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See detailSelf-Assembly and Evaporation of Superparamagnetic Colloids
Darras, Alexis ULiege

Doctoral thesis (2019)

The evaporation of colloidal droplets is an area of intensive research. From paint coating to blood analysis on crime scene, applications of patterning from evaporation of colloids are numerous and ... [more ▼]

The evaporation of colloidal droplets is an area of intensive research. From paint coating to blood analysis on crime scene, applications of patterning from evaporation of colloids are numerous and various. In our work, we aimed to bring highlight on how interactions between colloidal particles influence the eventual deposit's pattern. To do this we used superparamagnetic colloids as a way to have a tunable interaction with these particles. We first studied the influence of dipolar interactions on the suspension of particles. We performed systematic experiments to characterize the thermodynamic equilibrium reached by the suspensions. We showed that tuning the viscosity parameter could be used to speed-up numerical simulations. We used this process in sped-up simulations in order to study a new range of volume fraction. We showed that high volume fraction conditions led to higher chains' length than expected. We proposed a modification of current models. We then focused on evaporating droplets. We began by reviewing the liquid flows in our suspensions. We showed there was a competition between coffee-ring flow and Marangoni instability. We then characterized the deposits left after evaporating suspensions under magnetic fields, and showed the influence of both this parameter and the Marangoni instability on the eventual deposits. We evidenced a transition in the deposit's behaviour when the DLVO interaction between the particles and the substrate becomes attractive. [less ▲]

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See detailThe Smart Point Cloud: Structuring 3D intelligent point data
Poux, Florent ULiege

Doctoral thesis (2019)

Discrete spatial datasets known as point clouds often lay the groundwork for decision-making applications. E.g., we can use such data as a reference for autonomous cars and robot’s navigation, as a layer ... [more ▼]

Discrete spatial datasets known as point clouds often lay the groundwork for decision-making applications. E.g., we can use such data as a reference for autonomous cars and robot’s navigation, as a layer for floor-plan’s creation and building’s construction, as a digital asset for environment modelling and incident prediction... Applications are numerous, and potentially increasing if we consider point clouds as digital reality assets. Yet, this expansion faces technical limitations mainly from the lack of semantic information within point ensembles. Connecting knowledge sources is still a very manual and time-consuming process suffering from error-prone human interpretation. This highlights a strong need for domain-related data analysis to create a coherent and structured information. The thesis clearly tries to solve automation problematics in point cloud processing to create intelligent environments, i.e. virtual copies that can be used/integrated in fully autonomous reasoning services. We tackle point cloud questions associated with knowledge extraction – particularly segmentation and classification – structuration, visualisation and interaction with cognitive decision systems. We propose to connect both point cloud properties and formalized knowledge to rapidly extract pertinent information using domain-centered graphs. The dissertation delivers the concept of a Smart Point Cloud (SPC) Infrastructure which serves as an interoperable and modular architecture for a unified processing. It permits an easy integration to existing workflows and a multi-domain specialization through device knowledge, analytic knowledge or domain knowledge. Concepts, algorithms, code and materials are given to replicate findings and extend current applications. [less ▲]

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See detailCharge-sensitive methods for the off-design performance characterization of organic Rankine cycle (ORC) power systems
Dickes, Rémi ULiege

Doctoral thesis (2019)

The organic Rankine cycle (ORC) is among the most suited technologies to convert low-grade and low-capacity heat sources into useful work. For many reasons - including predictive control, optimal sizing ... [more ▼]

The organic Rankine cycle (ORC) is among the most suited technologies to convert low-grade and low-capacity heat sources into useful work. For many reasons - including predictive control, optimal sizing or performance forecast - a proper understanding and characterization of the ORC behaviour under off-design conditions is of significant interest. In order to avoid any intrinsic state assumption, predictive models must account for both fundamental conversation laws of hermodynamics, namely the conservation of energy and the conservation of mass. Besides of modelling the energy transfers, a true off-design model must account for the constant amount of working fluid in the system and simulate its distribution among the different components. Although well-known for HVAC systems, such charge-sensitive considerations are quasi absent for the ORC technology and existing models have never been completely validated. The goal intended by this PhD thesis is to fill this gap. To begin this work, experiments are conducted to assess the fluid distribution and the impact of the charge on a real system operation. To this end, a 2 kWe ORC test rig is constructed and tested over wide range of conditions. Besides of standard thermohydraulic sensors, the fluid charge distribution is measured on-line by bending load cells and infrared imaging techniques. Following a complete experimental campaign (which includes more than 300 steady-state points), a dual reconciliation method is applied on the raw measurements to obtain a reference dataset. An extensive study of the experimental data is then conducted. Among many results, the important contribution of the heat exchangers in the charge inventory is highlighted, so as the impact of oil circulation on the ORC performance rating. Following this experimental study, a complete modelling library is developed to replicate and extrapolate the system off-design behaviour. The intended goal is to create a true performance simulator, i.e. a predictive tool able to estimate the ORC behaviour based solely on its boundary environment (without state assumption, i.e. accounting for the charge distribution in the system). In a first step, a miscibility model of R245fa/POE oil is developed to account for the presence of the lubricant in the ORC operation. Afterwards, the modelling of each system component is conducted, with a particular focus on the heat exchangers and their charge estimation. Then a global ORC model is constructed by coupling the various components sub-models accordingly to a robust resolution scheme. The ORC model predictions are ultimately confronted to the experimental measurements, both in terms of thermodynamics and charge inventory predictions, and a good fit is demonstrated for all the model outputs. Finally, the utility of such a charge- and lubricant-sensitive ORC model is highlighted for different tasks. Considering the experimental test rig as case study, the off-design modelling tool is employed (i) to fully characterize the ORC response under off-design conditions, (ii) to prevent operating conditions where pump cavitation is likely to occur, (iii) to build optimal performance mappings for full- and part-load operations, and, finally, (iv) to optimally select the charge of working fluid and to accordingly size the liquid receiver. [less ▲]

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See detailRôles sociaux, construction identitaire, pouvoir et contre-pouvoir. Les femmes dans la société podoko des monts Mandara (Cameroun)
Mahama, Abel ULiege

Doctoral thesis (2019)

Cette thèse se propose d’étudier les formes de pouvoir et de contre-pouvoir exercées par les femmes dans la société podoko de l’Extrême-Nord du Cameroun. Notre recherche a notamment été guidée par les ... [more ▼]

Cette thèse se propose d’étudier les formes de pouvoir et de contre-pouvoir exercées par les femmes dans la société podoko de l’Extrême-Nord du Cameroun. Notre recherche a notamment été guidée par les questions suivantes : en quoi le rôle et le statut des femmes dans la société podoko sont-ils révélateurs de ces formes de pouvoir et de contre-pouvoir féminins ? Comment se construisent les identités sexuelles et féminines dans les représentations sociales et les usages chez les Podoko, en particulier dans la prise en charge des enfants et au regard de celles des hommes ? Quel rôle jouent le mariage et le travail dans l’émancipation et le pouvoir économique des femmes ? Comment se manifestent les pouvoirs et les contre-pouvoirs des femmes de la société podoko dans les différentes sphères de leur vie quotidienne ? Notre hypothèse générale est que les activités quotidiennes, même les plus anodines, participent de la construction de formes de pouvoir et de contre-pouvoir des femmes. Celles-ci s’expriment au travers des non-dits, des actes et aussi des discours qui traversent les différents espaces et les différentes sphères de la vie sociale. Sur le plan théorique, plusieurs champs et notions ont été mobilisés pour étudier, analyser et interpréter les données : le courant des gender studies, pour étudier la construction du rôle et du statut des femmes, la notion de « valence différentielle » des sexes, mais aussi les champs théoriques que sont l’anthropologie du corps et l’anthropologie de l’enfance, pour étudier l’intervention des femmes auprès des enfants. Concernant la méthodologie, nous avons opté pour des observations directes et participantes, et des entretiens en mettant l’accent sur les modes d’expression et de développement des différentes masculinités et féminités, les pratiques économiques, la prise en charge de l’enfant, et les activités liées à la vie politique et religieuse. Confirmant les hypothèses de notre recherche, l’analyse des matériaux produits et recueillis et leur interprétation montrent que l’analyse des discours formels ne suffit pas pour comprendre en profondeur les relations de pouvoir et de contre-pouvoir, et la répartition des pouvoirs, entre les femmes et les hommes dans la société podoko. [less ▲]

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See detailSocio-cultural characterization of historic urban landscapes: an integrated approach based on the use of social media
Ginzarly, Manal ULiege

Doctoral thesis (2019)

Cultural heritage, in its manifold expressions, is as a key urban component that (i) adapts and evolves through time with the changes occurring in the city, and at the same time maintains its identity ... [more ▼]

Cultural heritage, in its manifold expressions, is as a key urban component that (i) adapts and evolves through time with the changes occurring in the city, and at the same time maintains its identity, integrity, and continuity, and (ii) enables and drives the social, economic, and environmental dimensions of sustainable development. The recent 2011 UNESCO Recommendation on the Historic Urban Landscape (HUL) called for the application of a value-based landscape approach to urban management to ensure the integration of cultural heritage conservation concerns within the wider framework of sustainable urban development. The Recommendation declared cultural heritage to be a social construct, subject to diverse associations of meanings related to personal experience, knowledge, practices, and change over time, and challenged existing methods for the characterization and mapping of urban landscape. This thesis follows this conceptualization and develops a novel method that integrates traditional and innovative tools to grasp the range of cultural values attributed by the different stakeholders to the urban landscape, and to provide insights into all facets of the perceived landscape character. In this regard, Tripoli, Lebanon is taken as a cased study to apply the proposed method. This thesis draws attention to the social co-construction of meanings of everyday landscape. It goes beyond historic centers and designated heritage to address the city as a whole and recognize in-between liminal spaces, where heritage boundaries are challenged, alternatives to dominant narratives of identity are articulated, and diverse cultural values are claimed through community interests and social activism. First, this thesis identifies the prospects and challenges for the application of a value-based landscape approach to urban management. Second, it applies the proposed method to the characterization of the HUL. Third, it recalls the dissonant, conflictual, and process-based character of heritage values, and investigates the role of “non-expert” actors in shaping the dynamics of heritage production. In doing so it addresses both collective and connective action. The latter is built upon online communities and digital activism. The results show that value judgments are very complex in nature and are bounded by the local sociopolitical structure and economic conditions. Another important finding of this thesis is that the analysis of social media metadata provides additional knowledge about everyday encounters with the HUL, and that digital platforms play a role in building online communities that contribute to the co-production of local knowledge and that challenge authorized understanding of heritage. [less ▲]

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See detailThe Quaternary biogeographic history of bryophytes: a window into their ability to face global change
Ledent, Alice ULiege

Doctoral thesis (2019)

Studying the influence of past climate changes on the distribution of species contributes to our understanding of the evolution of life on earth. Among past climate changes, the Quaternary period (from 2 ... [more ▼]

Studying the influence of past climate changes on the distribution of species contributes to our understanding of the evolution of life on earth. Among past climate changes, the Quaternary period (from 2.4 Myrs to present time), characterized by high amplitude climatic oscillations, is considered one main determinant of current species distributions. Europe has long served as a model region to study the impact of past climate changes on extant biodiversity patterns. Its landscape is characterized by the presence of E-W-oriented mountain ranges, acting as effective barriers to migration for many organisms. Explicit historical scenarios for the post-glacial recolonization of Europe from distinct refugia have been discussed at length in the literature. In contrast, the impact of past climate changes on species distributions in tropical areas has been much less documented. In Amazonia, where the landscape is homogeneous without any apparent geographic barrier to migration, available fossil evidence describes range contractions and expansions of the evergreen rainforest during the Quaternary period. Bryophytes are poïkilohydric and therefore appear as extremely sensitive to climate changes. Bryophytes disperse by means of spores or asexual diaspores, which are involved in frequent long-distance dispersal (LDD) events. These high dispersal capacities have cast doubts on the possibility to find signatures of historical events from analyses of the extant spatial patterns of genetic structure and diversity of their populations. In Amazonia in particular, recent ecological work suggests that dispersal does not show geographical structure across the area. In the present thesis, we assembled and analyzed large molecular datasets at the level of the species range to determine how bryophytes responded to major Quaternary climate changes in environments characterized by different ‘resistance’ to migration and environmental heterogeneity, especially in Europe and Amazonia (ongoing study in the case of the latter). More specifically, the aims are to: (1) Test whether, due to the high dispersal capacities of bryophytes in general – and in particular in homogeneous environments without any apparent geographic barrier to migration –, the inverse isolation hypothesis – according to which any signal of isolation-by-distance (IBD) is erased beyond the limits of short-distance dispersal (SDD) by the intensity of LDD events – applies, erasing any historical signal in the extant spatial patterns of genetic structure and diversity of bryophyte populations; (2) Test the relevance of other differentiation mechanisms promoting speciation and, in particular isolation-by-environment (IBE), across a relatively homogeneous environment without any apparent geographic barrier to migration; (3) Infer the post-glacial history of bryophytes, in environments characterized by the presence (Europe) or the absence (Amazonia, ongoing study) of apparent geographic barriers to migration, from analyses of the extant spatial patterns of genetic structure and diversity of their populations. The results strongly suggest that the LDD capacities of bryophytes did not homogenize the genetic structure of their populations, neither in an environment characterized by apparent geographic barriers to migration – such as the E-W-oriented mountain ranges in Europe –, nor in a much more homogeneous environment as in the Amazonian rainforest. In contradiction with the idea that the inverse isolation hypothesis applies in Amazonian bryophytes in particular, the IBD signal observed in 8 out of the 10 Amazonian bryophyte species consistently remained significant beyond the range of SDD, evidencing LDD limitations. This consistent persistence of the IBD signal contrasts with the result of a recent meta-analysis on IBD patterns in bryophytes and suggests that Amazonian bryophyte species experience more dispersal limitations than species from other biomes. As a comparison, we showed that, within the same Amazonian environment, the spatial genetic structures observed in bryophytes are comparable to that of angiosperm species producing much larger seeds. While a significant IBD signal characterizes the genetic structure of the vast majority of the Amazonian bryophyte species investigated here, our results are not consistent with the idea that isolation-by-resistance (IBR) and IBE contributed to the observed spatial patterns of genetic variation. Nevertheless, a low (0.059) but significant (P=0.004) Fst was found between sympatric specimens of the sibling Syrrhopodon annotinus and S. simmondsii, and their average kinship coefficients along a geographic gradient were consistently higher for conspecific comparisons than for interspecific comparisons, pointing to reproductive isolation between those two sympatric species characterized by different habitat requirements. Even if this single empirical result does not challenge the global idea that IBE does not prevail in extant patterns of genetic diversification in Amazonian bryophytes, it nonetheless contributes to growing evidence for genetic divergence observed along environmental gradients, suggesting that adaptation could play a more important role in shaping genetic patterns than previously thought. Rejection of the hypothesis that high dispersal capacities of bryophytes erased any historical signal in the extant spatial patterns of genetic structure and diversity of their populations and, in particular rejection of the inverse isolation hypothesis, indicate that the data generated in the present thesis are suitable for demographic inference. We applied coalescence-based approaches to infer the post-glacial history of bryophyte populations from contrasting environments characterized by the presence (Europe) or the absence (Amazonia, ongoing study) of apparent geographic barriers to migration. In Europe, our analyses revealed that the post-glacial assembly of bryophytes likely involved a complex history. Extant European populations originated from multiple sources with a contribution from allochthonous migrants representing 90-100% in about half of the 15 investigated species, which demonstrates the importance of LDD for the post-glacial recolonization of Europe by bryophytes and is unparalleled in any previous phylogeograhic study on other organisms. [less ▲]

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See detailValorisation des gisements argileux pour la fabrication des blocs de terre comprimée
Mango-Itulamya, Lavie Arsène ULiege

Doctoral thesis (2019)

Le matériau « terre » représente une ressource naturelle répandue dans les sols et les formations sédimentaires superficielles. Il constitue une alternative pour construire des logements durables à faible ... [more ▼]

Le matériau « terre » représente une ressource naturelle répandue dans les sols et les formations sédimentaires superficielles. Il constitue une alternative pour construire des logements durables à faible coût environnemental et pour les pays en développement à faible coût économique à condition de sélectionner des terres adéquates et/ou prétraiter des terres inadéquates. Cette thèse apporte une contribution sur la production des matériaux de construction économiques et écologiques pour d’une part répondre aux défis de logement dans les régions de Kinshasa et du Kongo Central et d’autre part promouvoir le développement des matériaux en terre crue en Belgique. La thèse comporte deux objectifs spécifiques. Le premier objectif spécifique consiste à évaluer l’aptitude des formations argileuses superficielles pour la conception des Blocs de Terre Comprimée (BTC). Le second objectif vise à augmenter la durée de vie de ces blocs. Le matériel argileux étudié (167 échantillons) a été prélevé dans 62 sites répartis dans 21 formations et membres argileux en Belgique et en RDC. Ces échantillons ont été caractérisés par la mesure de paramètres minéralogiques (minéralogie totale et fraction argileuse), chimiques (éléments majeurs) et géotechniques (granulométrie, limites de consistance, perte au feu, retrait longitudinal de séchage et nature), principaux tests pour sélectionner les terres propices à la construction en BTC. Les résultats de ces tests ont montré que ces échantillons peuvent être utilisés, moyennant ou non des prétraitements, dans la construction en BTC. Des échantillons représentatifs ont été sélectionnés pour étudier cinq paramètres affectant la durée de vie des BTC. L’influence de la nature des minéraux argileux a été étudiée en utilisant 5 formations argileuses de composition minéralogique différente. L’influence de la taille des particules a été testée en ajoutant 3 types de granulats de dimensions différentes (i.e., 0/2, 0/4 et 0/6,3 mm). L’influence de la pression de mise en forme a été évaluée en compactant les BTC avec 3 pressions (i.e., 100, 200 et 300 kN). L’influence de la quantité d’eau a été évaluée en ajoutant de 3 à 10 % d’eau. L’influence de la stabilisation a été faite en ajoutant, en différentes proportions, soit des substances minérales (granulat rocheux, sable alluvionnaire), soit des déchets agricoles bruts (bagasse de canne à sucre) ou prétraités (cendre issue de la combustion de la bagasse). Des BTC et des éprouvettes ont été produits et caractérisés par leur retrait de séchage, leur résistance à l’abrasion, leur résistance à la compression et à la flexion, les essais d’absorption d’eau par capillarité, d’immersion complète, d’égouttement accéléré et enfin de gel-dégel. La caractérisation des BTC et éprouvettes montre que les résistances à l’absorption d’eau par capillarité, à l’égouttement accéléré et au gel-dégel augmentent avec le pourcentage du stabilisant granulat ajouté. Les résistances à la compression, à la flexion et à l’abrasion n’augmentent pas avec l’ajout de stabilisant pour toute formation argileuse. La résistance à l’immersion complète diminue avec l’ajout de granulat. L’ajout des différents stabilisants réduit le retrait dû au séchage. L’ajout de fibre augmente la résistance à la flexion. La résistance à la compression diminue avec la quantité d’eau ajoutée. L’augmentation de la pression de mise en forme permet d’augmenter la résistance en compression. Cette étude démontre que les gisements argileux sélectionnés permettent de produire des BTC à faibles coûts environnemental. En Belgique, les formations argileuses testées permettent de produire des BTC avec une bonne performance mécanique, pouvant être utilisés à l’intérieur ou à l’extérieur du bâtiment. En RDC, ces matériaux de construction répondent à des normes de résistance à la détérioration et sont compatibles avec les cultures constructives locales. De plus, ces matériaux représentent une alternative économique pour les pays en développement comme la RDC. [less ▲]

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See detailDéveloppement de l’information électronique et Open Access en Géographie Mise en perspective des performances des outils bibliographiques avec l’usage et la diffusion de la littérature scientifique
Stirbu, Simona ULiege

Doctoral thesis (2019)

In scientific research, the development of digital media has revolutionized the documentary landscape. The objective of our work was to identify the influence of the development of electronic scientific ... [more ▼]

In scientific research, the development of digital media has revolutionized the documentary landscape. The objective of our work was to identify the influence of the development of electronic scientific information and Open Access on the use and dissemination of scientific publications in Geography. Our doctoral dissertation is organized around two main matters: on the one hand, bibliographic research tools and their coverage that influence the use of documents, and on the other hand, the dissemination and visibility of the results returned by these bibliographic research tools. Different methodological approaches have been adopted and the results are presented in two parts and five chapters. In a difficult financial context, linked to the permanent rise in journal prices and to increasingly restrictive editorial policies, the question of the effectiveness of commercial bibliographic databases (such as WoS, Scopus, GeoRef) against the "free" search engine GS, has been the subject of many publications. However, as far as geography is concerned, there is little data available on the effectiveness of GS as a bibliographic research tool and means of dissemination of scientific publications. In our work, as much for keyword searches, as for its coverage in theses bibliographies or for its coverage in a selection of publications from ULiege geographers, the results numerically place GS largely at the top of the list of the bibliographic tools analyzed. The search engine finds many references, whether in Physical Geography or Human Geography. Generally, GS completely covers the contents of the other studied databases, with some exceptions for GeoRef, a tool that is specialized in Physical Geography. Regarding the visibility of the scientific literature produced by the geographers of ULiège, we have noted an excellent performance of GS, followed by Scopus, WoS and GeoRef. The role of the ORBi institutional repository in the visibility of the ULiège publications via GS was questioned. The references are all visible and accessible to researchers via GS thanks to ORBi’s harvesting, even if the performance of GS would in any case be greater than that of the databases without the contribution of ORBi. The cartographic representation of downloads made from ORBi and a statistical approach to data allowed us to conclude that the language of references, the location of countries on the different continents, as well as the membership of the countries that make the downloads to the French-speaking community positively influence the number of downloads. Developed French-speaking countries as well as those in the process of development are the largest users of these publications, of which a large percentage is French-written. In conclusion, bearing in mind the fact that GS is only apparently "free" and that there are economic and social implications to its use, our results allow us to argue that the search engine can be a solid alternative to classical commercial databases in Geography. Furthermore, the development of digital media offers the academic world the opportunity to regain, at least in part, the dissemination of research results. Thus, making available the publications in institutional repositories, which are part of the Open Access movement, improves their distribution regardless of the type of document or language of publication. [less ▲]

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See detailIngestion of Ionospheric Scintillation Skymaps into GNSS Algorithms
Lonchay, Matthieu ULiege

Doctoral thesis (2019)

Nowadays, Global Navigation Satellite Systems (GNSSs) play a significant role in our modern society as they support a wide range of applications worldwide associated with utterly demanding performance ... [more ▼]

Nowadays, Global Navigation Satellite Systems (GNSSs) play a significant role in our modern society as they support a wide range of applications worldwide associated with utterly demanding performance requirements. However, GNSS performances in terms of accuracy, continuity and reliability are limited by the Earth’s ionosphere. In particular, small-scale irregularities and inhomogeneities in the ionospheric free-electron density are responsible for diffraction and scattering effects on GNSS signals that propagate through such ionospheric disturbances. These effects result in rapid fluctuations of the amplitude and phase of GNSS signals, also known as ionospheric scintillations, which can severely disrupt the performances of GNSS navigation and positioning algorithms. The ultimate objective of this PhD thesis consists in prototyping mitigation strategies in order to improve the accuracy, continuity and reliability performances of GNSS algorithms in case of low-latitude ionospheric scintillations. In particular, this research targets two specific Single-Point Single-Epoch (SPSE) GNSS algorithms, namely the Standard Point Positioning (SPP) and the Precise Point Positioning (PPP) algorithms. The mitigation strategies prototyped in the framework of this research are based on ionospheric scintillation skymaps resulting from the application of specific spatial analysis techniques on ionospheric scintillation measurements. Specifically, these prototype mitigation strategies target the stochastic modelling and the integrity monitoring stages of the SPP and PPP algorithms. First, this PhD thesis presents a statistical analysis based on measurements performed by a network of Ionospheric Scintillation Monitoring Receivers (ISMRs) located near the magnetic equator in Brazil and collected during the year 2014, i.e. during the (second) peak of the last solar maximum (solar cycle 24). This statistical analysis leads to the conclusion that high-end GNSS receivers operating in low-latitude regions can see their positioning performances affected by ionospheric scintillations during about 20%–30% of the time in case of active ionospheric conditions. The addition of detrimental effects due to signal fading, cycle slips and losses of signal lock results in poor positioning performances in terms of accuracy, continuity and reliability during moderate-to-intense ionospheric scintillation events. As the performances of the PPP algorithm rely on the precision of carrier phase measurements, the PPP algorithm is more sensitive to ionospheric scintillations than the SPP algorithm, which is based on code pseudorange measurements exclusively. In case of active ionospheric scintillation conditions, the Root-Mean-Square Error (RMSE) of the tridimensional PPP solution can be as high as 6.73 m and its success rate as low as 50% by comparison to 0.18 m and about 100%, respectively, during quiescent conditions. Then, this PhD thesis focusses on the spatiotemporal characteristics of ionospheric scintillations by exploiting spatial analysis techniques applied to scintillation measurements collected through the experimental ISMR network located in Brazil. Spatial analysis techniques consider densified ionospheric scintillation skyplots composed of Ionospheric Pierce Points (IPPs) as spatial samples whose geometric and attribute components evolve over time as satellites are orbiting the Earth and as ionospheric conditions change. This approach turns out to be successful in detecting, scaling and tracking significantly positive spatial autocorrelation in ionospheric scintillation skyplots during active ionospheric conditions. The spatial analysis techniques exploited in the framework of this research eventually led to the design of three types of real-time ionospheric scintillation skymaps that quantify the spatiotemporal characteristics of low-latitude ionospheric scintillations. Finally, this PhD thesis describes the design and benchmarks the performances of several categories of prototype mitigation strategies against ionospheric scintillations that target the stochastic modelling and the integrity monitoring stages of the SPP and PPP algorithms. The design of the strategies is based on several types of ionospheric scintillation skymaps and the benchmark of their performances relies on the definition of several specific performance parameters. Globally, all the prototype mitigation strategies designed in the framework of this PhD thesis contribute to increase the accuracy, continuity and reliability performances of the SPP and PPP algorithms during low-to-moderate ionospheric scintillations. Strategies associated with ionospheric scintillation skymaps based on local spatial autocorrelation statistics outperform strategies based on interpolated skymaps. Strategies related to the weighting scheme of the stochastic model provide better results for the SPP algorithm than the PPP algorithm whose performances are further enhanced by strategies implementing spatial masks. Prototype mitigation strategies tuning the integrity monitoring stage of the SPP and PPP algorithms increase significantly the continuity and reliability performances of the algorithms but at the expense of a heavier computational load. Best performances for the SPP and PPP algorithms in terms of reliability are obtained by hybrid strategies targeting both the stochastic modelling and the integrity monitoring stages of the algorithms. [less ▲]

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See detailDevelopment of complementary methods for the detection of animal by-products in feedingstuffs
Lecrenier, Marie-Caroline ULiege

Doctoral thesis (2019)

Since the mid-1980s, several transmissible spongiform encephalopathies have been reported in humans and animals. Bovine spongiform encephalopathy was first identified in cattle in 1986 and, in subsequent ... [more ▼]

Since the mid-1980s, several transmissible spongiform encephalopathies have been reported in humans and animals. Bovine spongiform encephalopathy was first identified in cattle in 1986 and, in subsequent years in other animal species. Consumption by cattle of meat and bone meal containing carcasses of infected animals was incriminated. The use of such animal by-products was first banned in feed for ruminants and then, with few exceptions such as the use of fish meal for non-ruminants, extended to all feeds for farmed animal. Thanks to prevention and control efforts, a gradual lifting of the feed ban is now possible. The reintroduction of non-ruminant processed animal proteins into the feed of aquaculture animals was adopted in 2013. In this context of dynamic relaxation of the ban, the challenge remains the development of complementary methods or the adaptation of official methods aimed at refining the identification of feed materials. Indeed, the combination of light microscopy and PCR does not differentiate among certain animal by-products and this can make the results uninterpretable. This PhD thesis focused on (1) the evaluation of current legislation and available methods of analysis for the detection of animal proteins; (2) the development of a fluorescence in situ hybridisation method combining the advantages of microscopy (localisation and identification of type of tissues) and molecular biology techniques (identification of the species by DNA); (3) the identification of specific peptides from blood products by high resolution mass spectrometry and (4) the development of a sensitive and routinely applicable tandem mass spectrometry method paving a new way to the detection of processed animal proteins. The results obtained allowed to (1) highlight current and foreseen analytical gaps as part of the feed ban relaxation dynamics; (2) propose a method for a specific detection of processed bone particles of ruminant origin independently of contamination by other by-products such as milk powder; (3) identify 9 biomarker peptides of plasma powder of bovine origin and 7 biomarker peptides of bovine haemoglobin powder, 6 of which also allow the detection of blood meal of bovine origin and (4) develop a UHPLC MS/MS multi-target method allowing the simultaneous detection of several by-products of ruminant origin (blood meal, blood products and dairy products) at a limit of detection (LOD) of 0.1% (w/w). Finally, new analytical schemes incorporating the results of this thesis as well as potential sources of improvement for future analytical developments have been proposed. [less ▲]

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See detailDéveloppement et optimisation d'une méthode MALDI-MS/MS pour l'identification de cyanotoxines
Deleuze, Christelle ULiege

Doctoral thesis (2019)

Water quality monitoring is an area where miniaturization and speed are key parameters to facilitate portability. In the case of recreational water analysis, ELISA is the most widely used method, and ... [more ▼]

Water quality monitoring is an area where miniaturization and speed are key parameters to facilitate portability. In the case of recreational water analysis, ELISA is the most widely used method, and analysis can be performed directly in the field thanks to commercially available kits. This method is robust and sensitive but suffers from a lack of specificity. Indeed, ELISA generally targets only one particular compound or family without distinction between potentially more or less toxic variants. Cyanobacteria are one of the world's earliest groups of living organisms. If their presence is natural in waterbodies such as lakes or rivers, their abnormally important development under certain conditions is problematic. Indeed, during cell lysis, a very large quantity of toxins can disperse quickly, with potentially dazzling effects such as paralysis followed by the death of the victim in the case of ingestion of saxitoxin, for example. One of the most widespread cyanotoxines, for which the World Health Organization (WHO) has set a limit of 1 µg/L, is microcystin LR (MC-LR). To date, more than 200 variants of microcystins and other cyanotoxins, of variable toxicity, have been identified. It is therefore essential to include them in recreational water quality monitoring in order to prevent risks as much as possible. This PhD has been started in that context, with the main goal being to develop new approaches for the analysis and identification of cyanotoxins. When the identification of the composition of a sample is a must, mass spectrometry (MS) is usually the reference method. In order to improve quantification limits, mass spectrometry is used either at high resolution and/or in "tandem or MS/MS" mode. The mixtures to be analyzed being complex, to avoid interferences, Pigh-Performance Liquid Chromatography (HPLC) separation was developed upfront mass spectrometry analysis. When a separation technique is coupled with mass spectrometry, it can drive the choice of ion production technology. Electrospray ionization (ESI) was the method of choice. However, another source that grew up in parallel with electrospray ionization, Matrix Assisted Laser Desorption/Ionisation (MALDI) can now be considered in with liquid chromatography separation. The eluent of the HPLC column is dropped onto the consecutive spots of a MALDI analysis plate. This LC MALDI coupling offers interesting performances compared to the HPLC ESI, especially in terms of optimal use of the sample. It is indeed deposited in its entirety on a solid support and is consumed only during LASER shots. The chromatography is somehow stored on the solid support and the analysis can be renewed later. The final objective of this project is the development of a method for the identification and analysis of cyanotoxins by mass spectrometry coupled to HPLC separation, and more particularly HPLC MALDI MS/MS. The choice of the MALDI matrix allowing the detection of a maximum of cyanotoxins was made on the basis of an exhaustive review of the literature. The major obstacle of this part of the work was to assess the proposed solutions allowing for the detection of these toxins without interfering in the mass spectrum. The classical MALDI matrices have been evaluated and compared with the alternatives proposed by the scientific community at the beginning of this work (2006). Thus, the 2,5 DHB, HCCA and sinapinic acid matrices, in particular, were tested and compared with alternative matrices such as the DIOS (Desorption/Ionization on Silicon) system, the liquid ion matrices, the porphyrin matrices, titanium dioxide inorganic matrices and graphite carbon from pencil mines, which practical interest is obvious. In the second part, the reductive properties of the 1,5 DAN matrix were exploited and have allowed the development of a characterization tool for microcystins. This reducing matrix, via the reduction of the C = C double bond of certain microcystins, made possible the classification of microcystins and the discrimination between the amino acids Dhb, Dha and Ser /Ala present in position 7 of the microcystin cycle. Once the HPLC separation step was developed, we performed the HPLC MALDI coupling via a robotic system in order to start the last part of this work, which is devoted to the analysis of environmental samples and identification of microcystins by HPLC MS/MS by exploiting MALDI and ESI sources, high resolution Orbitrap analyzer and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT ICR-MS). [less ▲]

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See detailBande à part ou quête d'appartenance ? Une anthropologie de la condition des jeunes Noirs à Liège
Collin, Jonathan ULiege

Doctoral thesis (2019)

Based on fieldwork carried out over a period of nearly four years, this doctoral thesis investigates the condition of young Blacks in the urban region of Liège (French-speaking Belgium). Following a socio ... [more ▼]

Based on fieldwork carried out over a period of nearly four years, this doctoral thesis investigates the condition of young Blacks in the urban region of Liège (French-speaking Belgium). Following a socio-historical contextualization of the sub-Saharan African presence in Belgium and a discussion of the notion of the “black condition”, the research draws on interactionist theories – most notably Erving Goffman’s work – as well as on current research into interethnic relations, socialization and recognition to analyze field materials. In addition to emphasizing the presence of discriminations, the analysis also brings to light the existence of a second, separate phenomenon: difficult face-to-face ethno-racial interactions. The research then highlights the substantial face work which black individuals make use of in such interactions, and the adaptation mechanisms they resort to in an effort to preserve civility in mixed daily contacts and encounters. Two resources are more closely examined, through which individuals attempt to cope with interactional difficulties in the longer term: krumping, an urban dance fostering interactional citizenship among practitioners, and youth gangs, which enable their members to seek more of an interactional recognition through withdrawal into a protective and awe-inspiring peer-group. [less ▲]

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See detailHolomorphic Cohomological Convolution, Enhanced Laplace Transform and Applications
Dubussy, Christophe ULiege

Doctoral thesis (2019)

The Hadamard product of power series has been studied for more than one hundred years and has become a classical tool in complex analysis. Nonetheless, this product only concerns functions which are ... [more ▼]

The Hadamard product of power series has been studied for more than one hundred years and has become a classical tool in complex analysis. Nonetheless, this product only concerns functions which are holomorphic near the origin. In 2009, T. Pohlen studied an extension of this Hadamard product on functions defined on open subsets of the Riemann sphere, which do not necessarily contain the origin. Using ad-hoc and explicit constructions, he could define this product thanks to a contour integration formula. However, his construction is non-symmetric with respect to 0 and the infinity. The first part of this thesis consists in the study of a generalization of Pohlen's extended Hadamard product. Using singular homology theory, we introduce more symmetric cycles and define a generalized Hadamard product which is equivalent to Pohlen's product when the functions vanish at infinity. Then, we show that this generalized Hadamard product is a particular case of a more general phenomenon called "holomorphic cohomological convolution". We study this convolution in detail on the multiplicative complex Lie group C^* and provide a contour integration formula to compute it. The second part of the thesis is devoted to the study of holomorphic Paley-Wiener type theorems due to Polya (in the compact case) and to Méril (in the non-compact case). These theorems use a contour integration version of the Laplace transform. Thanks to the theory of enhanced subanalytic sheaves developed by A. D'Agnolo and M. Kashiwara as well as the enhanced Laplace transform introduced by M. Kashiwara and P. Schapira, we show that such theorems can be understood from a cohomological point of view. Under some convex subanalytic conditions, we are even able to provide stronger Laplace isomorphisms between spaces which are described by tempered growth conditions. It appears that these spaces can be linked to certain spaces of analytic functionals. In the non-compact case, we define a convolution product between analytic functionals and conjecture that it is compatible with the additive version of the previously studied holomorphic cohomological convolution. Thanks to our results on the enhanced Laplace transform, we prove the conjecture in the subanalytic case. [less ▲]

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See detailEtude des risques naturels liés aux interactions entre les mouvements de masse et le réseau hydrographique dans la région des lacs Kivu et Tanganyika
Nibigira, Léonidas ULiege

Doctoral thesis (2019)

This PhD thesis is entitled ‘Etude des risques naturels liés aux interactions entre les mouvements de masse et le réseau hydrographique dans la région des Lacs Kivu et Tanganyika ’ (in English : ‘Analysis ... [more ▼]

This PhD thesis is entitled ‘Etude des risques naturels liés aux interactions entre les mouvements de masse et le réseau hydrographique dans la région des Lacs Kivu et Tanganyika ’ (in English : ‘Analysis of natural hazards related to the interactions between mass movements and the hydrographic network in the Lake Kivu and Lake Tanganyika regions’). The study area belongs to the East African Rift Valley. It is also located in a typically tropical climatic environment. Thus, it is regularly affected by landslides and recurring floods. Flood and landslide issues are often analysed separately while there are many cases of disasters where those types of hazards interacted; this is particularly true for the target region. Therefore, this thesis is focused on the interactions between those two types of natural hazards in order to provide clues to better assess them together. More specifically, this work will provide an inventory of the hydrological and geological hazards, will investigate cases experienced in the region, will highlight the level of exposure to direct and / or indirect impacts of landslides and will finally produce a related assessment. A methodology coupling field observations and measurements as well as laboratory analyses was developed. Laboratory studies were supported by remote sensing and numerical models to study slope stability as well as the triggering and evolution of landslides. Hydraulic simulations involving dam failure scenarios were run to assess related effects on floods in the downstream area. Important decision-support tools in the environmental and land management, urban and hydroelectric plant planning have been developed. They consist of maps illustrating the relative territory and hydrographic network susceptibilities to floods and landslides. Moreover, the configuration of the interplay mechanisms between landslides and floods is designed and discussed. These results make a valuable contribution to the understanding of geological and hydrological hazards in the Lake Kivu and Lake Tanganyika regions. They are also an important asset for further studies in this field and can be used for other zones located in a similar natural hazard context. [less ▲]

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See detailGroundwater and contaminant mass fluxes monitoring in heterogeneous aquifers
Jamin, Pierre ULiege

Doctoral thesis (2019)

Groundwater is one of the most important natural resources of our planet and it requires appropriate management and protection in order to guarantee its availability for future generations. From a water ... [more ▼]

Groundwater is one of the most important natural resources of our planet and it requires appropriate management and protection in order to guarantee its availability for future generations. From a water quality point of view, old industrial activities and modern accidental releases have locally impacted groundwater resource. Management of these contaminated aquifers has historically relied on comparison between measured contaminant concentrations in groundwater and threshold values. This approach is a necessary early characterization step but is totally insufficient to fully investigate the contaminants behavior in groundwater and to quantify the associated risks. Since the beginning of the years 2000, a consensus has been growing among the scientific, technical and decision makers’ community on the fact that management of contaminated aquifers should be performed in terms of contaminant flux metrics. Accordingly, it has become necessary to dispose of techniques able to accurately measure mass fluxes and mass discharges of contaminants in aquifers. Contaminant mass flux usually relies on measurements of both groundwater flux and contaminant concentration in monitoring wells drilled in the aquifer of concern. Research efforts must lead to the proposition of new solutions, methodologies and techniques, in particular for measuring groundwater fluxes. In this work, the Finite Volume Point Dilution Method (FVPDM), is proposed as an innovative single-well method for monitoring groundwater fluxes in aquifers. Mathematical basis and a first analytical solutions allowing to interpret FVPDM experiments performed in steady state groundwater flow conditions were already developed and validated on a few field applications. In this research, a generalized FVPDM interpretation framework for monitoring groundwater fluxes over time is proposed, based on a new finite difference expression proposed to calculate groundwater fluxes from FVPDM experiments performed in transient groundwater flow fields. In a first step, the FVPDM technique was successively applied in various laboratory and field experiments allowing to define its accuracy, precision and resolution under transient groundwater flow conditions. A first lab-scale flow tank experiment demonstrated the accuracy of the FVPDM for groundwater fluxes measurements in both steady and transient state flow conditions. Difference between the prescribed water flux in the flow tank and the measured water flux using FVPDM was as low as 0.15 %. In a second experiment the FVPDM was applied to measure groundwater fluxes on several fractured zones of an open well installed in a crystalline rock aquifer. This constitutes the first successful application of the FVPDM technique in a fractured aquifer, using straddle packers. The classical point dilution method (PDM) was also applied during this experiment, under the same groundwater flow conditions to compare the sensitivity and uncertainty of both methods. It demonstrated that FVPDM generally provides a better precision than PDM but it may require longer experimental durations. A third FVPDM experiment undertaken in an alluvial aquifer allowed to validate in the field the method for monitoring rapidly changing groundwater fluxes. This first series of experiment allowed to validate the FVPDM as a fully operational method for measurements of groundwater fluxes for a wide spectrum of experimental and flow conditions. In a second step, three field-scale applications of the method were performed. The first relates to direct groundwater fluxes measurements in a sub-permafrost aquifer located in the remote territories of northern Quebec. These measurements came in support to a thermo-hydrodynamic model of a watershed where permafrost thaw occurs. This specific application demonstrated the robustness and versatility of the FVPDM. In a second field application, the FVPDM was used to monitor, under controlled conditions a solute mass discharge experiment undertaken in a heterogeneous alluvial aquifer at a series of control planes in order to compare different methods for calculating the total mass discharge based on discrete groundwater fluxes and concentration measurements. In a third application, the FVPDM was successfully used in a groundwater pollution investigation to characterize highly transient groundwater flows and pollutant mass fluxes within a coastal aquifer influenced by marked tides. The results of this experiment allowed to improve and refine the conceptual site model and provided crucial information for optimizing further investigations and risk mitigation measures at this polluted site. The FVPDM was applied in a wide range of environmental contexts, of application scales, of experimental setups, of aquifer types, of time scales, of groundwater flow conditions, and for both research and consultant-type purposes. The FVPDM was proven to be a robust and versatile method that provides high-quality reliable groundwater flux data for general hydrogeological characterizations and for contaminant mass fluxes monitoring, even under highly transient flow conditions. From a more general perspective, this research demonstrated the great importance and the huge benefits of having direct and reliable in situ measurements of groundwater fluxes for any kind of hydrogeological studies. This research proves once more the value of undertaking mass flux measurements for characterization of contaminated sites, risk assessment and design of risk mitigation measures. [less ▲]

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See detailNew Methods for Signal Analysis: Multifractal Formalisms based on Profiles. From Theory to Practice.
Kleyntssens, Thomas ULiege

Doctoral thesis (2019)

The multifractal formalisms allow to numerically approximate the Hölder spectrum of a real-life signal f. In this thesis, we study some multifractal formalisms based on profiles: these are functions ... [more ▼]

The multifractal formalisms allow to numerically approximate the Hölder spectrum of a real-life signal f. In this thesis, we study some multifractal formalisms based on profiles: these are functions allowing to study the histograms of coefficients obtained by the wavelet transform of f. The profile-based formalisms studied here are the Wavelet Profile Method (WPM) and the Leaders Profile Method (LPM). An advantage of these methods, compared to those that use a Legendre transform on a structure function, as for example the Wavelet Leaders Method (WLM), lies in the fact that they are able to approximate non-concave spectra. The contributions on a practical level are directly related to the profile-based methods. An efficient algorithm for these methods is proposed. It is applied and compared with the WLM on classical examples, as the fractional Brownian motion, the Lévy process and the Mandelbrot cascades, as well as on processes with prescribed pointwise regularity. A new method to distinguish the mono- and multifractality of a signal is also proposed. We apply these methods on a practical example: the Mars' topography. We show that the simultaneous use of the WLM and the LPM allows to obtain additional information on the nature of signals. We also show that it is possible to detect major surface features of Mars in the spatial distribution of the Hölder exponents. The contributions on a theoretical level can be divided into two parts. For the first one, let us recall that the amplitudes of the wavelet leaders of a signal have not necessarily the same asymptotic pointwise Hölderian behaviour: a logarithmic correction can appear. We prove that the three well-known Hölderian behaviours of the Brownian motion (known as ordinary, rapid and slow) are also present in the behaviour of the amplitudes of its wavelet leaders. The proof provides a new way to study fine properties of stochastic processes. We also construct a multifractal process that has a local regularity similar to that of the Brownian motion. The second part of these contributions is a generalisation of the Snu spaces with the help of the admissible sequences. The topological properties holding for the usual Snu spaces are preserved. The robustness of these new spaces is also presented, which implies the independence of the chosen wavelet basis. Finally a link with the generalised Besov spaces is given. [less ▲]

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See detailLes conditions d'applications des normes IPSAS au Maroc en comparaison avec la Belgique
Idrissi Chouahdi, Amina ULiege

Doctoral thesis (2019)

As regards public administration, Moroccowasrefractory a long time with the idea of change. It wasnecessarydecadesbefore the concept of public management take sit place and thatitisrecognizedlike capital ... [more ▼]

As regards public administration, Moroccowasrefractory a long time with the idea of change. It wasnecessarydecadesbefore the concept of public management take sit place and thatitisrecognizedlike capital in the strategy of the State. Up to that point, the idea of public administration hadremained an opaque, dubious and voluntarily vague concept in order to more sit the seizure and the control of Makhzen. The administration of the country wasmarked by the absence of an accounting transparent, reliable, wasstandardized and rational whatdid not easilyapplied to the principles of good governance and the installation of a public management optimized and really effective. As regards public accounting, one attends since 2008 a truerevolution. That of the birth in Europe and in the world of standards IPSAS (International Public Sector Accounting Standards). These new international countable standards, primarily intended for the public sector and enacted by the IFAC (the International federation of the accountants), aim at improving the transparency, balance and the effectiveness while applying to the communities of the rules close to those of the companies and by unifying the methods between the organizations. Globalization and its many effects lead to more economic opening and a more marked liberalization of the trade. This situation which imposes transactions taking place except borders, between several States which often do not have the same financial culture, forces these same States to find a common language as regards financial information. In Morocco, standards IPSAS are still applied only in a very partial way. Our comparative study with Belgium, where the IPSAS are also in the course of application, should help us with better understanding which are the levers likely to facilitate their generalization. [less ▲]

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See detailDesign, synthesis, and properties of novel bio-based and ethylene-based copolymers
Scholten, Philip ULiege

Doctoral thesis (2019)

Renewable monomers have the potential to replace petroleum-derived monomers for reversible deactivation radical polymerisations (RDRP) for a variety of applications, such as adhesives and coatings. Yet ... [more ▼]

Renewable monomers have the potential to replace petroleum-derived monomers for reversible deactivation radical polymerisations (RDRP) for a variety of applications, such as adhesives and coatings. Yet, challenges in the polymerisation of non-activated and often internal double bonds found in natural molecules still remain. Moreover, functionalisation pathways attaching renewably-sourced double bonds to natural molecules are rare and sustainable strategies using catalytic or enzymatic reactions are sought after. This thesis aims to introduce a set of renewable monomers for reversible deactivation radical polymerisation (RDRP), namely organometallic-mediated radical polymerisation (OMRP) using a cobalt complex, in the quest for renewable and functional (co)polymers. This particular type of OMRP was chosen because it controls the polymerisation of a large range of non-activated monomers with excellent control over the chain growth process under mild experimental conditions. The monomers prepared in this thesis were obtained from plant oils and/or CO2 via catalytic reactions and contain ester and carbonate functionalities of interest for post-polymerisation modifications. Successful copolymerisations with monomers bearing non-activated double bonds, namely vinyl acetate and ethylene, were performed using OMRP under mild conditions and the comonomer content was tuned via the initial polymerisation feed or the ethylene working pressure. The introduction of carbonate moieties into vinyl acetate copolymers allowed for the synthesis of three discrete functional poly(vinyl alcohol) copolymers. Moreover, the ability to incorporate such carbonate functionalities into polyethylene copolymers by OMRP was shown for the first time. Highly linear ethylene copolymers over a broad range of carbonate content were obtained with significantly altered properties compared to homo-polyethylene. Particularly the ability to finely tune the molecular copolymer parameters, such as molecular weight and copolymer architecture, allows a systematic study of their influence on the compatibilisation capability of such copolymers. The potential of polyethylene copolymers bearing functional groups as compatibilisers was highlighted for poly(ethylene-co-vinyl acetate) copolymers. Finally, a fully renewable compatibiliser, based on starch and high oleic sunflower oil, obtained by non-radical means was applied to cellulose/LDPE composites. An improved cellulose dispersion within the matrix was observed by rheology, while the mechanical properties, notably Young’s modulus, was increased. This work aims to highlight the unexplored potential of renewable resources for the synthesis of functional polymers for their application in polyolefin composites. [less ▲]

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See detailOctarellinVII A new generation of de novo designed (β/α)8 -barrel proteins
Martina, Cristina ULiege

Doctoral thesis (2019)

De novo protein design is a growing field in protein chemistry, aiming at the production of artificial proteins. On a purely fundamental basis, the design of proteins from scratch allows testing the ... [more ▼]

De novo protein design is a growing field in protein chemistry, aiming at the production of artificial proteins. On a purely fundamental basis, the design of proteins from scratch allows testing the accuracy of the current protein knowledge and, possibly, to improve it. A deep knowledge of the sequence, structure, function relationships in proteins is necessary to design new proteins with specific functions. This facet of de novo protein design has numerous appli- cations in biotechnology and biomedicine. On the other hand, in the context of a post-genomic era, advanced computational methods for protein analysis, modelling and design are needed to decode the massive amount of genomic data. There is a long tradition at the University of Liège in the design of artificial (β/α) 8 -barrel proteins, called Octarellins. This fold, also known as TIM-barrel, is widespread in nature, partic- ularly in enzymes, and represents an interesting target for therapeutic or biological applications. Several generations of Octarellins were designed with the help of very different approaches. Lessons from these previous works has served as a rational basis for this study, which consists in the design of a new generation of artificial TIM-barrels, termed OctaVII. This thesis is divided in four sections that are shortly described hereafter: The first section describes a pool of natural TIM-barrels, which structural features were analyzed in order to extract useful information for the following steps of design and validation. The second section is dedicated to the design of OctaVII models. Backbone structures were designed with the use of the modelling software Rosetta and Modeller. This led to the selection of 28 backbones structures, which were used for the design of sequences, using Rosetta. Finally, more than 8000 artificial sequences were designed. The third section includes the in silico validation of the design. Information obtained from natural TIM-barrels was used to screen the 8000 artificial sequences and to select 10 of them for experimental characterization. Various structural features were tested, including hydrogen bond content and amino acid composition, and both secondary structure predictions and molecular dynamic simulations were performed. The fourth section is dedicated to the experimental validation of the design through pro- tein expression, purification and biophysical characterization. In addition to the ten original sequences that were designed in this work, five additional variants were tested for their possibly improved properties (collaborations at the Vrije Universiteit Brussel, Belgium, and at the Van- derbilt University, USA). This thesis contributes to the development of the de novo design of proteins as an emerging methodology for both a better understanding of proteins and the design of new functional proteins with applications in biomedicine and nanotechnology. [less ▲]

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See detailTranscriptomic and epigenomic analysis of endodermal and pancreatic progenitor cells in Danio rerio
Lopez Pérez, Ana Rosa ULiege

Doctoral thesis (2019)

The pancreas is developing from the endodermal germ layer. Differential analysis of gene expression and open regions of the chromatin between endodermal and non-endodermal cells, through RNA-seq and ATAC ... [more ▼]

The pancreas is developing from the endodermal germ layer. Differential analysis of gene expression and open regions of the chromatin between endodermal and non-endodermal cells, through RNA-seq and ATAC-seq, highlighted 820 genes with enriched expression in endoderm and 10601 regions of the chromatin specifically open in these cells. We found that half of the genes enriched in endoderm are located around at least one of these specific open chromatin regions; moreover, motif enrichment analysis showed that these regions are enriched in binding sites corresponding to endodermal specific transcription factors, such as Gata, Sox, and Forkhead. Furthermore, it is known that Retinoic Acid (RA) is required during gastrulation for the proper anterior-posterior regionalization of the embryo and for pancreas specification in vertebrates, however, the mechanisms by which RA induces pancreas in the endoderm are poorly understood. In this study, we identified the genes regulated by RA through RNA-seq. From the 371 genes up-regulated by RA, 26 of them were also down-regulated by BMS493 (an antagonist of RA). Besides, 94 of these up-regulated genes have RA receptor (RAR) binding sites, found by ChIP-seq analysis using a Myc-tagged RAR protein, around their transcription starting site (TSS), suggesting that RA might directly regulate them. Among these 94 genes, we found cyp26a1, cyp26b1 and dhrs3a, genes involved in the synthesis pathway of RA. Moreover, two known pancreatic markers, gata6 and hnf1ba, are also among these 94 genes, indicating that these two genes might act as mediators of RA to induce pancreas formation. Open chromatin analysis performed through ATAC-seq, showed that RA has also an effect on the chromatin structure, the motifs present in the regions of the chromatin induced by RA are enriched in RA response elements (RARE), and in binding sites for Gata6 and Hnf1b proteins. All these data together suggest that the RAR might act as pioneer factors modifying the chromatin structure and that gata6 and/or hnf1ba might be the key mediators of RA action to induce pancreas in the endoderm. Finally, transcriptomic analyses of the pancreatic progenitor cells from the ventral pancreas highlighted genes with enriched expression in these cells. In situ hybridization analysis for some of these genes showed specific expression of olfm4 in the pancreatic progenitor cells. Besides, nupr1, elf3 and cebpa showed an expression not only in the developing pancreas but also in other gut tissues. [less ▲]

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See detailOrganizing Strategic Decision: Decisional Work in New Ways of Working Projects
Jemine, Grégory ULiege

Doctoral thesis (2019)

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See detailAgroecological intensification of Integrated agriculture aquaculture systems: the case of smallholder farms in the western DRC
Mafwila Kinkela, Patrick ULiege

Doctoral thesis (2019)

In the Democratic Republic of Congo (DRC) as in other sub-Saharan African (SSA) countries, small farms face the problem of low yields. To meet the challenge of stably and sustainably increasing production ... [more ▼]

In the Democratic Republic of Congo (DRC) as in other sub-Saharan African (SSA) countries, small farms face the problem of low yields. To meet the challenge of stably and sustainably increasing production, some smallholders are turning to integrated agriculture aquaculture (IAA) production systems developed in South-East Asia. It is based on the exchange of nutrient flows between different subsystems among which fish ponds play a key role. It allows small farms to be less dependent on external resources, increasing profitability. However, the expected results are not yet visible in SSA. The objective of this thesis was to identify which levers can be used to optimize overall production at the farm level in the humid tropics in an African socio-economical context, using the periphery of Kinshasa as a case study. We hypothesized that the level of integration of flows determines the stability of IAA farms, focusing on nitrogen (N), both in terms of quantity and quality, as it is the major limiting factor in both terrestrial and aquatic production. A survey of 150 integrated agricultural farms in two peri-urban and one rural area of Kinshasa helped to understand how ponds are managed in the integrated systems. A subsequent monitoring of 11 integrated agriculture aquaculture farms for eighteen months with at least two visits per month helped to understand the functioning, the strengths and the weaknesses in the technical and economic organization of IAA farms. In order to quantify and propose a more efficient use of N flows, a mathematical model has been developed. Finally, experiments with locally available resources were carried out to improve efficient use of N flow from pig at the farm level; namely by adding an insect larvae production subsystem in the IAA farms. Results indicated that 79% of fish ponds in Kinshasa were located on farms integrating fish with livestock (mainly pigs) and/or vegetable farming. No striking difference in farm characteristics between urban and rural farms was denoted, except for fish feeding practices. IAA is generally applied in small farms with limited financial resources and some of them are unable to generate profits, although they all have a positive gross margin. Due to the lack of commercial feed for feeding fish, farm wastes and agro-industrial by-products are widely used as fish feed despite their low nutritional value, especially regarding the protein content and nutritive value of fish. At least eleven possible flows can be exploited with the three main subsystems, i.e. fish ponds, pigsties and vegetable beds, present on a farm with a relatively high use of pig manure as fertilizer for vegetable crops and as an indirect feed protein input through primary production in the fish food chain. The level of education and the involvement of the farm owner have proven to be crucial factors that can allow a better organization of the farm both technically and financially and take maximum advantage of the complementarity of flows between farm components. Losses of N due to poor management of some flows between components have been noted, especially during the harvesting and storage of pig manure which often requires additional labour. Nevertheless, a more appropriate management of N outflows from pigs, which were evaluated at 14gN/pig and 20gN/pig per day, for fecal and urinary forms respectively, by the mathematical model, can help farmers to reduce N losses. For instance, raising pigs above ponds has been shown to be much more effective in minimizing N flow losses and handling requirements due to the natural collection of both feces and urine, which is often difficult in rural and peri-urban pigsties. It also allows farmers to reduce pond density per are of pond in the farm. Feces can also be harvested and used effectively as a substrate for the production of insect larvae, in mixture with agro-industrial wastes. Indeed, feces contain not only N but also undigested proteins and bacteria. They can be used more efficiently to produce a protein source and lead to the design of a new IAA system. In this system the natural production of flies larvae, whose growth limiting factor is probably lysine, could be improved by mixing pig manure with brewers' grains as locally available substrates. The produced larvae with a good amino acid profile can then be used as a complement to fish feed. At the farm level, a prototype infrastructure for maggot production was built directly on the ponds and allowed intensive production, natural harvesting of maggot in the ponds and reduced requirements for handling the manure by the farmers. In conclusion, integrated agriculture aquaculture systems as applied in the humid tropics of the DRC are able to fulfill their promises of stabilizing production and turning farms profitable. This goal may be achieved if farmers apply a thoughtful strategy for labour management in the farm and get personally involved in the farm’s activities. Farmers need also to focus on reducing N losses through N flows management between subsystem in the farms. They can give particular attention to the pig density and the use of pig manure in the other subsystems. Finally farmers can use the solution proposed by the simulation model according to the available resources and its environment. [less ▲]

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See detailExtensions of the Pascal Triangle to Words, and Related Counting Problems
Stipulanti, Manon ULiege

Doctoral thesis (2019)

The Pascal triangle and the corresponding Sierpiński fractal are fairly well-studied mathematical objects, which both exhibit connections with many different scientific areas. The first is made of ... [more ▼]

The Pascal triangle and the corresponding Sierpiński fractal are fairly well-studied mathematical objects, which both exhibit connections with many different scientific areas. The first is made of binomial coefficients of integers that notably appear in combinatorics to tackle counting problems (for instance, they provide the number of possible ways to choose a given amount of elements from a set of elements). There exist multiple generalizations of those binomial coefficients. In this text, we focus on binomial coefficients of words, which count scattered subwords. The red thread of this thesis is precisely the combination of the Pascal triangle and binomial coefficients of words. The first part is dedicated to extensions of the Pascal triangle to various sets of words (languages) associated with different numeration systems. We transport the existing link between the Pascal triangle and the Sierpiński gasket to this wider setting. The second part is concerned with particular sequences extracted from generalized Pascal triangles. They count non-zeroes binomial coefficients on each row of a given Pascal-like triangle. We study their regularity and their automaticity with respect to different numeration systems. In the third and last part, we establish the asymptotics of the summatory functions of the sequences considered previously. The most important feature of this part might not necessarily be the result itself, but the underlying new method to achieve it. [less ▲]

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See detailRecherches en cours. Discours de savoir numériques et actualité scientifique dans les carnets de recherche de la plateforme Hypothèses
Mayeur, Ingrid ULiege

Doctoral thesis (2019)

Table des matières Introduction 13 Première partie : État des lieux 21 1. Des humanités (numériques) 23 1.1. Une tentative de définition 24 1.2. Des humanités, à quelle fin ? 28 1.2.1. Une valeur per se ... [more ▼]

Table des matières Introduction 13 Première partie : État des lieux 21 1. Des humanités (numériques) 23 1.1. Une tentative de définition 24 1.2. Des humanités, à quelle fin ? 28 1.2.1. Une valeur per se 28 1.2.2. Une utilité sociale plus ou moins directe 30 1.2.3. Une valeur de savoir critique 32 1.3. Humanités et numérique 33 1.3.1. Penser dans l’environnement numérique 34 1.3.2. Comment le numérique intervient sur les savoirs en humanités 36 1.3.3. Les digital humanities : avatars d’une transdiscipline 39 1.3.3.1. Une approche historique des humanités numériques 40 1.3.3.2. Ce que recouvrent les humanités numériques 41 1.3.3.3. Les difficultés d’une institutionnalisation 44 1.4. Humanités, temporalité, actualité 47 1.4.1. Auctorialité numérique 48 1.4.2. Statut et temporalité des savoirs 49 2. La circulation des savoirs au prisme de leur matérialité (1) : texte et discours numériques 53 2.1. Quelle matérialité pour les textes numériques ? 55 2.2 La circulation des savoirs dans l’environnement numérique 59 2.2.1. L’écrit porté à l’écran : les transformations de la culture écrite 60 2.2.2. Énonciation éditoriale des textes numériques et architextes informatisés 62 2.2.3. Le texte numérique produit par les médias informatisés 64 2.2.4. Les savoirs comme êtres culturels affectés par la trivialité 66 2.2.5. L’éditorialisation des savoirs 68 2.2.6. Esthétique du texte numérique 72 2.2.7. Des SIC aux sciences du langage 73 2.3. Le discours numérique dans les sciences du langage 75 2.4. Dispositifs médiatiques et actualité 82 3. La communication scientifique dans l’environnement numérique 87 3.1. Une mise en perspective historique 88 3.1.1. Une mutation inscrite dans une continuité 89 3.1.2. La communication scientifique directe 93 3.2. Infrastructures numériques de la communication scientifique 97 3.2.1. Plateforme ou portail ? 97 3.2.2. Modèles économiques et idéologies de la communication scientifique : de l’abonnement à l’accès ouvert 99 3.2.2.1. Accès ouvert et SHS : quelques éléments du débat français 101 3.2.2.2. Le mouvement des communs 103 3.2.2.3. Science citoyenne et citoyen-chercheur 105 3.3. Les formats de publication de la recherche 106 3.3.1. La forme revue, pionnière dans la diffusion des savoirs numériques 107 3.3.2. Le blogging scientifique 112 3.4. Actualité de la recherche et fonction critique 115 4. La circulation des savoirs au prisme de leur matérialité (2) : l’écrit scientifique 119 4.1. L’apport des SIC à l’étude de la médiation sociale et numérique de l’écrit scientifique 120 4.1.1. La médiation sociale des savoirs scientifiques 121 4.1.2. Nouvelles matérialités du discours scientifique 128 4.2. L’analyse du discours scientifique 132 4.2.1. L’apport de la sociologie des sciences : le discours comme révélateur des rapports de pouvoir dans le champ scientifique 132 4.2.2. L’analyse du discours scientifique : positionnements énonciatifs du chercheur 133 4.2.2.1. Effacement énonciatif et objectivité 134 4.2.2.2. Discours scientifique et doxa 136 4.2.2.3. Dimension argumentative des écrits de recherche et ethos du chercheur 137 4.2.2.4. Genre(s) du discours scientifique 139 4.2.2.5. Quel discours scientifique numérique ? 143 4.3. Le discours scientifique engagé dans la temporalité des dispositifs numériques 145 5. Élaboration d’une problématique 147 5.1. Humanités numériques, édition scientifique et circulation des savoirs : retour transversal sur l’état des lieux 148 5.1.1. Quelles pratiques de médiation scientifique ou de science citoyenne en SHS ? 149 5.1.2. Le lecteur attendu 150 5.1.3. Le discours comme opérateur de trivialité 153 5.1.4. Une poétique de la recherche en cours 154 5.2. Formulation de la question de recherche 156 5.3. Synthèse des hypothèses de travail 157 Intermède méthodologique 161 6. Orientation méthodologique et corpus de travail 163 6.1. Choix et délimitation d’un corpus 163 6.1.1. Hypothèses comme plateforme de blogging en SHS, intégrée au portail de science ouverte OpenEdition 163 6.1.2. Unités d’analyse 165 6.1.3. La page d’accueil de la plateforme : biais d’une sélection éditoriale 168 6.1.4. Bornes temporelles et ajustements possibles 170 6.1.5. Distance du chercheur à l’égard de son corpus 171 6.2. Méthode 172 6.2.1. L’approche qualitative 172 6.2.2. L’analyse du discours numérique comme boîte à outils : quelques mises au point 173 6.2.3. Le recours à l’exemple 176 6.2.4. Démarche analytique générale 178 6.2.4.1. Hypothèses comme dispositif médiatisant 179 6.2.4.2 Genres de la communication scientifique 180 6.2.4.3. Les gestes d’élaboration du savoir 181 6.2.4.4. La dimension argumentative des billets de recherche 182 Deuxième partie : Analyse du corpus 183 7. Hypothèses comme dispositif médiatisant 185 7.1. La page d’accueil d’Hypothèses comme lieu de circulation des textes : une étude de l’énonciation éditoriale 186 7.1.1. Architexte, rubriques, vignettes et billets à la Une 186 7.1.2. Principes de valorisation des billets en page d’accueil 192 7.1.3. Formes culturelles et modèles : une comparaison avec la page d’accueil de la plateforme Hastac 201 7.2. Éditorialisation des billets comme formes circulantes 208 7.2.1. La mise au catalogue : éditorialisation du carnet comme unité éditoriale 209 7.2.2. Carnets anthologiques 211 7.2.3. Remédiations dans des espaces externes 214 7.2.4. Le billet comme espace d’éditorialisation 217 7.3. Coexistence et concurrence des formats 218 7.3.1. Blog vs. carnet de recherche 219 7.3.2. Carnet de recherche vs. revue 221 7.4. Relire le Manifeste des Digital Humanities comme promesse communicationnelle d’OpenEdition 226 7.5. La construction d’une actualité de la recherche : Hypothèses dans le chronotope médiatique 231 7.5.1. Gnoséologie d’Hypothèses 233 7.5.2. Topiques d’une actualité de la recherche 235 7.5.2.1. L’actualité du chercheur 236 7.5.2.2. L’actualité d’un collectif 237 7.5.2.3. L’actualité d’un média de la recherche 239 7.5.2.4. L’actualité sociale au prisme de la recherche 241 8. Le blogging de recherche, genre du discours scientifique ? 245 8.1. Le blog, un hypergenre 246 8.1.1. Qu’entend-on par genre ? 247 8.1.2. Le blog comme genre de discours 248 8.1.3. Le billet, genre conversationnel et journalistique 253 8.1.4. La chronique, un genre voisin du billet 254 8.2. Autodésignations génériques 256 8.3. Remédiations 257 8.4. Scénographies du billet de recherche 262 8.4.1. Discours à énonciation objectivisée 263 8.4.2. Discours à énonciation subjectivisée : contagion des formats médiatiques 265 8.4.2.1. Chroniques de/pour la recherche 265 8.4.2.1.1. Sérialité des publications 267 8.4.2.1.2. Mise en intrigue de l’activité de recherche 268 8.4.2.1.3. Dimension conversationnelle des billets 270 8.4.2.2. Billets réflexifs 273 8.4.2.3. Entretiens 276 8.5. Commentaires 278 8.6. Le blog scientifique, un genre en construction 284 9. Les gestes d’élaboration du savoir dans les billets de recherche 289 9.1. Les gestes discursifs du savoir sur Hypothèses 290 9.1.1. Citer 292 9.1.1.1. Marqueurs (techno)linguistiques des citations dans les carnets de recherche 295 9.1.1.1.1. Technomots/URL 296 9.1.1.1.2. Cadres énonciatifs audio(-visuels) 297 9.1.1.1.3. Technographismes 298 9.1.1.2. Fonctions assumées par les citations dans les billets du corpus 299 9.1.1.2.1. Fonction argumentative : positionnement, actualisation, illustration, définition, autocitation 299 9.1.1.2.2. Fonction ludique ou de connivence 303 9.1.1.3. De la citation au partage 304 9.1.2. Partager 307 9.1.2.1. Hypertexte et intertexte 307 9.1.2.2. Fonction éditoriale 309 9.1.2.3. Fonction critique 309 9.1.2.4. Fonction informative/ d’identification 312 9.1.2.5. Fonction ludique 314 9.1.2.6. Un rapport à l’intertexte reconfiguré dans les billets scientifiques 315 9.1.3. Digresser 317 9.1.3.1. La digression comme pratique discursive 318 9.1.3.2. Quels « à côté » d’une activité de recherche ? 321 9.1.3.3. Comment se manifeste discursivement la digression au sein des carnets ? 323 9.2. L’énonciation des gestes de la recherche 328 9.2.1. Textualisation des pratiques de recherche : corporalité et gestes du chercheur 331 9.2.2. Textualisations et notations de gestes machiniques 336 9.2.3. Le lien hypertextuel comme textualisation d’un geste intellectuel du chercheur 339 9.3. Le discours d’une recherche en mouvements : gestes et réflexivité du discours scientifique des billets 341 10. Pour une approche rhétorique du blogging scientifique : la dimension argumentative des billets de recherche 343 10.1. Le chercheur comme témoin 344 10.2. L’ethos du chercheur-carnetier 347 10.1.1. L’ethos discursif, un concept au carrefour des traditions sociologique et rhétorique 347 10.1.2. Spécificités de l’ethos en contexte numérique et dans les carnets de recherche 350 10.3. Effets de dramatisation et recours au pathos dans le discours scientifique des billets 354 10.3.1. Mise en scène de l’émotion du chercheur 355 10.3.2. La création d’une connivence avec l’allocutaire : apostrophes, humour, allusions 360 10.4. Quelle dimension argumentative dans les billets de recherche ? 364 11. Ouverture : Après les attentats. Échos d’une actualité sociale dans deux carnets de recherche d’Hypothèses 371 11.1. La présence sociale des SHS à travers les carnets d’Hypothèses 372 11.2. Analyse d’une sélection de billets issus des carnets UC@ctualité et Janvier/novembre 2015. Réfléchir après 376 11.2.1. Énonciation éditoriale et iconographisation de la page d’accueil 377 11.2.2. Projet éditorial des carnets 381 11.2.3. Scénographie, gestes de savoir et dimension argumentative des billets du corpus 383 11.3. Quelle saisie de l’actualité par les médias de la recherche en SHS, pour quelle circulation des savoirs ? 391 Conclusion 395 Bibliographie 409 Sources primaires 409 Corpus premier 409 Exemples illustratifs tirés du corpus étendu 415 Exemples illustratifs hors bornes temporelles et/ou hors page d’accueil 418 Autres billets cités 419 Sitographie (Carnets de recherche cités) 421 Sources secondaires 421 Articles, monographies et billets 421 Sitographie 448 Table des illustrations 451 Index des notions 453 [less ▲]

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See detailETUDE DE LA CONTAMINATION DE L’ENVIRONNEMENT ET DES PRODUITS DE LA PECHE PAR LES PESTICIDES, DANS LE BASSIN COTONNIER BENINOIS
Zoumenou, Yémalin Mawunan Berny's Genia ULiege

Doctoral thesis (2019)

Northern Benin is recognized as a cotton growing area that uses large quantities of insecticides. The same agricultural area has water reservoirs developed for the production of fish that are a source of ... [more ▼]

Northern Benin is recognized as a cotton growing area that uses large quantities of insecticides. The same agricultural area has water reservoirs developed for the production of fish that are a source of protein for most of the northern population. Unfortunately, these impoundments and the fish that live there are subjected to strong pressures linked to the massive use of insecticides for cotton cultivation. The presence of residues of these insecticides in the water or fish of these reservoirs can cause health problems for consumers. In order to evaluate the levels of contamination of these insecticides in reservoirs and in fish, this work consisted in developing analytical methods for the control and monitoring of these pollutants. The first part of this document (the introduction) presents the study environment (the North of Benin), some generalities on the insecticides likely to be or to have been used for the cotton cultivation in the North of Benin, their become in the environment, their physicochemical, eco-toxicological and toxicological characteristics. The insecticides of interest in this work are some organochlorines (endosulfan, DTT and related compounds, isomers of HCH), some pyrethroids (lambda-cyhalothrin, permethrin, cypermethrin, beta-cyfluthrin) and neonicotinoids (especially acetamiprid) and the chlorpyrifos. The second part is the experimental section with 4 studies. In the first study, the development of a generic pyrethroid ELISA test was investigated using polycyclonal antibodies directed against the phenoxybenzene group common to a large number of pyrethroids. The polyclonal antibodies obtained, however, did not have sufficient affinity for lambda-cyhalothrin, one of the targeted pyrethroids of this study, for insecticide determination at the expected concentration levels in the environment (and water in particular). The second experimental study concerns the development of a gas-chromatographic mass spectrometry (GC-MS) multiresidue method for the determination of 16 compounds in water (10 organochlorines, 4 pyrethroids, chlorpyrifos and trifluralin). After validation of the method, a test for the recovery of the analytes in water samples stored under different conditions of time, temperature and container (glass or plastic) was carried out. This test made it possible to highlight that, whatever the conditions of conservation of water samples (glass or plastic bottles, 4 ° C or -20 ° C) supplemented at the rate of 1 g/L with various pyrethroids, these are no longer available for analysis, from the second day of storage, probably due to adsorption on the walls of the container. For organochlorines insecticides and chlorpyrifos, the recovery seems good if the water sample is stored at -20 ° C in glass bottles. The third study presents the development of a UPLC-UV method for the determination of acetamiprid in water. After optimization of the extraction, detection and quantification steps, the method was submitted to an inhouse validation according to several international guidelines including the European Commission's reference document SANTE/11945/2015 (SANTE 2015). The method was then applied to water samples taken from 4 reservoirs in northern Benin, close to cotton fields. This study shows that acetamiprid residues are present in impoundments at concentrations ranging from 0.2 to 7.7 μg/L. These concentrations of acetamiprid do not, however, constitute a risk to the health of the fish or to the man who consumes the water of these reservoirs. In the fourth study, the GC-MS multiresidue method developed for water in the first study was adapted for the determination of the same compounds in sediment and fish samples. After validation, the method was applied to samples of water, sediment and fish taken from the 4 reservoirs in northern Benin, already mentioned in the third study. In the water samples, analysis of these samples revealed the presence of trace organochlorines only (<1μg / L). It is in the sediment samples that the greatest number of residues has been recovered and in larger quantities, in particular with endosulfan levels of the order of 100 μg/kg. For pyrethroid residues, concentrations ranged from 0.2 to 14 μg/kg. Low amounts of chlorpyrifos were found (at concentrations of the order of 1 μg/kg). On the other hand, a wider range of concentrations was found for organochlorines (between 0.6 and 101 μg/kg). Finally, in fish, the concentrations of pyrethroids ranged between 1.5 and 11 μg/kg, those of chlorpyrifos between 1.8 and 3.3 μg/kg and those of organochlorines between 1 and 36 μg/kg. The risk assessment for each chemical contaminant taken alone shows that there is no risk to fish consumers in these water reservoirs. Finally, the last part presents a general discussion of the results obtained. Organochlorine, chlorpyrifos and pyrethroid residues have been found in sediment and fish matrices, but sediments appear to be more contaminated than fish and than water. At the level of the two fish species sampled, Clarias gariepinus, a sediment-dwelling species, appears to be more contaminated than the Oreochromis niloticus which live in the water, but a statistical comparison is not possible due to the small number of individuals sampled. Based on the results of this study concerning the contamination of fish with pesticides, and literature studies concerning the contamination of other foodstuffs with pesticides, it appears that the use of pesticides in the cotton basin results in the presence of pesticide residues in food in such a quantity as to constitute a risk for the health of the population. It is the case for chlorpyrifos and lambda-cyhalothrine, which can cause a chronic risk for children. In conclusion, analytical methods were developed during this study for the determination of different pesticides in water, sediment and fish. The risk assessment, for the local consumer, associated with the ingestion of pesticide residues shows that there appears to be no risk, considering the consumption of fish from the reservoirs only, but considering the total exposure of the population via other commodities, the quantities of pesticides ingested exceed the allowable doses, safe for health, in the case of children. Thus, to reduce the risk to the health of the population linked to the use of pesticides, measures should be put in place in Benin to monitor the food chain, reduce the amount of pesticide used in the cotton basin and propose alternatives (such as biopesticides) for the treatment of cotton and other crops. [less ▲]

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See detailPuissances émergentes et coopération Sud-Sud. Les enjeux de la pénétration chinoise en République Démocratique du Congo
Baenda Fimbo, Zacharie ULiege

Doctoral thesis (2019)

Four lessons are drawn from a series of demonstrations related to my thesis: 1. State power consists of three categories of attributes. Old material attributes (population and territory), current material ... [more ▼]

Four lessons are drawn from a series of demonstrations related to my thesis: 1. State power consists of three categories of attributes. Old material attributes (population and territory), current material attributes (economic, political and cultural) and immaterial attributes (identity, recognition and international representation). All these attributes are reinforced by South-South cooperation that allows emerging countries to extend their power away from their area of direct influence. 2. It is this model of cooperation that Chinese actors have with African countries and the change in their motivation depends on their political and economic objectives as well as the evolution of the international environment. Yet Africa does not form a coherent bloc. 3. Taking into account the historical, political and socio-economic particularities of the DRC, the economic and commercial activities of the Chinese actors in this country contribute to the construction of the economic power of China in Africa and contain issues (strategic, logistical, economic, migratory and positioning) likely to reproduce the mechanisms of domination of the Congolese economy. 4. To achieve their objectives, these Chinese economic actors mobilize the political tool (South-South cooperation to win the trust of their partners), the discursive tool (the historical referent to recall their assets and exploits of the past) and the economic tool (the public-private partnership to integrate the structures of the local economy). [less ▲]

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See detailÉtude des potentialités antiplasmodiales de plantes endémiques des Mascareignes: Poupartia borbonica Gmel., une nouvelle source de composés antimalariques prometteurs ?
Ledoux, Allison ULiege

Doctoral thesis (2019)

Ce travail de thèse a été mené dans l’optique de participer à la recherche de nouveaux antipaludiques provenant de plantes endémiques des Mascareignes. La première partie de ce travail est consacrée au ... [more ▼]

Ce travail de thèse a été mené dans l’optique de participer à la recherche de nouveaux antipaludiques provenant de plantes endémiques des Mascareignes. La première partie de ce travail est consacrée au criblage antiplasmodial in vitro réalisé sur 64 plantes provenant de l’île de la Réunion. Ces plantes ont été sélectionnées selon plusieurs critères : leurs endémismes, leurs usages traditionnels, ainsi que leurs inscriptions à la Pharmacopée. L’objectif principal de cette partie du travail consistait à mettre en évidence les plantes présentant une activité antiplasmodiale prometteuse (IC50 < 15µg/mL). Parallèlement, le second objectif était de valoriser la flore locale. Plusieurs plantes se sont avérées être intéressantes : le Casearia coriaceae, le Poupartia borbonica et le Vernonia fimbrillifera dont les IC50 sont inférieures à 10 µg/mL. Le Poupartia borbonica a été sélectionné en vue de réaliser des tests phytochimiques et pharmacologiques approfondis. La deuxième partie du travail est consacrée à l’exploration phytochimique et pharmacologique de cette plante endémique. Un fractionnement bioguidé a été entrepris et a conduit à la mise en évidence de trois nouveaux composés, des dérivés d’alkylcyclohexenones, les poupartones A, B, et C. Ces trois molécules présentent une activité antiplasmodiale prometteuse (IC50<2 µM). La poupartone majoritaire, la poupartone A, a été testée in vivo sur un modèle murin. Son potentiel antipaludique a été confirmé, puisqu’une dose de 15 mg/kg a permis une réduction de la parasitémie de presque 70%, 7 jours après l’infection. Cependant, une certaine toxicité a été observée. La troisième partie de cette thèse a consisté à mettre en évidence des pistes quant aux mécanismes de toxicité liés aux poupartones. Des tests sur larves de Zebrafish exprimant une fluorescence vasculaire ou une fluorescence musculaire ont permis de mettre en évidence qu’une toxicité cardiaque semblait être une conséquence d’un mauvais état général. L’atteinte la plus rapide et la plus marquée, sur toutes larves confondues, était liée à une toxicité de contact importante. Des tests de toxicité cellulaire réalisés avec des techniques d’imagerie en temps réel sur deux lignées cellulaires ont mis en évidence une hétérogénéité d’action. Cependant, la poupartone B induit des modifications importantes de l’adhésion cellulaire, ainsi que des mécanismes de type apoptotique. La dernière partie de ce travail a eu pour principal objectif de neutraliser cette toxicité périphérique en ciblant spécifiquement les globules rouges parasités par P. falciparum. Des liposomes contenant la poupartone B ont été réalisés, ceux-ci ont été entourés d’héparine, connue pour lier spécifiquement certaines protéines exprimées par les globules rouges infectés. Des tests réalisés sur larves de Zebrafish ont démontré une diminution de la toxicité, et les tests réalisés sur P. falciparum ont établi que l’activité était améliorée, même sur les Plasmodium partiellement résistants à l’artémisinine.   [less ▲]

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See detailFaire face à l’incertitude du monde. Pratiques diplomatiques et identité politique du Saint-Siège à l’épreuve des paix de Westphalie (1639-1651)
Regibeau, Julien ULiege

Doctoral thesis (2019)

Ma thèse est fondée sur une double question : quelle influence l’Europe des congrès de Westphalie exerce sur la reconfiguration diplomatique et politique de la papauté et quelle est la part des ... [more ▼]

Ma thèse est fondée sur une double question : quelle influence l’Europe des congrès de Westphalie exerce sur la reconfiguration diplomatique et politique de la papauté et quelle est la part des ambassadeurs du Saint-Siège – les nonces apostoliques – dans cette construction ? Cette problématique procède de l’uniformité interprétative que les historiens tendent à proposer des paix de Westphalie (1648), évènement majeur qui met fin à la guerre de Trente Ans (1618-1648). De manière générale, la signature des traités acterait l’effondrement de la chrétienté médiévale et conduirait à la naissance de l’Europe des États modernes. En bouleversant le modèle des relations diplomatiques, un tel processus serait à l’origine de la décadence diplomatique de la papauté et de l’échec à long terme du modèle politique romain. Le bref de protestation Zelo Domus Dei, publié par le pape Innocent X en 1650 pour condamner toutes les parties des traités qui contreviendraient aux intérêts du Saint-Siège et de l’Église catholique, en constituerait la preuve la plus évidente. Prenant le contre-pied de cette interprétation, j’ai interrogé les représentations que les nonces apostoliques construisent des congrès de Westphalie et des paix qui suivent afin de voir comment celles-ci influent sur les pratiques diplomatiques et l’identité politique de Rome. Pour ce faire, j’ai étudié les correspondances échangées entre la secrétairerie d’État romaine et les nonces en poste à Madrid, Paris, Bruxelles, Münster et Vienne entre 1639 et 1651. À travers les cinq chapitres qui composent le travail, j’ai cherché systématiquement à décaler le regard afin de montrer à quel point Rome propose une compréhension multiple des paix de Westphalie et de son rôle dans le monde qui s’annonce. J’ai commencé tout d’abord par modifier l’échelle de l’analyse en étudiant les correspondances des nonces apostoliques comme les productrices des normes et des écarts qu’elles mettent en texte. Sur base de cette nouvelle herméneutique, j’ai ensuite relativisé l’impact des paix de Westphalie sur leur actualité géopolitique en montrant qu’à la fin de l’année 1648, l’Europe est encore traversée par les conflits et que cette situation de crise conditionne les regards que les ambassadeurs romains jettent sur les traités signés. Troisièmement, j’ai voulu défataliser la protestation pontificale en montrant qu’elle n’est pas le résultat inévitable d’un siècle d’intolérances religieuses mais qu’elle se construit au contraire de façon heurtée, dans l’urgence des négociations de Westphalie, et s’autorenforce au travers de processus socio-politiques identifiables. Dans la quatrième partie, ensuite, j’ai insisté sur la pluralité des jugements que les nonces apostoliques portent sur les paix d’Allemagne au moment de leur survenue. Dans la cinquième partie, enfin, j’ai envisagé que l’attitude de rejet dont la diplomatie pontificale témoigne vis-à-vis des traités de Westphalie s’explique pour partie par le transfert des espoirs romains vers un autre terrain de négociations : celui, éphémère, qui se met en place entre la France et la monarchie espagnole durant l’été 1648, en vue d’entrainer la signature rapide de la paix entre les deux couronnes catholiques. De cette analyse il ressort qu’au milieu du XVIIe s. la papauté, bien que mise en tension par les évènements, n’est pas exclue ou déclassée par les autres États européens. Au même titre que nombre de leurs contemporains, les diplomates romains construisent au fil de leurs lettres l’image d’un monde dominé par les conflits auquel les paix de 1648 n’arrivent pas à apporter de réelle solution. Ces représentations leur permettent en retour de régénérer triomphalement la légitimité de leur institution en insistant sur la constance dont celle-ci fait preuve au milieu de la tempête, signe manifeste de sa proximité avec la Vérité divine. Cette thèse m’a donc permis d’apporter une réponse originale à la problématique du passage de la chrétienté à l’Europe à partir de l’étude du rôle charnière que joue la papauté dans ce processus. [less ▲]

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See detailExperimental Study of Nappe Oscillations on Free Overfall Structures
Lodomez, Maurine ULiege

Doctoral thesis (2019)

Free-overfall structures such as weirs and crest gates are commonly used as control structures for a variety of applications including irrigation, water treatmentand dam safety. The gravity-driven free ... [more ▼]

Free-overfall structures such as weirs and crest gates are commonly used as control structures for a variety of applications including irrigation, water treatmentand dam safety. The gravity-driven free falling jet on the downstream side of these structures, called the nappe, may display a variety of behaviors and instabilities among which, under relatively low heads/discharges, nappe oscillations, also known as nappe vibrations. This oscillating phenomenon is characterized by oscillations of the thin flow nappe cascading downstream of the crest and results in a significant disturbing noise production that increases negatively the environmental and societal impacts of the hydraulic structure. Given the lack of quantitative information reported in literature and the inchoate understanding of the dominant processes underpinning nappe oscillations occurrence and development, the global objective of this PhD thesis was to improve the knowledge of the nappe oscillation phenomenon. To that end, experimental modelling was seen as the best way to analyse the problem. First, a prototype scale model of a linear weir has been specifically designed and made flexible with respect to the main parameters of the weir. Then, two original characterization methods of the nappe oscillations properties have been developed based on the distinct audio and visual traits of the phenomenon. The application of these methods allowed the determination of the occurrence and development of the oscillations and their associated frequencies. Both were used systematically to assess the influence of various hydraulic and geometric parameters on the nappe oscillation phenomenon. Secondly, given the importance of scale physical modelling for hydraulic structure design, the possible scale effects affecting nappe oscillation were studied by considering a 1:3 scale model of the aforementioned prototype scale facility. The operation of this second model showed that nappe oscillations cannot be scaled according to the traditional similitude for weirs (Froude similitude). Instead, they always occur within the same unit discharge range independent of size scale, although they are prone to hysteretic behaviour and are less stable over time for smaller weir dimensions. Third, considering the data collected from the study of 52 geometric configurations and the expertise gained from hours of nappe oscillation observations and analysis, necessary conditions for nappe oscillation occurrence have been defined. Along with geometrical criteria regarding the fall height and width of the structure, these conditions, although not sufficient, allow to predict the occurrence of the oscillation in many cases. Finally, original mitigation techniques have been developed with the help of practicing engineers and contractors. Identified with respect to constructability, durability, performance and maintenance, these solutions were tested and optimized regarding disturbing noise reduction without impacting the hydraulic efficiency of the structure. Beside these extensive experimental works, in-situ measurements at two Belgian dams proved the applicability and robustness of the measurement methodologies developed in the framework of this thesis and the utility of the results to solve real world problems. [less ▲]

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See detailExperimental and numerical study of cracking during the desiccation of porous materials : application to the fields of chemical engineering and geomechanics
Hubert, Julien ULiege

Doctoral thesis (2019)

Porous material drying is a process used in many engineering fields such as food (conversation), plastic (polymer), chemical, pharmaceutical and wood (paper paste, composite beam for construction ... [more ▼]

Porous material drying is a process used in many engineering fields such as food (conversation), plastic (polymer), chemical, pharmaceutical and wood (paper paste, composite beam for construction) industries as well as any manufactured process based on paste or powder. It is also of importance in civil engineering because of its impact on soil properties and soil-structure interaction. This thesis is centered around two materials of interest in the fields of geomechanics and chemical engineering respectively. For the geomechanical part, the study is conducted under the scope of deep geological storage of nuclear wastes and the studied material is Boom clay. For the chemical engineering aspect, Resorcinol Formaldehyde hydrogels were chosen because after drying it can be pyrolyzed to obtain high specific surface carbonate porous structures which have many industrial applications as alternatives to activated carbon. The goal of this work is to develop a numerical model capable of accurately reproducing the drying kinetics of a porous material as well as being able to predict crack onset. A constitutive law has been implemented in a finite element code and validated based on drying experiments conducted in the laboratory. This thesis, therefore, combines numerical and experimental approaches. Thermo-hydro-mecanical simulations have been conducted to reproduce the experimental behavior. [less ▲]

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See detailLife-history and behavioural adaptations to xeric environments in fossorial amphibians
Székely, Diana ULiege

Doctoral thesis (2019)

Amphibians are particularly sensitive to environmental water availability due to their particularities in physiology, mainly related to permeable tegument and ectothermy, to their water-dependent ... [more ▼]

Amphibians are particularly sensitive to environmental water availability due to their particularities in physiology, mainly related to permeable tegument and ectothermy, to their water-dependent reproduction, and their reduced mobility compared to other vertebrates. However, amongst anurans, some fossorial species have adapted to xeric environments, either extremely dry or drastically seasonal and unpredictable in precipitation distribution. The present study aims at advancing the understanding of the complexity of life-history adaptations and behavioural strategies that allow fossorial anurans to survive in such demanding environments, through each particular stage in the life-cycle of the study organism (larvae, juveniles, adults, and finally reproduction and egg-laying). To test the research predictions, a seasonally dry tropical forest located in the Pacific Ecuador, Arenillas Ecological Reserve, was chosen as the study site. The climate at this location is characterized by severe seasonality in terms of precipitation regime, but with a minimal variation in temperature throughout the year. The project is focused on the Pacific horned frog Ceratophrys stolzmanni, the only fossorial anuran present at the study site. The effects of water limitations were evident in the species starting with the first and most sensitive life-stage, the aquatic tadpoles. The larvae responded to both tested types of cues related to the danger of pond desiccation: an increase in tadpole density as well as a decrease in water level, by rapidly modifying their development and growth in response to the environmental conditions. When not experiencing water limitations, tadpoles were able to capitalize on favourable aquatic conditions by intensifying their growth rates, delaying their transition to terrestrial habitat and metamorphosing at large size. The size at metamorphosis was a particularly important parameter for the fitness of individuals, since the detrimental conditions experienced during larval development were carried-over to the juvenile stage, and froglets metamorphosing at a small size experienced higher mortality and achieved lesser performance in food acquiring and predator avoidance traits. The activity of the horned frogs was strongly related to the precipitation pattern, individuals coming out of the ground mainly during or shortly after rains. This means that at the study site there are a limited number of opportunities for them to acquire food even during the short rainy season. However, the species showed intense growth rates both before and after metamorphosis, and both males and females were able to sexually mature in their first year of life. Some of the investigated behavioural strategies contribute to reduce their overall energetic expenditures: low individual mobility, the choice of burrows depth in accordance with substrate humidity and an abbreviated mating season. Additionally, to diversify the modalities of resource exploitation, the Pacific horned frogs employed some mechanisms that are rather unusual for most anurans. Amongst them, they exhibited a divergence in temporal niche between terrestrial life-stages, which probably reduces intraspecific interactions and allows increased access to food for the smaller juveniles. The other mechanism refers to the capacity to consume a wide variety of prey items, including vertebrates. The intense growth rates and rapid maturation probably come at a cost of increased mortality, reflected in the low longevity of individuals from the studied population. In this aspect, the permanence of the species in such an unpredictable environment suggests that mass tadpole mortality caused by pond desiccation is rather uncommon. This is due at least partially to the synchronized reproduction that takes place at the first heavy storm of the rainy season, as soon as breeding pond become available, giving the tadpoles the longest interval possible to develop. Additionally, the female investment in a relatively large number of eggs and the overall short larval duration should contribute to successful yearly recruitment. Our study enhances the understanding of this poorly-known species and of the potential risks to its long-term survival. Due to the strong influence of rainfall regime on all life-stages, the predicted changes in precipitation patterns are likely to lead to further restriction of the activity of the frogs and to reductions of recruitment or juvenile fitness. Additionally, the short reproductive lifespan of the species makes the persistence of the population vulnerable to persistent droughts of 2–3 consecutive years. The population parameters that we provide in this thesis serve as base-line information for the present welfare of the population, and can be a starting point for the detection of potential declines. This knowledge should be included in future management plans for the effective conservation of the species. [less ▲]

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See detailEtude des interactions de molécules phytotoxiques avec des modèles membranaires inspirés de la membrane plasmique végétale
Lebecque, Simon ULiege

Doctoral thesis (2019)

L’agriculture se trouve actuellement face à un double défi : produire suffisamment et produire durablement. Ces dernières décennies, l’accent a essentiellement été mis sur les rendements, tirés vers le ... [more ▼]

L’agriculture se trouve actuellement face à un double défi : produire suffisamment et produire durablement. Ces dernières décennies, l’accent a essentiellement été mis sur les rendements, tirés vers le haut notamment via l’usage massif d’herbicides synthétiques permettant de gérer les adventices. Leur efficacité est cependant menacée par le développement de résistances parmi les adventices, lié au faible renouvellement de leurs modes d’action. De nombreuses études pointent en outre les risques associés à l’usage de ce type de produits tant pour l’environnement que pour la santé humaine. De nouveaux outils de lutte contre les adventices sont donc activement recherchés afin de rencontrer ces deux enjeux. L’allélopathie, qui désigne le phénomène par lequel certaines plantes affectent le développement des plantes voisines en émettant des composés (allélo)chimiques dans l’environnement, représente une piste prometteuse à cet égard. Il paraît toutefois nécessaire d’identifier au préalable les composés allélochimiques impliqués dans de telles interactions et d’élucider leur mode d’action afin d’en faire une exploitation sécurisée, maîtrisée et optimisée. Plus largement, de nombreuses molécules d’origine végétale s’avèrent phytotoxiques, et pourraient donc servir d’herbicides naturels présentant potentiellement des modes d’action nouveaux et une biodégradabilité plus élevée que les herbicides synthétiques traditionnels. L’objet de cette thèse consiste à étudier certaines molécules phytotoxiques d’origine végétale sous un angle original : leurs interactions avec des modèles membranaires inspirés de la membrane plasmique de plante. Cette perspective est intéressante car la membrane plasmique est à la fois le site d’interaction initial d’un composé toxique avec une cellule et le siège de nombreux processus cruciaux pour le bon fonctionnement cellulaire, et apparaît donc comme une cible potentielle. Des bicouches lipidiques artificielles composées de lipides retrouvés dans la membrane plasmique de plante ont été utilisées pour étudier le comportement de molécules phytotoxiques d’origine végétale en présence d’un tel environnement. Deux types de structures moléculaires ont été étudiés dans ce contexte : des petits composés aromatiques amphiphiles et des composés possédant une chaîne hydrocarbonée. Dans un premier temps, deux alcaloïdes de l’orge, la gramine et l’hordénine, ont été considérés. Il s’agit de composés caractérisés par une petite structure aromatique et amphiphile. Leur phytotoxicité a été évaluée via des essais biologiques réalisés sur Matricaria recutita L., la camomille, une adventice commune d’Europe. Les deux composés ont induit une réduction de la longueur racinaire chez cette espèce, mais la gramine s’est révélée nettement plus toxique que l’hordénine. Les interactions de ces molécules avec des bicouches lipidiques ont ensuite été investiguées grâce à des techniques de biophysique. Des titrages calorimétriques isothermes ont permis de montrer que l’affinité de la gramine pour des bicouches lipidiques est supérieure à celle de l’hordénine. Des expériences en spectroscopie infrarouge ont mis en évidence l’impact de ces alcaloïdes sur une propriété importante des bicouches lipidiques : leur température de transition de phase. A nouveau, l’effet de la gramine sur ce paramètre s’est avéré plus important que celui de l’hordénine. Les mécanismes moléculaires sous-jacents ont été explorés par le biais de simulations de dynamique moléculaire. Les résultats des expériences de biophysique sont discutés, de même que leur possible corrélation avec les résultats des tests biologiques. Dans un deuxième temps, des molécules avec un autre type de structures, incluant une chaîne hydrocarbonée, ont été étudiées. L’acide nonanoïque, la sarmentine et la sorgoléone ont été choisis. Leur impact sur l’ordre et la fluidité de bicouches lipidiques a été étudié par fluorimétrie. L’utilisation du 1,6-diphenyl-1,3,5-hexatriène (DPH) et du laurdan, deux sondes fluorescentes, a ainsi permis de mettre en évidence l’augmentation d’ordre et l’augmentation de la température de transition de phase d’une bicouche lipidique induite par la présence de sorgoléone. L’acide nonanoïque et la sarmentine ont en revanche semblé n’avoir qu’un impact minime ou inexistant sur ces mêmes paramètres. Grâce à des titrages calorimétriques isothermes, l’affinité des trois molécules pour les bicouches lipidiques a pu être mesurée, et classée comme suit : sorgoléone >> sarmentine > acide nonanoïque. Des simulations en dynamique moléculaire ont enfin été réalisées afin d’obtenir des détails concernant la localisation préférentielle des composés au sein d’une bicouche lipidique. Une analyse du paramètre d’ordre des chaînes hydrophobes des lipides basée sur ces simulations a confirmé l’effet rigidifiant de la sorgoléone et suggéré la présence d’une possible influence subtile de l’acide nonanoïque et de la sarmentine sur la stabilité des bicouches lipidiques. Les résultats sont discutés par rapport à leur implication potentielle quant à la phytotoxicité des composés. Une discussion générale revient sur les principaux résultats obtenus dans le cadre de la thèse, leur apport à l’état des connaissances et les limites de leur signification. L’impact de certains traits structuraux présentés par des molécules phytotoxiques susceptibles d’interagir avec des bicouches lipidiques est discuté. Finalement, des perspectives à partir de cette thèse sont évoquées, en soulignant notamment l’importance des recherches à mener pour mieux comprendre le fonctionnement de la membrane plasmique et le rôle de sa composante lipidique. [less ▲]

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See detailSelf-organization of a monolayer of magnetized beads
Schockmel, Julien ULiege

Doctoral thesis (2019)

We present experimental results obtained with a model experimental system dedicated to the study of 2D structures and phase transitions. The system is composed of a monolayer of millimetric soft ... [more ▼]

We present experimental results obtained with a model experimental system dedicated to the study of 2D structures and phase transitions. The system is composed of a monolayer of millimetric soft ferromagnetic beads confined in a 2D horizontal cell. The beads are immersed in a vertical and homogeneous magnetic field inducing magnetic dipole-dipole interactions between beads. Due to the confinement, the repulsive interactions tend to order the system. As the system is athermal, a mechanical agitation is used to produce a Brownian motion of the beads which creates disorder. Adjusting the competition between the effects of the interaction and the agitation allows us to control the order of the system. Thanks to this experimental setup, we can study the transition from a frozen and very ordered state, called a crystal, to a disordered and dynamic state similar to a liquid. As predicted by the KTHNY theory of 2D melting, a two-step transition is highlighted, including the so-called hexatic phase between crystal and liquid. In addition, the structures observed agree quantitatively with structures obtained in colloidal systems and in numerical simulations. Our experimental system is, therefore, a suitable model to study 2D thermal structures. In this work, we focus on the study of topological defects that are crucial in low-dimensional physics. We first forced topological defects into the syttem by inducing frustration from confinement. We show that the size and the geometry of the confinement strongly affect the global order, as well as the type and the number of topological defects observed in the systems. Finally, we force pointlike defects in the structure by introducing beads of different size, called impurities. At global scale, the increase of the impurity can prevent the crystallization. At local scale, we observe that an impurity induces a very localized geometrical frustration, which creates a topological defect whose nature is directly related to the size of the impurity. [less ▲]

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See detailBiostratigraphie, paléoécologie et évolution thermique du Supergroupe Mésoprotérozoïque de Mbuji-Mayi, RdCongo.
Kabamba Baludikay, Blaise ULiege

Doctoral thesis (2019)

Understanding the origin, evolution and distribution of life in Universe - the subject of astrobiology - requires unambiguous knowledge of the different stages of evolution of life on Earth, the only ... [more ▼]

Understanding the origin, evolution and distribution of life in Universe - the subject of astrobiology - requires unambiguous knowledge of the different stages of evolution of life on Earth, the only planet where, for the moment, the existence of life is an absolute evidence. This requires the contribution of several scientific disciplines (biology, geology, geochemistry, geophysics, micropaleontology ...) in the production of data relating to the Precambrian, period during which life appeared on Earth and knew its first stages of evolution. This study focusses on a key period of life evolution, and in particular the diversification of early eukaryotes, during the Proterozoic. It presents the results on the micropaleontology, palaeoecology, chemostratigraphy and geothermometry of the Mbuji-Mayi Supergroup, located in the Democratic Republic of Congo. This sedimentary sequence is dated between 1065 and 1000 Ma (late Mesoproterozoic). The results obtained using conventional analyzes (optical microscopy, mass spectrometry, Raman microspectroscopy, XRD, solid bitumen reflectance and TAI) reveal: (1) a well-preserved assemblage of organic-walled microfossils, consisting of 49 taxa of which 11 unicellular and multicellular eukaryotes. This assemblage is similar to other contemporaneous assemblages known elsewhere in the world, impliyng a connection with the other oceanic basins, and permitting to improve Proterozoic biostratigraphy ; (2) a redox stratification of ocean water into oxic, anoxic iron-rich and anoxic sulfidic-rich zones during the deposition of the Mbuji-Mayi Supergroup; (3) an abundance and better preservation and perhaps habitats of eukaryotes in proximal anoxic and iron-rich environments; (4) δ13Ccarb variations similar to contemporaneous variations elsewhere in the world; (5) a similarity between the different ranges of temperature estimates from Raman geothermometers, solid bitumen reflectance or Kübler index obtain on clays. This has shown that extraction of kerogen by acid attack does not alter its chemical signal. This moderate diversity of eukaryotes at ~ 1065 Ma makes it possible to set back the great diversification of the first eukaryotes which is generally estimated at 800 Ma, and to show that it also happened in Africa. [less ▲]

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See detailContribution à l'évaluation de la fonction musculaire rachidienne du sportif
Grosdent, Stéphanie ULiege

Doctoral thesis (2019)

Aims: to clarify the muscular function of the trunk and to study the relationships between low back pain (LBP) and the spinal muscles in athletes. The literature review presented in the first section ... [more ▼]

Aims: to clarify the muscular function of the trunk and to study the relationships between low back pain (LBP) and the spinal muscles in athletes. The literature review presented in the first section discusses athlete spinal pathology, lumbar spinal musculature characteristics and highlights the prevalence and risk factors associated with the occurrence of LBP in athletes. The second part of our work specifies the trunk muscle profile in relation to sport and LBP. After a review of the literature on muscle and joint evaluation (step 1), our studies compare on the one hand the muscular and articular lumbopelvic performances of asymptomatic competing athletes practicing different sports disciplines (tennis, football, swimming, rowing) and a controlled population (step 2), and on the other hand, competitive athletes (football and tennis players) with and without LBP (step 3). While there are some specificities in the trunk muscles profile related to the sport discipline, our studies do not report a link between the presence of LBP and the maximum voluntary force, the asymmetries of strength of the trunk muscles or the lumbopelvic flexibility in tennis and elite football players. In young elite crawl swimmers, a complementary study (step 4) highlights two sprint performance indicators: the maximum isometric strength of the extensor muscles and the fatigue resistance of the trunk flexor muscles. In the third part, our work focuses on the quality of sensorimotor control and stability of the trunk and lumbopelvic region of athletes with LBP or with a history of disabling LBP. A review of the literature (step 1) confirms the current lack of standardized criteria for the evaluation of functional lumbar instability (FLI) and lumbopelvic movement control (LMC). The study of an athletic population with LBP (step 2) highlights that athletes with signs suggestive of FLI are an important subgroup and highlights the relevance of some elements of the history and clinical examination for the diagnosis of FLI in athletes with LBP. The assessment of the LMC of young elite football and tennis players (step 3), using a battery of five field tests, discriminates players with and without a history of LBP and confirms that the disappearance of symptoms and the sports recovery is not enough to restore an optimal LMC. Finally, the implementation of a specific and progressive training of LMC among young elite tennis and football players with a deficit of LMC (step 4) improves the LMC and tends to reduce the prevalence of LBP in these athletes in the short and medium term. In conclusion, athlete's low back pain appears to be correlated with the quality of muscular contraction and lumbopelvic movement, rather than the amount of activation or muscle strength produced. The LMC impairment appears to be a result of lower back pain and advocates for the management of athletes with a history of pain and / or lumbar lesions (secondary prevention). [less ▲]

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See detailEnvironmental impact assessment of rail freight intermodality in Belgium using a Life Cycle Assessment approach
Merchan Arribas, Angel ULiege

Doctoral thesis (2019)

Freight transport is a crucial sector for the development of the economy and society, but it also produces negative impacts on the environment and the human health that must be considered. Intermodal ... [more ▼]

Freight transport is a crucial sector for the development of the economy and society, but it also produces negative impacts on the environment and the human health that must be considered. Intermodal freight transport represents an opportunity to achieve a transport of goods with enhanced environmental and competitive characteristics. Hence, intermodal freight transport consists in the transport of goods by at least two modes of transport, in the same loading unit (e.g. container), without handling the goods themselves when changing modes in an intermodal terminal. Intermodal freight transport leads to the shifting of road freight transport in long distances to others modes of transport with improved environmental performance such as rail freight transport and inland waterways transport. This thesis is concerned with a study of the environmental impacts of rail freight intermodality using a life cycle approach. The purpose of this research is to analyse the environmental impacts of the different inland freight transport modes in Belgium (focusing on rail freight transport), and their use in intermodal freight transport routes in Belgium and Europe. In this framework, the Life Cycle Assessment (LCA) methodology constitutes an effective tool to assess the environmental impact of the inland freight transport modes. The system perspective of the LCA methodology implies the need to analyse not only the direct processes related to the transport activity such as energy consumption and exhaust emissions, but also the processes connected with the electricity and fuel production, vehicles (e.g. locomotives and wagons, barges and lorries) and infrastructure (e.g. railway, inland waterways and road). This thesis studies the inland freight transport in Belgium from the period 2006 to 2012. It has been carried out the LCA of rail freight transport (distinguishing between electric and diesel traction), inland waterways transport and road freight transport independently. A comparison between the environmental impacts of these inland freight transport modes has been performed as well. Within rail freight transport, the environmental impacts of electric trains using the electricity supply mix of different European countries have been compared. Moreover, a detailed study of the life cycle phases of construction, maintenance and disposal of railway infrastructure has been conducted. Furthermore, the influence of load factor and emission engine technology in the environmental performance of road transport have been studied. In addition, a study of the environmental impacts of consolidated intermodal freight transport routes in Belgium and Europe have been carried out. The aim of this analysis is the comparison of the environmental impacts of these intermodal routes depending on the transport mode chosen for the major part of the intermodal route. Finally, this thesis studies the environmental impact of the modal splits of inland freight transport in Belgium for several scenarios such as the increase of rail freight transport as a result of the possible development of the intermodal rail freight transport or the optimization of the operational costs. It has been analysed how the change of the modal split and the improvement of the technology used by the different transport modes affects the environmental impacts of inland freight transport in Belgium. [less ▲]

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See detailConstruction d'une demande de justice écologique. Le cas des semences non-industrielles
Hecquet, Corentin ULiege

Doctoral thesis (2019)

Via the « Distinction Uniformity Stability – DUS » criteria, the legislative framework of the European Union (extended to other countries including Brazil) imposes a norm of standardization for the ... [more ▼]

Via the « Distinction Uniformity Stability – DUS » criteria, the legislative framework of the European Union (extended to other countries including Brazil) imposes a norm of standardization for the registration of plant varieties in the catalogue allowing to put them on the market. Only a few practionners of crop biodiversity register their crop varieties despite the existing derogation system. Starting from a set of 4 case studies – BioNatur (Brazil), Semailles (Belgium), Kokopelli (France) and Kaol Kozh (France – Brittany), I demonstrate that these crop diversity farmers develop numerous, even contradictory strategies – ambiguity, spreading, disobedience, circumventing- to enable the circulation of their seeds, but at the same time, to make visible their claims in order to face the unjust system generated by DUS. Behind these heterogeneous strategies, I identify a claim for ecological justice. Through the dimensions of distribution, recognition and participation, I propose an empirical study with a specific attention on the notion of public and I add the experimentation dimension of ecological justice. At it is hard for practionners to participate at the debate about DUS, the different strategies aren’t unlocking the conventional seed system, nevertheless I support that they are crumbing it away (effritement). [less ▲]

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See detailAssessing irrigation water saving for crop production in Cambodia based on combined in situ and modelling approaches
Ket, Pinnara ULiege

Doctoral thesis (2019)

In recent decades, climate change has become the major constraint for agricultural production in Cambodia and leads to future concern of food security. Improving effective irrigation management ... [more ▼]

In recent decades, climate change has become the major constraint for agricultural production in Cambodia and leads to future concern of food security. Improving effective irrigation management, especially for non-rice crops that use less water is urgently needed. The aim of this thesis is to contribute the development of vegetable production during the dry season in Cambodia. The specific objective of the research is to optimise irrigation water use at the on-farm level. We focused on developing a methodology for i) characterising soil hydraulic properties for crop models and ii) exploring the best irrigation scenarios for vegetable irrigation. Two growing season experiments with lettuce were conducted during 2016 and 2017 in five farm fields in the Chrey Bak catchment, Kampong Chhnnag Province, Cambodia. Two approaches were tested to achieve irrigation water saving. Firstly, a method using a soil water model, HYDRUS-1D, was used to inversely estimate the van Genuchten soil hydraulic functions in the unsaturated zone. The five experimental fields had different soil textures, loamy sand, sand and loam, and the field data (i.e., irrigation amounts, weather, lettuce growth data, soil permeability, etc.) were collected and measured to feed the given model. To generate the soil parameters, the objective functions were generated using inverse data such as measured soil moisture dynamics and soil water retention curves, using a combination of a soil moisture sensor, 10HS, and soil potential sensor, MPS-2, for a 30 minute time step. Our analysis showed that the inverse modelling successfully estimated the soil water retention curve and soil water dynamic with reasonable accuracy when compared to the observed values. However, uncertainties of the simulation and data measurement were observed, especially for the SWRC in dry and wet conditions. For the second study approach, to explore irrigation water saving the AquaCrop model was used to simulate irrigation scheduling under water stressed conditions. In the second study approach, to explore the irrigation water saving, the water driven model, AquaCrop was selected for simulating irrigation scheduling under water-stressed conditions. The crop growth parameters for lettuce were calibrated using field data from the 2017 experimental growing season from two fields that have sand and loam soil textures. In the calibration process the measured crop growth data were used, e.g. canopy cover and above ground biomass collected over a 3 day time step, taking into account the other factors of irrigation management such as drip irrigation and mulching. Then, the method for optimal irrigation scheduling was described. Two main categories of irrigation scheduling for deficit irrigation were developed. The first varied thresholds of readily available water content (RAW) for the stop irrigation point under different no water stress and stress conditions. The second decreased deficit irrigations below field capacity (FC). The results of the calibration for crop growth were quite satisfactory. A primer set of adjusted lettuce parameters was obtained. The results highlighted limitations of the model in defining heat stress and root depth of the vegetable. Primarily, analysis results of irrigation scheduling scenarios show the capabilities of the model to identify the optimum water saving alternatives under limited water conditions. Overall, this PhD thesis opens perspectives for improving irrigation management for increased crop productivity in Cambodia [less ▲]

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See detailDevelopment and optimization of in silico models of 2D cell expansion and 3D neotissue formation in the context of tissue engineering therapy design and translation
Mehrian, Mohammad ULiege

Doctoral thesis (2019)

Tissue engineering is an interdisciplinary field that applies the principles of engineering and life sciences towards the development of biological constructs with the ability to heal, improve, or replace ... [more ▼]

Tissue engineering is an interdisciplinary field that applies the principles of engineering and life sciences towards the development of biological constructs with the ability to heal, improve, or replace damaged tissue. Despite the increasing amount of research which has led to some progress in delivering bench to bedside solutions in the field of bone tissue engineering, the transition rate of these solutions from research to clinics has been slow due to the lack of reproducibility and quality control in the constructed tissues. Computational models, applied in the context of process engineering strategies, are considered as great tools for addressing these issues by providing appropriate means that enable us to predict and optimize the neotissue formation during the in vitro culture. In this thesis, a computational framework is developed investigating the in vitro cell expansion process in 2D tissue flasks and 3D scaffolds in a perfusion bioreactor set-up. In the first part of this thesis, a data-driven model was built, based on the information of 174 donors with the aim of predicting the population doubling time (PDT) of the donor-derived cells. For this purpose, a Random Forests technique using five cell- and donor-specific input parameters (age, gender, initial seeding, surface area and the previous culture time) was applied. It is showed that the age of the donor has the most important factor influencing the PDT (especially for the first two passages). Furthermore, the prediction error for the PDT is lower than for the current standards used in the laboratory for predicting the PDT. In the second part of this thesis, a computationally efficient model was developed describing the growth of neotissue (cells and their extracellular matrix) inside 3D scaffolds. The growth of neotissue is modeled as a function of oxygen, glucose, pH level, mean curvature of the neotissue-void interface inside the 3D scaffold, and the shear stress caused by the medium flow that is perfused through the scaffold and the neotissue. Bayesian optimization was used to find the best refreshment strategy that maximizes the neotissue growth during the culture time. Subsequently, a novel cost function considering the cost of labor and culture medium was added to the developed model with the goal of maximizing the neotissue growth and minimizing all associated experimental costs during the culture period. The Multi-objective optimization problem was solved using four evolutionary algorithms and three different settings each. Using the obtained Pareto-front, we were able to choose the most optimal solution to the Multi-objective optimization problem. Finally in the last part of this thesis, the neotissue model developed in the previous part was further expanded by making a distinction between the growth of cells and production of ECM, as well as considering the effect of a generic growth factor on cell proliferation and differentiation. Using a new cost function taking into account the costs of the growth factor, labor and culture medium, refreshment strategies leading to maximum cell proliferation and minimum overall experimental costs were identified. Therefore, this model could be used to predict cell expansion in 3D scaffolds as an alternative for cell expansion in conventional 2D flasks. In conclusion, this PhD thesis shows the potential of computational models in investigating the cell expansion and tissue growth in 2D and 3D environments and demonstrates how these models can assist in the achievement of a robust and predictable bioprocess for regenerative medicine applications. [less ▲]

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See detailMilk protein adulteration detection via mass spectra and infrared spectroscopy
Yang, Jinhui ULiege

Doctoral thesis (2019)

Milk protein adulteration concerns the addition of cheap foreign substance having high nitrogen content into milk and dairy products, to mask low natural protein in milk. Plant protein is a potential ... [more ▼]

Milk protein adulteration concerns the addition of cheap foreign substance having high nitrogen content into milk and dairy products, to mask low natural protein in milk. Plant protein is a potential candidate of adulterants; soy, pea, wheat, and rice proteins being the most popular. The consumption of those adulterants could induce serious Human health disorders. Therefore, the development of detection methods for protein milk adulteration is of great importance to guarantee food safety. The current thesis aims to test and compare methods such as two-dimensional gel electrophoresis (2-DE), liquid chromatography tandem mass spectrometry, and infrared spectroscopy to detect foreign protein spiked in milk, especially hydrolyzed plant proteins. Here are the major results: (1) According to the protein spots highlighted on the polyacrylamide gel of adulterated milk, β-conglycinin and glycinin were detected in milk adulterated with soy protein, while legumin, vicilin, and convicilin indicated the addition of pea protein, and β-amylase and serpin marked wheat protein. 2-DE-based protein profile allowed to identify milk spiked with soy and pea protein, with a detection limit of 4% plant protein in the total protein. (2) Sodium dodecyl sulfate -polyacrylamide gel electrophoresis (SDS-PAGE) gels revealed clearly that centrifugation at 20 000 g for 60 min reduced band intensity of casein and albumin in milk. No obvious protein line was observed for hydrolyzed wheat and rice protein. Results of nano-HPLC-MS/MS highlighted the major proteins of soy (β-conglycinin, glycinin), pea (vincilin, convicilin, legumin) and wheat (glutenin and gliadin) in adulterated milks. So, this method allows the detection of hydrolyzed soy and wheat protein at the level above 0.5% in total protein, and pea protein at the level of 2 and 4%. No rice protein was identified in milk samples adulterated with hydrolyzed rice protein. Combined with principal component analysis (PCA), nano-HPLC-MS/MS discriminated all the adulterated samples from authentic milk. (3) Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-MIR) applied to commercial skimmed milk was also tested to identify protein milk adulteration and to estimate the non-protein nitrogen content (eNPN). Spectral clusters revealed by PCA depended on the level and type of adulterant. The developed partial least square (PLS) regression showed good performance of ATR-FTIR to predict eNPN (R2 = 0.70, RMSE = 0.06 g/100 g of full cross-validation). The addition of adulterants to milk increased the eNPN level for all samples and ranged from 0.04 to 0.37 g/100 g. Based on the difference between the known NPN range in normal milk and the predicted eNPN of adulterated samples, it was possible to detect samples adulterated with hydrolyzed rice (HRP), soya (HSP) or wheat (HWP) with a content higher or equal to 3.8 g/L. This study cannot be generalized as the natural milk composition change was not taken into account. Therefore, a second study was iv conducted to validate these first observations and to enlarge the use of infrared spectroscopy to near-infrared. (4) So, 9 raw cow milk samples were adulterated with different levels of HRP (2.5-40 g/L), HWP (1.875-30 g/L), whey (1.875-30 g/L), urea (0.5-8 g/L), and water (3.125-50 g/L). Those 234 samples in total were analyzed using ATR-MIR and near-infrared (NIR) spectrometers. The developed NIR and ATR-MIR PLS - discriminant analysis did not discriminate control milk from adulterated samples. Raw ATR-MIR spectra discriminated better on HRP and HWP adulteration above 6.25%, while first derivative NIR spectra detected whey content above 12.5% in milk. Good prediction performance was observed to quantify the level of HRP and urea in raw milk using both ATR-MIR and first derivative NIR spectra (validation R2p> 0.96). ATR-MIR showed better prediction on HWP level than NIR (validation R2p=0.95 vs. 0.88), while NIR had a better accuracy in whey level quantification (validation R2p=0.97 vs. 0.40). Moreover, both technics predicted well the total protein adulterant level (without water) in adulterated samples (validation R2=0.87-0.98, RMSE=2.04-4.11 g/L). Consequently, the use of untargeted quantitative analysis is possible to detect the level of protein adulterants (such as hydrolyzed plant protein, urea or whey) in milk using NIR or MIR infrared spectroscopy, although classification of samples between adulterants types gave contrasted performances depending on the adulterant level and the king of spectroscopy used. [less ▲]

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See detailLa céramique tardo-républicaine en Italie centro-tyrrhénienne : établissement et confrontation des faciès du Latium septentrional et d'Etrurie méridionale entre le IIe s. et le Ier s. av. n.è.
Motta, Lucie ULiege

Doctoral thesis (2019)

La céramique n’est désormais plus à établir comme élément fondamental de nos connaissances des mondes anciens, que ce soit d’un point de vue chronologique, économique ou culturel puisqu’au-delà de son ... [more ▼]

La céramique n’est désormais plus à établir comme élément fondamental de nos connaissances des mondes anciens, que ce soit d’un point de vue chronologique, économique ou culturel puisqu’au-delà de son rôle d’élément datant auquel s’arrêtent encore bien trop d’études, elle est l’une des principales sources d’informations en étant un produit direct de la culture qui l’a produite. Sa quasi-omniprésence dans le mobilier archéologique et les fortes quantités excavées ne sont alors pas sans lien avec la solidité du matériau. En effet, bien que les objets ainsi réalisés soient aisément brisables, la matière constitutive – l’argile cuite – est particulièrement résistante et ne se détruit que difficilement, que ce soit par le sol et sa nature, le temps, l’action de l’homme ou la combinaison de ces divers facteurs. Elle n’est notamment pas recyclable comme peuvent l’être le verre ou les métaux, et encore moins périssable comme les matières organiques. Le choix d’orienter cette recherche sur l’Italie centro-tyrrhénienne tardo-républicaine n’est évidemment pas anodin et résulte de la constatation d’une lacune flagrante dans nos connaissances de sa céramique, bien qu’il s’agisse d’un ancrage, aussi bien chronologique que géographique, charnière de l’Histoire romaine. Ainsi, la ligne directrice de ce travail vise à constituer une première tentative de caractérisation du faciès céramique, aussi bien dans son uniformité que dans ses spécificités régionales et de déterminer son évolution interne, que ce soit en matière de classes, catégories, formes et types. Pour ce faire, une méthodologie rigoureuse a été mise en place afin de disposer d’un corpus composé d’éléments suffisamment similaires pour établir un raisonnement fiable. Trois axes ont notamment été au coeur de cette réflexion : - la nature des contextes afin d’écarter au maximum la notion de sélection des céramiques a priori, en excluant notamment les contextes cultuels. - la possibilité de disposer de l’intégralité du matériel céramique sans aucune sélection a posteriori, afin de pouvoir croiser les données de toutes les catégories et en tirer les conclusions au sujet des assemblages en eux-mêmes. - la quantification, dont l’usage reste relativement rare dans les études italiques, normalisée et appliquée à l’intégralité du matériel céramique afin d’envisager une nouvelle approche du domaine.L’étude a alors été centrée sur deux aires géographiques bien précises – le Latium septentrional et l’Étrurie méridionale – pour lesquelles il a fallu établir les faciès respectifs et leurs évolutions en s’interrogeant sur les rapports des classes, catégories, formes, types et provenances à travers trois ères chronologiques – la première moitié du IIe s., la seconde moitié du IIe s., et le Ier s. av. n.è. Des études macroscopiques ont également été réalisées sur les pâtes du matériel provenant des études de cas. Les groupes techniques mis en évidence ont alors été confrontés aux données déjà existantes afin de faire ressortir les zones d’approvisionnement, les questions d’échanges commerciaux, d’importations et de productions locales ou régionales. Plus modestement, cette étude a également tenté d’ouvrir le discours aux tendances et pratiques alimentaires en confrontant les résultats, notamment morphologiques et fonctionnels, obtenus lors de l’établissement du faciès avec les sources littéraires et les études déjà menées sur le sujet. Notons enfin que ce travail, loin d’être définitif, devra être nourri par d’autres recherches afin de s’étoffer pour confirmer ou infirmer les hypothèses proposées. [less ▲]

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See detailEssays on the effects of retirement and labour market policies in Belgium
Tarantchenko, Ekaterina ULiege

Doctoral thesis (2019)

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See detailLa figure d’Hercule dans l’art de la tapisserie à la Renaissance (c. 1450-1565). Fortune iconographique et usages politiques
Laruelle, Anne-Sophie ULiege

Doctoral thesis (2019)

Les exploits d’Hercule, l’un des thèmes littéraires et artistiques les plus appréciés à la Renaissance, connut une faveur toute particulière dans le domaine de la tapisserie, genre artistique majeur à ... [more ▼]

Les exploits d’Hercule, l’un des thèmes littéraires et artistiques les plus appréciés à la Renaissance, connut une faveur toute particulière dans le domaine de la tapisserie, genre artistique majeur à l’époque. Des tapisseries de grande qualité ont été réalisées sur ce thème dans les meilleurs ateliers de tissage des anciens Pays-Bas (Bruxelles, Audenarde, Enghien, Anvers, Bruges, Tournai), en France, et dans la péninsule Italienne. Cette fortune du thème en tapisserie invite à s’interroger sur le sens particulier que lui donnaient les princes, destinataires privilégiés de ces tentures. Il ne fait pas de doute que, plus que tout autre héros, Hercule leur servait de modèle en ce qu’il incarnait la Virtus heroica, à savoir la « vertu active » constituée de courage, d’actes intrépides et d’érudition. Nous avons approfondi la question dans notre recherche doctorale en nous focalisant sur la période comprise entre le milieu du XVe siècle et les années 1560. Outre la quantité exceptionnelle des pièces conservées (une centaine), la multitude des mentions dans les inventaires et descriptions anciennes confirment l’importance de la thématique herculéenne à l’époque et laissent entrevoir la complexité de son iconographie. [less ▲]

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See detailDevelopment of a fully-partitioned PFEM-FEM approach for fluid-structure interaction problems characterized by free surfaces, large solid deformations, and strong added-mass effects
Cerquaglia, Marco Lucio ULiege

Doctoral thesis (2019)

Fluid-Structure Interaction (FSI) phenomena are encountered in many engineering applications and there is nowadays an increasing need for powerful numerical tools capable to efficiently model them. In ... [more ▼]

Fluid-Structure Interaction (FSI) phenomena are encountered in many engineering applications and there is nowadays an increasing need for powerful numerical tools capable to efficiently model them. In this work we address some critical features of the numerical simulation of such problems. In particular, the presence of free surfaces and of large solid displacements inside the fluid flow represents a major difficulty for traditional numerical approaches, often based on an Eulerian description of the fluid motion. The use of a Lagrangian approach for both the fluid and the solid parts allows to take these aspects into account in a natural way. However, in order to cope with mesh distortion issues typical of mesh-based Lagrangian approaches, a fairly recent meshless particle method, called Particle Finite Element Method (PFEM), has been implemented in a brand-new code and employed in this work to model the fluid. In the context of PFEM, a novel way to impose free-slip boundary conditions for moving boundaries of arbitrary geometry has also been developed during this PhD. The fluid and the solid solutions are then coupled through a fully partitioned approach, which allows to exploit all the features of the coupled solvers at their best. In particular, in this thesis the nonlinear Finite Element code Metafor, developed by the MN2L lab of the University of Liège, is used to model the solid part. Thanks to the use of a fully partitioned approach, all the nonlinear capabilities of Metafor, as for instance the contact management and the use of complex constitutive behaviors, are readily available. The coupling is made through CUPyDO, an integrated Python environment for FSI coupling developed from scratch during this PhD together with David Thomas, a researcher of the MTFC lab of the University of Liège. CUPyDO is able to couple virtually any solid and fluid solver and provides built-in advanced coupling strategies, and conjugate heat transfer, non-matching meshes and parallel capabilities. The main drawback of using a partitioned approach is that the asynchronous solution of the solid and fluid equations may induce numerical instabilities known as added mass effects. These effects become critical when the solid and fluid densities are close to each other. To cure this problem while preserving a fully partitioned approach, the Interface Quasi-Newton Inverse Least Squares (IQN-ILS) strategy has been used in this work to perform the PFEM-FEM coupling. Finally, the techniques developed during this PhD have been applied to the simulation of bird strike events on aeronautical structures, providing encouraging, though still preliminary, results. [less ▲]

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See detailDynamique du paysage de Kinshasa sous la pression de la périurbanisation: l'infrastructure verte comme moteur d'aménagement
Sambieni, Kouagou Raoul ULiege

Doctoral thesis (2019)

Like most African cities, which are currently the main focus of global urbanization, Kinshasa provides a convincing example of the urgent need to re-examine the logic of exploiting spaces and resources ... [more ▼]

Like most African cities, which are currently the main focus of global urbanization, Kinshasa provides a convincing example of the urgent need to re-examine the logic of exploiting spaces and resources. Indeed, the lack of planning in this city since Independence has led to its peri-urbanization characterized by increasing demographics and the dispersed and spontaneous occupation of the various geomorphological zones, suitable or not for construction. This has resulted in an environmental and landscape imbalance through environmental risks and damage such as erosion, flooding, pollution and other. It is thus clear that the challenge of urban and peri-urban development in Kinshasa is linked to improving the environmental quality of habitats. To do so, it is now recognized that it is necessary to calibrate and adapt management practices to natural and human resource conditions. In this perspective, this study is based on the central assumption that: the adaptation of the existing green system to the biophysical, socio-economic and cultural context, through the approach of the landscape, consisting in taking into account the quality of the environments and their appropriation by the inhabitants, opens up new perspectives for restoring the balances disrupted by the spatial transformations underway in the urban and peri-urban context of Kinshasa. The research was organized around three main objectives, namely: (i) to study the ongoing spatial transformations in the urban and peri-urban landscape; (ii) to determine the existing green potential in order to understand its uses and its representations in living practices and (iii) to study the contribution of the approach of the landscape in qualifying peri-urban habitats through plant engineering. The results show that Kinshasa's urban and peri-urban landscape is undergoing major spatial transformations to the detriment of vegetation cover. However, it should be noted that in the urban and peri-urban fabric, there are still residual green spaces and plant development practices in inhabited plots that could support environmental requalification. Based on this better knowledge of the landscape of Kinshasa, we carried out a specific study of a degraded site in Kisenso, one of the municipalities of Kinshasa, through an approach learned and developed within the "Ville-Territoire-Paysage" Laboratory of the University of Liège. This landscape approach, which we refer to as "reading and writing" of the territory, operationalizing the landscape approach, has enabled us to understand how to develop and/or set out possibilities of action. The latter rely on local plant dynamics to re-establish new interactions between natural resources and peri-urban settlements. This research thus shows, on the one hand, the relevance and necessity of integrating the "landscape" into the planning of African territories and, on the other hand, the importance of maintaining or establishing a green infrastructure, based on the slightest existing plant gap, in the context of widespread peri-urbanization. [less ▲]

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See detailTunable capillary adhesion inspired by nature
Gernay, Sophie-Marie ULiege

Doctoral thesis (2019)

Insects natural ability to walk upside-down and on any kind of substrate is the result of more than 300 million years of evolution. This highly efficient mechanism combines strong reliable adhesion, fast ... [more ▼]

Insects natural ability to walk upside-down and on any kind of substrate is the result of more than 300 million years of evolution. This highly efficient mechanism combines strong reliable adhesion, fast detachment, self-cleaning and wear resistance. It is based on the presence of micron-size slender structures coupled to a liquid secretion. The field of microtechnology struggles on the other hand to grasp and release components under the micron scale. The goal of this work is to draw inspiration from biological adhesion and to adapt those findings to artificial structures able to generate some similarly controlled adhesion. In this thesis we present our results regarding the quantification of the natural walk kinematics of the dock beetle, a model of elastocapillary equilibrium applied to the adhesion structures of the dock beetle, a replication of this elastocapillary equilibrium with artificial structures and two techniques of microfabrication that can be used to generate similar structures. [less ▲]

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See detailLocal and centralized control of multi-terminal DC grids for secure operation of combined AC/DC systems
Papangelis, Lampros ULiege

Doctoral thesis (2018)

High Voltage Direct Current (HVDC) transmission has become increasingly popular in the recent years, fueled by the shift to renewable energy sources and the gradual decommissioning of conventional power ... [more ▼]

High Voltage Direct Current (HVDC) transmission has become increasingly popular in the recent years, fueled by the shift to renewable energy sources and the gradual decommissioning of conventional power plants. The vast majority of HVDC connections in the world consists of point-to-point links. The next step envisaged is the extension to Multi-Terminal DC (MTDC) grids. However, several challenges have to be first addressed, one of which is the secure operation of the combined AC/DC systems that are going to arise. This thesis proposes local and centralized control schemes in order to improve the security and to enhance the dynamic behavior of such systems, by taking advantage of the flexibility of the AC/DC converters. First, a hierarchical structure is proposed to control an MTDC grid, consisting of a primary, a secondary and a tertiary level. The primary level aims at adjusting the power of the Voltage Source Converters (VSC) connected to the MTDC grid in order to correct any power imbalances that might arise. The secondary level monitors the MTDC grid to alleviate system-wide violations and steer it towards a desired operating point. The role of the tertiary level is to minimize the losses in the MTDC grid and ensure its secure operation after the loss of any single component. Next, the issue of frequency support among asynchronous AC systems is explored. Since more and more conventional power plants are decommissioned in favor of new power electronics-interfaced generation, AC frequency control may become critical in the future. Two decentralized control schemes are proposed in this thesis. The VSCs are equipped with the proposed controllers and react to important frequency deviation to either provide a pre-defined participation to frequency support or to keep frequency inside a desired range. In both cases, constraints imposed by the DC grid are respected. Last but not least, a framework for the security assessment of combined AC/DC grid is outlined. The control flexibility offered by MTDC grids must be taken into consideration when investigating corrective control actions against a set of credible contingencies. The framework highlights the need for cooperation and exchange of relevant information between the TSOs connected to the same MTDC grid, in order to avoid conflicts between them and ensure the security of the combined AC/DC system. [less ▲]

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See detailMolecular breeding and gene function verifying for cucumber fruit traits
Hu, Bowen ULiege

Doctoral thesis (2018)

Cucumber is a widely cultivated vegetable with high economic benefit. The assembled draft genome sequence and variation map generated by deep resequencing provided big data to advantage cucumber serving ... [more ▼]

Cucumber is a widely cultivated vegetable with high economic benefit. The assembled draft genome sequence and variation map generated by deep resequencing provided big data to advantage cucumber serving as the model plant for sex determination, long-distance trafficking and plant viruses disease research. However, the underlying molecular basis of some important horticultural traits, such as peel color, is still unknown. Besides, Cucurbitaceous species are well known to be one of the most refractory plants for transformation, which makes many meaningful traits hardly to be verified reliably in cucumber by reverse genetics, or makes identified gene cannot be applied well in molecular breeding. In this dissertation, the classical research methods of forward genetics and reward genetics was adopted. Initially, we discovered a cucumber mutant showing distinct light green exocarp of immature fruit from our EMS mutant library. By combining bulked-segregant analysis (BSA) and transient RNA interference, we first identified Csa7G051430 responsible for light green skin. Additionally, we successfully obtained transgenic cucumber using an inbred line rather than an F1 hybrid as previously used. We further optimized the CRISPR/Cas9 system by using stronger CsU6 promoter and a GFP tag to facilitate selection both the transformants and transgene-free mutants among the progeny. Thirdly, with these optimized procedures, we first verified the gene function of CsWIP1 which plays an important role in sex determination in cucumber and generated transgene-free gynoecious cucumber plants from a commercially valuable inbred line. The main contents and results are as follows: (1) An accumulation and replication of chloroplasts 5 gene mutation A mutant showing light green exocarp was discovered from ethylmethane sulfonate (EMS) mutagenized cucumber line 406 with dark green exocarp. Genetic analysis showed the mutant phenotype is conferred by a single recessive gene, here designated as lgp (light green peel). By re-sequencing of bulked segregants, we identified the candidate gene Csa7G051430 encoding ACCUMULATION AND REPLICATION OF CHLOROPLASTS 5 (ARC5) that plays a vital role in chloroplast division in Arabidopsis. A single nucleotide polymorphism (SNP) causing amino acid alteration in the conserved GTPase domain of Csa7G051430 showed co-segregation with the altered phenotype. Furthermore, a transient RNA interference of this gene resulted in reduced number and enlarged size of chloroplasts, which were also observed in the lgp mutant. These evidences support that the non-synonymous SNP in Csa7G051430 is the causative mutation for the light green peel. This study provides a new allele for cucumber breeding for light green fruits and additional resource for the study of chloroplast development. (2) Improving transformation protocol and optimizing CRISPR/Cas9 system in cucumber To find a way to improve the genetic transformation efficiency, GFP (green fluorescent protein) was used as a reporter during Agrobacterium infection and in situ hybridization of CsSTM was carried out. The result suggested the regenerated adventitious shoot was originate from cells in deeper layers where Agrobacterium can barely arrived by immerse infection. To enhance infection, a simple syringe was used for vacuum infiltration. Additionally, hemin was used to promote the rooting of transgenic shoots, which solved the problem that addition of auxin promoted chlorosis of the transgenic shoots. The transformation protocol established in this study was used to perform CRISPR/Cas9-mediated knocking out of three genes and the transformation efficiency approached 1.00‰. Aside from cucumber, the transgenic and genome-editing approach has been validated in melon, so it would be possible that this approach can be widely used in Cucurbitaceae species. (3) Engineering non-transgenic gynoecious cucumber using CRISPR/Cas9 system We verified the function of an important sex determination gene CsWIP1 and obtained transgene-free gynoecious cucumber by utilizing the improved efficient transformation protocol and optimized CRISPR/Cas9 system. Cswip1 T0 mutants displayed gynoecious phenotype, with the upper nodes bearing only female flowers, which indicated CsWIP1 acts as an inhibitor of carpel development in cucumber. Three types of deletions were found in T0 plant line 4 which displayed a high mutation rate 64.3% without off target. Homozygous and transgene-free Cswip1 T2 mutants were obtained from self-pollinating of heterozygous T1 mutants generated by crossing-pollinating between T0 and wild-type. Compared with monoecious wild-type plants, the Cswip1 mutants had seven times female flowers more than wild-type. Development of gynoecious cucumber by transgenic approach provide a stable and fast strategy to convert monoecious lines to gynoecious lines. [less ▲]

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See detailL'image exposée. La représentation des photographies de l'Agence France-Presse sur les réseaux sociaux numériques
Fabre, Maxime ULiege

Doctoral thesis (2018)

Le cliché d’une « barquette de frites nappées de chocolat », un « coucher de soleil » aux couleurs saturées près de Puerto Natales au Chili… Cette thèse a pour objectif d’étudier la représentation des ... [more ▼]

Le cliché d’une « barquette de frites nappées de chocolat », un « coucher de soleil » aux couleurs saturées près de Puerto Natales au Chili… Cette thèse a pour objectif d’étudier la représentation des photographies exposées par l’Agence France-Presse sur les « réseaux sociaux » – Instagram, Facebook, Twitter et Tumblr en têtes –, à l’aune d’une réflexion sur les transformations et les mutations des pratiques photojournalistiques en régime « numérique ». L’étude se divise en deux axes : une approche sémiotique d’abord, qui permet de comprendre de quelle manière le discours photojournalistique déploie les conditions formelles et médiatiques qui président à la fixation de la croyance, et articulent des normes et des attentes sur le statut de vérité du monde présenté par ces images ; une approche généalogique ensuite, qui étudie les conditions selon lesquelles les photographies de presse sont exposées. En réinterrogeant le concept de banalité, en lui redonnant son sens premier, ce deuxième axe développe une réflexion sur la complexité de la médiation « numérique », entre le pouvoir de réquisition des « industries du passage » d’un côté, et l’adaptation du discours informationnel de l’AFP de l’autre. À partir d’un point de vue nettement interdisciplinaire, la thèse prouve ici qu’il est possible de comprendre la médiation « numérique » comme la corrélation expressive entre l’économie d’un dispositif et le développement de formes de vies iconiques singulières. [less ▲]

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See detailLCA of building materials that include a biobased binder: lessons and challenges
Gerbinet, Saïcha ULiege

Doctoral thesis (2018)

Detailed reference viewed: 56 (14 ULiège)
See detailSynthesis and AFM-based Single-Molecule Force Spectroscopy of Helical Aromatic Oligoamide foldamers
Devaux, Floriane ULiege

Doctoral thesis (2018)

In this work, we describe the synthesis of aromatic oligoamide foldamers designed for AFM-based single-molecule force spectroscopy (SMFS) and the detailed investigation of their mechanical properties by ... [more ▼]

In this work, we describe the synthesis of aromatic oligoamide foldamers designed for AFM-based single-molecule force spectroscopy (SMFS) and the detailed investigation of their mechanical properties by this technique. The aim of the thesis was to gain insights into the forces governing the folding and the mechanochemical properties of synthetic folded molecules. We designed and studied three different kinds of helical foldamers to investigate the influence of the size of the foldamer and of the chemical architecture on the mechanical properties at the level of the single molecule in organic solvents. Pulling experiments on quinoline-based foldamers of four different sizes revealed a characteristic unfolding pattern, consistent with the sequential opening of the same groups of interactions involved in the helical conformation. The length of the unfolding patterns is proportional to the foldamer size, while the average unfolding forces show non-linear force dependence. This result highlighted the cooperativity of the interactions originating from the chemical sequence in the folding. From pulling-relaxing SMFS experiments, we evaluated the unfolding free energies and evidenced the capacity of the unfolded molecules to rapidly refold under the mechanical load. Together with experiments in different solvents, these results demonstrate the high robustness of this class of foldamers. SMFS experiments on the naphthyridine-constituted foldamer confirmed its helical structure and suggested that the strength of the interactions along the foldamer are weaker for a wider helix. The insertion of a methylene bridge in the aromatic oligoamide sequence showed a substantial effect on the mechanical properties. The aliphatic junction indeed disrupts the interaction continuum in the helical conformation under load. Providing detailed characterizations down to the single-molecule level, which are complementary to the traditional ensemble experiments, we also showed that helically folded aromatic oligoamides are a genuine class of foldamers with very promising properties as building blocks for mechanized nanomachines. [less ▲]

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See detailMagnetocapillary Self-Assemblies: Interfacial Locomotion at Low Reynolds Number
Grosjean, Galien ULiege

Doctoral thesis (2018)

Les auto-assemblages magnétocapillaires se forment lorsque des particules ferromagnétiques douces sont déposées sur la surface d'un liquide et soumises à un champ d'induction. Ils émergent de la ... [more ▼]

Les auto-assemblages magnétocapillaires se forment lorsque des particules ferromagnétiques douces sont déposées sur la surface d'un liquide et soumises à un champ d'induction. Ils émergent de la compétition entre une interaction dipolaire magnétique et l'effet Cheerios, une force attractive due à la déformation du ménisque. Sous des champs variables, ces structures auto-assemblées nagent le long de l'interface. Grâce à leur simplicité conceptuelle, ils permettent de vérifier et d'étendre notre compréhension générale des micronageurs. Différents arrangements de particules peuvent être réalisés dans le but d'accomplir divers objectifs : du plus simple nageur unidimensionel à la plus complexe structure inspirée du vivant ; d'un nageur rapide et contrôlable à un transporteur de cargaison ou mélangeur de fluides. [less ▲]

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See detailBioinspired and Architectured Materials with Enhanced Mechanical Performance by Three-dimensional Printing
Zorzetto, Laura ULiege

Doctoral thesis (2018)

The tremendously rapid development of additive manufacturing technologies is enabling the fabrication of a new class of advanced materials, referred to as architectured materials. They have well defined ... [more ▼]

The tremendously rapid development of additive manufacturing technologies is enabling the fabrication of a new class of advanced materials, referred to as architectured materials. They have well defined internal structures at length scales which are smaller than the size of the components, but which are much larger than the length scales traditionally associated with the microstructures of materials (e.g. grain size, lattice constant, polymer chains). They feature a controlled internal architecture ranging from 100 µm to 100 mm, therefore bridging the gap between microstructure and component size. The design of new architectured materials can profit from the strategies followed by nature in load-bearing biological materials. This is the context of the present PhD research, where we focused on introducing nature’s design principles into synthetic architectured materials using 3D printing, with the final goal to prototype next-generation materials with enhanced mechanical efficiency and multifunctionality. We first considered cellular architectures, which are widespread in nature as well as in engineering thanks to the combination of low weight with high stiffness and strength. Cellular solids also allow to expand the design space, because by tuning internal architectures we can obtain many different mechanical responses according to specific requirements. Here, we investigated the combination of local positive and negative Poisson ratio phases inside a cellular structure to enhance the overall mechanical behavior. Specifically, we introduced into a regular hexagonal beam lattice, local defects in the form of auxetic inclusions. Auxetic materials possess negative Poisson ratio, i.e., they contract perpendicular to the compression direction. We demonstrated that the combination of positive and negative Poisson ratio subunits could lead to a remarkable stiffness enhancement in cellular solids due to the contrast in the local deformation modes without increasing relative density. In a subsequent study we focused on helix-reinforced composites. Arranging stiff helicoidal fibers into a soft matrix is a universal construction principle widely adopted in load-bearing biological materials as well as in traditional engineering composites. A common example is the wood cell wall, which has a multilayer tube-like structure, each layer featuring helicoidal cellulose fibers reinforcing a matrix of lignin and hemicellulose. Here, we 3D printed wood-like architectures having stiff polymeric helix-reinforcements embedded into softer rubbery matrix. By controlling the fiber winding angle and matrix compliance, we could program the mechanical response of our structures in terms of stiffness and energy absorption. We also demonstrated that adding thin outer and inner reinforcing layers to the main helicoidal structure, with small fibrous elements oriented perpendicular to the applied load as seen in the wood cell, could lead to a huge amplification of failure strength and energy absorption of the wood-inspired structures. The mechanical behavior of composite materials, both man-made and fabricated by nature, is largely controlled by internal interfaces. Therefore, we turned our attention to characterize interfaces fabricating during 3D printing. In polyjet 3D printing, discrete photopolymer droplets are deposited on a build tray, leveled off by a roller and cured by UV light. This technique has a huge potential for cost-effective manufacturing of high performance multimaterial composites with soft and stiff polymers combined in a countless variety of arrangements and linked through interfaces. However, in 3D polyjet printing the properties of the interface between different photopolymers are unknown. Here, by combing different experimental methods and computer simulations we indicated that, depending on the printing modality, a strong blending at the interfaces over a length scale much bigger than droplet size can occur. We also reported that interface properties are dominated by the harder polymer phase. Our results provide novel insights on the micro-scale behavior of 3D printed interfaces, which should be considered when designing multimaterial composites. Finally, the last work of this PhD relates to possible bioinspired strategy to improve failure resistance of bimaterial attachments. Biological interfaces between two dissimilar materials are usually not flat but show distinct patterns in the form of interdigitation. This is the case of the interface connecting soft tissues such as ligaments and tendons to bone. There, interdigitation is believed to enhance failure resistance. Here, we performed an experimental study based on 3D printing to investigate the impact of patterning at interfaces connecting two materials with a large mismatch of elastic properties similar to the one of tendon and bone. The failure behavior was studied on 3D printed bimaterial polymer samples featuring a single notch and subjected to tensile loading. Results showed that pattering bimaterial interfaces with a wavy profile can delay failure initiation and increase failure resistance with respect to flat interfaces. Furthermore, we performed a novel assessment of damage tolerance by 3D printing defects right at the interface and we proved that waviness also makes the interface less sensitive to pre-existing damage.In conclusion, our work highlighted the possibility to use 3D printing in combination with computer simulations and experimental testing to design and prototype novel synthetic materials featuring biomechanical design principles of biological materials, which were replicated at higher length scales and using completely different building blocks. We analyzed different construction strategies ranging from cellular architectures to fiber reinforcements and we hope that our results shall guide the development of next generation architectured materials featuring locally tunable and heterogeneous properties, which could lead to unprecedented multiple functionalities. [less ▲]

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See detailHow to Support Environmental Protection Policy in Agriculture: A Case Study in Henan and Hebei Provinces, China
Yang, Xiaomei ULiege

Doctoral thesis (2018)

Crop straw (agricultural residue) is one of the most important biomass resources in China. Crop straw is either burned in the field or collected for recycling. Open burning of crop straw releases ... [more ▼]

Crop straw (agricultural residue) is one of the most important biomass resources in China. Crop straw is either burned in the field or collected for recycling. Open burning of crop straw releases particulate matter and gaseous pollutants, which play a key role in poor air quality, prompting heavy haze episodes during the harvest season. Such episodes threaten human health and interfere with social and economic activities. In contrast, recycling of crop straw reduces open burning and avoids its negative environmental impacts. In fact, improving the efficiency of straw use contributes to a circular economy, dedicated to reducing waste, while also making the best use of any ‘waste’ in economically viable processes that increase its value. Returning straw to agricultural fields in China is the easiest solution and the most important measure promoted by governments promising clean technologies to replace open burning. Recently, China’s municipalities have issued regulations forbidding outdoor burning of straw to reduce air pollution and have passed regulations to encourage farmers to use straw shredders during harvesting, and return crop straw as a bio-fertilizer. However, these regulations have not achieved the desired results, with ongoing open burning and reluctant use of straw on fields. In the first part of this research, urban residents’ willingness of to pay (WTP) for a corn straw ban in Henan (China) was assessed using contingent valuation in a face-to-face survey. Such assessments are important for policy makers to determine the investment and policy instruments for regulating the environmental impacts of straw open burning. The expected WTP analyzed using the Tobit model was about 77 RMB per person per year for the total respondents and 143 RMB per person per year for respondents with positive WTP bids. Aggregate values were between 3.4 and 3.9 billion RMB, suggesting that the corn straw burning ban is of considerable economic value in Henan. In the second part of this research, the factors affecting farmers’ willingness to participate in corn straw return and their willingness to accept compensation (WTA) were explored using a questionnaire survey and face-to-face interviews. A logistic regression model was used to assess adoption success, and the Tobit model was used for WTA analysis. High machinery costs, amount of straw returned, and slow decomposition rates of straw were the most significant factors negatively influencing adoption of this practice. They had a positive influence on the WTA. Poor quality of the straw was another significant factor reducing the probability of using straw return technology. Sown areas and soil improvements associated with adding straw wereoth positive factors determining adoption of the practice and negative determinants affecting WTA compensation. The mean WTA for the total respondent sample was 47 RMB per mu. In the third part of this research, a field experiment was carried out to compare the effects of tillage (minimum/full tillage) combined with corn straw return (mulching, incorporation, and removal) and irrigation (reduced/normal irrigation) methods on wheat productivity and water conservation. In 2013-2014, the yield for minimum tillage with residue mulch (MTm) was slightly but not significantly higher than the yield under full tillage with residue incorporation (FTi). Yields for MTm with reduced irrigation were 10.2% higher than FTi and reduced irrigation. The positive crop response to MTm may reflect higher topsoil moisture and soil temperature under MTm compared with FTi during winter. In conclusion, this study showed there is huge value to prohibiting open burning of corn straw to improve air quality. Despite machinery and operational problems that negatively influence farmers’ enthusiasm for straw return, minimum tillage coupled with corn straw return does benefit subsequent wheat yields. [less ▲]

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See detailStealth and pH-sensitive lipid nanocapsules : targeting the tumor microenvionement of melanoma
Pautu, Vincent ULiege

Doctoral thesis (2018)

Tumor acidity has been shown to play a major role in resistance to chemotherapy. The use of nanomedicines, as lipid nanocapsules (LNC), allows to protect drugs from this acidic environment. They can also ... [more ▼]

Tumor acidity has been shown to play a major role in resistance to chemotherapy. The use of nanomedicines, as lipid nanocapsules (LNC), allows to protect drugs from this acidic environment. They can also improve the biodistribution of therapeutics and to target the tumor environment. The aim of this thesis concerns the evaluation and characterization of stealth and pH-sensitive LNC in the context of melanoma. Firstly, these works consisted in characterizing the vascularization of human and mice melanoma. These studies allowed to compare different tumors (density, size and structure), and determine if the used of nanocarrier is suitable in the context of melanoma. The second part of this thesis described the development and the characterization of new copolymers, combining stealth and pH-sensitive properties. These copolymers, composed of N-vinylpyrrolidone (NVP) and vinylimidazole, were synthesized by RAFT polymerization and were post-inserted onto LNC surface. These modifications allowed to obtain charge reversal nanocarriers, leading to increase their melanoma cell uptake under acid pH. Finally, biodistribution of these modified nanoparticles was studied in vivo and highlighted the interest of NVP in the development of stealth nanocarriers. To conclude, the developed copolymers able to extend nanocarrier circulation time and to provide pH-responsive properties which should increase the tumor internalization of LNC in vivo and potentiate the effect of anticancer drugs. [less ▲]

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See detailRégulation du facteur tissulaire par la vimentine lors des processus de transition épithélio-mésenchymateuse : impact pour la progression métastatique
Francart, Marie-Emilie ULiege

Doctoral thesis (2018)

Au cours de la propagation métastatique, des cellules tumorales circulantes (CTC) sont libérées dans la circulation sanguine, dont seule une faible proportion seront capables de former des métastases ... [more ▼]

Au cours de la propagation métastatique, des cellules tumorales circulantes (CTC) sont libérées dans la circulation sanguine, dont seule une faible proportion seront capables de former des métastases détectables. La contribution des processus de transition épithélio-mésenchymateuse (TEM) à la biologie des CTCs représente aujourd'hui une hypothèse plausible étayée par une littérature abondante, associant la TEM à des propriétés de survie plus élevées mais aussi plus invasives et plus métastatiques. Le sang représente un aspect important de la biologie des CTCs puisqu’elles y rencontrent un nouvel environnement particulièrement hostile. De plus, les données de la littérature et du laboratoire suggèrent une contribution du système de coagulation dans les premières étapes de la propagation métastatique (survie, persistance, arrêt et extravasation). Au cours de cette thèse de doctorat, nous avons démontré que les voies de la TEM induisent l’expression du facteur tissulaire (FT) (un activateur majeur de la cascade de la coagulation) dans les cellules tumorales. Nous avons montré que cet axe de régulation TEM / FT conférait aux CTCs TEM+ des propriétés procoagulantes et une capacité accrue à survivre dans la circulation sanguine et à nicher dans les organes colonisés une fois injectées par voie intraveineuse à des souris. Nous avons identifié la vimentine en tant que régulateur potentiel du FT et nous avons donc examiné son implication dans cet axe TEM / FT / coagulation. Nous avons ainsi montré que l’inhibition de la vimentine diminuait l'expression de la protéine du FT. Nous avons également démontré que la transfection de siARN dirigés contre la vimentine diminuait les propriétés coagulantes in vitro et les métastases précoces lors d’injection par voie intraveineuse à des souris. Pour décrypter les mécanismes moléculaires impliqués dans la régulation du FT par la vimentine, des expériences au cours du temps ont révélé une inhibition de l'ARNm du FT dès 4h après transfection d’un siARN dirigé contre la vimentine. Nous avons également montré que la vimentine pouvait interagir avec l'ARNm du FT et le stabiliser. Jusqu'ici, nos données soutiennent un mécanisme par lequel la vimentine pourrait interagir avec la région 3'UTR de l’ARNm du FT, empêchant ainsi un mécanisme de régulation impliquant la famille miR-520. Pris dans leur ensemble, nos résultats renforcent une implication fonctionnelle de la vimentine dans l’axe de régulation TEM / FT et qui pourrait réguler et stabiliser l'ARNm du FT en se liant à son 3’UTR interférant avec une régulation négative de miARNs favorisant ainsi les métastases précoces dépendantes de la coagulation. [less ▲]

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See detailSynthèse et application de complexes organométalliques et d’hétérocycles dérivés de sulfonamides
Etse, Koffi Senam ULiege

Doctoral thesis (2018)

Ces dernières décennies, la synthèse de nouveaux composés aux structures toujours plus complexes n’a cessé de progresser grâce aux apports de la catalyse. Que ce soit par la formation de liaisons C―C, C―N ... [more ▼]

Ces dernières décennies, la synthèse de nouveaux composés aux structures toujours plus complexes n’a cessé de progresser grâce aux apports de la catalyse. Que ce soit par la formation de liaisons C―C, C―N et C―O, la réduction de composés carbonylés ou l’oxydation des alcools, les complexes de métaux de transition se sont montrés très efficaces dans l’amélioration des réactions. La polyvalence des complexes à base de palladium a plusieurs fois été démontrée et c’est dans ce sens que les travaux de Richard F. Heck, Ei-ichi Negishi et Akira Suzuki ont été récompensés en 2010 par le Prix Nobel de Chimie pour le développement de couplages catalysés par le palladium en synthèse organique. Notre ambition visait initialement à développer une nouvelle famille de carbènes N-hétérocycliques dérivés de sels de benzothiadiazine comme ligands pour des complexes de métaux de transition. Suite aux échecs répétés en matière de cyclisation, ce projet a été réorienté afin de valoriser les intermédiaires formés. Ainsi, dans cette thèse, nous avons étudié plusieurs approches centrées sur les sulfonamides, la synthèse de complexes de palladium et la formation de nouveaux hétérocycles par voie catalytique. En nous intéressant aux benzoisothiazoles, nous avons décrit l’état de l’art et diverses avancées dans la synthèse de sultames. Nous avons poursuivi en rappelant des grandes réactions catalysées par les complexes de palladium et l’influence des ligands sur l’activité de ces complexes. Pour conclure l’introduction, nous avons souligné l’intérêt des complexes organométalliques en biologie et leur possible potentiel comme matériau d’électrode dans les batteries au lithium. Dans le premier chapitre, afin de mettre au point une voie de synthèse des dibenzoisothiazines, nous avons développé une nouvelle méthode de synthèse des N-sulfonylformamides portant des substituants alkyle et aryle. Ces composés sont des intermédiaires pour la synthèse des ynamides. La préparation des N-sulfonyl-formamides procède par une étape de déprotonation des formamides par le n-BuLi suivie de l’addition d’un chlorure de sulfonyle à -100 °C. Nous avons proposé un mécanisme qui permet d’expliquer la formation du produit désiré et des sous-produits. L’analyse par thermogravimétrie a montré que les N-sulfonylformamides sont stables dans une large gamme de température et ne subissent pas de perte du groupe carbonyle avant leur décomposition complète. Après la mise au point de cette réaction et l’obtention de l’ynamide, la synthèse des benzoisothiazoles catalysée par des complexes de palladium a fait l’objet du Chapitre II. En effet, en nous basant sur la méthode de synthèse des carbazoles décrite par Witulski, nous avons imaginé la synthèse de dibenzoisothiazines par une réaction de cycloaddition entre un diyne et un alcyne libre. Les tentatives de synthèse du diyne ont conduit dans les conditions classiques du couplage de Sonogashira au 3-ylidène-dihydrobenzo[d]isothiazole 1,1-dioxide substitué par un alcyne. Ces ènynes présentent une architecture originale et sont potentiellement des composés bioactifs. Nous avons montré que cette réaction procède par un mécanisme de type tandem Heck–Sonogashira et peut être étendue à plusieurs alcynes terminaux. Dans le Chapitre III, l’activation de la liaison C―X caractéristique du couplage de Heck–Sonogashira a ouvert la voie à la synthèse de nouveaux complexes. A cet effet, nous avons valorisé une série de 2-halogénobenzènesulfonamides comme ligands pour la synthèse de complexes de palladium. Plusieurs complexes ont été obtenus par addition oxydante sur le complexe Pd(PPh3)4. L’étude du produit par RMN du proton et du phosphore démontre que, bien que l’isomère trans soit le plus stable et le plus abondant, l’isomère cis est également formé mais de façon minoritaire. Nous avons aussi observé que plus l’encombrement stérique du substituant sulfonamide porté par le ligand aryle est grand, plus la forme cis est favorisée. Après cristallisation, seule la structure moléculaire des isomères trans a été obtenue par diffraction des rayons X. Ces complexes ont montré une bonne activité catalytique dans la réaction de cyclopropanation du styrène et les résultats ont montré que les complexes portant des ligands brome et arylsulfonamides encombrés stériquement sont plus efficaces dans cette réaction. L’activation de la liaison C―I mise au point dans le chapitre précédent a été mise à profit pour la synthèse d’une série de complexes de formule générale [PdX(PPh3)2(4-RC6H4)], R étant H, OMe et OAc. Grâce à la modification du ligand aryle, seule la forme trans est obtenue attestant de complexes isomériquement purs et adaptés à des études biochimiques. La méthode de synthèse décrite par Flemming pour les complexes bromés et chlorés a été améliorée en réalisant la réaction one-pot dans un milieu biphasique eau/toluène, ce qui ne nécessite alors qu’une faible quantité de KBr et KCl. L’étude de l’activité antiradicalaire de ces complexes a été réalisée en utilisant deux tests chimiques (ABTS et DPPH) et un système enzymatique HRP-H2O2/L-012. L’ensemble des résultats montre que les complexes [PdX(PPh3)2(4-MeOC6H4)] avec X = I, Br et Cl possèdent une très bonne activité antioxydante et antiradicalaire. Par contre, les résultats ne permettent pas de mettre en évidence l’effet de l’halogène sur le pouvoir antioxydant de ces complexes. Une étude cinétique a révélé que les molécules synthétisées réagissaient plus rapidement avec le radical DPPH• qu’avec le radical cation ABTS•+ et que le mécanisme impliqué dans la réaction variait suivant le radical. L’étude cinétique a aussi permis de mieux évaluer et de classer l’activité de ces composés. Dans le dernier chapitre de la première partie, la stabilité et les processus rédox mis en évidence par trois des complexes étudiés au chapitre précédent, à savoir [PdI(PPh3)2(4-AcOC6H4)], [PdBr(PPh3)2(4-AcOC6H4)] et [PdCl(PPh3)2(4-AcOC6H4)], ont été mis à profit en les étudiant en tant que matériaux pour électrode des batteries au lithium. Les complexes iodé, bromé et chloré fournissent une capacité irréversible respectivement de 1089, 444 et 684 mA.h.g-1 lors de la première décharge. Les résultats ont aussi montré que le complexe [PdI(PPh3)2(4-AcOC6H4)] présente la capacité spécifique la plus élevée avec une capacité de décharge réversible d’environ 170 mA.h.g-1 après 200 cycles continus à une densité de courant de 50 mA.g-1. En plus, l’ensemble des complexes montre une rétention très intéressante de capacité au-delà de 200 cycles. Dans la deuxième partie de cette thèse, nous nous sommes intéressés aux dérivés de benzodioxoles et des dicétopipérazines comme intermédiaires vers la première synthèse totale du brasiliamide. Ainsi, dans le Chapitre VI, nous avons mis au point une voie de synthèse de l’acide 2-amino-3-(7-méthoxybenzo[d][1,3]dioxol-5-yl) propanoïque, un précurseur biosynthétique des brasiliamides. Les tests biochimiques révèlent que ce composé et certains de ses précurseurs possèdent une activité antiradicalaire vis-à-vis du radical DPPH• et peuvent inhiber efficacement la réaction d’oxydation de la HRP induite par les ROS. De plus, les résultats cellulaires montrent que l’acide 2-amino-3-(7-méthoxybenzo[d][1,3]dioxol-5-yl)propanoïque peut empêcher la production des ROS chez la souche cellulaire HL-60 sans pour autant être une molécule cytotoxique. Enfin, le dernier chapitre de cette thèse a été consacré à des études préliminaires de la condensation de deux acides aminés en vue de la synthèse des brasiliamides. Ainsi, la synthèse et l’étude conformationnelle de la 1,4-diacétyl-3,6-bis(phénylméthyl) pipérazine-2,5-dione ont été réalisées. La structure moléculaire obtenue par diffraction des rayons X a montré que la molécule est centrosymétrique et les paramètres de Cremer et Pople révèlent que le cycle dicétopipérazine adopte une conformation chaise écrasée. Les données cristallographiques ont ensuite été comparées à celles obtenues par calcul théorique en phase gazeuse. Parmi les trois conformations les plus stables, une seule présente la même disposition des groupes benzyle autour du cycle dicétopipérazine montrant que l’adoption de cette conformation est la force motrice de l’inversion de stéréochimie d’un résidu phénylalanine. [less ▲]

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See detailRestauration écologique en carrière, habitats analogues et résistances aux invasions végétales
Pitz, Carline ULiege

Doctoral thesis (2018)

Growing concern over the continued global loss of biodiversity has led to increased efforts for biodiversity conservation and restoration in anthropogenic ecosystems. Mining activities and introduction of ... [more ▼]

Growing concern over the continued global loss of biodiversity has led to increased efforts for biodiversity conservation and restoration in anthropogenic ecosystems. Mining activities and introduction of exotic species are listed as two of the seven major causes of human disturbance. Many studies have shown that adequate quarry management can significantly improve biodiversity. On the other hand, it is generally accepted that the choice of an appropriate target ecosystem is a decisive factor in the success of any restoration program, particularly in anthropogenic ecosystems. One of the major challenges in these novel ecosystems is to identify to which natural habitat they can be analogous (to define new restoration targets) and to deepen our understanding of the ecological (taxonomic and functional) succession that is naturally taking place in these human ecosystems, in order to know how and under which circumstances can restoration programs rely on spontaneous succession to sufficiently develop the target habitat (passive restoration) and when and to what extent human intervention is more effective (active restoration). In this thesis, we studied the assumption that dry zones of calcareous quarries could be analogous to semi-natural grasslands, and that these natural habitats could be used as restoration target of these dry zones. We based our reasoning on this same premise to establish seed mixtures sown in active restoration, choosing a priori calcareous grasslands species, also because these communities have a dominance of species harboring stress-tolerance strategies, which are theoretically more adapted to this type of bare substrate. We examined plant communities’ types that spontaneously assemble in these dry areas, both taxonomically and functionally, and compared these communities to those of semi-natural reference habitats. To that purpose, we compared field inventories in dry areas of calcareous quarries in the Walloon Region with semi-natural grasslands references vegetation. We also tested the installation of seed mixtures of semi-natural grassland species on different quarry substrates, by the establishment of experimental tests in three quarries of the Walloon Region. The various studies carried out during this thesis allowed the evaluation of passive and active restoration on dry zones of calcareous quarries. They allowed putting into perspective implications for quarry management, in several areas tested through the thesis. White chalk or dolomite dry areas of limestone quarries can naturally be oriented by passive restoration to hay meadows, a community of interest throughout the Walloon Region. It has been demonstrated that on calcareous spoil heap, a technical improvement of the substrate by the addition of a large spectrum of granulometry raw spoil (0-30 mm), allows a considerable improvement of the capacity of grassland species to settle along with a better resistance to Buddleja davidii Franch invasion. Finally, on dry areas of hard limestone quarries, where plant assemblages naturally tend towards mesophilous calcareous grasslands, active interventions could be carried out to promote assemblages of species similar to species-rich temperate grasslands, which have a particularly high conservation value. To that purpose, several restorations options are practicable after exploitation, according to targeted temporality criteria, financial resources that can be allocated and long-term management resources. These techniques include: passive restoration after overcoming dispersion limits; technical improvement of the substrate by the addition of a large spectrum of granulometry raw spoil (0-30 mm) or mimicry of the natural succession by initiating processes with ruderal species. Furthermore, this thesis allowed to identify the main components of biodiversity that should be targeted in order to implement relevant and accepted by all restoration and management actions at European level, to promote and conserve biodiversity at a regional level. In any case, this thesis is a new contribution to the definition of potential analogous habitats in anthropogenic habitats, and to the knowledge of practical methods to optimize ecological restorations in these disturbed limestone quarries habitats, with a view to reaching a balance between installation of vegetation of interest for the conservation of biodiversity and resistance to plant invasions. [less ▲]

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See detailArchitecture et déconstruction, remises en jeu d'une rencontre: raconter, traduire, hériter.
Bodart, Céline ULiege

Doctoral thesis (2018)

Cette thèse s'adresse à un domaine de recherche nommé "architecture et philosophie". La spécificité de ce domaine s'inscrit dans la question d'une coordination possible entre ces deux disciplines. Afin de ... [more ▼]

Cette thèse s'adresse à un domaine de recherche nommé "architecture et philosophie". La spécificité de ce domaine s'inscrit dans la question d'une coordination possible entre ces deux disciplines. Afin de mieux comprendre ce à quoi tient ce "et", nous proposons de revenir sur un épisode singulier de son histoire: la rencontre entre la déconstruction derridienne et la culture architecturale anglo-américaine de la seconde moitié du 20e siècle. Trois parties composent la restitution de cette recherche. Premièrement, il s'agit d'étudier comment se raconte cette rencontre depuis différentes situations d'énonciation (anglo-américaine et francophone), afin de mettre en avant comment des réceptions et appropriations culturelles variées conditionnent des poursuites théoriques spécifiques. D'un milieu à l'autre, entre les versions d'une même histoire, il y a de l'écart. L'objet principal de la thèse est alors d'investir l'écart entre ces versions par la mise en traduction de certaines traces de son histoire (Wigley 1993; Kipnis 1997). La seconde partie propose d'expérimenter comment traduire aujourd'hui en français ce qu'ont produit les Derridean years de l'architecture. Enfin, il s'agit de reconsidérer l'héritage de cette rencontre comme un problème à construire, en vue de remettre en jeu l'histoire longue et oscillante de l'hospitalité des discours de l'architecture. Cette thèse est une focale construite sur un épisode de l'histoire récente. En proposant d'en expérimenter de nouveaux modes d'énonciation, nous soutenons l'hypothèse que ces modes spécifiques permettent de transformer et ré-engager notre attention sur les conditions de rencontre entre architecture et philosophie. [less ▲]

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See detailUpdating Failure Probability of a Welded Joint Considering Monitoring and Inspection - For Offshore Wind Turbine Substructures
Mai, Anh Quang ULiege

Doctoral thesis (2018)

Reliability assessment of existing offshore wind turbine (OWT) support structures taking advantage of historical data from inspection and monitoring is crucial for the optimisation of maintenance and life ... [more ▼]

Reliability assessment of existing offshore wind turbine (OWT) support structures taking advantage of historical data from inspection and monitoring is crucial for the optimisation of maintenance and life extension. In this thesis, the crack inspection data and the monitoring data are separately considered for updating failure probability of welded joints. Concerning crack inspection data, this thesis aims at finding advantages of using the fatigue assessment diagram (FAD) in the failure criteria for failure probability estimation and updating. The crack inspection results (no detection or detected) and possible immediate interventions (repair normally or perfectly) are considered. Failure probabilities are calculated using the FAD and then compared with those obtained from the usual critical crack size criteria. The simulation-based approach is used to calculate and update the failure probability. Crack depth and length are simulated simultaneously. The crack propagations are calculated using a bi- linear Paris’ law with stress-range value varying over time. Uncertainties come from the crack growth parameters, initial crack sizes, fracture toughness, yield and ultimate strengths, FAD formula, stress intensity factor, stress-range values, and the detectable crack size. By combining the fracture toughness with the crack size in the failure criteria, the results show that the estimated failure probability of the welded joint is significantly increased in comparison to the case where only critical crack size is considered in the LSF. In comparison with the failure criteria which includes both the critical crack size and fracture toughness, the FAD approach gives similar reliability results when the applied peak tensile stress is small. However, when the applied peak ten- sile stress is high (the ratio between applied peak tensile stress and yield strength is more than 65%), the FAD approach predicts higher failure probability values. The uncertainty in FAD does not significantly affect the predicted failure probability of the joint as compared to the uncertainties in the ultimate and yield strength. This is because the latter affects directly the cut-off location of the FAD curve where the plastic failure is defined. The FAD approach can be used to update failure probability considering crack inspections and intervention actions. The calculation shows that reliability of the welded joint increases when no crack is detected, or when a crack is detected and repaired. In comparison with a perfect repair, a normal repair assumption significantly reduces the reliability of the joint. With regard to the monitoring data, the research questions how to effectively incorporate the measured strain and the oceanographic data (wind, wave) for updating failure probability of a welded joint in fatigue failure mode. To answer the question, the monitoring data is used to update the characteristics of a random variable in the LSF. Consequently, the updated random variable is then used in a reliability analysis to obtain the updated failure probability. The limit state function (LSF) is based on the Miner’s rule and solved using the first order reliability method (FORM). The random variable used to update failure probability is the joint distribution of wind speed, wave height and wave period. The monitoring data consists of strain, 10-minute mean wind speed, significant wave height, and mean wave period. Fatigue damage is summed up from all load combinations, i.e. from all the discretized components of the joint distribution of wind and wave. The measured strain data is used to calculate fatigue damage in each load combination. The probability of each load combination is calculated us- ing its joint distribution, which in turn can be updated using monitoring data. The 10-minute mean wind speed is assumed to follow a Weibull distribution and can be updated using Bayesian approach. Assuming that the scale parameter is a nor- mally distributed random variable with unknown mean and standard deviation, the predictive distribution of this random variable becomes a student’s t-distribution. The proposed methodology has been applied to a monopile support structure of a wind farm in Belgium. The measured strain is used to find the potential hot-spot location. Stresses are derived at the hot-spot location for fatigue analyses. It is assumed that stress-ranges in each load combination follow a Weibull distribution. The stress-range distribution parameters are found by performing least squares fitting method on the fatigue damage. The results show that the Weibull distribution is generally not very good for fitting stress-ranges in each wind-speed bin for the considered data. However, the inte- grated fatigue damage for the considered load combination is quite accurate since it is the objective of the fitting procedure. The main influence on the remaining fatigue life is the magnitude of stress-ranges at the hot-spot. So the stress conentration factor, the interpolating factor (for example to obtain stresses at under water locations), the correction factor for corrosion effects (if any), and their uncer- tainties should be estimated with great care. The measured 10-minute wind speed data has a significant effect in adjusting the predicted probability of failure and eventually the remaining fatigue life. The duration of strain measurement should be long enough to be combined with oceanographic data. Longer strain measurement duration, greater number of parameters in the oceanographic data can be considered for the failure probability updating. [less ▲]

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See detailEarly life programming by prebiotics or ingredients rich in non-starch polysaccharides in broiler chickens and pigs: effects on growth performance, intestinal maturation and colonization
Li, Bing ULiege

Doctoral thesis (2018)

Prebiotics or ingredients rich in non-starch polysaccharides (NSPs) are often used to improve intestinal health aiming to reduce the use of antibiotics in today’s intensive management farms. These ... [more ▼]

Prebiotics or ingredients rich in non-starch polysaccharides (NSPs) are often used to improve intestinal health aiming to reduce the use of antibiotics in today’s intensive management farms. These ingredients display prebiotic effects when fermented in the large intestine. The maturation and colonization of the intestine starts soon after birth/hatch, and can be programmed by early life interventions, affecting their development even until adulthood. However, the effect of fermentable ingredients applied in the early life is so far poorly investigated. Therefore, we chose 2 popular fermentable ingredients: inulin, a mixture of oligomers and polymers of fructose and wheat bran, a feed ingredient containing high levels of NSPs to investigate their effects on growth performance, intestinal maturation and colonization during the early life in broiler chickens and pigs. In addition, we aimed to evaluate whether the early programming of these ingredients resulted in a lasting effect, when the supplementation was stopped. Moreover, we conducted a test on 4 feed ingredients (galacto oligosaccharides, acidic oligosaccharides, colostrum derivative, prototype oligosaccharides) in suckling piglets. Firstly, inulin and wheat bran were provided to broiler chickens separately or in combination to study their effects during the starter period (Chapter 2) or finisher period (Chapter 3). Per dietary treatment (inulin, wheat bran or the combination), chickens received this ingredient either during the entire rearing period or during the starter period only, aiming at investigating a lasting effect of a temporary supplementation. Inulin had a greater ability to shape the microbial fermentation during the starter period, as seen by Chapter 2. The inclusion of 2% inulin in the diet might have been too high for chickens as it did not affect body weight (BW) and gut morphology positively during the entire life. The beneficial effect on gut morphology when the supplementation was stopped might point to this over-dose too. In contrast, the beneficial effect of wheat ban was mainly on BW during the starter period, and this beneficial effect was lasting until slaughter age, suggesting that wheat bran might be a favourable ingredient during the starter period. It also reduced some potential pathogenic bacteria during the finisher period. The combination of inulin and wheat bran not only demonstrated certain properties of the individual supplemented ingredients, but also showed a synergistic effect, seen by its improved results of BW and gut morphology. Lasting effects of inulin and wheat bran were absent in our study, except for the BW in the wheat bran group. Secondly, we investigated the effect of inulin and wheat bran in pigs. In a first attempt, inulin and wheat bran were provided to suckling piglets in creep feed (Chapter 4). However, a low and uncontrolled intake of creep feed was observed, perturbating the interpretation of the results. Therefore, in a proof-of-concept experiment, in Chapter 5, different amounts of inulin (IN-0.5: 0.5 g/d inulin at birth, increasing weekly with 0.5 g/d inulin and IN-0.75: 0.75 g/d inulin at birth, increasing weekly with 0.75 g/d inulin) were provided to piglets orally during the suckling period. Thereafter, piglets were also reared during 3 weeks after weaning to evaluate the lasting effect induced by the early supplementation with inulin. A dose-effect of inulin was observed. Only IN-0.5 displayed prebiotic effects, improving the BW, the gut morphology, the SCFA profile in the large intestine and selected colonic bacteria. But both inulin-groups reduced gene expressions of some inflammatory markers to help piglets against inflammation. Only the BW and gut morphology were found to have a lasting effect when supplementation was stopped, but it could be just an accumulation of early advantages. Thirdly, we performed an experiment in suckling piglets with a company to test 4 feed ingredients, which belonged to oligosaccharides- and colostrums-derivatives (Chapter 6). All these ingredients improved the BW of piglets during the suckling period, but through the measurement of gene expressions of cytokines (acidic oligosaccharides and prototype oligosaccharides) and microbiota profile (galacto oligosaccharides and prototype oligosaccharides), we did not observe any alterations. In summary, this thesis increased the understanding of the early use of inulin, wheat bran, as well as the other potential prebiotic ingredients in broiler chickens and pigs, especially their effects during the early life. The supplementation of inulin and wheat bran improved growth performance and intestinal parameters in broiler chickens and pigs, but in a dose-dependent way, where an excess amount did not affect them positively. In addition, their prebiotic effects relied on the administration of inulin and wheat bran directly, suggesting no or a weak lasting effect. As for the feed ingredients of oligosaccharides- and colostrums-derivatives, all these ingredients improved the BW of suckling piglets, but did not affect immune response and microbial fermentation. Therefore, the prebiotics or ingredients rich in NSPs could display effects in the early life, however, the early programming of these ingredients did not induce a lasting effect. [less ▲]

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See detailUse of pesticides in Fresh Water Aquaculture in the Mekong Delta, Vietnam, and impacts on environment and food safety
Nguyen, Quoc Thinh ULiege

Doctoral thesis (2018)

The research “Use of pesticides in Fresh Water Aquaculture in the Mekong Delta, Vietnam, and impacts on environment and food safety” consisted of four sections. To evaluate the pressure of drugs and ... [more ▼]

The research “Use of pesticides in Fresh Water Aquaculture in the Mekong Delta, Vietnam, and impacts on environment and food safety” consisted of four sections. To evaluate the pressure of drugs and chemicals in the environment, two surveys were performed in the Mekong Delta. The first was focused on rice and rice-fish system and was conducted in 2009. The second, an in depth survey, conducted in 2013, focused on rice-fish, striped catfish and red-tilapia systems. Results showed that, for the rice-fish system, most rice fish farmers grew 2 rice crops and 1 fish crop per year. Pesticides were applied generally 3 times per crop. Farmers normally applied pesticides based on the recommended doses of producers. Chess 50WG (containing 500g/kg pymetrozine, produced by Syngenta, Vietnam), Bassa 50EC (containing 500g/L fenobucard, produced by Việt Thắng Bắc Giang (Vithaco), Vietnam) and Kinalux (containing 250g/L quinalphos, produced by United Phosphorus Ltd., India) were the most common used commercial pesticides in rice crop, rice-fish crop and distributors as well. According to the majority of the distributors, the use of pesticides will increase in future. The in-depth survey showed that much more active compounds were used in 2013 compared to 2009, but, all of the active compounds belonged to the approved list of Vietnamese government. Few farmers used chemicals during fish crop. Farmers reported their awareness towards the use of agrochemicals in terms of health effects. The survey showed that the farmers select an agrochemical based on their experience. The study on red-tilapia demonstrated that many different types of disinfectants and antimicrobials are used. Further, the cost-effectiveness of such pesticide use, especially for feed supplement products, antimicrobials and disinfectants, is questionable and should be assessed. There is an urgent need to improve the farmer’s knowledge and their access to advisory services on careful use of disinfectants and antimicrobials. All visited striped catfish farms applied drugs and chemicals with seven types of antibiotics during the fish production. Enrofloxacin, sulfamethoxazole and trimethoprim were reported to be the most used chemicals by farmers to treat Bacillary Necrosis of Pangasius (BNP). The survey and practical situation demonstrated that quinalphos, trifluralin and dichlorvos were commonly used in rice fish system and, consequently, may contaminate aquaculture products. A Gas chromatography – mass spectrometry (GC-MS) analytical method was developed and validated according to European guidelines (SANTE/11945/2015) for the determination of residues of those pesticides in water. The developed method was then optimized using a gas chromatography – electron capture detector (GC ECD) technique to make the method more applicable in Vietnam. The developed method was used to analyze water samples collected from the aquaculture system in April 2013, at the beginning of the rainy season. Results showed that only 9 % of the total water samples analyzed contained residues of quinalphos, but only in water from rice fish systems. The other two pesticides, trifluralin and dichlorvos, were not detected. A comparison between GC-MS and GC-ECD indicated that GC-ECD is less sensitive than GC-MS. However, for samples with concentrations detectable with both techniques, no significant difference was observed between the results obtained using both equipments GC-ECD and GC-MS. The next step was to determine the distribution and elimination of quinalphos, the active substance of a popular insecticide used in the Mekong Delta, according to the first survey. An experiment was set up in a rice-fish integrated system in Can Tho City, Vietnam. Quinalphos was applied twice in a dose of 42.5 g per 1000 m2, according to the producer recommendations. Samples (fish, water and sediment) were collected at time intervals and were analyzed by GC-ECD. The results showed that quinalphos residues in fish muscles were much higher than those in the water and the bioconcentration factor (logBCF) was above 2 for the fish. The half-lives, after the first and second quinalphos applications, were 12.2 and 11.1 days for sediment, 2.5 and 1.1 days for silver barb, 1.9 and 1.3 days for common carp, and 1.1 and 1.0 days for water, respectively. Finally, as a case study including 3 commonly used pesticides (quinalphos, trifluralin and dichlorvos), dioxins and one forbidden antibiotic (chloramphenicol), the risk for the consumer, linked to the chemical contamination of the aquaculture related environment was evaluated. Sediments samples were collected including 10 samples collected from catfish ponds in An Giang Province and 12 samples randomly collected from rice-fish systems in Can Tho City. Analytical results showed that 3 from the 13 water samples collected from rice field were contaminated with low levels of quinalphos (with concentrations of 0.11, 0.08 and 0.04 μg/L). The other investigated pesticides were not detected in any sample. For chloramphenicol (CAM) residues in fish samples, analysis was performed on 36 fish samples of catfish (18 samples included 9 from small scale and 9 from large scale systems), snakehead (9 samples) and climbing perch (9 samples) collected at the beginning, middle and at the end of culture period. Results showed that one sample of climbing perch and one sample of snakehead were contaminated with traces of CAM (concentrations of 0.17 and 0.19 µg/kg, respectively). It appeared that CAM was not detected in catfish samples neither from the beginning to the end of the crop, nor from small and large scale systems. Dioxins were not detected in any of the collected sediments samples. In order to assess the general risk for the Vietnamese consumer of fish, a survey was performed in Can Tho City, using a questionnaire designed to collect information. A large part of interviewees (77%) stated that they like to eat fish. The number of days of eating fish was 3.4 days per week. In this study, the average amount of fish consumption ranged between 90 and 140 g per day. It was shown that the daily intake of trifluralin of interviewed people was 0.05 µg/kg body weight/day. This level of exposure was much lower than the acceptable daily intake (ADI) (15 µg/kg/day) (EFSA, 2015). However, trifluralin has not been approved in EU, so the presence of residues of trifluralin in aquatic product, even if they cause no problem for the consumer, would be a problem for aquatic product export. [less ▲]

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See detailLessons from experimental infections with Bluetongue and Schmallenberg viruses in ruminants
Martinelle, Ludovic ULiege

Doctoral thesis (2018)

En août 2006, le sérotype 8 (BTV8) du virus de la fièvre catarrhale ovine (FCO) ou maladie de la langue bleue a été confirmé pour la première fois aux Pays-Bas. Celle-ci était caractérisée par une ... [more ▼]

En août 2006, le sérotype 8 (BTV8) du virus de la fièvre catarrhale ovine (FCO) ou maladie de la langue bleue a été confirmé pour la première fois aux Pays-Bas. Celle-ci était caractérisée par une sévérité inattendue chez les bovins, une expansion géographique sans précédent et une propagation épizootique efficace malgré l'absence du vecteur classique Culicoides imicola dans les zones touchées. En outre, le BTV8 européen a été le premier BTV de type sauvage dont la capacité à traverser la barrière placentaire et le potentiel tératogène ont pu être prouvés, ces caractéristiques étant jusque-là l’apanage des souches adaptées au laboratoire, comme les virus vaccinaux vivants modifiés. En novembre 2011, c’est un nouvel Orthobunyavirus (famille Peribunyaviridae) qui a été identifié. Le nouveau virus a été appelé virus de Schmallenberg (SBV), du nom de la ville allemande où il a été isolé la première fois. Outre des manifestations cliniques – très rares et modérées - observées occasionnellement chez les bovins adultes, le SBV a été surtout associé à des avortements, des mortinatalités et des malformations congénitales chez les agneaux, les veaux et les chevreaux. Le virus de la FCO et le SBV ont un pouvoir tératogène, partagent une zone d’émergence commune ainsi qu’un spectre d'hôtes et des espèces communes de vecteurs. Ils sont tous deux des arbovirus à ARN segmenté à l’origine non identifiée et ayant un impact sérieux sur le bétail. Ces aspects convergents justifient les travaux actuels visant à clarifier et à discuter plus spécifiquement la pathogenèse de ces deux maladies. Pour ce faire, six infections expérimentales de bovins ou de moutons ont été mises en place. La thèse présente est ainsi séparée en trois parties : 1) Contribution à la mise au point d'un modèle infectieux animal fiable et normalisé pour étudier la pathogenèse du virus de la FCO et du SBV chez les espèces cibles de ruminants (études 1 et 2) 2) Etudes de la pathogenèse et du potentiel tératogène du virus de FCO et du SBV chez des animaux gestants (études 3 et 4); 3) Évaluation de la réactivité croisée, de la super-infection et comparaison des sérotypes de BTV, avec un accent particulier sur les sérotypes du virus de la FCO historiquement présents en Europe continentale (études 5 et 6). L’étude 1 nous a permis de mettre en évidence qu’un virus de la FCO issu d’une culture cellulaire passée un nombre limité de fois constitue un inoculum tout à fait valable pour une reproduction adéquate de la maladie en conditions expérimentales. Dans l'étude 2, nous avons conclu que les voies d'inoculation sous-cutanée et intradermique étaient adaptées pour reproduire correctement une infection par le SBV similaire à une infection naturelle. Nous avons rapporté dans l'étude 3 des hémorragies de l'artère pulmonaire - considérée comme presque pathognomonique de l'infection par BTV - chez des veaux nés de mères infectées avant la mi-gestation, malgré l'absence d'ARNémie à la naissance. De même, dans l'étude 4, après l'infection de brebis à 45 ou 60 jours de gestation, aucun agneau n'a présenté de malformation évoquant une infection à SBV et aucun d'entre eux n'avait d'anticorps anti-SBV avant la prise de colostrum. Cependant, la plupart d'entre eux avaient au moins une structure placentaire ou extra-embryonnaire avec une détection positive de l'ARN du SBV. L'objectif principal de l'étude 5 était d'évaluer l'effet d'une surinfection par BTV1 chez des veaux naïfs ou vaccinés préalablement contre BTV8. L'inoculum s’est révélé être contaminé par BTV15. Nous avons ensuite caractérisé la co-infection BTV1-BTV15 en plus d'une comparaison BTV1 et BTV15 au cours de challenges infectieux à sérotype unique. Cette étude a fourni de nouvelles informations sur la protection hétérologue entre BTV1, BTV8 et BTV15 et sur leur adaptation au bétail. L'étude 6 décrit les paramètres cliniques, sérologiques et virologiques après les infections expérimentales de veaux avec 5 sérotypes européens de BTV (1, 2, 4, 9 et 16). Les expériences ont montré (i) la virulence limitée des souches virales sélectionnées pour les bovins, (ii) une réactivité croisée partielle, (iii) une faible protection croisée induite par la vaccination et/ou l’infection préalable contre BTV8. De plus, nous avons pu confirmer que les sérotypes de BTV sont adaptés différemment aux jeunes bovins (BTV1, 16 et 9 plus adaptés que 2 et 4). Les travaux présentés ici ont apporté de nouvelles données utiles à la conception des infections expérimentales avec BTV et SBV, à la pathogenèse des anomalies reproductives et aux relations sérologiques entre les sérotypes européens de BTV. Ces aspects sont finalement discutés à la lumière des données expérimentales les plus récentes. En dépit des contraintes de biosécurité, d’éthique animale et de cout, la valeur des données fournies et l'absence de modèles alternatifs reproduisant de manière adéquate la pathogenèse de BTV et de SBV prouvent que les infections expérimentales de ruminants restent incontournables dans ce contexte.   [less ▲]

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See detailClimate change in Belgium: recent and future evolution of global radiation and hydroclimatic conditions favouring floods using the regional climate model MAR
Wyard, Coraline ULiege

Doctoral thesis (2018)

In Belgium, the future response of the climate to increasing greenhouse gas concentration is not clear, especially with regard to the perturbations of the precipitation regime, snow cover, and global ... [more ▼]

In Belgium, the future response of the climate to increasing greenhouse gas concentration is not clear, especially with regard to the perturbations of the precipitation regime, snow cover, and global radiation. On the one hand, existing studies show results which differ strongly either according to the future scenario, or from one model to another. On the other hand, there is even an absence of studies focussing on Belgium regarding future changes in snow cover and global radiation. Given their potential impacts on the society (water management, energy supply, biodiversity, tourism), future changes in precipitation, snow cover, and global radiation require further research. As the orography, the exposition to the dominant winds, and the proximity of the North Sea determine a large spatial variability in the Belgian climate, the latter requires a fine representation of these features to be properly simulated. Compared to global climate models (GCM), regional climate models (RCM) are recognized for their ability to represent climatic phenomena with higher spatial resolutions. In the framework of this doctoral thesis, the RCM MAR (for "Modèle Atmosphérique Régional" in French), which is developed at the Laboratory of Climatology and Topoclimatology of the University of Liège, was applied for the first time to Belgium. The aim was first to assess the performances of MAR over Belgium and then to study the current and future evolution of hydroclimatic conditions favouring floods, and also the current and future evolution of global radiation. For this purpose, historical simulations were performed over 1959-2014. Future projections (2006-2100) were then performed under the most pessimist IPCC future scenario (RCP8.5). The horizontal resolution used for both historical and future simulations is 5 km. By comparing the MAR outputs to ground-based measurements from 20 weather stations over 2008-2014, the results show that MAR successfully simulates the spatial and temporal variability of the Belgian climate. In fact, the biases found in the MAR results are non-significant and the correlation coefficients are satisfying with regard to temperature, precipitation, snow height, global radiation and cloudiness. The MAR results are particularly satisfying during the winter months and in High Belgium where the climate is the coldest. Regarding hydroclimatic conditions favouring floods, we focused on the Ourthe catchment. In this river, about 70 % of floods occur during the winter months and result from either the rapid melting of the snow pack covering the Ardennes eventually combined with rainfall or abundant rainfall alone. The current evolution of hydroclimatic conditions favouring floods was first assessed for the period 1959-2010. Conditions favouring floods in the Ourthe River present a negative trend over 1959–2010 as a result of a decrease in snow accumulation and a shortening of the snow season. Regarding the impact of the evolution of extreme precipitation events on hydroclimatic conditions favouring floods, the signal is less clear because the trends depend on the data used to force the MAR model. By the end of the 21st century, under the most pessimist scenario, the results show an acceleration of the snow cover depletion resulting in a decrease in conditions favouring floods. Further, the impact of the evolution of extreme precipitation events on hydroclimatic conditions favouring floods, no significant change was found although these trends are subject to uncertainties due to the deficiencies of the convective scheme of MAR. Regarding global radiation, its current evolution was first assessed for the period 1959-2010. In addition, we consider two distinct periods in our analysis: 1959-1979 (dimming) and 1980-2010 (brightening). For both the dimming and the brightening periods, our results show that the annual global radiation trends are mainly driven by global radiation changes in spring and summer. The increase in global radiation observed in Belgium since the 1980s and especially since the 2000s could mainly be explained by a decrease in low and medium cloud cover. This would strengthen the effect of the decrease in aerosol load on global radiation that has been observed in Europe since the 1980s. The origin of these changes in cloudiness is not clear and could result from changes in both aerosol-cloud interactions and atmospheric-circulation, such as more frequent tropical air advections and more frequent anticyclonic conditions over Western Europe due to the poleward shift of extratropical storm tracks. These changes in the atmospheric circulation may result from global warming and may persist in the future. In fact, by the end of the 21st century, under the most pessimist scenario, the models simulate an increase in the blocking regime frequency in summer over Europe. For Belgium, this implies more frequent anticyclonic conditions favouring cloudless conditions. The future projections performed with MAR exhibit significant decreasing total cloud cover, and particularly decreasing low and medium cloud cover. However, this declining cloud cover leads to contrasting changes in global radiation depending on the data used to force MAR. [less ▲]

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See detailLa collection et la revue Poétique. Histoire intellectuelle, sociale et matérielle d'une discipline moderne (1970-1987)
Lorent, Fanny ULiege

Doctoral thesis (2018)

Cette thèse se veut un essai d’histoire intellectuelle, sociale et matérielle appliqué à une discipline moderne, la poétique. De la poétique, telle qu’elle a été refondée au tournant des années 1970 dans ... [more ▼]

Cette thèse se veut un essai d’histoire intellectuelle, sociale et matérielle appliqué à une discipline moderne, la poétique. De la poétique, telle qu’elle a été refondée au tournant des années 1970 dans le lointain sillage d’Aristote, ce travail n’entend pas donner le dernier mot sur la définition, les objets, les méthodes. Il s’agit plutôt de fournir la chronique, pas à pas, texte par texte, de la façon dont une telle appellation a été mobilisée dans le second XXe siècle dans deux lieux spécifiques : la revue et la collection « Poétique », fondées en 1970 par Gérard Genette, Tzvetan Todorov et Hélène Cixous, et publiées par les Éditions du Seuil. En effet, c’est un critère éditorial qui a régi, au départ, mon enquête. Subordonner de la sorte les savoirs disciplinaires à un découpage « matériel » m’a semblé le premier geste à poser pour se démarquer d’une histoire des idées abstraite et idéaliste. Les textes ne sont pas compris, dans ce travail, en tant qu’entités désincarnées, mais en tant qu’objets, livres, numéros de revue. Cet angle d’approche permet de mener une étude qui, sans négliger le contenu conceptuel des textes, inscrit ceux- ci dans l’ensemble de la chaîne sociale mobilisée pour produire et diffuser les objets dans lesquels ils se réalisent. Ces derniers, unités pertinentes de la présente thèse, s’offrent aux yeux des lecteurs sous certaines configurations graphiques, présentent une composition et une organisation signifiantes des contenus. En outre, ils sont produits par des auteurs (dont la formation, la nationalité, l’appartenance professionnelle, le réseau amical, etc. doivent être pris en compte), et circulent dans un espace social, dans une communauté savante spécifique, et parfois au-delà. Telles sont les diverses dimensions que j’ai souhaité tenir ensemble dans cette thèse, laquelle espère se situer à la croisée de l’histoire des idées, de l’histoire du livre et de l’édition, de la sociologie des intellectuels et de ce que l’on commence à nommer aujourd’hui, à la suite de Marie-Ève Thérenty, la poétique des supports. Cette chronique de la poétique dans et par Poétique et « Poétique » est organisée en quatre temps. Un long prologue, courant de 1963 à 1970, est destiné à saisir en acte la manière dont le terme poétique, après des années d’absence, est réapparu sur la scène intellectuelle, a circulé et s’est enfin stabilisé pour venir désigner le programme auquel la revue et la collection « Poétique » entendent répondre à leur fondation. Ensuite, trois chapitres correspondent aux restructurations internes de la revue et de la collection. Les trois périodes délimitées (1970- 1973 ; 1974-1978 ; 1979-1987) se soldent par le départ de Todorov de la direction de la collection. Si « Poétique » et Poétique sont toujours actives aujourd’hui, j’ai néanmoins choisi de me concentrer sur la période s’étendant de 1970 à 1987. Cruciales pour le paradigme structuraliste, ces années nous mènent des prémisses de la poétique moderne aux premiers moments de sa remise en cause par un retour de l’histoire littéraire. Elles permettent ainsi d’envisager comment la discipline s’est repensée, renouvelée sans cesse, pour survivre jusqu’à nos jours. [less ▲]

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See detailPancreatic Beta Cell Regeneration in Zebrafish : Investigation of the Ductal Contribution and Involved Molecular Mechanisms
Bergemann, David ULiege

Doctoral thesis (2018)

The pancreas, along with its major role in digestion, holds one of the most important cell type involved in glucose homeostasis : the insulin-producing β cell. Diabetes mellitus is characterized by a ... [more ▼]

The pancreas, along with its major role in digestion, holds one of the most important cell type involved in glucose homeostasis : the insulin-producing β cell. Diabetes mellitus is characterized by a disturbed blood glucose balance resulting from a lack or an inadequate secretion/action of insulin. A hallmark of diabetes is the loss of β cells either by an autoimmune destruction (T1D) or by an ongoing exhaustion and subsequent cell death associated with the inability to fit metabolic demands (T2D). As this disease has become a major burden in our modern society, efforts are needed to provide effective therapeutic strategies. While current strategies rely on exogenous insulin supply and glycemic control through medication, restoring a functional β cell pool represents the most promising solution to tackle the disease at its root. To this regard, regeneration studies have provided evidence that β cells can be produced by stimulating their replication or by (trans)differentiation of different cellular sources. In this work, we investigated the possibility that the pancreatic ductal compartment can be a source of regenerated β cells. In order to study regeneration and unravel underlying mechanisms, we conducted our work in the regeneration prone zebrafish model which was previously shown to regenerate its β cells in a very efficient manner. By using a combination of transgenic tools and deep RNA-sequencing, we were able to show that adult pancreatic duct cells display a progenitor-like behavior and that they constitute a source of regenerated β cells. We then used comparative transcriptomics in order to get an insight into the molecular mechanisms (gene regulation) occurring in the ductal cells during regeneration. This provided us with candidate signaling pathways and genes possibly involved in regeneration. To determine their importance in this process, we initiated functional studies by targeting pathways with pharmacological inhibitors/activators. Among the candidates, the Ca2+/calcineurin signaling axis seemed most promising and will be further investigated for its implication in regeneration. In parallel, we also underlined an important pro-endocrine role for the transcription factor ascl1b in β cell regeneration from the ducts. Lastly, this work prompted us to further improve the nitroreductase-mediated ablation system used in regeneration studies. Thus we characterized Nifurpirinol as a more potent substrate than the gold-standard prodrug Metronidazole which displayed suboptimal and variable cell ablation efficiencies. Altogether, our work strengthens the hypothesis that adult pancreatic ducts contain progenitors able to differentiate into β cells and provides new research leads regarding targetable signaling pathways and genes for the stimulation of β cell regeneration. Understanding the fundamentals of β cell regeneration taking place in zebrafish might thus pave the way towards stimulating these mechanisms in diabetic patients. [less ▲]

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See detailTargeted metabolomic study in Brassica napus L. under cadmium and epoxiconazole stress
Durenne, Bastien ULiege

Doctoral thesis (2018)

Investigations carried out during this thesis consisted in the research of volatile and non-volatile abiotic stress markers using winter oilseed rape (Brassica napus L.), a major crop worldwide. Two ... [more ▼]

Investigations carried out during this thesis consisted in the research of volatile and non-volatile abiotic stress markers using winter oilseed rape (Brassica napus L.), a major crop worldwide. Two specific abiotic stresses involved in current agricultural soil threats were studied such as cadmium (Cd), a carcinogen trace heavy metal, and epoxiconazole being a persistent systemic fungicide. A targeted metabolomic approach was therefore used through the analysis of volatile organic compounds (VOCs) profiles, targeting terpenoid compounds largely described in plant abiotic stress response, and through the profiling of glucosinolates (GSLs) as non-volatile sulfur-containing metabolites within Brassicaceae. A new glass device allowing the plantlets growth and the non-invasive dynamic sampling of emitted VOCs was successfully developed. It can be described as an innovative laboratory and high-throughput plant chambers system. Oilseed rape plantlets analysis was performed under sterile and controlled conditions, using in vitro medium in the case of experiments related to cadmium exposure and using perlite as a soil-similar substrate for testing epoxiconazole. A phenotyping based on plantlets observations and physiological measurements under cadmium and epoxiconazole stress: i) characteristic symptoms (chloroses), ii) root and shoot growth and iii) biomass was performed at vegetative stage, in complementarity with the targeted metabolomic approach. Different levels of stress were tested on oilseed rape plantlets through dose-response experiments in order to obtain a concentration gradient representing defined stress conditions (i.e. low, middle and severe). With respect to cadmium stress, the concentration of Cd and sulfur (S) has been also measured in the different plant organs such as roots and shoots. GSL profile and content in plantlet organs were also investigated in order to highlight their putative involvement in Cd stress tolerance. About epoxiconazole stress, a characterisation of molecule concentration in the plantlets was carried out before studying its impact on terpenes profiles and on the breakdown products of GSLs (i.e. isothiocyanates) as putative metabolic markers. Overall results showed that metabolic markers could be identified for both kinds of stress such as cadmium and epoxiconazole. These molecules were also involved in adaptive response of plantlets to stress. The sesquiterpenes clearly emerged from the experiments as VOC stress markers. In addition, the role of GSLs in the mechanisms of Cd-tolerance was highlighted with an emphasis on importance of oilseed rape primary S metabolism. The non-invasive method of rapid analysis of VOCs emitted by oilseed rape plantlets and terpenes quantitation could certainly be used for studying the relationships between plant-emitted VOCs and other abiotic or biotic stresses. Finally, this customised glass chambers system could be used in regards to other plants such as potatoes, sugar beets and vegetable crops using soil substrate in order to discover new putative metabolic markers. [less ▲]

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See detailThe Dynamics of Bank Business Models in the ASEAN Banking Sector
Oktofa Yudha Sudrajad, ULiege

Doctoral thesis (2018)

Prior to the global financial crisis in 2007/2008, the bank business model was moving away from traditional intermediation-based to more complex and sophisticated model such as trading and derivatives ... [more ▼]

Prior to the global financial crisis in 2007/2008, the bank business model was moving away from traditional intermediation-based to more complex and sophisticated model such as trading and derivatives activities. This migration is believed to have played a significant role in the onset of the global crisis. Afterward, banks shift back to the traditional business model again. The dynamics changes of bank business models attract researcher to make further investigation regarding this behavior. However, most of the studies were conducted in the context of developed countries and limited attention has been given to the banking sectors in emerging countries. Therefore, this thesis focuses on the empirical investigation of the business models evolution in the banking sectors in ASEAN country members as a representation of the emerging markets. The evolution of bank business models is evaluated by examining the determinants of bank business model transformations which consists of external and internal factors. Chapter three evaluates bank market power and chapter four investigates banking regulation, in which both factors represent external determinants that might affect bank business model transitions. Meanwhile, Chapter five examines the internal factors by using cost minimization objective of the banks as a measure. In addition to the drivers of bank business models evolution, we also investigate the relationship between bank business models and banking performance as well as banking risk in Chapter three and five. All in all, our findings suggest that bank business models in the ASEAN region evolve throughout time, indeed. We find strong evidence that external and internal factors affect the business model of the banks to a significant degree. However, our evidence shows the intermediation-based model as the bank business model equilibrium. In regard to the effect of business models on bank stability and performance, we reveal that stronger banks intermediate less and turn to alternative sources of business in order to enhance their financial situation, both from the performance and the stability sides. [less ▲]

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See detailEchanges de composés organiques volatils d'origine biogénique entre deux écosystèmes agricoles et l'atmosphère
Bachy, Aurélie ULiege

Doctoral thesis (2018)

Some volatile organic compounds (VOC) have a significant effect on climate and air quality. They are mainly or partially exchanged by terrestrial ecosystems, hence they are called BVOC for biogenic VOC ... [more ▼]

Some volatile organic compounds (VOC) have a significant effect on climate and air quality. They are mainly or partially exchanged by terrestrial ecosystems, hence they are called BVOC for biogenic VOC. Many studies were conducted in order to quantify and understand BVOC exchanges between these ecosystems and the atmosphere. However, so far croplands have been poorly studied yet, despite their importance in term of land use at the global scale. Therefore, this thesis focused on ecosystem-atmosphere BVOC exchanges for the two most important cultures worldwide, i.e. wheat and maize. Four objectives were pursued: - Qualify, - Quantify, - Understand the BVOC exchanges mechanisms for both cultures and - Evaluate the ability of up-scaling models (currently used by atmospheric chemistry models to simulate BVOC emissions from terrestrial ecosystems) to reproduce the BVOC exchanges observed in the framework of this thesis. For that purpose, three measurement campaigns were carried out at the Lonzée Terrestrial Observatory (LTO, Belgium): the first on a maize field, the second on a winter wheat field and the third on a bare soil. BVOC fluxes were measured at the ecosystem-scale by using the disjunct eddy covariance by mass scanning technique, with a mass spectrometer for BVOC ambient mixing ratio measurements, during the whole (maize) or the most part of the (winter wheat) growing season. These measurement campaigns are original especially because of their broad and high temporal coverage, which enabled to characterize all vegetation stages in situ and in details. Both the maize and the winter wheat field exchanged mainly methanol. The exchanges were bidirectional but the emissions were much more important than the uptakes. The fluxes were correlated with the temperature, the radiation and the water vapor fluxes. They were also triggered by plant phenology. In addition, the soil exchanged significant amounts of BVOC, methanol being the main exchanged compound. This result is original because it counteracts with the common assumption that soil BVOC exchanges are one to three orders of magnitude lower than plant BVOC exchanges. The soil methanol exchanges were driven by a physical adsorption-desorption process coupled with a methanol source which depended on soil surface temperature. They decreased along with the development of the canopy (leaf and above-ground biomass). Then, the tested up-scaling model was able to reproduce the methanol exchanges observed at LTO between the winter wheat field and the atmosphere when the canopy was well established, so that soil exchanges were reduced. Several parameters of the model were nevertheless strongly modified to adjust the model to the data; otherwise the model overestimated the exchanges by a factor of 3. Lastly, the BVOC exchange rates varied strongly between this study and the other studies conducted on croplands. More generally, we observed strong differences in BVOC exchange rates among all studies, and this even for the same cultivated crop species end under similar temperature, radiation and phenology conditions. Thanks to the two broad measurement campaigns which enabled the analysis of temporal BVOC flux dynamics as well as their relationships with the meteorological variables and the ecosystem (plant development – soil), this thesis brings original values for the exchanges rates, the BVOC budget and the parameters for up-scaling models. In addition, it highlighted or made possible to suggest some exchange mechanisms and this for the two main crops species worldwide, under a temperate climate, with a silty loam soil and conventional crop management techniques. These results should therefore help improving the performance of the models when estimating BVOC exchanges for that region, since they currently use parameters based on few representative species (in terms of cultivated surface) or default values (because of a lack of available flux data) for croplands. The factors causing the differences in BVOC exchanges rates for a same crop species and under similar meteorological and phenological conditions should nevertheless be better constrained. For that purpose we suggest comparing the BVOC exchanges from several wheat, maize and rice varieties, which are the three main crop species in the world, in terms of cultivated area, under various pedoclimatic conditions and crop management practices. Plant and soil BVOC exchanges should furthermore be disentangled, in order to better constrain the exchange rate differences observed at the ecosystem-scale. [less ▲]

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See detailEtude de protéines du divisome chez E. coli : caractérisation du sous-complexe FtsW-PBP3-PBP1b et du domaine AMIN de l'amidase AmiC
Leclercq, Sophie ULiege

Doctoral thesis (2018)

De nos jours beaucoup d’antibiotiques sont connus mais leur surconsommation conduit à l’émergence de souches bactériennes capables de résister à leur action, il est donc nécessaire de trouver de nouvelles ... [more ▼]

De nos jours beaucoup d’antibiotiques sont connus mais leur surconsommation conduit à l’émergence de souches bactériennes capables de résister à leur action, il est donc nécessaire de trouver de nouvelles cibles. Durant la division cellulaire bactérienne, la formation d’un septum de peptidoglycane (PG) par les synthases et le clivage de ce dernier par les amidases pour séparer les deux cellules filles sont deux étapes importantes, sous le contrôle d’un complexe multiprotéique appelé le divisome. Dans ce travail, nous avons étudié les interactions entre les protéines directement impliquées dans la synthèse du septum et l’effet de ces interactions sur celle-ci. Nous avons aussi essayé de déterminer le mécanisme d’interaction entre le PG et le domaine AMIN de l’amidase AmiC, ces processus étant des cibles potentielles pour le développement de nouveaux agents antibactériens. Chez E. coli, les enzymes directement responsables de la synthèse du PG septal sont la PBP3 et la PBP1b. Cette synthèse serait coordonnée avec l’activité encore mal définie (flippase et/ou transglycosylase) de FtsW et régulée par FtsN ainsi que d’autres protéines. FtsN joue également un rôle dans le maintien et la stabilité du divisome. Néanmoins, les mécanismes moléculaires exacts des fonctions de ces quatre protéines au sein du divisome sont mal connus. Dans ce travail, nous démontrons que FtsW interagit avec PBP1b et le lipide II mais aussi que PBP1b, FtsW et PBP3 forment un complexe ternaire. Nous démontrons également que la grande boucle entre les TM 7/8 de FtsW est importante pour l'interaction avec PBP3. De plus, nous avons mis en évidence une inhibition par FtsW de la polymérisation du lipide II en PG par PBP1b et que PBP3 lève cet effet inhibiteur. Ces résultats suggèrent que FtsW interagit avec le lipide II empêchant sa polymérisation par PBP1b et que PBP3 en interagissant avec FtsW facilite la libération du lipide II et/ou son transfert à PBP1b. Ce mécanisme de régulation étroit est compatible avec le besoin de la cellule d'assurer une utilisation appropriée du stock limité de lipide II. Le septum une fois formé divise la cellule et doit être clivé pour permettre la séparation des cellules filles et la maturation des nouveaux pôles cellulaires. Les amidases dont AmiC sont responsables de la scission et la répartition du septum entre les deux nouveaux pôles des cellules filles. Ces enzymes sont activées de manière spécifique par des protéines caractérisées par la présence d'un domaine LytM également recrutées au site de division, ainsi AmiC est activé par NlpD. AmiC est composée d’un domaine catalytique et d’un domaine AMIN qui lie le peptidoglycane et est nécessaire et suffisant pour la localisation de la protéine au site de division. Néanmoins, le mode d’interaction du domaine AMIN avec le PG pour la localisation au site de division et le mécanisme exact d’activation de l’amidase sont encore mal compris. Nous avons établi par RMN que 13 résidus du domaine AMIN seraient importants pour l’interaction avec le PG et que la nature du celui-ci jouait aussi un rôle dans cette interaction. Parallèlement, nous avons élaboré une banque de 41 mutants du domaine AMIN pour caractériser leurs impacts sur l’interaction des protéines mutées avec le peptidoglycane et/ou leur localisation au site de division. Parmi ces protéines mutées, 27 ont été purifiées et 11 ont été testées en co-précipitation avec le peptidoglycane avec lequel elles ont toutes interagit. Des constructions permettant l’analyse de la localisation de ces protéines mutées in vivo en fusion avec la sfGFP ont aussi été réalisées. Enfin, le domaine LytM de NlpD a été cristallisé. [less ▲]

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See detailBiomasse et stocks de carbone en Afrique centrale: importance de l'allométrie des arbres
Loubota Panzou, Grâce Jopaul ULiege

Doctoral thesis (2018)

Quantifier les stocks de biomasse et de carbone dans les forêts tropicales est essentiel pour la mise en oeuvre des stratégies d’atténuation des changements climatiques, et notamment le mécanisme de ... [more ▼]

Quantifier les stocks de biomasse et de carbone dans les forêts tropicales est essentiel pour la mise en oeuvre des stratégies d’atténuation des changements climatiques, et notamment le mécanisme de réduction des émissions dues à la déforestation et la dégradation (REDD+). Les scientifiques s’accordent aujourd’hui à utiliser une équation allométrique de biomasse générale, combinée à une allométrie hauteur-diamètre ajustée sur des données locales non-destructives. Or, l’allométrie des arbres varie néanmoins, entre les espèces et stratégies fonctionnelles d’une part, entre les types de forêts et conditions du milieu d’autre part. L’objectif général de cette thèse de doctorat était d’étudier les variations de l’allométrie des arbres en vue d’améliorer les estimations de la biomasse et des stocks de carbone en Afrique centrale. Les variations de l’allométrie des arbres étaient étudiées à deux échelles : (1) entre espèces coexistentes au sein d’un type de forêt ; et (2) entre sites et types de forêts. A l’échelle des espèces, les variations des allométries hauteur-diamètre et houppier-diamètre ont été reportées entre les 45 espèces d’arbres coexistentes d’un site représentatif des forêts semi-décidues à Celtis du nord Congo. Les relations entre les traits architecturaux (hauteur totale et dimensions du houppier) dérivés à partir des allométries spécifiques aux espèces et les traits fonctionnels ont mis en évidence un continuum d’espèces entre les espèces de grande taille dominant canopée et les espèces de petite taille dominant le sous-bois. Les espèces d’arbres de grande taille étaient exigeants en lumière, dispersées par le vent, décidues avec une large contribution à la biomasse forestière, alors que les espèces d’arbres de petite taille étaient tolérantes à l’ombrage, dispersées par les animaux, sempervirentes et plus abondantes en densité de tiges. A l’échelle des sites, nous avons mis en évidence des variations de l’allométrie hauteur-diamètre des arbres entre les types de forêts, et pour la première fois en Afrique centrale, des variations de l’allométrie houppier-diamètre entre les types de forêts. Ces tendances étaient également confirmées pour les espèces communes entre les types de forêts, suggérant un contrôle environnemental sur les variations de l’allométrie des arbres. A partir des allométries spécifiques aux sites, des attributs architecturaux (hauteur totale et dimensions du houppier), en plus des attributs plus classiques de structure (surface terrière, densité de tiges…) et de composition (densité du bois) ont pu être dérivés et reliés aux variations spatiales de la biomasse et des stocks de carbone. Cette thèse de doctorat a fourni de nouvelles données nécessaires sur l’estimation de la biomasse et de stocks de carbone forestiers en Afrique centrale. Il y a également des perspectives pratiques à ce travail, notamment pour les futures cartes de biomasse dans le cadre du suivi du carbone forestier, qui pourraient s’appuyer sur des sites étudiés dans cette thèse. [less ▲]

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See detailContribution of reverse genetics in design of antiviral vaccines
Li, Lin ULiege

Doctoral thesis (2018)

Lin Li. (2018). Lin Li. (2018). Contribution of reverse genetics in design of antiviral vaccines. (PhD Dissertation in English). Gembloux, Belgique, Gembloux Agro-Bio Tech, Université de Liège. Classical ... [more ▼]

Lin Li. (2018). Lin Li. (2018). Contribution of reverse genetics in design of antiviral vaccines. (PhD Dissertation in English). Gembloux, Belgique, Gembloux Agro-Bio Tech, Université de Liège. Classical swine fever (CSF) and pseudorabies are caused by classical swine fever virus (CSFV) or pseudorabies virus (PRV), respectively. Both of them induce important economic losses in many countries, such as China and other developing countries that lack good diagnostic methods and good vaccines. Therefore, in order to wipe out these viruses and protect the animals from virus infection, it is necessary to develop better diagnostic tools and vaccines. In the first part of my thesis, we developed an indirect enzyme-linked immune-sorbent assay (iELISA) to differentiate vaccinated animals from the infected. The results showed that the sensitivity (94.6%) and specificity (97.1%) of the test is very good. The iELISA can thus be employed to diagnose CSF. In the second part of my thesis, we focused on the gE protein of PRV. Using the yeast-two hybrid system, we have isolated 8 proteins from cDNA library interacting with gE. One of these, translocator protein (TSPO) was further characterized. Interaction of gE with TSPO was supported by coimmunoprecipitation and confocal imaging analyzes. We further demonstrate that overexpression of TSPO affects cholesterol levels and suppresses virus attachment and replication. In the third part of my thesis, we studied another viral system. We wrote a review about oncogene-dependent replication of human T-cell leukemia virus (HTLV-1) in the presence of a strong immune response. In conclusion, we have made contributions to a better understanding of different viral systems and provided new tools to improve diagnostics and prevention. [less ▲]

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See detailEnergy-Based Magnetic Hysteresis Models - Theoretical Development and Finite Element Formulations
Jacques, Kevin ULiege

Doctoral thesis (2018)

This work focuses on the development of a highly accurate energy-based hysteresis model for the modeling of magnetic hysteresis phenomena. The model relies on an explicit representation of the magnetic ... [more ▼]

This work focuses on the development of a highly accurate energy-based hysteresis model for the modeling of magnetic hysteresis phenomena. The model relies on an explicit representation of the magnetic pinning effect as a dry friction-like force acting on the magnetic polarization. Unlike Preisach and Jiles-Atherton models, this model is vectorial from the beginning and derives from thermodynamic first principles. Three approaches are considered: the first one, called vector play model, relies on a simplification that allows an explicit, and thus fast, update rule, while the two others, called the variational and the differential approaches, avoid this simplification, but require a non-linear equation to be solved iteratively. The vector play model and the variational approach were already used by other researchers, whereas the differential approach introduced in this thesis, is a new, more efficient, exact implementation, which combines the efficiency of the vector play model with the accuracy of the variational approach. The three hysteresis implementations lead to the same result for purely unidirectional or rotational excitation cases, and give a rather good approximation in all situations in-between, at least in isotropic material conditions. These hysteresis modeling approaches are incorporated into a finite-element code as a local constitutive relation with memory effect. The inclusion is investigated in detail for two complementary finite-element formulations, magnetic field h or flux density b conforming, the latter requiring the inversion of the vector hysteresis model, naturally driven by h, for which the Newton-Raphson method is used. Then, at the finite-element level, once again, the Newton-Raphson technique is adopted to solve the nonlinear finite-element equations, leading to the emergence of discontinuous differential reluctivity and permeability tensors, requiring a relaxation technique in the Newton-Raphson scheme. To the best of the author’s knowledge, the inclusion of an energy-based hysteresis model has never been successfully achieved in a b-conform finite-element formulation before. [less ▲]

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See detailTowards operational use of combined Split-Band Interferometry and Multidimensional Small Baseline Subset: application to geohazard monitoring in the Kivu region
Libert, Ludivine ULiege

Doctoral thesis (2018)

The vulnerable region of Kivu is strongly affected by geohazards such as volcanism and landslides. An essential ingredient for modelling the geophysical processes from which these geohazards originate is ... [more ▼]

The vulnerable region of Kivu is strongly affected by geohazards such as volcanism and landslides. An essential ingredient for modelling the geophysical processes from which these geohazards originate is the measure of the Earth’s surface displacements. In this complex region, monitoring these ground deformations can be efficiently performed by using Synthetic Aperture Radar Interferometry (InSAR). Nevertheless, geophysical modelling requires accurate measurements of the displacements over time, which are not always manageable with conventional InSAR due to area-related limitations such as geometric distortions. Consequently, we consider advanced processing techniques such as Split-Band Interferometry (SBInSAR), which potentially allows to calculate the absolute interferometric phase, and Multidimensional Small Baseline Subset (MSBAS), which reconstructs the history of deformations along the horizontal and vertical directions. The aims of this thesis are the investigation of the SBInSAR and MSBAS techniques for improving the ground deformation measurements, the development of these techniques in order to achieve an operational tool of monitoring, and eventually to combine the information provided by both methods. Regarding the Split-Band Interferometry, we consider its theoretical applicability, determine optimum processing parameters and propose a method that corrects phase ambiguities by using SBInSAR as a complement to classical phase unwrapping, which we call SBInSAR-assisted phase unwrapping. We establish that the best criterion for the detection of spectrally stable pixels is the slope standard deviation. We also study the temporal behaviour of spectrally stable pixels and show that few of them persist over time. We analyze the behaviour of artificial reflectors with respect to SBInSAR and provide strong evidences that there exists a correlation between the signal-to-clutter ratio of a target and its detectability as a spectrally stable pixel. Regarding the Multidimensional Small Baseline Subset, we present the InSAR mass processing chain developed in collaboration with the European Center for Geodynamics and Seismicity for MSBAS preprocessing, and we propose to optimize the spatial coverage of MSBAS measurements by using interpolation or global masking. An MSBAS analysis is carried out over the city of Bukavu for the period from January 2016 to September 2017. We also study temporal decorrelation over the Virunga Volcanic Province and we model it using a decreasing exponential function. As a complement, we implement the Range Split-Spectrum technique in the CIS software for the ionospheric phase compensation in low frequency interferograms. We finally discuss the options for merging SBInSAR and MSBAS together. [less ▲]

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See detailVariabilité des concentrations cellulaires phytoplanctoniques de diméthylsulfoniopropionate (DMSP) et de diméthylsulfoxyde (DMSO) en Baie Sud de la Mer du Nord
Speeckaert, Gaëlle ULiege

Doctoral thesis (2018)

The eutrophication of the Southern Bight of the North Sea has been benefitting to the prymnesiophyte Phaeocystis globosa (P. globosa). This species is a known high dimethylsulfoniopropionate (DMSP ... [more ▼]

The eutrophication of the Southern Bight of the North Sea has been benefitting to the prymnesiophyte Phaeocystis globosa (P. globosa). This species is a known high dimethylsulfoniopropionate (DMSP) producer whose bloom accounts for 95% of spring phytoplankton biomass. An increase in DMS(P) and its oxidation product dimethylsulfoxide (DMSO) cellular contents have been frequently observed in cellular stress conditions. To test this, we have first analysed the natural distribution of DMS(P,O) cellular contents in the North Sea. Secondly, we have measured DMS(P,O) cellular contents in monospecific cultures of several key species of the North Sea and their responses to salinity variations. Our main working hypothesis is that DMSP acts as an osmoregulator and/or as an antioxidant, depending on the species. The DMS(P,O) annual cycle in the Southern Bight of the North Sea revealed a seasonality linked to the spring phytoplankton communities succession: (1) colonial diatoms (reappearing in autumn), (2) Chaetoceros spp., (3) P. globosa, (4) large-size summer diatoms (mainly Guinardia spp.), and (5) dinoflagellates. Spatial gradients of DMS(P) were related to those of phytoplankton biomass, itself related to the inputs of nutrients from the Scheldt estuary. It also discharges suspended matter in which DMSO may have been produced by anaerobic oxidation of DMS. Laboratory measurements confirmed a large variability in DMSP cellular contents between the six studied diatoms (Nitzschia closterium, Skeletonema costatum, Thalassiosira rotula, Chaetoceros socialis, Chaetoceros debilis, and Guinardia delicatula), low producers in comparison with P. globosa and even more with Heterocapsa triquetra (Dinoflagellate). In particular, communities 2 and 4 have lower DMSP cellular contents than community 1 (N. closterium, S. costatum and T. rotula). Senescence induces a decrease in DMSP/DMSO suggesting an oxidative stress caused by nutrients and/or light limitation in DMSP producers. In S. costatum, DMSP seems to play an osmoregulatory role and is oxidised into DMSO in hyposaline conditions. In P. globosa and H. triquetra, an oxidative stress appears in hypo- and hypersaline conditions diverging from their salinity optimum. [less ▲]

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See detailUse of Soil and Litter Arthropods as Biological Indicators of Soil Quality in Southern Rwanda
Nsengimana, Venuste ULiege

Doctoral thesis (2018)

Abstract - Nsengimana Venuste (2018). Use of soil and litter arthropods as biological indicators of soil quality in Southern Rwanda. University of Liège, Gembloux Agro Biotech. Pages: 121, tables: 13 ... [more ▼]

Abstract - Nsengimana Venuste (2018). Use of soil and litter arthropods as biological indicators of soil quality in Southern Rwanda. University of Liège, Gembloux Agro Biotech. Pages: 121, tables: 13, figures: 3 To assess soil quality under different land uses by the use of soil and litter arthropods as biological indicators, a research was conducted in the Arboretum of Ruhande and the Rubona agricultural research station in southern Rwanda. Soil and litter arthropods were collected by pitfall sampling technique and identified to the family level. Ants (Hymenoptera: Formicidae) were identified to species level. Soil cores were collected and analysed for soil organic carbon, total nitrogen, available phosphorus, pH, aggregate stability, cation exchange capacity, electrical conductivity, silt, and clay and sand soil textures. C:N ratios were calculated from the mass of carbon to the mass of nitrogen. Higher levels of total nitrogen, soil organic carbon, and clay and silt soil texture were found in native and exotic tree species. Higher levels of cation exchange capacity, pH, and electrical conductivity were found in native tree species and banana plantations, while higher levels of available phosphorus, aggregate stability and sand soil texture were found in coffee and banana plantations. The analysis of the abundance of collected soil and litter arthropods indicated higher abundance of the most of identified families in native and exotic tree species than in the varieties of coffee and banana plantations. Families of Scolopendridae, Trombiculidae, Eosentomidae, Formicidae and Staphylinidae showed strong correlation with soil physicochemical properties. Formicidae highly occurred in all land uses and discriminated between clay, sand, aggregate stability, pH, available phosphorus, electrical conductivity and cation exchange capacity. The ecological functions of identified families contribute to the soil quality through predation, decomposition, bioturbation and phytophagous that increase soil organic matter and facilitate water retention and soil aeration. The taxonomy of ants to species level indicated 30 species belonging to 14 genera, and four subfamilies, the Formicinae, Dorylinae, Myrmicinae and Ponerinae. These species correlated with soil properties in different ways, but their ecological functions that contribute to soil quality are not yet well documented. We recommend further studies to be replicated in other land uses and ecological zones of Rwanda, to include the impact of climate variability, altitudinal variation, functional diversity, metal and soil microbiology and the taxonomy of the entire community composition of collected soil and litter arthropods to species level in order to generalize these findings. Key words: Community composition, Doryllinae, Formicinae, Myrmicinae, Ponerinae, land use, physicochemical parameters [less ▲]

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See detailAnalyse des risques environnementaux liés aux pratiques phytosanitaires dans les écosystèmes aquatiques du bassin cotonnier (Nord Bénin)
Gouda, Abdoul-Ibrachi ULiege

Doctoral thesis (2018)

In Benin, the cotton sector occupies a preponderant place in the national economy. Its production is confronted with attacks from pests and diseases causing losses of 50 to 70%. In the absence of ... [more ▼]

In Benin, the cotton sector occupies a preponderant place in the national economy. Its production is confronted with attacks from pests and diseases causing losses of 50 to 70%. In the absence of sustainable alternatives, the use of plant protection products (PPPs) is widespread and poorly regulated. A survey of 150 cotton farmers on phytosanitary practices shows that only 19% of PPPs are registered in Benin for cotton. 75% of producers have not received any instruction and 5% have received training on treatments. As a result, 75% of operators overdose insecticides, 80% do not protect themselves and empty packaging is abandoned or sometimes used for domestic purposes. Scenarios based on the observations have made it possible to estimate that the potential exposure of producers significantly exceeds the AOEL values for all the active substances identified, sometimes by more than 50 times. Using a tracer (tartrazine), the drift generated by a backpack device and a centrifugal rod was quantified under identical weather conditions. The results show that a higher spraying height and the use of a centrifugal spray can generate significantly higher drift percentages. The quantities transferred by air to the water reservoirs are small and the droplets disperse up to a distance of 16 m regardless of the device used. Using cotton plot collectors and water retention sampling, the transfer of pesticides by runoff was quantified after several rainfall events during the 2016-2017 season. The results indicate the systematic presence of acetamiprid (mainly in the aqueous phase) and chlorpyrifos (mainly on sediments), which is explained by their solubility and adsorption to soil particles. However, the results also indicate that the quantities transferred by runoff are low and depend on rainfall, environmental characteristics (slope, soil cover and structure) and certain phytosanitary or cultural practices. At concentrations observed in the receiving environment, the ecotoxicological risk of acetamiprid would be negligible (IRE = 4) to aquatic organisms, earthworms and birds. However, chlorpyrifos concentrations in the environment could be harmful to these organisms (IRE = 272). To remedy this situation, actions to develop the surroundings of water reservoirs and to raise producers' awareness of good phytosanitary practices are necessary. [less ▲]

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See detailEvaluation de l’impact des antibiotiques et des pesticides utilisés en élevage et en agriculture sur la qualité sanitaire de la viande bovine consommée au Nord-Est du Bénin
Dognon, Sèmanou Robert ULiege

Doctoral thesis (2018)

The presence of antibiotic and pesticide residues in food can cause health problems for consumers. However, no study has quantified residues of veterinary antibiotics and pesticides in meat of cattle ... [more ▼]

The presence of antibiotic and pesticide residues in food can cause health problems for consumers. However, no study has quantified residues of veterinary antibiotics and pesticides in meat of cattle massively bred in North Benin. This is why the overall objective of this thesis is to evaluate the impact of the use of veterinary antibiotics and pesticides on the safety of cattle meat consumed in North-East of Benin. The first chapter is a compilation of three review papers that were titled, respectively: “production, importation and quality of meat consumed in Benin”; “quality of veterinary antibiotics used in West Africa and methods for detecting of their residues in foodstuffs” and “review on the modes of action, impacts and detection of pesticides used in agriculture”. In chapter 2, a survey was first conducted among 98 farmers in the communes of Banikoara, Kandi, Bembereke and Kalale located in North-East of Benin. This first study showed that the antibiotics used in cattle breeding belonged to the groups of tetracyclines, beta-lactams, sulphonamides, aminoglycosides and macrolides, which were used per 100; 88; 56; 44 and 35% of breeders, respectively, in the study area. Fifty-eight percents of these farmers bought these drugs in the illegal market, 57% of them practiced “self-medication” and 93% of them did not respect the withdrawal times for antibiotics before putting foodstuffs from treated animals on the market. These risky practices led to the contamination of cattle meat with antibiotic residues, as was shown in the second study. The kidney and muscle tissues of 50 cattle carcasses from the Parakou city, in north-east of Benin, were samples to determine antibiotic residues (tetracyclines, beta-lactams and sulfonamides), using a semi-quantitative screening method adapted from the New Two Plates Test (NTPT) of Pham Kim et al. (2011). This modified NTPT showed that 60 % of the 50 carcasses analyzed contained residues of tetracyclines, beta-lactams and sulfonamides. Positive results were confirmed by liquid chromatography - mass spectrometry (LC-MS) analyzes. The maximum levels observed for oxytetracycline, epi-oxytetracycline, tetracycline and epi-tetracycline residues in the kidney were 1380, 350, 190 and 230 μg kg-1, respectively. In one of the bovine carcasses, very high levels of sulfamethazine residues were found: 3900 μg kg-1 in the kidney and 2220 μg kg-1 in the muscle. Overall, 38 % of the carcasses submitted to confirmation analyzes by LC-MS showed antibiotic residue levels that exceeded the maximum residue limits (MRLs) applied in the European legislation. The modified NTPT method was then used to evaluate the quality of veterinary antibiotic drugs used in cattle breeding in the study area. The results of this third study showed that the 28 products tested contained the active ingredient as indicated on the drug labels. However, quantitatively, only 61 % of these drugs contained active substance at levels ranging from 90 to 120 %, 90-115 % and ≥ 90 % of the concentrations mentioned on the labels (for oxytetracycline, penicillin G and tylosin drugs, respectively), and could therefore be declared compliant with the requirements of USP (United States Pharmacopeia). The results of the studies reported in this chapter 2 have shown that veterinary practices, resulting in the presence of residues in the meat, and the poor quality of veterinary antibiotics could promote the development of bacterial resistance to antibiotics in the study area. Chapter 3 presents the results of studies 4 and 5. The inventory realized in study 4 showed that 56 commercial pesticides (including 21 herbicides and 35 insecticides) were used in agriculture in the study area. As regards the active ingredients contained in these products, 13 were herbicides and 14 were insecticides. Seventy-eight percents of farmers bought these pesticides both in the illegal circuit and in the official agricultural inputs selling structures. Only 53 % of these farmers knew the instructions for use of these dangerous products. These practices have led to the contamination of natural ecosystems and the food chain with pesticide residues. Indeed, study 5 revealed traces of glyphosate residues in pasture waters. In addition, three of 25 cattle carcasses that samples were subjected to the analyzes by gas chromatography - mass spectrometry, were contaminated with insecticide residues such as beta-endosulfan (98.6-139.5 μg kg-1) and dichlorodiphenyldichloroethylene (DDE) (4.6 μg kg-1). Overall, only beta-endosulfan found in two carcasses showed concentrations above the MRL established by European Regulation (EC) 396/2005. Finally, chapter 4 presents a general discussion of the results obtained in the five studies. As a general conclusion and recommendation, it can be said that all the veterinary and agricultural practices as described in studies 1 and 4 clearly impact the safety of cattle meat consumed in North-East of Benin, and the results of these studies are benchmarks for future monitoring of the food chain in Benin. [less ▲]

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See detailAnticancer Effects of Soybean Bioactive Components and Anti-inflammatory Activities of the Soybean Peptide Lunasin
Zhu, Yingying ULiege

Doctoral thesis (2018)

Soybean products have been demonstrated to have health-promoting benefits. In this study, we investigated the anticancer effect of 12 bioactive components from soybean on human breast cancer cells in ... [more ▼]

Soybean products have been demonstrated to have health-promoting benefits. In this study, we investigated the anticancer effect of 12 bioactive components from soybean on human breast cancer cells in vitro. Results showed that genistein, daidzein, glycitein, genistin and dainzin showed stronger anti-proliferative activity against MCF-7 cells with median effective concentration (EC50) values of 66.98±4.87 μM, 130.14±2.10 μM, 190.67±5.65 μM, 72.82±2.66 μM and 179.21±6.37 μM, respectively. There was a synergistic effect of combination treatment of genistin plus daidzin in MCF-7 cells with combination index at inhibition of 50% (CI50) of 0.89±0.12. Genistein, glycitein, genistin and β-sitosterol were demonstrated to have a stronger anti-proliferative activity against MDA-MB-231 cells with EC50 values of 93.75±5.15 μM, 142.67±5.88 μM, 127.82±4.70 μM and 196.28±4.45 μM. The synergistic effect was observed in the mixture of genistein plus genistin, genistein plus β-sitosterol or β-sitosterol plus genistin with CI50 values of 0.56±0.13, 0.54±0.20 and 0.45±0.12, respectively. These bioactive components were able to inhibit invasion and migration in breast cancer cells and the combination treatments enhanced the inhibitory effect. Regulation of PI3K/Akt/mTOR pathway seems to be the main mechanism involved in the anticancer activity. Among all the tested components from soybean, lunasin attracted our interests because that it is a novel peptide and many problems about lunasin remained to be studied. About lunasin, we were concerned about its anti-inflammatory activity and involved signalling pathways, as well as its production using genetic engineering method. In this study, we isolated natural lunasin (N-lunasin) from soybean and expressed recombinant lunasin (R-lunasin) from Pichia (P.) pastoris. The expression level of R-lunasin reached 240 mg/L cell-free broth at the optimum condition (initial pH 7.0, 1.0% final methanol concentration and induction for 72 h at 26 °C). The anti-inflammatory activity of N-lunasin and R-lunasin was accessed and compared. Results showed that there was a comparable effect of N-lunsin and R-lunasin on inhibition of release of nitric oxide (NO), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in a dose-dependent manner. In addition, intracellular signalling array analysis demonstrated down-regulated levels of phosphorylated Akt, mechanistic target of rapamycin (mTOR) and p70 s6 kinase (p70s6k) and an up-regulated level of glycogen synthase kinase-3β (GSK-3β) after R-lunasin treatment. These results suggest that lunasin exerted anti-inflammatory activity in LPS-stimulated RAW264.7 cells partly via inhibiting the activation of Akt/mTOR/p70s6k signalling pathway. Soybean is widely cultivated from north China to south China. We were also interested in the variation in lunasin content in soybean seeds. In this study, we determined the lunasin content in a total of 413 soybean samples that were collected from four major regions in China and harvested in 2014 and 2015 to reveal the regional distribution of soybean lunasin content in China and the effects of climate factors. The results showed that the cultivar Changmidou 30 collected from Jilin province and harvested in 2015 had the highest lunasin content (3.25 mg/g dry seeds). The data from both 2014 and 2015 showed that the lunasin content in soybean collected from north China was significantly higher (p<0.05) than that from south China. There was a positive correlation (p<0.01) between lunasin content and hours of sunshine (HS) as well as diurnal temperature range (DTR); however, there was a negative correlation (p<0.01) between the lunasin content and rainfall (RF). In addition, the combined analysis of data from 2014 and 2015 demonstrated that DTR was the dominant factor that affects the lunasin content with a direct path-coefficient of 0.301. These results generated from our study are anticipated to improve our knowledge of bioactive components in soybean as well as their bioactivities. [less ▲]

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See detailStudy of the birth, the growth and the life of a dynamical cluster under microgravity conditions
Noirhomme, Martial ULiege

Doctoral thesis (2018)

Granular materials can produce spectacular phenomena due to the dissipation that occurs when the grains collide. In microgravity environments, a granular material can adopt different behaviors, mainly ... [more ▼]

Granular materials can produce spectacular phenomena due to the dissipation that occurs when the grains collide. In microgravity environments, a granular material can adopt different behaviors, mainly depending on the packing fraction of the system and the intensity of the energy that is injected into the system. By regulating the packing fraction, a granular gas or a dense and slow aggregate can be observed. These aggregates are called "clusters" and their emergence has been studied both theoretically and numerically in the last decades. In addition, the parameters triggering the gas-cluster transition were highlighted during these studies. Nevertheless, these theoretical and numerical considerations have never been verified experimentally and the cluster, which always coexist with granular gases in the case of excited systems, requires still a lot of attention. That's why the SpaceGrains project has been launched by the European Space Agency (ESA). This project contributes to the study of granular phenomena in microgravity thanks to the development of the VIP-Gran-PF instrument, containing of a cell in which bronze beads can be excited by two oscillating pistons. The cell can be quasi-two or three dimensional. The instrument was developed for parabolic flights and the first part of this work has consisted in verifying experimentally the gas-cluster transition and to observe some dynamics which have been predicted by numerical simulations. These simulations constitute the second part of our work. Perfect knowledge of the capabilities and performance of the VIP-Gran-PF instrument as well as advanced training were required before starting to use it in parabolic flights. Our experimental work began with the study of the instrument itself. Once the handling of the VIP-Gran-PF device acquired, we focused on several topics. The first concerned the experimental verification of the gas-cluster transition. This study required a large number of parabolic flight campaigns (5 to be exact) since it was necessary to explore an entire phase diagram, that was derived from numerical simulations. Granular gases and clusters, as well as an unexpected "bouncing aggregate" regime, have been observed during these campaigns. By developing an original image processing, we have been able to reconstruct the distributions of the three dimensional positions of the particles in the VIP-Gran cell on the basis of two dimensional pictures. Adapting an existing model, we also predicted the possibility of emergence of the "bouncing aggregate" regime. In parallel with this study, we performed numerical simulations in order to determine the mechanism of birth and growth of clusters within the instrument. By sorting the grains as gaseous or clustered with a local criterion, we have discovered that the cluster was born in the corners near the lateral walls of the cell, as far as possible from the oscillating pistons. We also show that the cluster grows because the gas has to keep a critical packing fraction. Other numerical simulations allowed us to identify a specific dynamic of the cluster. By asymmetrically exciting the particles, it is possible to displace the position of the center of mass of the system. Moreover, a natural oscillation of the cluster, linked to its size, the asymmetry and the driving frequency, has been highlighted. Finally, we were interested in the structure of clusters in the case of a mixture of two different types of particles. As a function of their difference in mass and/or in volume, we showed that different structures are observed and that a phase segregation could take place in the system. Finally, we realized experiments in order to validate all of our numerical simulations, except for the growth of the clusters, which is impossible to observe in the current configuration of the VIP-Gran-PF instrument. We also investigated the clustering of elongated particles, the behavior of intruders in a granular gas, such granular osmosis by using a semi permeable wall and the behavior of a mobile wall placed in between both pistons. At this point, the data of these studies still has to be analyzed. [less ▲]

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See detailOn the Fluid Mechanics of Self-Aeration in Open Channel Flows
Valero Huerta, Daniel ULiege

Doctoral thesis (2018)

This dissertation is organized in five parts. Part I is made of four chapters which aim to introduce this dissertation and put it in the context of past developments. In Chapter 1, a historic analysis of ... [more ▼]

This dissertation is organized in five parts. Part I is made of four chapters which aim to introduce this dissertation and put it in the context of past developments. In Chapter 1, a historic analysis of air-water flows research in open channel flows is presented, jointly with a detailed discussion on research trends. Besides, aims and scope of this dissertation are clearly defined. Chapter 2 focuses on fundamental studies directly dealing with self-aeration, Chapter 3 deals with experimental studies on the self-aeration onset determination and Chapter 4 examines past attempts on numerical modelling of air-water flows. Part II describes the non-aerated region, which is of interest for the subsequent chapters. This part is intentionally divided into two chapters as to highlight the relevance of a commonly forgotten aspect: the free surface. Thereby, Chapter 5 deals with the water and air phases in the non-aerated flow region of spillways, whereas Chapter 6 is entirely dedicated to conceptualize the free surface. Main hypotheses related to the upcoming analytical derivations are also examined in Chapter 6. Part III is the kernel of this dissertation and is divided into two chapters. The first one, Chapter 7, is dedicated to the mathematical derivations related to the equations governing the turbulent motion of a free surface. The main result of Chapter 7 is a kinematic and a dynamic equation that, together, yield a non-linear second-order differential equation describing the growth of the free surface perturbations. 8 aims to approximate, as accurately as possible, the forces acting over a free surface perturbation. The equations obtained in Chapters 7 and 8 allow computation of the growth rates for each wavelength, the free surface fluctuations spectra and the perturbations steepness. Part IV is composed of two chapters. Chapter 9 presents an application where capabilities of the derived equations are brought to light by means of a prototype scale application. Chapter 10 focuses on some empirical evidences obtained at a large-scale stepped spillway model. Perturbations growth is predicted by the developed theoretical model. Furthermore, it is shown that the free surface turbulent structure agrees, for the biggest wavelengths (gravitational dominated wavelengths), with that predicted by the mathematical analysis up to around 30 % of the non-aerated region length. Downstream, the energy distribution of these wavelengths starts changing. Notwithstanding that, the free surface structure at smaller wavelengths (surface tension dominated wavelengths) holds valid up to the inception point location. Further evidences also point in the direction of a breaking steepness as an appropriate parameter for self-aeration characterization. Part V contains a single chapter. This last chapter brings closure to this thesis and offers a discussion on the most relevant achievements and limitations of this doctoral work, together with an outlook into the future research challenges to be addressed. In summation, this investigation has provided with a fluid mechanics description of the self-aeration onset while demonstrating that it is the result of a new type of two-phase flow instability. [less ▲]

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