References of "Dissertations and theses"
     in
Bookmark and Share    
Full Text
See detailNumerical Investigation of Multi-physics Turbulent Flows involving Weakly Diffusive Quantities
Sid, Samir ULiege

Doctoral thesis (2022)

Turbulence is a fluid flow regime observed in a large number of natural and engineering systems involving liquids or gases in motion. When the fluid viscosity is not able to overcome the flow inertia, a ... [more ▼]

Turbulence is a fluid flow regime observed in a large number of natural and engineering systems involving liquids or gases in motion. When the fluid viscosity is not able to overcome the flow inertia, a random chaotic motion characterized by a wide range of spatial and temporal scales takes place. In many cases, turbulent fluid flows interact with auxiliary physical phenomena such as chemical reactions or electromagnetic fields, to name but a few, resulting in substantial changes in their driving mechanisms. When the auxiliary physics relies on weakly diffusive quantities, the limited effect of diffusion at the Kolmogorov scale, where the smallest turbulent vortices dissipate, can potentially lead to the formation of even smaller structures. Batchelor's theory and subsequent investigations have proved that, in the case of passively advected quantities, structures smaller than the Kolmogorov scale develop in turbulent flow when the Schmidt number is sufficiently large. However, it remains unclear whether generic quantities behave similarly in multi-physics systems, where they play an active role. In the present work, direct numerical simulations of multi-physics systems involving weakly diffusive quantities are performed to study the interactions between the smallest scales of generic quantities and the mechanisms driving classical (uncoupled) turbulence. In particular, mixed convection flows and viscoelastic turbulence (dilute polymer solutions) are simulated in a periodic channel domain to determine the role of the small temperature or elastic scales in the turbulence production mechanism and their impact on the redistribution of turbulent kinetic energy over the different scales. The results of the present study show that the role of the smallest scales of generic quantities in the flow dynamics strongly depends on the system considered. In mixed convection flows, the majority of the multi-physics interactions occur at relatively large scales and decreasing the thermal diffusivity tends to limit the influence of thermal convection on the pressure-driven dynamics. In contrast, reducing polymer diffusion in viscoelastic turbulent flows allows thin polymer sheets characterized by very small scales to develop and contribute more actively to the polymer-turbulence interaction mechanism, resulting in a larger amount of turbulence produced in the flow. Although the two systems of interest are driven by multi-physics interactions of different nature, comparing their spectral distributions also reveals that turbulent vortices smaller than the Kolmogorov scale cannot form in any of the two flows and that the size of the smallest temperature/elastic scale is in rather good agreement with the one predicted by Batchelor's theory for the case of passively advected quantities. These findings suggest that simulating viscoelastic turbulence using RANS or LES approaches would most likely require tailored closure models that take into account the production of turbulence resulting from the interaction between the small elastic scales and the flow inertia. [less ▲]

Detailed reference viewed: 42 (13 ULiège)
Full Text
See detailEffets des amendements à base de biochar sur les paramètres agro-pédologiques dans une rotation coton-maïs à l’ouest du Burkina Faso
Cissé, Drissa ULiege

Doctoral thesis (2022)

Le défi de l’agriculture au Burkina Faso est de produire davantage pour répondre aux besoins alimentaires d’une population en constante augmentation sur des superficies de plus en plus réduites et des ... [more ▼]

Le défi de l’agriculture au Burkina Faso est de produire davantage pour répondre aux besoins alimentaires d’une population en constante augmentation sur des superficies de plus en plus réduites et des sols peu fertiles. Cette thèse s’intéresse à la durabilité des systèmes de production agricole par l’utilisation d’amendements à base de biochar pour relever le niveau de fertilité de sols à l’Ouest du Burkina Faso. L’objectif de l’étude est de renforcer les capacités de résilience des petits producteurs par la gestion durable de la fertilité des sols. La méthodologique a consisté à caractériser les sols des zones d’étude et à évaluer la performance agronomique des amendements à base de biochar selon la nature du sol à travers des tests agronomiques. Les résultats obtenus montrent que les sols étudiés à l’ouest du Burkina Faso sont issus de l’altération du granodiorite et du grès. Les teneurs en argile et en nutriments des lixisols et plinthosols développés sur matériau gréseux sont meilleures à celles des sols développés sur matériau granodioritique. La CEC de ces sols est contrôlée par l’argile. Toutefois les caractéristiques morphologiques varient peu mais les sols issus du matériau gréseux sont moyennement fertiles avec des aptitudes agronomiques modérées à nulle alors que les sols issus du matériau granodioritique ont une fertilité moyenne à basse avec des aptitudes agronomiques marginales à nulle. L’analyse de la qualité des amendements à base de biochar a montré que l’adjonction du biochar au cours du processus de compostage améliore significativement les teneurs en carbone total, azote total, phosphore total, potassium total et magnésium total du co-compost par rapport au compost de 30%, 48%, 68%, 72% et 64% respectivement. Les résultats des tests agronomiques sur plusieurs types de sol montrent que les meilleurs rendements en coton graine ont été obtenus sur le lixisol chromique avec le co-compost (1877 kg.ha-1) en 2018 et avec le biochar (2056 kg.ha-1) et en 2020. Le même sol a enregistré le meilleur rendement en maïs grain en 2019 avec le traitement co-compost (4140 kg.ha-1). Par ailleurs, les rendements coton graine et biomasse obtenus avec les amendements ont significativement élevés comparativement au compost sur tous les sols excepté le lixisol endoplinthique où l’essai a subi des dégâts d’animaux en milieu de campagne. Des tests agronomiques montrent que le co-compost appliqué à une dose de 2,5t.ha-1.an-1 en deux ans associé à 75% de la dose recommandée de NPK permet de maintenir le rendement des cultures au même niveau que le compost associé à 100% de la dose recommandée de NPK. Les rendements moyens en coton graine de 2018, sont respectivement de 1338 kg.ha-1 pour le co-compost associé à 75% de la dose recommandée de NPK, 1237 kg.ha-1 pour le co-compost associé à 100% de la dose recommandée de NPK et 1176 kg.ha-1 pour le compost associé à 100% de la dose recommandée de NPK. Les résultats de notre étude montrent que le matériau parental impact les caractéristiques physico-chimiques des sols mais ne contrôle pas l’aptitude agronomique. Le niveau de fertilité des sols est moyen sur le matériau gréseux et moyen à bas sur avec des aptitudes agronomiques modérées à nulle. La performance des amendements à base de biochar est la fois fonction du type de sol et de la durée de l’amendement dans le sol et l’utilisation du co-compost comme amendement du sol permet de réduire les apports en NPK de 25 % sans affecter les rendements des cultures. [less ▲]

Detailed reference viewed: 29 (3 ULiège)
Full Text
See detailStudy of the natural radioactivity background of the Douala University Campuses and surrounding by Nuclear Techniques: Validation by GEANT4 Monte Carlo simulations
Guembou Shouop, Cébastien Joel ULiege

Doctoral thesis (2022)

The present thesis focused on an ionizing radiation monitoring project of the soils of the University of Douala campuses (campus 1 and 2) and surrounding, the Littoral region of Cameroon. The purpose was ... [more ▼]

The present thesis focused on an ionizing radiation monitoring project of the soils of the University of Douala campuses (campus 1 and 2) and surrounding, the Littoral region of Cameroon. The purpose was to provide a baseline to document the conditions present at the time of sampling. The methodology used γ-ray spectrometry-based High Purity Germanium detector (HPGe), both Energy Dispersive X-Ray Fluorescence (EDXRF) and Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectrometry for sample’s elemental characterization, and the Monte Carlo simulation-based Geant4 toolkit for detector efficiency calibration. The Geant4 toolkit also provides the opportunity to optimize the detection systems using computer simulations and greatly reduces the need for expensive (radiation exposure to calibration sources) testing in the laboratory. The assessment of 238, 235U, 232Th, 137Cs, and 40K concentration was done by measuring soil and sand samples by γ spectrometry-based High Purity Germanium detectors (HPGe). Both laboratories of the National Radiation Protection Agency (NRPA) of Cameroon and the Atomic and Nuclear Spectroscopy, Archeometry Laboratory of the University of Liege were used for experiments. Geochemical characterization of soil samples, origin determination, and provenience were accessed by X-ray spectroscopy. By comparing the results of two detectors and the technics used according to the detector type, improvements on the γ spectrometry methodology were made. The relative uncertainty activity concentration was calculated for 226Ra, 232Th, and 40K. The average report between the GC0818-7600SL model and the BEGe-6530 model was the main outcome that suggested real attention that should be paid when selecting the radionuclide to be investigated on a specific type of detector. The BEGe detector was found to be more suitable for low γ energy emitters measurement, compared to the GC0818-7600SL model, found more efficient for high energy γ emitters. The potential radiological hazards parameters were assessed by calculating successively the following parameters from using those sands in the construction of dwellings and large buildings: Ra-dium Equivalent activity (Raeq), Outdoor absorbed γ dose rate (Dout), Annual Effective Dose rate (AED), Internal hazard (Hin) and external hazard (Hex) indexes, and 𝛼 and γ indexes for sand samples used as building materials. Results obtained show that Annual Effective Dose absorbed by in-habitants due to the use of the investigated sand as construction materials was found to be below 1.0 mSv y-1. Therefore, sand used as building materials from the investigated quarries appears to be radio-logically safe for building construction and for the environment (beaches, built houses, …) where people could safely spend time. Soil characterization using EDXRF in the present study provided an overview of the geological origin or provenience of the investigated area. As a result, the analyzed soil samples could be classified chemically as Fe-soil and are illustrative dregs from the Continental margin because of the high concentration of Fe in all the investigated samples. These data record the elemental composition and the natural radionuclide’s radioactivity levels of the studied area and could be set as reference database information in the region, in Cameroon as well as for the Gulf of Guinea’s data. Monte Carlo validation based on the GEANT4 toolkit has been used to validate the efficiency calibration of the system, and it has been noticed that the combination of γ-ray spectrometry, the development of related Monte Carlo methods, and the GEANT4 (GEometry ANd Tracking) toolkit developed for γ spectrometry simulation are compelling and useful for detector characterization nowadays. It can then be concluded that the Monte Carlo simulation gives more prominent adaptability, greater flexibility, gained time, precision, and accuracy when determining the detector response and efficiency in the routine of environmental radioactivity monitoring. [less ▲]

Detailed reference viewed: 47 (10 ULiège)
Full Text
See detailCharacterization of the river thermal regime in relation to its environment: a regional approach using in situ sensors in a temperate region (Wallonia, Belgium)
Georges, Blandine ULiege

Doctoral thesis (2022)

Due to climate change, the normal natural balance is being altered. In particular, the rise in temperature already observed is leading to numerous risks for humans and all other forms of life on Earth ... [more ▼]

Due to climate change, the normal natural balance is being altered. In particular, the rise in temperature already observed is leading to numerous risks for humans and all other forms of life on Earth. Climate change also disrupts the conditions of the aquatic ecosystem such as water temperature (WT). WT is a major factor influencing aquatic ecosystems. WT influences many physicochemical factors in streams (e.g., oxygen availability, organic matter, toxicity and decomposition rates) that impact the metabolism, growth, survival, and swimming endurance of aquatic organisms (fish species, algae, insects, …). Climate change is also expected to lead to more frequent unusually high WT. These extreme thermal events defined as temperatures that lie outside the seasonal norms (abnormal), have repercussions on biodiversity (modification of productivity, spatial distribution and the extinction of species subordinated to their environment) and river managers whose actions currently in place may become ineffective in the coming years. The understanding of thermal processes in rivers is therefore crucial for coping with climate change. In this context, the objective of this thesis is to characterize the thermal regime of rivers in relation to their environment and to focus on thermal extreme events. All the research has been conducted on the hydrographic network of the southern region of Belgium (Wallonia) covered by a hundred stations recorded WT at intervals of 10 minutes. First, data is needed to characterize thermal regime. Specifically, continuous WT network is essential for effective research unfolding through time in a global change context. The networks of stations dedicated to WT measurement are scarce. However, many countries have large spatial networks of water quality (water quality monitoring) or water level (flow monitoring) measurement whose probes are equipped to measure WT. Therefore, we investigated the use of WT data from a regional water level monitoring network which measure WT as ancillary data (chapter 2). A Bland–Altman analysis with WT collected through a European monitoring network (Water Framework Directive) and WT data from our regional water level network (140 stations) was made to test the reliability of the water level network for continuous WT monitoring. We found that the water level stations were reliable tools in recording continuous WT in the streams of the study area. The temperature difference between the two WT monitoring networks was −0.57°C on average but showed a strong linear correlation. Our positive results allowed us to use WT from water level stations in order to perform both state‐of‐the‐art visualization of thermal regimes and spatio‐temporal queries for specific ecological monitoring at high frequencies. Second, based on WT data validated in chapter 2, we highlighted and studied « extreme WT ». Although many studies focus on maximum WT, « extreme WT » are more relevant to be identified and modeled in a climate change context. « Extreme » or WT above normal characterizes unusual weather events influenced by global change. Extremes can be damaging (and even lethal) for aquatic ecosystem. Indeed, for many aquatic species the different phases of the reproduction cycle are controlled by seasonal change (temperature, photoperiod, …). This coordination ensures that the offspring are produced under optimal environmental conditions for their survival. Hence, abnormal WT change may have negative impacts on species with seasonal spawning patterns. In addition, an increasing number of extreme events is observed as the climate continues to change. In chapter 3, we made a generalized additive modeling (GAM) to highlight extreme WT. GAM is a time series statistical method which allows to extract within-year variations (seasonality) and long-term changes (trend). WT which deviated significantly from commonly observed WT (or normal) were therefore be identified. Then, the WT temporal dynamics around extremes were modeled using specific differential equations in order to better understand the phenomenon. Thirdly, managers need to know how to mitigate rising WT due to climate change. We hypothesized that (i) extreme thermal events highlighted in chapter 3 are influenced by a limited set of environmental factors and (ii) the role played by those factors varies spatially. Therefore, in chapter 4, we determined which environmental variables affected the most WT. Environmental variables are composed of land cover, topographical (channel slope, elevation, shade) and hydromorphological (channel sinuosity, water level, watershed area, baseflow index) factors which are the main influential variables identified in the literature as affecting WT. The role of environmental parameters was investigated at different spatial scales (buffer, riparian and watershed scales) to identify the spatial scales over which those environmental variables influenced WT. To test these hypothesis, stepwise multiple linear regressions (MLR) were made between model variables (day thermal sensitivity, night thermal sensitivity, and non-convective thermal flux) calculated in chapter 3 and environmental variables. Environmental variables were evaluated for the six spatial scales during summer extreme events highlighted in chapter 3. Results showed that shade, baseflow index (a proxy of the influence of groundwater), water level and watershed area were the most significant variables influencing thermal sensitivity. Our results show also that a larger management scale is not more effective in reducing thermal sensitivity to extreme events. Finally, the main findings of the thesis were summarized and we discussed some limitations of our results and the main practical implications. Particularly, we discussed three questions: « With what data can we characterize the thermal regime? », « When and where is it relevant to characterize the thermal regime? » and « How managers can act to mitigate WT increases? ». Future research perspectives were also provided. [less ▲]

Detailed reference viewed: 33 (8 ULiège)
Full Text
See detailAdvanced continuous flow strategies toward pharmaceutical ingredients
Kassin, Victor-Emmanuel ULiege

Doctoral thesis (2022)

Within the context of revisiting abandoned, forbidden or forgotten chemistry and in conjunction with emerging strategies, continuous flow technology dedicated to the manufacture of high value-added ... [more ▼]

Within the context of revisiting abandoned, forbidden or forgotten chemistry and in conjunction with emerging strategies, continuous flow technology dedicated to the manufacture of high value-added molecules constitutes a significant and timely research area. While batch chemistry made it from the dawn of preparative organic chemistry to nowadays lab environments alongside with its drawbacks and benefits, continuous flow technology holds the potential to redefine the current paradigm of chemical synthesis. By overcoming the well-known boundaries of conventional chemistry, flow technology helps addressing the many aspects of chemical hazard, intensification and overall environmental footprint. This PhD dissertation intends to demonstrate the assets of continuous flow chemistry for the expedient, safe, robust and scalable preparation of active pharmaceutical ingredients and analogs. [less ▲]

Detailed reference viewed: 45 (5 ULiège)
Full Text
See detailFinite-Element Modeling of Thin Wires Including Skin- and Proximity Effects
Velasco, Jonathan ULiege

Doctoral thesis (2022)

This thesis presents an accurate and inexpensive treatment of thin conducting wires in finite element (FE) models for the magnetic vector potential magneto- dynamics formulation in frequency domain. The ... [more ▼]

This thesis presents an accurate and inexpensive treatment of thin conducting wires in finite element (FE) models for the magnetic vector potential magneto- dynamics formulation in frequency domain. The idea of the proposed technique, called Semi-Analytical (SA) method, is three-fold. Real conductors are represented in the FE model by idealized thin wires with vanishing radius. The implied mod- elling error is then canceled by means of a field truncation based on the solution of a small auxiliary FE problem. Finally, analytical results are invoked to reconstruct the local field solution and to accurately evaluate the losses and impedances. The SA method is first demonstrated and then systematically compared against the results of a conventional fully discretized finite element model (FM) in case of a single conductor and of multiple parallel conductors. The method’s accuracy at a broad range of frequencies is studied, particularly emphasizing the impact of spacing between conductors. Lastly, the formulation is extended to include ex- citation sources (e.g., voltage, current) and analytical expressions accounting for frequency-dependent effects on the inductance and resistance of multi-turn coils. [less ▲]

Detailed reference viewed: 73 (21 ULiège)
Full Text
See detailStudy of Structure – Property – Function Relations of Hawthorn Pectin
Zhou, Mo ULiege

Doctoral thesis (2022)

Pectins are a family of native heteropolysaccharides ubiquitously presenting in the primary cell wall and the middle lamella of higher plants, which have been commercialized for wide applications in food ... [more ▼]

Pectins are a family of native heteropolysaccharides ubiquitously presenting in the primary cell wall and the middle lamella of higher plants, which have been commercialized for wide applications in food industry as gelling agent, emulsifier, stabilizer, and thickener. As a natural ingredient with both textural modification abilities and various health-benefit effects, the global market of pectin is expected to grow rapidly in the future, driven by the increasing demands for natural, clean label and functional ingredients. Currently commercial pectin products are mainly extracted from citrus and apple, which are difficult to adapt to the increasing and diversified demands for tailored applications of pectin in food, pharmaceutical, and hydrogel material industries. Finding new source of pectin with specific structure, property, and function is attracting both industry and academia. Hawthorn is a popular commercial fruit in China which is an important edible and medicinal source. Hawthorn fruits contain large amount of pectin resource which has been almost not exploited and utilized, due to the poor knowledge on the structure, property, and function of hawthorn pectin. The present thesis investigated in-depth on the structure characteristics of hawthorn pectin, and related them with the rheological property and function of inhibiting lipid digestion. The results showed that among natural pectins, hawthorn pectin is characterized by high degrees of methoxylation (DM), low molecular weight (MW), high proportion of homogalacturonan (HG) region, low proportion of rhamnogalacturonan (RG) region but with abundant side chains. These features of pectin structure are different among the hawthorn fruits which are mainly used for processing in different provinces of China, and significantly affected by heat processing and extraction temperature, thereby resulting in the different performances in rheological property and function of inhibiting lipid digestion. A dynamic alteration of pectin fractions involving solubilization and depolymerization occurred simultaneously during heat processing of hawthorn fruit. The solubilization mainly happened in chelator-soluble pectin (CSP) and Na2CO3-soluble pectin (NSP), inducing a shift from water-insoluble pectin to water-soluble pectin (WSP), meanwhile the depolymerization occurred in HG region of WSP, forming a large amount of pectic polysaccharide fragments with small MW. Long time heat processing at high temperature had negative effect on both rheological property and ability to inhibit lipid digestion of hawthorn pectin. The pectin (HP60) extracted from Hebei hawthorn at mild temperature (60 °C) presented a good rheological property and best inhibitory effect on lipid digestion. It can even can form gel-like structure by itself without the presence of sugar and calcium ion. The self-gelation property of HP60 owed to its unique structural and conformational characteristics including high DM, relatively lower MW, abundant side chains, an appropriate ratio of HG and RG-I regions and a balanced chain length between the main chain and side chains. Theoretically, the relation of structure–property–function of pectin is very complicated. Besides DM and MW, this thesis through systematic research into hawthorn pectin revealed that the other structural even conformational characteristics such as the abundance of RG-I region, the amount of side chains, and the length of main chain and side chains also affect pectin property and function. The property and function of pectin is a combined consequence of multiple effects of various structural even conformational features. This study provides novel knowledge and in-depth insight on understanding the structure–property–function relations of pectin. More importantly, this study described a typical structure of high methoxy pectin which can form gel without large amount of sugars as co-solute. It breaks the traditional knowledge on the gelling mechanism of high methoxy pectin. This typical structure of high methoxy pectin is worthy to be in-depth studied in the future. On the industrial relevance side, the results and finding of this thesis will facilitate the utilization and commercialization of hawthorn pectin. [less ▲]

Detailed reference viewed: 42 (11 ULiège)
Full Text
See detailAnalyse du cadre légal de la vaccination par le pharmacien d’officine à l’étranger et transposabilité au système belge
Delwaide, Anne-Lise ULiege

Master's dissertation (2022)

Introduction : En Belgique ainsi que dans de nombreux autres pays, deux problématiques liées à la vaccination coexistent en termes de santé publique. D’une part, il y a un déficit de couverture vaccinale ... [more ▼]

Introduction : En Belgique ainsi que dans de nombreux autres pays, deux problématiques liées à la vaccination coexistent en termes de santé publique. D’une part, il y a un déficit de couverture vaccinale pour plusieurs maladies pouvant être prévenues par la vaccination telles que la grippe, le pneumocoque, le papillomavirus humain et les doses de rappels chez l’adulte du vaccin antitétanique. D’autre part, il se produit chaque année, de façon saisonnière, une surcharge des systèmes de soins de santé dû à la vaccination anti grippale qui se réalise sur un cours laps de temps. En outre, il se rajoute dorénavant la pandémie de COVID-19 qui sature d’autant plus le système. Contrairement à la Belgique, de nombreux pays utilisent le pharmacien en tant que vaccinateur pour répondre à ces problématiques, en complémentarité avec les autres prestataires de soin de santé. L’objectif de ce travail sera donc de déterminer si cette prestation peut être implémentée dans le système de santé belge. Méthodologie : Nous avons recueilli des informations concernant le cadre légal relatif à la vaccination par le pharmacien d’officine à l’étranger. Pour réaliser cette recherche, nous avons questionné divers intervenants en France, en Suisse, au Canada, au Portugal, en Irlande et au Royaume-Uni et utilisé les sites des Ordres des pharmaciens ou des Associations s’y référant. Nous avons également utilisé les textes réglementaires propres à chaque pays. Pour la Belgique, nous avons interviewé plusieurs acteurs clés et analysé les textes réglementaires se référant à la profession de pharmacien. Résultats : Il s’avère que les pays qui ont instauré la vaccination par le pharmacien suivent les mêmes lignes directrices concernant les conditions à remplir pour pouvoir réaliser l’acte vaccinal. Ces conditions sont la réussite d’une formation à la vaccination, la mise en place d’un aménagement spécifique au sein de l’officine, l’obligation pour le pharmacien de déclarer son activité auprès des autorités compétentes, la détermination de procédures relatives à la réalisation de cet acte et la mise en place d’un système de traçabilité des vaccinations réalisées. Ces conditions ont été décrites et analysées en détails dans notre travail. Conclusion : Il s’est avéré, au terme de ce travail, que les exigences demandées aux pharmaciens à l’étranger pour réaliser l’acte vaccinal peuvent aisément s’appliquer au système de santé en Belgique. Toutefois, il est nécessaire pour ce faire de modifier la loi coordonnée du 10 mai 2015 relative à l'exercice des professions des soins de santé afin que la vaccination ne soit plus considérée comme un acte médical. Sur la base de ces exigences, nous proposons un potentiel cadre légal qui pourrait s’y appliquer. [less ▲]

Detailed reference viewed: 42 (6 ULiège)
Full Text
See detailAléas naturels, dégradation de l'environnement et vulnérabilité des populations littorales camerounaises
Mbevo Fendoung, Philippes ULiege

Doctoral thesis (2022)

De par le monde, les aléas naturels sont responsables de plusieurs dégâts tant matériels qu’humains. La manifestation de ces aléas sur le littoral camerounais est sans cesse croissante. À ceci s’ajoute la ... [more ▼]

De par le monde, les aléas naturels sont responsables de plusieurs dégâts tant matériels qu’humains. La manifestation de ces aléas sur le littoral camerounais est sans cesse croissante. À ceci s’ajoute la dégradation environnementale orchestrée par les agro-industries et l’urbanisation. Ce qui fait que cet espace géographique, du Nord au Sud, présente une forte vulnérabilité. Dans ce champ de recherche suffisamment vaste, ce travail insiste sur les inondations et l’érosion côtière, dans l’objectif d’analyser la vulnérabilité du littoral Camerounais aux aléas naturels et proposer des éléments à intégrer dans les stratégies locales d’adaptation. Pour y parvenir, une approche méthodologique holiste est adoptée. La cartographie de l’érosion côtière s’est appuyée sur le logiciel ArcGis/DSAS, à base des images satellites de types Landsat (30m), les photos aériennes Google earth et les images pléiade (0,5m). Celle des inondations est faite, avec l’approche hydro géomorphologique. Des zones de vulnérabilité sont identifiées sur une échelle de 5 (très faible, faible, modérée, élevée et très élevée) et spatialisées. La dégradation environnementale est mesurée sur l’ensemble du littoral camerounais à travers la classification supervisée des images Landsat (1986-2020). Les perceptions locales des changements est analysées grâce à la méthode paysagère SELP. Elle est appliquée sur les sites de Campo, Kribi et Apouh (SOCAPALM). La vulnérabilité quant à elle est analysée en prenant en compte les dimensions physiques, sociales et économiques. Les indices d’exposition, de sensibilité et de capacité d’adaptation sont déterminés à travers les enquêtes de terrain pour mieux expliquer la vulnérabilité. Un échantillon de 300 ménages est pris en compte dans cette étape, de façon aléatoire. Seulement 201 ménages ont répondu. Fort de cette démarche, un certain nombre de résultats est obtenu. L’érosion côtière affecte plus de 75% du linéaire côtier dans l’estuaire du Wouri, avec des taux de recul estimés à +- 3m à +-5m par endroit, entre 1975 et 2020. Les points chauds de régression sont entre autres Cap Cameroun, la flèche littorale autour de l’île de Manoka et la zone proche du PAD. Au niveau de Kribi, l’érosion est à sa phase initiale. Entre 1973 et 2020, le linéaire présente une certaine stabilité. Au total, +-72,32 % du trait est resté stable, +-1,3 % en accrétion et 26,33 % en érosion. Par ailleurs, les inondations sont récurrentes et affectent plus les localités riveraines de l’océan Atlantique (Malimba, Lobéthal, Manoka, Cap Cameroun, Idénau), mais encore plus la ville de Douala dont 70% de la superficie urbaine est bâtie sur des sites très vulnérables. Face à cet environnement à risque et où s’enchainent des aléas de plusieurs natures, il y a des populations vulnérables et des écosystèmes fragiles. Vu sous l’angle physique, le littoral camerounais présente une vulnérabilité remarquable. Plus de 80% des logements sont en matériaux précaires et essentiellement des campements de pécheurs. Au niveau social, l’accès à l’éducation reste faible, surtout pour le genre féminin. Il en est de même pour l’accès au soin de santé. Les maladies les plus dominantes sont le paludisme et la typhoïde. La perception de ces changements environnementaux est disproportionnée, ce qu’en témoignent les analyses SELP. Dans l’ensemble et fort des enquêtes de terrain, un indice de vulnérabilité moyenne de 2,63/5 est obtenu. L’indice d’exposition est de 3,58/5, celui de sensibilité est de 2,75/5 et celui des capacités d’adaptation est de 1,54/5. Pour s’adapter et garantir leur survie, les populations locales développent des stratégies telles que la construction sur pilotis, le renforcement de la résistance des maisons, la relocalisation… Malheureusement, les mesures étatiques de réponse semblent insuffisantes, voire inefficaces. Les structures dédiées à la gestion des risques semblent non opérationnelles (DPC, ONR…). Le cadre légal est riche mais reste latent. Au final Le littoral camerounais présente le visage d’un territoire subissant l’assaut répété des aléas naturels et dont certains sites sont aujourd’hui, complètement assiégés par ceux-ci. D’où la situation de vulnérabilité observée et analysée dans ce travail. Des efforts de gestion sont faits mais ont du mal à s’inscrire dans la durabilité. L’urgence de réévaluer et d’opérationnaliser les politiques publiques en faveurs de la gestion de l’environnement en général et des risques et catastrophes en particulière s’impose. Il faut également sensibiliser les populations et les autorités locales sur la nécessité de préserver la mangrove. [less ▲]

Detailed reference viewed: 29 (3 ULiège)
Full Text
See detailStudy of the behavior of Listeria monocytogenes in raw milk butter
El-Hajjaji, Soundous ULiege

Doctoral thesis (2022)

Detailed reference viewed: 25 (4 ULiège)
Full Text
See detailAnti-Obesity Activity of α-AI Enriched Extracts From White Common Bean and Its Application In 3D Printing Foods
Shi, Zhenxing ULiege

Doctoral thesis (2022)

SHI Zhenxing. (2022). Anti-Obesity Activity of α-AI Enriched Extracts From White Common Bean and Its Application In 3D Printing Foods (PhD Dissertation in English). Gembloux AgroBio Tech, University ... [more ▼]

SHI Zhenxing. (2022). Anti-Obesity Activity of α-AI Enriched Extracts From White Common Bean and Its Application In 3D Printing Foods (PhD Dissertation in English). Gembloux AgroBio Tech, University, Gembloux Belgium, 151 pages, 11 tables, 22 figures. Recent studies have shown that consumption of common bean (Phaseolus Vulgaris L.) foods contributes to the prevention and treatment of obesity, which mainly based on the starch blocker role of α-amylase inhibitor (α-AI) in common bean seeds. In this study, (1) the in vitro and in vivo inhibitory effects of α-amylase inhibitor enriched extracts (α-AIE) from white common bean on fat accumulation was studied, respectively; (2) the regulatory effects of α-AIE on the gut microbiota composition in high-fat diet-induced obese rats was investigated; (3) the 3D printing performance of common bean protein extracts (CBPE) which possess α-AI activity was evaluated. Firstly, α-AIE was isolated from white common bean seeds (Cultivar Longquanjiuli) and its α-AI activity was determined to be 1027.1±154.2 (U·mg-1 protein). The effects of α-AIE on 3T3-L1 adipocytes differentiation were evaluated. Results of Oil Red O staining showed that a-AIE inhibited 3T3-L1 adipocytes differentiation. The quantitative results revealed that low dose (2 mg/mL) and high dose (4 mg/mL) of α-AIE reduced the lipid content in the mature adipocytes to 90.20% and 68.28%, respectively. Additionally, high dose of α-AIE showed significant suppression effects on the mRNA expression level and the protein expression level of (1) peroxisome proliferator-activated receptor γ (PPARγ), (2) CCAAT-enhancer-binding protein α (C/EBPα), and (3) fatty acid binding protein (ap2). Secondly, the anti-obesity effect and gut microbiota modulation properties of α-AIE were verified in high-fat diet-induced obese rats. Intake of α-AIE significantly reduced the body weight, intra-abdominal fat accumulation and improved the serum lipid levels (p<0.05, R=0.94, 0.92 and 0.95), suggesting its inhibitory effects on fat accumulation in vivo. In addition, rats fed the α-AIE diet exhibited higher total short-chain fatty-acid (SCFA) concentrations (p<0.05, R=0.91) in their colonic contents. β-Diversity analysis, principal components analysis and a Venn diagram showed that α-AIE administration changed the gut microbiota composition. At the phylum level, the relative abundances of Firmicutes and Proteobacteria decreased and the relative abundances of Bacteroidetes and Akkermansia increased. Eighty-nine of operational taxonomic units (OTUs) significantly responding to high-fat diet and 30 OTUs significantly responding to α-AIE were identified. The OTUs enriched by α-AIE were mainly assigned to putative SCFA-producing bacteria, including Bacteriodes, Butyricoccus, Blautia and Eubacterium. Twenty-two of OTUs were found to be significantly correlated with obesity indexes. Finally, CBPE powders with the α-AI activity of 961.30±29.43 (U·g-1 protein) were further smashed to different superfine grinds for 0, 6, 12 and 24 minutes. Then, the CBPE mixtures of Formula A (CBPE: 40%, alginate: 0.5% and gelatin: 6.0%) and Formula B (CBPE: 12%, xanthan: 0.05%, and agar: 3.5%) were confirmed with the addition of suitable additives, which can be applied in two types of printers (syringe extruder 3D printer and L3D kit 3D printer). Superfine grinding significantly (p<0.05, R=0.99) decreased the particle size of CBPE, and resulted in a reduction in the printability of the food-ink systems mainly through increasing (p<0.05, R=0.99) the adhesiveness of materials for the syringe-based 3D food printer, and increasing the swell powder (p<0.05, R=0.98) of materials for the gear-based 3D food printer. The decrease in the stability of printed products by the syringe-based 3D food printer was mainly due to the reduced water binding capacity (p<0.05, R=0.91) by superfine grinding. Besides, the syringe-based extrusion process was demonstrated to have no obvious effect (p>0.05, R=0.37) on the α-AI activity of CBPE. The 3D products of the L3D kit 3D printer with Formula B lost the α-AI activity but had very high stability. All these results indicate that several dose of α-AIE from white common bean can inhibit the fat accumulation both in vitro and in vivo; Intake of α-AIE attenuated obesity and modulated gut microbiota composition in high-fat diet-induced obese rats. The addition of hydrophilic colloid improves the 3D printing performance of CBPE, but ultra-fine grinding degrades it. The results of our study should improve our knowledge of common bean α-IEA and its inhibitory effects on obesity as well as its valorisation and application in food additive manufacturing. [less ▲]

Full Text
See detailSilica-based solid electrolyte for Li-ion microbatteries
Hartmann, Korina ULiege

Doctoral thesis (2022)

The PhD thesis was embedded in the Energy for Smart Objects (EnSO) project, which is part of the Electronic Components and Systems for European Leadership (ECSEL) Joint Undertaking in collaboration with ... [more ▼]

The PhD thesis was embedded in the Energy for Smart Objects (EnSO) project, which is part of the Electronic Components and Systems for European Leadership (ECSEL) Joint Undertaking in collaboration with the European Union’s H2020 Framework Program (H2020/2014-2020) and National Authorities, with the aim to develop Autonomous Micro Energy Sources (AMES) for smart objects. In the framework of the EnSO project, the goal of the thesis was to develop a solid electrolyte for all-solid Li-metal microbatteries as energy storage device in AMES. Lithium metal is the anode material of choice because of its very high theoretical specific capacity of 3861 mAh/g, which is one of the important requirements for miniaturized batteries. However, inhomogeneous lithium depositions known as dendrites, which reduce the life time and can connect both electrodes and create a short circuit, are often observed when using Li-metal as anode. The aim is therefore to develop a solid electrolyte, which presents a high ionic conductivity for the Li ion transport and a high mechanical stability to hinder dendritic growth. Electrolyte solutions based on ionic liquids (ILs) with dissolved lithium salt can be confined into inorganic porous networks forming so called ionogels (IGs), which are investigated as quasi-solid electrolyte materials. In a first step, the synthesis in a one-pot sol-gel process for silica-based ionogels is developed and in a second step tested as quasi-solid electrolyte in Li/LiCoO2 systems. IGs were obtained by a sol-gel reaction between TMOS as silica precursor and TFA as catalyst in PYR13-FSI (IL) and LiTFSI (Li+ source). It was possible to synthesize transparent IG monoliths with gelation times of 2-3 h, which is a suitable time for the IG film preparation on the LCO cathodes. Four IGs with different compositions were prepared and characterized. Two types of silica matrices built of mostly threefold-condensed Si centers could be distinguished: a densely packed structure and an open-porous structure, the latter one corresponding to IG B with the molar ratios IL/TMOS=3, TFA/TMOS=0.3, H2O/TMOS=2.3. The ionic conductivity of the IGs could be linked to the silica matrix structure. Only the IG with the open-pore structure (IG B) has a good ionic conductivity (10−4 S/cm). Equally, the examination of the four IGs as thin film electrolytes in LCO/Li batteries show promising results for batteries containing IG B. However, the capacity lies under the theoretical value (89 mAh/g instead of 136 mAh/g) due to high cell resistance. Therefore, the ionic conductivity of IG B was improved by changing the synthesis process while keeping the composition unaltered. The new IG B∗ has a very good ionic conductivity (10−3 S/cm) but a poor mechanical stability due to a matrix structure of loosely connected silica particles. IG B∗ was not able to hinder dendritic growth. Thus, the PVDF-HFP polymer (20 wt.%) was added to B∗ (B∗-p), which enhanced the mechanical stability and the cyclability of the Li-ion batteries with B∗-p as electrolyte layer. No indication of dendrites was visible in the charge/discharge curve for minimum 30 cycles at C/5. The capacities are low (≤ 80 mAh/g) due to the decreased liquid (IL) to solid (SiO2 + PVDF-HFP) ratio, which results in a lower lithium ion mobility. In order to increase the battery capacity, the silica amount in the IG formulation was reduced, the LiTFSI lithium salt concentration was increased, and the Li+ source was modified by taking IL-based electrolyte solution with different concentrations of LiFSI. Indeed, the capacity increases with decreasing silica amount due to improved ion mobility. The change of the lithium concentration from 1M to 3M and 5M enhanced the capacity. A battery with the combination of the reduced silica amount (0.5 TMOS) and 5M electrolyte solution has a good capacity (> 100 mAh/g) for at least 10 cycles at C/5. The lithium salt LiFSI has a smaller anion than LiTFSI and thus, it can further improve the ion mobility in the IG electrolyte film. All IGs containing LiFSI have a higher ionic conductivity than the corresponding gels with LiTFSI. Overall the battery performance and reproducibility could be greatly improved. Batteries containing a solid electrolyte with 20 wt.% PVDF-HFP and the reduced TMOS amount with a 3M LiFSI solution are able to cycle without the appearance of dendrites for 13 cycles at C/5 followed by 12 cycles at C/2 with a rather good coulombic efficiency around 95%. However, the capacity remains under the theoretical maximum. [less ▲]

Detailed reference viewed: 58 (1 ULiège)
See detailIntroducing biological neuronal dynamics and neuromodulation in artificial neural networks.
Vecoven, Nicolas ULiege

Doctoral thesis (2022)

The present thesis takes a step towards enriching artificial neural networks with bio-inspired mechanisms. To this end, high-level abstractions of important biological rules, modelled using control theory ... [more ▼]

The present thesis takes a step towards enriching artificial neural networks with bio-inspired mechanisms. To this end, high-level abstractions of important biological rules, modelled using control theory, will be introduced and linked to artificial networks. In particular, it will be discussed that introducing neuronal bistability and neuromodulation into artificial neural networks provides different benefits. As a first step, Part 1 will first introduce necessary machine learning background. Part 2 of this thesis will focus on the ability of recurrent neural networks to learn long-term dependencies, something which usually proves difficult. Bistable recurrent cells will be introduced as a way to help towards solving such issues. Furthermore, supported by the results obtained with those cells, a more generic method to promote multistability with usual recurrent cells is proposed. This part highlights the importance of dynamics in recurrent neural networks and in particular, right after initialisation, for easily learning long-term dependencies. Part 3 of this thesis is dedicated to introducing neuromodulation in artificial neural network. This important biological mechanism is often associated to the robust control of continuous behaviours, allowing biological systems to adapt very quickly to changing context, something which remains very difficult for usual artificial agents. As such, a neuromodulated architecture, specifically designed for its adaptive capabilities (i.e. robustness towards changing environment or context), is proposed. It will be shown to exhibit much more stable performance and to converge towards better policies than classical recurrent networks. Furthermore, this part discusses that these architectures are also implicitly able to learn a continuous representation of the different contexts in which they evolve. Finally, some other very recently proposed architectures and their benefits will be briefly mentioned as well. As a last note, it is important to mention that Part 2 and Part 3 of this thesis could potentially be linked. As such, the last part of this thesis will be dedicated to provide ideas for future works, specifically aimed at closing the gap between Part 2 and Part 3. [less ▲]

Detailed reference viewed: 60 (9 ULiège)
Full Text
See detailARCHITECTURE ET REGIONALISME AU CONGO : LA CONTRIBUTION DES TRADITIONS LOCALES DANS LES HERITAGES MODERNISTES A KINSHASA, 5 Études de cas
Tshiunza Kabeya, Alexis ULiege

Doctoral thesis (2022)

The modernism that characterizes African cities is described by some as European or foreign. However, many architects who had worked in Congo hoped to make an architecture that would become African ... [more ▼]

The modernism that characterizes African cities is described by some as European or foreign. However, many architects who had worked in Congo hoped to make an architecture that would become African. European styles had not suited them more than what was called African architecture at that time. They found « huts » inappropriate for cities, and did not want neither to make a decontextualized architecture just to reflect the grandeur of the Metropolis. A new architecture presented itself as a way out. Since it was impossible to invent ex-nihilo, to take neither Europe nor Africa, their architecture would be de facto a mixture. Adaptation to the environment has become their main objective and this legitimate concern in any architecture has allowed a great receptivity. European modernism has thus mingled with tropical architecture as a set of traditional solutions for building in the tropics, with sculptural and pictorial forms depending on the case. My research attempts to capitalize the responses that have been provided by 5 architects to the need for urban architecture in Congo by noting the local inputs and the regional character of their buildings. It would like to question the view of the architecture made by foreigners, often linked to colonization and the phenomenon of architectural importation that is observed among the former colonized. It proceeds through case studies on buildings mainly built by Belgian architects in Congo before the training and achievements of Congolese architects. Based mainly on the statements of these architects, the analysis of their works in comparison with a traditional or local architecture or practice and the writings on regionalism, it attempts to demonstrate that a certain effort has been made by each of the five architects to produce a worthy architecture in Congo. The targeted architects have distinguished themselves from European modernism and international style without yet passing the vernacular as in universal exhibitions or postmodernism. They have opened a third way, hybrid, between the traditional and the modern, between the local and the international, architecture made of a syncretism of ideas, which deserves attention in the current context of the rise of a globalizing culture. My research assumes that these architects, in doing so, would have facilitated the appropriation of their buildings, which can serve as examples in the teaching of the architectural project. [less ▲]

Detailed reference viewed: 32 (2 ULiège)
Full Text
See detailGenetic structure and migration of Sitobion miscanthi populations in China
Sun, Jingxuan ULiege

Doctoral thesis (2021)

Sitobion miscanthi (Takahashi), a wheat aphid, is an economically damaging aphid pest and the dominant species in China. Migration and diffusion are not only important manifestations of population ... [more ▼]

Sitobion miscanthi (Takahashi), a wheat aphid, is an economically damaging aphid pest and the dominant species in China. Migration and diffusion are not only important manifestations of population dynamics, but also important ecological countermeasures for aphids to adapt to the environment. Migration, as the main physiological behavior characteristic of aphids, is the main reason for the difficulty in monitoring and forecasting. Temperature, wind and geographic location are the main abiotic factors for the migration of aphids. In this thesis, indoor and outdoor experiments were combined associated to methods of physiology and population genetics. Firstly, the physiological and reproductive parameters of different geographical populations of S. miscanthi at different temperatures and the life history traits of different populations during the growth and development period were investigated and analyzed. There was no significant difference in reproductive capacity within populations from northern China. In addition, latitude was positively correlated with aphids’ longevity. Secondly, eighteen geographical populations from China were studied by using one mitochondrial gene COI, one nuclear gene (EF-1α) and two endosymbiotic Buchnera genes (gnd and trpA). Two main natural migration pathways of S. miscanthi in China were observed: one was from Yunnan to the Sichuan Basin and another from Wuhan, Xinyang and Jiaodong Peninsula areas to the northwest. We inferred that these aphids appear first in the southwest and south regions and spread to the north with the help of the southeast and southwest monsoons, which occur in spring and summer. In autumn, aphids spread southward with the northeast and northwest monsoons. Finally, to clarify geographical structure of S. miscanthi in China and the factors affecting its distribution, we selected aphid samples from six geographic locations in China and analyzed the evolution history of genetic differentiation. Our 6 geographical populations of S. miscanthi were divided into three groups, Yinchuan, Suzhou, and other populations. Genetic structure analysis based on the mitochondrial (COI) and the symbiotic genes (gnd and trpA) were similar indicating that the symbiotic genes could act as potential molecular markers in studying the genetic structure and diversity of aphid populations. Difference in annual average temperature may be the reason for diversity genetic structure of S. miscanthi providing theoretical evidence of the aphid migration. It was speculated that S. miscanthi has seasonal migration patterns in wheat regions to allow prediction of potential aphids outbreaks in China. [less ▲]

Detailed reference viewed: 44 (9 ULiège)
Full Text
See detailStrategic outline and sizing of district heating networks using a geographic information system
Resimont, Thibaut ULiege

Doctoral thesis (2021)

The implementation of district heating networks into cities is a main topic in European Union policy plannings looking for sustainable solutions to reduce CO2 emissions and improve global energy ... [more ▼]

The implementation of district heating networks into cities is a main topic in European Union policy plannings looking for sustainable solutions to reduce CO2 emissions and improve global energy efficiency of heating systems. Compared to decentralized heating production units, district heating networks provide higher energy efficiencies due to larger units’ sizes. However, their development into cities is generally limited by high initial investment costs and a long return on investment period. Therefore, policymakers and investors are reserved about new district heating networks projects because of the risks associated with the profitability of the project. The development of optimization methods intended to draft efficient systems using heating consumption profiles into a prescribed geographic area are useful in this purpose. A Multi-Period Mixed Integer Linear Programming (MILP) model for the optimal outline and design of a district heating network based on a Geographic Information System (GIS) is described in this thesis. The optimal outline aims to determine the location of the heating sources and the pipes into the network while the optimal design aims to size the pipes and the heating sources. This model can be used as a decision tool based on the maximization of the net cash flow (NCF) generated by the system from user-defined economic and physical parameters. This methodology aims to be applicable for a large range of problem sizes from small-scale to large-scale case studies while guarantying numerical robustness. This thesis provides new insights for the optimization of heating network systems: 1. A global review of the district heating network sector regarding the advantages, the technical breakthroughs and the economic features of these heating networks. Existing optimization models for heating networks are compared to identify their main attributes and to highlight the novelty and the benefits of this work compared to the existing ones. 2. Implementation of a new decision tool based on a methodology enabling to design any new heating network from scratch based on a geographic information system and user-defined economic and urbanistic parameters. 3. Applications of the methodology to small-scale and large-scale case studies to show the replicability of the decision tool to a large range of heating networks. 4. Optimized heating networks from the decision tool are modelled in a dynamic way to illustrate the limits of the decision tool and its lack of accuracy regarding the physics of the system. [less ▲]

Detailed reference viewed: 87 (18 ULiège)
Full Text
See detailWaste conversion for organic fertilizer and fungal production to promote crop plants and control pests
Liu, Xue ULiege

Doctoral thesis (2021)

A set of bottom-up interactions can be observed between soil, plant and pest. In rural areas, the discharge of livestock excrement is the main cause of water environmental pollution but with potential ... [more ▼]

A set of bottom-up interactions can be observed between soil, plant and pest. In rural areas, the discharge of livestock excrement is the main cause of water environmental pollution but with potential transformation into organic fertilizer using earthworms or black soldier flies. The use of such organic fertilizer alone or in combination with some fungi can affect pest growth and reproduction. The application of fungi also affected the growth and reproduction of pea aphid and fall armyworm. Firstly, dairy cattle farming produce large amounts of wastewater and it causes environmental pollution. Here, an improved vermicomposting system was applied to dairy farm wastewater with different combinations of organic substrates such as cow manure and rice straw in rural solid waste. Earthworm growth in vermicomposting were positively correlated with the C/N ratio, organic matter content and pH. Percentages of minerals increased in vermicomposting while organic matter content, C/N ratio, and cellulose declined as a function of the vermicomposting period. Final vermicompost was better for the absorption of plants. Continuous wastewater addition improved the effective transformation of organic waste to allow valorizing a broad range of organic residues, and avoid the risk of environmental pollution in dairy cattle farming. Secondly, multi-function fungi were used to promote plant growth. Inoculation with Phosphate-solubilizing microorganisms not only improved the growth of rape, but also increased phosphorus availability. We also obtained a novel gene from Penicillium oxalicum I1 whose overexpression in Escherichia coli increased the secretion of acetic acid helping to understand what was the function of the gene isolated from P. oxalicum as well as that of its homologs found in several other species of the Penicillium genus. Finally, fungi and compost were used to control pest included fall armyworm and pea aphid. Pest developmental durations were longer while reproductive ability was lower. Population dynamics of pests differed among the organic fertilizer treatments with vermi- or entomo-composts. Also, both entomopathogenic fungi and organic fertilizers effectively control aphids. Bioassays with Aspergillus flavus and A. niger allowed to control aphids To conclude, organic fertilizers and fungus synergistically reduced pest fertility and increased the death rate. To the best of our knowledge, this is the first report on the combined use of compost and multifunctional fungi to promote crop plants and synchronally control different pests such as aphid and moth. [less ▲]

Detailed reference viewed: 57 (7 ULiège)
Full Text
See detailHow to develop agriculture and protect the environment around protected areas: A case analysis of Xuan Thuy National Park, Vietnam
Nguyen Thi Trang Nhung, ULiege

Doctoral thesis (2021)

Agricultural development is still central to economic activity and employment in Vietnam. The developments in modern agriculture have led to a host of environmental concerns because it impinges on natural ... [more ▼]

Agricultural development is still central to economic activity and employment in Vietnam. The developments in modern agriculture have led to a host of environmental concerns because it impinges on natural resources and heavily relies on synthetic fertilizers, pesticides and other chemicals. Agricultural developments include various influences on biodiversity and ecosystem functioning and services such as destruction of wildlife habitat, organic and nutrient enrichment, pollution risks, etc. The research throws light on an area not always foregrounded in the discussion of agricultural development surrounding protected areas in Vietnam. It raises an important question about how can manage agricultural production of protected area buffer zones to achieve economic viability and ensure ecological sustainability. This research has sought to analyze the agricultural development of local people and provide some perspectives on sustainable development toward agroecology nearby protected sites which are significant for Vietnam. The structure and emphasis of this research have been shaped mainly by the material gathered through the interviews. Through the application of the systemic approach of agroecology (objectives-practices-outputs), this research reviews the current situation of agricultural development surrounding Xuan Thuy National Park, the first Ramsar site in Southeast Asia. In the protected area buffer zone, there is an existence of diverse farming systems (mono and poly-culture) but there is a dearth of ecological-based knowledge and practices of farm households. One indication that there have not different cultivation guidance and management for farmers in the communal buffer zone as compared with outer communes. Agricultural advisory services from the local government have been disseminated similarly in the whole district including the protected area buffer zone. Whole-farm performances gained with different levels of sustainability. From socio-economic perspectives, farm households achieve some profitability but less efficiency. From ecological perspectives, there are many issues related to environmental pollution including the spontaneous drainage of farm effluents, inordinate application of pest and disease control, unwise utilization of synthetic fertilizers, wide use of antibiotics, and water conflicting between group users. Through RAAIS (Rapid Appraisal of Agricultural Information System) analysis, this research identifies a vast range of elements that constitute constraints and underlying causes that hinder sustainable agricultural development and the application of ecological-based management practices in the protected area buffer zone. The top three clusters of constraints to achieving the development are mismanagement practices at the farm-scale, economic issues and environmental pollution. The analysis is undoubtedly brought about improvements in understanding the challenges and particular problems for agricultural developments around the protected area. Then the research focuses on the analysis of interlinked causes of the constraints. The first cause relates to the poor policy development associated with low enforcement of agroecologically-based methods for the agriculture sector nearby protected areas. Meanwhile, literature and policy documents show that Vietnam has numerous laws, policies and regulations for sustainable agriculture and eco-friendly cultivation, they have not been effectively transferred into practices at this zone. There is no restriction upon the unwise use of agrochemicals such as chemical pesticides and fertilizers around the sensitive area. At the same time, there is a lack of economic incentives for farmers who conserve nature near the protected area. Authorities at district and commune levels manage agriculture toward intensification but deficient ecological knowledge. Xuan Thuy National Park management board has very little authorization in monitoring improper practices of peripheral communities even though the park has technicians working on the issues related to environmental protection and conservation. Farmers have little interaction with the park for agricultural production. Furthermore, the enforcement of environmental standards in farming activities is limited despite the existence of environmental regulations and laws. The weak enforcement attributes by the dearth of facilities, resource-conserving equipment, laboratories, and staff from district to communes. In other words, environmental standards are given too much emphasis, while they have not transferred into practice and materialized in this site. The second emergent cause call for a reorientation is the agricultural advisory service system due to its low performance. Packages of technical advisory and problem-solving skillsets have not yet satisfied various needs of farmers or improved the economic and environmental outcomes of diverse production systems. Advisory providers have little role in assisting farmers to confront regional issues including negative impacts from pesticide contaminants and pond effluents, a disease outbreak in production, drastic weather, water conflicting between groups of farmer users, etc. Another critical interlinked constraint is related to the gap between the objectives of farmers and the park authority. Primary, farmers have the top priority for profits and they want to satisfy their own needs rather than feeling responsible for long-term maintenance. This clearly expresses the improper farming methods in the land-use systems and thus partly leads to the undesirable environmental performance in surveyed farms. While the conservative authorities expect both conservation and development, but in most cases economic factors shaped the decision-making of provincial government and lower agencies. From the preservation perspective, there have not clear indicators or measures of environmental sustainability for agriculture. Lastly, the findings of the research point out that farmers’ knowledge of ecological agriculture is deficient, and these have an impact on the limited adoption of environmentally friendly production methods. Several implications are arising from this research to reflect on what needs to be put in place to ensure the form of agriculture nearby sensitive sites. These include ways of the policy-making process and stakeholder engagement as well as fostering of local knowledge and capacities and sustainable management practices in the response of agricultural development and pollution mitigation. The changes require helps to regulate agriculture toward the preservation of local ecosystems. [less ▲]

Detailed reference viewed: 70 (8 ULiège)
Full Text
See detailFluorescent immunochromatographic assays (FICA) for quantitative detection of the foot-and-mouth disease virus serotype O antibodies
Hou, Fengping ULiege

Doctoral thesis (2021)

Foot-and-mouth disease (FMD) is a transboundary animal disease, and a disease of great economic significance in the animal husbandry industry. The prevention and control of such epidemic diseases is ... [more ▼]

Foot-and-mouth disease (FMD) is a transboundary animal disease, and a disease of great economic significance in the animal husbandry industry. The prevention and control of such epidemic diseases is particularly important. Effective diagnosis is indispensable to accomplish the mission. The common diagnostic methods are based on live virus or inactivated virus, which may cause leakage of virus easily. Some other methods are also time-consuming, labor-consuming or need sophisticated instruments. Considering the biosafety and practicality, the aim of this thesis is to develop simple quantitative real-time diagnostic assay for FMD with high sensitivity, specificity, and stability. Here, the fluorescent immunochromatographic assays (FICAs) were selected, owing to their simple, rapid, convenient, and safe performance. Rare earth fluorescent nanoparticles exhibit several unique fluorescent properties which make them suitable candidates for detecting biomolecules. Virus-like-particles (VLPs) are capsid proteins of virions, and they are assembled from structural proteins; they are noninfectious, owing to lack of genetic materials. The activated rare earth nanoparticles are integrated with conventional immunochromatography to quantitatively detect foot-and-mouth disease virus (FMDV) antibodies. First, noninfectious FMDV VLPs are utilized as capture antigen, and fluorescent europium microparticles (EuMSs) are applied as fluorescent labels. The labeled staphylococcal protein-A (SPA) are referred to as fluorescent sensors. The fluorescence signal intensity at test line and control line is associated with the concentration of the target antibody. The EuMSs-based assay showed 30-fold more sensitive through observation in five minutes and 68-fold more sensitive through portable equipment than colloidal gold assay. Next, to reduce the cost of the fluorescent nanoparticles and enhance the stability of the assembled strips, we prepared upconversion nanoparticles (UCNPs). Rare earth salts reacted under argon atmosphere according to the solvent thermal method, and then they are modified with citric acid using a ligand exchange method. The carboxyl-modified UCNPs were coupled with protein G to form the UCNPs sensor. The UCNPs-based strips showed higher stability at 4 ℃ for about one year. These assays have been evaluated with real serum samples without cross-interference. Therefore, such assays have great prospects for rapid, sensitive, and quantitative determination of foot-and-mouth disease virus serotype O (O-FMDV) antibodies. [less ▲]

Detailed reference viewed: 43 (9 ULiège)
Full Text
See detailPatterns of plant species invasion along urban-to-rural gradients
Géron, Charly ULiege

Doctoral thesis (2021)

The highest rates of introduction of alien species in Europe have been recorded in the last 25 years, and alien plant species are mainly brought in through horticulture, agriculture or contamination of ... [more ▼]

The highest rates of introduction of alien species in Europe have been recorded in the last 25 years, and alien plant species are mainly brought in through horticulture, agriculture or contamination of commercial goods. Only a small portion of the alien plant species pool can establish and develop in the introduced range. These low success rates are notably due to the presence of developmental and reproduction barriers. These barriers can be significantly weakened with climate change or disturbances from anthropogenic activities, however, increasing the risks of plant invasion. Alien plant species represent opportunities to study range expansions and plant response to new environmental conditions, especially when studied along environmental gradients. Urban-to-rural gradients came into view only recently for this purpose, despite their high variation in climatic conditions and anthropogenic influences at all spatial scales. In western Europe, urban-to-rural gradients exhibit temperature variations at scales ranging from kilometers to meters, due to the urban heat island effects (UHI) and microclimatic effects of urbanization. Moreover, due to the presence of anthropogenic surfaces and materials, western European cities have a lower relative humidity and urban soils are drier than rural ones. Cities represent communication nodes, are subject to anthropogenic disturbances and display a variety of growing conditions; therefore, a high density and diversity of alien plant species are present in urban areas. However, several aspects of alien plant species invasion along urban-to-rural gradients are still not fully understood. The hypothesis that alien plant species from warmer native ranges establish preferentially in urban areas has been formulated, but has never been formally tested. The phenotypic response of alien plant species along the urbanization gradient has been investigated mainly at the interspecific level and at rather coarse temporal and spatial scales, with often inconclusive results. Finally, the study of the evolutionary processes of alien plant species in relation to urbanization is still in its infancy. In this thesis, I study the relationships between alien plant species invasion and urbanization from the regional scale to the level of the plant. Focusing on western Europe, I investigate inter and intra-species variability using various species at different stages of invasion. Additionally, I integrate temporal and spatial scales in order to better highlight distribution, phenotypic response and evolution of alien plant species in relation to urbanization. Research questions are answered using a wide range of methods: from species distribution modelling over in-situ measurements of leaf and developmental traits to experimental reciprocal common gardens in-situ and in controlled conditions. I found that all alien plant species, regardless of their native climatic conditions, shared a comparable intraspecific phenotypic response to summer conditions along urban-to-rural gradients. The phenotypic response of alien plant species was only related to variables depicting the urbanization at the plant scale, and not by those at a coarser resolution. While alien plant species development was constrained by urban conditions, these restrictions seemed to be mitigated by the protection of shielded environments in which they experienced less light, heat and drought stress. The protection by shielded environments did not depend on whether the skyline consisted of buildings or vegetation, nor did it depend on climatic conditions during the growing season or on the location of these shielded areas along the urbanization gradient. Furthermore, I unveiled a complex interplay of plasticity, environmental maternal effects and local adaptation as sources of the phenotypic response of alien plant species. A critical role of seed mass and related environmental maternal effects was particularly apparent in urban conditions, which could represent strategies to persist in heterogeneous city environments. Finally, I found a high importance of native climatic conditions for the distribution of alien plant species along urbanization gradients at coarse spatial resolutions. While alien plant species, regardless of their climate of origin, were highly present in the central part of the urbanization gradient corresponding to detached houses with garden, their distribution patterns diverged towards the urban and rural ends of the gradient. Alien plant species from warmer or drier native climates were more present in urban areas, whereas species from cool and wet native climatic conditions had expanded more in the rural zones. The results of this PhD indicate that alien plant species distribute differently along the urban-to-rural gradient in oceanic Europe with species from warmer or drier native climates being more present in urban environments while species from cooler or wetter native climates are more present towards rural areas. The contrasted distribution of alien plant species according to their native climatic conditions was not related to their phenotypic response to summer conditions. Rather, the phenotypic response of alien plant species along urbanization gradients was similar, despite their different climatic affinities and depended on conditions at the local scale. This stresses the necessity to account for very local parameters when studying urbanization effects on alien plant species and the need to have access to fine resolution data of environmental conditions such as temperature. The high importance of seed variables and related environmental maternal effects for alien plant species phenotypic response suggests that the study of seedlings of alien plant species in relation to urbanization might unveil processes regarding their contrasted distribution along urban-to-rural gradients. Cities host new combinations of native and alien plant species which are subject to rapid and drastic changes. Better understanding the response of the urban flora to urbanization is crucial, especially in the ongoing era of globalization which sees the homogenization of biotas and because urban areas are where the majority of the world's human population live. [less ▲]

Detailed reference viewed: 33 (8 ULiège)
Full Text
See detailDE « BANCOVILLE » A LA CONSTRUCTION POSTMATERIALISTE : ÉTUDE SOCIO-ANTHROPOLOGIQUE DES CONDITIONS DE POPULARISATION DE LA BRIQUE EN TERRE COMPRIMEE (BTC) A OUAGADOUGOU (BURKINA FASO)
Zoungrana, Ousmane ULiege

Doctoral thesis (2021)

This thesis analyses, from a socio-anthropological perspective, the problem of local resistance to the diffusion of compressed earth bricks (CEB) in the city of Ouagadougou. Firstly, the thesis shows that ... [more ▼]

This thesis analyses, from a socio-anthropological perspective, the problem of local resistance to the diffusion of compressed earth bricks (CEB) in the city of Ouagadougou. Firstly, the thesis shows that the main obstacles to the diffusion of CEB are embedded in the conduct and implementation of public policies in the sector. This mixed record of public action for valorization of local materials has nevertheless led to individualistic and private strategies for building using CEB in the long term. Secondly, the thesis shows that these individual strategies of construction in its contemporary form is the prerogative of an urban elite with high economic and cultural capital. For these elites, the choice of CEB is based on four interconnected forms of justification: (i) a technical justification based on an ecological reasoning, (ii) a culture of social distinction; (iii) an identity-based justification, (iv) a justification based on post-materialist values related to the global issues of the sustainable development goals. Moreover, this thesis shows that four forms of social representation coexist in the CEB sector in Ouagadougou, the most shared endogenously being that of the "material for the poor". However, the paradox lies in the fact that the CEB is adopted by an urban elite that has a positive vision of the material. Finally, the analysis of the arena of the public post-policy of the CEB revealed that the supply of production remains private. It is characterized by a strategy of production by opportunity that addresses a very specific “niche market” segment of applicants whose preferences are oriented towards bioclimatic construction. In terms of construction, a square meter of CEB wall is less expensive (9897 FCFA) than that of hollow cement blocks (16000 FCFA). During the usage, the building built with CEB wall offers less hours of thermal discomfort (20% less) than a building built with hollow cement block wall. It also saves on electricity consumption (10%) if an air conditioner is used to maintain the temperature at 28 °C. However, this return on investment in terms of energy consumption is relative, with regards to the society where ecological reasoning in construction are not sufficiently rooted in the domestic culture of households. Moreover, in view of the obstacles mentioned above and the new forms of justification, the thesis shows that one of the ways of regaining the confidence in CEB would be through the dissemination of ecological reasoning in Burkinabè society. Keywords: Compressed Earth Brick, Public Policies, Social Representations, Bioclimatic habitats, Indigenousness, Post-Materialist Values, Sustainable Development, Burkina Faso [less ▲]

Detailed reference viewed: 42 (9 ULiège)
Full Text
See detailInfection of European eel by Anguillid herpesvirus 1: from basic research to conservation programs
Delrez, Natacha ULiege

Doctoral thesis (2021)

The European eel (Anguilla Anguilla) is a culturally and commercially important fish species and along with other members of the genus Anguilla, they are flagship species for aquatic conservation efforts ... [more ▼]

The European eel (Anguilla Anguilla) is a culturally and commercially important fish species and along with other members of the genus Anguilla, they are flagship species for aquatic conservation efforts. Anguillid eels have a fascinating and complex life cycle involving different life stages and extended migration through both marine and freshwater environments. The lifecycle of the European eel begins in the Atlantic Ocean. After hatching, leptocephali larvae drift thousands of kilometres across the ocean to reach continental coastal waters where they metamorphose into glass eels. These juvenile eels then migrate upstream towards freshwater habitats where they grow into yellow eels and remain there for several years. Finally, they fully mature into silver eels and migrate back to their place of birth, where they reproduce before dying. Within the last 50 years, the European eel population has dramatically decline and the species is now critically endangered. The reason for this steep decline in population is likely to be multifactorial, with one potential major factor being infectious diseases. In terms of viral diseases, Anguillid herpesvirus 1 (AngHV 1) is the causative agent of a haemorrhagic disease affecting freshwater eels (Anguilla spp.), and is one of the most frequently detected viruses from European eels, especially in fish farms. This herpesvirus is a member of the genus cyprinivirus of the family Alloherpesviridae. As a consequence of this decline, the European Commission has established the “Eel Recovery Plan” within member states with the aim of protecting and restoring the population of European eel. One of the main measures of this plan relies on restocking. This process involves the active transfer of eels to inland areas where eel populations have declined. Although this restocking is widely practiced in Europe, additional studies are still needed to evaluate and improve its effectiveness. The broad objective of the present thesis was to contribute to the conservation of the critically endangered European eel, through focusing on infectious diseases as one of the potential causative factors of its decline. Firstly, we investigated the sanitary status of wild caught glass eels entering estuaries and aimed to develop quarantine stations that would facilitate the implementation of therapeutic and prophylactic measures prior to their reintroduction into the wild. Our results showed that glass eels were negative for AngHV-1 before their reintroduction into Belgian rivers. We also established that under certain conditions, a two-week pre-release quarantine period could be implemented without major impact on important metrics such as eel survival rate, sanitary status, health and morphology. One of the major goals of this PhD project was to gain insights into AngHV-1 pathogenesis using recombinant viral strains combined with in vivo bioluminescent imaging (IVIS). As a prerequisite for the study of AngHV 1 pathogenesis, we sequenced the entire genome of seven strains of AngHV-1 from different geographic origins and compared their biological properties in vitro, which also provided insights into the evolution of this virus. Based on this, we selected 4 strains representative of the viral species, compared their properties in vivo and produced recombinants expressing luciferase and a copepod green fluorescent protein (here after named LucGFP). Characterization of these recombinants revealed that they are appropriate for the study of AngHV-1 with no detectable negative effect associated with the insertion of the transgene. As all strains expressed comparable properties in vivo, the UK LucGFP strain was selected for the next steps of the project. Using the UK LucGFP strain and the IVIS, we investigated major questions related to the pathogenesis of AngHV-1 infection in its natural host: These experiments led to the following observations: (i) Glass eels are not susceptible to AngHV-1 infection through the natural route tested. (ii) Inoculation of elvers led to few positive subjects expressing bioluminescence on their cephalic part, mainly gills and jaws, with no spreading of the infection between subjects according to time. (iii) Inoculation of yellow eels led to infection of all subjects expressing bioluminescence signal associated with strong clinical signs. Morbidity and cumulated mortality reached 100% and 20% respectively. (iv) The gills and the periodontal mucosa represented major portals of entry of the virus into naïve subjects. (v) Two modes of transmission of AngHV-1 were highlighted in this study, i.e. direct transmission through interspecific agonistic interactions (e.g. biting) between fish, and indirect transmission through environmental water. Our results indicate that AngHV 1 transmission via contaminated water requires a high density of subjects and virions, and is thus probably restricted to intensive aquaculture conditions. On the other hand, AngHV-1 infection mediated by biting appears highly efficient and is likely to be facilitated in environments with either high or low host density. We hypothesize that viral transmission mediated by interspecific agonistic interactions may partially explain the high prevalence of AngHV 1 in the wild despite the low infectivity of AngHV-1 in water, the low and declining host population density, the solitary behaviour of the host, and the strong ability of fish skin mucus to neutralize pathogens such as AngHV 1. In conclusion, this project contributed to recommendations for optimization of glass eel restocking practices in Belgium and highlighted major aspects of AngHV 1 pathogenesis. The findings create ample scope for future projects in relation to eel conservation, AngHV 1 evolution, host-pathogen dynamics in aquatic environments as well as setting the groundwork for AngHV 1 vaccine development. [less ▲]

Detailed reference viewed: 53 (5 ULiège)
Full Text
See detailEnjeux fonciers et développement de l'agriculture familiale au Sud-Kivu
Bahati Shamamba, Dieudonné ULiege

Doctoral thesis (2021)

La République démocratique du Congo (RDC) présente une réalité contrastée du point de vue du foncier. On rencontre des fortes densités de population dans la partie Est alors que la densité moyenne ... [more ▼]

La République démocratique du Congo (RDC) présente une réalité contrastée du point de vue du foncier. On rencontre des fortes densités de population dans la partie Est alors que la densité moyenne n’atteint pas 40 habitants/km² pour l’ensemble du territoire national. Il en résulte une forte pression sur les terres à l’Est du pays du fait d’une croissance rapide de la population, de la concentration de la terre par les élites, et de la sollicitation de la terre en milieu rural pour d’autres finalités en dehors de l’agriculture à savoir l’exploitation minière, l’habitat, etc. Par ailleurs, la législation foncière telle qu’organisée en RDC est incomplète en ce qui concerne la gestion des terres paysannes. Par conséquent, ces terres sont constamment exposées aux pratiques d’accaparement par des élites politiques, militaires et des riches commerçants. Le contexte socio politique, caractérisé par l’insécurité et les mouvements des populations, a amplifié ces pratiques ; d’où l’explosion des conflits fonciers, l’accès difficile à la terre par les paysans et l’insécurité des droits fonciers paysans issus essentiellement de la coutume. La province du Sud Kivu fait partie des régions orientales de la RDC caractérisées par la réalité foncière décrite ci-dessus. Dès lors, le présent travail s’est inscrit dans la démarche visant à contribuer à une meilleure gestion de la ressource terre dans la province au Sud Kivu, au profit des petits producteurs agricoles. De manière spécifique, l’étude a visé premièrement à documenter l’accès à la terre par les ménages paysans c’est-à-dire déterminer la disponibilité foncière pour les ménages et les modes d’accès à la terre ; deuxièmement à déterminer la manière dont l’accès à la terre influence les pratiques agricoles ainsi que les choix techniques au niveau des ménages et enfin à identifier les solutions développées par les ménages en vue de faire face à la pression foncière accrue dans leur milieu. En vue d’atteindre ces objectifs, ce travail s’est réalisé à travers une diversité d’outils méthodologiques. Il s’agit d’une enquête des ménages conduite auprès de 120 ménages dans le groupement Mbinga Sud, en territoire de Kalehe. Le territoire de Kalehe a été choisi du fait du contexte foncier particulier y prévalent qui fait en sorte que la terre soit au centre des questions d’identité et de pouvoir. D’où des nombreuses pratiques d’accaparement des terres y sont documentées, de même que des conflits fonciers débouchant parfois sur de la violence. Les données issues des ménages ont été complétées par des enquêtes conduites auprès d’autres parties prenantes autour du foncier à savoir les grands concessionnaires auprès de qui les ménages prennent la terre en location, l’autorité coutumière, l’administration foncière, les organisations locales de développement, l’église et le pouvoir public. Des informations supplémentaires sur les questions foncières au Sud Kivu en général et à Kalehe en particulier ont été obtenues grâce à la recherche action participative (RAP) à travers l’organisation des théâtres participatifs, des dialogues entre métayers et grands concessionnaires. Les résultats obtenus dans ce travail font état d’une réelle difficulté d’accès à la terre par les ménages de Kalehe. Cette difficulté se traduit d’une part par l’exiguïté des étendues de terres à leur disposition et d’autre part par les conditions difficiles auxquelles les ménages font face dans la location des terres en vue de compenser la faiblesse qui s’observe dans la propriété foncière. Ceci se manifeste aussi bien par le prix de location élevé que par les restrictions auxquelles les ménages sont soumis dans la pratique de location ; ce qui les limite considérablement dans le choix des cultures, des variétés et des itinéraires techniques à envisager sur les terres louées. Toutefois, la location des terres paraît comme une importante alternative dans l’accès à la terre pour les jeunes paysans et les femmes qui n’ont pas la possibilité d’en hériter et qui sont défavorisées par les pratiques coutumières d’accès à la terre respectivement. Il ressort des résultats de ce travail une difficulté actuelle et à venir dans l’obtention des terres par les voies coutumières, principalement par le contrat coutumier kalinzi. D’où l’émergence de l’achat et de la location comme modes alternatifs d’accès à la terre à Kalehe. Les deux sont malheureusement confrontés respectivement à la surenchère foncière due à la forte attractivité des terres par les élites et les conditions de location très contraignantes. A l’issu de ce travail, il apparait la nécessité d’accélérer le processus de réforme foncière en cours en RDC. Devant l’augmentation rapide de la population, une réforme agraire associée à des politiques agricoles cohérentes est importante pour l’avenir de l’agriculture familiale dans la région. Etant donné l’importance que prend de plus en plus la pratique de location de terres, il serait important que cette dernière soit règlementée par le pouvoir public, au profit des paysans. [less ▲]

Detailed reference viewed: 75 (21 ULiège)
Full Text
See detailProductivité, efficience et profitabilité des petites exploitations agricoles dans la région des sols de laves au Rwanda
Maniriho, Aristide ULiege

Doctoral thesis (2021)

In intention to respond to the demand for food in both quantity and quality of the growing population in Africa, it will be necessary to apply appropriate agricultural technologies to the fragile soils of ... [more ▼]

In intention to respond to the demand for food in both quantity and quality of the growing population in Africa, it will be necessary to apply appropriate agricultural technologies to the fragile soils of this continent to increase productivity and achieve food security. In the context of Rwanda, the use of fertilizers and pesticides raises a dispute between the Ministry of Agriculture and Livestock and the Rwandan Office responsible for the protection of the environment. While the former advocates the intensive use of fertilizers and pesticides, the exploitation of swamps to increase agricultural production, the latter stresses that this will lead to pollution of the environment. The Government of Rwanda has adopted, for more than a decade, a sequence of policies and strategies aiming at economic development and improving the living standards of its primarily agrarian population. In the agricultural sector, the adoption of technology packages and increased production has been accompanied by the implementation of these strategies. We should emphasize, however, that the country's economy is still dominated by subsistence agriculture, with a gap between potential and current production for the priority crops selected under the agricultural intensification and regional specialization program. This research endeavors to highlight the role of small farms (1.0 hectare at most) in agricultural development in Rwanda by considering two points of high sensitivity, in particular the peasantry and plant production (potato, corn, beans, wheat, vegetables), more specifically in the Volcanic Agro-ecological Zone, in the Burera and Musanze districts of the Northern Province, as well as Nyabihu and Rubavu in the Western Province. Data collected for this study focused on different points such as the socioeconomic characteristics of farmers and their households, characteristics of farms (size and crop), perception of farmers on the usefulness of agricultural techniques, the agricultural methods actually practiced by farmers, information related to labor, inputs, pesticides, agricultural equipment and tools, rent (or cost of access to land), transport cost, production and selling price, as well as living conditions (habitat, food, access to water as well as cooking and lighting energy). The different methods, namely those of documentary analysis, questionnaire survey, direct observation and interview were used to collect quantitative and qualitative data on the 401 small farmers (including 132 potato producers, 39 bean producers, 24 maize producers, 14 sorghum producers, 51 red onion producers, 43 white onion producers, 50 cabbage producers, 46 carrot producers, 1 producer for wheat and 1 for pyrethrum) in the Volcanic Highlands in Rwanda. Data analysis was done using statistical, econometric and budgetary methods. The descriptive statistics (frequencies, percentage, and means) were calculated and made it possible to order the perceptions of agricultural producers on the selected agricultural methods, as well as the agricultural techniques practiced on the holdings. They were also calculated to identify the components of production costs, reveal the importance of the sources of food products consumed in the households of farmers, and to identify the distribution of consumption expenditure among the various items. Correlational analysis and the "lowess" curve allowed us to identify the determinants of agricultural yield and those of farm profitability, while the budgetary method and cost-benefit analysis facilitated the estimation of the profitability of small-scale farms. The Student Test was used to locate the difference between the average cultivated land, the average yields, the average selling prices and the average net farm income between onion producers and potato producers. After forming hierarchical groups of mutually exclusive smallholder farms in terms of their profitability, the analysis of variance was used to test the variability of performance indicators among the three categories of smallholder farmers: lower-performing smallholders, medium-performing smallholders, and higher-performing smallholders. The econometric approach was used to identify the determinants of effectiveness, while the CARI approach was used to statute the food security status of the small-scale farmers in the study area. The results from the analysis using the Likert scale show that, in order of importance, the most commonly used farming techniques, the results show that, in order of importance, these are: timely sowing, appropriate use of organic fertilisers, use of high-yielding seeds, harvesting at the point of ripening, combination of crop and livestock farming, appropriate use of pesticides, crop rotation, reasoned combination of chemical and organic fertilisers, and crop combination. As for the examination of the presupposed effects of certain techniques on which small-scale farmers express their perceptions of their role, by importance, the techniques perceived as most likely to promote soil fertility and productivity are: use of organic fertilisers, soil protection against erosion, combination of crop and livestock farming, crop rotation, reasoned combination of chemical and organic fertilisers, use of chemical fertilisers, agroforestry, and crop combination. Making further use of our survey data for the 2019 B season, comparative analysis shows that there is no significant difference between the size of land used for potato production and that used for onion production, that onion yields are significantly higher than potato yields, that the selling price of onion is significantly higher than that of potato, and that the average income of an onion producer is significantly higher than the average income of a potato producer in the lava soil region of Rwanda. In terms of profitability analysis, the results indicate that for all crops, the net farm income (NFI) is greater than zero and the benefit-cost ratio (BCR) is greater than 1. Furthermore, these results show that onion is more profitable than potato. Compared to 2009, the results of our study show that the potato, bean, maize and sorghum farms were still profitable in 2019, although, unlike the 3 crops, the potato yield had significantly decreased. The correlational analysis and the "lowess" curve show that crop yield is correlated with the amount of fertilizers (DAP, urea, manure) and pesticides used, as well as the area of land farmed, even though this relationship is not always linear. For the econometric analysis, the results of the linear regression identified the level of performance, cooperative membership, access to credit, market access, access to extension services, adoption of high-yielding varieties, crop rotation, farm location, and the crop grown as factors significantly influencing small-scale farmers’ effectiveness. The level of efficiency (TFP=3.48) shows that small-scale farmers underuse their resources. In addition, the analysis of variance shows the highly significant variability in yield, level of effectiveness, efficiency of resource allocation, cost of production, and net farm income both between the three categories of smallholder farmers as well as among crops. In addition, the results from most recent studies on the domestic resource cost show that, except for maize, the domestic resource cost (DRC) ratio of all crops is less than 1, which implies that the value chains of these crops are viable in the world economy, given that these agricultural products have a comparative advantage in international trade. With the CARI approach, we were able to classify smallholder farm households into poor food situations (3.5%), limited food situations (21.5%), and acceptable food situations (75.1%). On the basis of the results of this research, the proper use of inputs (NPK, urea, manure, dithane), the size of the land farmed and the role of the cow in the farm should be considered in order to increase the crop yield; the functioning of institutions (cooperatives, credit, extension, market) as well as the good practice of farming techniques (seed selection, use of fertilisers, choice of crop) should be considered. Econometric estimates show that potato producers are three times more likely to be food secure than non-potato producers, and that potato is more important for food security among lower-performing smallholders than among the other two categories of smallholders. While recognising the role of potatoes in food security, small-scale producers should alternate the production of different crops in order to benefit from the advantages of each crop in increasing and stabilising farm incomes as well as in improving living conditions. [less ▲]

Detailed reference viewed: 115 (59 ULiège)
Full Text
See detailMélanges et compaction d'assemblages granulaires
Pillitteri, Salvatore ULiege

Doctoral thesis (2021)

A granular pile submitted to a vibration or a series of shakes increases its packing fraction. This phenomenon, called compaction, can be used to densify granular materials or as a measurement method to ... [more ▼]

A granular pile submitted to a vibration or a series of shakes increases its packing fraction. This phenomenon, called compaction, can be used to densify granular materials or as a measurement method to characterize the flow properties of a powder. This method is also popular in the pharmaceutical industry because of its ease of use. Although the phenomenon of compaction has been studied for a long time, it remains poorly understood and most of models describing its dynamics are empirical. This work focuses on compaction and the impact of parameters like the conditions of vibration and the granulometry of the granular medium on the dynamics of this phenomenon. This thesis is presented as a collection of articles, linked together by the search for control parameters and the process optimization. [less ▲]

Detailed reference viewed: 33 (10 ULiège)
Full Text
See detailNew insights into the enzymatic properties and metabolic profile of the phytopathogen Streptomyces scabiei
Deflandre, Benoit ULiege

Doctoral thesis (2021)

Streptomyces scabiei (syn. Streptomyces scabies) is a phytopathogenic Gram-positive bacterium known as the causative agent of common scab disease. This microorganism causes, together with about 20 other ... [more ▼]

Streptomyces scabiei (syn. Streptomyces scabies) is a phytopathogenic Gram-positive bacterium known as the causative agent of common scab disease. This microorganism causes, together with about 20 other species in the Streptomyces genus, skin lesions affecting tuber crops and mainly reducing the marketability of potatoes. S. scabiei 87-22 is considered the model strain for the study of virulence-associated mechanisms and has been used to highlight the regulatory network governing the biosynthesis of its main pathogenicity determinant, thaxtomin A. This phytotoxin – acting as an inhibitor of cellulose biosynthesis – is shared by most common scab causing streptomycetes and is the only virulence factor considered to be essential for their success in host colonization. Cellulose oligosaccharides (cello-oligosaccharides) have been shown to be the elicitors of thaxtomin production and, by extension, the triggers of the pathogenic lifestyle. In this work, we reveal the wide effects of these oligosaccharides as inducers of additional genes and specialized metabolites which have thereby been attributed to the so-called ‘virulome’ of S. scabiei. We also provide the first comprehensive and manually curated genome mining analysis of a pathogenic Streptomyces strain, revealing its impressive potential for the biosynthesis of specialized metabolites. Concomitantly to cello-oligosaccharides import, S. scabiei activates a central gene encoding the β-glucosidase BglC involved in the control of the pool of thaxtomin elicitors, and the scopolin phytoalexin which appears to be meaningful in the feedback control of thaxtomin production. However, the loss of this gene leads to major physiological modifications and unexpected phenotypes which indicate yet unknown functions. Studying the adaptations of the bglC null mutant revealed an intriguing phenomenon of genetic compensation causing the transcriptional activation of two other genes, namely bcpE1 and bcpE2. These genes encode two other β-glucosidases which fulfill distinct roles to functionally replace BglC, i.e., BcpE1 is similarly active on cello-oligosaccharides, and BcpE2 hydrolyzes a wide range of plant heterosides including the scopolin phytoalexin. Finally, we provide the first reported characterization of the amylolytic system of S. scabiei which was a surprisingly overlooked aspect for a bacterium that colonizes plant storage organs. We have investigated its ability to consume starch and related carbohydrates to find that maltose was poorly utilized by S. scabiei. This unexpected phenotype was attributed to a strong repressive control mediated by the MalR transcriptional regulator which was also shown to be involved in the maltose-dependent control of the secreted amylase enzymes. Overall, the present work provides insights into the understanding of i) the diversity of the virulome of S. scabiei, ii) the molecular mechanisms associated with the multiple roles of bglC/BglC, and iii) the primary metabolism dedicated to the utilization of the most abundant storage carbohydrates of tuber hosts. [less ▲]

Detailed reference viewed: 37 (1 ULiège)
Full Text
See detailInvasion de Tuta absoluta au Burkina Faso : Impact, recherche et propositions de stratégies de gestion
Sawadogo, Wendnéyidé Mathieu ULiege

Doctoral thesis (2021)

La mineuse sud-américaine de la tomate Tuta absoluta (Meyrick, 1917) (Lepidoptera : Gelechiidae) est l'un des ravageurs les plus redoutés de la tomate. Elle a été découverte en 2016 au Burkina Faso, un ... [more ▼]

La mineuse sud-américaine de la tomate Tuta absoluta (Meyrick, 1917) (Lepidoptera : Gelechiidae) est l'un des ravageurs les plus redoutés de la tomate. Elle a été découverte en 2016 au Burkina Faso, un pays où la filière tomate joue un rôle socio-économique et nutritionnel très important. Cette thèse a été initiée pour acquérir les connaissances nécessaires au développement de recommandations et méthodes de lutte contre cette espèce exotique envahissante. Les résultats d’enquêtes menées auprès des producteurs de tomate burkinabés suggèrent que ceux-ci subissent d’énormes pertes économiques qui les obligent à faire un usage déraisonnable, et souvent infructueux, d’insecticides chimiques de synthèse. En évaluant le niveau de résistance développé par les populations de mineuses, nous avons pu établir une liste positive de produits phytosanitaires encore efficaces. Des insecticides biologiques à base d’extraits végétaux atteignent également un niveau d’efficacité larvicide satisfaisant. La phénologie de cette espèce a été caractérisée durant deux années complètes, suggérant deux pics annuels d’abondance du ravageur. L’espèce réalise une reproduction sexuée toute l’année, mais en cas d’absence de mâle, pratique une reproduction parthénogénétique deutérotoque. Parmi les alternatives aux pesticides identifiées durant ce travail, nous avons démontré que Nesidiocoris tenuis (Hemiptera : Miridae), prédateur des œufs et des jeunes larves de la mineuse, est présent et abondant dans de nombreuses surfaces agricoles du pays et pourrait être un allié de choix si des pesticides biologiques sont préférés aux insecticides de synthèse. De même, nos essais démontrent que Gynandropsis gynandra (Capparaceae), une plante potagère comestible et très appétente pour N. tenuis, pourrait favoriser le maintien et la prolifération du prédateur dans les champs de tomates. Aussi, nous avons montré que les variétés de tomate Mongal, Cobra 26 F1 et Kanon F1 ont les meilleures aptitudes à contenir les attaques de la mineuse. Des stratégies de lutte intégrée, valorisant judicieusement ces différents résultats, permettraient de contenir les invasions de cette mineuse au Burkina Faso. Parmi les solutions présentées au terme de ce travail : la modification des périodes de semi et récolte, l’arrachage des plantes hôtes alternatives du genre Solanum, l’emploi de biocides efficaces et respectueux des espèces locales, et d’autres approches agroécologiques destinées à favoriser les populations d’ennemis naturels. [less ▲]

Detailed reference viewed: 54 (20 ULiège)
Full Text
See detailSupervised machine learning under constraints
Begon, Jean-Michel ULiege

Doctoral thesis (2021)

As supervised learning occupies a larger and larger place in our everyday life, it is met with more and more constrained settings. Dealing with those constraints is a key to fostering new progress in the ... [more ▼]

As supervised learning occupies a larger and larger place in our everyday life, it is met with more and more constrained settings. Dealing with those constraints is a key to fostering new progress in the field, expanding ever further the limit of machine learning---a likely necessary step to reach artificial general intelligence. Supervised learning is an inductive paradigm in which time and data are refined into knowledge, in the form of predictive models. Models which can sometimes be, it must be conceded, opaque, memory demanding and energy consuming. Given this setting, a constraint can mean any number of things. Essentially, a constraint is anything that stand in the way of supervised learning, be it the lack of time, of memory, of data, or of understanding. Additionally, the scope of applicability of supervised learning is so vast it can appear daunting. Usefulness can be found in areas including medical analysis and autonomous driving---areas for which strong guarantees are required. All those constraints (time, memory, data, interpretability, reliability) might somewhat conflict with the traditional goal of supervised learning. In such a case, finding a balance between the constraints and the standard objective is problem-dependent, thus requiring generic solutions. Alternatively, concerns might arise after learning, in which case solutions must be developed under sub-optimal conditions, resulting in constraints adding up. An example of such situations is trying to enforce reliability once the data is no longer available. After detailing the background (what is supervised learning and why is it difficult, what algorithms will be used, where does it land in the broader scope of knowledge) in which this thesis integrates itself, we will discuss four different scenarios. The first one is about trying to learn a good decision forest model of a limited size, without learning first a large model and then compressing it. For that, we have developed the Globally Induced Forest (GIF) algorithm, which mixes local and global optimizations to produce accurate predictions under memory constraints in reasonable time. More specifically, the global part allows to sidestep the redundancy inherent in traditional decision forests. It is shown that the proposed method is more than competitive with standard tree-based ensembles under corresponding constraints, and can sometimes even surpass much larger models. The second scenario corresponds to the example given above: trying to enforce reliability without data. More specifically, the focus in on out-of-distribution (OOD) detection: recognizing samples which do not come from the original distribution the model was learned from. Tackling this problem with utter lack of data is challenging. Our investigation focuses on image classification with convolutional neural networks. Indicators which can be computed alongside the prediction with little additional cost are proposed. These indicators prove useful, stable and complementary for OOD detection. We also introduce a surprisingly simple, yet effective summary indicator, shown to perform well across several networks and datasets. It can easily be tuned further as soon as samples become available. Overall, interesting results can be reached in all but the most severe settings, for which it was a priori doubtful to come up with a data-free solution. The third scenario relates to transferring the knowledge of a large model in a smaller one in the absence of data. To do so, we propose to leverage a collection of unlabeled data which are easy to come up with in domains such as image classification. Two schemes are proposed (and then analyzed) to provide optimal transfer. Firstly, we proposed a biasing mechanism in the choice of unlabeled data to use so that the focus is on the more relevant samples. Secondly, we designed a teaching mechanism, applicable for almost all pairs of large and small networks, which allows for a much better knowledge transfer between the networks. Overall, good results are obtainable in decent time provided the collection of data actually contains relevant samples. The fourth scenario tackles the problem of interpretability: what knowledge can be gleaned more or less indirectly from data. We discuss two subproblems. The first one is to showcase that GIFs (cf. supra) can be used to derive intrinsically interpretable models. The second consists in a comparative study between methods and types of models (namely decision forests and neural networks) for the specific purpose of quantifying how much each variable is important in a given problem. After a preliminary study on benchmark datasets, the analysis turns to a concrete biological problem: inferring gene regulatory network from data. An ambivalent conclusion is reached: neural networks can be made to perform better than decision forests at predicting in almost all instances but struggle to identify the relevant variables in some situations. It would seem that better (motivated) methods need to be proposed for neural networks, especially in the face of highly non-linear problems. [less ▲]

Detailed reference viewed: 169 (28 ULiège)
Full Text
See detailCaractéristiques des élevages caprins et efficacité d'utilisation digestive des fourrages chez deux races de chèvres locale (sahélienne) et importée (majorera) dans la région de Fatick (Sénégal)
Sow, Fafa ULiege

Doctoral thesis (2021)

The challenges of animal production in Southern countries are to increase productivity, preserve environment, maintain rural manufacturing, fight against poverty and promote economic integration. These ... [more ▼]

The challenges of animal production in Southern countries are to increase productivity, preserve environment, maintain rural manufacturing, fight against poverty and promote economic integration. These points strongly commit Research to development of animal production. In Senegal, changes in the agricultural context have gradually led to marginalisation of livestock farming, in particular goat farming, and this makes it necessary to identify new strategies for adapting this speculation in order to be productive and at the service of the population. Major livestock development programs focus mainly on large ruminants. However, in the small ruminant sector, particularly goats, the State encourages genetic improvement using non-indigenous breeds, without any accompanying measures, either organisational or technical. The aim of this thesis is to provide knowledge that could be used to guide goat breeding programs and to promote improved breed productivity in low-input production systems. It aims to gain better understanding of goat farming systems in Senegal, and to work with farmers to propose ways to improve the sector, taking into account family considerations, cultural context and socio-political regulations of the Institutions. As the current requirements are those of productive and sustainable livestock production, it was necessary to compare the feed efficiency of indigenous (Sahelian) and imported (Majorera) breeds in order to highlight the allocation of nutrients between the physiological functions of production and adaptation in a constrained goat environment. Therefore four studies were carried out. The first study was the characterisation of goat production systems on family farms in the area of Fatick, Senegal. A survey was conducted among 45 farmers in four localities. It revealed that the farmers were all agro-pastoralists practising a mixed farming system. The majority (93%) supplemented their animals with agricultural by-products, agroforestry resources and kitchen scraps. A multiple correspondence analysis identified three groups: a first group, consisting of producers and processors of milk into traditional curdled milk, practising the sale of animals for household needs; a second, more specialised group of milk processors into yoghurt and cheese; and a third, (agro) pastoral group of goat sellers. Identification of goat husbandry practices related to feeding and housing and prospects for improvement in the same area was the focus of the second study. Surveys were conducted among eighty (80) herders (19% male and 81% female) in five villages. Based on the associated practices and objectives, an analysis of the main components revealed three categories of herders: "Innovators - Milk", "Innovators - Intermediate" and "Tradition". The first two groups were the largest (32.5 and 40%, respectively). The first group used natural pastures, agricultural residues, and natural woodland and raised goat herds. Its members gave particular importance to these practices to achieve milk production targets. The second group favoured fodder and woody crops and employed goat farm, all associated with a main objective of organic manure production. The third group used traditional housing combined with livestock farming based on sale of animals and meat consumption. However, it appeared that goat housing and feeding practices based on fodder crops were similar and highlighted herders wishes to "stabilise" the goats permanently, close to the house, mainly to protect their animals from bad weather. Heavy rainfall during rainy season, in particular, favours diseases and mortality, especially among young animals. Studies 3 and 4 aimed to provide zootechnical advice to livestock farmers. They compared the Spanish breed Majorera, which has a good performance in milk production, with the local breed, Sahelian goat, on dietary efficiency of energy and nitrogen of a locally available resource, cowpea haulm, Vigna unguiculata, variety 58/74, and their possible relationships with faecal microbiota. The results showed that the Majorera and Sahelian goats had similar levels of dry matter (DM) intake and nutrient digestibility. On the basis of metabolic weight, intake of dry matter, gross energy, digestible energy, metabolisable energy and net energy , and energy lost as methane production were significantly higher (p < 0.01) in the non-native goats than in the Sahelian goats. Urinary excretion of energy was similar (p = 0.9) between breeds, while the loss of faecal energy was higher in Majorera than in Sahelian goats. The milk energy production of Majorera goats was higher than that of Sahelian goats (p < 0.05). However, the conversion yield from metabolisable energy to net energy (klm) was not affected by breed (p = 0.37), while nitrogen intake, milk nitrogen to nitrogen conversion yield and faecal nitrogen losses, relative to metabolic weight, were significantly higher (p < 0.05) in Majorera goats than in Sahelian goats. In contrast, the fraction of dietary nitrogen excreted in urine was higher in Sahelian animals. Breed factor had no effect on nitrogen retention, nitrogen digestibility, urine nitrogen and nitrogen utilization efficiency. Amplicon profiling of the 16S ribosomal RNA gene showed that the relative abundance of phyla in the faecal microbiota was similar between breeds, highlighting the dominance of phyla firmicutes with 94.4% of the total sequences, followed by Actinobacteria with 3.7% of the sequences. Bacteroidetes represented 0.7% of the total sequences. The proportions of Lactobacillales, Erysipelotrichales and Bifidobacteria were higher in Majorera goats than in Sahelian goats (p ≤ 0.05), in contrast to Elusimicrobials (p ≤ 0.04). No significant effect of breed on bacterial diversity was observed (R-ANOSIM = 0.198; P = 0.082). However, out of the 284 genera identified in our samples, eight (08) genera of bacteria showed breed difference, i.e, the genera Atopostipes, Bifidobacteriacea_ge, Defluviitaleacea-UCG-011, Enteractinicoccus, Lachnospiraceae-UCG-008, Muribaculaceae_ge and Roseburia were significantly more represented in animals of allochthonous race (p = 0.037), as opposed to Bacillus (p = 0.045). In conclusion, goats of both breeds were similar in terms of energy efficiency and nitrogen use, despite higher daily milk production and dry matter consumption in Majorera goats. The goats were also similar in terms of energy and nitrogen digestibility and faecal microbiota. In conclusion, the Majorera breed is likely to be more dependent on a high nergy diet than the Sahelian breed as suggested by a higher basal metabolism. [less ▲]

Detailed reference viewed: 28 (3 ULiège)
Full Text
See detailEfficient Multi-Level Measurements and Modeling of Computer Networks
Grailet, Jean-François ULiege

Doctoral thesis (2021)

(abstract) Since the 1980’s, the Internet has steadily grown in size to deliver various services to an increasingly large public, which amounts to billions of users as of the beginning of the 2020’s. As a ... [more ▼]

(abstract) Since the 1980’s, the Internet has steadily grown in size to deliver various services to an increasingly large public, which amounts to billions of users as of the beginning of the 2020’s. As a consequence, its infrastructure has considerably evolved too, which prompted the research community to investigate the topology of the Internet at multiple levels. The highest level is the AS-level (Autonomous System), an Autonomous System being a vast computer network operated by a single company, such as an ISP (Internet Service Provider). Not only the way Autonomous Systems communicate with each other has been investigated, but also their internal networks has drawn the attention of the research community, as many works focused on the mapping and the modeling of the router-level, i.e., how routers are interconnected either within a single AS or at the borders of adjacent ASes. The Internet router-level has been investigated not only to discover its structure, but also to understand its dynamics. Starting from the 2000’s, the research community focused on how the routers balance the traffic between several links to handle the increasingly large amount of network traffic, a process which is commonly denoted as load balancing (a form of traffic engineering). Additionnal works on the router-level aimed at characterizing meshes of routers, i.e., routers that are directly connected at the data link layer (or Layer-2) to manage a large number of links as if they were a single router. In the meantime, the research community also explored other levels of the Internet to complement router-level maps, such as a subnet-level, a subnet (short for subnetwork) being a group of network interfaces that can contact each other directly at the data link layer. This thesis aims at designing new topology discovery techniques to efficiently map the intra-domain topologies of large networks by exploring their different levels and the relationships that exist between these levels, all while dealing with the effects of load balancing. Three different levels are investigated: the router-level, the subnet-level, and the hop-level. The hop-level characterizes how routers or meshes exchange packets at the network layer (or Layer-3), and can therefore be used to study the internal forwarding of a network without extensively discovering its router-level. Not only this thesis provides new topology discovery schemes to map each level, but it also combines them to increase their accuracy. In particular, it introduces a new subnet inference methodology that takes advantage of alias resolution (i.e., the process of determining whether or not a group or pair of network interfaces belong to the same device) to solve ambiguous scenarios, as well as a topology mapping scheme that relies on both subnet-level data and alias resolution to build comprehensive hop-level maps of intra-domain topologies. Moreover, these maps can be interpreted with bipartite formalisms to more easily study their topological features. All topology discovery methods developed for this thesis are comprehensively elaborated and assessed in this document. The tools that implement these methods ( WISE and SAGE ), their source code, and the data they could collect on various Autonomous Systems are publicly available. [less ▲]

Detailed reference viewed: 88 (26 ULiège)
Full Text
See detailFirst and second principles study of magnetic and multiferroic properties of rare-earth orthoferrites
Sasani, Alireza ULiege

Doctoral thesis (2021)

Rare-earth orthoferrite perovskites (RFeO3, where R is a rare-earth element, i.e., La, Gd, Dy, …) are a family of materials that have attracted a lot of attention due to their original magnetic properties ... [more ▼]

Rare-earth orthoferrite perovskites (RFeO3, where R is a rare-earth element, i.e., La, Gd, Dy, …) are a family of materials that have attracted a lot of attention due to their original magnetic properties and large nonlinear magnetoelectric responses (ME). A large magnetoelectric response will allow controlling magnetic properties using an electric field which can bring in a plethora of applications and improvements of the current technologies. In my thesis, I have studied magnetic properties of rare-earth orthiferrites and I have made a Heisenberg model to explain the origin of different unique magnetic behaviors (spin reorientation and magnetization reversal) present in these rare-earth orthoferrites. We have then used the model to explain large ME responses observed in these materials. We have shown that the nonlinear response present in these materials arises from the fact that the antiferromagnetic ordering changes nonlinearly with an applied magnetic field. Through a collaboration with experimentalists, we have also studied ultrafast manipulation of the magnetic phase of DyFeO3 using laser pulses in an ultrafast time scale which allows the use of these materials in memories with ultrafast time responses. [less ▲]

Detailed reference viewed: 27 (5 ULiège)
Full Text
See detailIn silico, in vitro, and in vivo investigation for antihypertensive activity of quinoa protein and peptides
Guo, Huimin ULiege

Doctoral thesis (2021)

Quinoa, known as an ancient and underutilized crop, holds great promise to be an excellent protein source for its excellent nutritional and bioactive properties. The present study investigated the in ... [more ▼]

Quinoa, known as an ancient and underutilized crop, holds great promise to be an excellent protein source for its excellent nutritional and bioactive properties. The present study investigated the in silico-based potential bioactivity, in vitro angiotensin-I-converting enzyme (ACE) inhibitory activity, and in vivo blood pressure-lowering effect of quinoa protein and peptides, thus providing a better understanding of their antihypertensive mechanism and supporting their application in the development of functional foods. [less ▲]

Detailed reference viewed: 43 (7 ULiège)
Full Text
See detailStudy on green preparation of chondroitin sulfate and antiosteoporosis activity of chondroitin sulfate calcium complex
Shen, Qingshan ULiege

Doctoral thesis (2021)

China is the largest producer and exporter of chondroitin sulfate (CS), accounting for 80% of the world's CS production. For traditional CS isolation procedures, it is generally believed that high ... [more ▼]

China is the largest producer and exporter of chondroitin sulfate (CS), accounting for 80% of the world's CS production. For traditional CS isolation procedures, it is generally believed that high concentration alkaline treatment is required to break down the core protein. This produces a lot of effluent during industrial production, which is not environmentally friendly. About 30,000 tons of chicken sternal cartilage are produced in China each year, and most of them are usually processed into snacks or other low-value products. However, the constituents of chicken sternal cartilage are still undervalued and deserve to be considered for more economically competitive exploitation. Furthermore, the bioactivities of chondroitin sulfate metal complex, especially chondroitin sulfate calcium complex (CSCa), are poorly reported in vitro and in vivo. Based on the above-mentioned problems, the environmentally friendly preparation of CS from chicken sternal cartilage was proposed, and the bioactivities of CSCa were studied in vitro and in vivo. First, steam explosion (steam cracking) technology was used to liquefy chicken sternal cartilage for CS green preparation. The effects of experimental parameters, including pressure and holding time, on cartilage liquefaction were investigated. Part of the cartilage can be liquefied. The microstructural changes of the solid residue of the steam explosion treated cartilage were verified by scanning electron microscopy, and CS was obtained from the liquid fraction by enzymolysis and membrane separation technologies. The chemical and structural properties of CS were confirmed by Fourier transform infrared spectroscopy, agarose gel electrophoresis, nuclear magnetic resonance and chromatography. The results suggest that steam explosion can be used as a pretreatment method to liquefy cartilage for environmentally friendly isolation of CS. Next, another technology was proposed to completely liquefy chicken sternal cartilage. Hot-pressure technology with low temperature and long processing time was used to pretreat the cartilage for green CS preparation. After complete liquefaction by hot pressure, co-production of CS and peptides was achieved in an environmentally friendly manner by dual enzymatic hydrolysis and combined membrane separation technologies. The effects of hot-pressure parameters, including temperature and time, on the liquefaction of cartilage were investigated. Microstructural changes and migration of constituents in the solid residue of hot-pressure treated cartilage were verified by scanning electron microscopy and alcian blue staining. The chemical and structural properties of the CS sample were confirmed by Fourier transform infrared spectroscopy, agarose gel electrophoresis, chromatography and nuclear magnetic resonance. The results suggest that hot pressing can be used as a pretreatment method to liquefy cartilage for environmentally friendly industrial co-production of CS and peptides. In addition, chondroitin sulfate-calcium complex (CSCa) was fabricated, and the structural characteristics of CSCa and its proliferative bioactivity for chondrocyte were studied in vitro. The fabrication of CSCa was performed to study the maximum calcium retention capacity. The structural properties of CSCa were studied by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The characterization of CSCa was analyzed by scanning electron microscopy, energy dispersive spectrometer, ultraviolet and visible spectrophotometer, atomic force microscope and X-ray diffraction. Thermal properties were analyzed by thermogravimetric analysis and differential scanning calorimetry. Additionally, the effects of CSCa on chondrocyte growth, cell cycle and apoptosis were studied in vitro. The intracellular calcium ion level of the chondrocyte was assessed by fluorescent probe staining. And some proliferative-related genes influenced by CSCa were studied by real-time quantitative polymerase chain reaction. The results suggest that calcium ions can bind to sulfate or carboxyl groups of CS chains forming a polysaccharide-metal complex. CSCa could probably interact with the calcium-sensing receptor, increasing intracellular calcium ions and influencing the cell cycle. CSCa-induced secretion of TGF-β1 could activate the TGF-β/Smads pathway and alter the expression of proliferation-associated genes ultimately leading to chondrocyte proliferation. Finally, the anti-osteoporosis bioactivity of CSCa was studied in vivo. The ovariectomized rat model was constructed by bilateral ovariectomy to simulate estrogen deficiency-induced osteoporosis in postmenopausal women. Bone microarchitecture and bone mineral density were analyzed by microcomputed tomography. Bone turnover markers, including bone formation and resorption markers in serum, were determined by enzyme-linked immunosorbent assay. In addition, multi-omics methods including microbiome and metabolome were used to investigate the alteration of microbiota and changes of metabolic profiles in the faeces from ovariectomized rats subjected to a dietary intervention of CSCa for twelve weeks. The results suggest that, compared with the osteoporosis rats, CSCa, instead of CS, can improve bone mineral density and microstructure of the femur, and alter the level of bone turnover markers in serum. Additionally, CSCa altered the composition of gut microbiota as well as metabolite profiles in the faeces by 16S rRNA sequencing and metabolomics. Specifically, after CSCa intervention, the relative abundance of Acidobacteria, Chloroflexi, and Gemmatimonadetes increased while that of Bacteroidetes, Actinobacteria, and the Bacteroidetes/Firmicutes ratio decreased at the phylum level as well as some specific changes in the gut microbiota community at the genus level. Enriched metabolites of lipid metabolism, amino acid metabolism, and biodegradation and xenobiotic metabolism were distinguished from those of model rats. Correlation analysis showed that certain taxa of the gut microbiota were significantly correlated with osteoporosis phenotypes and enriched metabolites. Overall, dietary CSCa intervention has the potential to alleviate osteoporosis and associated symptoms by acting on gut microbiota composition or metabolite profiles, as demonstrated in rats. This study provides scientific evidence of the potential effects of dietary CSCa on osteoporosis. [less ▲]

Detailed reference viewed: 66 (11 ULiège)
Full Text
See detailDispositifs d’enseignement hybride : Étude des liens entre composantes pédagogiques, facteurs motivationnels et performances des étudiants
Sacre, Margault ULiege

Doctoral thesis (2021)

Blended learning is increasingly prevalent in higher education institutions, and this phenomenon has been further exacerbated by the COVID-19 crisis. However, the predictors of student performance in ... [more ▼]

Blended learning is increasingly prevalent in higher education institutions, and this phenomenon has been further exacerbated by the COVID-19 crisis. However, the predictors of student performance in blended courses are not yet clearly identified. How can we support student achievement when implementing a blended course? This question is studied in this thesis from the perspective of education and training sciences and, to some extent, social psychology. Thus, the ambition of this thesis is to highlight pedagogical components and motivational factors related to students' performance in blended settings, to propose concrete ways of action to educational agents. Through two systematic reviews (chapters 1 and 3) and an empirical study of 538 nursing students (chapter 4) three pedagogical levers were identified: the extensive use of available technologies, the presence of formative feedbacks and the combination of explicit and constructivist approaches. Motivational factors were then questioned and academic self-concept, achievement goals, self-determination theory (Chapter 6) and online participation were used. Three empirical studies (Chapters 7-9) identified two motivational levers: supporting a positive perception of students’ academic competence and engaging the intrinsic and autonomous quality of teaching and learning activities. In addition, the link between performance-approach goals and actual student performance is discussed with respect to the competitive dynamics present in nursing schools. Finally, several practical implications are proposed, perspectives for future work are presented, and an alliance between field and research is sought. [less ▲]

Detailed reference viewed: 105 (6 ULiège)
Full Text
See detailCentury-old biochar in temperate agroecosystems: role in nutrient cycling and organic matter stability in soils
Burgeon, Victor ULiege

Doctoral thesis (2021)

Natural earth-atmosphere carbon (C) fluxes have been disrupted by anthropogenic activities since the onset of the industrial revolution. Repeated scientific warnings to humanity regarding the consequences ... [more ▼]

Natural earth-atmosphere carbon (C) fluxes have been disrupted by anthropogenic activities since the onset of the industrial revolution. Repeated scientific warnings to humanity regarding the consequences of such imbalance have drawn the global population’s attention to the importance of limiting global warming to ensure the sustainability of ecosystems and livelihoods worldwide. Alongside a drastic drawdown of C emissions, carbon dioxide removal practices are needed. Among possible practices, the enhancement of soil organic carbon (SOC) stocks and in particular, the incorporation of charcoal in soils, thus known as biochar, holds great potential as a C sequestration tool and as a soil crop amendment. Number of studies have reported the agronomic benefits of biochar on the short term. However, precisely because of its persistence in soils which generally outlasts research parties, its long-term effects have seldom been addressed. Here, we focus on leftovers from charcoal production in hearths intended to meet pre-industrial fuel demands in Belgium and we use it as a proxy for 200-year-old biochar. Our aim is to address the long-term stability of biochar in soils and its potential co-benefits on biogeochemical functioning of agroecosystems. This manuscript presents our findings through an ascending spatial scale approach that deals with impacts of century-old biochar (CoBC): i) at the micrometer scale by focusing on organo-mineral interactions and the distribution of PyOM in the soil matrix (chapter 3), ii) at the meter scale, by addressing the vertical mobility of PyOM and century-old biochar effects on SOC stocks in the soil profile (chapter 4), iii) at the hectare scale, to determine the role of PyOM on nutrient cycles and crop performance (chapter 5) and finally iv) at the regional scale, where we compare the effects of PyOM on soil microbiology across soils differing in texture and land use (chapter 6). This work brings particular attention to the need for in-situ studies by focusing on a specific, thoroughly equipped observatory set-up in a farmland near Gembloux (Belgium). Three studied soils, defined as Luvisol, containing either century-old biochar (CoBC), recently amended young biochar (YBC) and finally a charcoal-free reference soils (REF) were compared. For the three soils and their three horizons (Ap: 0-30, E=30-60, Bt= 60-90 cm), five field replicates were analyzed and monitored. Yields and the elemental composition of winter wheat and chicory were monitored and analyzed. Soil temperature and volumetric water content as well as meteorological variables were continuously monitored over the study period (2018-2021). Suction cups were set up in the three soil horizons (20 cm, 45 cm, 80 cm) to monitor the pore water composition and its evolution continuously for 2 years. Samples of the topsoil (Ap) and subsoils (E) horizon underwent a soil fractionation protocol based on size and density to separate OM fractions displaying similar stabilization processes: the free light fraction (LF), the occluded LF and the mineral associated heavy fraction (HF). The elemental composition and thermal signature of bulk soil samples and fractions were analyzed to quantify and differentiate PyOM and non-PyOM. We show that CoBC soils store on average an additional 54 ± 25 tC ha-1 when compared to adjacent REF soils in the uppermost meter of soil. This increase in absolute C stocks is particularly marked in the topsoil horizon (Ap, 0-30 cm) but relatively larger in the subsoil (E, 30-60 cm) horizon in comparison to REF. This increase in C stocks is largely due to PyOM, which accounts for 35 ± 13 tC ha-1 (1 m profile), but not only as we provide evidence throughout the manuscript for an increase in non-PyOM accounting for between 6-16% of the additional carbon occurring in CoBC topsoils. The fractionation of soils highlighted the presence of charcoal in all particulate and mineral-associated fractions in both top and subsoil horizons. We show PyOM is strongly bound to mineral fractions and we discuss it as a means to promote PyOM stability in soils. Our results support the assumption that biochar functionalization promotes organo-mineral associations and OM inaccessibility to decomposers. We further provide evidence for a shift in the main C pool of subsoils whereby most PyOM occurs as particulate light fraction in CoBC subsoils as opposed to being mainly mineral-associated in REF soils. PyOM is also further stabilized through vertical migration, however, our analysis of dissolved organic matter (DOM) contents and optical properties did not provide evidence for PyOC dissolution. We suspect bioturbation to be a major process involved in the vertical mobility of PyOM. Our research also investigates the effect of biochar of contrasting ages on nutrient cycling in the soil-water-plant continuum of conventionally cropped agroecosystems. Here we provide field-based evidence that the effects of biochar evolve over its lifetime in soils. Indeed, recently amended biochar had a strong impact mainly on the soil pore water nutrient concentrations, resulting in decreased N-NO3- and K+ leaching out of the profile while increasing P-PO4- concentrations in the topsoil horizon. Century-old PyOM, on the other hand, had little impact on the pore water nutrient concentration but increased soil total N, plant available K+ and Ca2+ but decreased plant available P content. Overall, the presence of biochar in soils decreased the N, K+ and Ca2+ exports under the winter-wheat crop studied but had no significant effect on crop productivity. Overall, the work presented in this manuscript showed that beyond its stability as a metabolically unappealing source of OM for decomposers, CoBC is further stabilized through its interaction with surrounding soil constituents and its transfers to deeper soil horizons. Its persistence vouches for its potential as a carbon dioxide removal tool. Simultaneously, CoBC improves the accessibility of certain nutrients (N, K+, Ca2+) thus highlighting a high potential for improving nutrient use efficiency in agroecosystems. [less ▲]

Detailed reference viewed: 61 (14 ULiège)
Full Text
See detailSiting Strategies for Variable Renewable Generation Assets in Capacity Expansion Planning Frameworks
Radu, David-Constantin ULiege

Doctoral thesis (2021)

In the eve of a climate crisis generated by the sustained combustion of fossil fuels across various economic sectors, decarbonising worldwide power systems has been a cornerstone in reaching net-zero ... [more ▼]

In the eve of a climate crisis generated by the sustained combustion of fossil fuels across various economic sectors, decarbonising worldwide power systems has been a cornerstone in reaching net-zero targets in the upcoming decades. To this end, widely-available renewable energy sources (RES) such as solar irradiance or wind have been recently harnessed at scale in order to replace fossil-based generators in the electricity mix of power systems around the world. However, such resources are inherently variable on time scales ranging from minutes to years and integrating them in power systems typically complicates planning and operational procedures. Several solutions have been advocated to alleviate these issues, including the large-scale deployment of electricity storage systems or the implementation of demand response programs. Alternatively, since RES are heterogeneously-distributed in space and time, it has been suggested that siting RES electricity production assets so as to exploit this diversity may reduce the aggregate output variability of power plants as well as the residual electricity load (i.e., total load minus renewable production). The concept of renewable sources spatiotemporal complementarity formalises this idea and makes for the chief concept investigated in this thesis. The manuscript starts by revealing how connecting remote RES sites could lead to reduced probabilities of low-generation events. Then, a framework explicitly designed to assess the spatiotemporal complementarity between geographically dispersed RES assets is introduced and leveraged to devise optimisation models seeking to identify deployment patters with maximum complementarity among sites. Once an optimisation problem for siting RES assets based on complementarity criteria is made available, the value of spatiotemporal complementarity for power systems is assessed. Essentially, this is made possible via a multi-stage approach that works as follows. In the first stage, a highly-granular siting problem identifies a suitable set of sites where RES assets could be deployed according to a pre-specified criterion (e.g., spatiotemporal complementarity, output maximisation). In the second stage, the subset of previously identified sites is passed to a capacity expansion planning framework that sizes the power generation, transmission and storage assets that should be deployed and operated in order to satisfy pre-specified electricity demand levels at minimum cost. Furthermore, a third stage may also be leveraged should a more accurate estimation of the impact of different siting criteria on the operation of power systems is sought. This stage is formulated as a classical unit commitment and economic dispatch problem and, given the capacities of power generation, transmission and storage assets resulted from the second stage, provides a more detailed view on the daily operation of the power system assets. Finally, inspired by the workings of the aforementioned routine, a method to reduce the spatial dimension and decrease the computational burden of capacity expansion planning problems while preserving a detailed representation of RES assets is proposed. [less ▲]

Detailed reference viewed: 365 (14 ULiège)
Full Text
See detailTaxonomical, ecological and functional exploration of aquaponics microbiota in interaction with lettuce growth
Eck, Mathilde ULiege

Doctoral thesis (2021)

Aquaponics is emerging as an interesting alternative to decrease pressure on planetary resources and to limit the environmental impact of the food production systems. This new technique combines ... [more ▼]

Aquaponics is emerging as an interesting alternative to decrease pressure on planetary resources and to limit the environmental impact of the food production systems. This new technique combines hydroponics i.e. the soilless production of vegetables, with recirculating aquaculture in several types of systems fitted to various environments. Aquaponics, as implemented nowadays, is a fairly novel production system and requires a thorough inquiry of several aspects of its functioning to ensure its viability and reliability. One of these crucial features regards the characterisation of microbial communities and their roles in nutrient cycling. The objective of this thesis is thus to address this huge gap of knowledge regarding microorganisms in aquaponics via the description of the bacterial communities, the study of the potentially plant beneficial functions which could be carried on by the microbiota and their interaction with lettuce growth. In the first instance, this thesis focuses on the taxonomical description of the bacterial communities which can be found in various aquaponic and aquaculture systems and reports on the evolution of the different communities of one given system over nine weeks, using 16S rRNA gene sequencing. Results show that different systems harboured different microbiota although some common taxa could be found in all samples. It was also observed that within one system each compartment (sump, biofilter, plant roots) hosted specific microbiota and that those communities were relatively stable over time. Indeed, no adaptation period could be noted after the transplantation of seedlings into the system i.e. when the system previously functioning as a recirculating aquaculture system (RAS) was turned into a coupled aquaponic system - which is the main modification that the system underwent during the experiment. No modifications appeared either following the water parameters changes which naturally occur during the functioning of the system. As such it was concluded that the studied bacterial communities were resilient. Eventually, a taxonomic comparison between the lettuce root communities in the aquaponic system with literature regarding soil borne lettuce root communities showed intriguing similarities. This raises new questions regarding the origin of root microorganisms (i.e. seed or system) in aquaponics and its recruitment processes in soilless systems. However, the use of metabarcoding only provides an overview of the global composition of the communities down to the genus level. Genus identification does not permit to identify specific roles or functions linked with nutrient cycling and plant growth. Consequently, the second part of this thesis focuses directly on the functions present in aquaponics and their potential roles in plant health and care. In this view, 31 bacterial strains were isolated from the sump of the coupled aquaponic system of Gembloux Agro-Bio Tech. Five potentially plant beneficial traits were targeted in these bacteria via the use of in vitro biochemical tests: i) phosphorus and ii) potassium solubilisation and the production of iii) indole acetic acid, iv) siderophores and v) ammonia. Three of the most promising strains were then selected for a series of in vivo trials to assess their impact on lettuce growth in aquaponics. In these trials, three treatments were compared i.e. a mix of the three strains (AHT), one of the strains alone (T) and a control without any inoculation. The AHT bacterial mix treatment provided encouraging results fostering the production of lettuce leaves in light related and nutritive stress conditions while the T strain alone treatment also impacted lettuce growth in stressful conditions albeit in smaller proportions than AHT. An upscaling of the trials would now be required to confirm these observations. Overall, this thesis provided a first insight into bacterial communities in aquaponics and constitutes a stepping stone for more in depths research on the ecology of bacterial communities in aquaponics and their roles in interaction with crop growth. [less ▲]

Detailed reference viewed: 53 (13 ULiège)
Full Text
See detailLa 5-phosphatase de phosphoinositides INPP5K régule le développement précoce des lymphocytes B par le biais du contrôle de la structure et de la signalisation du récepteur à l'interleukine 7
Moes, Bastien ULiege

Doctoral thesis (2021)

INPP5K (Inositol polyphosphate 5-phosphatase K) or SKIP (Skeletal muscle and Kidney enriched Inositol Phosphatase) is an ubiquitously expressed enzyme which belongs to the phosphoinositide 5-phosphatase ... [more ▼]

INPP5K (Inositol polyphosphate 5-phosphatase K) or SKIP (Skeletal muscle and Kidney enriched Inositol Phosphatase) is an ubiquitously expressed enzyme which belongs to the phosphoinositide 5-phosphatase family. This enzyme hydrolyses both PtdIns(4,5)P2 and PtdIns(3,4,5)P3. Because of the lack of adequate biological tool, the function of Inpp5K in vivo is still poorly characterized,. Indeed, for still unknown reasons, Inpp5K total knock-out mice die during embryonical life at stage E10.5. Since we previously showed that INPP5K mRNA and protein are well expressed in lymphocytes, we generated and crossed Inpp5Kflox/flox mice with VAV-Cre mice, in order to obtain mice deficient for Inpp5K specifically in hematopoietic cells (VAV-CRE). Analysis of these VAV-CRE mice revealed a significant diminution of total B cells in blood, spleen and bone marrow, compared to controls mice. These alterations were associated with a nearly absence of antibody in the blood. Consequentlty, we have analysed early B cell development in bone marrow of VAV-CRE mice. The absence of INPP5K provokes a diversity of complex differences compared with control mice, including a partial blockade of this development between PrePro B (Fr.A) and Early Pro B (Fr.B) stages. These results were confirmed in Inpp5Kflox/flox MB1-CRE (MB1-CRE) where INPP5K is specifically deleted in B cells. To better understand the mechanism behind this partial blockade, the Interleukin 7 receptor (IL7R) pathway, which is essential for initiation and engagement of progenitor cells in the B cell lineage, has been analyzed in VAV-CRE and control mice. In VAV-CRE mice, these analyses revealed at PrePro B and Early Pro B stages a significant decrease in the phosphorylation of JAK1 and JAK3, two kinases that bind to the 2 IL7R chains, as well as of STAT5, their protein target, as compared with control mice. Downstream to STAT5 activation in the IL7R signaling, EBF1 and PAX5 expression was significantly decreased in VAV-CRE mice. This suggests that INPP5K plays an important during the early plasma membrane steps of IL7R activation. This hypothesis is reinforced by the observation of an increased membranous PtdIns(4,5)P2 level in bone marrow VAV-CRE B cells from PrePro B and Early Pro B stages. Confocal microscopy analysis demonstrated that INPP5K inactivation results in an altered formation of GM1+ microdomains which are known to be important for IL7R signaling. Moreover, indirect FRET analysis showed that the absence of INPP5K provokes significant alterations in IL7R dynamic structure both before and after IL7 stimulation. We indeed observed in VAV-CRE bone marrow B cells an increase in the distance between the two extracellular domains of the IL7R, an abnormal mobility of JAK1 and JAK3 kinases and a freeze of the distance between the cytoplasmic tail of IL7Rα chain and the plasma membrane, as compared with control B cells. [less ▲]

Detailed reference viewed: 38 (2 ULiège)
Full Text
See detailWork, mining, and neoliberalism: ethnography of Zambian mineworkers in the 21st century
Musonda, James ULiege

Doctoral thesis (2021)

On 1st April 2000, the Swiss multinational Copper trader Glencore successfully purchased two former Zambia Consolidated Copper Mines (ZCCM) assets, Nkana and Mufulira, and formed Mopani Copper Mines (MCM ... [more ▼]

On 1st April 2000, the Swiss multinational Copper trader Glencore successfully purchased two former Zambia Consolidated Copper Mines (ZCCM) assets, Nkana and Mufulira, and formed Mopani Copper Mines (MCM). Since then the company has drastically changed its labour policies in terms of: the promotion of safety culture among its workers; the withdrawal or reduction in social benefits given to workers; facilitating workers’ access to loans; persistent retrenchment of labor in line with fluctuations of global commodity prices; reduction in the number of direct employees who are replaced by a growing number of contract workers; and the employment of women miners (though still far fewer than men). How have these changes affected mineworkers’ subjectivity? This thesis responds to this question from three perspectives: protection (safety and loans); stability (retrenchments, and subcontracting); and gender and family dynamics. The thesis examines how Mopani Copper Mines, a Zambian company owned by the Swiss multinational company Glencore attempted to create Mopani subject— an easily controllable, responsible, dependent, vulnerable, and loyal employee through the various changes to the organisation of labour it has implemented since 2000. Drawing on a Foucaultian approach, the thesis shows however that the MCM’s corporate power only structured a “field of possibilities” inside which workers had more or less freedom. While the MCM policies influenced workers’ subjectivity, to a larger extent, workers’ subjectivity, the shimaini subject was a product of the workers own moral code or rules of conduct they assigned to themselves. This subjectivity manifests itself in a series of ways related to safety regimes and practices, indebtedness and credit, precarity and changing work trajectories, gender practices, and changes to family relations. It draws upon the ethnographic research I conducted on the Zambian Copperbelt between 2016 and 2019. I conducted this research in two former mine townships-Wusakile (in Kitwe) and Kankoyo (in Mufulira). It utilizes various approaches including: participant observation by working in two undergrounds as a helper and by observing miners in their homes and communities; over 150 interviews with miners, their families, managers, and union leaders; a simple survey; photographs; and a review of company and union data. [less ▲]

Detailed reference viewed: 34 (3 ULiège)
Full Text
See detailMicrogrid management with weather-based forecasting of energy generation, consumption and prices.
Dumas, Jonathan ULiege

Doctoral thesis (2021)

The decade 2009-2019 was particularly intense in rhetoric about efforts to tackle the climate crisis, such as the 2015 United Nations Climate Change Conference, COP 21. However, the carbon dioxide ... [more ▼]

The decade 2009-2019 was particularly intense in rhetoric about efforts to tackle the climate crisis, such as the 2015 United Nations Climate Change Conference, COP 21. However, the carbon dioxide emissions at the world scale increased constantly from 29.7 (GtCO2) in 2009 to 34.2 in 2019. The current gap between rhetoric and reality on emissions was and is still huge. The Intergovernmental Panel on Climate Change proposed different mitigation strategies to achieve the net emissions reductions that would be required to follow a pathway that limits global warming to 1.5°C with no or limited overshoot. There are still pathways to reach net-zero by 2050. Several reports propose detailed scenarios and strategies to achieve these targets. They remain narrow and highly challenging, requiring all stakeholders, governments, businesses, investors, and citizens to take action this year and every year after so that the goal does not slip out of reach. In most of these trajectories, electrification and an increased share of renewables are some of the key pillars. The transition towards a carbon-free society goes through an inevitable increase in the share of renewable generation in the energy mix and a drastic decrease in the total consumption of fossil fuels. In contrast to conventional power plants, renewable energy is subject to uncertainty. Most of the generation technologies based on renewable sources are non-dispatchable, and their production is stochastic and complex to predict in advance. A high share of renewables is challenging for power systems that have been designed and sized for dispatchable units. Therefore, this thesis studies the integration of renewables in power systems by investigating forecasting and decision-making tools. Since variable generation and electricity demand both fluctuate, they must be forecast ahead of time to inform real-time electricity scheduling and longer-term system planning. Better short-term forecasts enable system operators to reduce reliance on polluting standby plants and proactively manage increasing amounts of variable sources. Better long-term forecasts help system operators and investors to decide where and when to build variable plants. In this context, probabilistic forecasts, which aim at modeling the distribution of all possible future realizations, have become a vital tool to equip decision-makers, hopefully leading to better decisions in energy applications. When balancing electricity systems, system operators use scheduling and dispatch to determine how much power every controllable generator should produce. This process is slow and complex, governed by NP-hard optimization problems such as unit commitment and optimal power flow. Scheduling becomes even more complex as electricity systems include more storage, variable generators, and flexible demand. Thus, scheduling must improve significantly, allowing operators to rely on variable sources to manage systems. Therefore, stochastic or robust optimization strategies have been developed along with decomposition techniques to make the optimization problems tractable and efficient. These two challenges raise two central research questions studied in this thesis: (1) How to produce reliable probabilistic renewable generation forecasts, consumption, and electricity prices? (2) How to make decisions with uncertainty using probabilistic forecasts to improve scheduling? The thesis perimeter is the energy management of "small" systems such as microgrids at a residential scale on a day-ahead basis. The manuscript is divided into two main parts to propose directions to address both research questions: (1) a forecasting part; (2) a planning and control part. The forecasting part presents several techniques and strategies to produce and evaluate probabilistic forecasts. We provide the forecasting basics by introducing the different types of forecasts to characterize the behavior of stochastic variables, such as renewable generation, and the tools to assess the different types of forecasts. An example of forecast quality evaluation is given by assessing PV and electrical consumption point forecasts computed by standard deep-learning models such as recurrent neural networks. Then, the following Chapters investigate the quantile forecasts, scenarios, and density forecasts on several case studies. First, more advanced deep-learning models such as the encoder-decoder architecture produce PV quantile forecasts. Second, a density forecast-based approach computes probabilistic forecasts of imbalance prices on the Belgian case. Finally, a recent class of deep generative models, normalizing flows, generates renewable production and electrical consumption scenarios. Using an energy retailer case study, this technique is extensively compared to state-of-the-art generative models, the variational autoencoders and generative adversarial networks. The planning and control part proposes approaches and methodologies based on optimization for decision-making under uncertainty using probabilistic forecasts on several case studies. We introduce the basics of decision-making under uncertainty using optimization strategies: stochastic programming and robust optimization. Then, we investigate these strategies in several case studies in the following Chapters. First, we propose a value function-based approach to propagate information from operational planning to real-time optimization in a deterministic framework. Second, three Chapters focus on the energy management of a grid-connected renewable generation plant coupled with a battery energy storage device in the capacity firming market. This framework promotes renewable power generation facilities in small non-interconnected grids. The day-ahead planning of the system uses either a stochastic or a robust approach. Furthermore, a sizing methodology of the system is proposed. Finally, we consider the day-ahead market scheduling of an energy retailer to evaluate the forecast value of the deep learning generative models introduced in the forecasting part. (1) Forecasting techniques of the future. The development of new machine learning models that take advantage of the underlying physical process opens a new way of research. For instance, new forecasting techniques that take advantage of the power system characteristics, such as the graphical normalizing flows capable of learning the power network structure, could be applied to hierarchical forecasting. (2) Machine learning for optimization. Models that simplify optimization planning problems by learning a sub-optimal space. For instance, a deep learning model can partially learn the sizing space to provide a fast and efficient tool. A neural network can also emulate the behavior of a physics solver that solves electricity differential equations to compute electricity flow in power grids. Furthermore, such proxies could evaluate if a given operation planning decision would lead to acceptable trajectories where the reliability criterion is met in real-time. (3) Modelling and simulation of energy systems. New flexible and open-source optimization modeling tools are required to capture the growing complexity of such future energy systems. To this end, in the past few years, several open-source models for the strategic energy planning of urban and regional energy systems have been developed. EnergyScope TD and E4CLIM are two of them where we think it may be relevant to implement and test the forecasting techniques and scheduling strategies developed in this thesis. (4) Psychology and machine learning. Achieving sustainability goals requires as much the use of relevant technology as psychology. Therefore, one of the main challenges is not designing relevant technological tools but changing how we consume and behave in our society. Thus, machine learning and psychology could help to identify appropriate behaviors to reduce carbon footprint. Then, inform individuals, and provide constructive opportunities by modeling individual behavior. [less ▲]

Detailed reference viewed: 403 (61 ULiège)
Full Text
See detailDevelopment of artificial black soldier fly (Hermetia illucens (L.1758)) rearing from agricultural by-products to produce aquaculture feed ingredients
Hoc, Bertrand ULiege

Doctoral thesis (2021)

Worldwide fish demand for food market continuously increases while fishery resources reached a ceiling in the 1990s and wild fish stocks are subject to increasing pressure which endangers them. Therefore ... [more ▼]

Worldwide fish demand for food market continuously increases while fishery resources reached a ceiling in the 1990s and wild fish stocks are subject to increasing pressure which endangers them. Therefore, aquaculture continues to develop as an alternative to contribute to the global fish production. Nevertheless, this production sector requires large quantities of feed ingredients for fish species that are mostly carnivorous and require large amounts of proteins and lipids. Feed sources for the fish farm largely rely on industrial fisheries whose stocks are limited and already overexploited. In this context, a diversification of nutritional resources must be considered in order to perpetuate the sector development and ensure its sustainability. Vegetable meals inclusion in fish feed has already made it possible to substitute a significant part of the fishing resources. Nevertheless, their nutritional profiles do not meet all the requirements of most fish species, which limits their inclusion rate in fish feed. Insects present a new source of proteins and lipids that could be produced locally to feed farmed fish. Compared to conventional farms, they require less space, consume less water and have a high conversion rate, especially for organic waste. Among potential species, the black soldier fly (Hermetia illucens L. 1758- Black Soldier Fly - BSF) is a prime candidate because of its rapid production cycle, its voracity for a wide range of organic matter and its amino acid profile, making it an excellent substitute for fish meal. Its fatty acid profile characterized by a high level of saturated fatty acid (SFA) will be the limiting factor for its inclusion in fish feed. The production of this new fish feed ingredient is still in its infancy and the BSF zootechnical data, as well as the impacts of its nutritional composition on fish feed, are still limited. In this context, this thesis research focused on the prepupae production of BSF through the valorization of agricultural by-products and their inclusion in rainbow trout (Oncorhynchus mykiss Walbaum 1792) feed. The first experimental axis of this work focuses on the development of the BSF rearing in a controlled environment. Based on the natural behaviors of the species, specific rearing methods and infrastructures for each stage of its life cycle (reproduction, egg incubation, larval pre-fattening, larval fattening and prepupae self-collection) have been developed. This research has led to the setting up of a mass production unit of BSF larvae and prepupae in a converted transport container. A particular emphasis was put on the BSF artificial reproduction, the most sensitive rearing phase. Breeding experiments were conducted to evaluate the impact of sex-ratio and density of broodstock as well as variation in the nycthemeral cycle on breeding effort. In order to carry out these experiments, a broodstock selection model and an oviposition system were first developed. Sexing of imago populations resulting from prepupae mass production revealed sexual growth dimorphism, wherein males exhibit faster growth. These observations allowed us to establish a selection of broodstock populations according to their sex-ratio based on their progressive self-collection at the prepupal stage. The oviposition device consisting of artificial supports placed on an attraction system has allowed to centralize the ovipositions within the breeding cages in order to collect and quantify egg production. This research has shown that a population with a dominant female sex-ratio should be favored from a density of 6500 individuals/m³ and that a daily light duration of minimum 6h should be applied to maintain the reproduction. The compilation of the results obtained allowed the development of an efficient method of BSF reproduction in a controlled environment. The second experimental axis of this work focuses on the modulation of the BSF prepupae fatty acid profile through larval feeding. The objective of this research was to evaluate the potential of modulating the prepupae fatty acid profile by enriching diets with available agricultural by-products and to determine the limits of these modulations through the lipid metabolism that conditions them. Two larval nutrition experiments consisting of the enrichment of diets by the progressive incorporation of oilseed cakes and the substitution of water brought to diets by heavy water (D2O) were successively carried out. The diets enrichment has partially balanced the prepupae fatty acid profiles by decreasing their SFA contents and increasing their unsaturated fatty acid (USFA) contents. The D2O diet inclusion led to a mass labelling of the biosynthesized fatty acids by the deuterium atoms incorporation highlighting the limited modulation of fatty acid profiles due to high levels of neosynthesized SFAs, the inability of larvae to synthesize α-linolenic acid (ALA: C18:3n3) targeted by diet enrichments, and the underestimation of the involvement of carbohydrates in larvae fatty acid synthesis. A scheme of the fatty acid synthesis pathways has been established and will require further research to confirm the identification of the key enzymes involved. The third experimental axis of this work focuses on the inclusion of BSF prepupae meals in the diets of rainbow trout. The objective of this research was to evaluate the impact of this inclusion on the trout growth performance and on the proximal compositions and fatty acid profiles of their fillets. Through the experiments conducted, the entire production cycle of BSF-based trout feed was studied (insect production and processing, feed formulation and extrusion, and fish nutrition trial). These experiments validated the applicability of the BSF rearing methods developed which led to the prepupae mass production with differentiated fatty acid profiles from plant by-products. The inclusion of prepupae meals in trout diets did not modify the proximal composition of trout fillets but modified their fatty acid profile and decreased their growth. These results show the limitations of the prepupae fatty acid profiles obtained by the valorization of plant by-products to maintain the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the trout fillets. Regarding the decrease in trout growth, the amino acid profile, chitin content and SFA content of BSF-based trout feed have been incriminated and it is reasonable to suppose that these three factors could have influenced trout growth concomitantly. Different ways to improve the prepupae meal nutritional quality through methods of fatty acid profile enrichment and processing of prepupae are suggested. The research carried out during this study has allowed the exploration of different areas of this new model of feed ingredients production. The results obtained highlight several potentialities and limits of application of this new resource. They constitute a basis of reflection to allow the development of this new sector of activity. [less ▲]

Detailed reference viewed: 128 (24 ULiège)
Full Text
See detailLes dynamiques interrégionales afro-sud-américaines dans l'Atlantique Sud: entre "Communauté de destins" et enjeux stratégiques. Cas de la ZOPACAS et de l'ASA.
Mvengou Cruzmerino, Martine Colette ULiege

Doctoral thesis (2021)

Le présent travail a abordé le phénomène interrégional à partir d’une perspective Sud-Sud et a questionné les enjeux stratégiques et les dimensions cognitives qui structurent lesdites dynamiques ... [more ▼]

Le présent travail a abordé le phénomène interrégional à partir d’une perspective Sud-Sud et a questionné les enjeux stratégiques et les dimensions cognitives qui structurent lesdites dynamiques interrégionales. En abordant le cas du dialogue entre l’Afrique et l’Amérique du Sud, l’analyse s’est concentrée sur deux études de cas : la Zone de Paix et de Coopération dans l’Atlantique Sud (ZOPACAS), et le Forum de Coopération Amérique du Sud-Afrique (ASA). Cette thèse a mis en lumière les intérêts politiques et sécuritaires collectifs et individuels autour de l’Atlantique Sud, et a identifié des dynamiques de circulation idéelles au sein de ces deux espaces de dialogue afro-sud-américains. A partir de la consultation d’archives, d’entretiens et de l’analyse de discours, cette recherche a proposé de nouvelles pistes d’analyse pour l’étude des initiatives interrégionales issues du Sud. [less ▲]

Detailed reference viewed: 32 (5 ULiège)
Full Text
See detailIdentification of a new role for the ERG transcription factor in the regulation of pre-mRNA alternative splicing through its collaboration with RBFOX2
Guedri, Katia ULiege

Doctoral thesis (2021)

Transcription factors (TFs) are usually defined as sequence-specific DNA-binding proteins that control transcription as a first step of gene expression. However, more and more evidence indicates that they ... [more ▼]

Transcription factors (TFs) are usually defined as sequence-specific DNA-binding proteins that control transcription as a first step of gene expression. However, more and more evidence indicates that they are also involved in the regulation of posttranscriptional steps, in particular the splicing process. In our laboratory, we previously demonstrated that ERG protein, a member of Ets TFs has a role in the regulation of decay [1], a downstream mRNA processing event. In addition, it was suggested that TFs act directly on splicing through different mechanisms, such as by modifying RNA polymerase II elongation rates and altering the kinetics of exposure of splice sites, by the recruitment of transcriptional coactivators involved in splicing, or through the modulation of direct splicing factors expression. However, currently it was proposed that some TFs can control alternative splicing (AS) directly through their binding onto pre-mRNA, thus controlling AS via an unknown but direct mechanism [2]. In this work, we hypothesized that ERG TF can regulate AS process and this can be affected in cancers such as Ewing’s sarcoma (EwS). Thus, we reported for the first time that ERG can regulate AS of numerous splicing targets. This is probably by a direct mechanism. Indeed, first we showed that ERG associates with spliceosomal components, it is found on nascent pre-mRNA and induces AS through its CTAD domain, by inclusion or exclusion of an alternative exon when it is recruited onto a reporter. Second, transcriptomic analysis demonstrated that depletion of ERG affects a large number of AS events, mainly cassette exons, in a tissue-specific manner. Third, we observed that sequences of ERG-regulated cassette exons and their 200 adjacent intronic base pairs are enriched in binding motifs for RBFOX2, a tissue-specific splicing regulator and an important functional interactor of the LASR splicing complex. We demonstrated that ERG and RBFOX2 interact via their CTAD and C-terminal domains respectively, and both proteins collaborate to regulate a large set of cassette exons. Finally, our observations suggested that the splicing function of ERG is independent of its DNA-binding and transcriptional activity since we did not find any significant overlap between differentially expressed and differentially spliced genes in ERG-depleted cells, and a transcriptionally inactive ERG variant lacking the DNA-binding domain (ERG-ETS) presented full splicing activity in our reporter assay. Perturbation of the splicing program is a feature of EwS. This was previously attributed to the presence of FET-Ets fusions [3] and the splicing function of EWS-FLI1 was only attributed to its EWS moiety. In addition, the functional relevance of EWS-FLI1 in the EwS oncogenic process is still unknown. We have studied the role of the EWS-FLI1 fusion in the reporter assay and observed that its AS function is linked to its recruitment onto the reporter mRNA. In addition, our observations suggested that the FLI1-derived moiety can also be a major contributor to the fusion protein’s splicing function in EwS and that EWS-FLI1 also interacts with RFBOX2, suggesting that the EWS-FLI1 and RFBOX2 interaction could play a major role in EwS development. Altogether, our results support a model in which the ERG protein controls AS processes beyond its role as a TF. This new function of ERG in AS regulation should be considered for future cancer therapies. [less ▲]

Detailed reference viewed: 41 (2 ULiège)
Full Text
See detailAdapting, implementing, and evaluating the effects of a comprehensive school reform program: the case of School-Wide Positive Behavior Interventions and Supports in French-speaking Belgium
Deltour, Caroline ULiege

Doctoral thesis (2021)

This dissertation aimed at examining the adaptation, implementation, and evaluation of a comprehensive school reform in French-speaking Belgium, that is School-Wide Positive Behavior Interventions and ... [more ▼]

This dissertation aimed at examining the adaptation, implementation, and evaluation of a comprehensive school reform in French-speaking Belgium, that is School-Wide Positive Behavior Interventions and Supports (SWPBIS). The general introduction points out the importance of school climate and the role of teachers’ collective efficacy based on results from international surveys and on the literature. The research context and SWPBIS are presented, before introducing the research project, its objectives, and the hypotheses. The introduction closes on an overview of the dissertation. The five articles introduce the results of the five conducted studies. The first one is a systematical and critical review of the existing literature concerning SWPBIS, its implementation and numerous outcomes. The second article is a comparison of SWPBIS implementation in three French-speaking contexts. This exploratory study’s goals were to highlight the similarities and differences between the implementation in the three contexts and to analyze the unmissable facilitating factors that anyone interested in implementing SWPBIS should be aware of. The third article is the result of cross-cultural study on school climate and mental health in teenagers. The study aimed at cross-culturally validating a school-climate survey and investigating the relation between school climate and mental health for secondary school students. The fourth article presents the results of the cultural adaptation of SWPBIS to the school context of French-speaking Belgium and the outcomes of SWPBIS implementation on school climate for all stakeholders: staff members, students, and parents. Results concerning the impact of SWPBIS implementation on tardiness and absenteeism are also presented. The fifth article examines the outcomes of SWPBIS implementation on teachers’ collective efficacy. The five articles are followed by a general discussion in which the initial hypotheses are confronted to the results of the five conducted studies. Then, the discussion takes additional arguments, mainly linked to the sustainability of the system and its outcomes, into consideration. The school-wide characteristic of the program, the implementation fidelity, the importance of data-based decision-making and the impact SWPBIS implementation can have on students’ SES background are developed. [less ▲]

Detailed reference viewed: 155 (10 ULiège)
Full Text
See detailCreating highly entangled states with ultracolds bosonic atoms through resonance- and chaos-assisted tunneling
Vanhaele, Guillaume ULiege

Doctoral thesis (2021)

The present dissertation theoretically investigates the generation of entangled states with ultracold bosonic atoms. Specifically, that focuses on the NOON states in a double-well potential, which are the ... [more ▼]

The present dissertation theoretically investigates the generation of entangled states with ultracold bosonic atoms. Specifically, that focuses on the NOON states in a double-well potential, which are the coherent and equivalent superposition of |N,0> and |0,N> with $N$ atoms, and on the triple-NOON states in a three-site optical trap, which are the coherent and equivalent superposition of |N,0,0>, |0,N,0> and |0,0,N>. These states can be seen as large manifestations of entanglement. The collective tunneling in the self-trapping regime is made possible by the atom-atom interactions. For example, the NOON state is formed after half the tunneling time, i.e. the time needed to obtain a total transfer of population to the other site. The main message of this dissertation is that the timescale required to generate this transition can be considerably reduced by means of an external periodic driving without qualitatively altering the quantum dynamics. Moreover, indications of this speedup are available in the corresponding classical phase space. The presence of nonlinear resonances at the classical level induces perturbative couplings at the quantum level. The subsequent reorganization of the eigenspectrum enables one to explain the modifications of the tunneling time. These modifications can also be produced by prominent chaotic layer known to welcome strongly connected states. Built upon the phase space features, resonance- and chaos-assisted tunneling is a semiclassical theory which can be used as a guideline in the quest of suitable parameters. [less ▲]

Detailed reference viewed: 57 (13 ULiège)
Full Text
See detailConfiguring the field of philanthropy in the age of social-mission platforms: A story of fragmented structuration and divergent boundary work
Dessy, Elodie ULiege

Doctoral thesis (2021)

At the junction of private and public spheres, philanthropy is a social phenomenon open to controversies. That which constitutes giving private resources for public purposes evolves alongside societal ... [more ▼]

At the junction of private and public spheres, philanthropy is a social phenomenon open to controversies. That which constitutes giving private resources for public purposes evolves alongside societal developments. Philanthropy can be regarded as an issue field – that is, forming around the contested issue of what giving means and how to give. Given this issue-based nature and following digital evolutions, platform-based newcomers (i.e., social crowdfunding, -timing, and -sourcing platforms) have emerged at the fringes of philanthropy. This dissertation explores the configuration of philanthropy in this age of social-mission platforms. It focuses on the Belgian field of philanthropy. One feature of Belgian philanthropy is its fragmented infrastructure. The field lacks the meaning, operational and relational mechanisms to guide philanthropic organizations’ action and interaction. As a result, when facing newcomers, incumbent organizations did not offer a united front. This phenomenon is investigated through three papers. Considering the field infrastructure, the first paper documents field-structuring strategies and the unique role of “field-structuring actor”. Using a case-based approach, the second paper develops a typology of social-mission platforms. Finally, the third paper examines the relationship between incumbents and newcomers, and emphasizes in- population heterogeneity in boundary strategies. Overall, the dissertation contributes to both institutional theory, by explaining how divergent boundary work leads to a process of persistent, purposeful, and productive fragmented structuration, as well as to philanthropy studies, by documenting the heterogeneity of philanthropic organizations and the development of social-mission platforms. [less ▲]

Detailed reference viewed: 69 (14 ULiège)
Full Text
See detailEstimation des rendements du Maïs (Zea mays) et du Sorgho (Sorghum bicolor) à l’échelle de la parcelle et de la région agricole par assimilation de données de télédétection dans le modèle AquaCrop
Mohamed Sallah, Abdoul-Hamid ULiege

Doctoral thesis (2021)

In a context of climate change that directly affects agricultural production, yield estimation is of great importance regarding economic, geopolitical and food security issues. Traditionally carried out ... [more ▼]

In a context of climate change that directly affects agricultural production, yield estimation is of great importance regarding economic, geopolitical and food security issues. Traditionally carried out through agricultural costly and time-consuming surveys, yield estimation can be improved with crop growth models combined with Earth observation data. This research focuses on the implementation of an operational system to assimilate biophysical variables obtained from high spatial and temporal resolution satellite data into the AquaCrop model to estimate total biomass for maize and sorghum. First, the biophysical variable of interest, canopy cover, derived from satellite data was validated at the field scale with measured data obtained from digital hemispherical photography. The canopy cover parameters derived from the satellite time series – maximum canopy cover and emergence date – were assimilated into the AquaCrop model for better calibration and validation toward a limited number of maize fields in Belgium. The performance of the method allowed, in a second step, to estimate the total biomass of all the maize fields in the country using a crop mask and plot-specific data. To make the results available at the scale of the agricultural region, data aggregation was performed. This approach resulted in a satisfactory estimate of yields at the scale of the agricultural region. The approach was also tested in a semi-arid context and under weedy crop management in Niger for sorghum. It also provided interesting results both with reference data (measured) and with open access data. This research provides a framework for operationalizing yield estimation at the agricultural region scale using plot-specific information and the AquaCrop model. [less ▲]

Detailed reference viewed: 51 (6 ULiège)
Full Text
See detailInvestigation of innovative analytical techniques and methodological approaches for the analysis of phyto-cannabinoids in cannabis samples
Deidda, Riccardo ULiege

Doctoral thesis (2021)

Cannabis has now been the center of scientific attention for several years. Indeed, since its pharmacological potential was rediscovered in the 2000s, this plant has become a major subject in research ... [more ▼]

Cannabis has now been the center of scientific attention for several years. Indeed, since its pharmacological potential was rediscovered in the 2000s, this plant has become a major subject in research laboratories, leading to the publication of countless scientific works. In the field of analytical chemistry, various methods of analyzing cannabinoids in cannabis samples have been published. For this purpose, various techniques have been applied, but liquid and gas chromatography are undoubtedly the most used. However, in recent years, other techniques, equally interesting from the point of view of analytical performance, have been successfully implemented in analytical laboratories. This thesis project aims to investigate the potential of rapidly developing techniques for the analysis of cannabinoids in cannabis samples. In particular, two techniques were involved in the research discussed in this thesis: near-infrared spectroscopy (NIR) and supercritical fluid chromatography (SFC). These two techniques have been identified as particularly promising. NIR spectroscopy allows samples to be analyzed quickly and directly in their original form. Indeed, the preparation of samples is most often not required by the technique, representing a considerable advantage in terms of time but also economic. In addition, the components of the spectrophotometer can be miniaturized, an aspect that has enabled the development of portable spectrophotometers, which offer the possibility of carrying out analyses directly in the field. This possibility was therefore studied in the specific case of the analysis of cannabis samples to determine their ∆9-tetrahydrocannabinol (THC) content. Two portable spectrophotometers with different technical characteristics were tested first on cannabis inflorescences and then on resins in order to choose the most suitable device for this type of analysis. The results obtained during this preliminary study demonstrated the applicability of portable NIR spectroscopy for the quantitative analysis of THC in cannabis samples, without any preparation process. In the case of SFC, this analytical technique can be considered as an evolution of liquid chromatography, with several advantages over the latter. Indeed, if the analytical performance in terms of efficiency is comparable to that of ultra-high-performance liquid chromatography (UHPLC), the use of organic solvents and analysis times can be drastically reduced, depending on the operating conditions chosen. During this thesis, an SFC-UV method was developed and applied to the quantitative analysis of five cannabinoids on 92 real cannabis samples, with the aim of evaluating the quantitative potential of this technique. The results were then compared with those obtained using a reference method based on UHPLC-UV. The Bland-Altman statistical method was then applied and the “difference plots” confirmed the concordance of the results obtained with both techniques, thus demonstrating the equivalence of SFC for the analysis of cannabinoids. In addition to the technological advances in cannabinoid analysis, this thesis project also covered the methodological aspects of the development of analytical methods. Indeed, the principles of "analytical quality by design" (AQbD) have been deepened by means of a review of its applications for pharmaceutical quality control, presented by the scientific literature. This approach, based on a thorough investigation of operational parameters, allows the development of robust and efficient analytical methods. Operational choices are made through statistical evaluations, which allow the identification and optimization of critical methodological parameters for certain quality attributes of the analytical method under development. The result of this approach is a “method operable design region”, consisting in a multidimensional region exhibiting a series of operating conditions, which allow to satisfy the quality requirements of the method, with a known probability. Within this multidimensional space, which can be seen as a robustness space, the operational parameters of the method can be selected. In this context, this innovative approach was evaluated by means of two scientific papers. The first concerned the optimization of an analytical method based on liquid chromatography for monitoring THC concentrations in oily cannabis extracts. This work made it possible to apply this strategy and to study its advantages closely. The second work focused on the application of this strategy to an unusual and innovative analytical technique: surface enhanced Raman scattering (SERS). Indeed, the scientific literature shows a wide application of AQbD for the development of methods based on separation techniques, such as capillary electrophoresis and liquid chromatography for example. However, their application to analytical methods based on spectroscopic techniques is insufficiently described. For these reasons, in the last part of this work, the AQbD approach was applied, for the first time, to SERS, which is gradually spreading in analytical laboratories. [less ▲]

Detailed reference viewed: 69 (7 ULiège)
Full Text
See detailUAV-based remote sensing for high spatio-temporal monitoring of century-old biochar effects on crop performance
Heidarian Dehkordi, Ramin ULiege

Doctoral thesis (2021)

Biochar, the solid carbon-rich residue of biomass pyrolysis, has been widely promoted in the context of climate-smart agriculture to improve soil nutrient availability, soil acidity, and water holding ... [more ▼]

Biochar, the solid carbon-rich residue of biomass pyrolysis, has been widely promoted in the context of climate-smart agriculture to improve soil nutrient availability, soil acidity, and water holding capacity. The aforementioned biochar impacts on soil quality can, in turn, affect nutrient uptake and crop productivity. Although numerous studies have explored short-term biochar effects on soil-plant system, there exists a general lack of researches investigating the long-term effects. As such, this project (CHAR-ARC) aims to evaluate the effects of century-old biochar (aged in agricultural soils more than 150 years ago) on soil-plant interactions within three different work packages. The first and second work packages study century-old biochar effects on nutrient cycling and water dynamics, respectively. The third work package (this thesis) investigates century-old biochar effects on crop dynamics using remote sensing images allowing for a high spatio-temporal monitoring thorough the entire cropping seasons. The study site is an agricultural field near Isnes (NW corner: 50°31′N 4°44′E; SE corner: 50°31′N 4°45′E) in central Belgium. The field was predominantly covered with oak, hornbeam, beech, and hazel forests and had been turned into cropland since the eighteenth century resulting in eleven biochar patches within the site. The soil type is Luvisol with a silt loam texture in the topsoil. Soil organic carbon and total nitrogen concentrations were determined following a regular sampling scheme by dry combustion using the Leco TruMac element analyser. High-resolution remotely-sensed images captured by unmanned aerial vehicles (UAVs) were deployed (a total of 27 UAV flights) to monitor crop performance across the century-old biochar patches in comparison to their adjacent reference soil patches. Red-Green-Blue (RGB) dataset was acquired using a DJI Phantom 4 Pro. Multispectral and thermal datasets were collected RedEdge-M and FLIR Vue Pro Radiometric sensors respectively, on boar of a DJI Matrice 100. In Chapter 2, high-resolution UAV images were deployed to monitor chicory crop growth across the century-old biochar patches in comparison to their adjacent reference soil patches over the 2018 cropping season. Chicory canopy cover was retrieved from the RGB sensor as the ratio of the pixels covered by vegetation to the total number of ground pixels over the 2018 cropping season. Statistical paired t-test indicated a significant positive impact of century-old biochar on chicory crop growth during the green-up phase. This was corroborated with greater chicory leaf lengths across the biochar patches measured in the field. In addition, chicory crop water stress was retrieved as the difference between the canopy temperature (derived from the thermal images) and the air temperature (recorded by the on-site weather station). Moreover, the topographical wetness index (TWI) was computed to mitigate the impact of topography on the calculated crop water stress. Interestingly, TWI exhibited a positive relationship with soil organic carbon. Moreover, our results indicated an increase in chicory crop water stress across century-old biochar patches. Lastly, no impact of biochar was observed on the harvested plant biophysical parameters such as chicory yield, root length, or perimeter. The latter underlined the computed chicory canopy cover curves in which no particular impact of biochar was observed at the end of the growing season. In Chapter 3, winter wheat performance was evaluated using RGB and multispectral images throughout the 2019 cropping season. As such, monitoring winter wheat crop growth and health provided new insights into the alteration in winter wheat crop dynamics at the canopy level associated with century-old biochar presence. Similar to the results of chicory season, a significant positive impact of biochar on the evolution of winter wheat canopy cover was illustrated using the RGB images. Furthermore, winter wheat plant height was computed based on the RGB images by subtracting the digital terrain model from the digital surface model (following the necessary calibration chain). The remotely-sensed winter wheat plant height was slightly higher across the century-old biochar patches. In addition, a total of eight vegetation indices were computed based on the multispectral dataset. Though the contrast between biochar and reference plots was not thoroughly the same for all the vegetation indices, several indices such as optimized soil adjusted vegetation index (OSAVI) highlighted a significantly better winter wheat crop development at the beginning of the growing season. There was however no particular impact of biochar on crop spectral status towards the end of the season. Crop health maps were also computed based on the RGB and multispectral images using principal component analysis and k-means clustering. Both RGB and multispectral crop health maps (comprising a clustering agreement of 74.82%) indicated a better winter wheat crop health across the biochar plots. There was also a significant positive impact of biochar on crop growth stages measured in the field. Finally, the plausible relationship between the multispectral vegetation indices and the harvested crop yield was tested. Simplified canopy chlorophyll content index (s-CCI) and normalized difference red edge index (NDRE) were found to be good linear estimators of harvested crop yield. s-CCI was then used to predict a harvested crop yield map for the entire study field. The predicted crop yield showed no remarkable influence of biochar on winter wheat harvested crop yield. In Chapter 4, the potential of high-resolution UAV images to monitor plant diseases, and the plausible link between century-old biochar and plant diseases (as raised in generated crop health maps in Chapter 3) was specifically investigated. For this, UAV-based RGB images were first acquired across four winter wheat fields in the Grand Duchy of Luxembourg. At the same time, the percentage of the diseased leaf areas in terms of wheat stripe rust (WSR) and wheat leaf rust (WLR) were visually observed in the field. Then, WSR and WLR severities were determined from the acquired RGB images through additive or subtractive models in visual cryptography. As such, digital numbers (DNs) of green and red spectral bands were used to determine WSR. In addition, the combination of DNs of green, red, and blue spectral bands was used to identify WLR. The results indicated a strong correlation between UAV imagery and in-field observations for the determination of WSR, WLR, and canopy cover for winter wheat crop. The identified indices were then applied across the CHAR study site in Gembloux. The estimated WSR severity was 35.7% on average for the biochar plot in comparison to an average of 42.3% in the reference plots. For WLR severity, there was an average of 22.8% in the biochar plots versus 26.4% in the reference plots. These results were in apparent agreement with the identified crop health percentages in Chapter 3 as a function of century-old biochar enrichment. Furthermore, WSR and WLR showed notable alterations in winter wheat typical reflectance spectra, mostly between the green and red spectral bands, in both RGB and multispectral images available across the study site in Gembloux. This finding may pave the way for future researches developing more robust remote sensing indices to monitor fungal foliar diseases. In Chapter 5, the capability of fusing remotely-sensed UAV and Landsat-8 images allowing for a high spatio-temporal monitoring of century-old biochar effects on evapotranspiration over the cropping season was explored. The fusion of UAV and Landsat-8 images was performed using additive wavelet transform (AWT), generating sharpened Landsat-8 images with the high spatial resolution as the UAV images. AWT sharpened Landsat-8 images were spatially well-correlated with coarse resolution images, and were well-preserved the spatial details. Surface albedo and normalized difference vegetation index (NDVI) were computed based on reflectance spectra of UAV and Landsat-8 multispectral sensors. We retrieved surface temperature images from FLIR Vue Pro R on board of UAV and Landsat-8 brightness temperature images respectively based on reference ground-based thermal panels and temperature emissivity separation algorithm. The fused images and the meteorological data were used as inputs in the ETLook which is a surface energy balance model based on the Penman-Monteith approach. As such, ETLook model provided high spatio-temporal maps of actual evapotranspiration across the field throughout the 2019 cropping season. The results showed a significant decrease in surface albedo across the biochar plots during the early development stages of winter wheat. Moreover, biochar significantly caused an earlier greening up of wheat plants, and also, stimulated the development of wheat canopies towards the middle of the cropping season. There were however no impacts at the end of the season due to dense wheat canopies covering the aggravated dark colour soil across the biochar patches. Surface temperature was not affected by biochar either at the beginning or towards the end of the season. Neither was there any impact of biochar on actual evapotranspiration over the season. The implemented approach may also develop robust techniques for image fusion of UAV and satellite images to better meet the necessities of the precision agriculture. [less ▲]

Detailed reference viewed: 147 (27 ULiège)
Full Text
See detailInvestigating microbial lipopeptides with novel mass spectrometry tools
Mc Cann, Andréa ULiege

Doctoral thesis (2021)

Lipopeptides (LPs) are produced by microorganisms and are composed by a hydrophilic peptide ring connected to a hydrophobic lipid tail. The remarkable diversity in the lipopeptide structure confers the ... [more ▼]

Lipopeptides (LPs) are produced by microorganisms and are composed by a hydrophilic peptide ring connected to a hydrophobic lipid tail. The remarkable diversity in the lipopeptide structure confers the LPs class a large range of biological properties. In today’s approach for lipopeptide screening, newly Identified lipopeptides by in Silico or In Vivo methods are generally produced and purified before their characterization by HPLC-MS/MS. If mass spectrometry has been used so far as a tool to confirm the mass of a compound, we will show in this thesis that there are many other MS based tools, from ion mobility to mass spectrometry imaging, capable of both lipopeptide screening and identification, even in challenging conditions such as natural environment mimicking conditions. The first part of this thesis will focus on the development of mass spectrometry imaging tools by providing semi-targeted approaches for lipopeptide detection and localization, based on Kendrick mass defect. Mass shift associated with complex samples will also be discussed. The second part of this manuscript will highlight the benefit of mass spectrometry ion mobility for lipopeptide identification, and the possible structural information on lipopeptides that can be extracted from the ion mobility data. [less ▲]

Detailed reference viewed: 46 (12 ULiège)
Full Text
See detailCharacterization of the regenerated Insulin-producing cells following pancreatic β-cell destruction in zebrafish
Carril Pardo, Claudio Andrès ULiege

Doctoral thesis (2021)

Restoring damaged β-cells in diabetic patients by harnessing the plasticity of other pancreatic cells raises the questions of the efficiency of the process and of the functionality of the new Insulin ... [more ▼]

Restoring damaged β-cells in diabetic patients by harnessing the plasticity of other pancreatic cells raises the questions of the efficiency of the process and of the functionality of the new Insulin-expressing cells. To overcome the weak regenerative capacity of mammals, we used regeneration-prone zebrafish to study β-cells arising following destruction. We show that most new insulin cells differ from the original β- cells as they are Somatostatin+ Insulin+, but are nevertheless functional and normalize glycemia. These bi-hormonal cells are transcriptionally close to a subset of δ-cells in normal islets characterized by the expression of somatostatin 1.1 (sst1.1), the β-cell genes pdx1, slc2a2 and gck, and the machinery for glucoseinduced Insulin secretion. β-cell destruction triggers massive sst1.1 δ-cell conversion to bihormonal cells. Our work shows that their pro- β-cell identity predisposes this zebrafish δ-cell subpopulation to efficient age-independent neogenesis of Insulin-producing cells and provides clues to restoring functional β-cells in mammalian diabetes models. [less ▲]

Detailed reference viewed: 37 (8 ULiège)
Full Text
See detailCosmological Distances: Calculation of distances in cosmological models with small-scale inhomogeneities and their use in observational cosmology
Helbig, Phillip ULiege

Doctoral thesis (2021)

In cosmology, one often assumes that the universe is homogeneous and isotropic. While originally a simplifying assumption, today there is observational evidence that this is a good approximation in our ... [more ▼]

In cosmology, one often assumes that the universe is homogeneous and isotropic. While originally a simplifying assumption, today there is observational evidence that this is a good approximation in our Universe on scales above a few hundred megaparsecs. This approximation is often used when calculating various distances as a function of redshift, even though the scales probed by a beam of light are much smaller than the scale of homogeneity. Since our Universe is obviously not homogeneous and isotropic on small scales, it is at least conceivable that this could affect distance calculation. Two models have been proposed in order to take such small-scale inhomogeneities into account in a relatively simple way. One, due to Zel’dovich, involves a two-component universe where one component is smoothly distributed and the other in clumps, with the assumption that, when calculating distance from redshift, light propagates far from all clumps. Under those assumptions, one can derive a second-order differential equation for the distance. This is a simple ansatz but it is not obvious how valid it is. Another approach, originally due to Einstein and Straus but developed with regard to cosmological-distance calculation by Kantowski, involves removing material from a spherical region of an otherwise smooth universe and redistributing it inside this sphere (e.g. as a point mass at the centre, as a shell at the boundary, or in a more complicated manner). This ansatz is more difficult for calculations, but is an exact solution of the Einstein equations, so there is no question about its validity (how realistic such a mass distribution is as a model of our Universe is a separate question). Long after both had been investigated in detail, Fleury showed that they are equivalent at a well controlled level of approximation. After a review of the history of those two approaches, I present my own work in this area: an efficient numerical implementation for the solution of the most general form of the differential equation (i.e. arbitrary values of λ0, Ω0, and the homogeneity parameter η, the last indicating the fraction of matter distributed smoothly), a discussion of the uncertainty in distance calculation due to uncertainty in the value of η, the effect of η on the calculation of H0 from gravitational-lens time delays, the effect of η on the separation between images in a gravitational-lens system, and the effect of η on the determination of λ0 and Ω0 from the m–z relation for Type Ia supernovae—including evidence that observations indicate that, in our Universe, the standard distance is a good approximation, even though small-scale inhomogeneities can be appreciable, probably because the Zel’dovich model does not accurately describe our Universe. [less ▲]

Detailed reference viewed: 79 (16 ULiège)
Full Text
See detailGenomic and biologic comparisons of Cyprinid herpesvirus 3 strains: a journey into virus evolution in vitro and in vivo
Gao, Yuan ULiege

Doctoral thesis (2021)

Cyprinid herpesvirus 3 (CyHV-3), also known as koi herpesvirus (KHV), is a member of the genus Cyprinivirus, family Alloherpesviridae, order Herpesvirales. CyHV-3 is responsible of a lethal disease in ... [more ▼]

Cyprinid herpesvirus 3 (CyHV-3), also known as koi herpesvirus (KHV), is a member of the genus Cyprinivirus, family Alloherpesviridae, order Herpesvirales. CyHV-3 is responsible of a lethal disease in common and koi carp (Cyprinus carpio) which are economically important fish species. Over the last two decades, several CyHV-3 strains have been isolated in different countries. Complete genome sequences of 4 strains (KHV-U, KHV-J, KHV-I and KHV GZ11) were available in the Genbank at the beginning of this PhD project, but no comparisons of the biologic properties of these strains have been reported. In the first part of the thesis, we have sequenced the genomes of a further seven strains from various geographical sources, and have compared their growth in vitro and virulence in vivo. This part illustrates the importance of coupling genomic and biologic comparisons of viral strains in order to enhance understanding of viral evolution and pathogenesis. It revealed a negative correlation among strains between viral growth in vitro and virulence in vivo. This observation suggested the existence of alleles conferring adaptation to cell culture but reduced fitness in vivo and vice versa. The objective of the second part of this thesis was to identify such alleles. We identified the formation of syncytium in vitro as a common trait of cell culture adapted CyHV-3 strains. Comparison of virion transmembrane proteins encoded by CyHV 3 strains and production of various recombinants demonstrated that the genetic determinism of this trait is linked to a single nucleotide polymorphism (SNP) of ORF131 encoding a structural glycoprotein. Recombinant strains differing only by this SNP (183A and 183T) were compared for their fitness in vitro and in vivo. The ORF131 183A allele associated with syncytium formation revealed the highest fitness in vitro but the lowest in vivo. Interestingly, co-infection experiments by the two recombinants encoding ORF131 SNP revealed both in vitro and in vivo that the variant with the highest fitness contributed to the purifying selection of the less fit variant through the inhibition of superinfection, which could contribute the low diversity observed in CyHV-3 species. [less ▲]

Detailed reference viewed: 48 (6 ULiège)
Full Text
See detailDesign of lattice towers from hot-rolled equal leg steel angles
Bezas, Marios-Zois ULiege

Doctoral thesis (2021)

Angles profiles have been used since the very beginning of steel construction due to their easy transportation and on-site erection. However, they exhibit specific features that clearly distinguish them ... [more ▼]

Angles profiles have been used since the very beginning of steel construction due to their easy transportation and on-site erection. However, they exhibit specific features that clearly distinguish them from other types of common sections, what inevitably leads to the need for the development of specific design provisions. In a first step, existing European specifications on hot-rolled equal angle sections were critically reviewed and then, in a second step, extensive experimental, analytical and numerical studies have been conducted to propose a complete and duly validated set of design rules covering all aspects of design for angles. These rules include cross section classification, cross section resistance for all types of loading as well as rules for member design to individual and combined internal normal forces and moments. All the proposed rules are written in Eurocode 3 format to allow a direct possible inclusion in forthcoming drafts. Furthermore, angle profiles are extensively used in lattice towers and masts for telecommunication purposes or electric power transmission. Such types of towers are mainly designed according to EN 1993-3-1 and EN 50341-1, based on a first-order linear elastic structural analysis of a truss structure. An assessment of the current design approach is performed, where the tower has been simulated with a full non-linear finite element software, considering relevant imperfections as well as geometrical and material non-linearities. The importance of the second order effects in the analysis is underlined while the existence of an instability mode not properly covered directly by the norms, and usually therefore not checked, is highlighted. Two analytical models for the prediction of the critical load of the new buckling mode are proposed and validated numerically. Both proposed models are rather easy to apply and may fill the gap in the existing design recommendations for lattice towers. [less ▲]

Detailed reference viewed: 75 (25 ULiège)
Full Text
See detailTaking advantage of multicomponent reactions for the synthesis of advanced polymers and porous materials
Stiernet, Pierre ULiege

Doctoral thesis (2021)

The present thesis aims to contribute to the quest for increasingly complex functional polymers while respecting a simpler and more efficient chemistry. For this purpose, we took advantage of ... [more ▼]

The present thesis aims to contribute to the quest for increasingly complex functional polymers while respecting a simpler and more efficient chemistry. For this purpose, we took advantage of multicomponent reactions which involve at least three compounds and yield complex structures containing almost all atoms of the reactants. First, stimuli-responsive and biocompatible materials were synthesized using the Ugi four-component polymerization of amino acids. A variant of this reaction was then adapted for step-growth polymerization leading to a series of unprecedented poly(α-amino amide)s. In a second part, the Radziszewski reaction and the emulsion-templating polymerization method were combined giving access to macroporous poly(imidazolium)s networks of interest in catalysis and CO2 capture. [less ▲]

Detailed reference viewed: 59 (14 ULiège)
Full Text
See detailImproving Citrus tolerance to Huanglongbing through neutralizing soil acidity and exploring biocontrol resources
Li, Bo ULiege

Doctoral thesis (2021)

Huanglongbing (HLB), previously called citrus greening disease, is one of the most devastating diseases in citrus production. Since the causal pathogen (Candidatus Liberibacter asiaticus), which is mainly ... [more ▼]

Huanglongbing (HLB), previously called citrus greening disease, is one of the most devastating diseases in citrus production. Since the causal pathogen (Candidatus Liberibacter asiaticus), which is mainly transmitted by the Asian citrus psyllid (ACP) Diaphorina citri, of HLB has not been successfully cultured artificially, further researches on its pathogenic mechanism and the development of pathogen control technology are needed. Meanwhile, field observations showed that low pH values of soil and the prevalence of HLB disease in citrus orchards in South China generally occurred simultaneously. However, there is a lack of knowledge about the relationships between soil properties and the occurrence and development of HLB. The influence of soil acidify on citrus tolerance to HLB is also seldom taken into account to understand a suitable soil environment for plant growth and defense. Moreover, although it is well known that a stable plant-related microbial community is essential to plant health, most of current studies only focus on HLB interference with the inherent host-microbial interaction. There is no in-depth study on how to improve the resistance of citrus to HLB by remodeling root-related microorganisms. In this work, the aim was to enlighten the proteome-level response of diseased citrus trees to C. L. asiaticus infection during the development of HLB symptoms and to reveal the role of soil environment and beneficial bacteria in contribution of enhanced citrus tolerance to HLB. This is based on the conceptual model of disease triangle, trying to provide a candidate scheme for the HLB control from the perspective of optimizing the environmental factors of its three causal components. HLB should be controlled and mitigated by different and comprehensive measures in order to maintain the quality and productivity of citrus fruits. In spite of this, the use of biological control approaches to control HLB and ACP is still in the initial stage of research and beneficial microbial resources are obviously insufficient. To this end, the exploration and development of biological control agents with insecticidal and antibacterial characteristics are worthy of more efforts. Then, the study was carried out in four research axes described in the following paragraphs. As preliminaries, we detailed the changes in biological processes of host citrus during the establishment of HLB disease symptoms. Comparative proteomics analysis were performed to reveal the global protein accumulation profiles in leaf petiole of CLas-infected Citrus at the asymptomatic and symptomatic stages compared to healthy counterpart. We found that photosynthesis was suppressed throughout the whole CLas infection cycle. Also, lots of crucial starch biosynthesis and trivial immune defense associated proteins were induced after the symptom-free prodromal period. Moreover, the protein-protein interaction network analysis indicated that a F-type ATPase and an alpha-1,4 glucan phosphorylase were the core nodes in the interactions of differentially accumulated proteins. The analysis of endogenous hormones in different disease stages of citrus supported that the changes of SA and JA content were positively correlated with the abundance of phytohormone biosynthesis-related proteins. In the second research axis, lime application (3000 kg/ha ploughed into topsoil) proved to be a manageable and practical method to optimize soil pH and enhance the endurance capacity of citrus against C. L. asiaticus, resulting in increased yield and fruit quality of citrus in liming-amended soils. These meaningful effects may be attributed to the improvement of acidic soil that can increase the root metabolic activity and up-regulate the expression of ion transporter-related genes in HLB-infected roots, as well as alleviate the physiological disorders of sieve tube blockage of HLB-infected leaves and improve the content of chlorophyll. Meanwhile, the immune response involved in SAR and activating the salicylic acid signal pathway of diseased citrus was strengthen after applying lime. The third research axis focused on the relationship between liming practice the changes of soil properties and root-associated microbes of HLB-infected citrus. The extent of soil acidification and aluminum toxicity was mitigated after soil improvement, accompanied by the increase of root activity and the decrease of pathogen concentration in citrus roots. Likewise, lime application strongly altered root endophytic microbial community diversity and structure, which represented by the enrichment of beneficial microorganisms in disease roots. It also enriched functional categories involved in host-microbe interactions and nitrogen and sulfur metabolisms in the HLB-infected citrus rhizosphere. Then, we highlight the important role of root microbiota changes and ecological factors, such as soil acidity, in delaying and alleviating HLB disease. In the last experimental chapter, a nematode-symbiotic bacterium Xenorhabdus budapestensis strain C72 was identified with broad-spectrum antimicrobial activity and high-efficiency insecticidal activity. In Bipolaris maydis - Maize pathosystem, the early colonization of pathogenic fungi was significantly impaired by C72 supernatant treatment. Symbiotic bacteria secrete extracellular enzymes and induce the expression of host defense-related genes may be the reasons for the antimicrobial potential of C72. In addition, a high-quality complete and annotated genome sequence was reported, showing that the genome contains multiple secondary metabolite biosynthetic gene clusters. In conclusion, this study is among the first to focus on the interfer effects on the soil acidify and dynamic plant microbiota on the occurrence and progression of HLB. It provides interesting results on global protein accumulation profiles in response to CLas infection during the prodromal stage and advances the understanding of the association between soil improvement with the HLB endurance of diseased citrus. [less ▲]

Detailed reference viewed: 97 (11 ULiège)
Full Text
See detailWeak localisation in the transport of interacting Bose-Einstein condensates across random media
Chrétien, Renaud ULiege

Doctoral thesis (2021)

Quantum simulation with ultracold atoms gained a lot of traction recently by proposing a framework with a lot of flexibility, versatility and tunability to emulate diverse quantum ef- fects. It indeed ... [more ▼]

Quantum simulation with ultracold atoms gained a lot of traction recently by proposing a framework with a lot of flexibility, versatility and tunability to emulate diverse quantum ef- fects. It indeed provides the ideal playground to study many–body effects in a well–controlled environment and is particularly useful in the domain of quantum coherent transport of waves in random media. The purpose of this thesis is to study several configurations of coher- ent transport within random media with Bose–Einstein condensates and to investigate the interplay between coherence and interaction effects. In particular, we start by numerically studying Aharonov–Bohm oscillations in the transmission of particles across the eponymous rings in a 1D configuration. When exposed to a suitably chosen disorder potential, those rings yield oscillations with double frequency, which are routinely encountered in solid–state physics where they are referred to as Al’tshuler–Aronov–Spivak oscillations, similar in essence to coherent backscattering and weak localisation. We then study the behaviour of those os- cillations in the presence of interaction within Aharonov–Bohm rings and find that in the mean–field regime, they are inverted for finite interaction. Truncated Wigner simulations are then carried out in the same scenario and indicate that the inversion should be observ- able for realistic atomic and experimental parameters with 39 K atoms, although dephasing of the oscillations is observed at strong interaction owing to interaction–induced inelastic scattering. A first–order nonlinear diagrammatic theory is then presented and benchmarks our numerical findings. The question of the inversion prevalence is then investigated in a 2D scenario, following state–of–the–art observations in the literature. It has indeed been nu- merically observed that coherent backscattering is inverted in the mean–field approximation for finite interaction strength. We numerically confirm this observation with our study and extend it beyond the mean–field approximation by applying the truncated Wigner method. These simulations show that the inversion prevails beyond the mean–field regime and should moreover be observable experimentally with 87 Rb atoms for realistic parameters, despite a partial dephasing. This dephasing however completely eclipses interference effects and washes out this signature of antilocalisation for stronger interaction. [less ▲]

Detailed reference viewed: 84 (12 ULiège)
Full Text
See detailExperimental study and numerical modeling of length scale effects in nickel sheets - Shear, uniaxial tensile and large tensile tests at various temperatures
Yuan, Sibo ULiege

Doctoral thesis (2021)

The main objective of this thesis is to study the influence on the mechanical behavior of variations of the ratio between part dimensions and the material microstructure, as well as the influence of ... [more ▼]

The main objective of this thesis is to study the influence on the mechanical behavior of variations of the ratio between part dimensions and the material microstructure, as well as the influence of various interfaces. Such features are generally labelled as ‘size effects’. At small length scale (typically in micro/meso range), the relative size between mechanical part and the grains of the polycrystal plays an important role on the overall mechanical behavior. Indeed, the sample size becomes comparable to the grain size at such length scale and the influence of individual grains cannot be neglected. The literature review demonstrates that such dependence between the mechanical behavior and the length scale is widely observed in the experimental tests on various materials. The Hall-Petch (HP) relation, in which the flow stress is expressed by a function of the grain size, is used to compute the effects of the mechanisms underlying such size dependent mechanical behavior. In this work, the size effects, triggered by varying the number of grains across the sample thickness, are investigated for high purity nickel polycrystal sheets. The influences of the stress path and the temperature on the size effects are also considered by performing shear, simple (uniaxial) tensile and large tensile experimental tests at room temperature and 573 K. As expected, the modifications of the mechanical behavior with different numbers of grains across the thickness, are affected by the test conditions (different types of loading and temperatures). The reduced stress level with an increase in grain size (or a decrease in number of grains across the thickness) depends not only on the stress path but also on the temperature. A moderate increase in temperature can promote the emergence of quasi-single crystal behavior. For the numerical modeling, a Strain Gradient Crystal Plasticity (SGCP) model was implemented into a Finite Element (FE) framework using Lagamine software. A specific 3D displacement based brick shape element with 20 nodes, 8 integration points and 21 nodal degrees of freedom was developed. Among the 21 degrees of freedom, 18 are dedicated to the Geometrically Necessary Dislocation (GND) densities, including 12 edge types and 6 screw types in a Face-Centered Cubic (FCC) crystalline structure. To improve the modeling of interfaces, an original flexible boundary condition for GND densities was proposed. With a tunable length scale parameter, the interfacial behavior of GND can be modeled as any intermediate state between the fully permeable and the impermeable states. The FE simulations with a microscopic approach were carried out by employing a small Representative Volume Element (RVE) with constant dimensions. The number of grains inside the RVE was modified by varying the grain size in agreement with the values measured on the experimental samples. The reduced stress level with an increase in grain size can be correctly predicted in the form of a HP relation by the microscopic simulations. The mechanisms behind the modification of mechanical behavior with the grain size were analyzed through various microstructural properties (e.g. resistance to lattice slip, mean free path for the motion of dislocations etc.) thanks to the microscopic approach with the SGCP model. Furthermore, the free surface effects, stemmed from the escape of dislocations at free surfaces, can be characterized by the gradient of mechanical behavior and microstructural properties between surface grains and core grains.   [less ▲]

Detailed reference viewed: 74 (17 ULiège)
Full Text
See detailCapturing Transparency in a Nonprofit Setting: What, How, and Why?
Dethier, Fanny ULiege

Doctoral thesis (2021)

Among the different types of organizations—for-profit, public and nonprofit, nonprofit organizations (NPOs) are particularly dealing with increasing pressure to demonstrate transparency. However, the ... [more ▼]

Among the different types of organizations—for-profit, public and nonprofit, nonprofit organizations (NPOs) are particularly dealing with increasing pressure to demonstrate transparency. However, the distinctive features of NPOs’ transparency and their interaction with stakeholders’ perceptions are still subject to debate. Accordingly, this dissertation aims to capture transparency in a nonprofit setting by relying on four studies. Each study builds a theoretical framework and, when suitable, presents empirical assessments of aspects of the issue under consideration. The first study adopts the NPO’s perspective to propose a complete conceptualization and operationalization of transparency implementation. This study identifies information accessibility, completeness, and inferability as necessary dimensions of NPOs’ transparency. An empirical assessment of 432 Belgian NPOs’ transparency practices supports the soundness of both this conceptualization and operationalization of NPOs’ transparency. Considering the saliency of donors’ information needs for NPOs, the second study adopts the donors’ perspective to propose a multidimensional conceptualization and operationalization of transparency. The three necessary dimensions include information accessibility, completeness, and accuracy. A thorough scale development process results in a reliable and valid measure of perceived NPOs’ transparency. The third study offers—thanks to a systematic literature review—an integrative framework of antecedents and outcomes of NPOs’ transparency. A critical analysis of this framework suggests that some crucial aspects of NPOs’ transparency—i.e., direction of NPO transparency, distinguishing implemented from perceived transparency, the dark side of NPO transparency, and NPO transparency contingency factors—remain critically understudied, despite their relevance. II The fourth study proposes an empirical assessment of some antecedents selected out of the integrative framework developed in Chapter 3. In doing so, the utility of one of this dissertation’s measurement tool is highlighted (i.e., the index of NPOs transparency developed in Chapter 1), along with the necessity to explore further antecedents of NPOs’ transparency. Although the contributions of this thesis are particularly relevant for the nonprofit sector, this dissertation is insightful for any organization. Thus, thanks to its theoretical and practical contributions, the present thesis promotes, on the one hand, the strengthening of organizational transparency at the implementation and perception levels and, on the other hand, the set-up of a transparent informational environment. [less ▲]

Detailed reference viewed: 39 (8 ULiège)
See detailPreparation and characterization of non-isocyanate polyurethane hydrogels and coatings for indoor air decontamination
Bourguignon, Maxime ULiege

Doctoral thesis (2021)

Indoor air pollution was recently highlighted to be responsible for many health problems like respiratory track irritation. Organic solvents and some plasticizers are taking part to this problem and ... [more ▼]

Indoor air pollution was recently highlighted to be responsible for many health problems like respiratory track irritation. Organic solvents and some plasticizers are taking part to this problem and belong to the family of volatile organic compounds (VOC) that accumulate inside our more and more “hermetically” closed living spaces. Amongst them, toxic formaldehyde (FA) is largely used for formulating furniture coatings, carpets, flooring and is one of the main contributors of our indoor air pollution. Few strategies have been developed for dealing with FA accumulation, notably by capturing in porous matrices or by (photo)degradations using rare earth-based metals or photocatalysts, or by bioremediation using enzymes. However, when this thesis started, bio-active coatings (thus loaded by FA degrading enzymes) able to efficiency capture and degrade FA into non-toxic compounds and that could be easily deposited on elements of our closed areas (walls, ceiling, furniture, etc.) were not reported. This thesis aims to prepare new organic coatings able to reduce formaldehyde by degradation by enzymes under ambient conditions, thus adaptable for indoor life space implementation, using a chemistry that is as green as possible. As enzymes are often inactivated when used out of their natural environment, this work is mainly focused on developing new routes for producing coatings from precursors and under conditions that are tolerant to the enzyme stability and activity. Non-isocyanate polyurethanes of the poly(hydroxyurethane)-type are investigated in this work, as they constitute greener alternatives to the widespread conventional polyurethanes found in many high performance coatings. Indeed, these conventional polyurethanes, produced by the toxic isocyanate chemistry, are sources of pollution due to the presence of residual solvents or residual isocyanates that are released in the environment. Therefore, this work is dedicated to the elaboration of greener poly(hydroxyurethane)s adaptable for enzyme entrapment by the polyaddition of poly(cyclic carbonate)s to polyamines with the challenge to produce them in water at room temperature without requiring the use of organic solvents. The influence of the structure of the comonomers and the reaction conditions on the formation of the polymer matrix and the entrapment of the formaldehyde degrading enzyme is explored and largely discussed. The potential of the various products as coatings for formaldehyde abatement are also reported. This thesis was carried out in the frame of the BIODEC project that was financed by le Fonds européen de développement régional “(FEDER) et la Wallonie dans le cadre du programme opérationnel ‘Wallonie-2020.EU’”. [less ▲]

Detailed reference viewed: 56 (15 ULiège)
Full Text
See detailConstruction sociale de la sécurité alimentaire et dynamique de la solidarité dans les ménages de Kinshasa. Essai d’analyse socio-anthropologique
Nambuwa Bila Lenge, Régine ULiege

Doctoral thesis (2021)

The Democratic Republic of Congo is one of the countries in the world that meets all the climatic conditions to feed its population. As a result, it is theoretically capable of making do with domestic ... [more ▼]

The Democratic Republic of Congo is one of the countries in the world that meets all the climatic conditions to feed its population. As a result, it is theoretically capable of making do with domestic production to feed its population without resorting to imports. It has arable land, a diversity of climates and a hydraulic network that can provide good irrigation and agriculture throughout the year. Its population is predominantly young and can be used as a labor force. However, the DRC is paradoxically one of the countries most affected by famine and food insecurity in the world. Its potential remains underexploited. National production shows a glaring deficit, far from meeting the food needs of the population and forces the country to turn to imports. To date, all the indicators prove that food and nutritional security (SAN) in the DRC cannot be guaranteed without resorting to imports. In 2014, the chronic malnutrition rate was 43% for whole country and 17% in Kinshasa (INS, 2013-2014). At the end of the CPI analyses carried out between July and December 2019, 26% of the population analysed were in a situation of acute food insecurity (Phases 3 and 4), of which more than 4 million were in an emergency situation (Phase 4). Projections from January to May 2020 indicate that around 13.24 million people, or 28%, will be acutely food insecure (Phases 3 and 4), of which more than 3.4 million will be in an emergency situation (Phase 4) (DRC CPI, 2019). In urban areas in general, and in Kinshasa in particular, the unemployment rate is considerable. People in paid employment represent 35% of the active population (E-QUIBB / DRC 1-2016: 215). This unemployment limits households' access to food and exposes them to chronic food insecurity. This situation has led to a great impoverishment of the population, forcing households to reorganise themselves by adopting various strategies. Some have developed a number of these practices, using the mobilisation of all members and diversifying sources of income. Others are reducing the quality and number of meals. Some heads of households explicitly or implicitly solicit children's contribution to the household budget. Others have made it a 'social norm': bi tie te bi lie te (who does not contribute does not eat). We wanted to understand the impact of all these practices and strategies on social relations within households. To do this, a qualitative study was carried out in three sites in Kinshasa, namely: Limete, Ndjili and Makala. For more than six months, we monitored consumption in 30 households divided into three categories: poor, average and well-off. Using semi-directive interviews, direct observations, life stories and consumption records, we observed and questioned the different actors involved in the survival of the households. This information was supplemented by the consumption records, which made it possible to take a sample of each household's daily consumption. As a model for data production and analysis, we used the theory of social practices. The socio-anthropological method was used as an analytical grid to grasp the different logics of action developed by the actors around food. The results of the study show that fundraising practices vary from one environment to another, from one household to another, and even from one individual to another. Culinary space appears to be a divisive and unifying factor in all the sites. The people in charge of preparation vary from one site to another and from one household to another. It is mainly the woman who is in charge of cooking. When she works outside her household, she is replaced by another woman who is either a relative, her daughter or her maid. Consumption is the time of all issues where we observed the division between the entitled and the excluded, individualism, the failure to take into account the notion of family, the instability of the alliance with the change of allies according to circumstances; a moment of unity for some households, of sharing, contradiction and solidarity towards parasitic households for others. In short, this is the moment when we can observe the crisis in solidarity and solidarity in the crisis in the poor and intermediate class. [less ▲]

Detailed reference viewed: 31 (2 ULiège)
Full Text
See detailStudy on the mechanism linking the intestinal Cetobacterium and acetate to the regulation of glucose homeostasis and growth performance in zebrafish
Wang, Anran ULiege

Doctoral thesis (2021)

With the development of intensive culture systems to meet the increasing demand for global aquatic products, there has been an increasing incidence of diseases outbreak and substantial economic losses for ... [more ▼]

With the development of intensive culture systems to meet the increasing demand for global aquatic products, there has been an increasing incidence of diseases outbreak and substantial economic losses for farmers. Antibiotics are used as prophylaxis in this context causing serious drawbacks such as the surge of antibiotic resistance strains of common pathogens including humans. National bans for the administration of some antibiotics have been issued to minimize their overuse in aquaculture. As an alternative to antibiotics, probiotics have been proposed as a promising solution. Commensal gut microorganisms have been proposed as key suppliers of beneficial candidate probiotics. A substantial body of evidence supports that the gut microbiota plays critical roles in the regulation of metabolic, endocrine, and immunes functions. SCFAs, the main microbial metabolites produced by bacterial fermentation of indigestible carbohydrates in the intestines, are considered key candidate mediators in the microbiota-gut-brain communication directly or indirectly modulate processes associated with food intake, insulin secretion, and whole-body energy homeostasis. Currently, how to improve the ability of fish to use carbohydrates is another urgent scientific problem in aquaculture. With the development of aquaculture industry, high-carbohydrate diets were used to stimulate the protein-sparing effect and reduce feed costs. However, the utilization of carbohydrates in fish is limited compared to mammals, especially in carnivorous species. Fish fed with high levels of carbohydrates will lead to persistent postprandial hyperglycemia, and further induce low efficiency of feed utilization, abnormal fat deposition, and even high mortality. Here too, relevant probiotics could improve the utilization of carbohydrates in fish. Therefore, the aim of this work was to explore the potential host-associated probiotic, investigate the mechanism of indigenous probiotic regulate fish glucose homeostasis, and evaluate the beneficial effects of gut microbial metabolites on fish health. In experiment 1, we explored host-associated probiotic for fish by performing proteomic analysis and 16S rRNA gene sequencing to investigate the mucus proteins and adhesive gut microbiota of different intestinal segments in adult zebrafish, from proximal, mid and distal gut segments. The results revealed that the three intestinal segments investigated exhibited significant differences in functions, and these differential proteins are more involved in metabolic processes. The composition of intestinal microbiota also showed differences in the three segments. At the genus level, Cetobacterium was the predominant taxa in midgut. Moreover, we also determined that the midgut mucus layer was the thickest among the segments, indicating that Cetobacterium might have better colonization capacity in zebrafish midgut. This finding has led us to further explore the role of this bacteria in the fish gut and its potential use as probiotic in aquaculture. In experiment 2, we investigated the beneficial effects of commensal Cetobacterium on zebrafish glucose homeostasis. To explore the effect of feeding habits on the gut microbial composition and glucose homeostasis, 2-month-old zebrafish were fed with three formulated diets mimicking carnivorous diet (CD), omnivorous diet (OD) and herbivorous diet (HD) for 2 weeks. The results demonstrated that feeding habits could influence the composition of gut microbiota, and the Cetobacterium somerae was enriched in OD and HD groups. Zebrafish fed with omnivorous diet (OD) and herbivorous diet (HD) showed better glucose homeostasis compared with carnivorous diet (CD), suggesting a beneficial effect of enriched C. somerae on glucose utilization. To confirm the causative effects of C. somerae enrichment in glucose homeostasis in fish, conventionally raised (CONR) zebrafish were fed the basal diet with or without non-absorbable antibiotic mixture for 1 week. Then, exogenous C. somerae or Aeromonas veronii B565 (negative control) were applied to the rearing water of antibiotic-treated zebrafish. We observed significantly decreased postprandial blood glucose level and increased insulin concentration in C. somerae treated zebrafish. Furthermore, we mono-associated germ-free (GF) zebrafish with A. veronii B565 + Plesiomonas shigelloides, or A. veronii B565 + P. shigelloides + C. somerae. Consistently, gnotobiotic larval zebrafish with C. somerae colonization showed significantly lower glucose levels and increased insulin expression, and C. somerae colonization was associated with higher acetate level in whole-larvae zebrafish, which suggested the regulation of commensal C. somerae in zebrafish glucose homeostasis and a role for its metabolite acetate in this regulation. Dietary sodium acetate and intracerebroventricular (ICV) injection of NaAc or NaAc + atropine demonstrated that the effects of both acetate and C. somerae on glucose homeostasis was mediated through parasympathetic activation. This study highlights a specific C. somerae-brain axis in the regulation of glucose homeostasis in fish and suggests a role of acetate in mediating the axis function. Our results suggest potential strategies for improvement of fish carbohydrate utilization. In experiment 3, we further evaluated the effects of acetate on fish growth performance. 1-month-old zebrafish were fed with 0.15% sodium acetate (NaAc) for 4 weeks. At the end of the feeding trial, zebrafish fed with 0.15% NaAc showed higher weight gain and daily feeding rate compared with the control group. Dietary supplementation of 0.15% NaAc significantly promoted the body fat mass, energy gain and energy conversion efficiency, as well as intestinal digestive enzyme (amylase) activity in fish. The expression of food intake-related genes (ghre, npy and npy7R) in the brain of fish fed on the diet contacting NaAc was higher than that of the control group. Furthermore, intracerebroventricular (ICV) injection of NaAc or NaAc + atropine showed that acetate played a direct role in controlling appetite through the parasympathetic nervous system. Finally, there was significant decrease in the relative abundance of Plesiomonas genus in the fish gut fed on the diet supplemented with NaAc. This study suggests that sodium acetate has a potential value as fish feed additive in aquaculture. In conclusion, this thesis demonstrated that the commensal acetate-producing strain Cetobacterium has beneficial effects on fish glucose homeostasis, and provided evidence for benefits of a specific Cetobacterium-brain axis in the regulation of glucose homeostasis in fish, suggested a role of acetate in mediating the axis function. It also revealed the beneficial effects of sodium acetate on fish growth performance and health status, suggesting that sodium acetate might be a potential feed additive for aquaculture. This work not only may provide theoretical references for improvement of fish carbohydrates utilization targeting gut microbiota, but also promote the development of functional feed additives for fish health. [less ▲]

Detailed reference viewed: 74 (7 ULiège)
Full Text
See detailInvestigating genetic and environmental factors impacting potato dormancy and assessing management strategies to control potato sprouting during storage
Visse-Mansiaux, Margot ULiege

Doctoral thesis (2021)

Sprouting during potato storage must be controlled as it leads to a decrease in tuber weight, a reduction in nutritional and processing quality, and consequently economic losses. To avoid losses during ... [more ▼]

Sprouting during potato storage must be controlled as it leads to a decrease in tuber weight, a reduction in nutritional and processing quality, and consequently economic losses. To avoid losses during storage, chlorpropham (CIPC) has been extensively used for decades due to its high efficiency and affordability to mitigate potato sprouting. However, because CIPC and its major metabolite are a potential risk to human health, CIPC has recently been removed from the European market (EU regulation 2019/989). Consequently, the main objective of this thesis was to find economically suitable and sustainable management strategies to control potato sprouting. In this thesis, the influence of year, location and variety factors on potato dormancy was assessed. The analysis was performed using 3,379 records of multi-environment trials collected in Switzerland in five different locations with contrasting environments, over 25 years. In total, 537 genotypes were tested. The potential to predict potato dormancy of 247 predictors (i.e., environmental factors and management during the growing season variables) was evaluated using a forward selection approach to select a model predicting the duration of dormancy. Variety was the most important variable to explain the variability in dormancy (60.3 %), while year and location explained 13.9 % and 5.4 % of the dormancy variability, respectively. The selected predictive model used the variety class and a parameter related to the temperature of the growing season as predictors. The importance of the temperature parameter was confirmed by a greenhouse trial. In order to find alternative anti-sprouting treatments, the potential to control potato sprouting of several synthetic pre- and post-harvest molecules was investigated (i.e., Maleic hydrazide (MH); 1,4-Dimethylnaphtalene (1,4-DMN); 3-decen-2-one and CIPC) and compared to an untreated control. The potential of 1,4-DMN and 3-decen-2-one post-harvest treatments to reinforce the efficacy of MH pre-harvest treatment was also investigated. Residue analyses were performed at the end of the storage. Results showed that all pre- and post-harvest treatments significantly mitigated sprouting for up to seven months of storage. The efficacy of the tested molecules to reduce the sprout weight in comparison to the untreated control was 86.9 %; 77.9 %, 73.6 % and 99.8 % for the MH; 3-decen-2-one, 1,4-DMN and CIPC molecules, respectively. The advantage of the 3-decen-2-one treatment is that it leads to complete necrosis of sprouts within 24 hours after treatment and it can be used as a curative treatment to save potato stocks that have already sprouted. In this study, results showed that there was no benefit to combine pre- and post-harvest treatments to mitigate sprouting. A variety-dependent effect of sprouting and treatment efficacy was observed. In addition, no residue of 1,4-DMN was observed in treated tubers (< LOQ), while residues of both CIPC and MH were found in treated tubers. The efficacy of natural molecules to mitigate sprouting was also evaluated and compared to an untreated control. The tested natural molecules were L-carvone, D-limonene (i.e., mint and orange essential oils, respectively) and ethylene. All the tested molecules efficiently controlled sprouting for up to five months of storage at 8 °C. These natural molecules are advantageous because they are authorized to treat potatoes in organic farming and they can so far be used without a maximum residue limit in the final product. As an alternative or complementary approach, the potential of cold storage (i.e., at 4 °C) to mitigate sprouting after 4.5 months of storage in comparison to storage at a higher temperature (i.e., 8 °C) was evaluated for six processing potato varieties (Lady Claire, Verdi, Kiebitz, Pirol, Agria and Markies). The CIS-ability of these six potato varieties was evaluated by measuring relevant determinant parameters for the industry (e.g., acrylamide content, sucrose content, RS or crisp color quality) after two and/or four months of storage at 4 °C and 8 °C. The potential of reconditioning at 15 °C after a cold storage at 4 °C to decrease total RS, glucose and acrylamide contents in potato tubers was also evaluated. Vacuolar invertase (VInv) gene expression level was measured in tubers stored at 4 °C, at 8 °C and reconditioned at 15 °C. Results showed that a storage at 4 °C efficiently mitigates sprouting in the six tested varieties for up to 4.5 months of storage. Three CIS-resistant varieties were identified (i.e., Lady Claire, Verdi and Kiebitz) and displayed a low total RS and/or glucose content for up to four months of storage at 4 °C. In addition, the reconditioning efficiently reduced the glucose content and the Vinv gene expression in the Markies variety after storage at 4 °C. Several correlations have been observed between glucose or RS content and VInv gene expression. Based on the results obtained in this thesis, several potato management strategies are proposed to mitigate sprouting for different sprouting pressure scenarios. [less ▲]

Detailed reference viewed: 103 (19 ULiège)
Full Text
See detailAsteroseismic study of solar-like pulsators along their evolution
Farnir, Martin ULiege

Doctoral thesis (2021)

Following the advent of space-borne missions (e.g. CoRoT, Kepler), came a wealth of data of unprecedented quality. This enabled asteroseismology to thrive and to probe the stellar structure of a wide ... [more ▼]

Following the advent of space-borne missions (e.g. CoRoT, Kepler), came a wealth of data of unprecedented quality. This enabled asteroseismology to thrive and to probe the stellar structure of a wide variety of pulsating stars. Amongst these pulsating stars is the notable category of low-mass stars. These exhibit masses below 2.3 solar-mass , encompassing the case of our Sun. Throughout their evolution, these stars exhibit a few interesting peculiarities. First, during the main-sequence phase, they display a very regular pressure-mode oscillation spectrum. However, small perturbations to that regularity may occur. Such perturbations are the result of sharp and localised variations in the stellar structure. These create an oscillating feature, as a function of the frequency, in the oscillation spectrum, the so-called glitches. These glitches are of particular interest as they allow us to probe very localised regions of the stellar interior and provide diagnoses about specific stellar features, inaccessible by other means. In main-sequence low-mass stars, we distinguish two main causes of glitches: the helium second-ionisation zone, providing information about the surface helium abundance, and the base of the envelope convection zone, constraining the mixing processes in that region. The first part of my thesis was dedicated to the development of a seismic technique, WhoSGlAd, that consistently analyses the complete oscillation spectra of main-sequence low-mass stars and robustly retrieves the glitches signatures present in these spectra. Special care was put in the definition of stringent seismic indicators as we decorrelated them as much as possible. This is done thanks to a Gram-Schmidt orthonormalisation process. The defined indicators were then used to constrain stellar models and provide a characterisation of both the 16 Cygni system and the Kepler Legacy Sample, representing the best solar-like seismic data currently available. After the main-sequence phase, low-mass stars evolve on the subgiant and red-giant phases. Their core then contracts while their envelope expands, developing a large core-envelope density contrast. This produces the appearance of mixed-modes, presenting a twofold nature: a gravity- dominated nature in the inner radiative regions, and a pressure-dominated nature in the outer convective regions. These modes have the great advantage to propagate throughout most of the stellar interior and, therefore, to probe almost the complete stellar structure. To exploit the information these modes carry, we developed the EGGMiMoSA method. It relies on the asymptotic expression and allows us to precisely measure seismic indicators on both subgiant and red-giant stars. The method was applied to a grid of models extending from the subgiant phase to the luminosity bump. The results are excellent in regard to the asymptotic values of the seismic indicators and also qualitatively agree with observed and theoretical studies. These indicators also allow us to efficiently infer the stellar age, mass, and radius of subgiant stars and of red-giant stars with masses & 1.8 M . Below this threshold, we noted that the central electron degeneracy impaired our diagnosis of the stellar age, mass, and radius in red-giants. The combination of both methods should provide means to constrain the stellar structure of low-mass stars from the early main-sequence phase to the late red-giant one. This is a unique opportunity to study their structure through most of their evolution and, for example, pinpoint missing physical processes in their modelling. [less ▲]

Detailed reference viewed: 38 (4 ULiège)
Full Text
See detailSustainable pathways of manure and sewage management in dairy farming towards the circular economy: Evidence and perspective for China
Zhang, Junyan ULiege

Doctoral thesis (2021)

Due to the well-known benefits of milk and dairy products, the rapid development of the dairy sector plays a critical role in creating livelihoods, particularly for developing countries. Simultaneously ... [more ▼]

Due to the well-known benefits of milk and dairy products, the rapid development of the dairy sector plays a critical role in creating livelihoods, particularly for developing countries. Simultaneously, it supplies massive employment and promotes the agricultural economic development. The increasing demand and consumption of milk and dairy products lead to the intensive development of the dairy industry, along with the enormous amount of manure and sewage generated. Accordingly, the manure and sewage management (MSM) in the dairy sector not only brings considerable challenges of environmental degradation for decision-makers, but also creates opportunities to solve energy crisis and resource depletion issue and provide additional economic and social benefits. In response to a series of policy regulations implemented at both global and national levels, a wide range of dairy MSM strategies have been developed to focus on the improved management of dairy manure and sewage. As a consequence, there is an urgent need for investigating current status of dairy MSM pathways and technologies at both global and national levels, which can benefit to explore environmentally, economically, and socially feasible MSM pathways in the dairy sector. In this thesis, a comprehensive review and a quantitatively comparative analysis for currently available dairy MSM strategies from a global scale were firstly conducted. The results indicated that the consensus of waste-to-energy pathway could be reached to mitigate global warming, eutrophication, and ecotoxicity potential remarkably. For the detailed technologies, anaerobic mono-digestion and its integrated technologies have varying degrees of impacts on reducing global warming and eutrophication potential. However, uncertain impacts for the majority of MSM pathways and detailed technologies were revealed. It indicated that the necessity is required to perform comprehensive trade-off analyses for determining the appropriate MSM pathways towards circularity and sustainability. Secondly, taking China as an example, current technological status and performances of typical dairy MSM technologies were systematically reviewed. These MSM technologies cover the whole management chain based on the field survey of large-scale dairy farms in China, including collection, storage, manure and sewage processing and utilization stages. The analysis results highlighted the need of exploring suitable dairy MSM pathways covering the whole management chain for the government, which should maximize recycling and utilization efficiencies of various nutrients from dairy manure and sewage. Thirdly, in order to identify key pathways to simplify the high diversity of dairy MSM strategies in China, a quantitative typology methodology using a series of data mining techniques was employed. Based on the nationwide survey data of 306 scale dairy farms in China, the results revealed four key MSM pathways. They include low-specialized and traditional (LTM), specialized and recycled (SRM), specialized and diversified (SDM), and semi-specified and biogas project (SBM) modes. The key pathways identified benefit the informed decision-makings of developing effective policies towards the sustainable development and circular economy. Fourthly, the characteristics of general information, bio-physical resource endowments, socio-economic characteristics, production management traits, and attitude and policy subsidies among the four pathways were explored to reveal the potential determinants which might affect the decision-making of dairy farmers’ dairy MSM selection. The statistical results showed that most of indicators in terms of resource endowments, milk productivity and quality, and costs and benefits showed a clear and consistently increasing trend among four pathways (i.e. LTM<SBM<SDM<SRM). The results indicated that resource endowment availability and intensification degree are potential factors of decision-making. Moreover, the up-scaling level of sustainability and policy evaluation from farm individual scale to a higher scale is feasible based on these pathways. In conclusion, the results of the present thesis revealed the necessity of determining appropriate dairy MSM pathways from different scales, which is expected to have the maximum nutrient recycling and utilization from manure and sewage, together with optimally overall benefits by balancing environmental, economic, and social impacts. The mathematical modelling of policy evaluation is particularly required to consider decision-making process of individual dairy farmers and sustainable impacts induced by various technologies and practices along the whole management chain. [less ▲]

Detailed reference viewed: 67 (6 ULiège)
Full Text
See detailRessources territoriales et productivité des entreprises : approches d'analyse spatiale et d'économétrie. Une application sur les entreprises wallonnes
Wilmotte, Pierre-François ULiege

Doctoral thesis (2021)

Productivity determinants are a central research topic. Among these determinants, the impact of territorial resources (especially at sub-national scales) has been under-researched and relatively neglected ... [more ▼]

Productivity determinants are a central research topic. Among these determinants, the impact of territorial resources (especially at sub-national scales) has been under-researched and relatively neglected by mainstream scientific research. Moreover, many productivity studies deal with it at an aggregate level, which may lead to ecological errors in the conclusions related to public policies and regional development. This doctoral research aims to answer three questions to tackle these gaps and issues. To start with, what are the territorial resources that significantly influence firms’ productivity? Methodologically, can we avoid the bias of the ecological error influencing interpretations and conclusions outlined by studies conducted at aggregated levels? And about policy mix, what specific lessons can we learn from improved understanding of the relationship between territorial resources and firm productivity? The thesis was developed in three research areas to address the research questions. Firstly, two systematic literature reviews were conducted to identify the leading productivity indicators, the most appropriate statistical methods and the relevant territorial resources. Then, the spatial structures of several productivity indicators were identified using spatial autocorrelation indexes. Spatial analysis and cartography are suitable tools to identify geographies of firm productivity, but they are currently underused. Finally, based on the spatial structures and the literature, we developed an explanatory model of Walloon firms’ Total Factor Productivity (TFP) by territorial resources. The results underline agglomeration economies’ central role: an imbalance does exist between economies and diseconomies in the major Walloon urban areas. The economies (linked to urban size) are too small by comparison with the structural difficulties related to the industrial decline of these urban areas. In addition, labour markets of nearby metropolises like Brussels or Luxembourg seem to put pressure on Walloon local labour markets (higher wages) and Walloon firms TFP (lower than expected by literature review). Finally, analyses seem to converge in confirming that dense and multifunctional locations are associated with a higher firms’ TFP, invalidating the link between firm competitiveness and cheap land. [less ▲]

Detailed reference viewed: 356 (55 ULiège)
Full Text
See detailInteractions génétiques et environnementales impliquées dans la détermination précoce du sexe chez un modèle de téléostéen : épigénétique, héritabilité et adaptation
Nivelle, Renaud ULiege

Doctoral thesis (2021)

Le Tilapia du Nil, Oreochromis niloticus, est une espèce de poisson tropicale gonochorique d’origine africaine d’un grand intérêt économique. Cette espèce présente un déterminisme du sexe complexe ... [more ▼]

Le Tilapia du Nil, Oreochromis niloticus, est une espèce de poisson tropicale gonochorique d’origine africaine d’un grand intérêt économique. Cette espèce présente un déterminisme du sexe complexe, dépendant de facteurs génétiques majeurs (système XX|XY), de facteurs génétiques mineurs et de facteurs environnementaux, en particulier de la température. Il a en effet été montré que des hautes températures (supérieures à 32°C) appliquées durant le développement induisent une masculinisation des individus dans des proportions variables. De grandes inconnues existent cependant quant à l’intégration de ce signal et à son interaction avec les autres facteurs. Les objectifs de ce travail ont été articulés autour de 4 grands axes de recherche : (1) La remise en contexte de l’inversion sexuelle par les hautes températures, (2) la recherche de nouveaux gènes (3) l’étude de potentiels mécanismes de régulation épigénétique et (4) d’un potentiel rôle du cerveau dans l’inversion sexuelle par les hautes températures. Une expérience de preferendum thermique a permis de montrer que des juvéniles à génotype sexuel XX choisissaient volontairement des températures masculinisantes, ce qui entraine une déviation du sexe ratio de la population. Cela donne du poids quant à l’existence du phénomène de masculinisation par les hautes températures dans le milieu naturel. Des études d’inversion sexuelle thermique tardive sur des individus à génotype sexuel YY ont permis de remettre en évidence un phénomène de féminisation par les hautes températures, ce qui pousse à développer un modèle plus complexe pour expliquer l’intégration du signal température lors du déterminisme du sexe chez O. niloticus et a amené à intégrer la féminisation par les hautes températures aux différents axes de recherche de ce travail. Lors des différentes expériences d’inversion sexuelle thermique, il a été observé que les répétitions d’un croisement identique donnaient des progénitures avec une réponse variable à la température. Il a également été observé que l’origine du mâle utilisé (inversion spontanée, thermique ou hormonale) a une influence sur la thermosensibilité de la progéniture. Ces deux observations ont mené à l’hypothèse de l’implication de mécanismes épigénétiques dans l’inversion sexuelle à la haute température. Le méthylome des gonades d’individus XX et XY à 15 jpf et 40 jpf a donc été étudié par séquençage Oxford Nanopore Technology®. Aucune différence de méthylation des gènes connus pour être impliqués dans le déterminisme du sexe n’a été observée dans le cadre de notre étude. Des différences de méthylation dans des gènes impliqués dans le métabolisme ont cependant été mises en évidence. Le transcriptome des gonades et des têtes à 15 jpf et à 40 jpf d’individus XX et XY élevés en condition contrôle (28°C) et en traitement par la haute température (36,5°C) a été analysé par RNA-seq dans le but de trouver des gènes cibles impliqués dans la masculinisation et dans la féminisation par les hautes températures. Beaucoup de gènes cibles ont été identifiés et des critères de sélection ont été appliqués pour identifier les gènes d’intérêt les plus pertinents. Dans les gonades, foxl2, un gène codant pour un facteur de transcription activateur de la voie de la stéroïdogenèse femelle a pu a été identifié comme étant sous-exprimé lors de la masculinisation et surexprimé lors de la féminisation. Dans les têtes à 15 jpf, il a été observé que le gène dbi était surexprimé lors de la masculinisation et sous-exprimé lors de la féminisation. Ce gène code pour plusieurs neuropeptides potentiellement circulants qui sont connus pour être impliqués dans l’import de cholestérol dans les mitochondries, qui est la première étape de la stéroïdogenèse. La mise en évidence de dbi[2] dans les têtes couplées aux résultats d’inversion thermique précoce, aux déplacement précoces des juvéniles vers les hautes températures dans l’expérience de preferendum thermique et à la remise en évidence de la féminisation nous ont amenés à émettre l’hypothèse de l’implication du cerveau dans l’intégration du signal température. Pour illustrer cette hypothèse, nous avons développé un modèle général en 3 parties : (1) l’intégration du signal par le cerveau, (2) le moyen de communication entre le cerveau et les gonades et (3) la réponse spécifique de la gonade entrainant la différenciation sexuelle. En conclusion, ce travail a permis de mieux caractériser certains phénomènes liés à l’inversion sexuelle chez le tilapia du Nil, mais aussi de trouver, par des études de séquençage à haut-débit, de nouveaux gènes cibles dont l’étude approfondie permettraient de mieux comprendre l’intégration du signal température lors du déterminisme sexuel de O. niloticus. [less ▲]

Detailed reference viewed: 65 (13 ULiège)
Full Text
See detailLA GESTION DES EAUX, CONDITION D’ÉQUILIBRE DE L’HABITAT COLLINAIRE. KINDELE (KINSHASA)
Kaleka N'Kole, Emeritte ULiege

Doctoral thesis (2021)

The research focuses on the description of the habitability conditions of a portion of peri-urban territory of the city of Kinshasa (DRC): the spontaneous tissues of the KINDELE valley in the municipality ... [more ▼]

The research focuses on the description of the habitability conditions of a portion of peri-urban territory of the city of Kinshasa (DRC): the spontaneous tissues of the KINDELE valley in the municipality of Mont-Ngafula. This sensitive environment, subject to erosion phenomena, constitutes both the ground for a participatory process, led by the author, and a re-reading of the plot system and existing habitats. The building, mostly built spontaneously on unstable clay-sandy soil, worsening the natural erosive nature of the site by its very presence, but also by the increase in phenomena related to water runoff (rain or related to activity ), has been the subject of observations and general surveys making it possible to establish relationships between the site and the existing natural risks. The thesis outlines ways of reflection and action to make the erosion risk understandable and sharpen the ability of inhabitants to establish and manage their buildings in line with natural constraints: simple and robust techniques firstly allowing to restore the capacity to "do together " – bomoko – and, if possible, " to do with nature ", that is to say by reorienting the use of the" soil, water and plant cover system ". The thesis thus intends to propose regional developments responding to the societal, economic and ecological challenges of KINDELE, in line with local governance. [less ▲]

Detailed reference viewed: 40 (6 ULiège)
Full Text
See detailReinventing wildlife census with unmanned aerial systems: new survey designs for ungulate counts in the vast African semi-open ecosystems
Linchant, Julie ULiege

Doctoral thesis (2021)

As the Earth has entered the new Anthropocene Era due to the major human- driven environmental changes, human impact on biodiversity has triggered the planet’s sixth mass extinction. Most terrestrial ... [more ▼]

As the Earth has entered the new Anthropocene Era due to the major human- driven environmental changes, human impact on biodiversity has triggered the planet’s sixth mass extinction. Most terrestrial vertebrate populations have shown a sharp decline in abundance and range. The vast (semi-)open ecosystems of Sub- Saharan Africa have among the most incredible mammal richness in the world, including many large ungulates species. Unfortunately, many are threatened by increasing human pressures. Natural ecosystem conservation requires adaptive management, supported by key elements such as regular wildlife abundance surveys. In large areas, aerial surveys with light aircraft generally remain the best alternative for counting large mammals. However, it presents a lot of challenges inherent to plane logistics and heavy costs. In this context, technological progress such as the availability of small Unmanned Aerial Systems (UASs) can be a powerful tool to help preserve and monitor ungulate populations. UASs exhibit high spatial and temporal resolution, and are safer and often less intrusive than manned airplanes. However, the range of small affordable UASs is generally too short for large-scale application of the traditional aerial surveys. The large amount of images collected is also difficult to manage and has impacted developments. In order to enable this emerging technology so that it can become fully operational for large game counts, the aforementioned issues must be addressed. Therefore, this thesis aims to develop and implement new sampling and counting methods with small UASs in order to facilitate regular censuses of large terrestrial African ungulates. The specific objectives are: (i) to design an innovative flight plan and sampling protocol for large ungulates counts (which will be adapted to small UAS constraints, and have relevant statistical performances in regard to the current standard transect sampling method); and (ii) to investigate the potential of UAS imagery to count precisely the often disregarded, partially submerged, hippopotamus populations. First, we identified the opportunities and limits of UASs use in wildlife monitoring based on a review of the available literature (Chapter 2). We describe the range of available models and sensors used by researchers and provided evidence that most studies focused on optical imagery and used small affordable UASs for a wide range of tasks. We focused on detection possibilities and the types of survey plans performed, and the contributions towards anti-poaching surveillance. Our findings indicate that the main drawback preventing UASs from becoming an effective alternative for large-scale censuses is the generally low flight endurance ultimately limiting the area covered. We identified research gaps in terms of innovative sampling methods and the availability of appropriate statistical approaches. To address the issue of managing the large datasets produced by drone flights, and help reviewing thousands of aerial images manually, we developed a user-friendly interface called WiMUAS (chapter 3). An image viewer allows multiple observers to annotate various observations as well as compare counts. The software can generate maps of the projected observations and sampling strips based on telemetry data and payload parameters for any type of flight plan. We tested it on more than 5000 images from flights performed in Garamba National Parc v savannahs. We assessed that flying at 100 m is the best compromise between resolution and surface covered to detect accurately the main medium- to large-sized antelopes. Then, we evaluated the relevance of a new sampling method adapted to small UAS limitations to census large African ungulates (chapter 4). We identified that a multiple rosettes flight plan based on the UAS operational range could be more efficient in terms of logistics. We showed by numerical simulations that four aggregated repetitions of the rosette flight plan can give accurate density estimates with a coefficient of variation under 15 % for antelope populations. However, the precision remains low compared to classic transect sampling with manned aircraft. We further identified the impact of gregariousness on density estimates by modeling population distribution for both buffalo herds and the more randomly dispersed antelopes, and concluded the lower sampling rate of the rosette design is unsuited for highly aggregative species. Second, we focused on optimizing the detection of hippos for total counts. We assessed the environmental and flight parameters influencing counts accuracy based on 252 RGB photos taken over two large well-known hippo schools (chapter 5). Eight observers reviewed the images, and the observer's experience had a significant impact on detection probability. Of environmental parameters, sun reflection on water had the worst effect on detection, with cloud cover showing a slight impact and wind speed no influence. Altitude up to 250 m did not have a significant impact on the counts, however it affected observers' confidence in their observations. We calculated correction factors that account for hippos' regular diving behavior and found it similar to previous studies. As counting individuals in dense pods proved tedious and highly impacted by the observers' personal capabilities, we used hippos as a case study to develop an algorithm for an automatic count (chapter 6). TIR imagery provided very clear and contrasting images of hippo schools at several flight heights, ranging from 38 to 155 meters above ground level. The algorithm was based on pixel value thresholding and generation of isolines and polygons, and required images to be cut to show only the group of hippos, as surrounding objects interfered with the detection. Estimated automatic counts showed very similar results to visual counts. However, hippos sometimes appeared cut in multiple polygons as they are partially submerged, which is not always addressed adequately by the algorithm. Finally, we summarized our conclusions of the main results achieved regarding new wildlife census methods with UASs (chapter 7). Following our findings, we discussed the practical implications for using UASs in the field of wildlife monitoring in general, and shared some relevant experiences and points of awareness regarding operations, especially under the challenging context of remote protected areas in tropical environments. We drew attention to the social implications of drones and underlined the importance of stringent legislation. We addressed the remaining crucial endurance limitation of the technology for large- scale wildlife aerial censuses and discussed a potential alternative with sensors mounted on ultralight aircraft to combine low costs and efficiency. Lastly, we developed perspectives to handle the large amount of data produced by drone surveys and concluded that automatic detection with machine learning will likely be one of the most important developments required for the future. [less ▲]

Detailed reference viewed: 104 (15 ULiège)
Full Text
See detailLes conceptualisations des nouvelles formes d'emploi. Un parcours réflexif.
Florin, Louis ULiege

Doctoral thesis (2021)

Sous l’effet de changements sociétaux, technologiques et économiques au cours des dernières décennies. On assisterait à un développement sans précédent des nouveaux arrangements de travail, créant une ... [more ▼]

Sous l’effet de changements sociétaux, technologiques et économiques au cours des dernières décennies. On assisterait à un développement sans précédent des nouveaux arrangements de travail, créant une sorte de zone grise entre travail salarié et indépendant. Alors que la demande et le besoin d’information sur ces formes de travail grandit, les statistiques publiques concernant le marché du travail ne permettraient guère d’objectiver le phénomène, poussant dès lors les chercheurs à suggérer de nouvelles approches statistiques. Au travers de trois articles faisant discuter des approches sociologiques assez différentes, de la sociologie quantitative à l’analyse de discours, de la sociologie de l’emploi à la sociologie des sciences et de la quantification, nous arrivons à des résultats complémentaires nuançant en premier lieu les approches binaires des Nouvelles Formes d’Emploi (NFE), montrant les liens entre récits politiques et conceptualisations et suggérant des pistes de compromis et leviers potentiels pour améliorer la soutenabilité de ces formes de travail. En montrant le lien entre savoir expert, instruments statistiques, récits et modes d'action politiques et usages sociaux des statistiques, nous montrons comment le monde du travail s'autodécrit comme en mutation et participe à construire cela comme une évidence au travers de nouvelles catégories statistiques et de récits politiques. Ce travail montre ainsi qui a du poids dans l’institutionnalisation de cette réalité du monde du travail et permet de poser la question de ce qui est visible ou non quand on invente des catégories ainsi qu'ouvrir la voie à des récits et conceptualisations alternatives. [less ▲]

Detailed reference viewed: 30 (8 ULiège)
Full Text
See detailCharacterization of the alterations of the respiratory microbiota and investigation of lung macrophage clusters involved in canine idiopathic pulmonary fibrosis
Fastrès, Aline ULiege

Doctoral thesis (2021)

Canine idiopathic pulmonary fibrosis (CIPF) mainly affects middle-aged to old dogs from the West Highland white terrier (WHWT) breed. CIPF is a chronic disease characterized by collagen deposition in the ... [more ▼]

Canine idiopathic pulmonary fibrosis (CIPF) mainly affects middle-aged to old dogs from the West Highland white terrier (WHWT) breed. CIPF is a chronic disease characterized by collagen deposition in the pulmonary interstitium inducing progressive airway failure. Despite numerous investigations, the aetiology of the disease remains unknown, the diagnosis difficult, the pathophysiology misunderstood and the prognosis poor. Currently, there is no curative therapeutic option for that condition and only symptomatic treatments can be used to maintain a quality of life as good as possible for the dogs. CIPF is frequently equated with human idiopathic pulmonary fibrosis (IPF), although the diseases are not strictly identical. This project was therefore conducted in order to increase pathophysiological knowledges on CIPF and more precisely the ones related to the lung microbiota (LM) and bronchoalveolar lavage fluid (BALF) macrophage clusters. Indeed, macrophages are critical mediators of innate immune responses against bacteria in the lung. They are able to polarize and modulate their phenotypes (inflammatory or pro-fibrotic) to adjust to the microbial environmental conditions. Moreover, recently, studies about IPF have shown that the LM and its impact on the immune system, especially lung macrophages, could have a link with the development, the maintain and the exacerbation of the disease, providing perspectives for designing novel therapeutic strategies. Before assessing the LM in CIPF, we described the LM in healthy dogs and determined the principal factors potentially able to alter it in healthy conditions, including antimicrobial treatment, age, breed and living conditions. As WHWTs affected with CIPF are frequently referred under antimicrobial drug, we first investigated the short and long-time impact of such treatment on the LM in healthy experimental beagles. We showed that before drug administration, the LM is quite similar among dogs with the predominance of 4 phyla: Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria. A 10-days oral amoxicillin-clavulanic acid administration induces alteration of the global diversity and the composition of the LM. However, changes nearly disappear 16 days after discontinuation of the drug. The impact of the living conditions and the breed on the LM have then been assessed by comparing different dogs’ breeds (terriers, WHWTs, beagles, brachycephalic dogs and shepherds) living in different conditions (domestic or experimental). We showed that LM is significantly different depending of the living condition of dogs, while breed has a milder impact. In adult dogs, age doesn’t seem to have an impact on the LM. A core microbiota has been proposed by regrouping data of all published studies related to the LM in healthy dogs and is composed by at least Cutibacterium, Streptococcus, Acinetobacter and Pseudomonas genera. In acute respiratory diseases and particularly in dogs affected with Bordetella bronchiseptica, we showed that 16S rDNA sequencing (the technique used to assess LM) results correlate with results of classical techniques used to assess bacterial infection in the lung (i.e. polymerase chain reaction and culture). This suggests that the 16S rDNA sequencing is reliable for identifying bacteria involved in canine lung infectious diseases, mainly when rare or slow growing bacteria are concerned. A dysbiosis of the LM is also described in the dogs affected with bordetellosis characterized by a domination of one or two bacteria, a reduction of the diversity and the richness, and a higher bacterial load compared with healthy aged-matched dogs. Lastly, we showed that the LM between healthy WHWTs and WHWTs affected with CIPF is quite similar. Brochothrix, Curvibacter, Pseudarcicella, a genus belonging to Flavobacteriaceae family, Rhodoluna and Limnohabitans genera are increased in WHWTs either healthy or diseased compared with healthy dogs from other breeds. Brochothrix, Pseudarcicella, Curvibacter and a genus belonging to Flavobacteriaceae family are also more abundant in CIPF than in healthy WHWTs, however, not significantly. We therefore conclude that the presence of a specific LM in WHWTs compared to other breeds may be suspected to be one of the factors that can predispose that breed to CIPF. In the second part of the thesis, the use of the single-cell mRNA sequencing technique (scRNA-seq) was first validated in the BALF from healthy dogs. ScRNA-seq is an unbiased and high throughput tool that enables the transcriptomic identification of thousands of single cells at a time and that has never been used in dogs before. By using this technique, we found 14 conserved clusters in the BALF of healthy dogs corresponding to 8 different cell populations: macrophages, lymphocytes, neutrophils, dendritic cells, B cells, mast cells, epithelial cells and cells in division. The scRNA-seq was then used to identify macrophages clusters in WHWTs affected with CIPF compared with healthy WHWTs. In all WHWTs, the same cell populations as described in the previous study were identified. Five clusters of macrophages were found. Among them, two were enriched in pulmonary fibrosis processes compared with other clusters, a cluster of monocytes and a cluster of monocytes-derived macrophages. Pro-fibrotic genes overexpressed in monocytes and monocytes-derived macrophages included CCL2, SPP1, FN1, CCL3, TIMP1, IL1RN, CXCL8 and CCL4, and SFTPC, CCL5, FN1, CXCL8, ATP11A and SPP1, respectively. The differential gene expression in monocytes was not different between CIPF and healthy WHWTs. However, significantly more cells from this cluster were identified in CIPF dogs. Monocytes-derived macrophages were enriched in pulmonary fibrosis but also in angiogenesis and epithelial-mesenchymal transition processes in CIPF compared with healthy WHWTs. Four pro-fibrotic genes were overexpressed in CIPF compared with healthy WHWTs in that cluster including FN1, SPP1, CXCL8 and PLAU. The presence of those pro-fibrotic macrophage clusters in diseased WHWTs probably participates to the onset and/or the perpetuation of CIPF. In conclusion, this project allowed to better describe the LM in healthy dogs and its modifications in WHWTs affected with CIPF in comparison with other lung pathological conditions. The use of the scRNA-seq in dogs’ BALF, after validation revealed the presence of pro-fibrotic macrophage clusters in CIPF compared with healthy WHWTs. Overexpressed pro-fibrotic genes identified in CIPF WHWTs might be used as biomarkers or be targeted for therapeutic treatment, which offers good perspectives for future research about CIPF. [less ▲]

Detailed reference viewed: 69 (9 ULiège)
Full Text
See detailEfficiency, Risk and Competition in Banking : Essays from Africa
Matabaro, Borauzima Luc ULiege

Doctoral thesis (2021)

Over the last decades, the banking market has experienced various changes including the expansion of cross-border banks (CBBs) in developing banking markets. This expansion has raised questions related to ... [more ▼]

Over the last decades, the banking market has experienced various changes including the expansion of cross-border banks (CBBs) in developing banking markets. This expansion has raised questions related to CBBs’ effects on incumbent banking markets. Although the existing literature has explored a number of these questions, there is still a lack of or a limited evidence on how to account for efficiency heterogeneity among banks when CBBs establish and how they affect less competitive and inefficient developing banking markets. This thesis investigates how changes induced by CBBs’ expansion affect efficiency, risk-taking and competition in developing banking markets, by focusing on Africa where cross-border banking (CBB) has shown an unprecedented upward trend over the last two decades. In the first part of this thesis, we account for efficiency heterogeneity among banks to examine how CBB affects the market structure and the performance in domestic markets. Using classical Cournot and Stackelberg oligopolies, we show that although more efficient outperform less efficient banks when competition increases, they alleviate the competition induced by CBB. Empirical results indicate that African CBBs are more advantageous to competition while non-African CBBs exhibit higher efficiency and mitigate the magnitude of competition. Moreover, a cross-country heterogeneity investigation suggests that the effects of CBBs are more significant in Sub-Saharan than in North African banking markets. In the second part, we explore how competition induced by CBBs affects bank risk-taking and implicitly the probability of bank failure when banks are heterogenous in terms of cost efficiency. By the mean of the Vasiceck single factor model and by introducing efficiency in the bank’s payoff function, the study confirms the nonlinear nexus between competition and bank risk-taking. It shows that efficiency moderates the effect of competition on bank risk-taking. Empirical evidence from African banking unveils that although efficiency mitigates the effects of competition on bank risk-taking, banks have to achieve reasonable cost efficiency levels. Moreover, the study shows that the penetration of African CBBs does not increase risk-taking in incumbent markets. Finally, based on a panel VAR analysis, this thesis examines the reverse causality between bank efficiency and market structure. It reveals that efficiency better predicts the market structure and that unlike cost and profit efficiency, a shock in technical efficiency negatively affects the bank market structure. [less ▲]

Detailed reference viewed: 47 (10 ULiège)
Full Text
See detailSingle-cell toolbox for optimizing the production of recombinant proteins by E. coli
Nguyen Minh, Thai ULiege

Doctoral thesis (2021)

Phenotypic heterogeneity provides the microbial population with fast adaptive response (i.e., in the range of several minutes) against various kinds of stress factors, mainly for improving the natural ... [more ▼]

Phenotypic heterogeneity provides the microbial population with fast adaptive response (i.e., in the range of several minutes) against various kinds of stress factors, mainly for improving the natural fitness of the microbial population in the presence of environmental fluctuations. The stability and reproducibility of such productive phenotype became more critical when applying continuous cultivation in industrial production. Here we report using a single-cell toolbox to study the impact of nutrient fluctuations on microbial population dynamics, and this platform can be used to ensure the long-term stability of phenotypic diversification. The setup, design, and operation of the so-called segregostat combined with an automated sampling platform and online flow cytometry were developed in order to implement real-time analysis and feedback control with a very high time resolution. This closed-loop controller is able to drive phenotypic diversification employing defined pulse-frequency modulation within continuously running bioreactor setups. Two exemplary case studies have been discussed, i.e., phenotypic diversification dynamics based on outer membrane permeabilization and the response of a coherent feedforward loop motif in E. coli, highlighting the applicability and flexibility of the proposed approach. In the first case, glucose pulses were added to maintain a predefined diversification ratio between non-permeablized and permeabilized cells based on an exogenous biomarker (propidium iodide). Our segregostat platform offered the possibility to adjust the environmental fluctuation profile based on the state of the population and automated this dynamic control in real-time. The second case study was focused on the induction of the arabinose operon as a model system; the GFP level prompted by an arabinose-inducible promoter has been tracked by flow cytometry. The bimodal distribution in the GFP expression pattern and the co-existence of GFP positive and negative subpopulations were observed in the glucose/arabinose co-feeding chemostat. Furthermore, adjusting the arabinose/glucose transitions based on the phenotypic switching under a bang-bang controller provides a fully predictable, but oscillatory, gene expression dynamics. Forcing the expression level of the arabinose system by increasing the inducer stimulation frequency led to harmonic oscillation, a more homogenous response of the cell population, and alleviated the bimodal behavior in gene expression. Such dynamic control could enable the repeated and reversible switching between two gene expression states, allowing individual cells to switch around a predefined threshold. Periodic inducer addition could be applied in bioprocesses for driving microbial population into a predefined phenotypic trajectory. Taken altogether, these results pointed out that our control platform is a major step in quantitatively controlling phenotypic heterogeneity among microbial population. [less ▲]

Detailed reference viewed: 57 (17 ULiège)
Full Text
See detailMulti-period distribution network problems with minimum commitment contracts
Clavijo Lopez, Christian Javier ULiege

Doctoral thesis (2021)

Companies outsourcing road freight transportation services approach their procurement plan based on a combination of long-term annual contracts with dedicated carriers and spot-markets for immediate loads ... [more ▼]

Companies outsourcing road freight transportation services approach their procurement plan based on a combination of long-term annual contracts with dedicated carriers and spot-markets for immediate loads. This thesis proposes an integrated planning framework considering tactical and operational decisions for logistics services procurement. It allows individual shippers to formulate mid-term contractual agreements with several transporters that could reduce some of the risks encountered in shipper-carrier business relationships, such as unavailability of transportation resources and high-market prices. [less ▲]

Detailed reference viewed: 70 (14 ULiège)
Full Text
See detailMultimodal Imaging In Parkinson’s Disease: Exploring Iron–, Neuromelanin-Sensitive MRI And FDOPA PET Relationships
DEPIERREUX, Frédérique ULiege

Doctoral thesis (2021)

This thesis explores the relationships between different imaging modalities (namely FDOPA PET, Neuromelanin-sensitive MRI, Iron-sensitive MRI) and how they could reflect the neuropathological processes ... [more ▼]

This thesis explores the relationships between different imaging modalities (namely FDOPA PET, Neuromelanin-sensitive MRI, Iron-sensitive MRI) and how they could reflect the neuropathological processes underlying Parkinson's disease. [less ▲]

Detailed reference viewed: 89 (6 ULiège)
Full Text
See detailSourcing and dynamic of mercury in Arctic true seals
Pinzone, Marianna ULiege

Doctoral thesis (2021)

Mercury (Hg) is considered one of the top 10 chemicals of modern public health concern. After the implementation of the Minamata convention in 2017, efforts were mostly directed to the understanding of Hg ... [more ▼]

Mercury (Hg) is considered one of the top 10 chemicals of modern public health concern. After the implementation of the Minamata convention in 2017, efforts were mostly directed to the understanding of Hg cycling in marine environment impacted by climate change. The Arctic region is a hotspot of Hg contamination studies, being a major sink and source for the global Hg cycle. Although evidences exist about a shift in Hg bioaccumulation in Arctic wildlife over time, scientists were not able to effectively link it with climate change. The remote position of some regions of the Arctic brought to a paucity of data. For example, Total-Hg (THg) temporal and spatial trends in marine and terrestrial predators living in the Greenland Sea are wildly missing. Forecasting of future THg trends is especially important for Arctic marine predators like marine mammals, whose Hg concentrations often surpass suggested toxicological thresholds. The assessment of Hg sources and pathways in the marine environment, remains a complex challenge despite its recognized toxicity, both for wildlife and humans. Stable isotope ratios of carbon (C), nitrogen (N), sulphur (S) and Hg are valid tracers of Arctic marine predators’ trophic ecology, as well as Hg sourcing and cycling in the ocean. They are often studied separately, leaving the interpretation of the data at times incomplete and limiting the understanding of the complexity of the natural world. The main goal of this work was to understand the main factors governing Hg pollution of marine predators in a changing Arctic. We focused on Greenland Sea true seals because of their diverse trophic ecologies and distribution. The hooded seal Cystophora cristata, harp seal Pagophilus groenlandicus and the ringed seal Pusa hispida are the most common specie in the area. As such they represent the main food source of local apex predators like polar bears and humans. We applied a multivariate approach integrating C, N and S stable isotopes as proxies of seal ecology, Hg stable isotopes as proxies of Hg sources and Hg concentrations as proxies of levels of exposure. We set 3 specific questions: (1) which are the main sources of Hg in Arctic marine predators? (2) Which factors influence the most Hg bioaccumulation and biomagnification in Arctic marine food webs? And (3) Which consequences can be drawn for the health of Arctic marine food webs in the framework of climate change? Our main findings indicate that (1) local Hg sources are far more important in governing Hg bioaccumulation and biomagnification in Arctic marine food webs, than environmental Hg levels; and (2) while environmental change at global levels is determining a decrease in Hg emissions and accumulation in marine species from oceanic food webs, ongoing changes across Arctic coasts are enhancing the risk of Hg exposure to inshore food webs. [less ▲]

Detailed reference viewed: 98 (10 ULiège)
Full Text
See detailLand-use effects on soil quality of agricultural systems in the Central Andes of Bolivia
Coca Salazar, Alejandro Ariel ULiege

Doctoral thesis (2021)

Increasing demands for food of the growing world population has led to agricultural intensification and rapid changes in land use worldwide. Resulting modifications of soil characteristics could have ... [more ▼]

Increasing demands for food of the growing world population has led to agricultural intensification and rapid changes in land use worldwide. Resulting modifications of soil characteristics could have cascading effects on soil functioning and the delivery of ecosystem services (e.g. food production). Maintenance of soil quality, the capacity of a soil to function to sustain biological productivity while maintaining environmental quality, is thus of central importance in order to ensure long-term provision of food, and its evaluation allows to understand the soil responses and to predict potential consequences of land-use changes. Over the last decades, agricultural systems of the Central Andean region of Bolivia have experienced rapid changes of land use and management practices such as shortening of fallow periods, use of chicken manure fertilization to improve soil fertility, and the plantation of Eucalyptus globulus L. on arable soils. So far, the effects of these changes on soil quality have not been assessed. Improving agricultural production while contributing to sustainability of these ecosystems requires soil quality evaluations under the current land uses. This thesis evaluated the effect of fields cultivated with potato, fallow fields (2-6 years old), eucalyptus plantations, and the use of chicken manure for fertilization on soil quality in agricultural ecosystems of the Central Andes. The combined responses of soil physico-chemical properties, soil aggregates, microbial processes, and their interactions were evaluated as indicators of soil quality. Short-term fallowing did not contribute to soil fertility restoration or soil structure improvement, indicating a neutral effect on soil quality compared to fields cultivated with potato. However, fallowing soils lead to reduced net nitrogen transformation rates and lower abundance and activity of ammonia oxidizing bacteria, suggesting sensitivity of these processes to land-use change. Fertilization with chicken manure improved soil quality by increasing labile carbon and nitrogen fractions and microbial activity. Manure also promoted seed germination and plant growth, however, immature manure caused root damage on Avena sativa L. seedlings. Turning manure piles accelerated the composting process and reduced root damage. It is recommended to compost manure for 100 days and to conduct turning events to reduce the risk of manure phytotoxicity. The plantation of eucalyptus promoted organic matter accumulation, and increased the total amount of carbon in different fractions. Soil structure was also improved and contributed to carbon stabilization. These changes are commonly associated with an improvement of soil quality for cultivation, but increased exchangeable Al and potential allelopathic interactions reduced biological soil quality compared to cultivated fields (reduced metabolic potential of soil bacteria, N transformation rates, and increased microbial energy maintenance demands) The plantation of eucalyptus should be avoided in agricultural areas, and careful land-use planning should guide its plantation to avoid negative effects on crops. Under the three land uses, ammonia-oxidizing archaea were dominant nitrifying organisms in terms of abundance and activity, but the contribution of ammonia-oxidizing bacteria to nitrification significantly increased with pH. We have also demonstrated that the activity of ammonia oxidizers should not be inferred from amoA gene abundances alone, but that their nitrification rates should be measured separately to determine their role in the environment. Labile carbon fractions (hot water extractable carbon and microbial biomass carbon) were strongly associated to microbial processes and were sensitive to land-use changes. Moreover, increases in microbial activity (respiration potential and net nitrogen mineralization) were associated to aggregate formation and stability. Labile carbon fractions and microbial processes should be considered for monitoring soil quality in response to land-use change and agricultural practices. This study demonstrated that the short fallow periods did not contribute to soil quality improvement for cultivation compared to fields cultivated with potato. The use of composted chicken manure for fertilizing soils improved to soil quality for agricultural production but the use of immature manure should be avoided to reduce the risk of phytotoxic effects. The introduction of eucalyptus to the Andean agricultural systems reduced soil quality for cultivation compared to fields cultivated with potato. Labile carbon fractions and microbial processes stand out as sensitive and informative soil quality indicators of the early changes occurring in these agricultural systems following land-use change. [less ▲]

Detailed reference viewed: 46 (1 ULiège)
See detailClinical Behavior and Intraoral Low-Temperature Degradation of Zirconia Dental Prostheses
KOENIG, Vinciane ULiege

Doctoral thesis (2021)

The use of zirconia in the field of dental prostheses has grown significantly since its introduction in the 2000s, following the advent of computer-aided design and manufacturing technologies. First ... [more ▼]

The use of zirconia in the field of dental prostheses has grown significantly since its introduction in the 2000s, following the advent of computer-aided design and manufacturing technologies. First-generation zirconia-based restorations (ZBR) are bilayered structures composed of a framework and a glass-ceramic veneer, which imparts an essential esthetic appearance. However, the first clinical reports regarding veneered ZBR indicated a high rate of short-term failures due to cohesive fractures (chipping) of the veneering ceramic. To address this, a retrospective study on veneered ZBR was conducted to investigate the influence of clinical parameters, such as patient-related risk factors, on chipping failures. Zirconia is now used to fabricate monolithic dental prostheses without the veneering ceramic layer and the only presence of a thin cosmetic glaze. These prostheses were notably developed to remedy chipping and, thus, obtain prostheses with an increased durability. Therefore, zirconia materials exhibiting greater translucency have been developed for monolithic restorations. However, second-generation zirconia materials are prone to show greater metastable behavior, which could promote low-temperature degradation (LTD). The main objective of this study was to evaluate the intraoral LTD of zirconia monolithic restorations and the influence of occlusal stresses and glaze protection on this process. Secondary objectives included the investigation of the general clinical behavior and material wear of the restorations. This work introduces an original protocol, including ex vivo analyses, to evaluate the LTD process of monolithic zirconia prostheses in the oral environment and to study their general clinical behavior, primarily in terms of material wear. LTD was shown to develop in 3 mol% yttria-doped tetragonal zirconia polycrystal monolithic restorations six months after intraoral placement and then progresses over time. After two years, the tetragonal-monoclinic transformation became non-uniform, with the presence of localized clusters of transformed grains. In axial areas, the grain aspect was typical of the classical nucleation-growth process reported for LTD. However, in occlusal areas, tribological stress generated surface crushing and grain pull-out from the clusters, causing an underestimation of the aging degree when the evaluation was limited to monoclinic phase quantification. Glazing cannot be considered a protection against LTD because it is worn away in occlusal areas after one year. Two years after their implantation, the Kaplan-Meier survival rate of restorations was 93.3% (100% for fixed partial dentures) and the success rate was 81.8%. It was found that eighty percent of major failures occurred in patients exhibiting clinical signs of bruxism. Complications such as root fracture, periodontal disease or composite chipping were also observed in antagonistic teeth. Wear in zirconia was observed to be less than 15 μm. The success rate of single-unit restorations was not as high as expected, the weak link being the prosthesis support or the antagonist tooth. One hypothesis is that zirconia’s stiffness and lack of ability to deform do not promote occlusal stress accommodation, which can be critical in patients affected by bruxism. Furthermore, several unexpected clinical failures were observed, including chipping and major fracture of the material, which may have been induced through LTD. If LTD occurs through the same mechanisms in dental prostheses as in orthopedic prostheses, its clinical impact remains unknown and needs to be evaluated through a thorough analysis of fractured prostheses in the framework of long-term studies. [less ▲]

Detailed reference viewed: 29 (1 ULiège)
See detailInfluence du microenvironnement pulmonaire sur l’implantation de métastases
BEKAERT, Sandrine ULiege

Doctoral thesis (2021)

Detailed reference viewed: 28 (1 ULiège)
Full Text
See detailSoil organic carbon sequestration and its synergetic effect on crop yield in cropland under different fertilizations
Xu, Hu ULiege

Doctoral thesis (2021)

Under the dual pressure of food demand growth and climate change intensification, how to promote soil organic carbon (SOC) sequestration and synergistically improve crop production via agricultural ... [more ▼]

Under the dual pressure of food demand growth and climate change intensification, how to promote soil organic carbon (SOC) sequestration and synergistically improve crop production via agricultural practice is not only a major strategic demand to ensure food security but also a key way to implement the "Four Per Mille Initiative" and "Carbon Neutrality". Fertilization, especially adding organic amendment, is the most effective practice to enhance SOC, but limited information is available on the underlying mechanism of SOC sequestration in intensive cropping systems. Moreover, in recent years, the application practices of both traditional (e.g., straw incorporation and organic substitution (substitution of chemical fertilizers by manure)) and emerging (e.g., biochar application) organic amendment have shown a great potential in enhancing crop yield and SOC. However, an understanding of how and to what extent organic substitution and straw incorporation impact SOC at different depths and crop yield remains limited. Moreover, previous results regarding the effects of biochar application on SOC and crop yield showed wide variation and high uncertainty. Therefore, it is essential to enhance the understanding of SOC sequestration mechanisms and crop yield response to those practices. In this thesis, firstly, we used a field experiment with double maize cropping to study the responses of OC in soil fractions to long-term fertilization and revealed the underlying mechanism of SOC sequestration in intensive cropping systems. Secondly, four organic substitution and one straw incorporation field experiments were conducted in China to quantify the effects of these practices on SOC at different depths and crop yield as well as their relationship. Finally, the effects of biochar application, as a new perspective of fertilization strategy evolution, on SOC and crop yield were evaluated via a global meta-analysis, and their key factors were determined using a boosted regression tree model. [less ▲]

Detailed reference viewed: 138 (38 ULiège)
Full Text
See detailBringing proteomics discovery studies towards clinical application requirements: guidelines and practical suggestions
Baiwir, Dominique ULiege

Doctoral thesis (2021)

Proteomics is the study of proteome which encompasses the nature and amounts of all the proteins present in a cell, or tissue at a given time and in a given condition. Differential proteomics refers to ... [more ▼]

Proteomics is the study of proteome which encompasses the nature and amounts of all the proteins present in a cell, or tissue at a given time and in a given condition. Differential proteomics refers to the determination of quantitative maps of protein expression from different biological where two or more conditions are compared (relative quantification). One of the main areas of research in quantitative differential proteomics is the discovery of biomarkers. At the biomolecular level, a biomarker is a molecule present at levels significantly different when a change of specific condition of health occurs. Differential quantitative proteomics generates a large list of proteins along with their relative abundances between different conditions and allows the identification of biomarker candidates. However, the approach is not straightforward and not all of the many differentially abundant proteins identified in proteomics studies become biomarkers used in clinical practice. The bottleneck is the reliability of the results of proteomics studies. The objectives of this work were therefore to develop and optimize methods using liquid chromatography hyphenated to mass spectrometry to obtain reliable results from proteomics discovery studies. These reliable results could be better leveraged for future clinical use. Based on the expertise gained, all relevant information is gather in a synthetic manner to draw guidelines, recommendations and practical advices to get reliable proteomics results. [less ▲]

Detailed reference viewed: 61 (11 ULiège)
Full Text
See detailMécanismes cérébraux du traitement incident de l'information sémantique
JEDIDI, Zayd ULiege

Doctoral thesis (2021)

Le réseau sémantique frontopariétal englobant le gyrus frontal inférieur (IFG) et le cortex médio-temporal postérieur (pMTG) est généralement considéré comme impliqué dans les processus de contrôle ... [more ▼]

Le réseau sémantique frontopariétal englobant le gyrus frontal inférieur (IFG) et le cortex médio-temporal postérieur (pMTG) est généralement considéré comme impliqué dans les processus de contrôle sémantique. La nature implicite versus explicite de ces mécanismes de contrôle demeure à ce jour toutefois largement méconnue. Ce travail expérimental a précisément étudié cette question en évaluant la réponse de régions particulières du cerveau vis-à-vis des attributs sémantiques d’un flux de mots présenté de manière détournée à des volontaires sains, alors que leurs ressources attentionnelles (détection visuelle, jugement, contrôle moteur, etc.) étaient monopolisées par une tâche complexe et exigeante basée sur la recherche visuelle. Le caractère spécifique de ces réponses par rapport au contenu sémantique du flux verbal a été établi par un paradigme incident de suppression par répétition en IRMf. Au cours de ce travail, nous avons mis en évidence le fait que le traitement sémantique incident d’une suite de mots passivement entendus a non seulement recruté les cortex unimodaux (‘spokes’) et amodaux (‘hubs’) dans les régions postérieures sous-tendant les connaissances sémantiques, mais également le cortex frontal inférieur et les régions postérieures du cortex médio-temporal considérées comme faisant partie du réseau de contrôle sémantique. Ces résultats soutiennent donc l’idée que le réseau sémantique fronto-temporal est impliqué dans un traitement (et un contrôle) sémantique incident. [less ▲]

Detailed reference viewed: 99 (5 ULiège)
Full Text
See detailThe Effect of Financial Retirement Incentives Originating from the Social Security System on the Retirement Behavior of Older Belgian Workers
Fraikin, Anne-Lore ULiege

Doctoral thesis (2021)

Rapid population ageing and the influx of baby boomers arriving at the age of retirement is generating a considerable threat for the financial sustainability of Belgium’s old-age pension system ... [more ▼]

Rapid population ageing and the influx of baby boomers arriving at the age of retirement is generating a considerable threat for the financial sustainability of Belgium’s old-age pension system. Additionally, the country must cope with relatively low elderly employment rates and one of the earliest average effective retirement ages in the OECD. Concurrently to a trend observed in many developed countries, Belgium has witnessed an upward trend in male employment rates starting in the 2000’s and a long-term structural increase in female employment. While these tendencies in employment show potential for improving the financial sustainability of the pension system, they are in no way sufficient to absorb the overwhelming burden of population ageing on public old age spending. Confronted with these demographic trends, the Belgian government has implemented various social security reforms since the 1990’s to safeguard the financial sustainability of the pension system. These reforms were mainly aimed at tightening access to early labor force exit pathways and at reducing the incentives of early old-age pension benefits claiming. The objective of the thesis is to explore the impact of the social security system as a driver of retirement, using Belgium as a case study. We use detailed social security eligibility and benefit calculation rules and their reforms from the 1980's until today to compute measures of financial retirement incentives and we study their impact on the retirement probability of older Belgian workers. [less ▲]

Detailed reference viewed: 43 (12 ULiège)
Full Text
See detailHow evolved that mouth: a functional morphological approach to unravel the evolutionary history of trophic shift between herbivory and carnivory in Serrasalmidae (Teleostei: Characiformes)
Huby, Alessia ULiege

Doctoral thesis (2021)

In jawed vertebrates, a diet transition between herbivory and carnivory is predicted to result in a change in functional constraints on the feeding system. Curiously, in this context, few studies have ... [more ▼]

In jawed vertebrates, a diet transition between herbivory and carnivory is predicted to result in a change in functional constraints on the feeding system. Curiously, in this context, few studies have explored the phenotypic evolution of the feeding system as an integrated functional system including teeth, bones and muscles. The Neotropical family Serrasalmidae (pacus, piranhas and relatives) is a highly successful group of South American characiform fishes having a large diversity of feeding habits and tooth morphologies. Feeding habits vary from the predominantly frugivorous and granivorous pacus having molariform teeth to the primarily piscivorous piranhas having caniniform teeth. More importantly, serrasalmids are atypical among teleosts because they feed only by biting on various types of plant and animal foods while using only the oral jaw system. All these specificities make serrasalmids the ideal study group to understand how the biting system evolves under a trophic shift, and in particular, how oral teeth, oral jaws and associated jaw muscles evolve in relation to each other. The main objectives of this research thesis were to determine, in a phylogenetic context, the impact of a diet transition between herbivory and carnivory on the feeding performance and functional morphology of the biting system, along with evolutionary patterns of phenotypic integration and modularity between the different dental and musculoskeletal structures of this system in serrasalmids. To this end, we recorded for the first time bite forces in many species of the family, we generated functional and morphological (geometric morphometric) datasets for each structure of the biting system, and we performed the first comparative analysis of function and microstructure of oral teeth between herbivorous and carnivorous serrasalmids. Our results demonstrate that the evolutionary history of serrasalmids is characterized by a main trophic shift from herbivory to carnivory, which is associated with a major phenotypic shift in the biting system enhancing bite performance. Sharper teeth, longer jaws, a jaw joint more in line with teeth and a larger jaw muscle changed the entire configuration of the biting system to generate more efficient and stronger bite forces for animal foods in a scissor-like strategy. In addition to these phenotypic adaptations, our results provide evidence of a shift in tooth attachment and microscopic adaptations at the level of oral teeth. Teeth of piranhas attach by their base to the jawbone to better withstand extreme bite forces and have an increased mineral content that most likely improves their stiffness. Our results also reveal that the biting system evolves as a modular system by having a certain degree of independence between oral teeth, oral jaws and associated jaw muscles. Our results also highlight, for the first time, a sequence of phenotypic adaptations in which oral teeth, oral jaws and then the adductor mandibulae muscle shift in morphology and function. Altogether, our findings suggest that oral teeth might be a key structure in the adaptive evolution of the biting system in serrasalmids in relation to trophic shift. However, their stronger phenotypic integration with oral jaws compared to adductor mandibulae muscle suggest that oral teeth and oral jaws, together, might enable the shift between the herbivorous and carnivorous adaptive zones and ecological diversification within these zones. [less ▲]

Detailed reference viewed: 59 (9 ULiège)
Full Text
See detailUrban flooding modelling: role of geometric distortion in scale models and influence of urban forms
Li, Xuefang ULiege

Doctoral thesis (2021)

Urban flood risk is increasing worldwide as a result of environmental changes such as more frequent hydro-climatic extremes and due to rapid urbanization. Accurate and reliable tools are critically needed ... [more ▼]

Urban flood risk is increasing worldwide as a result of environmental changes such as more frequent hydro-climatic extremes and due to rapid urbanization. Accurate and reliable tools are critically needed for managing this risk and enhancing flood resilience. Such tools rely on numerical models for computing flood hazard and flood risk. However, the accuracy and applicability of these models still remain hampered by a lack of suitable validation data. Data generated from laboratory experiments is a valuable complement to field observations for validating these flood risk management tools. Through a comprehensive review of the 45+ available experimental studies of urban flooding, a few gaps in current experimental knowledge of urban flooding were identified. Firstly, laboratory studies of urban flooding often use geometrically distorted scale models due to the multi-scale nature of these specific flow pattern The possible bias induced by geometric distortion has never been thoroughly investigated with dedicated laboratory experiments. To address this issue, we firstly carried out a preliminary assessment of these biases based on the reanalysis of two recent experimental datasets related to urban flooding. Then, combining two-dimensional numerical modelling and dedicated laboratory experiments, we provided a first systematic quantification of this bias in the case of a synthetic urban layout, involving models at three horizontal scales, models for different geometries and various flooding conditions. The results indicate the direction and magnitude of the bias induced by geometric distortion for a broad range of flow cases, which is valuable for offsetting these effects in practical laboratory studies of urban flooding. Secondly, water-sensitive urban design is an integral part of flood risk management. Based on numerical modelling, we investigated the influence of various urban forms on flood severity at an urban block scale in the case of long-duration urban flooding. The upstream flow depths, downstream discharge partition and flow exchange through the urban forms were examined. Moreover, the computational model was verified against laboratory observations, which constitute a novel valuable dataset for the validation of other urban flooding models. [less ▲]

Detailed reference viewed: 67 (10 ULiège)
See detailApprendre à maitriser la temporalité historienne: étude de l’efficacité d’un dispositif partiellement non chronologique
Pirard, Gaël ULiege

Doctoral thesis (2021)

Résumé : Depuis le XVIIe siècle, l’histoire s’enseigne dans l’ordre chronologique. Il s’agit là d’une tradition encore respectée aujourd’hui en Belgique francophone. Cependant, ces dernières années, des ... [more ▼]

Résumé : Depuis le XVIIe siècle, l’histoire s’enseigne dans l’ordre chronologique. Il s’agit là d’une tradition encore respectée aujourd’hui en Belgique francophone. Cependant, ces dernières années, des débats concernant le meilleur ordre à adopter pour apprendre l’histoire, et plus particulièrement, pour apprendre le temps, ont vu le jour en Belgique. Notre thèse de doctorat a pour objectif de vérifier empiriquement s’il existe, comme l’affirment de nombreux didacticiens, professeurs et acteurs de l’enseignement de l’histoire, un mode de mise à disposition des savoirs enseignés à privilégier pour permettre aux élèves de maitriser certaines dimensions de la temporalité historienne. Pour ce faire, nous avons mené une recherche quasi expérimentale dans laquelle la variable dépendante correspond à la maitrise de la temporalité historienne tandis que la variable indépendante concerne l’organisation des contenus à apprendre (organisation strictement chronologique ou « parcours chronologiques emboités »). Cette recherche a été menée en province de Liège, en Belgique francophone et a porté sur un échantillon d’élèves (n=369) de 3e année secondaire de l’enseignement qualifiant (technique ou professionnel). Notre recherche ne démontre pas une différence significative (p=0,9832) entre les deux modes d’enseignement lorsque l’on tente d’apprendre aux élèves les connaissances procédurales liées aux trois dimensions que nous avons retenues comme constitutives de la temporalité historienne (causes-conséquences, changements-continuités-périodisation et synchronies). Nous avons également observé qu’en moyenne, il existe une faible diminution des résultats entre le pré-test et le post-test dans les deux groupes. Enfin, nous tirons un certain nombre de conclusions par rapport aux variables secondaires influençant le niveau de maitrise de la temporalité historienne chez des élèves de l’enseignement qualifiant. Nous avons ainsi repéré l’existence d’un lien significatif entre le niveau de maitrise de la temporalité historienne de l’élève et son niveau de compréhension à la lecture, sa filière, l’indice socio-économique de son école, son niveau d’intérêt pour l’histoire et la nationalité de sa mère. Abstract: Since the seventeenth century, history has been taught in a chronological order. In this way, it is a tradition still respected nowadays in francophone Belgium. Nevertheless, these last years, debates about the best way to teach history, and more particularly, to teach time in general, have arisen in Belgium. The aim of our thesis is to check empirically if there is, as a lot of professors and professional stakeholders in history and didactic claim it, a way to introduce historical knowledge that we should opt for in order to allow the students to master some dimensions of historical temporality. In that sense, we have led an quasi-experimental research in which the dependent variable is the mastering of historical temporality, and the independent variable is linked to the organisation of historical understanding (strictly chronological organization or « slotted chronological process »). This research has been led in the province of Liege, in francophone Belgium, and has been built on a sample of 3rd year secondary school students (n=369), from the technical and vocational education. Our research does not show a significant difference (p=0,9832) between the two modes of teaching when we try to teach the students the procedural knowledge linked to the three dimensions that we have kept as constitutive of historical temporality (causes and consequences, changes-continuities-periodisations and synchronies). We have also observed that, in average, there is a slight decrease of the results between the pre-test and the post-test in the two groups. Finally, we have come to several conclusions according to the secondary variables which influence the level of mastering of historical temporality for students of technical and vocational education. We have thus spotted the existence of a significant link between the student’s level of mastering of historical temporality and his level of reading comprehension, his pathway, the socio-economic status of his school, his interest in history and his mother’s nationality. [less ▲]

Detailed reference viewed: 43 (4 ULiège)