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See detailIntervenir sur les édifices historiques en Belgique au XIXe siècle
Baudry, Antoine ULiege

Doctoral thesis (2021)

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See detailModelling the hydrodynamics and sediment transport in the Southern Bight of the North Sea for assessing offshore wind farms impacts on the sedimentary environment
Ivanov, Evgeny ULiege

Doctoral thesis (2021)

This PhD thesis is devoted to the study of the environmental impact of artificial marine structures, such as offshore wind farms (OWF), on the bottom deposition of organic and inorganic matter. This study ... [more ▼]

This PhD thesis is devoted to the study of the environmental impact of artificial marine structures, such as offshore wind farms (OWF), on the bottom deposition of organic and inorganic matter. This study aims to connect the local and regional scales using numerical modeling. Living on the foundations of turbines, filter feeders (like the blue mussel) filter suspended particulate matter (SPM) from the water column to produce fecal pellets, rich in carbon, that sink to the bottom. Thus, through biodeposition, fouling organisms living on wind turbines are able to modify the distribution of the carbon flux to the bottom, and the distribution of organic matter and the oxygen consumption in the sediment. Quantification of local effects at the scale of the Southern Bight of the North Sea (SBNS) is necessary within the framework of European strategies of the Blue growth and protection of biodiversity. A hydrodynamic model of the SBNS coupled with a sediment and wave model (COAWST) has been developed. This model has been extended with a model representing the filtration and biodeposition by fouling filter feeders. The model covers the entire SBNS with a coarse resolution (CR) of 5 km while the Belgian coastal zone (BCZ) is covered by a high resolution (HR) model of 1 km. The HR model is forced at the borders by the CR model, while the results of the latter at the level of the BCZ are updated with the results of the HR model. Model simulations of hydrodynamic variables including tides and waves and sediments have been validated against existing data for the region. The impact of variability of atmospheric conditions and tidal regimes on variability of hydrodynamics has been analyzed. This validation effort has shown that the HR model has better performance for the simulation of residual currents, the extension of the river plume and the variability in response to atmospheric forcings and tidal regimes. However, the CR model has better performance for the simulation of overtidal constituents. Regarding the impact of the biodeposition by fouling organisms on the flux of sedimentary particles, it has been shown that the impact of fouling fauna extends beyond the boundaries of the OWFs with an increase in the flux of sedimentary carbon (up to 50%) near (< 5 km) turbines and a slight decrease up to 30 km away. The model has then been used to provide recommendations on the design of a new OWF planned in a new concession area (NCA), located near a site of the Natura 2000 network according to the Marine Spatial Plan 2020. In particular, the impact of the number and position of turbines on the carbon flux to the sediment has been simulated. Placing the NCA turbine foundations over the protected gravel beds of the Natura 2000 network would result in a drastic increase (> 50%) in carbon deposition on them; while if turbines were placed at least 2 km away, the increase in carbon deposition would only be about 10%. The number of turbines plays a marginal role in altering the biodeposition flux. [less ▲]

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See detailFatigue Assessment of Hydraulic Steel Structures
Dang Van Thuong, ULiege

Doctoral thesis (2021)

This research consists of assessing and updating the remaining fatigue life of hydraulic steel structures when a fatigue crack has been discovered or is postulated. Due to constraints linked to inspection ... [more ▼]

This research consists of assessing and updating the remaining fatigue life of hydraulic steel structures when a fatigue crack has been discovered or is postulated. Due to constraints linked to inspection practices, cracks are generally rather large when detected. The research aim is to provide an optimum planning of repairs, in the best conditions for different input data. The study targets optimization of inspection schedule based on probability of failure, repair policies and cost of repairs. Risk-based inspection and maintenance of a hydraulic steel structure are performed based on a critical component or multiple critical components. The study provides an innovative approach for calculating the reliability of hydraulic steel structures, giving strategies and solutions to mitigate risk under corrosion and fatigue fracture failure. The influence of general corrosion and pitting corrosion for assessing and updating the remaining fatigue life of hydraulic steel structures are included in this research. [less ▲]

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See detailA numerical model based on cellular automata to assess travelling fires
Gamba, Antonio ULiege

Doctoral thesis (2021)

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See detailOn the k-binomial equivalence of finite words and k-binomial complexity of infinite words
Lejeune, Marie ULiege

Doctoral thesis (2021)

Complexity functions are well-studied objects in combinatorics on words. They encode some information about an infinite word: they count, for every non-negative integer n, the number of factors of length ... [more ▼]

Complexity functions are well-studied objects in combinatorics on words. They encode some information about an infinite word: they count, for every non-negative integer n, the number of factors of length n present in the infinite word. One may take variations of the classical factor complexity, by counting not all factors, but only those which are different enough one from the other. To this aim one can define an equivalence relation and count, for any n, the number of equivalence classes among all factors of length n of a given infinite word. In this thesis we are interested into the k-binomial equivalence and its associated complexity. This latter equivalence involves the notion of binomial coefficient of words, counting, given two words u and x, the number of times (u,x) that x appears in u as a subword. Two words u and v are k-binomially equivalent if (u,x)= (v,x) for every word x of length up to k. In this manuscript we first count the number of k-binomial equivalence classes and give an algorithm generating the 2-binomial class of a finite word. We also show that the monoid A^* / ~2 is isomorphic to the submonoid, generated by A , of the nil-2 group N_2 (A) . We then compute the exact values of the k-binomial complexity of the Thue–Morse word and the Tribonacci word, and we discuss the techniques employed, in an aim of generalizing it to larger families of words. Finally, we study a variant of the classical reconstruction problem and show that, proceeding in a sequential way, knowing n/2 + 1 well-chosen binomial coefficients is sufficient for reconstructing any binary word of length n. We also treat the case of an arbitrary alphabet and show that our bounds are better than what was known in the classical reconstruction case. [less ▲]

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See detailMethodology for the design of climate-responsive houses for improved thermal comfort in cold semi-arid climates
Mahar, Waqas Ahmed ULiege

Doctoral thesis (2021)

Pakistan is facing a severe energy crisis which results in power cuts across the country. This situation seriously disturbs everyday life, business, and economic activities. The household sector in ... [more ▼]

Pakistan is facing a severe energy crisis which results in power cuts across the country. This situation seriously disturbs everyday life, business, and economic activities. The household sector in Pakistan is the primary consumer of electricity. A reasonable sum of this electricity is used for heating and cooling residential buildings, which can be reduced by adopting passive design strategies. This PhD research aims to provide informed decision support to design and construct climate-responsive houses in the cold semi-arid climate of Quetta, considering the appropriate and locally adapted low-tech solutions to improve residential buildings' indoor thermal comfort. Firstly, a literature review was done to understand the existing housing, comfort, and energy situation in Pakistan. An inventory of the current housing stock was then created to identify housing characteristics, construction types, and materials. The most common housing type was analysed for indoor climate, including monitoring indoor temperature and humidity, comfort perception and energy usage behaviour. Semi-structured interviews were conducted with the residents to get insights on their comfort perception, clothing, behavioural adaptations, lifestyle etc. Then a benchmark study was performed by selecting the most representative house. The representative house's virtual model was analysed using dynamic simulation and calibrated based on actual monitored data. Four comfort models were compared to identify the best fit-t-context model. A parametric analysis was done using passive design strategies to improve indoor thermal comfort. A sensitivity analysis of 21 design variables was performed to identify the most influential passive design strategies, which can be used in the climate of Quetta. A materialization survey was done to determine the locally available and manufactured materials. Based on this PhD research analysis and findings, a prescriptive guide was developed to provide informed decision support for architects to design comfortable and climate-responsive houses. The prescriptive guide was then tested and validated. A usability test was performed among the architects and architecture. The results show that the prescriptive guide provides enhanced decision support compared to the Building Code of Pakistan. In the end, recommendations are made for the regulators and further research. [less ▲]

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See detailPositional Numeration Systems: Ultimate Periodicity, Complexity and Automatic Sequences
Massuir, Adeline ULiege

Doctoral thesis (2021)

This dissertation thesis is made up of three distinct parts, connected especially by complexity notion, factorial complexity as well as state complexity. We study positional numeration systems and ... [more ▼]

This dissertation thesis is made up of three distinct parts, connected especially by complexity notion, factorial complexity as well as state complexity. We study positional numeration systems and recognizable sets through decision problems and automatic sequences. The first part is devoted to the following problem: given a numeration system U and a finite automaton accepting U-representations of a set X ⊆ N, can we decide whether the set X is ultimately periodic (i.e. a finite union of arithmetic progressions)? We prove that this problem is decidable for a large class of numeration systems based on linear recurrent sequences. Thanks to the given automaton, we bound the possible periods of X via an arithmetical study of the linear recurrent sequence, as well as p-adic methods. The second part is dealing with the set of non-negative integers whose base-2 representation contains an even number of 1, called the Thue-Morse set and denoted by T. We study of the minimal automaton of the base-2^p expansions of sets of the form mT+r, where m and p are positive integers and r a remainder between 0 and m−1. In particular, we give the state complexity of such sets. The proposed method is constructive and general for any b-recognizable set of integers. As an application, we get a procedure to decide whether a 2^p-recognizable set given via an automaton is a set of the form mT+r. Finally, in the third part, we study properties of automatic sequences based on Parry and Bertrand numeration systems. We show that Parry-automatic sequences, like Pisot-automatic sequences (and thus in particular like b-automatic sequences) have a sublinear factor complexity. Furthermore, we exhibit a Bertrand-automatic sequence whose factor complexity is quadratic. We also prove that, contrarily to Pisot-automatic sequences, the image of a Parry-automatic sequence under a uniform morphism is not always a Parry-automatic sequence. The same happens for periodic deletion of letters. Last, we give the generalization to multidimensional sequences of a well-known result: a sequence is U-automatic if and only if its U-kernel is finite, U being such that the numeration language is regular. [less ▲]

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See detailBiological Roles & Evolution of Triterpenoids in Holothuroids
Claereboudt, Emily ULiege

Doctoral thesis (2021)

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See detailEtude phytochimique et biologique de deux plantes médicinales de Côte d’Ivoire : Lantana camara et Lantana rhodesiensis (Verbenaceae)
Nea, Fatimata ULiege

Doctoral thesis (2021)

Cette thèse a pour but de contribuer à l’étude phytochimique de Lantana camara Lin et Lantana rhodesiensis Moldenke, et de justifier leurs utilisations dans la médecine traditionnelle ivoirienne. La ... [more ▼]

Cette thèse a pour but de contribuer à l’étude phytochimique de Lantana camara Lin et Lantana rhodesiensis Moldenke, et de justifier leurs utilisations dans la médecine traditionnelle ivoirienne. La première partie a consisté à la détermination de la composition chimique et à l’évaluation des activités biologiques de l’huile essentielle des organes de ces plantes. Les échantillons d’huile essentielle ont été obtenus par hydrodistillation et analysés par CPG-SM, CPG-FID-IR et RMN 13C. Les résultats ont montré que la composition chimique de l’huile essentielle des organes est majoritairement dominée par l’(E)-β-caryophyllène et l’α-humulène. Les monoterpènes tels que le thymol, le sabinène et le 1,8-cinéole y sont parfois majoritaires. L'analyse statistique des échantillons d’huile essentielle a révélé une variabilité de la composition chimique des organes. En outre, l'impact de la variabilité due au stade phénologique sur la composition de l’huile essentielle des organes de L. camara a été démontré. Il ressort que la proportion de thymol est plus élevée pendant les mois de floraison et de fructification intense. La variation chimique de l’huile essentielle de L. camara serait également liée aux facteurs biogéographiques et génétiques. L’huile essentielle des feuilles et des fleurs présente des activités insecticide, antioxydante et anti-inflammatoire intéressantes. La deuxième partie a consisté à l’exploration phytochimique bio-guidée des organes de L. rhodesiensis. Le screening phytochimique a permis de mettre en lumière une plus grande richesse des feuilles en polyphénols et flavonoïdes. L’extrait des feuilles présente une activité antioxydante et antiplasmodiale plus élevée par rapport à l’extrait des tiges et des racines. Plusieurs fractions de l’extrait des feuilles ont révélé une activité antiplasmodiale intéressante (15 ˃ CI50 ˂ 3 µg/mL). À partir des feuilles, une nouvelle flavone (1) et trois autres flavones ont été isolés, il s’agit de : rhodescine ou 5,6,3’,5’-tétrahydroxy-7,4’-diméthoxyflavone (1); 5-hydroxy-6,7,3’,4’,5’-penta-méthoxyflavone (2); 5-hydroxy-6,7,3’,4’-tétramethoxy-flavone (3) et 5,6,3'-trihydroxy-7,4'-diméthoxyflavone (4). La structure de chacun de ces composés a été élucidée par les méthodes spectrales de RMN 1H, 13C, COSY, HSQC, HMBC et LC-MS. Les composés 1, 3 et 4 ont été identifiés pour la première fois à partir de cette espèce. Le pourcentage d’inhibition (%I) du radical DPPH de chaque composé (1mg/mL) a été déterminé. La rhodescine (1) (%I = 97,92 ± 0,20) présente un pourcentage d’inhibition proche de celui de l’acide ascorbique (%I = 98,50 ± 0,56) et de la quercétine (%I = 98,89 ± 0,74). Le pourcentage d’inhibition du composé 4 est moyen (%I = 61,77 ± 3,53) tandis que celui des composés 2 et 3 est faible. Les résultats de ces travaux de recherche permettent de justifier l’usage de ces deux plantes dans la médecine traditionnelle, notamment dans le traitement du rhumatisme et de la malaria. Ces travaux ouvrent des perspectives sur d’autres investigations scientifiques qui pourraient aboutir à l’identification de nouveaux métabolites secondaires à potentialité antioxydante et antipaludique. [less ▲]

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See detailLe financement basé sur les résultats au Bénin et au Sénégal : Un levier pérenne de changement de pratiques des agents de santé ?
Bodson, Oriane ULiege

Doctoral thesis (2021)

Performance-based financing (PBF) has been widely implemented in low- and middle-income countries with the aim of incentivizing health service providers and the health workforce to improve the quantity ... [more ▼]

Performance-based financing (PBF) has been widely implemented in low- and middle-income countries with the aim of incentivizing health service providers and the health workforce to improve the quantity and quality of care for nearly twenty years now. However, the PBF approach continues to face a lack of (relevant) evidence regarding its effects, and a limited understanding of the motivational factors that explain the presence or absence of its effects. This doctoral research intends to address this gap. It aims to explore the potential for change in health workers’ practices through PBF in Benin and Senegal, and uncover the multiple explanatory factors underlying these changes. The originality of our research is manifold. It combines two study countries, analyzes several PBF programs and does so, with an original emphasis on the question of the sustainability of PBF effects in Benin. The research is based on the articulation of qualitative (documentary research, participant observation, semi-structured interviews) and quantitative (statistical analyzes) research methods, and mobilizes an original and dynamic analytical framework - the I-Change model. Our field study shows that, according to the health workers interviewed, PBF allows to change some of their practices, even if the observed changes are not systematic. In the case of Senegal, these changes are not accompanied by a systematic improvement of health indicators, even when the PBF is combined with demand-side programs through a conditional cash transfer (CCT) scheme. From our study, it also emerges that the potential of PBF to change health workers’ practices cannot be only explained by the financial incentive, which is central in results-based approaches dissemination strategy. Indeed, many levers for changing health workers’ practices - both tangible and intangible - have been identified, while other potential levers of change have not been activated, at least not always fully. The second field study conducted in Benin, 9 and 12 months after the end of PBF programs respectively, showed a general trend towards a gradual “relaxation” of “seriousness”, of professional “rigor”, and a deactivation of certain levers for change of PBF. The PBF programs in Benin did not have lasting effects. In addition, our field studies have shown that the context in which PBF programs are implemented plays a crucial role - which can be facilitating or hindering - in achieving and sustaining the results of PBF programs. Taken together, these observations challenge the idea that PBF can constitute an effective approach to respond to dysfunctional health systems – or at least they call for the implementation of PBF programs coordinated with the various reforms initiated or to be initiated within the national health systems (particularly relating to human resources for health remuneration and technical equipment funding), and forming part of an in-depth reflection on supply and demand of care challenges. [less ▲]

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See detailEffect of the Boundary Conditions Applied to the Liquid Bridge on the Liquid Transfer between Two Solid Surfaces
Tourtit, Youness ULiege

Doctoral thesis (2021)

The trend towards miniaturization requires to handle even smaller micro-components: they must be picked, placed with high accuracy, and then released. This highly challenging process should take into ... [more ▼]

The trend towards miniaturization requires to handle even smaller micro-components: they must be picked, placed with high accuracy, and then released. This highly challenging process should take into account two aspects: the yield of successful placements and the minimized risk of damaging the manipulated micrometer-sized objects due to contact forces. Despite the advantages of the latest gripping technologies, including low complexity, high accuracy, and high reliability, the component is subjected to high contact forces that could damage it. As a consequence, there is a need of developing new and innovative ways to manipulate micro-sized components with respect to the requirements mentioned above. Gripping based on capillary bridges is a promising technique to handle components at the micrometric scale. This technique offers many advantages: flexibility and reliability, self-centering effect, the capability of grasping small and delicate components in a wide range of shapes and materials thanks to the “bumper” effect of the mediated liquid bridge. Nevertheless, the liquid residue on the component after breaking up the bridge is undesirable. As a consequence, there is a need to design a capillary gripping system that can retain all the liquid after the breakup of the bridge. Understanding the formation, the stretching, and the liquid distribution after the breakup of the liquid bridge is mandatory. In this thesis and in the first place, we studied the rupture of a liquid bridge confined between different geometries of the gripper and the substrate: plane/plane, cone/plane, and cavity/plane. We developed, based on the resolution of the Young-Laplace equation, an operational quasi-static criterion to predict the rupture gap of the bridge. We also investigated the effect of the geometry on the liquid distribution after the breakup. Optimal geometries are found to retain up to 90% of the liquid after the breakup of the bridge. In the second place, we investigated the secretion dispensing in green dock beetles Gastrophysa viridula. Their ability to walk upside-down on any kind of surfaces rely on mediated secretion between their hairy pad and the surface they walk on. We studied the mechanism of the secretion dispensing from the source where it is produced to the contact zone. Experimental setups have been designed, with advancing 3D printing and micro-fabrication techniques. Models have been developed, discussed, and compared to experimental data. [less ▲]

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See detailAutumn to spring inorganic carbon processes in pack and landfast sea ice in the Ross Sea, Antarctica
Van der Linden, Fanny ULiege

Doctoral thesis (2021)

The Ross Sea, the southernmost sea on Earth, presents several iconic features of polar seas: sites of deep water formation, high summer primary production, floating ice shelves, the annual cycle of ... [more ▼]

The Ross Sea, the southernmost sea on Earth, presents several iconic features of polar seas: sites of deep water formation, high summer primary production, floating ice shelves, the annual cycle of advance and retreat of sea ice, polynyas and katabatic winds. Furthermore, sea ice in McMurdo sound (western Ross Sea) is one of the most productive marine environments. However, sea ice inorganic carbon dynamics and related air-ice CO2 fluxes have never been documented in the Ross Sea. Two surveys were carried out in the western Ross Sea to bridge over a critical gap in the current understanding of sea ice: autumn and winter processes. The land-based YROSIAE project was a temporal survey from late winter to summer within landfast sea ice. The ship-based PIPERS project was an unique opportunity to study the early stages of sea ice formation (in polynyas) and more common consolidated pack ice in autumn. Based on these two consistent surveys, this work aims to (i) examine the bulk ice pCO2 dynamics in landfast sea ice from late winter to summer (ii) investigate the seasonal pattern (net source vs net sink) and diurnal pattern of air-ice CO2 fluxes (iii) analyse the depth-dependent physical and biogeochemical processes involved in inorganic carbon dynamics (iv) assess the precipitation of calcium carbonate in autumn and during a full bloom season. CO2 fluxes were measured using the chamber technique in autumn, late winter and spring, over open surface water, frazil ice patch, grey unconsolidated ice and consolidated first-year ice. These new autumn and winter data provide a first step to set up the budget of air-ice CO2 fluxes over the year and evaluate the large-scale influence of these fluxes on the annual uptake of CO2 by ice-covered oceans. Our results confirm that sea ice acts as a CO2 source for the atmosphere during ice growth, with enhanced fluxes reported at the early stages of sea ice formation, and shifts to a sink in spring. In late spring, diel pattern superimposed upon this seasonal pattern and was potentially assigned to either ice skin freeze-thaw cycles or diel changes in net community production. The snowpack plays a complex role in CO2 exchanges and can no longer be considered as an inert reservoir lying at the sea ice surface. The main features of the normalized DIC distribution (DIC35) through the ice column were: (i) a marked depletion at the surface from autumn to spring induced by the CO2 releases to the atmosphere (ii) bubble-driven gas enrichment below or within impermeable layers and (iii) an initial DIC35 enrichment in the bottom layer disappearing in spring when the seasonal peak in biomass occurs.At the bottom of landfast ice, in spring, a particular assemblage of microorganisms, the biofilm, led to a massive biomass build-up counterintuitively associated with nutrients accumulation. This biofilm formation may also promote calcium carbonate precipitation. However, in young pack ice or in cold landfast ice in early spring, limited calcium carbonate precipitation was reported. This suggests that calcium carbonate precipitation is not an ubiquitous process, especially in winter and autumn Antarctic sea ice. Comparison of calcium carbonate precipitation and pCO2 measurements advocates that the calcium carbonate precipitation is rather controlled by pCO2 than temperature. [less ▲]

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See detailPrecision of auditory-verbal working memory performance: A behavioral and neuroimaging investigation
Bouffier, Marion ULiege

Doctoral thesis (2021)

This thesis investigated the precision of auditory-verbal working memory (WM) at phonetic, phonological and semantic levels using probe recognition tasks; in these tasks, participants were presented with ... [more ▼]

This thesis investigated the precision of auditory-verbal working memory (WM) at phonetic, phonological and semantic levels using probe recognition tasks; in these tasks, participants were presented with auditory lists of words or nonwords. After each list, a probe item was presented, and participants were invited to determine whether that item had been in the list. We manipulated the levels of phonetic, phonological or semantic proximity between target and probe items to assess the precision with which items were stored in WM. We showed that phonological WM precision is limited when single-phoneme level resolution is needed, with rejection accuracy strongly declining when target and probe items differ by only one phoneme. We also showed that phonological WM precision declines when multilingual speakers are tested in their less proficient language, suggesting that precision further depends upon the precision of underlying language representations. The fragility of phonological WM traces has furthermore been highlighted in our functional magnetic resonance imaging (fMRI) study, which revealed robust discrimination of phonologically non-overlapping nonwords maintained in WM, but not of phonologically overlapping nonwords. At the phonetic level, we showed that precision for subtle phonetic information tended not to be reliably represented in WM, in line with evidence suggesting that fine-grained phonetic codes are not systematically contained in WM under more naturalistic listening conditions. At the semantic level, we observed high rejection accuracy for probes highly related to target items presented at initial list positions. This suggests that semantic variables influence precision in a time-dependent manner, with early list items being more strongly activated, allowing for optimal discrimination between the target item and a semantically highly related probe item. Hence, while advancing our understanding of the limits and nature of auditory-verbal WM precision, this thesis also highlights the close association of auditory-verbal WM and language domains. [less ▲]

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See detailEffect Of Magnetic Reconnection Over The Earth’s Space Environment
Matar, Jessy ULiege

Doctoral thesis (2021)

The majestic spectacle of polar aurora has fascinated the humankind since the dawn of time. It was understood, already several centuries ago, that the auroral and concurrent magnetic activities were ... [more ▼]

The majestic spectacle of polar aurora has fascinated the humankind since the dawn of time. It was understood, already several centuries ago, that the auroral and concurrent magnetic activities were related to solar activity, which was later understood as the source of the resulting solar wind, which carries a frozen-in magnetic field and interacts with the magnetic field of the Earth. Major progresses were realized towards the understanding of the coupled solar wind - magnetosphere - ionosphere system after the beginning of the space era. Since 1958, around thirty satellites were sent to orbit the Earth and to observe the resulting auroral and geomagnetic disturbances and the different processes governing the solar wind - magnetosphere coupling. Space based observations also led to the discovery of a population of electrically charged particles trapped in the geomagnetic field, forming the plasmasphere. Under suitable conditions, interaction between the solar wind and the Earth’s geomagnetic environment causes a reconfiguration of the magnetic field that connects the interplanetary magnetic field to the geomagnetic field producing so-called open magnetic field lines. The solar wind flow then drags these open field lines, giving the magnetotail its elongated shape. Previously opened field lines eventually reconnect in the central region of the magnetotail, releasing energy and reconfiguring the field back again to a closed configuration. This cycle of magnetic field line opening and closure is now understood to be at the heart of the dynamics of the Earth’s space environment and its auroral and magnetic activity, producing auroral substorms and global geomagnetic storms. We investigate several storm and substorm cases in order to understand how the various regions of the magnetosphere and upper atmosphere interact with each other under different solar wind conditions. This thesis consists of two distinct studies: the first study examines in situ measurements of magnetic reconnection and their relation with remote sensing auroral observations, whilst the second examines the plasmaspheric and auroral responses during storm time. The aim of the first part of the thesis is to study the coupling between the solar wind and the magnetosphere and identify how its consequences materialize in different regions of the system, from the aurora to the space environment of the Earth, with a particular attention being given to the effects of magnetic reconnection. A combination of data from different origins, including satellites, magnetometers and radars, was used to achieve this aim. We combine the NASA-IMAGE satellite observations of the proton aurora with ground based measurements of the ionospheric convection from SuperDARN to analyse the cycle of magnetic flux opening and closure in the Earth’s magnetosphere. The ESA-Cluster mission provided in situ measurements of the plasma properties at reconnection sites which were concurrent with auroral observations from IMAGE and SuperDARN, and therefore allowed us to investigate the ionospheric consequences of reconnection occurring in the magnetotail on the nightside and at the magnetopause on the dayside. We demonstrated that the reconnection rate, expressed as an electric voltage, determined from ionospheric observation, reliably reflects the physical process occurring in the distant space both on the dayside and on the nightside, a result of fundamental importance. The impact of intense solar wind coupling with the magnetosphere makes up the second part of my project, devoted to the contrasted storm time response of the plasmasphere density and boundary on one hand, and the ionospheric auroral dynamics on the other hand. The satellite observations of the aurora from IMAGE-FUV and of the plasmasphere from IMAGE-EUV were used in addition to SuperDARN, OMNI, GOES data, and ground-based magnetometer-derived activity indices. We reach several conclusions highlighting the interplay of the different elements of the system: the plasmasphere responds directly to changes in the solar wind properties, the ionospheric convection boundary HMB is magnetically related to the plasmapause reflecting the topology of the system, the plasmasphere density correlates with the open magnetic flux but does not with the dayside and nightside reconnection rates owing to the fact that reconnection varies over shorter time scales. The analysis showed that some parameters can correlate better during the most active phase of the storm and therefore, better describe the direct response of the magnetosphere than the recovery phase. [less ▲]

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See detailImpact des coopératives agricoles des cultures vivrières sur les conditions de vie des ménages ruraux au Burundi : Cas des coopératives de la province de Ngozi
Manirakiza, Dismas ULiege

Doctoral thesis (2021)

For more than two decades, Burundi has experienced a resurgence of interest in agricultural cooperatives following the appeal of humanitarian partners aiming to reorient their intervention. In the regard ... [more ▼]

For more than two decades, Burundi has experienced a resurgence of interest in agricultural cooperatives following the appeal of humanitarian partners aiming to reorient their intervention. In the regard, the Government has given a higher priority to the development of food crops to ensure the supply of the population from national productions. Considering its historical situation of recurring food insecurity, the province of Ngozi has since had a proliferation of agricultural cooperatives around food crops, as well as cash crops, mainly coffee. Most of them are involved in access to low-cost agricultural inputs, markets, agricultural micro-credits, natural resources, training and information. The objective of this study was to assess the impact of food crops cooperatives on the living conditions of rural households in Burundi, particularly in the province of Ngozi. The realization of this study covering a period from 2016 to 2019 combines three methods such as the documentary exploitation, surveys and interviews with different actors of the cooperative movement of Busiga and Gashikanwa communes in Ngozi province. The fist survey was conducted on 90 members randomly selected in cooperatives of three main organizations present in each commune. The second survey was carried out on a comparison group of 60 non-members, who were selected by using the purposive sampling technique in the same social group and geographical area as cooperatives’ members. This study highlights various services offered by cooperatives to their members and to the surrounding community. Depending on their size, cooperatives are a preferred channel for supplying agricultural inputs and learning new farming techniques. The valuation of production (storage, processing, sale and inventory credit) is part of their concern. Facing the challenge to get agricultural financing, the cooperatives are innovating alternatives for accessing small loans. Under of mutual solidarity, members organize a kind of community health insurance. For some, cooperative members benefit from regular training on hygiene, small entrepreneurship, environmental protection, peaceful cohabitation, etc. Regarding of the impact assessment, the analysis shows that cooperatives have effects on the majority of aspects of the living conditions of their members. At the production level, the statistical test shows a significant difference in the yields of bananas between the two groups (p = 0.075) at the significance level of 10%. The impact corresponds to an average yield increase of 640 kg / ha per member household. Considering that the banana is an important crop in consumption and especially in commercialization; the increase in its production brings relatively high income to households, especially in member’s. In the process, the storage also allowed the cooperative members to have a capital gain on the production and an inventory credit. Regarding of the livestock, the impact is estimated at an average increase of 0.40 cattle and 0.46 goats per household of members. This situation expresses a great opportunity for fertilization, a social esteem and a wealth with an average value of 160,000 BIF (cattle) and 46,000 BIF (goat) The comparative analysis reveals a significant difference between the average amounts of loans taken out by the two groups. The average difference of 28,500 BIF would therefore constitute an impact induced by membership in cooperatives. Regarding of the habitat, the difference is significant for the quality of materials of the walls, access to safe water and the quality of latrines. Indeed, the impact corresponds to a 13% decrease in the level of possession of houses whose walls are built with wood covered of mud, a 9% decrease in the level of unsafe water consumption and a 7% increase in the level of possession of fitted latrines among members. In this respect, members appear less exposed to precarious hygienic conditions than non-members. In addition, the mutual health insurance within the cooperative offers them financial and physical accessibility to health care. The difference is also significant in the number of houses owned by households. The impact obtained is 0.5 houses corresponding to an additional number of houses owned by a household of cooperators. In relation to the equipment of the house, the impact appears in the possession of the cupboard and the dining room. An additional house and the possession of "complementary" equipment would enhance the comfort of a household. For the other material means, the impact appears in the possession of the bicycle and the radio in the households of the members. The bicycle plays a major role in the speed and cost of activities carried out in the households and the radio allows them to be constantly informed. The analysis of early school leaving reveals an impact corresponding to an average decrease of 0.15 school dropouts in member households. Although the difference is small, the 15% drop in eating just one meal per day among the low-income group could also be an impact. Coming out of the crisis, the cooperatives have succeeded in gathering together people living on the same hills around a common ideal. The social harmony observed in farmers’ cooperatives studied is reflected in mutual aid in many situations. [less ▲]

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See detailDevelopment of multidimensional approaches for metabolomics
Di Giovanni, Nicolas ULiege

Doctoral thesis (2021)

Metabolomics in a clinical context faces many analytical challenges. GC×GC-TOFMS has much higher sensitivity and resolution, therefore much higher untargeted capabilities than GC-MS but is still largely ... [more ▼]

Metabolomics in a clinical context faces many analytical challenges. GC×GC-TOFMS has much higher sensitivity and resolution, therefore much higher untargeted capabilities than GC-MS but is still largely neglected in comparison. In front of that situation, the aim of the thesis was to develop methods to exploit the performances of GC×GC-(HR)TOF-MS in untargeted metabolomics in a clinical context, with the underlying goal of extending its use relatively to 1D GC-MS. [less ▲]

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See detailPiezoelectric Digital Vibration Absorbers for Multimodal Vibration Mitigation of Complex Mechanical Structures
Raze, Ghislain ULiege

Doctoral thesis (2021)

Engineering structures are becoming lighter and more complex to accommodate the ever-increasing demand for performance and to comply with stringent environmental regulations. This trend comes with several ... [more ▼]

Engineering structures are becoming lighter and more complex to accommodate the ever-increasing demand for performance and to comply with stringent environmental regulations. This trend comes with several challenges, one of which is the increased susceptibility to high-amplitude vibrations. These vibrations can be detrimental to structural performance and lifetime, and may sometimes even threaten safety. Passive and active vibration reduction techniques can provide a solution to this issue. Among the possibilities, piezoelectric damping is an attractive option, due to its compact and lightweight character, its reduced cost and its tunability. This technique uses the ability of a piezoelectric transducer to transform part of its mechanical energy into electrical energy. The converted energy can then be dissipated by connecting a shunt circuit to the transducer. However, the difficulty of realizing such circuits limits the broad applicability of piezoelectric shunting. This doctoral thesis investigates the potential of replacing the electrical circuit comprising classical components such as resistors and inductors by a digital unit and a current source, thereby creating a digital vibration absorber (DVA). Virtually any circuit can be emulated with a digital controller, providing this approach with an extreme versatility for vibration mitigation of complex mechanical structures. In this regard, the DVA is first analyzed in terms of power consumption and stability of the controlled system. Then, effective and easy-to-use tuning approaches for the control of multiple structural modes either with passive electrical circuits or a DVA are proposed, namely a passivity-based tuning of shunt circuits, a modal-based synthesis of electrical networks interconnecting multiple piezoelectric transducers, and a numerical norm-homotopy optimization resulting in an all-equal-peak design. These techniques are eventually applied and adapted to real-life structures with potentially complex dynamics. Specifically, effective vibration mitigation is demonstrated on structures exhibiting nonlinear behaviors and high modal density. [less ▲]

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See detailMulti-Degree-of-Freedom Hybrid Fire Testing in a Non-Linear Environment
Mergny, Elke ULiege

Doctoral thesis (2021)

Hybrid Fire Testing (HFT) is a performance-based approach for structures in fire based on substructuring method. A complete structure is divided in two substructures, one being in a fire test laboratory ... [more ▼]

Hybrid Fire Testing (HFT) is a performance-based approach for structures in fire based on substructuring method. A complete structure is divided in two substructures, one being in a fire test laboratory (physical substructure [PS]), and one being numerically simulated (numerical substructure [NS]). By reducing the number of elements to be tested, this method overcome the huge costs of large-scale tests. Some hybrid fire tests have been successfully performed in the last decades, showing that this technique is promising. However, as HFT is still in its infancy, these hybrid tests were limited to one-degree-of-freedom (DOF) tests. In parallel with the tests, the stability of the HFT process has been studied and algorithms have been developed. These algorithms have been validated numerically but few have been used in experimental tests. This research aims first to propose a new framework based on linear control system theory and proportional integral controller to address identified stability issues and control the time properties in HFT. The final objective consists in performing multi-DOF tests based on this methodology. [less ▲]

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See detailContribution des concessions agricoles périurbaines à l’approvisionnement alimentaire de la ville de Kinshasa
Masiala Bode, Mabu ULiege

Doctoral thesis (2021)

The challenges of the demographic evolution of Kinshasa town and its food needs have led this doctoral research to focus on the case of peri-urban agricultural concessions. Two specific objectives have ... [more ▼]

The challenges of the demographic evolution of Kinshasa town and its food needs have led this doctoral research to focus on the case of peri-urban agricultural concessions. Two specific objectives have been assigned to this doctoral thesis. The first was to analyze the land security of farm who use agricultural concessions. The second focused on the analysis of the production systems of these peri-urban agricultural concessions. These two objectives were operationalized separately and integrated together through the adaptation of the evolving theory of property rights over rural agricultural land in Kinshasa. The development of this thesis required the adoption of an inductive scientific approach based on the analysis of documentary resources, interviews with key ressources persons, surveys of agricultural concessions and observations, with agricultural concessions of the peri-urban commune of Mont-Ngafula in Kinshasa as area study. It emerges from the results of this thesis that: - The area of the municipality of Mont-Ngafula devoted to agricultural concessions between 1975 and 2015 is to nearly 5,491.65 ha, or 15.3% of the total area of this municipality; - The rural lands of Mont-Ngafula are managed by administrative authorities and customary chiefs. This cohabitation pushes the purchasers of agricultural concessions to formalize their land status in two phases. First by contacting the customary chief and with the Conservator of land titles. This double validation of the land status gives the security of land tenure use to the agricultural concessions ; - The users of agricultural concessions are mostly natural persons active in non-agricultural sectors. They are not agricultural professionals and do not reside in their agricultural concessions. They use few and unskilled labor force and the rudimentary production equipment. The rate of valuation of land agricultural concessions is low. This level decreases with the increase in the area of agricultural concessions; - The foodstuffs produced are of plant and animal origin. Crop yields are far lower than theoretically conceivable minima. The rearing of backyard animals, livestock and fish farming are of less importance. The holders of agricultural concessions prioritize arboriculture. This is to quickly obtain the empyteose contract and to keep it. This contract is the only officially recognized land title in the DRC; - Income from agricultural production is predominantly negative in all categories of agricultural concessions. When these incomes are positive, they represent absolutely nothing compared to the plus-value of land in Mont-Ngafula. Access to this plus-value is facilitate by the possibility of obtaining an authorization to change the destination of land acquired under agricultural concessions to residential land. It emerges from the investigations carried out that the security of the agricultural land concessions does not have incentives for agricultural investment. Indeed, the majority of agricultural concessions in the Municipality of Mont-Ngafula benefit from land security which, unfortunately, does not benefit the food supply of the city of Kinshasa, but rather serves to hoard land capital whose surplus value in the peri-urban areas of Kinshasa only increases because of the continuous horizontal extension of Kinshasa town. Faced with this paradox and to preserve the agricultural vocation of agricultural concessions on the outskirts of Kinshasa, the following recommendations are proposed: the subordination of the emphyteutic rental contract by the agricultural contract, the professionalization of agriculture in agricultural concessions (profile of the manager, production system and technical services), access to credits for financing agricultural activities and, the application of a property tax at differentiated rates according to the level of development of the agricultural concessions acquired. Finally, research on the contribution of peri-urban agriculture to the food supply of the city of Kinshasa, in particular the contribution of agricultural concessions, should continue and intensify. [less ▲]

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See detailEnhanced Efficacy and Economic Feasibility of Anaerobic Soil Disinfestation Combined with Carbon Source and Cover Tarps in Controlling Strawberry Soil-borne Diseases
Song, Zhaoxin ULiege

Doctoral thesis (2021)

Pre-planting soil fumigation is a common practice for controlling strawberries (Fragaria×ananassa Duchesne) soil-borne diseases worldwide. Methyl bromide was the preferred fumigant for growers until it ... [more ▼]

Pre-planting soil fumigation is a common practice for controlling strawberries (Fragaria×ananassa Duchesne) soil-borne diseases worldwide. Methyl bromide was the preferred fumigant for growers until it was classified as an ozone-depleting substance, and its utilization was gradually restricted and legally phased out in 2015 in China. Chloropicrin or 1, 3-dichloropropene as the main alternative fumigants for methyl bromide are not sustainable. These kinds of broad-spectrum fumigants require a commercially licensed application, are costly, and are potentially hazardous to agricultural workers and the environment. These negative side-effects have promoted the search for alternatives that growers can use to control soil-borne diseases. Anaerobic soil disinfestation (ASD) is widely evaluated to suppress soil-borne diseases economically in numerous crops. The efficacy of the ASD technique varies with the form of the carbon source and its quantity, the soil properties, the temperature, and the cover tarps. The influence of different tarps on ASD efficacy is not documented. The structure of the thesis was divided into three parts: 1) the first part focused on optimizing ASD technologies by testing several carbon sources, cover tarps, soil moisture, and air temperature to reduce ASD cost while maintaining the efficacy; 2) using high-throughput sequencing (HTS) technologies to monitor the soil microbial communities before and after ASD treatments; 3) organizing field trials to evaluate the effect of ASD on control strawberry soil-borne diseases and the responses of plant growth, yield, and grower’s income. In the laboratory experiments, we evaluated the efficacy of three films used for ASD. The films included: polyethylene (PE), totally impermeable film (TIF), and virtually impermeable film (VIF). Water irrigation was used as a blank control. The result indicated that the combined factors of maltose, 28℃ temperature, and 30% of soil moisture carried out for ASD were more efficient than the other conditions by orthogonal experimental studies. Also, ASD using maltose as an organic amendment and sealing with TIF obtained the higher suppression against Fusarium spp. (> 99.5%) and Phytophthora spp. (> 99.3%). In the field trials, the efficacy of ASD using 6 and 9 t/ha maltose and sealing with TIF was evaluated and compared with reference treatment with chloropicrin (Pic), soil solarization (Sol), or untreated control. Compared with the untreated soil, ASD treatments highly reduced the colony number of Fusarium spp. and Phytophthora spp., and successfully controlled the damage caused by root rot wilt disease. ASD significantly increased the soil’s nutrition which promoted plant growth. Also, it significantly increased strawberry yield, which was similar to the Pic but better than the solar energy treatment. The analyzed fungal and bacterial microbiota did not show significant differences in the taxonomic richness and diversity between the compared treatments. Nevertheless, compared with the blank control, ASD treatments seemed to cause a modification change of the soil bacterial and fungi taxonomy composition at the class and genus levels even though the shift was not significant. In the second field trial, to reduce the cost of ASD and to promote its commercial application, the impact of 6 tons/ha composted chicken manure (CCM, CCM6) or 12 tons/ha CCM (CCM12) and TIF against soil-borne pests was evaluated. The results showed that the colonies of Fusarium spp. and Phytophthora spp. reduced significantly after ASD. With ASD treatment, the concentration of ammonium nitrogen, nitrate-nitrogen, and organic matter was significantly increased, but the oxidation-reduction potential was decreased in the soil. Besides, the strawberry plant height, stem thickness, and yield were significantly higher than the control. The strawberry marketable income was higher with ASD, the economic benefit could be due to the suppression of soil-borne disease reduction and the improvement of soil nutrition. The soil bacterial and fungal diversity and richness increased after CCM 6 treatment, but there was no significant difference between the CCM12 and the control. The increased biological control agents lead to the suppression of soil-borne pathogens. In summary, the results of the three experiments showed that adding maltose or compost chicken manure as a carbon source and coupling it with TIF for ASD has a great potential to replace chloropicrin for soil-borne diseases control in commercial strawberries production. [less ▲]

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See detailUnraveling Neurod1 mechanism of action in the differentiation of the intestinal secretory lineages in zebrafish
Reuter, Anne-Sophie ULiege

Doctoral thesis (2021)

The bHLH transcription factors belonging to the ARP/Ascl superfamily are key regulators of cell differentiation in a wide range of tissues. We noticed a striking diversity among these ARP/Ascl factors ... [more ▼]

The bHLH transcription factors belonging to the ARP/Ascl superfamily are key regulators of cell differentiation in a wide range of tissues. We noticed a striking diversity among these ARP/Ascl factors when involved in the determination and differentiation of the endocrine cells. In this study, we first assessed whether different members of the ARP/Ascl family could rescue the gut phenotype of the ascl1a-/- zebrafish mutant, that presents a loss of all intestinal secretory cells. We showed that Neurod1 is the only factor of the family able to rescue the enteroendocrine cells while the others only rescue goblet cells in ascl1a-/- mutant intestine, and highlighted that this role is modulated by an Evolutionary Conserved Domain (ECD) in the protein. Additionally, RNA-sequencing analysis suggest that ECD domain acts as a repressor of the goblet lineage. Furthermore, we investigated the role of ECD domain within the endogenous gene by creating a zebrafish mutant line by CRISPR/Cas9 and performed loss of function studies. Finally, we introduced insights on interacting partners of Neurod1. Altogether, the results of our study provide new understanding in Neurod1 mechanism of action, especially through the highlight of a conserved domain present after the bHLH domain that seems important for target gene repression. [less ▲]

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See detailMonitoring the activity and composition of comets with TRAPPIST telescopes
Moulane, Youssef ULiege

Doctoral thesis (2021)

Comets are remnants of the early stages of the Solar System and the most primitive Solar System bodies. Understanding their nature and evolution history provides important clues about the formation of the ... [more ▼]

Comets are remnants of the early stages of the Solar System and the most primitive Solar System bodies. Understanding their nature and evolution history provides important clues about the formation of the Solar System and the planets. Comets contain complex organic molecules, and may have played a key role in delivering water, organics and noble gases from the interstellar medium to the early Earth, contributing to the origin of life. The strong scientific interest in the Solar System small bodies is well demonstrated by numerous space missions in the recent years, such as Stardust, Deep Impact, Dawn and New Horizon etc. Particularly, ESA’s very successful Rosetta mission recently visited comet 67P/Churyumov–Gerasimenko and made several ground-breaking discoveries that have dramatically increased our knowledge about comets. However, most of the space missions can only perform short-term studies over a narrow time window of single objects. We are currently lacking long-term observations to study variations in the activity and composition in the coma of a comet and how it evolves along its orbit around the Sun. We regularly use the two robotic TRAPPIST telescopes to observe relatively bright comets (V<12 mag) that are visible in both hemispheres. These telescopes are equipped with narrow-band cometary filters that allow us to collect images of a comet at wavelengths where the light is emitted by the main gaseous species accessible in the optical (OH, NH, CN, C2, and C3). In addition, we observe comets in three continuum windows (scattered sunlight) that allow us to characterize the dust component of the comet. Thanks to the large amount of telescope time available on both telescopes for this project, we collected a unique data set of thousands of photometric measurements of 35 comets including 18 Jupiter-family Comets (hereafter JFCs) and 16 Long Period Comets (hereafter LPCs) in addition to the first active interstellar comet 2I/Borisov which was discovered in 2019. Each comet is monitored along an important part of its inner solar system orbit, starting at 3 au from the Sun (where water start to sublimate) and all the way to its perihelion. Post perihelion, we followed the comet again all the way out to 3 au at least. Then, through cometary coma models, the abundances of the main chemical species (accessible in the optical part of the spectrum) and dust production proxy (known as Afrho) and its color were determined. These measurements, thanks to the high quality and homogeneity of the observations and of the verified analysis procedure, allowed us to address important and long debated questions like the existence of comet compositional classes (comet taxonomy), the changes of molecular abundance ratios with the distance to the Sun and the link between chemical composition and dynamical origins, which is a fundamental step in understanding the formation of comets and the Solar System itself. Among 29 comets for which the gas emissions were detected (at least CN and C2), we identified three depleted comets in carbon-chain elements. These comets are 21P/Giacobini–Zinner, 260P/McNaught and 398P/Boattini in addition to the first interstellar comet 2I/Borisov. 21P is known as a depleted comet for a long time , but we confirm its depletion in its 2018 passage. The other three comets were found to be depleted in C2 and C3 for the first time with TRAPPIST. We made an extensive monitoring of the activity of the first interstellar comet 2I/Borisov. We presented an initial characterization of its activity including magnitude, Afrho dust parameter and dust colours during our observation period. 2I/Borisov was found to be depleted in C2 with respect to CN similar to the Solar System comets carbon-depleted group. No LPC was found to be depleted in carbon-chain elements, except for comet C/2019 Y4 which was at the limit of depleted comets before its fragmentation where we see a significant change in its coma composition. We also found four comets (21P, C/2015 V2, C/2017 T2 and C/2018 W2) depleted in NH with respect to OH and CN. In term of dust activity, most comets show a normal dust/gas activity with respect to the heliocentric distance, except for comet C/2017 O1 which shows a higher dust/gas ratio (especially for Afrho/OH) and comet C/2018 Y1 that shows a lower dust/gas ratio (in both Afrho/OH and Afrho/CN) with respect to most comets. We made a follow-up of five JFCs that showed outbursts. These comets include 29P/Schwassmann-Wachmann 1, 123P/West-Hartley, 155P/Shoemaker, 243P/NEAT, and 260P/McNaught. Comet 29P, as usual, shows multiple outbursts with various amplitudes while other comets show an unique outburst. We discussed the evolution of the outbursts for each comet, by measuring the magnitude, Afrho parameter and dust colours. The dense monitoring of comets allows us to investigate new topics like the heterogeneity of the nuclei composition and the determination of their rotation period through the analysis of the flux variations and of the coma features (jets). We found that the rotation period of comet 41P was surprisingly changed by 26 hr in just two months while the rotation period of comet 46P did not change on both sides of perihelion with an average value of 9.10±0.05 hr. The regular measurements of the comets activity and composition from optical measurements are also invaluable to support observing programs on larger ground based or space telescopes that we plan with our collaborators or other groups to perform complementary studies of the most interesting objects through optical and IR spectrometers (e.g, 21P and 66P/du Toit). In this work, we also discussed the reactive collision of electrons with molecular cations in cometary coma. In order to improve our understanding of the kinetics of the cometary coma, theoretical studies of the major reactive collisions in these environments are needed. Deep in the collisional coma, inelastic collisions between thermal electrons and molecular ions result in dissociation and vibrational excitation of the ions, the rates of these processes are especially elevated due to the high ion and electron densities in the inner cometary coma. We presented the study of reactive collisions of electrons with CO+ and H2+ molecular cations using the multi channel quantum defect theory (MQDT), such as dissociative recombination (DR), vibrational excitation (VE) and vibrational de-excitation (VdE), to understand the importance of these reactive collisions in producing carbon, oxygen and hydrogen atoms in cometary activity. The results shows that among all reactive collisions taking place between low energy electrons and CO+/H2+, the dissociative recombination is the most important process at electronic temperatures characteristic of comets, which can be a major source of atoms in the cometary coma at small cometocentric distances. [less ▲]

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See detailLeaving Europe: Emigration, aspirations and pathways of incorporation of Maghrebi French and Belgians in Montréal
Mandin, Jérémy ULiege

Doctoral thesis (2021)

When it comes to migration, Western European countries such as Belgium and France are typically described as destination countries. Yet, emigration remains an important phenomena in most of European ... [more ▼]

When it comes to migration, Western European countries such as Belgium and France are typically described as destination countries. Yet, emigration remains an important phenomena in most of European societies. This emigration is often portrayed as somehow different from migrations ‘from the South.’ The western European migrant – sometimes referred to as ‘expat’ – is generally depicted as a dynamic individual characterized by an entrepreneurial spirit and a taste for adventure. At a time where many European societies experience both the consequences of financial and economic crisis and growing tensions about cultural and religious diversity, very few attention has been given to the relation between such structural dynamics and the emergence of emigration practices among young Europeans. This research is an attempt to explore such a relation by focusing on the migration practices of Belgians and French youngsters of Maghrebi origins leaving Europe for the Canadian city of Montréal. More precisely, the research focuses on the aspirations - defined as socially situated representations of the future – that inform the emigration practices of Maghrebi Europeans. Building on an ethnographic field research conducted in France, Belgium and in the city of Montréal, the thesis is an exploration of migration related aspirations and their evolution at three stages of the migration process: before departure, during migration and once arrived at destination. The goal of the research is to understand the factors that inform the development of emigration aspirations among Maghrebi European people, how these aspirations are channeled during migration and how they evolve after migration. Through the focus on migrants’ aspirations, the research questions how perspectives for a desirable future are distributed both in Europe and in Montréal and how this distribution is highly dependent of one social position. The collection of biographic interviews with Maghrebi European migrants allows to understand the various representations of the future that inform the emergence of migration desires. This highlights a set of various experiences – experiences of ‘existential stuckedness’ or of ‘existential mobility’ – that evolve during the migration process. The ethnographic data also allows to explore the various pathways of incorporation that are carved out by Maghrebi Europeans in Montreal in order to sustain possibilities for a desirable future. These pathways, sometimes constitutes alternatives to the types of incorporation promoted by the Canadian and Québec authorities. In this sense, looking at how migrants think about their future and how they try to organize it also highlights forms of agency that exceed societal expectations. [less ▲]

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See detailLe rôle du théier dans les petites exploitations familiales au Burundi : le cas des complexes théicoles de Teza et d’Ijenda
Bitama, Pierre ULiege

Doctoral thesis (2021)

Since its introduction in 1963, the tea plant has been the heart of a strategic sector in Burundi. Tea cultivation is of paramount importance in the socio-economic life of more than 60,000 tea farmers. It ... [more ▼]

Since its introduction in 1963, the tea plant has been the heart of a strategic sector in Burundi. Tea cultivation is of paramount importance in the socio-economic life of more than 60,000 tea farmers. It creates employment and provides foreign exchange export earnings for the country. The main objective of the research was to emphasize the importance of the tea plant in the means of subsistence of the tea farmers. The specific objectives are: (i) to identify all the resources of tea farmers that enable them to ensure their livelihood, (ii) to highlight the risks and constraints faced by tea farmers, (iii) to analyse the strategies developed by tea farmers to ensure their survival, (iv) to highlight the contribution of tea in the livelihood of tea farmers, (v) to identify and discuss the challenges and constraints in the country's tea sector. To achieve the specific objectives, the study used an analytical model - the livelihood model - to understand the farming system as a whole before a specific study on the tea plant through the analysis of the value chain of the sector on its technoeconomic and governance aspects. The study was carried out through the analysis of primary data and secondary data via a desk research. The primary data were collected in 2018 and 2019 from actors (managers) responsible for tea production, processing and marketing, as well as from a random sample of 120 tea farmers in the Teza and Ijenda areas. The results showed that tea farmers depend on complementary resources. They are facing a wide range of risks and constraints, particularly with regard to food and vegetable crops, a threat to tea farmers who mainly rely on agriculture even though adaptation strategies are being developed. On the other hand, the exploitation of the tea plant in the study area has demonstrated a particularity of the plant and the results highlighted the intrinsic characteristics and virtues of the tea plant. The regular income from the tea plant throughout the year enables tea farmers to purchase food on a regular basis, to overcome the lean season and to meet other needs. This regularity of income classifies smallholders in the zone into a poverty typology of financially secure farmers who are likely to fall into the " wealthy " category if their non-monetary means of survival improve. In addition, the plant's perennial nature and resilience to the country's climatic hazards mean that it is exploited from generation to generation. It provides a pension for tea farmers in old age and is the only guarantee of credit. Implementation of the recommendations developed (gradual replacement of nonproductive tea plants, continuous reforestation, product diversification, etc.) to address the challenges identified in the tea sector would increase yield, profitability and strengthen the resilience of tea farmers. [less ▲]

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See detailAbout some notions of regularity for functions
Loosveldt, Laurent ULiege

Doctoral thesis (2021)

Given a function, a first natural desire is to know its ``behaviour''. To achieve this goal, different notions, such as differentiability, Lipschitz or Hölderian conditions, have been introduced through ... [more ▼]

Given a function, a first natural desire is to know its ``behaviour''. To achieve this goal, different notions, such as differentiability, Lipschitz or Hölderian conditions, have been introduced through the time, with more and more preciseness. In this thesis, we aim at characterizing the regularity of functions from different points of view that generalize the precited ones, and using different associated functional spaces. First, we focus on uniform regularity, investigated through Besov spaces of generalized smoothness. These spaces were originally defined in terms of Littlewood-Paley decompositions and, quickly afterwards, a characterization using finite differences was given. Using this last one, we present some alternative definitions for Besov spaces of generalized smoothness, involving elementary objects: (weak) derivatives, polynomials and convolution. This is made in order to understand as precisely as possible what means the belonging to a given Besov space. Initially, these spaces are known to be interpolation spaces between Sobolev spaces. A first generalization was obtained by introducing a function parameter in the interpolation formula. The spaces we consider here are even more general and, as an intent to ``close the circle'', we define a new method of interpolation for which Besov spaces of generalized smoothness are still linked to Sobolev spaces. Then, we study pointwise regularity by defining functional spaces that generalize both the ones of Hölder and Calderón and Zygmund. After nearly characterizing them by the mean of wavelet coefficients, we establish a multifractal formalism particularly well adapted to explore the pointwise regularity through our new spaces. In fact, as their definition is a kind of localization around the point of interest of generalized Besov conditions, it is not a surprise that Besov spaces of generalized smoothness play a major role in this formalism. After investigating the multifractal nature of pointwise spaces of generalized smoothness, we focus, in a more functional analysis point of view, on their interaction with partial differential equations. This follows the trail of Calderón and Zygmund as we link generalized pointwise smoothness with some families of operators. This leads to a theorem that allows to give the regularity of the solution of an elliptic partial differential equation by formulating it from the regularity of the coefficients and the right-hand side of the equation. Finally, at a midpoint between uniform and pointwise regularites, we study functions that are continuously differentiable on a compact set. Even if the question seems naive and harmless at first look, all good habits from open sets are missing and a whole new theory needs to be established. Based on deep results of functional analysis, we characterize the completeness of the defined functional space and show that, for any compact set, the restrictions on it of the continuously differentiable functions on $\R^d$ are dense in our space. Finally, the latter is compared with other spaces, more frequently met in the literature. [less ▲]

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See detailEtude phytochimique et biologique de trois plantes du genre Zanthoxylum
Tanoh, Amenan Evelyne ULiege

Doctoral thesis (2021)

The genus Zanthoxylum (Rutaceae) includes plants known for their uses in traditional medicine around the world. In Côte d'Ivoire, nine species have been identified (Zanthoxylum atchoum, Z. leprieurii, Z ... [more ▼]

The genus Zanthoxylum (Rutaceae) includes plants known for their uses in traditional medicine around the world. In Côte d'Ivoire, nine species have been identified (Zanthoxylum atchoum, Z. leprieurii, Z. macrophilum, Z. mezoneurispinosum, Z. parvifoliolum, Z. psammophilum, Z. rusbescens, Z. gelletii and Z. zantoxyloides). Zanthoxylum geniuscontains several plant exhibitingbiological properties (antioxidant, anti-inflammatory, anticancer, antifungal, antitumor and antimicrobial etc.). The present research focuses on three species of Zanthoxylum harvested in Côte d'Ivoire: Z. leprieurii, Z. psammphilum and Z. mezoneurispinosum. Its goal is to valorize these plants through their volatile and non-volatile secondary metabolites. The first species Z. leprieurii is extensively used in traditional medicine because of its numerous biological properties. However, to date, no traditional use is known for the last two species endemic to Côte d'Ivoire. The lack of knowledge, especially on Z. psammophilum and Z. mezoneurispinosum, led to the realization of a phytochemical study for the determination and confirmation of biological activities of the constituents of various organs (leaves, trunk bark, roots and fruits) of these plants. The analyses of the chemical composition of essential oils and the biological properties of the various organs were realized. From a hydrodistillation with a Clevenger-type apparatus, the essential oils are extracted and analyzed by gas chromatography coupled with mass spectrometry (GC/MS). For the Z. leprieurii species, a study of the effect of the season on the chemical composition of the various organs of the essential oils was carried out. The statistical analysis of the results obtained made it possible to group the chemical compositions into three classes. The first class is characterized by constituents from fruits dominated by β-myrcene and citronellol. The second class was composed by compounds extracted from bark with an abundance of tridecan-2-one. The last class includes tridecan-2-one, (E) β-caryophyllene and dendrolasin which are derived from essential oils extracted from the leaves. In Z. psammophilum, the chemical compounds extracted from the essential oil of the bark are mainly characterized by methylketones and dominated by tridecan-2-one. However, essential oils from the leaves and roots are represented by methylketone and sesquiterpenes respectively. The main characteristics of essential oils isolated from Z. mezoneurispinosum are monoterpenes (α-pinene) in the aerial parts, while the underground part has an abundance of sesquiterpenes (γ-elemene and cyclosativene). The essential oils extracted from the three plants have satisfactory biological activities. These are antioxidant, anti-inflammatory, insecticidal and anti-plasmodial activities. In addition, the phytochemical study of the leaves of Z. mezoneurispinosum carried out by column chromatography, high pressure liquid chromatography (HPLC) and nuclear magnetic resonance (NMR) allowed the isolation of a total of eight compounds. They consist of four alkaloids (1-hydroxy-3,4-diméthoxy-N-méthylacridone, chelerythrin, skimmianine and xanthoxoline), one triterpene (lupeol), a cinnamic acid derivative (methyl 4-coumarate), a carboxylic acid derivative ((E)-4-isobutylamino-4-butenoic acid) and a flavonoid (4'-methoxy-5,7-dihydroxyflavone or acacetine). The different results indicate that these plants can be useful to human. Indeed, a better knowledge of the chemical composition of the different essential oils, their biological activities and their isolated compounds, can promote greater use in perfumery, food, cosmetics, medicine, etc [less ▲]

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See detailSmart Regulation for Distribution Networks – Modelling New Local Electricity Markets and Regulatory Frameworks for the Integration of Distributed Electricity Generation Resources
Manuel de Villena Millan, Miguel ULiege

Doctoral thesis (2021)

Growing awareness of the effects of man-made global warming is leading societies worldwide to re-evaluate our seemingly ever-increasing energy requirements. The need to understand and mitigate the issues ... [more ▼]

Growing awareness of the effects of man-made global warming is leading societies worldwide to re-evaluate our seemingly ever-increasing energy requirements. The need to understand and mitigate the issues brought about by our current use of the world's resources has thus become a pivotal element in the political agendas of most regions. Accordingly, curbing anthropogenic greenhouse gas emissions has been the goal of many of the political decisions of the past decade. In this context, the electricity sector is undergoing deep structural changes to accommodate intermittent renewable electricity generation resources into a system originally designed to rely on dispatchable power plants to supply our energy needs. One of the main changes consists of a decentralisation of the sector, bringing the generation assets closer to the place of final consumption. This creates regulatory challenges that may jeopardise the integration of distributed renewable energy resources (DER). This PhD dissertation presents several research contributions dealing with these challenges. In the first part of our work, we have created a simulation-based approach to study the effects of different regulatory frameworks on the deployment of DER installations. DER deployment, in turn, is shown to have a notable impact on the revenue of the distribution system operator (DSO), which is also assessed with our simulator. Our approach is designed so as to offer a tool for policy makers and regulators to discriminate between different regulatory frameworks depending on their impact on the distribution network, before implementing them in real life. The second part of our dissertation models different decentralised electricity markets where consumers may exchange electricity, focusing on the concept of renewable energy communities (REC). We have designed a model of interaction that simulates an REC where its members can offer flexibility services by means of a centralised agent such as the REC manager. In addition, we analyse the allocation of local electricity generation among the REC members, and propose an algorithm based on \emph{repartition keys} to minimise the total electricity costs of the REC. The modelling tools developed in this thesis highlight a trade-off between promoting the integration of DER and containing their impact on the DSO revenue. In addition, they show that creating RECs may help maximise the use of local production and, therefore, lower the electricity costs of these communities. Despite having been studied for a few decades now, the promotion of DER is still very much in the political agenda in many regions. Unstable policies concerning these technologies, along with an insufficient understanding of the challenges they pose to the traditional electricity system, have hindered their natural integration into the electricity networks. These problems, though deeply studied in this thesis, call for further research to fight man-made global warming. [less ▲]

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See detailStudy of chemical and enzymatic functionalization of lignocellulosic natural fibers
Morin, Sophie ULiege

Doctoral thesis (2021)

Within the commercially available materials, composites are a class of hybrid material constituted of at least two components. Used for structural and semi- structural applications, glass-fibers ... [more ▼]

Within the commercially available materials, composites are a class of hybrid material constituted of at least two components. Used for structural and semi- structural applications, glass-fibers composites are widely spread. Due to environmental concerns regarding the final glass-fibers reinforced composites, natural plant fibers have been identified as a potential ersatz. Natural fibers are selected on the base of their intrinsic mechanical resistance, similar nay enhanced than glass-fibers. Local fibers suitable for such application could be found all around the world. In Europe, natural fibers market is singularly different from the rest of the world. Instead of being ruled by cotton cultivation and trade, flax and hemp represent the main part of the fibers culture and market in Europe. Their physico-chemical properties turn them suitable for use as reinforcement agent in plastic matrix. To elaborate composite, many steps are required from fibers harvesting to the obtaining of a final functional material. Each step includes multiple parameters to control which affect the resulting composite mechanical properties. Different parameters of the composite elaboration were evaluated to determine which affect the most the final material mechanical properties. Constitutive biopolymers of the fibers were found to play a crucial role in the improvement of the polypropylene and thermoplastic starch reinforcement. In heterogeneous materials such as composites, an optimal load transfer is researched to fully exploit the properties of both initial components. Interface quality between fibers and matrix determine this load transfer. In order to improve the fibers-matrices compatibility, fibers treatments exist such as chemical modification or enzymatic functionalization. The effects of these treatments were evaluated at the fibers level and the resulting composite. This manuscript describes and studies the design of functional natural fibers as plastic reinforcement agent. [less ▲]

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See detailThe impact of fat formulation and emulsifiers on the macro- and microscopic physical properties of palm oil-based puff pastry margarines
Detry, Roxane ULiege

Doctoral thesis (2021)

This work presents advances in vegetable fat crystallization for puff pastry margarine applications

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See detailRegional variation in the Coffin Texts: A study of sentence structure, verbal structure and graphical forms
Grotenhuis, Jorke ULiege

Doctoral thesis (2021)

In the pursuit of regional variation in Ancient Egypt on a linguistic level, this thesis proposes to use the mortuary liturgy of the Coffin Texts as a base from which to extract signs of regionally ... [more ▼]

In the pursuit of regional variation in Ancient Egypt on a linguistic level, this thesis proposes to use the mortuary liturgy of the Coffin Texts as a base from which to extract signs of regionally conditioned variation in the language. In this thesis, three approaches were used in order to visualize the existence of regional variation in the Middle Egyptian language. In the first approach, the sentence structure was compared. Using the metaphor that spells could be treated as proteins, biomedical algorithms were used for cluster analysis of the structure. The second approach tackles the verbal structure of the sentences instead, applying the same method which was used for the sentence structure. Finally, the graphical form of the verbal lemmas was studied in order to show preferences for spelling and written structure. Additionally, the graphical form of morphological features of verbal constructions was studied. The approaches used in this thesis were able to visualize that regional conditioned patterns exist within the Coffin Texts. [less ▲]

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See detailPerennial crop systems in Dak Lak province, Vietnam: Practices and socio-economic analysis
Phan Thi Thuy, ULiege

Doctoral thesis (2021)

Perennial crops play a valuable role in agricultural economics, as they provide goods for export and jobs for the workforce as well as contribute significantly to economic prosperity at the national level ... [more ▼]

Perennial crops play a valuable role in agricultural economics, as they provide goods for export and jobs for the workforce as well as contribute significantly to economic prosperity at the national level. Vietnam has a high potential for perennial crop development, and thereby achieve an explosive growth in agricultural commodities. In terms of perennial crops, Vietnam now ranks among the top five international exporters of coffee, pepper and cashew. Vietnam is the second-largest producer of coffee worldwide, while it is the leading exporter of pepper globally. In 2018, the planted area of the dominant perennial crops (coffee, pepper, rubber, tea and cashew nut) reached around 2.2 million hectares (ha) nationwide, an increase of 9,000 ha compared to 2017. The Western Highlands has the largest region of perennial crop production with an area of 1.151 million ha. Dak Lak province has favorable conditions of soil (1,450 ha of basaltic soils of volcanic origin, which equals two thirds of the total basaltic soil area nationwide), as well as weather and amount of arable land, which creates an advantageous situation for the culture of perennial crops. Remarkably, the planted area of coffee and pepper dominated production at about 30% of the whole country’s production in 2018, respectively. Over the years, perennial crops have changed considerably being usual dynamics of requirements. Despite its advantages and positive development trends, provincial perennial crop production has faced numerous constraints due to price fluctuation, unpredictable climatic trends, and incidence of pests and diseases. Thus, perennial crop production needs further research to ensure more evidence. Based on a systematic survey, focus group discussion, key informant interviews and participatory observation, this research project was undertaken to evaluate the practices and socio-economics of perennial crop systems in Dak Lak province, namely monocultures and intercropping systems. The aims of this project are to understand the distinct stages of perennial crop systems and to identify the socio-economic benefits of different systems concentrating on coffee and pepper crops. Additionally, the remaining aim of the study finds determinants affecting the farm’s decision of adoption. The results provide critical references for farmers and policymakers on implementation or decision to plant a particular perennial crop and strategies. The findings show that the type of crop that was planted by the farmers evolved considerably in terms of crop types, crops grown, farm size, type of system and an increase of total cultivated surface. In addition, under driving forces including socio-economic transformation, political changes and ecological movement, perennial crop systems are well changed. Indeed, for many years, perennial crop systems have experienced an evolution through five stages, namely large-scale coffee and rubber plantations; perennial crop systems which are state-owned farms and cooperatives; intensified perennial crop systems; mixed crop systems, and the specialized and diversified perennial crop systems. At present, perennial crop systems are put into practice which take into account climate change, marketing and losses of fertile lands. These systems include monocultures and intercropping, which are two representative models of perennial crop systems which are investigated in this study. Simultaneously, a comparative assessment of the socio-economic benefits between two monocultures (coffee and pepper mono cropping) and an intercropping system (coffee and pepper intercropping) is presented in which the intercropping is more efficient than the monoculture under the context of constraints on key resources, risk and uncertainty. Respectively, intercropping is not only demonstrated to have high economic returns and limitations of economic risk due to the volatile market but also to have the benefits of extended seasonal employment and attraction for women as farmworkers on small farms. In other words, coffee and pepper intercropping is the most desirable option to obtain socio-economic benefits in perennial crop systems. In addition, the classifications in different approaches and groups producing are also organized to clarify these economic performances by cost-benefit analysis. The further results are obtained that intercropped farm approaches, especially in intercropped coffee farms (ICFs) generate more economic earnings than intercropped pepper farms (IPFs) while group producing coffee (GpC) appears to be more appropriate for smallholders than group producing pepper (GpP) does. At the same time, conclusions from binary and multiple logistic regression analysis highlight factors affecting decision-making of farms’ decision in adopting. These factors include household characteristics, farm profits and crop profiles. This study supplies information that will allow farmers to develop productive planning with respect to choosing suitable perennial crop systems, and assist policymakers in forming small-scale perennial crop production strategies in Dak Lak province. In addition, the factors highlighted here are taken into account in the development of perennial crops. [less ▲]

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See detailIntegrated Structural-Geophysical-Geomechanical Models of Landslides in Seismic Regions
Mreyen, Anne-Sophie ULiege

Doctoral thesis (2021)

Slopes in hilly or mountainous regions can present complex morphologies due to erosional, gravitational and seismotectonic processes. In seismically active regions, mountain ranges are usually ... [more ▼]

Slopes in hilly or mountainous regions can present complex morphologies due to erosional, gravitational and seismotectonic processes. In seismically active regions, mountain ranges are usually characterised by numerous slope failures in the form of shallow to deep-seated landslides; yet, their origin is often not clearly established and must not necessarily be seismic. This thesis investigates deep-seated landslides of unknown origin (and age) that hint at a probable co-seismic development in regard to their regional seismotectonic context, site-related structural and geological setting, and distinct geomorphological shape. Such investigations include the reconnaissance of surface as well as subsurface structures with a variety of methods; here, we analyse landslide surfaces with satellite imagery, through geomorphological observations and structural measurements, while multiple geophysical techniques are used to reveal subsurface structures and to infer geotechnical properties of the ground. The work is focused on two study areas presenting rather ancient slope failures: the seismogenic Hockai Fault Zone in East-Belgium, with the Bévercé and the Pays de Herve landslides, and the seismic Vrancea-Buzau region in the Carpathian Mountains of Romania, with the Eagle's Lake and Balta landslides. A third study area, the Longmenshan Fault Zone in Central China with the Daguangbao and the Qinglincun landslides, is used as reference site to discuss landslides actually triggered by a recent earthquake, i.e. the 2008 Wenchuan event, and highlights mechanisms leading to co-seismic slope failure. A decisive approach of this work is the integration of the collected data into 3D geomodels of the respective sites; these allow to link the geophysical subsurface information to observed surface structures, as well as to assess landslide dimensions and to estimate the volume of landslide debris still in place. For two study areas, the Bévercé and Balta landslides, we present a numerical back-analysis with distinct element modelling in the 2D and 3D domain, respectively, to further comprehend mechanisms influencing the genesis and development of slope collapses possibly induced by earthquakes. These computations are based on geomodelled pre-failure slope shapes, structural settings derived from field measurements and geotechnical properties inferred from geophysical measurements. For both sites, numerical computations indicate the necessity of ground acceleration to achieve similar failure patterns as observed in their actual post-failure state. At last, we introduce conclusive key elements that link the observed markers deduced from the field measurements and numerical analyses to distinctive processes that are crucial components to comprehend the development of slope failures in seismic regions. The larger interest beyond the direct scope of this study is the deeper comprehension of regional seismotectonic processes that were active in the past to allow for better constrained seismic hazard evaluations in the future. [less ▲]

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See detailÉtude de l’influence de l’état de stress posttraumatique sur la vulnérabilité aux drogues chez la souris DBA/2J
Matonda Ma Nzuzi, ULiege

Doctoral thesis (2021)

Posttraumatic stress disorder (PTSD) and drug addiction are two comorbid conditions bound in a complex bidirectional relationship. On one hand, the mechanisms by which PTSD promotes the occurrence of drug ... [more ▼]

Posttraumatic stress disorder (PTSD) and drug addiction are two comorbid conditions bound in a complex bidirectional relationship. On one hand, the mechanisms by which PTSD promotes the occurrence of drug addiction are not fully understood. On the other hand, methodological and ethical limitations inherent to human studies do not allow a full understanding of the influence of drug addiction on the expression of PTSD symptoms. In an effort to contribute to the resolution of these two issues, the present thesis based on an animal model with DBA/2J mice, combined sequentially, in both directions, a drug-induced locomotor sensitization procedure and an animal model of PTSD based on an electric shock. Locomotor sensitization was achieved by repeated administrations of ethanol or cocaine at the same dose over several days. The PTSD-like symptoms were assessed several weeks after the electric shock with conditioned fear, sensitized fear and anxiety tests. Overall, the various experiments have shown, on one hand, that a PTSD-like experience in mice does not significantly increase the intensity of drug-induced locomotor sensitization. However, this PTSD-like experience indirectly strengthen drug sensitization through an interaction with some of its modulating factors. On the other hand, drug-induced locomotor sensitization does not directly affect the expression of PTSD in this animal model. However, drug sensitization can be considered as a form of stress sensitization. It induces on its own stress behaviors that add to the effects of the PTSD experience. Further studies on the subject would provide a better understanding of the co-morbidity between PTSD and drug addiction. [less ▲]

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See detailStructural, physicochemical and functional properties of cumin (Cuminum cyminum) proteins
Chen, Jingwang ULiege

Doctoral thesis (2021)

Nowadays, there is an increasing number of plant candidates for protein extraction as an alternative for animal sources. The investigation of new plant protein sources and the study of the effects of ... [more ▼]

Nowadays, there is an increasing number of plant candidates for protein extraction as an alternative for animal sources. The investigation of new plant protein sources and the study of the effects of processing methods on their structure, physicochemical, and functional properties obtain more attention and become necessary. Cumin (Cuminum cyminum) is a traditional and worldwide culinary spice. After the extraction of essential oils and oleoresin, a relatively important amount of defatted cumin residues is produced, which are rich in protein (28.33%) and constitute a good substrate for protein extraction. In this thesis, the composition of protein fractions from cumin seeds and their principal characteristics were studied, as well as the effects of different environmental conditions (pH and NaCl) and processing treatments (heat and high hydrostatic pressure treatment) on the structural, physicochemical and functional properties of cumin protein isolate (CPI) were assessed. First of all, the protein fractions and CPI were extracted from defatted cumin residues, and their characteristics were investigated. The protein fractions of cumin seeds were albumin (62.29%), glutelin (25.16%) globulin (11.12%), and prolamin (1.43%). The CPI presented most bands of albumin, globulin and glutelin, and had more disulfide bonds than major protein fractions when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The glutamic acid and aspartic acid were the predominant amino acids in cumin proteins, furthermore, more hydrophobic and aromatic amino acids were found in CPI than in protein fractions, and the content of essential amino acids in CPI and globulin were higher than in albumin and glutelin. The glutelin displayed greater exposure of tyrosine and tryptophan residues and bigger particle size compared to albumin and CPI, while CPI presented more α-helix (14.4%) and less β-strand (30.7%) than albumin and glutelin. These differences in structure and amino acid composition for CPI, albumin, and glutelin significantly influenced their hydrophobicity (Ho) and zeta-potential (ζ) (p<0.05), and as a consequence their emulsifying and gelling property. Albumin exhibited the highest emulsifying activity (EAI) and stability (ESI) and the smallest emulsion particle size (4.29 μm), followed by CPI and glutelin. The CPI was efficient in forming a gel at 80.6 °C, and glutelin could form the hardest gel at 92.6 °C. CPI and albumin could thus be potential candidates as emulsifying agents, and CPI and glutelin could be used for gelation in food industry. Overall, CPI displayed better amino acid composition and characteristics than the major protein fractions of cumin seeds, and therefore a deep investigation of CPI would be carried out for the application in food industry. Secondly, the effects of pH and NaCl on the structural, physicochemical, and functional properties of CPI were evaluated. The structure of CPI was greatly influenced by the pH adjustment and NaCl addition. The fluorescence intensity (FI) of CPI was reduced as pH reached a value close to 5.0 and the highest α-helix content (18.3%) in CPI was obtained at pH 5.0. The addition of NaCl led to a decrease in the α-helix content and an increase in the β-sheet for CPI. The ζ, Ho, and solubility of CPI were significantly reduced as pH reached 5.0 (p<0.05), whereas the addition of 0.5 and 1.0 M NaCl caused an increase in Ho and a decrease in solubility. CPI showed higher EAI and ESI at pH 7.0 and pH 9.0 with small emulsion droplet size, and the addition of 0.1 M NaCl produced an increase in ESI. At lower NaCl concentration (0.1 M), the EAI wasn’t affected, while the ESI was improved significantly (p<0.05). However, as pH changed to pH 5.0 or the addition of 0.5 M and 1.0 M NaCl, the emulsifying properties of CPI were reduced. All CPI emulsions showed pseudo-plastic behavior, and the apparent viscosity and viscosity coefficient (k) of the CPI emulsions at pH 5.0 were significantly higher than those for the other pH values, and increasing k values were found after the addition of NaCl. The desired emulsifying property of CPI might be obtained at neutral and alkali conditions with the addition of a lower concentration of NaCl. Thirdly, effects of heat treatments at 65, 75, 85 and 95 °C for 30 min on the structure and the emulsifying properties of CPI were investigated. The structure of CPI was remarkably influenced as heating temperature increased while fluorescence intensity decreased. After heat treatments at different temperatures, more protein molecules were unfolded and more compact conformations were formed, the α-helix content of CPI was increased, while the β-sheet content was decreased. A significant increase in the Ho of CPI was found after heat treatments, and the Ho reached 1030.6 for heated CPI at 95 °C. Heat treatments induced the formation of high molecular mass aggregates of CPI, which led to a decrease in the EAI and ESI of heated CPI at different protein concentrations (0.1%, 0.5% and 1.0%). However, the protein absorption in emulsions stabilized by heated CPI gradually increased with heating temperature increasing. Both emulsions stabilized by native and heated CPI showed shear-thinning behavior and exhibited a decrease in their viscosities with protein concentration increasing. Thermal treatments produced different effects on the flow behavior of emulsions formed by various protein concentrations. Indeed, the flow index (n) for heated CPI emulsions decreased for a 0.1% concentration, but increased for protein concentrations of 0.5% and 1.0%. More heated CPI absorbed on the surface of the oil droplet will be helpful for the production of emulsion gel with higher protein concentrations. Furthermore, the effects of high hydrostatic pressure (HHP) treatments (200, 400 and 600 MPa, 15 min) on the structural, physicochemical, and functional properties of CPI were studied. HHP treatments could result in the formation of more aggregates, more pores, irregular conformations, and bigger particle size from the results of SDS-PAGE, atomic force microscope (AFM), and scanning electron microscope (SEM). With pressure increasing, more protein aggregates with large protein molecular mass were formed which influenced the microenvironment of protein and led to a decrease in fluorescence intensity and an increase in α-helix content, a decrease in β-strand for CPI. Surface hydrophobicity of CPI significantly increased after HHP treatments, from 343.35 for native CPI to 906.22 at 600 MPa (p<0.05). HHP treatment at 200 MPa reduced the zeta-potential and solubility of CPI, while having a little effect at 400 and 600 MPa. After HHP treatments, the EAI and ESI of CPI were decreased with a significant increase in droplet size of emulsions (p<0.05). HHP-treated CPI at 400 and 600 MPa could form a heat-induced gel at lower Tgel (68.5 °C and 70.9 °C) with higher storage modulus (G') of 4100 Pa and 4170 Pa, respectively. HHP treatments might be a potential processing method in order to modify CPI making them potential candidates as gelation agent in food matrices. [less ▲]

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See detailPrediction of feed efficiency based on test-day liveweight of dairy cows estimated using animal characteristics and milk mid-infrared spectra
Zhang, Lei ULiege

Doctoral thesis (2021)

Due to the increasing world population, the consumption of milk and dairy products is raising. Optimizing the production of milk under the economic and environmental constraints is a challenge. In this ... [more ▼]

Due to the increasing world population, the consumption of milk and dairy products is raising. Optimizing the production of milk under the economic and environmental constraints is a challenge. In this context, knowing the feed efficiency (FE) of dairy cow is a key issue. Unfortunately, the acquisition of such records at individual and large scales is unfeasible. So, the current thesis aims to fill this gap by developing a FE predictive tool for dairy sector available at large and individual scales. To achieve this objective, the FE was assessed by calculating the ratio of fat and protein corrected milk (FPCM) to dry matter intake (DMI). Although FPCM is already routinely available, this is not the case for DMI. However, a literature equation exists to predict DMI from FCM, live bodyweight (BW) and the number of weeks of lactation. Recently, a methodology using the milk mid-infrared (MIR) spectrometry combined with the animal characteristics was developed to predict test-day BW records, leading to open new perspectives about the use of FE related traits for management and breeding purposes. So, the final achievement of this thesis is the development and the implementation of a FE prediction tool from traits easily recorded by dairy herd improvement (DHI) organizations, including namely the BW estimation. To achieve this objective, 3 main research activities were conducted in this thesis. The first research aimed to increase the calibration set and to apply feature selection algorithms during the modeling in order to improve the BW models' robustness and accuracy. Indeed, the presence of less informative variables in a prediction equation could impact negatively its robustness. Three feature selection algorithms were applied on 280 predictors to select the most informative ones from a dataset containing 5,920 records: partial least squares regression (PLS) combined with sum of ranking difference (SRD), PLS combined with uninformative variables elimination (UVE), and the output of Elastic net regression (EN). Parity, days in milk (DIM), milk yield (MY), and two MIR spectral points were selected as the most relevant variables to predict BW. Validation root mean square errors (RMSEp) of 60 kg were obtained for both PLS and EN regressions employing these 5 predictors, suggesting a better robustness of these models compared to the ones without MIR or using all 277 MIR variables. The RMSE values of validation set coming from another brand of spectrometer were around 64 kg. The second research work focused on the implementation of a BW equation in practice. Indeed, some poor quality BW predictions can be obtained using poor quality spectral data or by applying the model on samples for which the variability was not included in the calibration set. So, the objective of this work was to develop data cleaning methods easy to implement by DHI to ensure the quality of BW predictions. So, 3 data cleaning procedures and their combinations were tested on a DHI dataset containing 346,818 records: the deletion of 1% of extreme high and low predicted values (M1), the deletion of records when the global-H (GH) distance was greater than 5 (M2), and the deletion of records if the absolute fat residual value was higher than 0.30 g/dL of milk (M3). The interest of those procedures was assessed by estimating the root mean square differences (RMSD) between fat, protein, and fatty acids traits predicted by the MIR spectrometry internally and externally. All methods allowed to decrease RMSD, the gain ranged from 0.32% to 41.39%. Based on the obtained results, the “M1 and M2” combination should be preferred to be more parsimonious in the data loss as it had the higher ratio of RMSD gain to data loss. However, to ensure the lowest RMSD, the “M2 or M3” combination was the most relevant. Based on these 2 first works, FE records were easily obtained at large and individual scales and cleaned appropriately. Then, in order to assess the relevancy of the FE tool, the final work of this thesis consisted to study the behaviors of BW and FE predictions obtained from the 5 developed equations within and between lactations as well as per test month and compared them to the ones observed in the literature using reference values. Subsets of Hebei (N=288,607) and Walloon (N=379,472) DHI datasets were used. Even if the BW equations did not differ a lot based on the prediction performances, differences were observed on the DHI datasets and clustered the equations within 2 groups: the ones including 5 predictors and the one using the parity, DIM, MY, and the full MIR spectral data. The final one depicted a more expected evolution within lactation with a drop of BW around 30-50 days in milk and then an increase. This was not observed for the other equations suggesting a lack of MIR information to take into account sufficiently the individual variability of BW. The annual trend observed for this equation was also more expected with a BW drop during the grazing period. However, the differences in FE predictions obtained using BW estimated from different equations were less marked, suggesting a low sensibility of FE predictions to a moderate variation of BW. The validation RMSE reached 0.05 suggesting a good accuracy for this FE indicator. In conclusion, the FE tool developed in this thesis can be implemented by DHI organizations based on the BW equation including milk, parity, DIM, and the 277 MIR spectral points. However, some additional investigations are still needed before the use of a such tool by DHI. Indeed, even if preliminary results obtained in this thesis suggested a moderate heritability of FE trait, a study with the newly developed BW equations could be done as we have observed that the past BW equation tended to overestimate BW. Moreover, knowing the relationships between FE predictions with other traits having economic interest is required before any use. A reflection about the best way to communicate the results to the farmers must be also started. Finally, the FE tool was based on an equation predicting DMI. For the future, it could be also of interest to measure the relevancy of this equation by using DMI reference data. [less ▲]

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See detailSynthesis of furan derivatives from monosaccharides in reaction media based on choline chloride
Istasse, Thibaut ULiege

Doctoral thesis (2021)

In the context of fossil resources dependence and climate change due to green-house gas emissions, increasing efforts are devoted to the synthesis of plastic materials from renewable resources using less ... [more ▼]

In the context of fossil resources dependence and climate change due to green-house gas emissions, increasing efforts are devoted to the synthesis of plastic materials from renewable resources using less energy consuming processes. A possible path to produce plastic resins precursors is the transformation of plant saccharides to furan derivatives like 5-hydroxymethylfurfural (5-HMF) and 2-furfural (2-F). Furan derivatives are obtained through acid-catalyzed dehydration of saccharides and can be converted to new and more performant plastic materials. Their selective synthesis at moderate temperature remains however an important challenge and is the focus of this work. The first part of the research consists in an extensive review of monosaccharides dehydration mechanisms. Monosaccharides can be separated into two categories: ketoses (e.g. fructose) possessing a ketose moiety under acyclic form and aldoses (e.g. glucose) possessing an aldehyde moiety under acyclic form. The dehydration of ketoses through cyclic intermediates and their different reactivities are clarified. The reaction medium components required for their selective conversion to furan derivatives are methodically examined. Aldoses are more abundant in plants than ketoses and also more difficult to convert to furan derivatives. The study reveals why aldoses structure limits their dehydration and how catalysts and reaction media can be combined to enable a selective transformation. Given the promising results achieved with imidazolium chloride ionic liquids according to the literature, reaction media based on melted mixtures of choline chloride and organic acids were investigated as a possibly cheaper alternative. The dehydration of a ketose, fructose, was attempted at 90 °C in different mixtures with the aim to understand the role of each reaction medium components. Through reduction of the amount of organic acid and by increasing the acid strength, an 80% 5-HMF yield could be achieved in only 1h at 90 °C. The addition of small amount of an organic solvent like isopropanol enabled the reaction at 60 °C with a similar selectivity. The potential of choline chloride/organic acids melted mixtures for aldoses dehydration (glucose, mannose, galactose, xylose, arabinose) was then explored. To enable the formation of furan derivatives, boric acid was required for the prior isomerization of aldoses to ketoses. Aldoses transformation remained limited (e.g. 5% 5-HMF yield and 23% glucose conversion after one hour at 90 °C with maleic acid). Combined with α-hydroxyacids however, the reaction was faster and more selective (e.g. 19% 5-HMF yield and 61% glucose conversion after one hour at 90 °C). The synergy between α-hydroxyacids and boric acid was explained by formation of tetrahydroxyborate esters (THBE). Compared to boric acid, THBE reaction with glucose is energetically favored. THBE formation is associated with H3O+ release in the medium increasing its acidity. Dark polymers called humins were the main observed side-product of the reaction and are a major hurdle to the development of selective 5-HMF and 2-F synthesis processes. To better understand and inhibit their formation, humins were produced from different monosaccharides (hexoses, pentoses, 2-deoxyglucose) and analyzed by infrared spectroscopy and nuclear magnetic resonance. Humins formation during ketoses dehydration can be limited using organic solvents but humins production from aldoses persists even in organic reaction media. Those polymers are suspected to form from acyclic monosaccharides after one or several dehydration steps leading to a conjugated structure. The resulting conjugated product is sensitive to aldol addition/condensation with monosaccharides and furan derivatives. The experiments suggest that isomerization catalysts required for furan derivatives synthesis also exacerbate humins formation in two ways: they stabilize monosaccharides acyclic form and therefore expose their carbonyl moiety; humins possess functional groups which interact evenly or more strongly with the catalyst than reaction medium components or monosaccharides. Based on humins structure and a better understanding of their formation, advices are provided regarding the design of new catalysts including transition metals or boronic acids. We suggest that the catalyst should be strongly bonded to an organic structure which must prevent simultaneous interactions of several molecules with the catalytic site. The bulkiness of the organic structure must be precisely controlled to prevent humins of large size to inhibit the catalyst but still enable interaction with monosaccharides. The provided strategy should be valid for choline chloride-based medium as well as other solvents. This research supports the possibility to perform selective dehydration of abundant aldoses (e.g. glucose, xylose) at moderate temperature in commercially available and relatively cheap reaction media based on choline chloride. If polysaccharides depolymerization can be achieved in such media, they will certainly represent a promising path to generate bio-based monomers from renewable resources. [less ▲]

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See detailContribution à l'évaluation du programme de contrôle de l’échinococcose kystique au Maroc
Saadi, Aouatif ULiege

Doctoral thesis (2021)

Cystic echinococcosis (CE) is a major zoonosis, however, it is neglected. It is endemic in several countries around the world, particularly around the Mediterranean. In Morocco, despite the efforts ... [more ▼]

Cystic echinococcosis (CE) is a major zoonosis, however, it is neglected. It is endemic in several countries around the world, particularly around the Mediterranean. In Morocco, despite the efforts carried out within the framework of a national hydatidosis control program (NHCP), initiated in 2007, this zoonosis still presents a major cause of morbidity. Faced with this situation, the establishment of an effective proposal to improve the NHCP is necessary. Our study is based on the principle that, in order to improve the NHCP, we must first analyze and understand its different issues and facets. A multidisciplinary approach was followed, based on the estimation of monetary and non-monetary losses caused by this zoonosis, as well as participatory analyzes of its stakeholders, its implementation and ways of improving it. We were able to raise the multiple challenges facing the NHCP and studied the possibility of establishing a new control strategy, based on the vaccination of sheep and the treatment of dogs. Theoretically capable of eliminating this zoonosis in 15 years, the success of this strategy will indeed depend on the ability of the national program to carry it out and on its acceptability among the population directly concerned. Accurate assessment of the burden disease is essential for sensitizing decision-makers, as it helps prioritize funding for timely control measures. In this objective, a first study was carried out to estimate the economic losses caused by this zoonosis at the national and provincial level by combining financial and non-financial methods. In terms of human health, loss of disability-adjusted life years (DALY), medical costs and productivity losses were estimated. For animals, organ seizure losses at slaughterhouses and production losses caused by reducing milk, fertility, carcass weight and wool production were also estimated. The zDALY indicator, modifying the DALY indicator to include the animal health impacts of zoonotic diseases, was calculated to combine these two components. Monte-Carlo simulations were used to calculate the approximate numerical values. Total losses range from USD 222 million to USD 234 million. DALYs were estimated nationally at 0.5 years per 100,000 person and zDALY at 55 years per 100,000 person. According to these assessments, perceived losses are only the tip of the iceberg, with most of the losses being caused by loss of human productivity in undiagnosed cases and losses in animal production. This study highlighted the enormous losses caused by this zoonosis, throughout Morocco, indicating the need for improved prevention and control measures. The results of the first study showed the persistence of CE in Morocco and the failure that meet NHCP objectives. This prompted us to ask the question of the causes of this failure. To answer this question, a second study on the issues and obstacles that hindered the success of the NHCP was conducted. A qualitative approach was carried out in five regions of Morocco: Rabat-Salé-Kénitra; Béni Mellal-Khénifra; Sous-Masaa; Laâyoune-Sakia El Hamra and Guelmim-Oued Noun. We made the choice for this study to open the framework for application beyond hydatidosis alone, namely rabies and bovine tuberculosis, in order to highlight the common challenges that the control of these zoonoses presents. Participatory observations and 81 individual interviews were conducted with veterinarians, local authorities and slaughterers. The recordings were fully transcribed and the narratives analyzed with R software, using the RQDA package. The study revealed a lack of professional rigor, a lack of legislative framework, as well as an overlap of powers and interests between the different structures, while the multisectoral strategy is essential in the fight against zoonoses. This analysis led to our third study, which analyzed NHCP stakeholders to deepen our understanding of each stakeholder relationship with the program. The third study, therefore aims to analyze the actors of the NHCP in order to identify avenues for improvement and to propose more suitable ways. Stakeholders were identified, and a total of 163 semi-structured interviews were conducted in the same regions as the second study, as well as an inter-ministerial workshop in Rabat. The classic categories of stakeholder analysis, i.e. involvement, interest, importance, influence, priority and power, have been semi-quantified. An analytical framework was proposed combining these categories to evaluate the actors by three attributes: the appropriation of the measures, the political agency and the socio-technical agency. The study highlighted a deficient organization of the diversity of the actors involved, resulting in a deficiency in the three attributes mobilized. This study proposed an analytical and informative approach, particularly useful for an orientation of the fight against zoonoses in which multisectoral coordination is essential. In the search for new CE control strategies, sheep vaccination trials (EG95 vaccine) associated with anthelmintic treatment of dogs were carried out in the Middle Atlas, the region of the country with the highest prevalence. This study presents the analysis of the feasibility and social acceptability of this strategy, the aim of which is to outline an approach for the development of a guide for carrying out such an intervention in the future. Eleven focus groups and sixteen in-depth individual interviews were conducted with breeders, women, local authorities, private doctors and veterinarians, as well as officials from the structures responsible for the potential implementation of the NHCP in parallel with the trials of the vaccine. Recordings were transcribed and analyzed with R software, using RQDA software package. This study highlighted various reservations expressed by the players on the feasibility of the strategy. The study made it possible to collect participants' proposals for a better implementation of this new strategy. These reservations and proposals must imperatively be taken into account for the development of a renewed plan. In conclusion, the study highlighted the impact of CE throughout the Moroccan territory, which causes losses reaching 0.07% of Morocco's GDP. Thus, the qualitative approach allowed us first to understand the functioning of the NHCP in the field, and to propose a scheme for the establishment of a new control strategy, which theoretically, could control this zoonosis in 15 years. [less ▲]

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See detailUne nouvelle hypothèse sur le mécanisme de pacemaking dans les neurones dopaminergiques de la substance noire compacte
Jehasse, Kevin ULiege

Doctoral thesis (2021)

Substantia Nigra pars compacta dopamine neurons are integrated in the nigrostriatal pathways of the basal ganglia. They release dopamine in the striatum to modulate the activity of the different nuclei ... [more ▼]

Substantia Nigra pars compacta dopamine neurons are integrated in the nigrostriatal pathways of the basal ganglia. They release dopamine in the striatum to modulate the activity of the different nuclei from the basal ganglia. Thus, those neurons are involved in motor control, as well as exploration and motivation behaviors. Dopamine release disruption, due to neurodegeneration, leads to various motor impairment (Parkinson Disease) and behavioral diseases. Dopamine release is controlled by the electrical activity of dopamine neurons. The firing pattern of these neurons is controlled by synaptic activity in vivo. They can present a regular firing called “pacemaking”, an irregular firing or a bursting firing. Only the pacemaking activity remains in vitro. This regular firing is therefore sustained and controlled by intrinsic conductances. However, the exact mechanism underlying Substantia Nigra pars compacta dopamine neurons pacemaking activity remains unclear. In fact, blocking one or few conductances only affects the firing frequency but it does not fully inhibit the spontaneous activity. In order to sustain such activity, it has been showed that a small inward current is activated during the slow depolarization phase between two action potentials in ventral tegmental area dopamine neurons (Khaliq and Bean, 2008). Given the similar properties within midbrain dopamine neurons being heterogenous, it is not excluded that their pacemaking is mediated by one and same conductance. We investigated several potential candidates, including the unconventional conductance mediated by ω pores. We used the only known blockers of such pores, 1-(2,4-xylyl)guanidine (XG), in order to verify our hypothesis. We observed that this compound is able to selectively inhibit midbrain dopamine neurons pacemaking activity by blocking one target, without affecting either the burst activity nor the ion channels underlying action potentials. We also observed that the effect of XG still persists even when the pacemaking main modulators are being blocked. These results demonstrate that the XG-sensitive conductance is crucial to sustain the spontaneous activity in midbrain dopamine neurons. We next investigated the presence of ω pores but we did not observe evidence in favor of this hypothesis. However, we managed to isolate a XG-sensitive current occurring during the interspike interval corresponding the pacemaker current described by Khaliq and Bean. We characterized this current and found that it is sustained by Na+ and Cl-. Finally, we investigated whether this current was sustained by the dopamine transporter because it displays similar properties. We used transgenic mice lacking the dopamine transporter in dopamine neurons. We found that the absence of the transporter did not affect either the firing frequency nor XG effect on those neurons. To conclude, even though we did not manage to identify the molecular target of XG, we emphasized a new conductance crucial to sustain pacemaking activity in midbrain dopamine neurons. [less ▲]

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See detailGeneration and data-driven upscaling of open foam representational volume elements
Kilingar, Nanda Gopala ULiege

Doctoral thesis (2021)

In this work, a Representative Volume Element (RVE) generator based on the distance fields of arbitrary shaped inclusion packing is used to obtain morphologies of open-foam materials. When the inclusions ... [more ▼]

In this work, a Representative Volume Element (RVE) generator based on the distance fields of arbitrary shaped inclusion packing is used to obtain morphologies of open-foam materials. When the inclusions are spherical, the tessellations of the resultant packing creates morphologies that are similar to physical foam samples in terms of their face-to-pore ratio, edge-to-face ratio and strut length distribution among others. Functions that combine the distance fields can be used to obtain the tessellations along with the necessary variations in the strut geometry and extract these open-foam morphologies. It is also possible to replace the inclusion packing with a predefined set of inclusions that are directly extracted from CT-scan based images. The use of discrete level-set functions results in steep discontinuities in the distance function derivatives. A multiple level-set based approach is presented that can appropriately capture the sharp edges of the open-foam struts from the resultant distance fields. Such an approach can circumvent the discontinuities presented by the distance fields which might lead to spurious stress concentrations in a material behavior analysis. The individual cells are then extracted as inclusion surfaces based on said combinations of the distance functions and their modifications. These surfaces can be joined together to obtain the final geometry of the open-foam morphologies. The physical attributes of the extracted geometries are compared to the experimental data. A statistical comparison is presented outlining the various features. The study is extended to morphologies that have been extracted using CT-scan images. With the help of mesh optimization tools, surface triangulations can be obtained, merged and developed as finite element (FE) models. The models are ready to use in a multi-scale study to obtain the homogenized material behavior. The upscaling can help assess the practical applications of these models by comparing with experimental data of physical samples. The material behavior of the RVEs are also compared with the experimental observations. To increase the computational efficiency of the study, a neural network based surrogate is presented that can replace the micro-scale boundary value problem (BVP) in the multi-scale analysis. The neural networks are built with the help of modules that are specifically designed to predict history dependent behavior and are called Recurrent Neural Networks (RNN). The surrogates are trained to take into account the randomness of the loading that complex material undergo during any given material behavior analysis. [less ▲]

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See detailReduced tillage increases grain yield through improving soil properties and water use efficiency
Li, Shengping ULiege

Doctoral thesis (2021)

A primary challenge of our time is to attain high food security for a growing world population with reduced investment and ensuring environmental sustainability. Conservation tillage practices have ... [more ▼]

A primary challenge of our time is to attain high food security for a growing world population with reduced investment and ensuring environmental sustainability. Conservation tillage practices have received wide international attention to address this challenge because of their effect on soil physical properties and grain yield. However, there is a lack of knowledge about the relationships between soil physical properties and grain yield, especially for soil water repellency. The dynamic of soil physical properties during the growth period is also seldom taken into account to understand a suitable soil physical environment for plant growth. Moreover, although it is well known that conservation tillage practices could affect soil water repellency through hydrophobic substances and pore structure, most of the studies have only focused on hydrophobic substances due to the complexity of soil pore structure measurement and quantification. This results in limited knowledge about the relationship between soil pore structure and soil water repellency. In this study, we used a long-term field experiment located at the Dryland Farming Experimental Station in Shouyang, Shanxi Province, in northern China to study the seasonal changes of soil physical properties (e.g. bulk density, penetration resistance, porosity, mean weight diameter, least limiting water range, and plant available water). We also assessed how these soil physical properties influence grain yield, especially reveal the mechanism of how soil water repellency affects grain yield from the perspective of soil water availability. To better understand the effects of hydrophobic substances and pore structure on soil water repellency, another long-term experimental location was conducted in Gongzhuling, Jinlin Province, northeast China. The treatments were conventional tillage with residue removal (CT), reduced tillage with residue incorporation (RT), and no-tillage with residue mulching (NT) in both of the fields. The main results of this thesis are as follows: (1) Soil physical properties (e.g. bulk density, penetration resistance, pore size distribution, mean weight diameter, least limiting water range, and plant available water) were significantly influenced by tillage management, soil depth, and growth period (P < 0.05). At 0-5 cm layer, NT was the highest in soil bulk density on April 27th, but there was no significant difference among the three tillage management on July 7th, and NT was lower than RT and CT on September 10th. In addition, bulk density, porosity, S index, and mean weight diameter showed irregular and different relationships with grain yield during the growth period, especially there were no significant relationships between these soil physical properties and grain yield (P > 0.05). These results suggested that these soil physical properties were ineffective indicators for grain yield. Besides, the range of least limiting water range was narrower than plant available water during the growth period and more sensitive to assess soil water availability under the three treatments. NT significantly increased the lower limit of LLWR, which made it more difficult for root water uptake. Hence, RT presented higher corn yield compared to NT, even if the water content remained lower. Redundancy analysis further indicated that maize yield was mainly driven by a lower limit of LLWR and penetration resistance. (2) Soil organic carbon and microbial biomass carbon, both of which are hydrophobic substances, were higher in RT and NT treatments than in CT treatment. Microbial biomass carbon had a closer relationship with the water repellency index than soil organic carbon and more fully explained the impact of tillage on soil water repellency. The RT and NT treatments increased the porosity of pores that were 55-165 μm in diameter and it had a positive relationship with ethanol sorptivity and the water repellency index, respectively. However, there was no significant link with soil water repellency properties when the pores were greater than165 μm in diameter. The RT and NT treatments increased sorptivity by enhancing porosity and connectivity, and decreased water sorptivity by increasing soil surface area, which occurred because the area and possibility of contact between hydrophobic substances and soil water increased. (3) Both water sorptivity and water repellency index had effects on soil water availability (e.g. plant available water, least limiting water range, and soil water storage) that could affect plant growth. The effect of soil water repellency on soil water content became more obvious with the decrease in soil moisture following rainfall, which was also influenced by rainfall intensity. Although both water repellency index and water sorptivity can reflect the nature of soil water repellency, soil water sorptivity had a significant influence on grain yield, whereas water repellency index had no direct effect on grain yield. In addition, water sorptivity was the most favorable for grain yield improvement compared with soil organic carbon, mean weight diameter, penetration resistance, and total porosity. In conclusion, the thesis reveals the mechanism of how soil tillage management affects grain yield by changing soil physical properties. We found that grain yield was mainly driven by a lower limit of least limiting water range and penetration resistance. LLWR was an aggregative indicator including not only soil penetration resistance but also air porosity and soil water potential, which can better explain the change of grain yield under the long-term tillage management in the semi-arid region. Furthermore, the effect of conservation tillage on SWR is a result of the interactions between pore structure and hydrophobic substances. It is necessary to take into account both pore structure and hydrophobic substances when studying the impacts of SWR on soil processes. SWR also had the potential influence on grain yield by changing soil water availability and the effect of SWR on crop yield was worthy of further study under conservation tillage practices. The grain yield under RT treatment was highest by increasing water sorptivity, LLWR, and WUE. From this, we conclude that RT treatment is the most effective tillage practice compared to CT and NT treatments from the perspective of grain yield. [less ▲]

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See detailContribution of Mycobacterium bovis gene Rv3671c in acid resistance and replication
Lin, Weidong ULiege

Doctoral thesis (2021)

The survival of Mycobacterium in the host is largely attributed to its ability to resist the acidic environment. Recently, it has been found that a Mycobacteria tuberculosis mutant cannot maintain ... [more ▼]

The survival of Mycobacterium in the host is largely attributed to its ability to resist the acidic environment. Recently, it has been found that a Mycobacteria tuberculosis mutant cannot maintain intracellular pH in phagosomes in the absence of Rv3671c, which encodes Mycobacterial acid resistance protease (Marp). The aim of this study is to study the effect of Marp in acid resistance and the growth performance of Mycobacterium bovis and decipher the underlying working mechanisms. We have expressed the periplasmic domain of Marp in Escherichia coli and prepared monoclonal antibodies (MAb) against Marp. The serine proteinase activity of Marp was verified by using β-casein as a substrate. Monoclonal antibodies were tested with recombinant or and natural Marp protein from M. bovis. Meanwhile, we have constructed a knockout mutant (ΔMarp) using a mycobacteriophage, and validated its integrity by PCR and western blot. Besides,a complemented strain (ΔMarpComp) and a strain overexpressing the Rv3671c gene (PmvRv3671) were built by using plasmid pMV261. The growth rates of these strains were compared to that of the wild type M. bovis An5. Raw264.7 macrophages were infected at multiplicities of infections of 10 (MOI=10). After culture in standard 7H9 medium to the early logarithmic phase, the strains were transferred into 7H9 medium at pH 6.6 and pH 5.0 and maintenance solution at pH 6.6 and pH 4.5. The results show that while they all survive in 7H9 medium at pH 5.0 or pH 6.6 and maintenance buffer at pH 4.5, the viability at day 14th of the over-expressing strain PmvRv3671 is significantly higher than that of wild-type strain M. bovis, ΔMarpComp and ΔMarp. After comparing their corrected survival rates, it can be observed that the acid resistance abilities of all strains significantly decrease between days 5 and 14. When exposed to pH 4.5-citrate maintenance solution for a long time, their acid-resistance abilities become weaker. In Raw264.7 macrophages stimulated with IFNγ, the replication rate of the PmvRv3671 is significantly higher than that of An5, ΔMarp and ΔMarpComp. So, Rv3671c over-expressing strain shows a better growth ability than the other three strains under acidic environments. In conclusion, the Rv3671c gene is not only related to acid resistance but also affects the growth of M. bovis. To understand the panorama of the working mechanisms of Marp, we investigated proteins interacting with Marp. We used Mycobacteria tuberculosis Protein Chip to screen the proteins binding to Marp. The bacterial two-hybrid system was then used to validate the interacting proteins. The results show that among 295 interacting proteins, 52 displayed stronger binding. Interactions of seven candidates were verified by using the bacterial two-hybrid system. The biological functions were analyzed with String, Uniprot, BioCyc, and Gene Ontology databases. We concluded that these 7 proteins are mainly responsible for two biological functions: the growth of M. bovis and the binding of GDP or ATP. Therefore, we hypothesize that the mechanisms of the acid resistance are associated with these Marp interactants. The results of the present study provide a basis for further deciphering the complete model and working mechanisms of Marp in M. bovis. [less ▲]

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See detailUnveiling the specialized metabolism of Streptomyces lunaelactis spp.
Martinet, Loïc ULiege

Doctoral thesis (2021)

The decline in the number of new antibiotics discoveries, related in parallel with an acceleration and generalization of the bacterial resistance phenomenon, the unfolding of the global health crisis ... [more ▼]

The decline in the number of new antibiotics discoveries, related in parallel with an acceleration and generalization of the bacterial resistance phenomenon, the unfolding of the global health crisis, linked to the emergence of new viral pandemics, as well as the agro-industrial needs for new natural products less impacting the environment and human health, are examples of current driving elements that encourage research of new natural products. Over the past ten years or so, technological innovations allowing on one hand, the high-throughput and low-cost sequencing of bacterial genomes, and on the other, the high-resolution detection and identification of compounds, have offered an unmatched framework for discovery. During last decade, many innovative strategies have emerged, with the aim of providing access to biomolecules buried in nature. One of them is the bioprospecting of new microorganisms in ecological niches, described as extreme and so far unexplored, in order to maximize the chances of discovering new biomolecules. Streptomyces are soil bacteria, which actively participate in the recycling of organic biomass, and are also known to have an extremely developed secondary metabolism. Indeed, these Actinobacteria provide more than 50% of natural molecules of microbial origin used in human or animal medicine (antibacterial, antifungal, anti-tumor, etc) and in agro-industry (herbicides, insecticides, etc). The search for microorganisms native to karstic habitat called moonmilk, has led to the discovery of new strains of Streptomyces, including the recently described Streptomyces lunaelactis species. The aim of this work is to characterize the specialized metabolome associated with the Streptomyces lunaelactis species, including identification of the molecules produced by this microorganism and determination of the genes responsible for their biosynthesis. Through a comparative metabologenomic approach using 18 bacterial strains belonging to the S. lunaelactis species, this work has revealed their ability to produce bioactive molecules. Accordingly, the results of genome mining study of S. lunaelactis, combined with metabolomics studies, made it possible to evaluate the genetic predispositions of this species to produce specialized metabolites, as well as to experimentally validate some of these predictions. This work provides an overview on this species’ specialized metabolome and confirms that not only this microorganism, but also other Streptomyces derived from moonmilk, are abundant sources of new natural products. In addition, this work also exposes the risks associated with the dereplication of bacterial strain banks and investigates an innovative approach, which focuses on the evaluation of biosynthetic potential of strains within a single species, which shows a great promise in the search for new natural products. [less ▲]

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See detailStudy on extraction technics of sweet potato leaf flavonoids, sustained release of its nanoparticles, and sweet potato leaf fortified bread
Liu, Jiang ULiege

Doctoral thesis (2021)

The previous studies of sweet potato leaf polyphenols were mainly focus on the non-flavonoids part (phenolic acids), there weren’t enough study on the flavonoids part. Chemically, flavonoids have the ... [more ▼]

The previous studies of sweet potato leaf polyphenols were mainly focus on the non-flavonoids part (phenolic acids), there weren’t enough study on the flavonoids part. Chemically, flavonoids have the specific structure of a 15-carbon skeleton, which consists of two phenyl rings (A and B) and a heterocyclic ring (C), and can be abbreviated as C6-C3-C6 structure. Firstly, ultrasonic-microwave synergistic extraction (UMSE) was used to extract flavonoids from sweet potato leaves (SPL) by response surface methodology (RSM). The optimal conditions for flavonoids extraction were 1:40 (g/mL) of solid-liquid ratio, 57 °C of extraction temperature, 76 s of extraction time and 72 % (v/v) ethanol for 2 times of extraction, and the highest flavonoids yield from SPL was 5.1 %. After purification, the flavonoids purity reached up to 76.1 (%, DW). The result of high performance liquid chromatography (HPLC) revealed 11 compounds including astragalin, quercetrin, 4,5-chlorogenic acid, isoquercitrin, tiliroside, quercetin, 3,4,5-chlorogenic acid, caffeic acid, kaempferol, myricetrin and rhamnetin in sweet potato leaf flavonoids (SPLF), which possessed good antioxidant activity compared to soy isoflavones, Ginkgo biloba extract and propolis flavone. Secondly, the effect of heat treatment, high hydrostatic pressure (HHP) treatment, pH, light, temperature and simulated digestion on the stability of SPLF was studied. Heat treatment at 75 °C for 90 min or HHP treatment at 600 MPa for 30 min didn’t cause significant effect on SPLF. Heat treatment at 100 °C for 60 min and 90 min led to a decrease in antioxidant activity by 20 % and 25 % respectively, while pH 7.0 and 8.0 significantly decreased amount of SPLF by approximately 75 %, decreased antioxidant activity by about 30 % and 47 % separately. Light treated samples recorded a decrease in SPLF by 52 % and antioxidant activity by 24 %. No significant effect on SPLF was observed for samples stored at -18, 4 °C or room temperature (RT) (≈ 20 °C). The retention of flavonoids and antioxidant activity was 45 % and 56 %, individually in SPLF after simulated digestion. Thirdly, nanoparticles of SPLF were prepared by freeze-drying encapsulation using 2 % (g/mL) maltodextrin, which showed the highest stability with high absolute zeta potential (-41.6 mV) and encapsulation efficiency (EE) (59.0 %), low mean particle size (277.4 nm) and polydispersity index (PDI) (0.417). Confocal laser scanning microscopy (CLSM) and infrared spectrum provided the evidence. After simulated oral, gastric and intestinal digestion, nanoparticles additionally reserved 16, 31, 28 % of flavonoids and 16, 16, 10 % of antioxidant activity, separately, compared with the sample without encapsulation, which could be intuitively demonstrated by scanning electron microscopy (SEM). Finally, SPL was used to substitute 1, 2, 3.5 and 5 % (w/w) of wheat flour to make bread. 1 % SPL could change the bread color significantly, which could be clearly distinguished by human eyes. The hardness and chewiness of the crumb increased with increased SPL level. When adding 5 % of SPL to the flour, specific volume of the bread shrank in half, compared with the control. Pores in the crumb became deteriorating and disintegrating when the adding of SPL was higher than 3.5 %. Total polyphenols content (TPC) and total flavonoids content (TFC) of the bread increased 6-fold and 10-fold, and antioxidant activity enhanced 10-fold, separately when adding 5 % SPL to the flour. The addition of SPL won’t alter volatile compounds of the bread, but suppressed the generation of typical bread odors significantly. Overall, SPL (no more than 1 %) could be supplemented to the flour to make bread with high TPC (2-fold), TFC (2.5-fold), excellent antioxidant activity (3-fold), and no significant adverse effect on the physical characteristics and flavor. [less ▲]

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See detailStudy on extraction technics of sweet potato leaf flavonoids, sustained release of its nanoparticles, and sweet potato leaf fortified bread
Liu, Jiang ULiege

Doctoral thesis (2021)

The previous studies of sweet potato leaf polyphenols were mainly focus on the non-flavonoids part (phenolic acids), there weren’t enough study on the flavonoids part. Chemically, flavonoids have the ... [more ▼]

The previous studies of sweet potato leaf polyphenols were mainly focus on the non-flavonoids part (phenolic acids), there weren’t enough study on the flavonoids part. Chemically, flavonoids have the specific structure of a 15-carbon skeleton, which consists of two phenyl rings (A and B) and a heterocyclic ring (C), and can be abbreviated as C6-C3-C6 structure. Firstly, ultrasonic-microwave synergistic extraction (UMSE) was used to extract flavonoids from sweet potato leaves (SPL) by response surface methodology (RSM). The optimal conditions for flavonoids extraction were 1:40 (g/mL) of solid-liquid ratio, 57 °C of extraction temperature, 76 s of extraction time and 72 % (v/v) ethanol for 2 times of extraction, and the highest flavonoids yield from SPL was 5.1 %. After purification, the flavonoids purity reached up to 76.1 (%, DW). The result of high performance liquid chromatography (HPLC) revealed 11 compounds including astragalin, quercetrin, 4,5-chlorogenic acid, isoquercitrin, tiliroside, quercetin, 3,4,5-chlorogenic acid, caffeic acid, kaempferol, myricetrin and rhamnetin in sweet potato leaf flavonoids (SPLF), which possessed good antioxidant activity compared to soy isoflavones, Ginkgo biloba extract and propolis flavone. Secondly, the effect of heat treatment, high hydrostatic pressure (HHP) treatment, pH, light, temperature and simulated digestion on the stability of SPLF was studied. Heat treatment at 75 °C for 90 min or HHP treatment at 600 MPa for 30 min didn’t cause significant effect on SPLF. Heat treatment at 100 °C for 60 min and 90 min led to a decrease in antioxidant activity by 20 % and 25 % respectively, while pH 7.0 and 8.0 significantly decreased amount of SPLF by approximately 75 %, decreased antioxidant activity by about 30 % and 47 % separately. Light treated samples recorded a decrease in SPLF by 52 % and antioxidant activity by 24 %. No significant effect on SPLF was observed for samples stored at -18, 4 °C or room temperature (RT) (≈ 20 °C). The retention of flavonoids and antioxidant activity was 45 % and 56 %, individually in SPLF after simulated digestion. Thirdly, nanoparticles of SPLF were prepared by freeze-drying encapsulation using 2 % (g/mL) maltodextrin, which showed the highest stability with high absolute zeta potential (-41.6 mV) and encapsulation efficiency (EE) (59.0 %), low mean particle size (277.4 nm) and polydispersity index (PDI) (0.417). Confocal laser scanning microscopy (CLSM) and infrared spectrum provided the evidence. After simulated oral, gastric and intestinal digestion, nanoparticles additionally reserved 16, 31, 28 % of flavonoids and 16, 16, 10 % of antioxidant activity, separately, compared with the sample without encapsulation, which could be intuitively demonstrated by scanning electron microscopy (SEM). Finally, SPL was used to substitute 1, 2, 3.5 and 5 % (w/w) of wheat flour to make bread. 1 % SPL could change the bread color significantly, which could be clearly distinguished by human eyes. The hardness and chewiness of the crumb increased with increased SPL level. When adding 5 % of SPL to the flour, specific volume of the bread shrank in half, compared with the control. Pores in the crumb became deteriorating and disintegrating when the adding of SPL was higher than 3.5 %. Total polyphenols content (TPC) and total flavonoids content (TFC) of the bread increased 6-fold and 10-fold, and antioxidant activity enhanced 10-fold, separately when adding 5 % SPL to the flour. The addition of SPL won’t alter volatile compounds of the bread, but suppressed the generation of typical bread odors significantly. Overall, SPL (no more than 1 %) could be supplemented to the flour to make bread with high TPC (2-fold), TFC (2.5-fold), excellent antioxidant activity (3-fold), and no significant adverse effect on the physical characteristics and flavor. [less ▲]

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See detailMulti-scale characterization of transport in heterogeneous porous and fractured aquifer media using innovative heat and solute tracer tests
Hoffmann, Richard ULiege

Doctoral thesis (2021)

Characterization of subsurface mass and energy transport in heterogeneous porous and fractured aquifer media is particularly challenging due to existence of preferential flowpaths and dynamic matrix ... [more ▼]

Characterization of subsurface mass and energy transport in heterogeneous porous and fractured aquifer media is particularly challenging due to existence of preferential flowpaths and dynamic matrix processes at multiple scales. The main contribution of the present work is to combine solute and highly diffusive tracer information with the objective to improve the understanding of the actual transport processes and the predictive capacity of models. The use of innovative tracers such as heat or inert dissolved gases leads to different sensitivities to preferential flowpaths and matrix processes due to the broad variation of their diffusion coefficient values. This in turn allows a more realistic consideration of the heterogeneity patterns in the geological media and a better quantification of the associated uncertainty in model predictions. Field campaigns were performed in different geological formations with injections of: (1) heat and a solute in alluvial sediments; (2) dissolved gases, heat and uranine in a porous/fractured chalk system, (3) salt and water with higher and lower temperature (than the natural groundwater background temperature) in a weathered and fissured granite system in India. These field campaigns provided information on the evolution of concentration and temperature as function of time (breakthrough curves). The observations were interpreted with regards to peak time, peak value and slope of the tailing, taking into account the variation of the diffusion coefficient value of the different tracers. First, a joint heat and solute tracer experiment, previously carried out in alluvial sediments, was used to study the heterogeneity and for prior (i.e., parameter) uncertainty investigation. Monte Carlo simulations were used to revisit the current state of knowledge. For example, an increase in hydraulic conductivity with depth (due to the local spatial heterogeneity of the sediments) could now be realistically implemented in the aquifer simulation using the numerical calculator HydroGeoSphere (HGS). The Monte Carlo simulations were also used for a Euclidean distance-based sensitivity analysis relating model input and output uncertainty. It was shown that heat transport is more sensitive to heterogeneous patterns compared to solute tracer transport. Second, the joint injection of uranine and dissolved gases and their recovery (forced gradient experiment) in a porous/fractured chalk emphasized the influence of the specific (i.e., fracturing) aquifer heterogeneity on higher diffusive tracers. A channel model (analytical solution with explicit fracture numbers and apertures) was used to simulate the transport of helium, the gas with the highest diffusion coefficient tested. Then, using HGS, the simulation of flow, transport of solutes and heat transfer allowed to test the influence of matrix diffusion at different time and spatial scales by varying the diffusion coefficient of the tracer species. Third, the injection of hot and cold water in a weathered and fissured granite system in India, allowed the study of the actual and differential release of heat from the matrix to the fracture fluid and vice versa. A deterministic model solution using HGS showed that the width of the discrete fracture that is supposed to represent the fracture tested in the field had a significant effect on the temperature simulations. The results of the present PhD thesis clearly emphasize the importance and usefulness of these new tracers as well as their added value for an advanced aquifer characterization, to obtain a realistic assessment of the inherent heterogeneity of the different investigated groundwater systems. The latter is required for reliable simulations of mass and energy transport in the dynamic subsurface. [less ▲]

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See detailReconstruction of the Gulf Stream variability since 1940 using a variational inverse method and study of its interaction with the North Atlantic Oscillation
Watelet, Sylvain ULiege

Doctoral thesis (2021)

In this study, the Gulf Stream’s (GS) response to the North Atlantic oscillation (NAO) is investigated by generating an observation-based reconstruction of the GS path between 70° and 50°W since 1940 ... [more ▼]

In this study, the Gulf Stream’s (GS) response to the North Atlantic oscillation (NAO) is investigated by generating an observation-based reconstruction of the GS path between 70° and 50°W since 1940. Using in situ data from WOD, SeaDataNet, ICES, Hydrobase3 and ARGO floats, a harmonized database of more than 40 million entries is created. A variational inverse method implemented in the software DIVA (Data-Interpolating Variational Analysis) allows the production of time series of monthly analyses of temperature and salinity over the North Atlantic (NA). These time series are used to derive two GS indices: the GS North Wall (GSNW) index for position and the GS Delta (GSD) index as a proxy of its transport. We find a significant correlation (0.37) between the GSNW and the NAO at a lag of 1 year (NAO preceding GS) since 1940 and significant correlations (0.50 and 0.43) between the GSD and the NAO at lags of 0 and 2 years between 1960–2014. We suggest this 2-year lag is due to Rossby waves, generated by NAO variability, that propagate westwards from the center of the NA. This is the first reconstruction of GS indices over a 75-year period based on an objective method using the largest in situ dataset so far. This enhanced tracking and quantification of the GS confirms and extends the temporal scope of this property: NAO+ phases lead to a stronger and more northward GS, and conversely for NAO− phases. The teleconnections between the NAO and the variability of the GS were extensively studied these last years, often exhibiting time delays between both phenomena. These time lags, usually ranging between 0–2 years, are sometimes explained by the hypothesis of baroclinic Rossby waves generated by the NAO in the central NA and travelling westward before interacting with the GS. In this study, we use a numerical hindcast at an eddy-resolving resolution (1/12°) from the DRAKKAR project to examine the occurrence and properties of such Rossby waves between 1970–2015, thus including a large pre-TOPEX/Poseidon period. Through the use of a two-dimensional Radon Transform (2D-RT) on Hovmöller diagrams of the Sea Surface Height (SSH), a methodology easily portable to other oceanic model outputs, we show evidence of baroclinic Rossby waves travelling at 39°N at a speed of 4.17 cm/s. This study extends the period over which Rossby waves have been found that far north to a much longer period, which reinforces the findings of previous works. These results are consistent with the time lags observed between the NAO and the GS transport while the GS latitudinal shifts might obey additional processes. The Barents Sea, located between the Norwegian Sea and the Arctic Ocean, is one of the main pathways of the Atlantic Meridional Overturning Circulation. Changes in the water mass transformations in the Barents Sea potentially affect the thermohaline circulation through the alteration of the dense water formation process. In order to investigate such changes, we present here a seasonal atlas of the Barents Sea including both temperature and salinity for the period 1965–2016. The atlas is built as a compilation of datasets from the World Ocean Database, the Polar Branch of Russian Federal Research Institute of Fisheries and Oceanography, and the Norwegian Polar Institute using the DIVA tool. DIVA allows for a minimization of the expected error variance with respect to the true field. The atlas is used to provide a volumetric analysis of water mass characteristics and an estimation of the ocean heat and freshwater contents. The results show a recent "Atlantification" of the Barents Sea, that is a general increase of both temperature and salinity, while its density remains stable. The atlas is made freely accessible as handy NetCDF files to encourage further research in the Barents Sea physics. [less ▲]

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See detailItinéraire d'un formateur formé
De Lemos Esteves, Frédéric ULiege

Master's dissertation (2021)

Portfolio professionnel rédigé dans le cadre du Master de Spécialisation en Pédagogie de l'Enseignement Supérieur

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See detailEfficient and flexible implementation of an interfacing Python-based tool for numerical simulations of fluid-structure interaction problems
Thomas, David ULiege

Doctoral thesis (2021)

Applications involving a solid structure actively interacting with a surrounding fluid, referred to as fluid-structure interaction (FSI), are constantly gaining interest in fundamental or industrial ... [more ▼]

Applications involving a solid structure actively interacting with a surrounding fluid, referred to as fluid-structure interaction (FSI), are constantly gaining interest in fundamental or industrial research and development. Such a multi-physics system is characterized by a complex dynamics which requires technically advanced methods to be studied. An accurate understanding of FSI systems becomes a key factor in the current trend of producing lighter and more flexible industrial designs. Nowadays, numerical simulations are extensively used to produce high-fidelity FSI models for various engineering applications. The typical approach considered in this thesis performs the coupling between two independent solvers, each of them being specifically designed to solve the governing equations for one particular physics. In this context, this thesis presents the development of an original coupling environment called CUPyDO. It is designed for the coupling of independent single-physics solvers within a unified architecture based on a Python wrapping methodology. The development of CUPyDO has been conducted with the aim of producing a tool that leverages computing efficiency and accuracy, coupling flexibility and user-friendliness while circumventing some limitations and improving some other aspects of the existing solutions. The tool gathers state-of-the-art coupling methods which are deeply reviewed in this work. This includes major capabilities such as under-relaxed coupling algorithms, non-matching interface meshes and multi-core parallelization. The modern Python wrapping technology used in CUPyDO provides easy access to all the features through a high-level API which can be further customized and extended with minimal effort. Furthermore, the same wrapping technology provides a flexible black-box coupling with various existing standalone solvers without any architectural or algorithmic adaptation to be performed in the coupling environment. The implementation and the capabilities of CUPyDO are demonstrated and verified by simulating several FSI test cases for transonic aeroelastic flutter, vortex-induced vibrations and conjugate heat transfer. The test cases are also used to assess the coupling tool in terms of robustness, efficiency and accuracy. The results are successfully validated against experimental and numerical reference data found in the literature, and some usability guidelines are drawn. Furthermore, the coupling flexibility is highlighted by using various structural solvers through the different test cases. The coupling tool is used for the aeroelastic study of a very flexible flat plate wing with various geometrical configurations. In a first step, the linear flutter velocity and frequency are sought and compared with experimental data with good agreement. In a second step, the post-flutter aeroelastic response is simulated for some configurations of the plate and it is found that the system is characterized by a supercritical Hopf bifurcation. For one particular plate configuration, two distinct post-flutter limit cycle oscillations are observed depending on the initial structural perturbation and on the occurrence of aerodynamic nonlinearities. This further highlights the importance of using high-fidelity coupled models for representing nonlinear aeroelastic solution that reduced-order linear models are not able to predict. [less ▲]

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See detailDeep Reinforcement Learning for the Control of Energy Storage in Grid-Scale and Microgrid Applications
Boukas, Ioannis ULiege

Doctoral thesis (2021)

The European and worldwide directives and targets for renewable energy integration, motivated by the imminent need to decarbonize the electricity sector, are imposing severe changes to the conventional ... [more ▼]

The European and worldwide directives and targets for renewable energy integration, motivated by the imminent need to decarbonize the electricity sector, are imposing severe changes to the conventional electrivcal power system. The inherent unpredictability of the instantaneous energy production from variable renewable energy sources (VRES) is expected to make the reliable and secure operation of the system, a challenging task. Flexibility, and in particular, energy storage is expected to assume a key role in the integration of large shares of VRES in the power system, and thus, in the transition towards a carbon-free electricity sector. One of the main storage mechanisms that can facilitate the integration of VRES is energy arbitrage, i.e. the transfer of electrical energy from a period of low demand to another period of high demand. In this thesis, we investigate and develop novel operating strategies for maximizing the value of energy arbitrage from storage units at different scales (i.e. grid-scale or distributed) and in different settings (i.e. interconnected or off-grid). The decision-making process of an operator optimizing the energy arbitrage value of storage is an inherently complex problem, mainly due to uncertainties induced by: i) the stochasticity of market prices and ii) the variability of renewable generation. In view of the great successes of deep reinforcement learning (DRL) in solving challenging tasks, the goal of this thesis is to investigate its potential in solving problems related to the control of storage in modern energy systems. Firstly, we address the energy arbitrage problem of a storage unit that participates in the European Continuous Intraday (CID) market. We develop an operational strategy in order to maximize its arbitrage value. A novel modeling framework for the strategic participation of energy storage in the European CID market is proposed, where exchanges occur through a process similar to the stock market. A detailed description of the market mechanism and the storage system management is provided. A set of necessary simplifications that constitutes the problem tractable are described. The resulting problem is solved using a state-of-the-art DRL algorithm. The outcome of the proposed method is compared with the state-of-the-art industrial practices and the resulting policy is found able to outperform this benchmark. Secondly, we address the energy arbitrage problem faced by an off-grid microgrid operator in the context of rural electrification. In particular, we propose a novel model-based reinforcement learning algorithm that is able to control the storage device in order to accomodate the different changes that might occur over the microgrid lifetime. The algorithm demonstrates generalisation properties, transfer capabilities and better robustness in case of fast-changing system dynamics. The proposed algorithm is compared against two benchmarks, namely a rule-based and a model predictive controller (MPC). The results show that the trained agent is able to outperform both benchmarks in the lifelong setting where the system dynamics are changing over time. In the context of an off grid-microgrid, the optimal size of the components (i.e. the capacity of photovoltaic (PV) panels, storage) depends heavily on the control policy applied. In this thesis, we propose a new methodology for jointly sizing a system and designing its control law that is based on reinforcement learning. The objective of the optimization problem is to jointly find a control policy and an environment over the joint hypothesis space of parameters such that the sum of the initial investment and the operational cost are minimized. The optimization problem is then addressed by generalizing the direct policy search algorithms to an algorithm we call Direct Environment Search with (projected stochastic) Gradient Ascent (DESGA). We illustrate the performance of DESGA on two benchmarks. First, we consider a parametrized space of Mass-Spring-Damper (MSD) environments and control policies. Then, we use our algorithm for optimizing the size of the components and the operation of a small-scale autonomous energy system, i.e. a solar off-grid microgrid, composed of photovoltaic panels, batteries. On both benchmarks, we show that DESGA results in a set of parameters for which the expected return is nearly equal to its theoretical upper-bound. Finally, we provide the general conclusions and remarks of this thesis and we propose a list of future research directions that emerge as an outcome of this work. [less ▲]

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See detailPresent and future sensitivity of the Antarctic surface mass balance to oceanic and atmospheric forcings: insights with the regional climate model MAR
Kittel, Christoph ULiege

Doctoral thesis (2021)

Recent Global Warming has caused widespread ice losses from the Antarctic Ice Sheet (AIS) leading to an increase in mean sea level. By influencing the ice dynamics and the mass of water that accumulates ... [more ▼]

Recent Global Warming has caused widespread ice losses from the Antarctic Ice Sheet (AIS) leading to an increase in mean sea level. By influencing the ice dynamics and the mass of water that accumulates on the continent, the surface mass balance (SMB, i.e, the difference between snow accumulation and ablation at the surface of the ice sheet) contributes to sea-level variations. A better knowledge of how present and future SMB will change is therefore needed to refine sea-level-rise estimates. With the aim of identifying the driving processes from different components of the climate system (from the surface of the ocean to high-elevation clouds), we reconstruct and project the Antarctic SMB using the regional climate model MAR developed at ULiège, over 1980--2100. The results of MAR have been first compared to diverse observations to evaluate its performance. We gathered observations of several types (near-surface climate and snow accumulation) to guarantee the robustness of our results and conclusions based on our climate modeling. A first objective of this thesis was to determine to what extent the recent changes at the ocean surface can exert a direct feedback on the atmosphere and SMB. Our simulations with perturbed sea-ice concentration and sea-surface temperature around Antarctica reveal that strong and persistent katabatic winds prevent most atmospheric changes induced by the ocean to penetrate inland. This suggests a limited influence of the ocean surface on the Antarctic SMB. We focused afterwards on the sensitivity of the SMB to atmospheric warmings projected by global models using high-emission scenarios (RCP8.5 and ssp585). Higher temperatures are projected to increase SMB on the grounded ice as a result of stronger snowfall while the future SMB over the ice shelves should be dominated by higher meltwater-runoff values (compromising the stability of ice shelves) and is consequently projected to decrease. Leaving aside the role of the ocean on the thinning of ice shelves, increasing surface melt should however remain weak under the Paris Agreement limiting potential ice-shelf collapses and accelerated Antarctic ice losses. However, our results suggest a large spread in melt increase over the ice shelves during the 21st century resulting in large uncertainties in their potential disappearance. Given the important role of ice shelves in limiting the acceleration of Antarctic ice losses (as they restrain the grounded ice to flow into the ocean), the third subject of this thesis has been devoted to the physical drivers explaining differences in increased summer melt over the Antarctic ice shelves. Although the melt increase results from higher greenhouse-gas concentrations, differences in projected melt increases arises from liquid-containing clouds. These clouds re-emits more longwave energy towards the surface, increasing melt over the ice shelves and later favouring absorption of solar energy again strengthening melt. In conclusion, we investigate the sensitivity of the Antarctic SMB to different components of the climate system over 1981--2100. Uncertainties linked with the grounded Antarctic SMB essentially depend on the projected increased rates in snowfall associated with higher temperatures while uncertainties in the ice-shelf SMB decrease are related to cloud properties with more liquid-containing clouds leading to a stronger decrease of the ice-shelf SMB. [less ▲]

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See detailDynamic Stall modelling at low Reynolds Numbers
Boutet, Johan ULiege

Doctoral thesis (2021)

Dynamic stall is described by Mac Croskey et al. as a phenomenon that occurs on airfoils subjected to unsteady motion with high amplitude or frequency. The phenomenon occurs at higher angles of attack and ... [more ▼]

Dynamic stall is described by Mac Croskey et al. as a phenomenon that occurs on airfoils subjected to unsteady motion with high amplitude or frequency. The phenomenon occurs at higher angles of attack and lift values than steady stall. Dynamic stall can also be associated with the shedding of a vortex from the leading edge. This vortex usually affects the flow around the airfoil such that it increases further the instantaneous lift acting on the wing and produces a nose-down pitching moment when the vortex is swept toward the trailing edge. The modeling of dynamic stall is challenging even in 2D because it involves separated and turbulent flow. Typical 2D approaches range from semi-empirical, such as the Leishman-Beddoes (LB) or the ONERA models, to Computational Fluid Dynamic (CFD) methods. This thesis makes two major contributions towards the development of a dynamic stall model for 3D wings at low Reynolds number based on the 2D Leishman-Beddoes model. The LB model has not been conceived with very low Reynolds number in mind. The first contribution of this thesis is the development of a modified Leishman-Beddoes model able to handle dynamic stall at low Reynolds number ranges. It uses Wagner theory for the incompressible attached flow and adapts the stall onset criterion by Sheng et al to low Reynolds numbers. In order to calibrate and validate the model, an extensive set of dynamic stall experiments were carried out in a low-speed wind tunnel for three airfoils: a flat plate, a NACA0012 wing, and a NACA0018 wing. This modified Leishman-Beddoes model results in better aerodynamic load predictions than the original model for low and medium reduced pitch rates. For the highest reduced pitch rates, neither model yields fully satisfactory predictions. The second contribution is the development of a closed-form unsteady attached flow model for 3D wings. It combines the 2D Wagner unsteady aerodynamic loads calculation with Prandtl’s lifting line, by means of the unsteady Kutta-Joukowsky theorem. This new model was validated by means of comparison to the predictions of an unsteady vortex lattice model for impulsive and oscillatory motions of wings of different planforms and aspect ratios. An additional validation involved the calculation of the flutter speed and frequency of finite rectangular wings with pitch and plunge degrees of freedom and comparison to the predictions of an aeroelastic vortex lattice formulation. [less ▲]

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See detailCaractérisation et modélisation des nappes d’eau souterraine au voisinage de petites retenues d'eau d'irrigation en zone de socle : cas de Kierma et de Mogtédo (Burkina Faso)
Bambara, Apolline ULiege

Doctoral thesis (2021)

Surface water reservoirs have been massively built in sub-Saharan Africa to provide an alternative source of water during the drought. They contribute to the socio-economic development and food security ... [more ▼]

Surface water reservoirs have been massively built in sub-Saharan Africa to provide an alternative source of water during the drought. They contribute to the socio-economic development and food security of populations through the practice of irrigated agriculture in the dry season. Unfortunately, these surface water reservoirs tend to dry up prematurely before the harvests. One solution to these irrigation water shortages is to ensure the conjunctive use of surface and groundwater. In this respect, a better knowledge of groundwater resources is essential for integrated water resources management. The objective of this work is to contribute to a better understanding of the surface water reservoirs in the vicinity of irrigation water reservoirs for agricultural purposes. The present study is part of the "Programme d'Appui au Développement de l'Irrigation (PADI)" (Irrigation Development Support Programme) of the “Ministère de l’Agriculture et de l’Aménagement Hydraulique”, Burkina Faso. The catchment areas of Kierma (area of ≈100 km2) and Mogtédo (≈500 km2), which all have surface water reservoirs for irrigation, were chosen for the study. They are located in two different climatic and geological contexts. The methodological approach was based on several steps. The first consisted in characterising the geometry and structure of the aquifer systems of the two basins, mainly through the analysis of lithologs and electrical geophysical investigations (electrical resistivity tomography, ERT). Then, the hydrodynamic properties of the aquifers were determined on the basis of the interpretation of slug tests and the results of pumping tests from the drilling campaigns. This was followed by the characterisation of the interactions between the surface water reservoirs and the groundwater tables through the spatio-temporal analysis of the piezometric chronicles and water levels in the reservoirs coupled with the physico-chemical analyses of the groundwater. The natural and local recharge of groundwater tables was estimated using methods based on the water balance. Finally, the results of these hydrogeophysical and hydrogeological investigations were used to develop a hydrological model integrated with the HydroGeoSphere programme to simulate surface and groundwater flows in the Kierma basin. The results indicate that the aquifer system of these basins consists of a layer of alteration which may incorporate alluvium and a layer of fissured/fractured rock. These aquifers contain hydraulically connected water bodies. The results also show that the small surface water reservoirs are in almost permanent interaction with the groundwater bodies while favouring local recharge. The rate of local recharge is a function of the geological context and the texture of the sediments in the reservoirs. This approach, applied to the surface water reservoirs of Kierma and Mogtédo, has made it possible to estimate an average local recharge of 1,350 ± 540 mm/year in Kierma and 1,080 ± 540 mm/year in Mogtédo for average annual natural recharge of 82 mm/year in Kierma and 48 mm/year in Mogtédo. In addition, the hydraulic conductivity values are between 0.01 and 2 m/day in Kierma and between 1×10-4 and 0.2 m/day in Mogtédo. These conductivities could make it possible to pump into large diameter dug wells with a significant flow rate of between 0.5 and 120 m3/day in Kierma and between 0 and 10 m3/day in Mogtédo to compensate for the early drying up of the surface water reservoirs for irrigation. In this way, plots of crops with a surface area of between 100 and 22,300 m2 in Kierma and between 0 and 1,800 m2 in Mogtédo could be irrigated daily. All the geological and hydrogeological information made it possible to carry out a numerical simulation that reproduces the observed underground flows and the interactions between the surface water reservoirs and the underground water tables. [less ▲]

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See detailFinite-Element Modeling of Thin Wires Including Skin- and Proximity Effects
Velasco, Jonathan ULiege

Doctoral thesis (2021)

The presence of conductors is indispensable in the design and optimization of electromagnetic devices. Conductors appear in different shapes and forms, such as solid wires, cables, and plates. In complex ... [more ▼]

The presence of conductors is indispensable in the design and optimization of electromagnetic devices. Conductors appear in different shapes and forms, such as solid wires, cables, and plates. In complex systems, we might encounter mul- tiple conducting domains, all interacting with one another, affecting the design’s performance. The primary purpose of a conductor is to transport electric current within a sys- tem, in other words conducting electrons under an electric field’s influence. From a microscopic standpoint, these electrons will collide, and energy will be transmit- ted, having a direct impact on the power dissipation of the system as the resistance increases. This phenomenon is commonly known as Joule loss or electromagnetic heating due to ohmic power dissipation. Conversely, Ampere’s law states the re- lationship between the flow of current around an enclosed domain and a magnetic field. This magnetic field will have a high impact on those parts of the system in their vicinity, increasing losses due to their mutual inductance and ohmic re- sistance. As frequency increases, the current density becomes more prominent around the conductors’ surfaces, and the joule loss becomes frequency-dependent due to skin and proximity effects. This is known as the eddy current phenomenon. In large systems, the study of conducting domains can be cumbersome when the ratio between their transversal and axial dimensions is long. The challenge of modeling thin wires lies in the accurate solution of the field problem at higher frequencies, where both: skin and proximity effects are impactful, requiring fine discretization around the thin wire’s surface. This thesis presents an accurate and inexpensive treatment of thin conducting wires in a finite element (FE) framework for the magnetic vector potential magne- todynamics formulation in frequency-domain. First, the concept of field-truncation and analytical correction is introduced. The thin wire semi-analytical (SA) tech- nique is then compared against the results of a fully discretized model (FM) in a single conductor and multiple parallel conductors in two-dimensions. The accu- racy at a broad range of frequencies and spacing between conductors highlights the proximity effects. Lastly, the formulation is extended to include the system’s excitation source (e.g., voltage, current). Global sources enable calculating the input impedance and ultimately losses in multi-turn coils, including both skin- and proximity effects. [less ▲]

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See detailRenouveau des approches participatives pour la fabrique de la Smart City
Schelings, Clémentine ULiege

Doctoral thesis (2021)

Detailed reference viewed: 113 (13 ULiège)
See detailPostkantisme et révolution algébrique. Étude sur la philosophie des mathématiques de Hegel et Bolzano.
Mazurkiewicz, Stany ULiege

Doctoral thesis (2021)

Le texte comporte cinq chapitres. Un premier chapitre est consacré à la « révolution algébrique » : nous y explicitons les éléments qui nous semblent les plus pertinents pour comprendre en quoi la ... [more ▼]

Le texte comporte cinq chapitres. Un premier chapitre est consacré à la « révolution algébrique » : nous y explicitons les éléments qui nous semblent les plus pertinents pour comprendre en quoi la question des mathématiques et de leur histoire joue un rôle significatif dans la relation de Hegel et de Bolzano à Kant. Ensuite, suivent trois chapitres consacrés respectivement à Kant, Hegel et Bolzano. Les deux derniers possèdent une même structure tripartite. Il s’agit, dans un premier temps, de montrer que l’on trouve bien traces dans l’œuvre du philosophe étudié d’une réception de la « révolution algébrique » telle que nous l’exposons, de même que d’une prise de conscience des implications importantes qui en découlent. Il en va alors, dans un deuxième temps, de montrer qu’il existe chez Hegel et chez Bolzano une conscience du caractère contradictoire entre les mathématiques nouvelles et les critères épistémologiques qui étaient ceux de Kant, et qu’il en découle alors une nécessité à refonder un système philosophique nouveau, que l’on qualifiera de « postkantien ». Il faudra alors, dans un troisième temps, voir comment se mettent en place ces systèmes nouveaux en question, notamment à l’aune des problèmes mathématiques qui auront émergé chemin faisant. Pour finir, un cinquième chapitre, conclusif, entend mettre en avant les questions qui seront apparues comme étant les plus pertinentes au cours de ce travail de reconstruction concernant la comparaison systématique des œuvres de Hegel et de Bolzano dans le domaine de l’épistémologie des mathématiques. [less ▲]

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See detailImpact of environmental drivers and phytoplankton diversity on the dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) cell quotas: laboratory experiments and natural variability.
Royer, Colin ULiege

Doctoral thesis (2021)

In the last two decades, particular interest has been given to the cycle of dimethylsulfide (DMS), a climate active gas, and its precursors the dimethylsulfoniopropionate (DMSP) and the dimethylsulfoxide ... [more ▼]

In the last two decades, particular interest has been given to the cycle of dimethylsulfide (DMS), a climate active gas, and its precursors the dimethylsulfoniopropionate (DMSP) and the dimethylsulfoxide (DMSO). DMS is involved in the Earth’s radiation budget while the DMS(P,O) are produced by a wide variety of micro- and macroalgae, corals, bacteria, or angiosperms in response to diverse environmental stresses. Several functions have been suggested for these sulfur compounds such as antioxidants, cryoprotectants, overflow mechanisms, osmolytes, zooplankton deterrents or signalling compounds. This research aims at improving the knowledge about the antioxidant role of DMS(P,O) within three major phytoplankton groups: diatom (i.e. Skeletonema costatum), Prymnesiophyceae (i.e. Phaeocystis globosa) and dinoflagellate (i.e. Heterocapsa triquetra). The experimental results demonstrate that cellular DMS(P,O) have the ability to lower cellular reactive oxygen species concentrations produced during high-light and chemically-induced oxidative stresses; thus supporting the antioxidant function. However, the initial DMS(P,O) concentrations of each species are not informative of their ability to tolerate a further oxidative stress, and their concentrations do not increase in high-light grown cells. The DMS(P,O) may then act as antioxidants without being part of the antioxidant response of the cell. We recommend analysing more constituents of the antioxidant system (i.e. enzymes, carotenoids, redox buffer) along with DMS(P,O) by-products and DMSP-lyase activity to better understand the cellular function of DMSP. Field measurements in the North Sea, including the Belgian Coastal Zone (BCZ) and the Northern North Sea (NNS), bring additional information on the DMS(P,O) variations. While abiotic parameters (nutrients, temperature, and incident light) influence the Chlorophyll-a (Chl-a) concentrations in the BCZ, this impact is not reflected in the DMS(P,O) concentrations. The latter depend on the succession of low- and high-DMSP producing species (i.e. diatoms and Phaeocystis, respectively). In the NNS in August, no distinct pattern can be drawn for the DMS(P,O) evolution regarding the phytoplankton diversity or abiotic parameters. Investigated by correlations between DMS(P,O), photoprotective pigments and incident light, the antioxidant function is not observed for this short-term period of sampling in a temperate sea. Based on Chl-a linear regressions, DMS(P,O) concentrations are successfully estimated with two distinct relationships for diatoms and Prymnesiophyceae in the BCZ. However, this estimation lacks accuracy in the NNS due to the mixed phytoplankton community observed. Further work will provide a better understanding about the antioxidant function – especially on the field – and its association with the phytoplankton diversity in temperate regions such as the North Sea. [less ▲]

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See detailDimensionality reduction for geophysical inversion in highly structured subsurface environments
Lopez Alvis, Jorge ULiege

Doctoral thesis (2021)

For highly structured subsurface, the use of strong prior information in geophysical inversion produces realistic models. Machine learning methods allow to encode or parameterize such models with a low ... [more ▼]

For highly structured subsurface, the use of strong prior information in geophysical inversion produces realistic models. Machine learning methods allow to encode or parameterize such models with a low dimensional representation. These methods require a large number of examples to learn such latent or intrinsic parameterization. By using deep generative models, inversion is performed in a latent space and resulting models display the desired patterns. However, the degree of nonlinearity for the generative mapping (which goes from latent to original representation) dictates how useful the parameterization is for tasks other than mere compression. After recognizing that changes in curvature and topology are the main cause of such nonlinearity, an adequate training for a variational autoencoder (VAE) is shown to allow the application of gradient-based inversion. Data obtained in highly structured subsurface may also be represented by low-dimensional parameterizations. Compressed versions of the data are useful for prior falsification because they allow modeling marginal probability distributions of structural parameters in a latent space. An objective way based on cross-validation is proposed to choose which compression technique retains information relevant to high-level structural parameters. Inversion and prior falsification using dimensionality reduction provide a computationally efficient framework to produce realistic models of the subsurface. This framework is successfully applied to a field dataset using a prior distribution assembled from distinct patterns resemble a realistic geological environment including deformation and intrafacies variability. [less ▲]

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See detailContributions to uncertainty analysis of computational models with application to hydrodynamics and physically-based hydrological simulations
Goffin, Louis ULiege

Doctoral thesis (2021)

Modelling numerically natural phenomena like river flows, flows on hydraulic structures or groundwater flows, helps engineers quantifying them in order to organise human activities on the one hand and ... [more ▼]

Modelling numerically natural phenomena like river flows, flows on hydraulic structures or groundwater flows, helps engineers quantifying them in order to organise human activities on the one hand and design mitigation measures on the other hand. These models take, as input data, quantities that are uncertain because of their variability in time and space, and because of our lack of knowledge to represent them accurately. Uncertainty analysis aims at quantifying the impact of these uncertain input data on the outputs of the model. Several uncertainty analysis methods exist, including the well-known Monte Carlo method (MCM). However, it requires to evaluate the numerical model many times, which is not compatible with computationally expensive 2-D hydrodynamic models for instance. Other uncertainty analysis methods (Point Estimates Method (PEM), Perturbance Moment Method (PMM) and Stochastic Response Surface Method (SRSM)), based on simplifying assumptions, allow to decrease significantly the number of model evaluations. Non-hydraulic simple tests performed with these methods showed that they produce very good results compared to MCM. In order to consider testing and challenging these methods on more computationally expensive examples, a fast and robust 1-D steady shallow water model is developed. It includes an original sliding domain strategy used along with the nonlinear Krylov accelerator. After a validation step on academic tests, this new model showed an excellent scalability behaviour. Compared to CasADi, a state-of-the-art optimization tool, the new model produced better performance results. This new model allows to apply MCM to a real world 1-D shallow water case. The assessment of the flooding risk of a field located on the banks of the Haine River in Belgium is done through MCM, PEM and PMM. PMM showed in this example to produce an excellent compromise between the computation cost and the accuracy. Moreover, results were very close to the ones produced by MCM. After this successful hydraulic application for PMM, this method is applied to a 2-D horizontal shallow water flow in the Romanche River in the French Alps. Thanks to an uncertainty analysis approach, this emblematic example studies the sediment transport potential after several dam removals. Results reflect an increased sediment movement potential after dam removal even if the uncertainty analysis highlights a relatively wide confidence interval on the amount of sediments transported. Over the needs for fast computing models for the application to hydrodynamics, the automatic run of an uncertainty analysis requires also robust models. Groundwater partially saturated models can present convergence issues as reported in the scientific literature. In this thesis, a chapter tries to tackle this problem by proposing a promising method. Homotopy is tested and gives encouraging results in terms of convergence rate. [less ▲]

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See detailWhen Integrating Care is not Just a Question of Care: The Case of the Implementation of the Plan “Integrated Care for Better Health” for Chronic Patients in the Belgian Health Sector
De Winter, Mélanie ULiege

Doctoral thesis (2021)

This qualitative and inductive doctoral research makes a contribution to public policy sciences by analysing different aspects of the process pertaining to the implementation of a specific public policy ... [more ▼]

This qualitative and inductive doctoral research makes a contribution to public policy sciences by analysing different aspects of the process pertaining to the implementation of a specific public policy in the Belgian health sector: the “Integrated Care for Better Health” plan (IC4BH), launched on 19 October 2015 with the intention of integrating care with regard to chronic patients in Belgium. Based on an ethnographic approach, this research draws on several data collection methods: interviews (N=24), focus groups (N=7), direct observation (N=97 — corresponding to 213 hours of observation), documentary analysis (operational documents) and a multifocused literature review. This manuscript is comprised of seven different chapters. The first chapter is dedicated to methodological aspects, while the next four chapters each correspond to a specific paper (published or as yet unpublished) summarized in an abstract at the beginning of each of those chapters. Each paper deals with a precise research question in order to study different dimensions pertaining to the implementation of the IC4BH plan. The first paper (Chapter 2) addresses the question of how the particular Belgian federal configuration may have had an influence on the implementation of this public policy in the health care sector in Belgium, and, more specifically, on the implementation gap that is apparent when comparing expected and real outcomes in terms of the IC4BH plan implementation. The second paper (Chapter 3) focuses on the pilot project phenomenon, regarded as an object for research, trying to understand how the use of multidisciplinary pilot projects as implementation instruments contributed to reshaping the modes of public governance in the Belgian health sector, in a context of transition and ongoing devolution. The third paper (Chapter 4) tackles the issue of knowing how the use of pilot projects as implementation instruments structured horizontal collaboration between the parties involved in a pilot project. It would seem that the use of the pilot project instrument created the conditions allowing the progressive emergence of specific forms of organisation, taking the form of collaborative care networks, and more specifically, of what could be called community-based integrated care networks. Eventually, the fourth paper (Chapter 5) combines the results of three different studies in an inductive secondary analysis, and presents a cross-level approach of the concept of empowerment, one of the integrated care components, which is viewed as an umbrella term in the scientific literature. The paper analyses how the polysemy of this concept might have an influence on its collective operationalisation, when different health care stakeholders have to work together. After having developed additional empirical elements in Chapter 6, the discussion focuses on certain presuppositions, shortcomings, ambiguities, paradoxes and absurdities, all of which were identified during the ethnographic fieldwork carried out as part of this doctoral research and that might have contributed to the emergence of the previously noted implementation gap. The empirical material collected as part of this ethnographic research is first analysed by mobilising, inter alia, the analytical framework produced by Vreugdenhil et al. (2010) pertaining to the project phenomenon. Second, the notions of co-creation and process inclusivity are discussed in the context of the implementation of the pilot projects’ loco-regional action plans. Later, the research perspectives identified thanks to this doctoral research are presented before concluding the discussion. Last, but not least, a general conclusion is presented. [less ▲]

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See detailÉtude de valorisation du phosphogypse par désulfuration et par ajout à la stabilisation des sols gonflants
Oumnih, Safae ULiege

Doctoral thesis (2020)

The production of phosphoric acid from phosphate rock generates a large amount of waste in the form of phosphogypsum "PG". The storage strategy and management of this amount of phosphogypsum is a serious ... [more ▼]

The production of phosphoric acid from phosphate rock generates a large amount of waste in the form of phosphogypsum "PG". The storage strategy and management of this amount of phosphogypsum is a serious problem. The reuse or recycling of this waste remains limited despite the efforts made in this regard, because of the environmental risks that certain toxic elements (i.e. As, Ba, Cd, Cr, and Pb) could generate. The recovery of phosphogypsum has been studied using two approaches, namely desulphurization, which produces sulfur dioxide SO2, used in the synthesis of sulfuric acid, and the stabilization of bentonite intended for road construction. Desulfurization has made it possible to develop an alternative technique for upgrading PG and producing sulfur dioxide “SO2”, following attack by a strong acid in the presence of a metal catalyst “iron”. The results obtained showed that the leaching of PG with acid alone does not make it possible to reduce the sulphates of ions dissolved in SO2. However, if the leaching is carried out in the presence of iron, the release of SO2 gas is observed. The calculated values of ΔGr and ΔHr made it possible to prove the possibility of the reactions involved and to discuss the experimental results obtained. The stabilization of bentonite by adding phosphogypsum and lime as aggregates for road construction has been investigated, as well as the effect of these aggregates on cementitious properties has been discussed. Properties examined include chemistry (XRF), mineralogy (XRD, IR), calorimetry (ATD / TG), mechanical strength, and microstructure (SEM) of the mortar based on different mixtures of bentonite, phosphogypsum and lime. The results showed that the addition of lime and PG involves the formation of new nanocrystalline phases (CSH, stratlingite) and the disappearance of certain minerals such as portlandite. The CSH gel appeared in the mixture with 8% lime, while stratlingite was neoformed in the mixture with 8% L + 8% PG. These nanocrystalline phases are responsible for improving the mechanical strength due to the pozzolanic reaction. [less ▲]

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See detailÉtude de valorisation du phosphogypse par désulfuration et par ajout à la stabilisation des sols gonflants
Oumnih, Safae ULiege

Doctoral thesis (2020)

The production of phosphoric acid from phosphate rock generates a large amount of waste in the form of phosphogypsum "PG". The storage strategy and management of this amount of phosphogypsum is a serious ... [more ▼]

The production of phosphoric acid from phosphate rock generates a large amount of waste in the form of phosphogypsum "PG". The storage strategy and management of this amount of phosphogypsum is a serious problem. The reuse or recycling of this waste remains limited despite the efforts made in this regard, because of the environmental risks that certain toxic elements (i.e. As, Ba, Cd, Cr, and Pb) could generate. The recovery of phosphogypsum has been studied using two approaches, namely desulphurization, which produces sulfur dioxide SO2, used in the synthesis of sulfuric acid, and the stabilization of bentonite intended for road construction. Desulfurization has made it possible to develop an alternative technique for upgrading PG and producing sulfur dioxide “SO2”, following attack by a strong acid in the presence of a metal catalyst “iron”. The results obtained showed that the leaching of PG with acid alone does not make it possible to reduce the sulphates of ions dissolved in SO2. However, if the leaching is carried out in the presence of iron, the release of SO2 gas is observed. The calculated values of ΔGr and ΔHr made it possible to prove the possibility of the reactions involved and to discuss the experimental results obtained. The stabilization of bentonite by adding phosphogypsum and lime as aggregates for road construction has been investigated, as well as the effect of these aggregates on cementitious properties has been discussed. Properties examined include chemistry (XRF), mineralogy (XRD, IR), calorimetry (ATD / TG), mechanical strength, and microstructure (SEM) of the mortar based on different mixtures of bentonite, phosphogypsum and lime. The results showed that the addition of lime and PG involves the formation of new nanocrystalline phases (CSH, stratlingite) and the disappearance of certain minerals such as portlandite. The CSH gel appeared in the mixture with 8% lime, while stratlingite was neoformed in the mixture with 8% L + 8% PG. These nanocrystalline phases are responsible for improving the mechanical strength due to the pozzolanic reaction. [less ▲]

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See detailSome Effects of Evaporation in Binary Mixtures
Rabani, Ramin ULiege

Doctoral thesis (2020)

Evaporation of thin films of polymer solutions or of a partially miscible binary mixtures have many industrial applications related for instance to painting, coating, inkjet printing, or the fabrication ... [more ▼]

Evaporation of thin films of polymer solutions or of a partially miscible binary mixtures have many industrial applications related for instance to painting, coating, inkjet printing, or the fabrication of photovoltaic devices. Thus, a detailed understanding of the physical mechanisms that drive and influence structure formation in such films is of high scientific and industrial value. This thesis explores different physical phenomena involved in such systems, and aims at producing novel insights into the dynamics of thin evaporating film of binary mixtures. Four different questions are analyzed, that correspond to four published, or to be published papers. The first two are concerned with polymer solutions, while partially miscible mixtures are analyzed in the other two. First, we examine the formation of a skin layer at the free surface of a thin evaporating film of a polymer solution. A composition-dependent diffusion coefficient is considered in the liquid phase, which allows describing the gelation and skin formation at the liquid-gas interface. In addition, a realistic model of the evaporation flux, which is based on thermodynamic principles, is proposed. As interesting result, a possible immediate gelation, which is related to a very high evaporation flux, is predicted by our approach. This immediate gelation thus prevents all Marangoni convection in the system. In the second subject, Rayleigh-Bénard-Marangoni instabilities in a thin evaporating film of a polymer solution are analyzed and the importance of concentration dependent diffusion coefficient, viscosity, and relaxation time is examined using the framework of linear stability theory. The analysis is non-trivial because evaporative mass loss naturally leads to a time-dependent reference solution. As a key result of the linear stability analysis, we emphasize the presence of two distinct modes of instability in the system. The first one is monotonic, and corresponds to stationary convective cells. The conditions for its appearance are shown to be in good agreement with previous experimental work. The second mode of instability is oscillatory and is related to the viscoelastic properties of polymer solutions. Regions in the parameter space are identified, where an oscillatory instability should occur. This provides interesting indications on the conditions under which this phenomenon could be observed in future experiments. The third question considered in the thesis consists in exploring the possibility of phase separation in a sessile drop of a partially miscible binary mixture. First, experimental results obtained in the context of a collaboration with ULB (Brussels) are presented. Then a 1-D diffusive model is built to describe the beginning of evaporation in such systems. This model considers the physics of the gas layer above the mixture and its interactions with the liquid. An important result consists in the numerical determination of some conditions that are required for phase separation to occur during the evaporation of the liquid phase. In the last studied problem, we focus on the dynamics of phase separation and evaporation phenomena in a thin evaporating film of a partially miscible binary mixture. A 2-D diffusive and non-isothermal phase-field model is introduced and numerically solved to describe the dynamics of the system and to assess the competition between evaporation and phase separation. Depending on the leading mechanism, different types of morphology can appear in the separating mixture, which are analyzed in detail. We also examine the mid- and long-term evolution of the system. At last, we describe an experimental setup and the associated results obtained in our collaboration with ULB, that nicely confirm our theoretical and numerical predictions about the morphologies that can be created by evaporation and phase separation. [less ▲]

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See detailParcours forestiers du Nord du Maroc: changements spatio-temporels et étude du comportement de pâturage des caprins
Chebli, Youssef ULiege

Doctoral thesis (2020)

Au Nord du Maroc, l’espace forestier et sylvopastoral a toujours été considéré comme une partie intégrante du système alimentaire des caprins, et par conséquent, de l'élevage extensif. Néanmoins, la ... [more ▼]

Au Nord du Maroc, l’espace forestier et sylvopastoral a toujours été considéré comme une partie intégrante du système alimentaire des caprins, et par conséquent, de l'élevage extensif. Néanmoins, la chèvre reste considérée comme une espèce dévastatrice de ces formations forestières. Notre travail a démontré qu’entre 1984 et 2014, le couvert forestier et sylvopastoral du Nord du Maroc a reculé de 25%, et que le surpâturage n’est pas le seul facteur de cette dégradation. Le surpâturage interagit plutôt avec d'autres moteurs, tels que l’expansion de l’agriculture, l’augmentation de la population, les incendies, et la déforestation. Les niveaux de dégradation des forêts et des espaces sylvopastoraux, dépendent essentiellement de l'intensité d'interaction entre les différents moteurs. Par ailleurs, les pâturages forestiers constituent bien une source importante de fourrage pour les chèvres. Cependant, en raison de la saisonnalité de la disponibilité des fourrages et de l'absence d’une stratégie de gestion des pâturage et d’alimentation du troupeau, les chèvres ne sont pas en mesure d'assurer régulièrement leurs besoins énergétiques. Par conséquent, des stratégies de gestion et d'alimentation du troupeau dans le temps et l’espace doivent être élaborées, notamment, à l’aide d’aliments alternatifs, tels que les grignons d’olive et les raquettes de cactus. [less ▲]

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See detailRéfugiés kurdes de Turquie dans l'Ouest de la France et en Belgique de 1977 à nos jours
Rondeau, Coline ULiege

Doctoral thesis (2020)

Dans une perspective croisée, notre étude s’appuie sur des sources écrites et orales inédites qui mettent en évidence des enseignements socio-historiques des migrations des Kurdes de Turquie dans l’Ouest ... [more ▼]

Dans une perspective croisée, notre étude s’appuie sur des sources écrites et orales inédites qui mettent en évidence des enseignements socio-historiques des migrations des Kurdes de Turquie dans l’Ouest de la France et en Belgique. Les différents temps des migrations (accords de main-d’œuvre, regroupements familiaux, demandes d’asile) des Kurdes ont permis de retracer les « carrières migratoires » de ces hommes et de ces femmes. Leurs parcours migratoires sont au croisement de parcours administratifs et de parcours de vie qui interrogent les conditions de vie, les circulations des Kurdes en Turquie (déplacements forcés, service militaire, protecteurs de villages) et leurs migrations vers la France et la Belgique (routes empruntées, transports utilisés). Leurs installations et déménagements successifs les confrontent à des procédures administratives diverses (demandes d’asile, invitations à quitter le territoire, regroupements familiaux, mariages, naturalisations) nécessitant des stratégies de visibilisation et/ou d’invisibilisation, la mobilisation de réseaux et de solidarités multiples (villageoises, familiales, amicales, politiques). Les différentes générations de Kurdes recomposent des territoires, créent des associations déplaçant, de fait, le conflit turco-kurde en raison d’appartenances plurielles. Ces espace-temps des « carrières migratoires » des Kurdes interrogent les normes, les subjectivités, les expressions de la kurdicité et les rapports entretenus par les Kurdes avec leurs terres d’origine. [less ▲]

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See detailGrignons d’olive et raquettes de cactus dans l’alimentation des caprins du Nord du Maroc
El Otmani, Samira ULiege

Doctoral thesis (2020)

Au Nord du Maroc, le cheptel caprin joue un rôle économique majeur par sa contribution à plus de 68% aux revenus des ménages. Cependant, l’alimentation des troupeaux est principalement basée sur les ... [more ▼]

Au Nord du Maroc, le cheptel caprin joue un rôle économique majeur par sa contribution à plus de 68% aux revenus des ménages. Cependant, l’alimentation des troupeaux est principalement basée sur les parcours forestiers, caractérisés par une dégradation continue et une forte variabilité quantitative et qualitative saisonnière de l’offre fourragère, responsables de la faible productivité du cheptel. Par conséquent, il s’avère nécessaire d’identifier et de valoriser en alimentation caprine des nouvelles ressources alimentaires localement disponibles. Les grignons d’olive (Olea europea) et les raquettes de cactus (Opuntia ficus indica) sont deux ressources alternatives largement disponibles dans la région du Nord du Maroc et valorisables en alimentation des ruminants. Pour introduire ce type de matières premières dans l’alimentation du cheptel caprin, il est nécessaire de connaître leur valeur nutritive ainsi que leurs effets sur les performances de production et la qualité des produits caprins. Ce travail a été réalisé dans l’objectif d’étudier (i) la valeur nutritive des ressources alternatives qui sont les grignons d’olive et raquettes de cactus, (ii) leur effet sur la production et la qualité du lait chez les chèvres en lactation, (iii) leur effet sur la qualité de la carcasse et de la viande chez les chevreaux, ainsi que (iv) leur effet sur la flore bactérienne ruminale de la race caprine locale du Nord du Maroc Béni Arouss. Ainsi, pour déterminer la qualité nutritionnelle des grignons d’olive et des raquettes de cactus, les études de l’effet du mode et de la période d’extraction d’huile sur les grignons d’olive, et de l’effet de l’âge et de la période de collecte sur les raquettes de cactus ont été réalisées. Les grignons d’olive ont été collectés mensuellement, durant la période de production d’huile d’olive qui va du mois de novembre à janvier, auprès des unités de trituration utilisant le procédé d’extraction par pression mécanique, ou de centrifugation à 2 ou 3 phases. Les raquettes de cactus épineux ont été collectées selon l’âge (jeunes de l’année et matures de l’année précédente) chaque quinzaine entre les mois d’avril et juin. D’après les résultats, les grignons d’olive issus de l’extraction par centrifugation à 2 phases ont la plus faible teneur en matière sèche et en fibres, et la teneur la plus élevée en extractif non-azoté et en tannins totaux et hydrolysables. Ces grignons étaient plus rapidement fermentescibles que ceux issus de la centrifugation à 3 phases et de la pression mécanique. Les grignons d’olive obtenus par pression mécanique sont significativement les moins digestibles. La matière sèche, les protéines et l’extractif non-azoté ont été linéairement affectés par la période d'extraction. La production de gaz, les paramètres de digestibilité in vitro et la digestibilité enzymatique de la matière sèche et organique ont changé significativement avec la période et le processus d'extraction. Par conséquent, la composition chimique des grignons d’olive et leur digestibilité dépendaient principalement du processus et de la période d'extraction d’huile. Concernant les raquettes de cactus, les stades jeunes contiennent plus d'eau, de protéines, d'extrait éthéré et de composés phénoliques, et moins de matière minérale et de fibres. Les paramètres de production de gaz et de digestibilité n'ont pas été affectés par l'âge, alors que la digestibilité in vitro de la matière organique et la production de biomasse microbienne étaient plus élevées avec les jeunes raquettes. La composition chimique, la production de gaz et les paramètres de digestibilité des raquettes de cactus ont été affectés par la période de collecte. Les résultats permettent de conclure que les grignons sont caractérisés par une qualité nutritionnelle modeste qui nécessite un enrichissement en azote, et que les grignons d’olive issus de la centrifugation à 2 phases sont les plus intéressants du point de vue nutritionnel, et que cependant leur teneur élevée en eau limite leur durée de conservation. Quant aux raquettes de cactus, elles présentent une source d’eau durant les périodes sèches avec la qualité d’un bon fourrage pour les ruminants. Pour étudier l’effet de l’incorporation des grignons d’olive et des raquettes de cactus sur les performances et la qualité des produits caprins, une étude a été menée sur des chèvres en lactation. Quarante-quatre chèvres multipares de race Béni Arouss ont été réparties en 4 groupes qui recevaient en complémentation de la ration de base composée du foin d’avoine, un concentré conventionnel témoin, un concentré avec 20% de grignons d’olive, un autre avec 30% des raquettes de cactus, et un dernier avec 15% de grignons d’olive et 20% de raquettes de cactus. Durant les trois mois d’essai, chaque quinzaine, la production laitière était évaluée et des échantillons du lait étaient prélevés afin d’être analysés. L’introduction des grignons d’olive et des raquettes de cactus n’a eu aucun effet sur la production laitière journalière et par lactation, la composition (matière grasse, protéines, lactose, extrait sec dégraissé, matière sèche et minérale), l’énergie nette ainsi que l'acidité (pH et acidité titrable) du lait. Cependant, l'incorporation des grignons d’olive a augmenté les teneurs en acide gras C18:1n-9, en acides gras mono-insaturés (MUFA) et en n-9, mais a diminué celles en 9t-C18:1 et en acides gras polyinsaturés (PUFA). Des teneurs significativement plus élevées en C15:0, C18:1n-9 et C21:0, et des teneurs plus faibles en C4:0, 9t-C18:1, 6t-C18:2, C20:0 et PUFA ont été obtenues avec les raquettes de cactus. Le mélange des deux ressources alimentaires a réduit l’importance des teneurs en C4:0, 9t-C18:1, 6t-C18:2, C22:6n-3 et PUFA, et a augmenté celle de C18:1n-9, le rapport MUFA / PUFA et l’indice thrombogène. Les acides gras à chaînes courtes, moyenne et longue, saturée (SFA), désirable, n-3 et n-6, les rapports n-6/n-3, UFA/SFA et PUFA/SFA, (C18:0 + C18:1)/C16:0, Δ9C14, Δ9C16 et Δ9C18 dans le lait des groupes testés ont été similaires au témoin. Cette étude a permis de conclure que les grignons d’olive et les raquettes de cactus n’ont pas d’effet négatif sur la production et la qualité du lait de chèvre, par contre, ils améliorent légèrement le profil des acides gras. Pour évaluer l’effet de l’incorporation des grignons et des raquettes de cactus dans la ration des chevreaux, une étude visant l’évaluation des caractéristiques de la carcasse et la qualité de la viande des chevreaux Béni Arouss a été menée. Quarante-quatre chevreaux âgés de 3 mois ont été répartis en quatre lots et recevaient un concentré contenant, en matière sèche, soit 35% de grignons d’olive, soit 30% des raquettes de cactus, soit 15% grignons et 15% de cactus par rapport à un concentré conventionnel. Après 3 mois d’engraissement, les animaux ont été abattus et les résultats ont montré que les caractéristiques de la carcasse (poids final, rendement carcasse, poids des abats, couleur du dos et de la selle) n’ont pas été affectées par la ration, à l’exception de l’indice du muscle qui a diminué avec 35% des grignons d’olive, ainsi que l’indice du rouge et du jaune aux niveaux du contour de la queue et du ventre. Le pH ultime, la couleur, l'humidité et la tendreté de la viande n'ont pas été affectés par les régimes alimentaires. Cependant, une teneur plus élevée en protéines, en matière grasse et en cendres avec 30% de raquettes de cactus, et une teneur en protéines plus faible avec une ration à 35% de grignons d’olive et 15% de grignons et 15% de cactus ont été observées au niveau du muscle Longissimus dorsi. Une capacité de rétention d’eau élevée a été enregistrée dans le muscle Semimembraneux avec l’introduction des raquettes de cactus dans les rations. Les groupes, les rapports et les indices des acides gras des muscles étaient similaires entre les groupes d’animaux, à l'exception du profil des acides gras qui a été affecté par l'alimentation, en particulier pour le muscle Semimembraneux. Ainsi, l’incorporation des grignons d’olive et des raquettes de cactus dans la ration des chevreaux n’a eu aucun effet négatif sur la qualité de la carcasse et de la viande. Pour expliquer l’effet des grignons d’olive et des raquettes de cactus sur la qualité des produits, une étude a été menée, recherchant leur effet sur la composition de la flore bactérienne. Afin de réaliser cette étude, le jus de rumen des chevreaux de l’étude d’engraissement précédente a été prélevé lors de l’abattage pour l’extraction de l’ADN bactérien. Le jus de rumen récupéré avait une faible acidité dans le groupe témoin par rapport aux autres groupes tests. Les résultats de l’étude métagénomique ont montré que l’incorporation des grignons d’olive et des raquettes de cactus n'a eu aucun effet sur l'abondance des bactéries et leur diversité alpha (richesse, uniformité et indices Simpson et Simpson réciproque). L'absence d'effet de ces aliments a été confirmée par les résultats des tests de diversité bêta (échelles nonmétriques multidimensionnelles (nMDS), analyse de la variance moléculaire (AMOVA), homogénéité de la variance moléculaire (HOMOVA) et analyse permutative multivariée de la variance (PERMANOVA)). Ces deux ressources avaient un effet léger sur l'unité taxonomique opérationnelle (OTU) au niveau des genres, en affectant significativement trois genres bactériens. Ainsi, les grignons d’olive et les raquettes de cactus n’ont pas eu d’effet mesurable sur la composition bactérienne du jus de rumen. L’espèce caprine semble être capable de s’adapter à l’incorporation de ces deux ressources alternatives, ce qui permet de recommander leur introduction dans la ration du cheptel caprin. [less ▲]

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See detailReal-time semantics in video sequences
Cioppa, Anthony ULiege

Doctoral thesis (2020)

The study of semantics intends to provide meaning to data. In the case of video sequences, semantics allows to derive an analysis of the scene, on which many real-world applications can rely. To this ... [more ▼]

The study of semantics intends to provide meaning to data. In the case of video sequences, semantics allows to derive an analysis of the scene, on which many real-world applications can rely. To this extent, we start by defining two levels of semantics that can be extracted from videos. First, we define as low-level semantics every information describing the natural content of the video, comprising the objects and the environment of the scene. Second, high-level semantics characterizes the interpretation of the events occurring in the scene, which relates to a deeper understanding of the role of the elements composing this scene. In the first part, we explore several approaches to extract low-level semantics from video sequences in real time, as most current state-of-the-art methods are rather slow. In particular, we focus on three types of low-level semantics: motion detection, semantic segmentation and object detection. As a first contribution, we develop an asynchronous combination method to leverage the output of a slow segmentation network to improve the performances of a real-time background subtraction algorithm, while keeping real-time inference. As a second work, we present a novel method to train a fast segmentation network by leveraging the output of another slow, but performant, segmentation network while constantly adapting to the latest video conditions. Then, we show that this method, called online knowledge distillation, also proves to be effective for detecting players on a soccer field, even when the two networks process videos with different modalities and fields of view. In the second part, we focus on high-level semantics describing the events taking place during a soccer game. First, we leverage low-level semantics to progressively produce a higher-level understanding of the game and present a simple, yet effective, semantic-based decision tree to segment the following game phases: goal or goal opportunity, attack, middle and defense. In a second approach, we develop a novel network architecture coupled with a context-aware loss function to spot game events such as goals, card and substitution, and show that it achieves state-of-the-art performances on the SoccerNet dataset. As a final contribution, we publicly release a novel dataset containing high-level semantic annotations, comprising a complete set of game events and semantics related to the editing of the TV broadcast. This allows us to define four challenging tasks: action spotting, camera shot temporal segmentation, camera shot boundary detection, and replay grounding. We hope that this dataset will become the reference for high-level semantics in soccer videos. [less ▲]

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See detailLes staphylocoques d’origine animale : génétique de la résistance à la méticilline et évaluation thérapeutique des bactériophages dans le cadre des mammites bovines
Ngassam Tchamba, Cyrille ULiege

Doctoral thesis (2020)

Milk production, one of the main foodstuffs in Europe and particularly in Belgium, is often faced with problems which each have significant impacts on economies. Indeed, decreases in milk production ... [more ▼]

Milk production, one of the main foodstuffs in Europe and particularly in Belgium, is often faced with problems which each have significant impacts on economies. Indeed, decreases in milk production, penalties imposed for the high number of somatic cells in milk (> 4x105 cells / ml in tanks), the slaughter of cows with incurable mastitis, and antibiotic treatment each contribute to these economic losses (Halasa et al., 2007; Stevens et al., 2016; Ashraf and Imran, 2018). Antibiotic treatment will lead to the emergence of antimicrobial resistances such as methicillin resistance which is one of the most encountered in bovine mastitis and concerns staphylococci species (S. aureus and non-aureus) called methicillin resistant staphylococci (MRS) (Cohn and Middleton , 2010). The MRS represents a threat for public health due to their zoonotic potential and the transferability of the resistance between different staphylococcal species (Becker et al., 2018; Lakhundi and Zhang, 2018). Following these antibiotic resistance problems, farmers are increasingly exploring non-antibiotic alternatives for the treatment of bovine mastitis (Ciorba et al., 2015; Leimbach, 2017). These alternatives nowadays mainly involve the preventive or curative use of new products among which bacteriophages are some of the most promising because of their high advantages relative to antibiotics (Angelopoulou et al., 2019). In addition, recent studies have suggested the efficacy of this approach when using phages and phage endolysins against bovine mastitis both in in vitro assays and in mouse models (Zhou et al., 2017; Iwano et al., 2018; Angelopoulou et al., 2019). Building on these observations, the main objective of this thesis was to carry out an evaluation of the therapeutic use of bacteriophages as an alternative to antibiotics against bovine mastitis mediated by S. aureus. To achieve this objective, several studies have been conducted consisting of building up a collection of staphylococci from various origins (study 1), identifying and characterizing the MRS particularly responsible for bovine mastitis (study 2), and finally evaluating the therapeutic efficacy of some bacteriophages on S. aureus strains from our collection responsible for bovine mastitis (study 3). The study 1 revealed that 83% of the staphylococci strains in our collection were isolated from milk sample of cows with mastitis. Most of these samples were collected in Belgium and showed a certain presence of MRS reflecting the overuse of antibiotics in animal production. The majority of the strains responsible for bovine mastitis in this study were identified as S. aureus, although coagulase negative staphylococci (CNS) also constitute a large bacterial population, in particular among strains resistant to methicillin in Belgium. This study also reveals that the comparison of two bovine mastitis diagnostic tests results, classical bacteriology (MALDI-TOF) and qPCR (Pathoproof®), showed a concordance rate of around 67%. The two methods, each with advantages and disadvantages, were considered to be complementary for a better diagnosis. In study 2, the characterization of MRS in our collection enabled the identification of the SCCmec (staphylococcal cassette chromosome) type IV as predominantly present in cattle in Belgium. The limits of typing tests (phenotypic and genetic), the identification of potential new SCCmec as well as the need to think about establishing a new classification of cassettes within the CNS were also highlighted in this study. The study 3, has made it possible to observe the in vitro activity of phages against the strains of S. aureus tested, mediated by a bacterial lysis both in agar and broth media. Efficacy was also observed in vivo, as shown by a decrease of the bacterial titers both in Galleria (G.) mellonella larvae and murine mastitis model and a partial infection of the mice mammary glands in the groups infected and treated with phages. In conclusion, this study provides some relevant finding as well as for the diagnostic methods of bovine mastitis and the MRS involved. Our work complements the studies carried out with regard to the assessment of phage therapy in bovine mastitis by in vitro and in vivo tests. It also makes it possible to show the interest of the experimental intermediate model between in vitro and in vivo using G. mellonella larvae when assessing the phage efficacy against S. aureus strains responsible for bovine mastitis. Several perspectives are possible following this study in order to improve our results and deepen our knowledge on the subject. Among others, a modification of some parameters such as the phage / bacteria ratio and their inoculation route by additional in vivo studies could make it possible to improve the results of the phages efficacy. Others factors such as immune system as well as the presence in milk of some proteins or lipids which can influence the phages effectiveness could be also studied in order to control them during the in vivo evaluation of the phages efficacy. Finally, the successful establishing a new classification of cassettes within the CNS in the future will appear as one of the achievements of this work. [less ▲]

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See detailÉtude des interactions et des régulations au sein du noyau de synthèse du peptidoglycane septal d’E. coli
Boes, Adrien ULiege

Doctoral thesis (2020)

La division des bactéries à Gram négatif, comme Escherichia coli, est un processus coordonné spatiotemporellement et finement régulé. La division nécessite la séparation des chromosomes nouvellement ... [more ▼]

La division des bactéries à Gram négatif, comme Escherichia coli, est un processus coordonné spatiotemporellement et finement régulé. La division nécessite la séparation des chromosomes nouvellement répliqués, l’invagination des deux membranes cellulaires, la biosynthèse du peptidoglycane septal (sPG) et la séparation des deux cellules filles. Ces fonctions sont assurées par une structure macromoléculaire dynamique appelée le divisome, composé d’environ 30 protéines distinctes, dont 12 essentielles, pour la division et le maintien de l’intégrité cellulaire. Cette thèse s’est focalisée sur la synthèse du sPG et en particulier sur les protéines FtsW, PBP3, PBP1b, FtsBLQ et FtsN du divisome d’E. coli. Le complexe FtsW-PBP3 et la protéine PBP1b participent à la biosynthèse du sPG alors que les protéines FtsBLQ et FtsN semblent participer à la régulation de cette synthèse. Au cours de ce travail, nous avons contribué à une meilleure connaissance du réseau d’interactions qui s’établit entre ces protéines. Par ailleurs, nous avons établi une nouvelle description de la régulation de la biosynthèse du sPG PBP1b-dépendante et en particulier, nous avons mis en évidence le rôle de FtsBLQ dans la régulation de la synthèse du sPG. Ce complexe inhibe l’activité GTase du PBP1b, probablement via FtsL, et inhibe l’activité transpeptidase de PBP3, via FtsQ. La protéine FtsN, quant à elle, lève l’inhibition sur l’activité glycosyltransférase du PBP1b, déclenchant la biosynthèse du sPG PBP1b-dépendante. En particulier, nous avons montré l’interaction spécifique entre la région essentielle de FtsN (E FtsN) et la région du PBP1b située entre ses domaines UB2H et glycosyltransférase. Cette région est importante pour la stimulation de l’activité glycosyltransférase du PBP1b et des données in vivo confirment l’importance de l’interaction E FtsN-PBP1b pour la fonctionnalité du PBP1b. Enfin, nous avons développé un test spécifique, en anisotropie de fluorescence, pour la mise en évidence de l’interaction d’un dérivé fluorescent du Lipide II avec les protéines PBP1b, FtsW, FtsW-PBP3 et MurJ. Nous avons démontré l’applicabilité de ce test en vue de criblage à haut débit de molécules interférant dans la liaison Lipide II-protéines et/ou liant directement le Lipide II. En outre, ce test a permis de mettre en évidence le mécanisme d’inhibition de l’activité GTase du PBP1b par la squalamine et d’autres aminostéroles caractérisées préalablement. En effet, ces molécules semblent se lier au PBP1b empêchant la liaison du Lipide II. [less ▲]

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See detailAt home 'outside': Young migrants aligning their ‘home orbits’ in the city of Brussels
Damery, Shannon ULiege

Doctoral thesis (2020)

Young people are the group on which society bestows its hopes and fears for the future. Under intense scrutiny, the weight of these hopes and fears rests heavily on young migrants in Europe who are ... [more ▼]

Young people are the group on which society bestows its hopes and fears for the future. Under intense scrutiny, the weight of these hopes and fears rests heavily on young migrants in Europe who are watched for signs of non-integration, criminality and radicalization, . Paradoxically, in spite of this scrutiny, their positive contributions to society and the creative ways they direct their own adjustment to a new society are often overlooked. This ethnographic research aimed to explore these contributions and adjustments through the lens of ‘home’, where home is understood as an evolving process of the imagination that combines one’s relationships with one’s self, society, and the material world. In contrast to the concept of integration, home places the individual and their emotions at the center of the analysis and illuminates how various forces influence the home-making process. Comparing young migrants with different official migratory statuses offered insights into how outside forces impacted home-making while also showing how young migrants were able to subvert various obstacles and find creative ways to make home in the city of the Brussels. Through participant observation that explored home-making through public space, the arts, and language, the findings in this thesis reinforce the argument that mundane everyday routines are important foci of social science research. In this thesis, these routines of daily life were central to understanding the home-making of young migrants. Investigating the different dimensions that contribute to home, and the various factors such as societal norms, laws and policies, and individual agency that can impact it, led to a conceptualization of the ‘home orbit’. Home is depicted in this work as being at the center of an orbit, with different dimensions of home-making in constant motion around it and subject to various forces. This conceptual map and analytic tool illuminated how the superdiverse context of Brussels made fertile ground for both spaces of exclusion and the ability to find belonging by ‘not belonging’. Opening the data collection to include people of numerous national backgrounds and ethnic backgrounds as well as different migratory statuses allowed for findings that highlighted what young migrants have in common in their home making, as well as the strength of influence of various obstacles in this endeavor. [less ▲]

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See detailSteady Transonic Aerodynamic and Aeroelastic Modeling for Preliminary Aircraft Design
Crovato, Adrien ULiege

Doctoral thesis (2020)

Modern aircraft usually have light and flexible wings with large aspect ratio, which are subjected to significant deformations. The aeroelastic behavior of such wings is of paramount importance as it ... [more ▼]

Modern aircraft usually have light and flexible wings with large aspect ratio, which are subjected to significant deformations. The aeroelastic behavior of such wings is of paramount importance as it affects both the structural design and the aircraft performance. The present thesis aims at assessing the impact of aerodynamic modeling on transonic aerodynamic and aeroelastic computations performed in the preliminary stage of the aircraft design process, and at developing an aerodynamic modeling tool performing such computations with low computational cost. First, the different levels of fidelity commonly used for aerodynamic modeling in aircraft design are investigated. The aerodynamic loads predicted by the different models and the computational cost of the solutions are compared using two rigid wings simulated in transonic flight conditions. The results show that linear modeling is not suitable for transonic flow calculations as it cannot capture shocks, and that higher-fidelity models are too computationally expensive to be used routinely in the preliminary design stage. On the other hand, nonlinear potential solutions offer an excellent trade-off between accuracy and computational cost. Accordingly, the main full potential formulations and their solution techniques are subsequently reviewed. Two specific methods for solving the full potential equation are then developed and implemented. The first is the field panel method, an extension to the widely used and computationally effective panel method. Numerical calculations show that the iterative field panel approach implemented during this work yields satisfactory results for subcritical flows, but smears shock waves and thus cannot model transonic flows accurately. Moreover, the computational cost of the method is prohibitive for such computations. The second method is based on a continuous Galerkin, unstructured, finite element formulation. The code developed in the context of this work, Flow, is compared to a commercial state-of-the-art solver, Tranair, using various two and three-dimensional cases. In practice, Flow’s accuracy and computational cost are similar to Tranair, but the code open-source. The modular design of Flow allows the code to be easily coupled with CUPyDO, an in-house fluid-structure interaction code, which is then used to perform static transonic aeroelastic computations. In this context, the different aerodynamic levels of fidelity are compared using a flexible benchmark wing. For the wing shape considered in the present work, the results illustrate that linear potential methods yield sufficiently reliable static deformations, provided they model wing camber. On the other hand, nonlinear methods yield more accurate aerodynamic predictions but their computational cost is significantly higher. Consequently, static aeroelastic computations could be efficiently performed following a multi-fidelity approach, whereby a linear model would first be used to obtain the deformed wing shape, and a nonlinear model would then be used to compute the aerodynamic loads on that deformed wing shape. [less ▲]

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See detailReduced-order modelling of active distribution networks for large-disturbance simulations
Chaspierre, Gilles ULiege

Doctoral thesis (2020)

Distribution systems are getting more and more complex owing to the increasing number of Inverter-Based Generators (IBGs) connected at Medium-Voltage (MV) level. This makes distribution networks more and ... [more ▼]

Distribution systems are getting more and more complex owing to the increasing number of Inverter-Based Generators (IBGs) connected at Medium-Voltage (MV) level. This makes distribution networks more and more responsive and their influence on the whole power system dynamics increases. Therefore, it becomes important for Transmission System Operators (TSOs) to model those Active Distribution Networks (ADNs) in their dynamic studies. First, this thesis deals with the derivation of reduced-order, “grey-box” models of ADNs, intended for dynamic simulations of the transmission system. The ADNs are assumed to host IBGs as well as static and motor loads, whose dynamic parameters are affected by uncertainty. This latter issue is addressed using Monte-Carlo simulations. The parameters of the equivalents are adjusted to match as closely as possible the average of the randomized responses, while their dispersion is accounted for through the weights of the weighted least-square minimization. A procedure is used to remove from the identification the parameters with negligible impact. To avoid over-fitting, the equivalents are tuned for multiple large-disturbance simulations. A recursive procedure is used to select the smallest possible subset of disturbances involved in the least-square minimization. Next, the methodology is extended to account for changing operating conditions. This consists of testing the accuracy of a set of previously derived equivalents, and updating the best of them if its accuracy is not satisfactory. In order to update the equivalent with minimal effort, an approach minimizes the number of parameters to update. In most cases, the results coincide with expectations coming from “engineering judgment”, involving the adjustment of a (very) small subset of parameters. Finally, a new application for a Battery Energy Storage System (BESS), connected at distribution level, is proposed. Its active and reactive powers are controlled such that the net power entering the distribution network matches the response of the available equivalent to large disturbances in the transmission system. The response of the equivalent is simulated in real time. This would allow using with a higher guarantee of accuracy the equivalent model in dynamic simulations of the transmission system. The BESS is supposed to be connected at the main substation of the distribution grid and its control does not use any model of that grid. All simulations reported in the thesis have been carried out on three ADN test systems with different characteristics, one of them being derived from an existing distribution grid. The tests involve large disturbance scenarios that trigger nonlinear, discontinuous responses of IBGs and loads. [less ▲]

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See detailEtude du métabolisme, à l'échelle de l'écosystème, de l'herbier de Posidonia oceanica (L.) Delille en Baie de Calvi
Champenois, Willy ULiege

Doctoral thesis (2020)

Human population is increasing exponentially with a growing occupation of the coastal zone. It is estimated that by 2050, about 70% of the world population will live and/or work within 100 km of ... [more ▼]

Human population is increasing exponentially with a growing occupation of the coastal zone. It is estimated that by 2050, about 70% of the world population will live and/or work within 100 km of coastlines. This trend has been going on for decades and will further impact coastal ecosystems. Furthermore, climate changes will heavily impact littoral zones and their biotopes (sea-level increase, change of wind regime, seawater temperature increase, …). But the littoral zone is the source of about 40% of the ecosystem goods and services provided by global ecosystems to humankind. It is then important to study the different coastal ecosystems in terms of biogeochemistry to monitor their evolution. Understand the interdependence between these processes and the response of coastal ecosystems to environmental and human stressors will allow to better manage and protect them. In this context and objective, we monitored metabolic fluxes at community scale in a Posidonia oceanica meadow in the Bay of Calvi (Corsica, France) at -10 m depth. This monitoring contributes to the study of the biology and ecology of the posidonia meadow since the 1970s at this site by ULiège from STARESO. This high-frequency monitoring over 12 years (2006-2018) was carried out with a permanent mooring equipped with oxymeters. This allowed us to compute by a mass balance of O2 the gross primary production (GPP), community respiration (CR) and net community production (NCP) over 3275 24h-cycles. GPP, CR and NCP were highly variable whatever the time scale (daily, seasonal, year-to-year). Day-to-day and seasonal variability of metabolic fluxes follows the one of solar irradiance. Solar irradiance, water temperature and chlorophyll a were the main variables responsible for the inter-annual variations of metabolic fluxes. We also observed the response of the meadow to extreme weather conditions that nowadays are extreme events (heat-wave, absence of fall-winter storms, …) that could become the normal situation in future with climate change in the around Mediterranean Sea. Nowadays, GPP peaks in late Spring / early Summer (May-July), when day length is maximal and seawater temperature optimal (17°C to 20°C), the seawater temperature peaking seasonally (~24°C) in late August. This favorable conjunction of light and temperature for posidonia will not be maintained with a 3°C increase of seawater temperature projected for 2100. Climate models predict that storms in autumn and winter will decrease during the next decades. Data collected during years characterizes by absence of fall storms and/or of mild winters with low winds showed a decrease of both GPP and CR. We showed that this decrease was probably related to the absence of the export of litter, which shadows the benthos, blocking the development of sciaphyle flora. Further, a large part of nutrients stored by P. oceanica are absorbed by leaves from the water column. Mild and calm winters favor an early stratification of the water column, re-enforcing its oligotrophic nature. The mooring of oxymeters was an efficient and robust tool to carry out the monitoring of the P. oceanica meadow. We made incubations with benthic chambers during the first three years of the monitoring allowing to make the full budget of inorganic and organic carbon. The P. oceanica meadow is largely autotrophic at annual and community scales as GPP is higher thatn -CR (NCP>0) with 83, -60 and 23 mol de C m-2 yr-1 for GPP, CR and NCP, respectively. NCP was positive for 90% of the 3275 daily cycles. The incubations showed that a dissolution of calcium carbonate occurred in the meadow, at a rate of 7 mol Ca CO3 m-2 yr-1. For seawater pH and total alkalinity standard conditions, this corresponds to an additional sink of 4 mol O2 m-2 yr-1 to be added to 23 moles de CO2 m-2 yr-1 sustained by NCP. The P. oceanica meadow at -10 m in the Bay of Calvi is a net sink of CO2 of 27 moles de CO2 m- 2 yr-1. [less ▲]

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See detailDiversity, paleobiology and ecology of Organic-walled Microfossils from the Proterozoic of Arctic Canada, and implications for early eukaryotic evolution.
Loron, Corentin ULiege

Doctoral thesis (2020)

Understanding the appearance and evolution of Life on our Planet (and elsewhere?) requires multidisciplinary approaches intersecting, notably, biology, geology, chemistry and astronomy. Studies of Earth ... [more ▼]

Understanding the appearance and evolution of Life on our Planet (and elsewhere?) requires multidisciplinary approaches intersecting, notably, biology, geology, chemistry and astronomy. Studies of Earth deep times provide insights on the early hydrosphere, atmosphere and geosphere which influenced the development of the early biosphere. Conversely, the transition from prebiotic chemistry to life and subsequent biological changes (prokaryotic then eukaryotic photosynthesis, rise of eukaryotes, appearance of crown-groups, …) also played a role in modifying our young planet. This study focuses on a fundamental period for the diversification of Life on earth, the Proterozoic, that span from 2500 to 541 Ma. The total diversity of organic-walled microfossils present in two unmetamorphosed sedimentary successions from the northwestern Canada was investigated: The Dismal Lakes Group and the lower Shaler Supergroup. These successions represent more than 700 million years of earth history (from 1600 to 900 Ma) and preserve beautiful and abundant microfossils, especially numerous taxa of eukaryotes. This thesis demonstrates that the major diversification of eukaryotes observed in the fossil record at ~800 Ma has, in fact, started earlier and was more gradual. Eukaryotes were diversified by the early Mesoproterozoic and crown groups might have already appeared by then. New and earlier evidence for eukaryovory permits to suggest that predation was probably a powerful driver of this diversity rise. By combining classical paleontological approaches with spectroscopic and ultrastructural analyses, a new candidate of crown-group eukaryote, Ourasphaira giraldae could be proposed. This microfossil, recognized as an early fungus, provides new insights into crown-group diversification in the Proterozoic but also a new calibration point for molecular clock estimates of early eukaryotic evolution, and in particular of the Opisthokontes. Collectively, these studies show that northwestern Canada is an exceptional window on early eukaryotes evolution. [less ▲]

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See detailApports de la géomorphologie dans les processus de conception, de suivi et d’évaluation de projets de restauration de cours d’eau à différentes échelles spatiales et temporelles
Peeters, Alexandre ULiege

Doctoral thesis (2020)

In light of the increasing degradation of aquatic ecosystems and driven by growing environmental awareness, the issue of restoring rivers has gradually emerged since the 1980s. Initially the prerogative ... [more ▼]

In light of the increasing degradation of aquatic ecosystems and driven by growing environmental awareness, the issue of restoring rivers has gradually emerged since the 1980s. Initially the prerogative of engineers and ecologists, river restoration has gradually opened up to geomorphologists. Because of its holistic approach, geomorphology has thus become an essential discipline in river restoration. Indeed, it allows the site to be considered at several spatial scales (from catchment to form) and at several time scales (from slow geomorphological processes to human intervention). In addition, it has a field of research that explores many issues related to river management because geomorphological processes determine the physical framework of the river system in which ecological processes take place and aquatic organisms live. Moreover, geomorphology has finally proved to be a discipline essential to river restoration because it provides multiple tools and methods. However, although the contributions of geomorphology seem undeniable in the eyes of geomorphologists, they lack visibility among other actors involved in river restoration. Highlighting these contributions requires first identifying the tools and methods provided by geomorphology and then placing them within restoration planning schemes. In this context, the main objective of this thesis is to highlight the contributions of geomorphological tools and methods in the design, monitoring and evaluation processes of river restoration projects. To establish the role played by geomorphology within these processes, this work relies on the study of three components: "ecological continuity", "stream channel habitats" and "streambank", each components being the subject of a specific study in the form of a publication. First, "ecological continuity" is considered in this work from the perspective of the longitudinal component of sediment connectivity. This issue is addressed through the multiscale analysis of the impact of weir on sediment connectivity. Conducted in the River Bocq catchment, this study is based on the in-depth analysis of 7 weirs using different approaches: (i) calculating and analysing changes in the volume of sediment trapped in reservoirs, (ii) analysing grain size of bed material upstream, downstream and within the reservoirs, and (iii) measuring sediment transport with tracers (slag particles and PIT-tagged pebbles) to assess bedload transport across reservoirs and weirs. The results indicate that the volume estimates of bedload stored in reservoirs represents between 25 and 50% filled compared to the reservoir volume capacity, and did not evolve very much since 1990. In addition, bedload continues to be transported out of the reservoir, even though the selective trapping of coarser elements was observed within the reservoir. This trapping effect is mitigated when the weir has open or collapsed flushing gates that facilitate bedload transfer. This indicates that weirs act as leaky barriers that allow bedload to pass through, although the individual geomorphic setting plays a primary role in determining the local sediment continuity. These findings suggest that river connectivity is less impacted than initially thought and is likely to increase over time as old weirs gradually fall into disrepair. Second, "stream channel habitats" are studied through the evaluation of the suitability and sustainability of artificial spawning gravel habitats for lithophilic fish species. The restoration of spawning substrate by gravel placement is commonly seen as one of the most important mitigation measures to stem local wild fish population declines. However, while the biological requirements of lithophilic spawning fishes are generally taken into account, few considerations are given to river processes (e.g., bedload transport and clogging). In this study, we examined the effects of such rehabilitation actions on six degraded river reaches in Wallonia, thanks to (i) the monitoring of the thickness and clogging of the spawning gravel and (ii) to the PIT-tagged tracking of gravel dispersion over a period of 3.6 to 8.5 yrs. The results highlighted that several artificial spawning grounds were quickly clogged because of improper sizing of the spawning material. Gravel that was too coarse to be mobilized by the river and that had a narrow grain size range favoured fine sediment accumulation within the interstices of the gravel layer. On the other hand, one spawning gravel placement was rapidly scoured (after 2.2 yrs) because of an undersizing of the gravel with respect to flow competence. In the end, one gravel placement presented adequate gravel sizing, allowing periodic gravel transport over short distances (the mean annual travel distance was ~3 m). The longevity of a gravel placement and the ability of the displaced gravel to form new spawning grounds downstream were strongly dependent on the distance that the placed gravel was likely to travel, which in turn depended on unit stream power, channel morphology and bed texture. Thirdly, for the "streambank" component, we focused on streambank stabilisation techniques using soil bioengineering. This topic is addressed both from a scientific perspective (evaluation of the effectiveness and resistance of 4 streambank stabilisation techniques) and from an operational perspective (guidelines for implementing these techniques). In addition to the field expertise conducted on 19 streambank stabilisation structures, this study relies on an in-depth hydrological analysis and on an extensive use of historical data. The assessment of the resistance of streambank stabilisation structures, expressed in terms of the unit stream power, indicates that the permissible unit stream power thresholds (i.e., the maximum value of unit stream power to which the protection can resist) is approximately of 130 W/m² for fascines, 65 W/m² for tree revetment, 200 W/m² for cribwall and 150 W/m² for groynes system. Nevertheless, several factors might undermine the bank stabilisation structure, resulting to a lower threshold of unit stream power. The deterioration factors highlighted are (i) a poor vegetation recovery (lack of sunlight, unmanaged cutting, and damage caused by animals such as livestock and rodents), (ii) an inadequate design or filling, and (iii) a lack of consideration of fluvial processes such as unit stream power and Total Suspended Solids. Through the study of these 3 components, this thesis has demonstrated the essential role that geomorphology plays in the design, monitoring and evaluation processes of river restoration projects. The value of geomorphological tools and methods has been highlighted for the different stages of river restoration schemes, from the assessment of the geomorphological setting to the post-project appraisals. In the end, this research has highlighted the importance of in-depth geomorphological studies because they help to improve our knowledge of hydrosystems, and more specifically of river restoration. This knowledge will notably benefit future studies on river restoration. [less ▲]

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See detailNew ways of working, new ways of living...What housing and planning implications? Ontologies and governance of live-work mix. A comparison of Amsterdam, Brussels and Stockholm
Uyttebrouck, Constance ULiege

Doctoral thesis (2020)

The ‘flexibilisation’ of labour markets has led to the blurring of the work and home spheres, which has had implications on housing and planning. This thesis addresses the ‘live-work mix’, that is, the ... [more ▼]

The ‘flexibilisation’ of labour markets has led to the blurring of the work and home spheres, which has had implications on housing and planning. This thesis addresses the ‘live-work mix’, that is, the renewed intertwining of living and working activities in new housing production and urban development. This phenomenon is related to the focus on new target groups, the restructuring of housing provision and changes in urban agendas. The research addresses three overarching questions: (i) what are the different ontologies of live-work mix in contrasting institutional frameworks, (ii) what kind of governance arrangements are used to implement live-work mix and (iii) how do institutional frameworks influence the nature and governance of live-work mix. An embedded, comparative case-study analysis was conducted to tackle these questions, with three cities as main cases (Amsterdam, Brussels and Stockholm) and a typology of live-work mix as embedded cases. The analytical framework draws on path dependency and an institutionalist approach to collaborative governance. The first part of the thesis compares the housing and planning regimes as well as live-work mix strategies of the case-study cities. The analysis confirms the impact of early planning directions and shows how factors, such as historically dominant actors, impact local ontologies of live-work mix. Nevertheless, current issues conditioning live-work mix, such as the flexibilisation of tenure, apply across contexts. The second part explores the governance of live-work mix. The results indicate that local governments’ intervention is essential in live-work development, whereas market parties remain focused on residential development. Live-work mix also requires new instruments and strategic uses of existing tools. Although the actors share interests to enhance the attractiveness of a specific location for target demographics, divergent views, for instance, about the nature of live-work mix can affect their collaboration. As a result, the projects delivered are likely to favour housing, and affordability and accessibility issues can arise. A comprehensive discussion reconnects the empirical findings to the conceptual framework. It confirms that live-work mix is purposed for specific groups and draws on the emergence of new (commodified) housing forms in locations prioritised in urban agendas. Although institutional frameworks affect several variables of live-work mix, the implementation of live-work goals is not always more effective in more regulated frameworks. The discussion closes with suggestions for the regulation and governance of live-work mix that will inform planners and decision-makers on a phenomenon that is likely to expand in the future. [less ▲]

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See detailGypsum residues in fine recycled aggregates: effects on mechanical and microstructural properties of cementitious composites
Colman, Charlotte ULiege

Doctoral thesis (2020)

Fine recycled aggregates are an important waste stream coming from the demolition of old concrete structures. They are up to now not valorized because of an increased water absorption, lower density and ... [more ▼]

Fine recycled aggregates are an important waste stream coming from the demolition of old concrete structures. They are up to now not valorized because of an increased water absorption, lower density and higher fines content compared to natural aggregates. Moreover, they often have a high sulfate concentration. These sulfates could have originated from plaster in a demolished building, or from the residual cement that is commonly present in these materials. The sulfate level of recycled aggregates is recommended to stay under 0.2 mass% by standard EN206, to limit the risk on sulfate attack: the reaction between cement components, water and sulfates results in the formation of expansive minerals such as ettringite. This expansion can eventually lead to cracking of the material and a general loss in mechanical performances. Fine recycled aggregates from recycling plants did contain 0.15 to 0.80 % of sulfates which is more than allowed, but these amounts did not cause any swelling or degradation when the aggregates were incorporated into mortars. A very elevated sulfate content of 3 % was needed to observe significant expansion, and even this level of contamination could be mitigated by increasing the alkalinity of a mix. Concretes made with varying sulfate levels either expanded or they didn’t: the absolute swelling amount was not proportional to its sulfate content. The actual threshold concentration that started the swelling reaction was dependant on the type of coarse aggregate. The results of this study provide recommendations for the use of fine recycled aggregates contaminated with gypsum residues: a sulfate content of at least 0.3 % could be possible, and even more if certain parameters and mix compositions can be adjusted accordingly. The current limit of 0.2 % seems too strict and hinders the valorization of fine recycled aggregates in high quality construction applications. [less ▲]

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See detailAnalyse de l’ossification endochondrale dans le cadre de souris déficientes en 5-phosphatase SHIP2, un modèle potentiel pour l’opsismodysplasie humaine ?
Vande Catsyne, Charles-Andrew ULiege

Doctoral thesis (2020)

Opsismodysplasia is a rare recessive skeletal automosal chondrodysplasia characterized by dwarfism including shortened limbs, smaller hands and feet, macrocephaly and facial dysmorphism. The fate is ... [more ▼]

Opsismodysplasia is a rare recessive skeletal automosal chondrodysplasia characterized by dwarfism including shortened limbs, smaller hands and feet, macrocephaly and facial dysmorphism. The fate is variable, ranging from perinatal mortality to allow some individuals to exceed twenty. The radiographic abnormalities include shortened long bones with severely delayed epiphyseal mineralization, metaphyseal malformations, shortened metacarpals and phalanges, severe platyspondyly and a narrow chest. Histological studies performed on bones of opsismodysplastic patients are few but have nevertheless been able to highlight specific alterations in the growth plate. In the resting zone, germinal chondrocytes are more numerous and appear disorganized. Within the proliferative zone, there is nearly absence of columnar organization of proliferative chondrocytes. The hypertrophic area is reduced in size and has a significantly reduced number of hypertrophic cells. Finally, the bone trabeculae are described as thickened, shortened and irregular. These alterations were observed in all patients studied, but with great variability in intensity. In 2013, a group of researchers discovered that almost 60% of opsismodysplastic patients present homozygous or heterozygous mutations in the INPPL1 gene coding for the protein SHIP2. More than 25 different mutations have been identified in opsismodysplastic patients including nonsense, in-frame, missence, frame-shift and splice site mutations. Although most of them are predicted to severely alter or even completely inactivate the catalytic function of SHIP2, the underlying mechanism is currently unknown. In order to investigate the function of SHIP2 in endochondral ossification, we used in our study a SHIP2Δ/Δ mouse expressing a reduced level of catalytically inactive SHIP2 protein and an inhibitor of the protein 5-phosphatase activity. First, as seen in opsismodysplastic patients, catalytic inactivation of SHIP2 in mice induces a reduction in body size and in long bones, a craniofacial dysmorphism, reduction of the size of the hypertrophic zone and abnormalities of the mineralization of the growth plate. Second, the presence of the protein SHIP2 Δ is sufficient to induce in vitro intrinsic bone alterations of opsismodysplasia. Third, the expression of osteocalcin is increased when SHIP2 is inactivated in primary chondrocytes in culture and concomitantly with the decrease in the formation of mineralized nodules. Targeting osteocalcin mRNA with a specific shRNA increases the production of mineralized nodules. Fourth, phosphorylation levels of MEK and ERK1/2 are significantly increased when the catalytic activity of SHIP2 is inactivated in primary chondrocytes treated with serum and IGF1, but not with FGF2, compared to controls. Treatment of chondrocytes and metatarsals with an inhibitor of MEK phosphorylation partially restores the formation of mineralized nodules, the size of the hypertrophic zone and bone growth, allowing one day a potential treatment. Together, these results indicate that SHIP2Δ/Δ mice represent a relevant model for opsismodysplasia and that the majority of these abnormalities could be explained by dysregulation of the MAPK/ERK pathway. They underline the role of SHIP2 in chondrocytes differentiation during endochondral ossification, as an inhibitor of the MAPK/ERK pathway. Finally, this thesis opens up interesting work perspectives in therapeutic research in the context of human opsismodysplasia. [less ▲]

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See detailPERPECTIVE DE DEVELOPPEMENT DE LA LOMBRICULTURE A EUDRILUS EUGENIAE POUR L’ALIMENTATION DES VOLAILLES AU GABON
Byambas, Patrick ULiege

Doctoral thesis (2020)

Afin de fournir des pistes pour l’amélioration de l’alimentation des poulets, l’incorporation d’une ressource alimentaire non conventionnelle disponible au Gabon, à savoir les lombrics, est envisagée. La ... [more ▼]

Afin de fournir des pistes pour l’amélioration de l’alimentation des poulets, l’incorporation d’une ressource alimentaire non conventionnelle disponible au Gabon, à savoir les lombrics, est envisagée. La première partie de l’étude consiste en une présentation du ver de terre Eudrilus eugeniae Kinberg, à travers une revue des connaissances sur cette ressource alimentaire non-conventionnelle qui est un aliment naturel des volailles en général, et du poulet de chair en particulier. Cette synthèse bibliographique présente les différentes caractéristiques d’E. eugeniae et les rôles qu’il peut jouer dans l’amélioration de la valeur nutritive de l’aliment du poulet. Elle aborde aussi, les conditions de sa valorisation agronomique à travers la lombriculture. Bien que le ver de terre soit une source de protéine pour les poulets, sa collecte dans des milieux non contrôlés peut présenter des risques biologiques et non-biologiques pour les animaux. Le ver de terre peut accumuler des substances toxiques présentes dans son milieu de vie. Les métaux lourds sont fréquemment retrouvés dans les vers de terre qui en sont d’importants bio-accumulateurs et bio-indicateurs de leur présence dans le sol. Des pesticides liés au développement de l’agriculture intensive et des toxines microbiennes du tube digestif du ver de terre peuvent aussi être présents. Tous ces facteurs sont potentiellement à l’origine d’intoxication ou d’intoxination des volailles par le biais de l’alimentation. Pour limiter les risques de contamination de la chaine alimentaire, l’utilisation de la vermiculture pour la production des vers de terre est recommandée. La lombriculture à E. eugeniae, a permis de préciser ses conditions d’élevage en zone équatoriale. Les performances de reproduction et de croissance du lombric ont été mesurées à partir de 2 sources d’azote (bouse de vache et fumier de poules pondeuses) et 2 sources de carbone (fibres de noix de coco et folioles de Leucaena leucocephala). Les meilleures performances d’évolution de la population et de croissance pondérale d’E. eugeniae ont été obtenues avec la bouse de vache et les fibres de noix de coco. Les résultats suggèrent que l’association bouse de vache-fibre de noix de coco est plus adaptée pour la production d’E. eugeniae, en zone équatoriale. La production d’E. eugeniae pour l’alimentation animale a nécessité l’étude de sa valeur nutritive pour une meilleure utilisation dans les formulations. En plus des macronutriments, le profil d’acides gras du lombric a été étudié. Des acides gras à (très) longue chaîne tel que ω3 et ω 6 sont présents dans ce ver de terre. Ils sont vraisemblablement le résultat d’une biosynthèse et non pas exclusivement liés à l’aliment reçu. L’étude du profil en acides gras d’E. eugeniae a permis de mettre en évidence une capacité à bio-synthétiser les acides gras essentiels et démontre l’intérêt d’E. eugeniae comme ingrédient de substitution dans l’alimentation des volailles. Enfin le lombric a été introduit dans l’alimentation du poulet et les effets sur les performances zootechniques et économiques ont été mesurés. Les résultats montrent que la croissance des poulets et leur gain moyen quotidien ne sont pas influencés significativement par l’introduction des vers de terre. La consommation d’aliment a été plus économique avec la formulation contenant E. eugeniae. Aussi, comme le dispositif de lombriculture est relativement peu coûteux, E. eugeniae peut être un bon complément nutritif pour l’alimentation des poulets et peut générer des ressources financières relativement intéressantes pour l’éleveur. Pour conclure, cette thèse est une contribution à la connaissance d’E. eugeniae et aux perspectives de sa valorisation pour l’alimentation animale. Elle a permis de montrer que cette espèce est une source de protéines et d’acides gras, qui peut être produite à moindre coût au Gabon. [less ▲]

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See detailAutofabuladores fabulosos. Estudios sobre las autoficciones no miméticas de Mario Bellatin, Alan Pauls, Valeria Luiselli y César Aira
Licata, Nicolas ULiege

Doctoral thesis (2020)

The title of this dissertation, which holds a descriptive value of its content, is a good starting point for its summary. The word “autofabulator” refers to the author of an “autofabulation”, a technical ... [more ▼]

The title of this dissertation, which holds a descriptive value of its content, is a good starting point for its summary. The word “autofabulator” refers to the author of an “autofabulation”, a technical term that in turn refers to an obviously imaginary type of narrative that a writer builds around his or her own person, playing in it a more or less leading role. “Autofabulators” is reinforced by the adjective “fabulous”, which should be understood in the sense of “unreal”, “extraordinary”, “implausible”, because the authors considered here are not moderate fabulators. On the contrary, the plots they imagine are resolutely fictitious, and their narratives bring out this fictitious nature in many ways. In the subtitle, the expression “non-mimetic autofictions” is used as a synonym for the word “autofabulation”, and I speak of “studies” in the plural (and not of “a study” in the singular) because each chapter focuses on only one of the four authors cited, giving the priority to the unicity of his or her work. That being said, the fact that each chapter offers a reading of an individual work does not preclude that it also builds bridges with the three other authors’ work, in order to elucidate one or various important aspects of autofabulation and/or autofiction in general. It is therefore recommended to read these chapters conjointly. From the subtitle, it can be deduced that this doctoral thesis does not aim at providing a panoramic study of autofabulation, one that would be based on a large number of its cultivators. This does not however mean that I have completely lost sight in my methodology of the variety that characterises the panorama. Instead of opting for a panoramic thesis, that would encompass a wide range of authors, I opted for integrating the panorama in my approach to the narratives: not a panoramic point of view, but a panorama of analytical points of view. Indeed, remaining always primarily literary, my approach to Mario Bellatin’s (Mexico City 1960), Alan Pauls’ (Buenos Aires 1959), Valeria Luiselli’s (Mexico City 1983) and César Aira’s (Coronel Pringles, province of Buenos Aires 1949) autofabulations renews itself from chapter to chapter, and often even from subchapter to subchapter. In the pages of this thesis, the following issues among others are dealt with: the critical relationship of autofiction with medicine and more globally with sciences, feminine autofiction, the similitudes between contemporary Hispano-American autofabulation and the French nouvelle autobiographie, the rhizomatic conception of identity developed in autofabulation, the social image that autofabulators create of themselves, the ludic reading pact they propose to their readers, as well as the openness of their narratives as defined by Umberto Eco. [less ▲]

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See detailÉtude des liens Procédés-Microstructures-Propriétés pour les Alliages hors équilibre (Aciers à outils et Ti6Al4V)
Tchuindjang, Jérôme Tchoufack ULiege

Doctoral thesis (2020)

The work presented in PhD thesis is the result of a multidisciplinary approach, studying metallurgical phenomena such as solidification or transformations in solid phases under non-equilibrium conditions ... [more ▼]

The work presented in PhD thesis is the result of a multidisciplinary approach, studying metallurgical phenomena such as solidification or transformations in solid phases under non-equilibrium conditions. The purpose of the study is twofold and divided into two parts A and B. In Part A, the work aims to understand the microstructures in order to establish a link with the behavior of alloys belonging to complex Fe-Cr-CX system that undergo severe stresses on the one hand. In Part B, the work helps to determine the nature and the evolution of phases in a Ti6Al4V alloy that produced by additive manufacturing. Within Part A, both the solidification and subsequent solid phase transformations help enhancing the supersaturation effect which later influences the damage mechanisms. Studied materials are made of tool steels and high alloyed cast irons, which come from two manufacturing processes. The first one is a conventional casting in an electric arc furnace (EAF), followed by secondary metallurgy under Electro Slag remelting (ESR) prior to forging. The second one is vertical spin casting. Almost all the phases that exist within the Fe-C system are considered, starting from the high temperature  ferrite up to pearlite, which are often formed under equilibrium conditions, including non-equilibrium hardened phases such as bainite and martensite that are obtained after specific heat treatments. The characterization of theses phases is achieved while using different techniques and tools such as light microscope, scanning electron microscope associated with EDS, EBDS, dilatometry, differential thermal analysis (DTA), hardness, etc. In addition, special attention is paid to troostite that has been little studied to date, and which is often considered as a fine pearlite. Alike troostite that originated from supersaturation, several phenomena including carbides precipitating in the solid state are also considered. Mechanical properties of materials are also studied, especially after elaborating optimized heat treatments that help achieving structural homogeneity and adequate hardness. Part B is devoted to solidification and solid phase transformations in a Ti6Al4V alloy produced by Directed Energy Deposition (DED). The description of the manufacturing device and the macroscopic characterization of DED deposits obtained from different building strategies are achieved. A rough metallurgical model is set that accounts for the whole deposition process, the sketch being ascribed to a single equivalent cooling stage. Adding a 3D thermal finite element model that is validated makes it possible to simulate the evolution of the temperature at any point of the deposit. This information is used to interpret the evolution of the microstructure via a pseudo-isothermal annealing followed by final cooling stage, while considering a homogeneous sample. Using the same approach on a heterogeneous deposit allows for more complex thermal histories, thus justifying the development of a new concept, the so-called Time- phase Transformation – Block hereafter referred to as TTB concept. This approach allows the entire thermal history to be broken down into sequences, each sequence being linked to well-identified phase transformation mechanisms. In addition, the TTB concept offers a description that takes into account all stages of additive manufacturing, including rapid changes in temperature either during heating or cooling stages. The PhD thesis is the synthesis of 8 articles, of which 5 made Part A and 3 Part B. Each of the articles gives rise to a chapter where the framework of the study is recalled while bringing complementary and unpublished results. As such the overall content of a chapter helps better understanding of the topic. This study carried out on two distinct families of alloys shows that the non-equilibrium domain still remains a large field of investigation. This is particularly the case of supersaturation that leads to the formation of metastable phases. The supersaturated phases which already exist with conventional processes will be even more numerous if additive manufacturing processes are considered. The microstructure-properties correlations constitute the major contribution of this work, which provide a link to the materials science paradigm and give for example an explanation for the damage of a cast part during its development phase. The other major contribution developed in Part B is the development of a new metallurgical tool, the so-called TTB concept. TTB concept may serve as a basic tool for understanding the mechanisms of solid phase transformations. Moreover, it may help to develop kinetic models that are more adapted to additive manufacturing processes. [less ▲]

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See detailEtude des zones faillées et des formations superficielles de Fond Parisien et Gros-Morne en Haïti à partir de méthodes géophysiques, géotechniques et microsismiques en vue d'évaluer le risque sismique
Ulysse, Sophia Marie Johanne ULiege

Doctoral thesis (2020)

La République d’Haïti, couramment Haïti, occupe la partie occidentale de l’Ile d’Hispaniola et est située à la frontière des plaques tectoniques Nord-Américaine et Caraïbes. Elle est traversée par ... [more ▼]

La République d’Haïti, couramment Haïti, occupe la partie occidentale de l’Ile d’Hispaniola et est située à la frontière des plaques tectoniques Nord-Américaine et Caraïbes. Elle est traversée par plusieurs failles actives. Les mieux connues sont la faille Septentrionale et la faille Enriquillo Plantain Garden (EPG) qui sont deux failles majeures de direction plus ou moins E-Wparcourant respectivement le nord et le sud du territoire. A cause de la présence de ces structures, Haïti est exposée à un aléa sismique majeur qui, associé au niveau élevé de vulnérabilité de la population, donne lieu à un haut risque sismique capable de provoquer des catastrophes telles que celle liée au séisme du 12 janvier 2010. Ce tremblement de terre de magnitude 7 est l’un des plus meurtriers de l’histoire, laissant à son compte environ 200000 morts, 300000 blessés, près de 1.5 millions de sans-abris et des pertes économiques équivalentes à la presque totalité du produit intérieur brut (PIB). Un tel événement n’est certainement pas le dernier à se produire en Haïti qui, dans le passé, a déjà connu plusieurs séismes majeurs dont ceux de 1751 et de 1770 qui ont ravagé Port-au-Prince et celui de 1842 qui a détruit la ville du Cap-Haïtien. Et pour rappel, le séisme du 6 octobre 2018, soit 8 ans après, d’une magnitude de seulement 5.9, a provoqué des dégâts significatifs dans le nord-ouest du pays. Afin de contribuer à l’amélioration de la prévention du risque sismique, un projet de coopération entre la Belgique et Haïti (PIC 2012 - 2016) a été mis sur pied. La présente thèse de doctorat s’inscrit dans le cadre de ce projet et a pour objectif l’étude de l’aléa sismique local sur deux zones situées le long de la portion Est de la faille Enriquillo Plantain Garden, sur les contreforts du massif de la Selle. La première, Fond Parisien, est une zone rurale, localisée à proximité de la frontière haïtiano-dominicaine et représente une zone probable d’extension de la capitale, Port-au-Prince. La seconde, Gros-Morne, est une petite colline entièrement construite et située plus près de Port-au-Prince, et qui a été sévèrement touchée lors du tremblement de terre du 12 janvier 2010. Cette étude est réalisée à partir de méthodes géophysiques de surface. La technique du rapport spectral H/V a été appliquée pour étudier la fréquence de résonance des sites cibles et l’azimut du champ d’ondes. De plus, l’évaluation des facteurs d’amplification a été réalisée en utilisant des rapports spectraux site sur référence (SSR) obtenus à partir de tremblements de terre enregistrés par un réseau sismique temporaire installé sur chacune des deux zones. En utilisant la méthode d’analyse multitrace des ondes de surface (MASW), les propriétés sismiques des couches peu profondes ont été étudiées. Puis, les résultats ont été comparés aux données locales de tomographie de résistivité électrique (ERT). Enfin, les résultats de la fréquence de résonance fondamentale, de l’amplitude et de la vitesse de l’onde de cisaillement ont été cartographiés et combinés pour obtenir la distribution des effets de site ou de l’aléa local. Ces résultats mettent en évidence une zone E-W de faibles vitesses et de faibles résistivités dans la partie centrale de Fond Parisien. Ces faibles vitesses vont de 200 m/s à 450 m/s et sont dû à des causes à la fois tectoniques et lithologiques. Les causes tectoniques sont liées au plissement des roches alors que les effets lithologiques qui ont été observés dans la partie Est sont le résultat d’un remplissage sédimentaire marqué par des résonances à une ou plusieurs fréquences allant de 0.7 Hz à 20 Hz. Les faibles valeurs de résistivités sont comprises entre 1 m et 150 m et sont causées non seulement par des activités tectoniques et la présence de sédiments fins mais encore par l’infiltration et le stockage d’eau saumâtre dans les couches souterraines. On note aussi une influence significative de la faille EPG sur l’orientation principale du champ d’ondes sismique. Au voisinage de cette faille, les azimuts sont en effet parallèle à l’orientation de la faille. Ces résultats montrent aussi de plus forts potentiels d’effets de site dans le bassin sédimentaire. De fortes amplifications du mouvement sismique ont été mesurées pour les sites bordant le bassin au nord et à l’ouest. Au nord et au sud-ouest, ces amplifications ont probablement pour origine des irrégularités topographiques localement couplés à des dépôts de sédiments tandis qu’au centre de la partie ouest, l’effet de site résulte d’activité de plissement. Pour la colline de Gros-Morne, en plus de l’application des méthodes géophysiques de surface, les effets de site ont été investigués à partir d’une géomodélisation 3D d’une modélisation numérique permettant de déterminer l’influence de la topographie sur l’amplification du mouvement sismique. L’ensemble des mesures géophysiques montrent un potentiel d’effet de site allant globalement de faible à modéré enregistrés. Les plus forts potentiels d’amplification du mouvement sismique sont susceptibles d’être observés dans la partie sud ouest de la colline tandis que les effets de site les plus faibles seront enregistrés au sommet et dans la partie N-E de la colline. Les rapports spectraux H/V montrent cependant une grande variabilité de fréquences de résonance et d’amplitudes, en particulier sur le sommet de la colline, autour de l’Hotel Montana où les valeurs de fréquence de résonance et d’amplitude varient sur de très courtes distances. Les amplitudes vont généralement de faibles à modérées (1.5-6.5) à une ou plusieurs fréquences différentes pour le même site. Les fréquences de résonance sont comprises entre 0.5 et 24 Hz mais avec une prédominance de celles comprises entre 7 et 10 Hz. Les vitesses d’ondes de cisaillement varient de 300 à 700 m/s pour une profondeur de 15 à 20 m, avec les valeurs les plus élevées mesurées dans la partie N-E de la colline et à son sommet également marqué par les résistivités les plus élevées. En combinant les résultats de MASW et ceux des rapports spectraux H/V bruit ambient, nous avons pu procéder à une estimation de l’épaisseur des couches superficielles résonantes. Les résultats de cette évaluation qui a permis de mettre en évidence des couches plus épaisses au coin S-W de la colline ont été utilisés pour produire un modèle de représentation 3D de la colline. Notre modélisation numérique étudie l’amplification du mouvement sismique en appliquant la technique de rapports spectraux site sur référence (SSR) en diverses stations fictives placées le long d’une section transversale (extraites du géomodèle 3D) parallèle à l’axe le plus court de la colline et passant par le sommet de cette dernière. Elle considère deux modèles: l’un purement topographique et l’autre incluant une composante liée à l’effet d’une couche superficielle meuble surplombant le rocher. A partir de la modélisation numérique, nous avons pu détecter un peak topographique aux environ de 1 Hz dont l’amplitude est d’autant plus élevée qu’on est plus proche du sommet et d’autant plus faible qu’on se rapproche du pied de la colline. Ce peak qui est aussi identifié sur les courbes de rapports spectraux NS calculés en utilisant les données de séismes enregistrés par les stations du réseau temporaire, nest pas dètectè par les mesures H/V bruit ambient. Ce qui laisse supposer une incapacité dela méthode H/V bruit ambient à investiguer les effets de site topographiques. Ces modèles mettent également en évidence des peaks à plus haute fréquence dont l’origine est liée à aux effets combiné des couches de surface etde la topographie. Dans l’ensemble, ce travail de recherche a permis une meilleure compréhension de la distribution de l’aléa sismique local sur les deux sites cibles. A partir d’une méthodologie nouvellement appliquée à Haïti consistant en une intégration de plusieurs méthodes géophysiques, il a permis de distinguer, pour Fond Parisien, des zones où l’on peut très bien construire. Cellesci sont localisées dans la partie nord et englobent le Parc Quisqueya et les terrains situés à l’Est de ce parc ainsi que le village ‘La Source’ dans la partie sud. Cependant, de potentiels risques d’inondation doivent être pris en compte dans le village. Dans le reste de Fond Parisien, soit la partie centrale et la partie sud, on devrait construire avec prudence en tenant compte de la forte influence de la faille EPG et des couches de sédiments fins sur l’amplification du mouvement sismique. Pour la colline de Gros-Morne, cette thèse préconise un couplage d’effets topographiques et lithologiques à l’origine de l’amplification du mouvement sismique. La même approche intégrée a permis d’établir une correspondance entre les dommages observés suite au séisme du 12 janvier 2010 et des amplifications dû à la présence de couches meubles en surface uniquement pour certaines parties de la colline, laissant ainsi supposer que d’autres facteurs tels que la vulnérabilité des constructions peuvent avoir joué un rôle crucial dans l’intensité des dégâts observés. Ce travail a en outre permis de faire ressortir la complexité des effets de site au sommet de la colline marqué par une grande variabilité de l’amplification sur des distances de l’ordre de la dizaine de mètres. Laquelle variabilité n’aurait pas pu être détectée par un travail de macrozonage. [less ▲]

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See detailThin films for applications in generation and storage of electrical energy
Exantus, Chellda ULiege

Doctoral thesis (2020)

The PhD was focused on the development of metal oxides thin films using sol-gel process, for various applications. It is part of the overall context of the European EnSO (Energy for Smart Objects) project ... [more ▼]

The PhD was focused on the development of metal oxides thin films using sol-gel process, for various applications. It is part of the overall context of the European EnSO (Energy for Smart Objects) project, funded by the Electronic Components and Systems for European Leadership Joint Undertaking (ECSEL-JTI), in collaboration with the European Union's H2020 Framework Programme (H2020/2014-2020) and national authorities. The project aimed at developing autonomous micro energy sources, including both an energy harvesting system and a storage system. As the ULiège NCE laboratory was involved in the development of both parts, and following a general reorientation of the project at mid-term, the candidate was led to work on two different types of materials. This PhD thesis is thus presented in two distinct parts. The first part concerns the optimisation of a process for the growth of zinc oxide nanowires (ZnO NWs) for piezoelectric nanogenerator application. The objective was to develop a process for the synthesis of NWs on a substrate, with a growth rate compatible for industrial scale-up (minimum 20 nm min-1). A combined process including (i) the deposition of a seed layer made of ZnO crystallites followed by (ii) ZnO NW growth using wet chemistry was developed at the NCE laboratory. The study of the different steps of the process, as well as the growth kinetics of the NWs, made it possible to optimise the conditions of deposition and to obtain a growth speed compatible with industrial scale (70 nm min-1). By combining the results with those obtained by other researchers in the project, it was possible to obtain materials that can be used for the manufacture of piezoelectric nanogenerators, as shown by the characterisations after assembly, in collaboration with the Greman laboratory (Tours). The NWs were also characterised as photocatalysts for the potential decomposition of pollutants in water, thus showing the diversity of possible applications. The second part focuses on the optimisation of porous layers for positive electrodes of Li-metal batteries. Optimisation was based on the use of Li7La3Zr2O12 (LLZO), an ionic conductor synthesised by sol-gel process, as nanostructured solid electrolyte within the electrode. The final objective of the project, carried out mainly in collaboration with Prayon s.a. and CEA-Leti (Grenoble), was to produce solid-state Li-metal/LCO microbatteries. The aim of the thesis, which is based on the work of another researcher from the NCE laboratory, was to improve the ionic conductivity of the positive electrode layers by filling their porosity with the nanostructured LLZO. Hybrid LCO-LLZO layers preserving the electrochemical properties of the active electrode material were prepared and the characterisations carried out by adding a liquid electrolyte showed that the LCO does not undergo any alteration in the presence of LLZO. Finally, preliminary encouraging results were obtained when replacing the liquid electrolyte with the gel polymer electrolyte (GPE) developed at NCE: the addition of LLZO to the LCO electrode resulted in a microbattery that is stable when cycling at 1C. [less ▲]

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See detailDes fines de brique de terre cuite comme liants de substitution dans les ciments et les matériaux alcali-activés
Grellier, Adèle ULiege

Doctoral thesis (2020)

The construction industry today produces an enormous amount of waste, especially during the deconstruction and demolition of buildings. Terracota brick, which is the subject of our study, represents a ... [more ▼]

The construction industry today produces an enormous amount of waste, especially during the deconstruction and demolition of buildings. Terracota brick, which is the subject of our study, represents a significant part of this inert waste in some regions. The recycling of bricks is already carried out in the form of aggregates used for example in road embankments. But this constitutes what is called a "downcycling" operation. The investigated way is a valorization with higher added value via the elaboration of mixed hydraulic binders based on brick fines which are not valorized at present. The first way of valorization is the substitution of Portland cement composite based in reference brick fines with three granulometries (D50 de 3 µm, 20 µm et 180 µm) on the had and fines brick from demilition sites (D50 = 20 µm) on the other hand. The second valorization way is the use of alkali-activated materials, by means of substitution of blast furnace slag (GGBFS) by brick fines with a grain size D50 = 20 µm. The objective of the study is to understand the impact of the incorporation of brick fines in these two binders. The approach is a chemical, physical and mechanical characterization over time of the new binders. Valorization in cement is conclusive when substitution rates up to 20%: the performance of the material is equivalent to that of the control cement. For alkali-activated materials, it is shown that brick fines can be a precursor equivalent to GGBFS and thus lead to mechanical performances equivalent to control even up to 50% substitution rate in brick fines. Under certain conditions of alkali-activated solution concentration, the addition of 30% brick fines can greatly improve workability time. This certainly leads to a decrease in mechanical performance, but it is still in accordance with the construction needs. [less ▲]

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See detailIsotopic and microbiologic evidence of greenhouse gases transformation mechanisms in groundwater
Nikolenko, Olha ULiege

Doctoral thesis (2020)

One of the major global challenges of this century is to find the balance between the intensive agricultural production and the environmental damage that it causes by contributing to climate change and ... [more ▼]

One of the major global challenges of this century is to find the balance between the intensive agricultural production and the environmental damage that it causes by contributing to climate change and deterioration of water resources and soils. Agriculture accounts for up to one third of anthropogenic emissions of greenhouse gases (GHGs) which exacerbate the climate change (increase in nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2)) and lead to the depletion of stratospheric ozone layer (N2O). Recent studies have suggested that in agricultural areas groundwater systems might be the significant sources of GHGs emissions, especially N2O, to the atmosphere due to intensive application of nitrogen containing inorganic and organic fertilizers used to increase soil fertility. However, the dynamics of N2O, CH4 and CO2 in aquifers is still poorly characterized due to the insufficient insight into kinetics and controls of processes regulating their production, transport and consumption. That is why, it is important to obtain more information regarding functional zones controlling fate of GHGs in subsurface. This knowledge is important for constraining the GHGs budgets, understanding the mechanisms behind climate change and developing mitigation measures to stop the rise of concentrations of N2O, CH4 and CO2. In this context this study focuses on evaluating the potential role of aquifers affected by the agricultural activities as a source of GHGs emission to the atmosphere and improving the understanding of the impact of the spatial heterogeneity of subsurface media on the dynamics of N2O production and consumption processes. In this project advanced techniques and methods from hydrogeological, isotope and microbiological fields were used for investigation of the actual subsurface conditions and analysis of their impact on production and consumption of N2O in groundwater. The study was divided into two stages: 1) regional investigations and 2) local-scale explorations. The main aim of the regional survey was to examine the distribution and accumulation of GHGs in different parts of the studied aquifer across its lateral and vertical dimensions and to obtain better information regarding the hydrogeochemical conditions of the subsurface. Meanwhile, the local scale investigations were focused on the occurrence of biochemical stratification in the same aquifer and analysis of its impact on N2O dynamics. It aimed to identify and quantify the rates of N2O production/consumption processes using data obtained from ambient groundwater and laboratory designed experiments. Since N2O production and consumption processes can proceed through abiotic and biotic pathways, the measurements of the activity of the microorganisms that accomplish biotic N transformations were conducted to obtain more information about N2O dynamics. [less ▲]

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See detailModelling forest dynamics to assess and improve forest management at a regional scale: an analysis of forest changes in Wallonia (southern Belgium).
Perin, Jérôme ULiege

Doctoral thesis (2020)

Covering one-third of the world's land, forests provide many essential resources and services on which more than 25% of the world's population directly depend for their livelihoods. Moreover, because of ... [more ▼]

Covering one-third of the world's land, forests provide many essential resources and services on which more than 25% of the world's population directly depend for their livelihoods. Moreover, because of their importance in the carbon and water cycle and in the production of renewable materials, forests are one of the main means of mitigating the consequences of current and future global climate change. The need to balance ecological, economic and social roles to achieve sustainable management of forest resources is therefore evident from the local to the global scale. Accurate and up-to-date information on forests dynamics is essential to design and implement sustainable forest management plans. In particular, the development of customized management scenarios based on forest stand characteristics require accurate growth and yield estimates that can only be derived from permanent forest inventory data. This thesis focuses on the relevance of forest modelling from permanent forest inventory data to improve knowledge on current forest resource stocks and dynamics and help design sustainable forest management policies. The study concerns the forests of Wallonia, the southern Region of Belgium. Wallonia forests represent an interesting case study as they are intensively managed, highly fragmented, heterogeneous in structure and composition and undergoing fast change to adapt to new environmental and economic conditions. The first part of this thesis concerns the research for an appropriate modelling methodology to assess the level of productivity and species-station suitability of forest plantations. We developed an easily replicable methodology relying on stem analysis data to fit robust site index (SI) models which make it possible to estimate the level of productivity of plantations according to their top-height and age. New SI models were calibrated for the three main plantation species in Wallonia: Norway spruce, douglas-fir and Larches. These new models make it possible to account for the significant changes observed in the SI distribution over time which caused biases in previous ones. Our work suggests that these changes are mainly due to later harvesting and lower replanting rate of softwood plantations located on less productive sites, practices that are not exclusive to Wallonia. The second part of this work concerns the development of forest models able to accurately estimate the effect of original management scenarios on the development of forest resources. Using our new SI models and thousands of field experiment data allowed us to develop new harmonized growth models for even-aged pure stands of Norway spruce, douglas-fir and larches that have a wider validity than is possible with regional data. They highlight the very significant effect of stand density and social status on individual tree growth and demonstrate a lasting effect of early selective thinning on growth which does not decline as rapidly with age as previously thought. We also found that under similar growing conditions, douglas-fir yields are one-third higher than Norway spruce and larches. An economic analysis of the evolution of harvest revenues in Norway spruce and douglas-fir plantations also shows that although the actualized value of final harvests peaks at around 60 years, selective thinning can provide significant regular income until much later. The final part of this thesis concerns the design of a forest modelling methodology that A) provides detailed estimates about stock, growth, yield and harvested volumes, B) allows a direct use of permanent forest inventory data for calibration and initiation of the simulation, and C) can be applied at the regional level. It resulted in the development of the individual-tree distance-independent forest model SIMREG which is based on permanent data from the Permanent Forest Inventory of Wallonia (IPRFW). The tree-level approach made it possible to identify several inconsistencies in previous estimates from the IPRFW. In particular, we conclude that the net growing stock increase between the first and the second IPRFW cycle was previously overestimated by several million m³ while the total yield was underestimated by about 25%. These differences result from SIMREG's consideration of previously unmeasured forest resources and significant methodological changes between the two IPRFW cycles. Our simulations also confirm the rapid decline of spruce in favour of douglas-fir and various hardwood species but suggest that the higher yield of douglas-fir and the renewal of aging/low productive Norway spruce plantations could mostly compensate for the net decline in softwood forest area. We conclude that the standing stock of Walloon forests is managed sustainably overall but not at the species level. The decline of the Norway spruce plantations is arguably justified by numerous relevant reasons such as its presence in unsuitable stations, its sensitivity to drought, bark beetles and windfall damage, the higher yield of douglas-fir, etc. Nevertheless, Norway spruce is still the main production species in Wallonia and our work has resulted in several new recommendations to improve its management and that of its main substitute species: douglas-fir. Forest modelling and simulation is a timely issue and similar work is currently being done worldwide. Although our study has focused on Wallonia, our modelling methods were designed to only use data collected by most permanent NFI. For example, SIMREG was successfully adapted to the Flemish and Brussels forests in order to develop the national forest accounting plan of Belgium. We are thus confident that our modelling framework is generalizable to other countries. [less ▲]

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See detailUne socio-anthropologie du syndrome d'Asperger dans ses relations à la nature et aux animaux : de la marginalisation au renouvellement identificatoire et culturel
Marchionni, Anna-Livia ULiege

Doctoral thesis (2020)

L'existence de particularités de perception sensorielle chez les personnes autistes est aujourd'hui avérée (Gepner, 2014) ; dans le DSM-V1, elles sont considérées comme un symptôme à part entière des ... [more ▼]

L'existence de particularités de perception sensorielle chez les personnes autistes est aujourd'hui avérée (Gepner, 2014) ; dans le DSM-V1, elles sont considérées comme un symptôme à part entière des « troubles du spectre autistique » ; nombreuses sont les personnes autistes à en témoigner (Grandin, 1984 ; 1988 ; Jollife, 1992 ; Williams, 1992 ; Willey, 1999 ; Tammet, 2006) ; certains adultes autistes Asperger considèrent même que leur sensibilité sensorielle est une source de plus de difficultés quotidiennes que les questions de socialisation et d'insertion sociale (Attwood, 2010). L'enjeu de ce travail est d'explorer la relation de personnes autistes Asperger à la nature et aux animaux dans une approche qualitative, sociologique et anthropologique, par le recueil d'entretiens approfondis et par des enquêtes ethnographiques aux domiciles de deux participantes (dans une communauté anarchiste dans les Cévennes et dans un manoir isolé en Sologne). Je me suis intéressée aux processus subjectifs déployés par les participants afin de questionner leurs représentations des environnements naturels et de leurs liens aux animaux ainsi que leurs expériences sensorielles quotidiennes et les processus subjectifs qu'elles déploient en fonction de leur environnement. Les analysent ont montré comment, lorsque les autistes prennent la parole, celle-ci parle davantage de la société que de l'autisme, et remet en question les concepts culturellement ancrés dans l'ontologie naturaliste et dualiste de nos sociétés occidentales de la norme et du handicap, de la nature et des animaux, entraînant marginalisation des différents et exploitation des ressources naturelles. Ce que cette parole apporte, c'est un autre point de vue sur la société et sur la manière de catégoriser les êtres. Elle pose des questions politiques dans la mesure où elle exprime une demande de changement dans la prise en charge et le statut social des individus porteurs de différences ; politiques aussi dans la mesure où cette parole, en déstabilisant les normes validistes et la logique spéciste qu'elle entraîne, remet en question l'économie capitaliste des sociétés occidentales responsables de la destruction de la planète, amenant à la question bien plus large d'une possible transition ontologique en cours dans nos sociétés pour faire face à la crise écologique mondiale. [less ▲]

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See detailCAN EDDY-COVARIANCE BE USED ON A PASTURE? ESTIMATION OF CATTLE AND SOIL- PLANT METHANE EMISSIONS AND TRANSFER TO OTHER GREENHOUSE GASES.
Dumortier, Pierre ULiege

Doctoral thesis (2020)

Much debate has arisen as to the contribution of natural and anthropized ecosystems to the global production of greenhouse gases (GHG), ways to limit this contribution or how to use ecosystems as carbon ... [more ▼]

Much debate has arisen as to the contribution of natural and anthropized ecosystems to the global production of greenhouse gases (GHG), ways to limit this contribution or how to use ecosystems as carbon sinks. To provide solid ground for this debate, reliable data is required. Eddy-covariance (EC) is commonly used to measure gaseous exchanges from homogeneous ecosystems (crops, forests…). However, in its standard form, it may be biased when working with heterogeneous ecosystems, especially grazed pastures where cattle is an important, but also moving and intermittent GHG source. In this thesis, using data from the Dorinne ecosystem station, a Belgian pasture grazed by Belgian Blue beef, we disentangled cattle methane (CH4) and carbon dioxide (CO2) exchanges from soil-plant exchanges. This work allowed us estimate cattle CH4 and CO2 emissions and compute an un-biased pasture GHG budget. Our work therefore opens the door to a wider use of EC on grazed pastures and thus the monitoring of this important ecosystem. In practice, EC measures gaseous exchanges from an area upwind from the measurement mast. Each area contribution to the measured flux can be computed using a mathematical model (footprint model). We combined this footprint model with cattle positions on the pasture, obtained using GPS-collars, and EC in order to estimate cattle CH4 emissions. The proposed method was validated through an artificial tracer experiment where source recovery rates were between 90 and 113% and no bias was associated with atmospheric conditions or the distance between the source and the measurement mast. Applying this validated method on grazing Belgian Blue cows led to estimated CH4 emissions of 220 ± 35 gCH4 head−1 day−1. Cow’s behavior was also monitored and presented a clear daily pattern of activity with more intense grazing just after sunrise and right before sunset. However, no significant CH4 emission pattern could be associated with it, indicating that the diurnal emission variation might be lower than the measurement uncertainty range. We extended our method to cattle CO2 emissions. To avoid the need for cattle geolocation, we used CH4 fluxes as an indicator of cattle presence in the footprint. This allowed us by-passing labor intensive handling of cattle, thus making our method easier to use on a large number of test sites. Using this method, estimated cow CO2 emissions were of 3.2 ± 0.5 kgC head−1 day−1. Moreover, we computed a pasture GHG emission (CO2, CH4 and N2O) of 629 ± 296 gCO2eq m−2 yr-1. This figure should be handled with some precautions as it is site specific, dependent on budget boundaries and subject to annual variations. [less ▲]

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