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See detailUnderstanding Random Forests: From Theory to Practice
Louppe, Gilles ULg

Doctoral thesis (2014)

Data analysis and machine learning have become an integrative part of the modern scientific methodology, offering automated procedures for the prediction of a phenomenon based on past observations ... [more ▼]

Data analysis and machine learning have become an integrative part of the modern scientific methodology, offering automated procedures for the prediction of a phenomenon based on past observations, unraveling underlying patterns in data and providing insights about the problem. Yet, caution should avoid using machine learning as a black-box tool, but rather consider it as a methodology, with a rational thought process that is entirely dependent on the problem under study. In particular, the use of algorithms should ideally require a reasonable understanding of their mechanisms, properties and limitations, in order to better apprehend and interpret their results. Accordingly, the goal of this thesis is to provide an in-depth analysis of random forests, consistently calling into question each and every part of the algorithm, in order to shed new light on its learning capabilities, inner workings and interpretability. The first part of this work studies the induction of decision trees and the construction of ensembles of randomized trees, motivating their design and purpose whenever possible. Our contributions follow with an original complexity analysis of random forests, showing their good computational performance and scalability, along with an in-depth discussion of their implementation details, as contributed within Scikit-Learn. In the second part of this work, we analyze and discuss the interpretability of random forests in the eyes of variable importance measures. The core of our contributions rests in the theoretical characterization of the Mean Decrease of Impurity variable importance measure, from which we prove and derive some of its properties in the case of multiway totally randomized trees and in asymptotic conditions. In consequence of this work, our analysis demonstrates that variable importances as computed from non-totally randomized trees (e.g., standard Random Forest) suffer from a combination of defects, due to masking effects, misestimations of node impurity or due to the binary structure of decision trees. Finally, the last part of this dissertation addresses limitations of random forests in the context of large datasets. Through extensive experiments, we show that subsampling both samples and features simultaneously provides on par performance while lowering at the same time the memory requirements. Overall this paradigm highlights an intriguing practical fact: there is often no need to build single models over immensely large datasets. Good performance can often be achieved by building models on (very) small random parts of the data and then combining them all in an ensemble, thereby avoiding all practical burdens of making large data fit into memory. [less ▲]

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See detailInteractions in massive binaries: spectral modelling – CoMBiSpeC – and observational analyses
Palate, Matthieu ULg

Doctoral thesis (2014)

Massive stars are very important to the life of the galaxiesbut they are rare and many open questions on their formation, evolution and characteristics remain. One of the best ways to improve our ... [more ▼]

Massive stars are very important to the life of the galaxiesbut they are rare and many open questions on their formation, evolution and characteristics remain. One of the best ways to improve our knowledge on massive stars is to study massive binaries (that represent at least 50% of massive stars see Mahy et al. 2009, and Sana & Evans 2011) and their spectra. Spectral and atmosphere modelling of stars are very interesting tools that are now often used in spectral analyses. However, these models are designed for single spherical stars. In this context, we have developed a numerical code of spectral modelling of massive binary systems: CoMBiSpeC (code of massive binary spectral computation) that computes the spectra of massive binary systems and accounts for various effects that affect these systems. Our models, and the observational analyses of the four binary systems presented in the second part of this work, have allowed to explain several effects linked to binarity: luminosity class discrepancy, temperature distribution, Struve-Sahade effect, and some kind of line profile variations. In summary, CoMBiSpeC is a first step in the spectral modelling of massive binary systems and several improvements are still needed to be able to study all massive binaries. Nevertheless, this model can explain and reproduce various observed phenomena which was the main goal of this thesis. [less ▲]

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See detailContribution à l'exploration de la structure des sols par microtomographie aux rayons X : vers une amélioration de la modélisation hydropédologique
Beckers, Eléonore ULg

Doctoral thesis (2014)

The aim of this thesis is to tend towards a better representation of soil water horizontal fluxes in hydropedological modelling. Tillage practices result in soil structural modifications which impact soil ... [more ▼]

The aim of this thesis is to tend towards a better representation of soil water horizontal fluxes in hydropedological modelling. Tillage practices result in soil structural modifications which impact soil hydrodynamic behaviour. This study takes place in this context, aiming to understand these modifications using X-ray microtomography (µCT), which allows a more fundamental analysis of soil. Indeed, this tool becomes a key in the field of soil science, giving a direct insight of the internal structure of soil. Besides, anisotropy studies are still rare as tiresome, and this work shows that the current hydrological models are anyway unable to represent it correctly: when it is taken into account, it rests on the hypothesis of a simple ratio between vertical and horizontal conductivity functions. First, microtomography is used supplementary to usual methods for the establishment of hydrodynamic functions near saturation. We showed that the retention curve designed with µCT information is more realistic since it leads to a better estimation of unsaturated hydraulic conductivity. However, these results could be doubtful depending on the different µCT acquisition or processing choices and hypothesis. Particularly, the thresholding step is crucial. Consequently, we propose a new global thresholding method based on the visible part of soil sample porosity. This method has been tested and validated in the context of the present study. This step allows us to use microtomography results to increase our knowledge of soil structure. A principal component analysis on soil pores structural parameters confirms that connectivity, specific surface, volume and radius are key factors for the differentiation of soil horizons texturally similar but structurally different. Our results show that structural parameters have to be taken into account to improve hydropedological modelling, especially if pores orientation is considered. We described thus the relevant parameters that can be obtained with µCT and which could help to better model water fluxes in soil while discussing the remaining limits and uncertainties, about upscaling issues notably. [less ▲]

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See detailExactitude du positionnement numérique des axes de ruissellement dans les bassins versants agricoles
Ouedraogo, Mohamar ULg

Doctoral thesis (2014)

Des études récentes menées en Belgique estiment les dommages causés par les inondations et les coulées boueuses entre 12,5 et 122 millions d’euros par an pour les infrastructures publiques, et entre 1,6 ... [more ▼]

Des études récentes menées en Belgique estiment les dommages causés par les inondations et les coulées boueuses entre 12,5 et 122 millions d’euros par an pour les infrastructures publiques, et entre 1,6 et 16,5 millions d’euros par an pour les habitations. La carte des zones à risque potentiel de ruissellement concentré est l’un des outils mis en place par la Wallonie pour lutter contre ces phénomènes de plus en plus fréquents. Cependant, la résolution (10 × 10 m) du MNT utilisé pour extraire les axes de ruissellement est trop faible pour prendre en compte les détails de la microtopographie (travail du sol, résidus de cultures, cultures…) des parcelles agricoles. De plus, elle ne tient pas compte des incertitudes inévitables, présentes dans les données altimétriques utilisées. L’objectif de cette thèse est d’envisager l’utilisation des nouvelles technologies d’acquisition des données altimétriques de haute densité (plusieurs points/m²), i.e., le scanner laser terrestre (TLS) et la photogrammétrie à partir d’un véhicule non piloté (VNP) pour créer un modèle numérique de terrain (MNT) de meilleure exactitude et de haute résolution spatiale (maille de dimensions ± 1 x 1 m). Cela permet de tenir compte de la variabilité altimétrique des parcelles agricoles, et d’analyser son impact sur le positionnement numérique des axes de ruissellement. Dans un premier temps, un TLS et un VNP à voilure fixe ont été utilisés pour acquérir des données altimétriques sur un bassin versant agricole de 12 ha. Deux logiciels photogrammétriques ont permis de générer le MNTPSC (Agisoft PhotoScan) et le MNTMCM (MicMac) ; tandis que des traitements statistiques ont été nécessaires pour supprimer les erreurs systématiques présentes dans les nuages de points obtenus au TLS avant de les fusionner pour générer le MNTTLS. La comparaison des MNT avec des points de contrôle (GCP) positionnés au récepteur GNSS (Global Navigation Satellite System) en mode RTK (Real Time Kinematic) a montré que le MNTTLS est le plus exact avec un RMSE (Root Mean Square Error) de 4,5 cm, suivi par le MNTMCM et le MNTPSC avec des RMSE valant respectivement 9,0 et 13,9 cm. Dans un second temps, la méthode de Monte Carlo a été utilisée pour générer à partir du MNTTLS, des MNT équiprobables. L’extraction des axes de ruissellement à partir des MNT équiprobables a permis de définir pour chaque maille du MNT, la probabilité d’appartenir à l’axe de ruissellement, et de définir une zone contenant l’axe de ruissellement extrait du MNTTLS avec une probabilité définie. Une telle zone peut être utilisée pour la mise en place de solutions telles que les bandes et les chenaux enherbés. La comparaison des algorithmes de suppressions des dépressions fermées d’une part, et des algorithmes d’extraction de la direction de l’eau d’autre part, a montré peu de différence au niveau de la probabilité d’appartenance des mailles à l’axe de ruissellement lorsque le MNT est de haute résolution spatiale (± 1 m). Enfin, les analyses statistiques ont montré que les altitudes des GCP utilisés dans la méthode de Monte Carlo sont influencées par l’état d’ameublissement et par la rugosité des sols des parcelles agricoles. Les études futures, e.g., à l’échelle de la Wallonie, devront prendre en compte l’impact de ces erreurs. [less ▲]

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See detailTowards a better understanding of time-lapse electrical resistivity properties associated to organic contaminants and bioremediation processes in the subsurface
Caterina, David ULg

Doctoral thesis (2014)

Management of contaminated sites represents a major problem for our society. Geophysical methods arise progressively as non-conventional techniques that should allow decreasing the uncertainty linked to ... [more ▼]

Management of contaminated sites represents a major problem for our society. Geophysical methods arise progressively as non-conventional techniques that should allow decreasing the uncertainty linked to the local nature of punctual drilling/sampling measurements classically used to identify, characterize and monitor such sites. However, the use of geophysics for this purpose is relatively recent and still requires an improvement of geophysical imaging and a better understanding of the impact of contaminants and remediation processes on measured properties to be fully effective. The main objective of this thesis was thus to improve our knowledge on these two aspects. In order to assess the reliability of geophysical imaging, and electrical resistivity tomography (ERT) in particular, we first compare quantitatively different image appraisal indicators. The latter are developed to detect artefacts, estimate depth of investigation, address parameters resolution and appraise ERT-derived geometry. Numerical benchmarks are created representing different geological situations in terms of heterogeneity and scale. On the basis of this comparison, we propose a methodology and guidelines to appraise both qualitatively and quantitatively field ERT images. We show the successful applications on real data coming from the contaminated sites we investigated. It notably allows us to exclude from our interpretation zones of the electrical images that are not considered as sufficiently reliable. To enhance electrical imaging, we investigate three different approaches to incorporate prior information into the ERT inverse problem, namely reference model, structural constraint and regularized geostatistical inversion that we notably apply on real data coming from two contaminated sites. The results are benchmarked against the standard smoothness constraint inversion. Results with real data show that adding prior information in the inversion process always lead to a modification of the solution at least in zones of low sensitivity (allowing notably to better image contaminant plumes at depth). However, the choice of the constraint to apply is highly dependent on the type and amount of information available. Therefore, we provide guidelines that should help the practitioner to include their prior information directly into the inversion process through an appropriate way. To understand the temporal geoelectrical signature of organic contaminants and bioremediation processes, we monitor a site contaminated with hydrocarbons and subjected to stimulated bioremediation. We first show that the most contaminated areas above the groundwater table level are associated to very low resistivities. We then show that during biostimulation (promoting aerobic degradation) and natural attenuation, observed resistivity variations (up to 140%) are mostly located in the saturated zone of the contaminated area. They follow a seasonal trend suggesting a temperature dependence not observed in an uncontaminated zone of the site. However, in the contaminated area, changes largely exceed the expected variations due only to the temperature. We therefore investigate systematically different hypotheses that may explain such changes. Among those hypotheses, we show that microbial activity is a factor that may potentially influence the electrical signature of a contaminated soil and may contribute to the observed resistivity changes. In order to further study the electrical response associated to bacterial activity during bioremediation processes, we monitor a tank experiment that contains soils contaminated with hydrocarbons subjected first to biostimulation and then to bioaugmentation (with an inoculum of Rhodococcus erythropolis T902.1). Whereas no particular electrical signature is observed during the biostimulation phase, we observe a correlation between the evolution of bulk resistivity changes and the specific oil-degrading flora after bioaugmentation that cannot be attributed to fluid resistivity changes. This suggests a direct impact of microbial growth/activity on electrical properties through the modification of surface and/or local electrolytic conduction mechanisms. These latter results open up new perspectives for future experiments that should involve spectral induced polarization measurements allowing a better discrimination between the two conduction mechanisms. [less ▲]

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See detailModélisation numérique de la localisation des déformations dans le béton avec un modèle de second gradient
Jouan, Gwendal ULg

Doctoral thesis (2014)

Cette thèse porte sur l’utilisation d’un modèle de second gradient pour les problèmes de localisation dans le béton. La localisation des déformations est un phénomène courant dans les solides qui ont subi ... [more ▼]

Cette thèse porte sur l’utilisation d’un modèle de second gradient pour les problèmes de localisation dans le béton. La localisation des déformations est un phénomène courant dans les solides qui ont subi des chargements importants et qui mène progressivement à la fissuration du milieu. D’un point de vue pratique, il importe de prévoir la possible occurrence de tels phénomènes et de simuler le comportement de la structure après son apparition (on parlera alors de comportement post-localisation). Pour modéliser de façon objective ce phénomène, le modèle dit de second gradient «local», cas particulier des milieux à microstructure, est ici appliqué à des structures en béton. Le comportement du modèle est étudié pour des essais représentatifs de telles structures (poutre en flexion, propagation de fissures en mode I). Certaines limitations du modèle dans le cas de localisations importantes des déformations sont mises en évidence et on propose la transition vers un modèle cohésif afin de décrire l’ensemble du processus de fissuration. Ce modèle cohésif et la transition depuis la description continue sont formulés et implémentés dans un code de calcul éléments finis. [less ▲]

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See detailContribution à l'étude épidémiologique d'Anaplasma phagocytophilum chez des cervidés et suidés sauvages en Région wallonne.
Nahayo, Adrien ULg

Doctoral thesis (2014)

Au cours des vingt dernières années, de nombreuses études ont souligné l’importance croissante des maladies vectorielles. Au sein des arthropodes, les tiques occupent la deuxième place, après les ... [more ▼]

Au cours des vingt dernières années, de nombreuses études ont souligné l’importance croissante des maladies vectorielles. Au sein des arthropodes, les tiques occupent la deuxième place, après les moustiques, en tant que vecteurs d’agents pathogènes. L’anaplasmose granulocytaire humaine est une zoonose transmise par des tiques et dont l’agent responsable est Anaplasma phagocytophilum, une bactérie intracellulaire obligée qui infecte essentiellement les granulocytes neutrophiles. L’anaplasmose granulocytaire est considérée comme une maladie émergente qui suscite l’intérêt du monde scientifique. Jusqu’à présent, de nombreuses études ont été réalisées aussi bien sur les tiques vectrices d’A. phagocytophilum que sur les différentes espèces animales considérées comme réservoirs. Mais il reste actuellement beaucoup d’inconnues quant aux multiples mammifères sauvages qui hébergent cette bactérie et qui pourraient être considérés comme réservoirs potentiels. Dans ce contexte, les objectifs généraux de cette thèse étaient de déterminer si A. phagocytophilum circule au sein des populations de cervidés sauvages (cerfs et chevreuils) présents dans la zone d’étude (Région wallonne), si ces espèces sont des réservoirs compétents pour A. phagocytophilum et enfin si ces espèces peuvent être utilisées comme sentinelles sanitaires pour la surveillance spécifique de l’anaplasmose granulocytaire humaine. En outre, vu les populations importantes de suidés sur l’ensemble de la région, l’espèce sanglier a été la troisième espèce cible incluse dans l’étude. Pour remplir ces objectifs, des prélèvements ciblés (sang et rate) ont été réalisés sur les espèces cibles dans le cadre du programme de surveillance active mis en œuvre par le réseau de surveillance décrit dans la première étude. En 2006 puis 2011 et 2012, 854 cervidés et 513 sangliers ont été prélevés au sein des 33 unités géographiques couvrant la zone d’étude. Les échantillons ont été identifiés en fonction de l’espèce, de l’âge, du sexe de l’animal ainsi que de la date et du lieu de prélèvement. Un test d’immunofluorescence indirecte a été réalisé sur sérum pour détecter les anticorps anti A. phagocytophilum et une PCR 16S (qui permet d’amplifier un fragment du gène qui code pour le RNA ribosomal 16S) a été mise en œuvre sur les échantillons spléniques. Une partie des amplicons obtenus a été séquencée. Les enquêtes menées en cervidés ont montré que la séroprévalence apparente globale, en 2006 et 2012, était respectivement de 95% et 88% pour l’espèce chevreuil et de 37% et 32% pour l’espèce cerf. Les résultats PCR ont révélé que 94% des cerfs (79 sur 84) et 81% de chevreuils (245 sur 300) étaient infectés par A. phagocytophilum et que les résultats positifs étaient uniformément répartis sur l’ensemble de la zone d’étude. Par contre, le taux d’infection des sangliers était très faible puisque moins de 1 % des rates étaient PCR positives. En conclusion, nous avons montré pour la première fois en Belgique qu’A. phagocytophilum circulait de manière endémique au sein des populations de cervidés sauvages vivant en Région wallonne. Deux enquêtes sérologiques ont fourni les premiers indices de présence de cette bactérie chez des cerfs et chevreuils. Les analyses PCR ont ensuite révélé que ces deux espèces étaient fortement infectées par A. phagocytophilum par opposition aux sangliers qui présentaient des taux d’infection très faibles. Sur l’ensemble des résultats PCR positifs, les 25 amplicons séquencés étaient identiques quelle que soit l’origine de l’espèce (cerf, chevreuil ou sanglier) et ils présentaient 100% de similitude avec 2 souches d’origine humaine et plusieurs souches d’origine animale. Des études supplémentaires, qui ciblent les gènes ankA et groESL, sont nécessaires pour déterminer si les variants d’A. phagocytophilum qui circulent en faune sauvage sont pathogènes pour l’homme. Le cas échéant, chevreuil et sanglier devraient être considérés comme espèces sentinelles sanitaires pour la surveillance spécifique de l’anaplasmose granulocytaire humaine. [less ▲]

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See detailPopulations of aphid natural enemies in agroecosystems, with special emphasis on the Multicoloured Asian Ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae)
Vandereycken, Axel ULg

Doctoral thesis (2014)

The international trade of goods and food can lead to the introduction of alien species in the importing countries. Even if in the most cases there is no negative impact induced by alien species, in some ... [more ▼]

The international trade of goods and food can lead to the introduction of alien species in the importing countries. Even if in the most cases there is no negative impact induced by alien species, in some cases the new imported species can spread out of control. These species can cause economical and ecological damages. The Multicoloured Asian ladybird Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is one of these species which was intentionally introduced for biological control and has spread from its native range in Central and Eastern Asia to large parts of North and South America, Europe and Africa. The decline of native species is linked to the spread and the aggressive behaviour of H. axyridis. The objective of this thesis is the evaluation of aphid's predator population densities and predator diversities, with a special focus on H. axyridis in agroecosystems in Wallonia, in the South of Belgium. First, field crops preferences of H. axyridis were determined. Later aphid's predator population changes during time were evaluated. Finally H. axyridis population changes between two crop farming were evaluated. Our main findings were as follows. Results, based on insects collected since 2001, highlighted that the first collected H. axyridis was in 2002 and the population of H. axyridis is increasing until 2008. In the same time population of Adalia bipunctata, Propylea quatuordecimpunctata and Psyllobora vigintiduopunctata, three native species, are decreasing. Samplings in agroecosystems highlighted that aphid's predator community is composed of few dominant species: three coccinellids Coccinella septempunctata, P. quatuordecimpunctata and H. axyridis, one syrphid Episyrphus balteatus and one chrysopid Chrysoperla carnea. We have shown that H. axyridis do not invade all Wallonia crops at the same rate because corn and broad bean are more invaded that wheat and potato at both larval and adult stages. Moreover in corn, H. axyridis populations has strongly increased from 2009 to 2011. Finally, organic farming do not enhance abundance of H. axyridis but lead to increase the total abundance of aphid natural enemies. [less ▲]

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See detailQuels agritourismes pour les campagnes périurbaines ? Les cas de la Wallonie et du Grand-Duché de Luxembourg
Dubois, Charline ULg

Doctoral thesis (2014)

To cope with the economic uncertainties of the changes, transformations, and transitions affecting current European and world agriculture, many farmers are rethinking the purposes of their business and ... [more ▼]

To cope with the economic uncertainties of the changes, transformations, and transitions affecting current European and world agriculture, many farmers are rethinking the purposes of their business and are looking to diversify their activities. Taking advantage of certain assets related to their operation and of opportunities for tourism development in the region (such as availability of buildings, subsidies related to ecology and environment images), some of them have chosen agritourism, a tourist activity proposed by the farmer on his/her farm. The literature includes many studies on this topic, but there is no consensus on terminology, definitions, and concepts: they vary from one author to another and evolve over time. Having distinguished different agritourist typologies in which accommodation is a basic element, we have personally chosen to study agritourism defined as "all tourist and leisure activities and services present in a working farm". Wallonia and the Grand Duchy of Luxembourg, our geographical research areas, are neighbouring entities, with similar agriculture, and their tourist markets offer some similarities. Included in rural tourism, agritourism is nevertheless marginal compared to the overall tourist product offered. Some successes might suggest that agritourism could be the panacea against the crisis in agriculture. But is this always the case? Agritourism should be defined, localized, and differentiated. Working on these two periurban entities of Western Europe which are not yet discussed in the literature, we wanted to understand and to identify agritourist dynamics. We wanted to understand the geographic relationship between agritourism, periurban countryside, local resources, and agricultural and tourist specializations. We wanted to understand the logic of the emergence of tourism on a farm and the links between tourist and agricultural functions in a specific spatial context. Finally, we wanted to understand the integration of the motivations of different types of tourists and their reasons for visiting particular regional and local contexts. To do this, we analyse both the location and the agritourist geographical position in relation to the different markets. To meet the objectives, we conducted a comparative heuristic analysis of agritourism in both territories. We interviewed key organisational representatives (31 persons), we made field observations, documents comparisons... We conducted interviews with various Walloon and Luxembourg farmers (34 life histories) affording different agritourist practices that we synthesized by circumstantial geographical sketches. We conducted surveys with potential tourists (1148surveys) in seven Walloon and Luxembourg tourist spots. These steps and the statistical and cartographic processing based on the results allowed us to build a heuristic geographical model of the Walloon and Luxembourg agritourism. The experiences of farmers interviewed allowed us to understand the position of the agritourist system in its spatial context. Each of them develops opportunities and experience threats (economic, social, from heritage) in connection with the launch of the project, a true survival kit in some cases. It appears that agritourism is not always a panacea for farmers. On the farm, the tourist function comes after the agricultural one and is based on the latter, but the agricultural function also benefits from the tourist function because both activities are related. The emergence of tourism is an autonomous decision of the farmers who can be influenced by other actors, including authorities, but also by other factors such as the existence of a local demand or the regional real estate pressure. There is no particular profile of tourists visiting agritourism, but some features, including those of family, are more favourable to the experience of this type of tourism. Definitions and representations as well as the reasons and expectations differ depending on the characteristics of the interviewed tourists: urban or rural origin, level of experience. Three agritourist profiles were also highlighted: those seeking accommodation in a rural environment, those who think about accommodation linked to gastronomy, those who prefer accommodation that would be a comfortable basis from which to tour in a tourist area. The comparison between the experiences of farmers and the expectations of tourists shows that there is a risk of developing different organizational temporalities in the farm "open" to tourists as well as of favouring unbalanced images of agritourism, which could lead to a vision and a promotion of agriculture which does not correspond to its regional reality. By combining the different results and by linking the typology of the Walloon and Luxembourg agritourist products, the types of rural areas and the geographical components, it appears that agritourism should not only be analysed according to the environmental dimensions, but that the analysis must also take into account other factors such as accessibility, local communities, hospitality, rural development policies, the real estate market, the agricultural orientation of farm operations, as well as the degree of complementarity with tourist spots. We have demonstrated that agritourism, combining agriculture with tourism, is not developing, either everywhere, or in the same manner, and differs between different types of periurban countryside, depending on local resources. Moreover, agritourism is not always a solution for all countrysides, nor always a path for each farmer, nor always a perfect tourist destination for all tourists. However, even if strict regionalization of agritourism does not seem possible when we consider all the factors involved in the different regions, trends may emerge depending on agritourist types. There is thus a link between agritourism type and countryside type, which the heuristic model we propose should allow to improve in order to increase the convergence between the expectations of the different stakeholders. [less ▲]

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See detailL'univers romanesque d'Hubert Juin : L'aventure d'une écriture
Kangomba, Lulamba ULg

Doctoral thesis (2014)

The work has as main purpose to study the work of romance Hubert Juin trying to illuminate the paradoxes it contains: regionalist themes whose treatment goes beyond codes of regionalism; writing practices ... [more ▼]

The work has as main purpose to study the work of romance Hubert Juin trying to illuminate the paradoxes it contains: regionalist themes whose treatment goes beyond codes of regionalism; writing practices near New Roman, without the texts claim to this literary movement. This analysis is closely related to the biographical and poetic texts of the author. The approach is characterized, first, by the work of literary pragmatics developed by Dominique Maingueneau; secondly, by the work on the space novel done by Jean Weisgerber. [less ▲]

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See detailRésonance locale et caractérisation de défauts de délaminage par vibrothermographie
Demy, Philippe ULg

Doctoral thesis (2014)

La vibrothermographie est une méthode de thermographie active utilisée en contrôle non destructif qui présente des caractéristiques intéressantes et peu communes pour la détection de défauts. Cependant ... [more ▼]

La vibrothermographie est une méthode de thermographie active utilisée en contrôle non destructif qui présente des caractéristiques intéressantes et peu communes pour la détection de défauts. Cependant, la méthode souffre d’un manque de fiabilité des résultats lié au chaos acoustique inhérent à la nature du contact pour la stimulation. La principale innovation de cette thèse consiste à étudier et proposer une méthode alternative à la vibrothermographie classique à partir d’un couplage linéaire obtenu par collage. La mise en évidence et l’étude d’un phénomène de résonance locale de délaminage a permis la mise au point d’une technique performante et fiable pour la détection et la caractérisation de défauts dans les matériaux composites. [less ▲]

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See detailEtude des propriétés de surface et techno-fonctionnelles des fractions protéose-peptones
Karamoko, Gaoussou ULg

Doctoral thesis (2014)

The total proteose-peptone fractions are complex heterogeneous mixture of thermoresistant proteins of whey. The general objective of this work was to contribute to a better knowledge and understanding of ... [more ▼]

The total proteose-peptone fractions are complex heterogeneous mixture of thermoresistant proteins of whey. The general objective of this work was to contribute to a better knowledge and understanding of surface properties and techno-functional properties (foaming and emulsifying properties) and well as setting a relationship between the different properties. In this work, PPT fractions were extracted according to a classical approach and other industrially transposable by considering respectively the skimmed UHT milk and whey protein concentrate (WPC) as raw materials. The using of such both sources allowed to highlight the fundamental differences in the composition of the extracts of PPT. This has begotten a direct impact on the surfactant properties of the PPT. It has been therefore established that these differences at interfaces can have major consequences on their techno-functional behavior. This study also made it possible to determine the contribution of components especially non-hydrophobic and hydrophobic fractions in the interfacial behavior of PPT and the influence of pH, protein concentration, source and method of extraction. The setting in relationship of properties showed the existence of some statistically significant correlations between the interfacial parameters and, foaming and emulsifying properties. It will be therefore possible to predict the behavior of techno-functional PPT from some physico-chemical parameters. Finally, this study also showed that PPT fractions can be used as techno-functional agents in various food formulations based foams or emulsions. [less ▲]

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See detailPopulation ecology of coastal bottlenose dolphins (Tursiops truncatus) in Northern Patagonia Argentina
Vermeulen, Els ULg

Doctoral thesis (2014)

The population ecology of bottlenose dolphins (Tursiops truncatus) was assessed between 2006 and 2011 in Northern Patagonia, Argentina. Over these years, 356 systematic photo-identification surveys were ... [more ▼]

The population ecology of bottlenose dolphins (Tursiops truncatus) was assessed between 2006 and 2011 in Northern Patagonia, Argentina. Over these years, 356 systematic photo-identification surveys were conducted in Bahía San Antonio, of which 227 were land-based and 129 were conducted from a small outboard-powered rigid-hull inflatable boat. In total, 1472 h was spend searching for dolphins, and resulted in 215 h of observation of 415 dolphin groups. Photo-identification data resulted in the identification of 67 individual dolphins. Based on mark-recapture analysis, total abundance had a maximum corrected estimate of 83 (95%CI = 46 - 152) individuals. Adult survival rates varied between 0.97 (SE = 0.04) and 0.99 (SE = 0.01). Average calving interval of the 14 reproducing females equalled 3.5 ± 1.0 years. This results in 3.5 births/year in the entire population and a minimum annual birth rate of 4.2%. However, data suggest that calves may have been born and lost before being documented, underestimating birth rate, calf mortality and possibly the number of reproductive females. Either way, the recruitment rate of calves appears to be insufficient to compensate the overall mortality in the population. Additional data further indicated the genetic isolation and extremely low genetic diversity within this community, thus indicating this community of bottlenose dolphins is highly vulnerable and at risk. Association patterns within the studied community were relatively strong (HWI 0.30 ± 0.08), re-indicating the small size of the population. Nonetheless, the fluctuation in prey density and availability appeared to be the most important factor determining their fission-fusion dynamics. It appears that a combination of aspects inherent to the species and this habitat, such as low cost of locomotion, low predation pressure and food predictability, has helped reduce the costs of fission in response to intraspecific competition. Behavioural data indicated that Bahía San Antonio is mainly used to rest and forage, with a marked diurnal and seasonal pattern in their activity. Furthermore, dolphins appeared to show a preference for the shallower waters inside their core area; they moved in and out with the tide to remain in the intertidal zone as much as possible. The observed variation in foraging activity and spatial distribution is suggested to be driven by a seasonal and locally predictable variation in prey density and availability. Most of the identified dolphins showed a yearlong residency and long term site-fidelity to Bahía San Antonio, suggesting it is the core area within the larger home range of this community. Furthermore, based on the frequent presence of calves and high residency of reproductive females, this protected coastal environment appears to provide shelter for nursing calves. Many individuals of this community ranged along the entire northern coastline of the San Matías Gulf, up to the Río Negro Estuary (approx. 200 km). Further to the north, in the southern part of the Province of Buenos Aires, a neighbouring community of bottlenose dolphins was shown to exist. Both communities are largely isolated from each other, and the environmental discontinuities between two adjacent oceanic regimes in which these communities live are hypothesised to promote their co-existence. Additionally, four individuals from another community, originating from the more southern Province of Chubut, are known to reside in Bahía San Antonio. These individuals are genetically differentiated from all other individuals in the area, clearly shown in their distinct morphology. The apparent fine-scale population structure of bottlenose dolphins over the relative small geographical distances in Argentina has conservation implications and indicates the need for further detailed research. Currently, the populations of bottlenose dolphins in the Provinces of Buenos Aires and Chubut are reported to have nearly vanished. However, this disappearance has been largely ignored in the past 40 years resulting in the studied communities to be one of the last ones remaining in the country. It seems that the coastal lifestyle and site-fidelity of coastal bottlenose dolphins, and the belief of the species to be common, may have obfuscated the need for more extensive research and conservation efforts in Argentina in former years. Local declines of common species are easily overlooked when establishing priorities for conservation, and Argentina is not a unique case. An ever-increasing number of coastal bottlenose dolphin populations are reported to be vulnerable or declining worldwide. This study provides insight into how the failure to recognise local population declines can threaten the regional status of a common species like the bottlenose dolphin. Continued research and urgent conservation measures are therefore strongly recommended to prevent the disappearance of the bottlenose dolphin from the coasts of this South American country. [less ▲]

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See detailPoéticas del fracaso en la narrativa de David Toscana
Scheffer, Aurélie ULg

Doctoral thesis (2014)

Jusqu'à ce jour, l’œuvre de David Toscana (Monterrey, 1961) n'a été abordée par la critique que timidement et de façon partielle. Parmi cette maigre littérature critique, il est intéressant de remarquer ... [more ▼]

Jusqu'à ce jour, l’œuvre de David Toscana (Monterrey, 1961) n'a été abordée par la critique que timidement et de façon partielle. Parmi cette maigre littérature critique, il est intéressant de remarquer la fréquence d’occurrence d'un mot en particulier: “échec” (fracaso). Cette thèse se propose d'examiner les différentes manifestations intratextuelles de l'échec (Bärtschi et Leuzinger) dans l’œuvre toscanienne, c'est-à-dire, les formes fictionnelles de l'échec. Nous avons choisi de diviser notre étude en deux chapitres principaux: personnages et espace. Dans le premier, nous mettons en relation la notion d'échec et les divers protagonistes qui peuplent l'univers toscanien et tentons de comprendre dans quelle mesure ces derniers peuvent recevoir le qualificatif de “ratés” (fracasados). Plus concrètement, cette observation des personnages principaux favorise la réflexion sur ce que David Freundenthal appelle échec interne, en d'autres termes, l'échec très personnel et subjectif que ressent et vit l'individu, frustré dans ses désirs, ses projets et ses tentatives. À notre étude de l'échec interne correspond une perspective d'analyse interne: dans un premier temps, nous privilégions une approche de l’œuvre essentiellement orientée vers le texte même, et par conséquent, volontairement détachée de son contexte. Si nous optons pour ce type d'approche, nous nous refusons cependant à nous limiter à une analyse strictement thématique. Ainsi, nous pensons l'échec tant d'un point de vue thématique qu'en fonction de ses manifestations dans le processus d'écriture, c'est-à-dire, à travers les techniques et structures narratives appliquées au texte littéraire. L’œuvre du narratologue français Gérard Genette intitulée Figures III nous sert d'appui théorique dans l'appréhension des formes narratives de l'échec. Le second chapitre met l'accent sur la relation entre échec et espace narratif. En réalité, tous les personnages de Toscana partagent un même espace, le Mexique. Selon nous, la représentation que l'auteur fait de cet espace est à son tour inséparable de la notion d'échec. Aux antipodes des “foundational fictions” (Sommer), l’œuvre met en scène une nation désunie, incapable de se définir, d'assumer le passer et d'aller vers l'avant, incapable de synthétiser ses divergences, de respecter ses traditions, de s'identifier à un profil de valeurs propre. Ainsi, par exemple, la famille et la religion apparaissent, sous la plume de Toscana, comme des valeurs stériles et insubstantielles. Cette approche ne renvoie donc plus à l'échec interne mais bien à l'échec diagnostiqué de l'extérieur ou échec externe, selon l'expression de Freundenthal: indirectement et avec subtilité, Toscana postule le non-aboutissement d'un projet, celui qui aspirait à la constitution d'une nation mexicaine forte et cohésive, orientée vers l'avenir. Ce second chapitre repose sur les principes majeurs de l'analyse du discours. Pratiquer l'analyse du discours suppose l'acceptation que chaque phrase porte en elle un message qui la dépasse et dont le sens est à chercher tant dans son contexte d'énonciation que d’interprétation. Rejetant l'opposition traditionnelle entre texte et contexte, entre un “intérieur” et un “extérieur”, l'analyse du discours littéraire privilégie une conception du texte comme maillon d'une longue chaîne appelée “interdiscours” et qui correspond à “l'ensemble des unités discursives avec lesquelles un discours particulier entre en relation implicite ou explicite” (Charaudeau et Maingueneau 2005: 334). Le texte littéraire est donc à considérer “relationnellement et historiquement” (Meizoz 2010: 66) puisqu'il s'inscrit toujours dans un processus de communication, dans un échange réel ou virtuel avec la parole d'autrui. Adoptant cette perspective, nous décidons de chercher et de créer du sens à travers la mise en relation du texte toscanien avec un certain discours sur la mexicanité. En fait, l'échec se manifeste selon nous à travers la présence d'une série d'images nationales stéréotypées que l'écrivain régiomontain récupère et manipule à sa guise dans l'ensemble de son œuvre. De ce jeu avec les stéréotypes découle la construction d'un imaginaire national déterminé traduisant, de manière implicite et symbolique, l'échec de la nation mexicaine. Ainsi, nous insistons notamment sur l’affinité entre la fiction toscanienne et le célèbre discours sur la mexicanité d'Octavio Paz, énoncé dans son essai Le labyrinthe de la solitude. Plus que de simples traces de banalité, ces stéréotypes qui envahissent l’œuvre de Toscana constituent à nos yeux de véritables éléments narratifs dotés d'une fonction constructive et productive propre. La théorie des stéréotypes, une des nombreuses théories littéraires qui se revendiquent de l'analyse du discours, constitue le cadre théorique principal de ce second chapitre. [less ▲]

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See detailBodies of Evidence: An Anthropology of the Health Claim
Hendrickx, Kim ULg

Doctoral thesis (2014)

How can a food or food ingredient be proven healthy, without calling it a drug? In this thesis, I make an attempt at understanding the stakes of a heated debate involving scientists from the food industry ... [more ▼]

How can a food or food ingredient be proven healthy, without calling it a drug? In this thesis, I make an attempt at understanding the stakes of a heated debate involving scientists from the food industry, academia, and the European regulatory authorities. The centrality and importance of 'science' in the debate is remarkable, and merits our full attention. The 'science' that is disputed between 'industry' and 'the regulatory authorities', and that serves as a vehicle for their credibility and authority respectively, consists of a very particular practice of putting molecules to the test in clinical trials. The clinical trial in drug testing allows for making a qualitative leap from a molecule's biological action to its therapeutic effect. In the case of food, it is not permitted to define the molecule's therapeutics in relation to pathology, otherwise the substance tips over and becomes a drug. The shared concern of all scientists involved in the debate is to avoid this 'tipping point'. What the debate shows, is not so much an opposition between 'corporate science' and 'regulatory science', but an uneasy relationship between the ecology of pharmaceutical drugs, and an ecology-yet-to-be-made for food therapeutics. Such an ecology rests upon a pattern of collaboration -or agencement- between materials and humans pertaining to different realms of production, regulation and science. As such, the terms of the debate on healthy food ingredients can be reformulated in more precise terms than 'industry' versus 'the authorities', or 'good science' versus 'bad science', which only come to exacerbate a deeper-lying tension that is technical and political at once. At stake are our conceptions of health and disease, cure and prevention, and the professionals that have the authority to talk about health in present-day Europe. [less ▲]

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See detailrecherche de nouvelles potentialités des bacteries du genre Bacillus pour l'agriculture et l'agroalimentaire
Ait Kaki, Asma ULg

Doctoral thesis (2014)

L’exploration des échantillons en provenance de divers environnements de l’Est Algérien (du lac salé de Ain M’lila et de la rhizosphère d’une plante adjacente ; de l’eau de la source thermale d’Oued El ... [more ▼]

L’exploration des échantillons en provenance de divers environnements de l’Est Algérien (du lac salé de Ain M’lila et de la rhizosphère d’une plante adjacente ; de l’eau de la source thermale d’Oued El-Athmanya et du sol environnant ; de la rhizosphère de la plante Calendula officinalis, cultivée en serre à Setif) a abouti à l’obtention de 39 isolats de Bacillus et de Paenibacillus, dont 28 % sont sélectionnés pour leur capacité à inhiber la croissance de certaines moisissures phytopathogènes comme : Alternaria alternata, Aspergillus niger, Botrytis cinerea, Cladosporium cucumerinium, Fusarium oxysporium et Fusarium sp. Le calcul du taux d’inhibition de la croissance fongique par les isolats sélectionnés, réalisé, à titre d’exemple, sur F. oxysporium et B. cinerea, a permis d’obtenir des valeurs variant entre 39% et 84% suivant l’isolat. L’identification moléculaire des isolats sélectionnés par l’analyse d’ADN-16S et du gène « gyrase-A » a montré que les isolats de Ain M’lila appartiennent à Bacillus amyloliquefaciens, ceux isolés d’Oued El Athmanya sont : B. amyloliquefaciens, B. atrophaeus et B. mojavensis, enfin, les bactéries isolées de la rhizosphère de C. officinalis, sont : Paenibacillus polymyxa, B. velezensis, B. amyloliquefaciens et B. subtilis subsp. spizezenii. Les souches de Bacillus sélectionnées développent, dans les conditions de culture en fioles, des taux de sporulation importants variant entre 8 .108 et 27.108 spores/ml., alors que, le taux de sporulation chez P. polymyxa est insignifiant. Seuls les isolats de B. amyloliquefaciens sont capables de produire de la protéase. Cependant, l’activité cellulasique est observée chez toutes les espèces de Bacillus étudiées exceptant le B. atrophaeus qui a été le seul à produire de la chitinase. Toutes les espèces étudiées ont les mêmes capacités à produire les trois familles de lipopeptides (iturines, fengycines et surfactine), les siderophores et l’indole 3 acide acétique (IAA). Toutefois, le P. polymyxa (18SRTS) produit, dans les conditions expérimentales, une meilleure concentration d’IAA (54µg/ml). Par ailleurs, il est à mettre en exergue que, les B. amyloliquefaciens isolés du lac salé et de la source thermale produisent de nouvelles variantes de fengycines. En effet, il a été mis en évidence que le B. amyloliquefaciens (ET), produit de nouveaux homologues de fengycines A et B, ayant des chaines d’acides gras à 20 et à 18 atomes de carbone, respectivement, et deux nouvelles variantes de fengycines (fengycine X et Y) à cycles peptidiques dont la structure diffère de celle des fengycines conventionnelles. L’activité antifongique de certains isolats (B. amyloliquefaciens (ET), B. atrophaeus (6SEL), B. mojavensis (9SEL), B. amyloliquefaciens (9SRTS) et B. subtilis subsp. spizezenii (23SRTS)) sur milieux gélosés à base d’exsudats racinaires de tomate, de courgette et d’haricot, obtenus à différentes températures a été observée, vis-à-vis d’Alternaria alternata et de F. oxysporium. En complément, les souches B. atrophaeus (6SEL), B. amyloliquefaciens (9SRTS) et B. subtilis sub sp spizezenii (23SRTS), ont fait l’objet d’une production industrielle avec un taux de survie, après lyophilisation, très appréciable et leurs test in situ en serre et en champs sur le pois chiche a révélé une capacité intéressante de biofertilisation, de phytostimulation et de biocontrôle, ce qui justifie largement l’objectif assigné à cette recherche. [less ▲]

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See detailAssessing tropical forage species used as pig feed ingredients in the western provinces of the Democratic Republic of the Congo
Kambashi Mutiaka, Bienvenu ULg

Doctoral thesis (2014)

The use of forage species to feed pig goes back to immemorial times. If forage is no longer used in industrial farms with genetically-improved breeds, its accounts for an important part of pig diets in ... [more ▼]

The use of forage species to feed pig goes back to immemorial times. If forage is no longer used in industrial farms with genetically-improved breeds, its accounts for an important part of pig diets in smallholder pig production systems in tropical areas including the Western provinces of the Democratic Republic of the Congo (DRC). The aim of this research thesis was to assess the relevancy of the use of local forage resources as a strategy to reduce reliance of pig production systems on concentrate feed ingredients in tropical environment, by identifying plant species available to smallholders with interesting nutritional value that could partly replace concentrates in the diets. First, smallholder pig production systems in two western provinces of the DRC were characterized and the most used forage species in pigs identified. Their nutritional value was determined using an in vitro model of the pig’s gastro-intestinal tract. It was concluded that Manihot esculenta, Ipomoea batatas, Moringa oleifera, and legume species exhibit an interesting profile for feeding pigs while grasses, Eichhornia crassipes, Acacia mangium and Cajanus cajan should be discouraged. Feeding values of Psophocarpus scandens, Vigna unguiculata, Stylosanthes guianensis, and Pueraria. phaseoloides were measured by assessing the voluntary feed intake of forage hays-based diets and their digestibility. Finally, the economic impact of feeding Psophocarpus scandens, Vigna unguiculata, and Stylosanthes guianensis, was measured through growth performance, carcass quality, and production costs determination. It is concluded that although forage species reduce the nutritive value and the growth of animals, the investigated legumes do not impact negatively the economical balance of concentrate-fed pigs when forage accounts for approx. 10 % of the diet. The ability of some forage species to improve performances of animals fed ill-balanced diets as usually practiced by smallholder farmers in the DRC should be investigated as it is suspected that under less favourable conditions, conclusions on the usefulness of forage legumes in pigs might be more positive [less ▲]

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See detailLa conditionnalité environnementale dans la politique agricole commune. Analyse de l'intégration de la politique de protection de l'environnement au sein de la politique agricole commune
Habran, Maxime ULg

Doctoral thesis (2014)

Pierre angulaire de la construction européenne, la politique agricole commune (PAC) est à l’origine mise en place dans le but d’assurer l’autosuffisance alimentaire de la Communauté européenne. L’objectif ... [more ▼]

Pierre angulaire de la construction européenne, la politique agricole commune (PAC) est à l’origine mise en place dans le but d’assurer l’autosuffisance alimentaire de la Communauté européenne. L’objectif, rapidement atteint, laisse dans son sillage des stocks et excédents considérables ainsi que des dépenses communautaires importantes. Le mode de production agricole basé sur un modèle productiviste montre rapidement ses limites, obligeant les Etats membres à une réorientation de la PAC. Cette politique sera modifiée et réformée à de nombreuses reprises. La reconnaissance de la protection de l’environnement comme politique transversale contraint les Etats membres à l’adapter. D’une politique productiviste, elle devient attentive aux considérations environnementales, intégrant ces dernières dans chacune des réformes, allant même jusqu’à lier l’octroi de paiement au respect de règles essentiellement environnementales. Cette recherche présente la manière dont s’articule la relation entre les deux politiques autour de la notion de conditionnalité environnementale. A travers une étude minutieuse de chaque réforme de la PAC, une analyse de transversalité permet de saisir les enjeux et les motivations de l’intégration environnementale. [less ▲]

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See detailComputation and approximation of the inverse of relationship matrices between genotyped animals: Algorithms and Applications
Faux, Pierre ULg

Doctoral thesis (2014)

The recent developments in molecular biology have made available thousands of genetic markers, allowing livestock genotyping at a reasonable cost and the subsequent development of genomic prediction. The ... [more ▼]

The recent developments in molecular biology have made available thousands of genetic markers, allowing livestock genotyping at a reasonable cost and the subsequent development of genomic prediction. The single-step procedure, a unified approach of genomic prediction, requires inversion of two matrices gathering additive relationships between genotyped animals: the genomic relationship matrix (G) and a part of the additive relationship matrix (A22). The inverse of A22 may also be interesting for other applications. Matrix inverse can be constructed successively by, first, computing, for each animal, the vector containing contributions of other animals to its relationship and, secondly, adding the product of each vector of contributions by itself to a zeroed matrix. The objectives of this thesis were (1) to propose algorithms to compute or to approximate the vector of contributions and (2) to test the numerical efficiency of these algorithms (computing speed, memory use and, if needed, approximation accuracy). Computing contributions covered two points: (1) finding or approximating which contributions are different from zero, and (2) computing the value of contributions considered as non-zero. In the first approach, we considered that animals closely related have non-zero contributions and approximated their values by linear regression. This approach was extended in a recursive way. In the second approach, we empirically determined the set of non-zero contributions by a heuristic algorithm of pedigree exploration (only for the case of A22). Values were then computed either by linear regression, or using the already computed inverse. We also tested an approximation strategy: limiting the number of extracted generations of non-genotyped ancestors to reduce pedigree complexity. In a third approach, we followed the same heuristic algorithm as before but restricted the pedigree exploration to find out which animals have a non-zero contribution. Their values were approximated by linear regression. The presentation of the different approaches is followed by a general discussion in which the approaches are compared. It was found that the best compromise between speed, memory and approximation accuracy was achieved by the last approach for the case of A22. Use of this last approach simplified computations and therefore made predictions more feasible. However, for the case of G, no sufficient approximations could be reach in a reasonable time. Perspectives of other uses of algorithms developed and of future researches were drawn, as well as practical perspectives for animal breeding. [less ▲]

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See detailAnalyse et stratégies de développement de l’agriculture familiale dans un pays post-conflit: cas de la Province de Kirundo au nord du Burundi
Minani, Bonaventure ULg

Doctoral thesis (2014)

The Burundian family farming is indeed at the center of solutions to food and nutrition insecurity prevailing in Burundi. The agricultural sector contributes more than 40 % of GDP and employs 90 % of ... [more ▼]

The Burundian family farming is indeed at the center of solutions to food and nutrition insecurity prevailing in Burundi. The agricultural sector contributes more than 40 % of GDP and employs 90 % of active people. Kirundo famers practiced family agriculture market-oriented. This region was formerly considered as the breadbasket of the country because it fed many regions in cereals and legumes. Before 1993, Kirundo was the second rural province who had fewer households (28 %) living under poverty line. Today, this agriculture is consuming-oriented. Over 60 % of households in Kirundo Province live in food and nutrition insecurity, and 83 % of people live under poverty line. The objective of this study is to analyse underpinning constraints which hinder the system production performance of the region, in order to formulate strategies which can boost the family farming in Kirundo Province. In that case, a survey was carried out among 355 farm households in seven municipalities of the province. The results of this study showed that 282 farmers (79% of respondents) have small farmland and / or land conflicts as barriers to the family agriculture development. Contrariwise, the study identified also the existence of 73 farmers (21% of respondents) who didn’t have the small farmland and/ or land conflicts as constraints to the performance of their production systems. These farmers were divided into two groups: the first group (group A) included 41 farmers who were unable to fully exploit their land while the second group (group B) included 32 farmers who had a higher agricultural productivity. Thus, a case study was conducted with the farmers to know the core constraints which are impeding the land profitability in the first group (group A), and in other side, strategies implemented by other farmers in the group B to increase agricultural productivity. The results from this case study show that farmers partially exploiting their lands have an average area equivalent to 1.6 hectares per household, but only the third of this area is exploited. The crop yields (coffee, bananas, beans, maize, cassava, rice, sorghum, sweet potatoes, etc.) were lower than those observed at the national level. The main constraints of their lower production system performance are: the lack of agricultural workforce, this is lower because ( i) the rural exodus and early marriage of their children and departure of the household headers for seeking employment in Rwanda or in other family farms neighboring the regions, (ii) the lack of agricultural inputs, (iii) the lack of agricultural equipments, (iv) the use of moneylenders, (v) the insufficient erosion control techniques, (vi) the high rate of illiteracy,(vii) the poor distribution of organic manure between banana trees and other food crops, (viii) the persistence of traditional agro-pastoral techniques, (ix) the high animal mortality, (x) the low rate of households with fields in the lowlands and marshes, and (xi) the lack other opportunities outside the agricultural sector. Moreover, the strategies used by farmers with higher agricultural productivity for increasing the technical and economic performance of their production systems are: (i) the high rate of technology adoption (for erosion control, crop fertilization and pest management), (ii) the social development through the membership in local development associations well-structured and organized , (iii) the rational distribution of organic manure between banana trees and food crops , (iv) the application of modern agro- pastoral techniques, (v) the renewal of agricultural tools, (vi) the high rate of households with fields in the lowlands or marshes where they practice rice and other foods crops, (vii) the high literacy rate, (viii) the using of banks for credit, and (ix) the development of non-farm activities such as trade and crafts. The author concludes his study by recommending the development of non-farm activities, training farmers in modern agricultural techniques, the renewal of agricultural tools, the practices of food crops in the lowlands and marshes, and the development of small ruminants through the introduction of improved animal races and the practice of zero grazing as strategies to develop family farming in Kirundo Province. [less ▲]

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See detailImprovement of data quality for Diffusion Kurtosis Imaging and application to clinical neurological research
André, Elodie ULg

Doctoral thesis (2014)

Understanding human brain function and dysfunction is one of the major challenges of our century. One of the most popular methods to achieve this goal is in vivo magnetic resonance imaging. In particular ... [more ▼]

Understanding human brain function and dysfunction is one of the major challenges of our century. One of the most popular methods to achieve this goal is in vivo magnetic resonance imaging. In particular, diffusion-weighted (DW) imaging has become a standard tool to non-invasively study white matter structure in vivo. The main contributions of this work can be divided in two parts. The first part deals with the development of pre-processing methods to improve image quality and the accuracy of diffusion tensor and diffusion kurtosis-derived parameters. First, we describe and evaluate a novel method to correct data misalignment due to subject motion. Using an iterative model-based ap- proach, individual diffusion images are realigned to their own theoretical pair, rather than to the unweighted image. A recently developed advanced measure of tensor distance was used as a stopping criterion. The accuracy of the method is tested via a simulated diffusion tensor imaging data set. We have shown here that our procedure is a reliable and efficient way to correct subject motion during DW acquisitions, and that with a proper acquisition setup, it performs better than standard coregistration procedures. Next, we studied the influence of noise in diffusion kurtosis imaging. Two noise correction approaches are proposed and applied to a pool of 25 sub- jects to evaluate inter-subject variability and the impact of noise correc- tion. Additionally, data were acquired on a single subject with different head positions within the coil and different acquisition scheme to evaluate the impact of noise correction on within-subject variability. Results show a strong impact of noise correction on the estimated mean kurtosis, while the estimation of fractional anisotropy and mean diffusivity were less affected. Both within- and between-subject signal-to-noise (SNR) related variability of the mean kurtosis estimate is considerably reduced after correction for the noise bias, leading to more accurate and reproducible measures. In this work, we have proposed a straightforward method that improves the accu- racy of diffusion kurtosis metrics. Diffusion kurtosis imaging acquisitions at higher spatial resolution are made possible, which increases the chances to make valuable inferences in group analysis.The second part of this thesis deals with a clinical application of these meth- ods. A large group of patients with early-stage Parkinson’s disease was in- vestigated with diffusion kurtosis imaging and compared with a group of age- and sex-matched healthy volunteers using voxel-based analysis. Kur- tosis metrics show more sensitivity to white matter changes than standard diffusion metrics. Significant differences were found in posterior cerebral areas as well as subcortical regions like the putamen, and are therefore promising results. [less ▲]

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See detail"Je ne suis pas philosophe." Rousseau au miroir de l'épistolaire. Images de soi dans la correspondance de Jean-Jacques Rousseau (1730-1765)
Biquet, Stéphanie ULg

Doctoral thesis (2014)

L’objet de cette recherche consiste donc en une analyse de l’image de soi dans le discours épistolaire de Jean-Jacques Rousseau, depuis les premières années genevoises (vers 1730) jusqu’au départ pour ... [more ▼]

L’objet de cette recherche consiste donc en une analyse de l’image de soi dans le discours épistolaire de Jean-Jacques Rousseau, depuis les premières années genevoises (vers 1730) jusqu’au départ pour l’Angleterre (1765). Plus précisément, nous avons examiné le rapport que cette image entretient avec la figure du philosophe, qui fait l’objet d’une profonde reconfiguration au cours du XVIIIe siècle et qui nous semble une clé de lecture incontournable pour comprendre Rousseau. [less ▲]

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See detailDensité et écologie des chimpanzés (Pan troglodytes schweinfurthii) dans le Parc National de la Kibira, Burundi
Hakizimana, Dismas ULg

Doctoral thesis (2014)

Les forêts tropicales africaines et les communautés de primates qu'elles abritent sont sérieusement menacées par l'accélération des taux de conversion et de dégradation des forêts ainsi que par les ... [more ▼]

Les forêts tropicales africaines et les communautés de primates qu'elles abritent sont sérieusement menacées par l'accélération des taux de conversion et de dégradation des forêts ainsi que par les activités de braconnage. L'impact de ces menaces est si grand que certaines communautés de primates ont complètement disparu avant d’avoir été reconnues, encore moins étudiées. Des données référentielles sont toujours nécessaires pour comprendre les variations spatio-temporelles des primates. Les estimations de la densité ou d'abondance des populations sont des outils de première importance lors de la détermination des priorités de conservation et de la mise en place d’un plan de gestion des populations de primate. Comme dans les écosystèmes forestiers, la répartition et l’abondance des différentes espèces d’arbres influencent profondément les communautés animales qui y vivent, nous avons d’abord cherché à déterminer la densité et la structure des espèces d’arbres de la forêt de Kibira. Dans 256 plots couvrant une superficie de 32,15 ha, un total de 6.504 arbres répartis en 70 espèces, 67 genres et 37 familles ont été enregistrés. La densité était de 202 tiges par hectare, avec une surface basale de 21,05 m² par hectare. Au total, six espèces de primates diurnes ont été enregistrées dont une espèce anthropoïde (Pan troglodytes schweinfurthii), quatre cercopithecinae (Cercopithecus mitis, Cercopithecus mona denti, Cercopithecus lhoesti et Lophocebus albigena) et une colobinae (Colobus angolensis). Seule la densité et l’effectif total de la population des chimpanzés sont connus, tandis que pour le reste des espèces, seul l’indice d’abondance kilométrique a été calculé. Cette recherche a accordé une attention particulière à l’espèce emblématique du Parc National de la Kibira, le chimpanzé d’Afrique de l’est, Pan troglodytes schweinfurthii. Afin de mieux protéger cette sous-espèce en danger d’extinction, nous avons mené des investigations sur les sites de nidification pour identifier les espèces et les caractéristiques des arbres sur lesquelles les chimpanzés comptent pour la construction des nids. Les résultats ont montré que les chimpanzés sélectionnent certaines espèces d’arbres lors de la construction des nids. Le secteur Mabayi, situé au nord du parc, est le plus riche en espèces de primates; il abrite cinq espèces sur les six enregistrées, et deux espèces: Cercopithecus lhoesti (menacée) et Colobus angolensis ne se retrouvent qu’à Mabayi uniquement. Cette partie du parc constitue une clé pour la diversité et devrait par conséquent bénéficier d’une attention particulière en matière de protection et conservation. [less ▲]

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See detailEffets génomiques et non-génomiques de l'oestradiol lors de l'activation du comportement sexuel mâle
Seredynski, Aurore ULg

Doctoral thesis (2014)

Testosterone, via its estrogenic metabolites, is involved in the control of different behaviors such as social communication or reproduction. Estrogens act mainly at the genomic level via the activation ... [more ▼]

Testosterone, via its estrogenic metabolites, is involved in the control of different behaviors such as social communication or reproduction. Estrogens act mainly at the genomic level via the activation of nuclear receptors to regulate the transcription of target genes but also act at the non- genomic level via the activation of membrane receptors. The main question of my work was how these two types of actions of estrogens interact to control male sexual behavior. [less ▲]

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See detailRole of transcription factor sox4b in the differentiation of pituitary cells in zebrafish.
Quiroz O' Donova, Yobhana ULg

Doctoral thesis (2014)

The pituitary is a complex gland comprising different cell types each secreting specific hormones. The extensive network of signaling molecules and transcription factors required for determination and ... [more ▼]

The pituitary is a complex gland comprising different cell types each secreting specific hormones. The extensive network of signaling molecules and transcription factors required for determination and terminal differentiation of specific cell types is still not fully understood. The SRY-like HMG-box (SOX) transcription factor Sox4 plays important roles in many developmental processes and has two homologs in zebrafish, Sox4a and Sox4b. We show that the sox4b gene is expressed in the pituitary anlagen starting at 24hpf and later in the entire head region including the pituitary. At 48hpf, sox4b mRNA colocalizes with that for thyroid stimulating hormone (tsh), glycoprotein subunit  (gsu) and the Zn finger transcription factor Gata2a. Loss of Sox4b function, using morpholino knock-down or expression of a dominant negative Sox4 mutant, leads to a drastic decrease in tsh and gsu expression and reduced levels of gh, while other anterior pituitary gland markers including prl, slβ, pomc and lim3 are not affected. Sox4b is also required for expression of gata2a in the pituitary. Knockdown of gata2a leads to decreased tsh and gsu expression at 48hpf, similar to sox4b morphants. Injection of gata2a mRNA into sox4b morphants rescued tsh and gsu expression in thyrotrope cells. Finally, sox4b or gata2a knockdown causes a significant decrease of gonadotropin expression (lhβ and fshβ) at 4dpf. In summary, our results indicate that Sox4b is expressed in zebrafish during pituitary development and plays a crucial role in the differentiation of thyrotrope and gonadotrope cells through induction of gata2a expression in the developing pituitary. [less ▲]

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See detailModes d'Organisation et Distribution de l'eau: Une Evaluation empirique de la Performance par les Méthodes des frontières de production
Mande Buafua, Patrick ULg

Doctoral thesis (2014)

Cette thèse est une contribution à l’analyse empirique de la performance (efficacité technique et effectivité) dans le secteur de la distribution de l’eau en Afrique Subsaharienne. Nous cherchons à ... [more ▼]

Cette thèse est une contribution à l’analyse empirique de la performance (efficacité technique et effectivité) dans le secteur de la distribution de l’eau en Afrique Subsaharienne. Nous cherchons à répondre à la question de l’impact des modes d’organisation (participation du secteur privé, régulation et une combinaison de deux) sur l’amélioration de la performance dans ce secteur. Notre analyse s’appuie sur les données issues de la base des données de l’AICD pour la période 2000 à 2005. Premièrement, grâce au modèle de Battese & Coelli (1995), nous calculons les scores d’efficacité technique et nous identifions les sources de l’inefficacité technique. L’approche PLP nous sert de technique complémentaire pour approfondir l’examen des élasticités d’échelle et du coût implicite des pertes d’eau sur le réseau pour chaque opérateur. En moyenne, les entreprises de l’échantillon sont techniquement inefficaces sur la période. Réguler par contrat de performance conduit à des scores d’efficacité technique plus élevés que réguler par agence. La participation du secteur privé dans la gestion ou l’exploitation du service présente un effet positif sur l’efficacité technique. Il n’y a pas de preuve d’une différence significative entre l’efficacité technique des entreprises sous gestion publique régulées par contrat de performance ou par agence de régulation et celles avec participation du secteur privé dans la gestion ou l’exploitation régulées par contrat de performance ou par agence de régulation. Les élasticités d’échelle sont, en moyenne, décroissantes. Le coût des pertes d’eau sur le réseau est évalué, en moyenne, à 4 travailleurs pour 100.000 m³ d’eau perdue. De plus, ce coût marginal a tendance à augmenter avec les niveaux de la qualité du réseau. Deuxièmement, nous analysons notre question de recherche en prenant en compte la performance en termes d’effectivité. Nous nous appuyons sur la méthode DEA basée sur la procédure en double bootstrap (Simar & Wilson, 2007) en appliquant l’approche analytique, en 4 étapes, inspirée de Mbuvi et al., (2012). Les résultats laissent entrevoir l’existence d’un problème d’ineffectivité plus élevé que celui d’inefficacité technique. Ainsi, les opérateurs ont besoin des ressources additionnelles pour atteindre 100% de leur effectivité. Réguler par contrat de performance conduit à une plus grande effectivité que réguler par agence de régulation. La variable relative à la participation du secteur privé dans la gestion ou l’exploitation du service a un effet négatif et significatif sur l’effectivité. Enfin, il n’y a pas de différence significative, en termes d’effectivité, entre les entreprises avec participation du secteur privé dans la gestion ou l’exploitation régulées par agence ou par contrat de performance et celles publiques régulées par agence ou par contrat de performance. Enfin, nous évaluons l’impact des variables institutionnelles sur les taux de couverture du service en utilisant les modèles à effets fixes. Nous nous attaquons à la question de l’endogénéité en utilisant le cadre proposé par Heckman (1978). Réguler par contrat de performance a un effet positif et significatif sur les taux de couverture. La participation du secteur privé dans la gestion ou l’exploitation du service possède un effet négatif et significatif sur les taux de couverture du service. Combiner la gestion publique avec la régulation par agence ou par contrat de performance conduit à des taux de couverture du service plus élevés que combiner la participation du secteur privé dans la gestion ou l’exploitation du service avec la régulation par agence ou par contrat de performance. [less ▲]

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See detailReprésentations de l’environnement et adoption des pratiques durables de production par les cotonculteurs du Bénin
Assogba, Sonagnon Claude-Gervais ULg

Doctoral thesis (2014)

The research aims at contributing to a better understanding of the adoption of eco-friendly innovations. It analyses representations of environment and practices associated with sustainable management of ... [more ▼]

The research aims at contributing to a better understanding of the adoption of eco-friendly innovations. It analyses representations of environment and practices associated with sustainable management of cotton farming systems in order to deepen understanding of logics and strategies underlining farmers’ practices, and motivations that determine their sustainable farming system adoption behaviors. Organic cotton (SCBIO) and cotton made in Africa (SCMIA) systems were used as case study. Field research was carried out in Kandi and Pehunco in the largest area of cotton production in the North of Benin. The theoretical framework is based on the theories of technical change analysis, the actor-oriented approach and the theories of social representations. Data were collected from a sample of 90 organic cotton farmers and 100 CmiA farmers selected from a typology based on endogenous criteria of prosperity. 39 field agents from organizations promoting sustainable cotton farming system were surveyed. Individuals and groups interviews were used to collect data. The data were analyzed with a combination of qualitative and quantitative methods including normative and relative comparison analysis, perception analysis, descriptive statistics, analysis of variance, chi square test, etc. Results show a marginal contribution of organic cotton and cotton made in Africa to national economy in comparison to the conventional system. At farmer’s level farming system analysis reveals that both organic cotton and cotton made in Africa systems are not intensively sustainable. Their implementation is characterized by a large gap between recommendations and farmers’ practices, especially in soils’ fertility and pests’ management. The use of organic matters in combination with crops rotation including leguminous plants is the main approach of soils fertility management in organic cotton system. However, quantities of organic matters used, especially cow dung, are not sufficient due to its low availability and the lack of transportation means. The management of pests and diseases faces enormous constraints ranging from biopesticides production difficulties, weak efficiency of biopesticides, to observation of the evolution of parasitic complex, etc. Although the use of organo-chemical fertilizer is recommended in SCMIA system, more than 50% of SCMIA farmers apply only chemical fertilizer. Globally, the quantities of chemical fertilizer applied are under the requirements while the quantities of organic fertilizers are too small. Application of staged and targeted pest control (lutte étagée ciblée) is limited by constraints coming from the late implementation and the ineffectiveness of pesticides, the high number of observations needed, etc. Therefore, pesticides are used in overdose and prohibited pesticides such as endosulfan are also used. Consequently yields are very low and decrease. In addition, some farmers, especially from organic system, considering necessity of chemical fertilizers use for maize production develop diverse strategic logics such as misappropriation, craftiness, etc. to obtain these fertilizers. It appears from analysis that strategic logics carried out by farmers in farming systems’ adoption are the result of a combination of explanatory factors. These factors contribute to deepen the understanding of the weaknesses of organic and CmiA values chains in Benin and the bottlenecks in their development. Far from being static, farmers’ logics area temporary equilibrium resulting from different explanatory categories relative to social representations of environment, perceptions of projects and production and social reproduction objectives of farmers, the demand of sustainable cotton on international market, etc. Consequently, all actions aimed at promoting the sustainability of cotton farming system may facilitate access of farmers to inputs through the improvement of their existence means for a better soil fertility and pests management. Sensitization and training programs on the importance of leguminous plants integration to crops rotation, staged and targeted pest control, etc., may be carried out. At policy level it would be desirable that policies decisions don't negatively affect the development of alternative cotton value chains. In addition, measures may be taken to facilitate farmers’ access to chemical fertilizers for food crops, especially maize, to avoid their selling off. [less ▲]

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See detailImpact of micro-physics and macro-physics on the seismic properties of main-sequence B-type stars
Salmon, Sébastien ULg

Doctoral thesis (2014)

L’étude des pulsations stellaires, tout comme les ondes sismiques sur Terre, nous donne une méthode puissante afin de découvrir l’intérieur des étoiles. Cette discipline scientifique est aussi connue sous ... [more ▼]

L’étude des pulsations stellaires, tout comme les ondes sismiques sur Terre, nous donne une méthode puissante afin de découvrir l’intérieur des étoiles. Cette discipline scientifique est aussi connue sous le nom d’astérosismologie. Grâce aux missions spatiales CoRoT et Kepler, l’astérosismologie est entrée depuis dans une période faste. Par ailleurs, une frac- tion significative des étoiles présente des pulsations, ce qui nous permet de sonder leur intérieur pour la plupart de leurs stades d’évolution. Cette thèse se concentre sur les étoiles de type B de la séquence principale. Via l’inter- action de leurs vents stellaires avec leur milieu environnant et la production de nouveaux éléments chimiques en leurs intérieurs, elles contribuent aux processus dynamiques et d’enrichissement chimique du milieu interstellaire. Heureusement, deux types de pulsa- tion stellaire affectent ces étoiles: d’une part les pulsations dites de type β Cephei et d’autre part celles de type SPB. La nature de ces pulsations est sensible aux processus physiques internes de ces étoiles. Ainsi, l’observation de ces pulsations nous offre de sonder ces différents processus. Dans cette thèse, nous étudions tout particulièrement la sensibilité de ces étoiles aux opacités ra- diatives, et nous appuyant sur ces résultats, contraignons l’opacité radiative des éléments du groupe du fer à l’aide des étoiles pulsantes repérées dans les Nuages de Magellan. Dans une seconde étape, nous évaluons la possibilité de contraindre la nature du mélan- ge (diffusif ou overshooting instantané) à l’aide de la modélisation des β Cephei par l’ap- proche directe. Nous testons également les facteurs influençant la détermination de l’exten- sion de la zone mélangée. Enfin, nous proposons un scénario explicatif de la récente découverte d’une nouvelle classe d’étoiles variables dans un amas stellaire connu pour comporter de nombreuses étoiles en rotation rapide. [less ▲]

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See detailSimulation d’une Cellule Solaire Cristalline par la Méthode des Différences Finies & Fabrication, Caractérisation et Modélisation de Cellules Solaires à base d’hétérojonctions organiques distribuées en volume
Aazou, Safae ULg

Doctoral thesis (2014)

This thesis is devoted to theoretical and experimental studies of the basic device of photovoltaic conversion : the solar cell. First, renewable energies are highlighted in a general introduction and ... [more ▼]

This thesis is devoted to theoretical and experimental studies of the basic device of photovoltaic conversion : the solar cell. First, renewable energies are highlighted in a general introduction and their economic, ecologic and environmental advan- tages in comparison with fossil energy resources are emphasized, then, a revue of structure, types of bonds and energy bands of a solid material is presented and the case of a semiconductor is considered. Starting from Maxwell equations, the basic semiconductor equations namely Poisson’s equation and the continuity equations of electrons and holes are established. Next, discretizations of Poisson’s equation using a finite difference scheme and of the continuity equations by the Gummel-Scharfetter scheme are performed. The obtained system of equations is solved iteratively according Newton-Raphson algorithm. The experimental part of the work, entirely achieved in LIOS affiliated to JKU at Linz (Austria), aims the fabrication and the characterization of organic bulk heterojunction solar cells based on two different polymers used as donors P3HT and AnE-PVstat and the molecule PCBM as acceptor. A comparative study of the fabricated solar cells indicates that the device efficiency depends on the donor:acceptor ratio. In or- der to understand electronic and optical mechanisms occurring within a solar cell and which may affect its characteristics and performance, and to identify the role of the equivalent circuit parameters describing these mechanisms, many electronic circuits modelling the solar cell are presented and only the five physical parameters circuit is chosen. Several physical parameters extraction methods are exposed in details and only three of them are retained to extract the five physical parameters of the fabricated solar cells. The effects of each physical parameter on the solar cell efficiency are investigated. Thus, the variation intervals of the photovoltaic metrics, fill factor and efficiency under the influence of parameters variations can be identified. [less ▲]

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See detailModélisation des conditions d’apparition du micro-hydrodynamisme via la méthode des éléments finis dans la perspective d’intégrer ce phénomène dans un modèle numérique de laminage à froid.
Carretta, Yves ULg

Doctoral thesis (2014)

This dissertation presents a finite element numerical model able to predict the occurrence of Micro-Plasto-Hydrodynamic (MPH) lubrication. This phenomenon, which was first introduced by Mizuno and Okamoto ... [more ▼]

This dissertation presents a finite element numerical model able to predict the occurrence of Micro-Plasto-Hydrodynamic (MPH) lubrication. This phenomenon, which was first introduced by Mizuno and Okamoto, appears in the mixed lubrication regime. It consists in lubricant flows at the microscopic scale leading to a lubrication of the tool-piece solid contacts and therefore to a local friction drop. For instance, Laugier et al. have observed a friction decrease while rolling High Strength Steels for different strip thickness reductions. The only physical explanation to this trend is the MPH lubrication. Despite the huge influence of MPH lubrication on friction in metal forming processes, only a few numerical models can be found in the literature. Moreover, these models rely on several restrictive assumptions which prevent them from delivering predictive results. This work consists in the development of the first finite element model capable of predicting the appearance of the MPH lubrication. This model is used to numerically reproduce the experiments of Bech who studied this phenomenon, in plane strip drawing, by observing the behaviour of macroscopic pyramidal lubricant cavities through a transparent die. In the proposed approach, plane strip drawing is modelled in 2D with Metafor, an in-house nonlinear FE code. This model allows us to compare the lubricant pressure to the solid-solid contact pressure profile between the upper die and the strip material. Once the lubricant pressure exceeds the solid-to-solid contact pressure, the condition allowing a lubricant flow from the pocket to the neighbouring plateaus is fulfilled. The presented FE model is able to predict backward and forward escapes of the lubricant from the pocket. As in the experiments of Bech, several parametric studies have been carried out. The numerical results show that the model reproduces the trends observed experimentally. [less ▲]

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See detailLas políticas de representación del género en la escritura de la migración latinoamericana. Un análisis comparativo de El camino a Ítaca, de C. Liscano; Árbol de luna, de J. C. Méndez Guédez; y The Brief Wondrous Life of Oscar Wao, de J. Díaz.
Berlage, Pauline ULg

Doctoral thesis (2014)

The present thesis addresses the question of Latin-American migration literature by dealing with the subject from a gender perspective. This work brings into focus the politics of representation of bodies ... [more ▼]

The present thesis addresses the question of Latin-American migration literature by dealing with the subject from a gender perspective. This work brings into focus the politics of representation of bodies and migrant subjectivities in three works of narrative fiction from the end of the twentieth century and beginning of the twenty-first: El camino a Ítaca (1994), by Carlos Liscano; Árbol de Luna (2000), by Juan Carlos Méndez Guédez; and The Brief Wondrous Life of Oscar Wao (2008), by Domincan-American writer J. Díaz. Basing myself on that body of novels by male writers, I examine the way the subjectivity of gender-oriented register is combined with other “identity data” as class, race, ethnic differences and nationality. Moreover, this study focuses on the individual and collective re-subjectification process that the literary discourse transcribes through representation conventions in which the sexual and gender dimension is determining. The gender question is, therefore, discussed in terms of discursive aesthetic possibilities and is analysed in the particular cases of various literary migratory itineraries. Each novel is analyzed in the framework of the discursive production of Latin-American migration waves and in relation to the current debate over migrant literature. The literary analysis which focuses on concepts such as discursive ethos, the polysemy of “topic”, “corpo-graphy” and finally the concept of heterotopy. These will facilitate our understanding of migration in relation to the reshaping or reification of masculinity and feminity that are built followig some specific national norms. [less ▲]

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See detailDétection automatique des changements du bâti à partir des images satellitaires à haute résolution spatiale et des données cartographiques existantes.
El Mansouri, Loubna ULg

Doctoral thesis (2014)

La révision des données cartographiques (DC) est un processus réalisé actuellement d'une manière entièrement manuelle en cherchant les changements entre la donnée existante et une image plus récente ou ... [more ▼]

La révision des données cartographiques (DC) est un processus réalisé actuellement d'une manière entièrement manuelle en cherchant les changements entre la donnée existante et une image plus récente ou carrément par une nouvelle cartographique du territoire comme le cas au Maroc. La tâche étant lourde, lente et coûteuse, de nombreux travaux sont menés pour l'automatiser. L'idée développée dans plusieurs agences de cartographie collaborativement avec des institutions de recherche est d'adopter un mode de mise à jour semi automatique, où des procédures de détection automatique de changements sont mises en place pour extraire les zones de changement potentielles et les présenter à un technicien cartographe pour les valider avant de les intégrer à la DC à mettre à jour. Dans cette thèse, nous nous focalisons sur la détection des changements du bâti par comparaison automatique d'une carte numérique (CN) existante à une image satellitaire à haute résolution spatiale (HRS) plus récente, en vue d'une mise à jour semi automatique. L'approche proposée décompose le processus de détection de changements en deux étapes. Dans la première, les bâtiments sont extraits de l'image en se basant sur la classification de l'image pré-segmentée. Nous avons utilisé conjointement les avancées en algorithmes de classification d'images et les connaissances dérivées de la carte et des relations entre les objets urbains afin de s'affranchir des difficultés liées à l'extraction d'objets à partir d'images à HRS. Les objets de la carte sont intervenus à plus d'un niveau pour soutenir et automatiser l'extraction. Dans la seconde étape, la couche de bâtiments extraits est comparée à l'ancienne couche de bâtiments pour déduire les changements à l'échelle du "bâtiment". Ces changements représentent les mises à jour à valider par le technicien avant de les intégrer dans la carte. Nous illustrons l'efficacité de notre approche par des expériences menées avec une carte et une image QuickBird de la ville de Rabat au Maroc, qui connait depuis la dernière décennie une forte extension urbaine au détriment des zones de végétation. [less ▲]

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See detailÉvolution géomorphologique du littoral occidental de la péninsule tingitane (Maroc)
El Abdellaoui, Jamal ULg

Doctoral thesis (2014)

This work traces the geomorphological evolution of the western coast of the tingitane Peninsula (Morocco) in two time scales: the current scale and the Quaternary scale. Geomorphological characteristics ... [more ▼]

This work traces the geomorphological evolution of the western coast of the tingitane Peninsula (Morocco) in two time scales: the current scale and the Quaternary scale. Geomorphological characteristics have been identified and placed into their morphotectonic and/or morphodynamic contexts. To make our work more interesting, fruitful and realistic, we adopted an empirical approach. Firstly, we based our research on collection of data and analysis of available documents. Secondly, we made measurements, using appropriate techniques to answer specific questions, or to argue the hypotheses. It appears from this study, that the organization of geological units in a NNW-SSE direction has created a rugged shore, mainly in rocky cliff and pocket beaches on the Strait of Gibraltar coast, and a low sandy coast on the Atlantic coast. The geological and geomorphological quaternary history of Gibraltar Strait coast is characterized by a series of marine abrasion stepped and raised surfaces. The history of the Atlantic coast is rather marked by tectonic subsidence. This tectonic subsidence is manifested on the surface by a system of closed depressions (daya) arranged in a NNW-SSE axis, almost parallel to the orientation of geological units. The evolution of the geomorphological depressions is also controlled by the fluvio-marine action and wind activity. The last interglacial period is marked by two transgressive pulsations of eustatic origin. They were recorded at the marine terraces on both coasts. The second pulsation is aged at least 119.6 ± 2.3 ky. After the last interglacial, the central area of the Strait of Gibraltar was raised by an average of 8.1mm/100year from 117ky. The Ouljien was raised to a height of 13 to 16m. The Atlantic coast was stable at 117ky. Marine terraces are 5-6m high. The analysis shows that the current morphodynamics of the Atlantic coast are characterized by a barred beach geomorphology with a high spatio-temporal variability. It appears that a land wind plays a key role in the morphosedimentary evolution of backshore and foreshore. Indeed, the backshore develops, by negative retroaction, a geomorphology with a dune system to slow transport operated by land winds from the east. The foreshore, meanwhile, develops, by a positive retroaction, a system of bar and rip channels to counter a change in slope generated by the wind. On the one hand, risk analysis shows that the succession of anthropic changes at Tangier Bay has brooked the internal sediment balance. Erosion has affected both the sandy and rugged beaches of the eastern sector. The Atlantic coast doesn’t show signs of erosion, but it has a high vulnerability, because it evolves in a closed sedimentary system. On the other hand, the characteristic of a low open ocean coast facilitates the penetration of marine waters within the continent, especially the lower areas. Finally, a barred beach geomorphology creates problems of harbor silting and access disruption. [less ▲]

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See detailDevelopment and numerical validation of a 2-scale computational model to study the mechanical behavior of nanocrystalline metals
Péron, Vincent ULg

Doctoral thesis (2014)

This work aims at predicting the mechanical behavior of nanocrystalline structure using a 2-scale approach. Molecular simulations using the quasicontinuum method (QC) are performed to obtain the ... [more ▼]

This work aims at predicting the mechanical behavior of nanocrystalline structure using a 2-scale approach. Molecular simulations using the quasicontinuum method (QC) are performed to obtain the mechanical responses of the grain-boundaries and grains at the nanoscale. A finite element model is then calibrated using these atomistic results. This 2-scale model accounts for intergranular and intragranular plasticity, can predict the intergranular failure, and is able to study large structures. [less ▲]

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See detailImportant roles of SoHo proteins in vascular development: Sorbs1 and Sorbs2 have related but distinct functions in endothelial cells angiogenic properties
Bleuart, Anouck ULg

Doctoral thesis (2014)

Vascular system in all vertebrate organisms has in charge essential functions such as to bring nutrients, oxygen and signalling molecules to distant organs. Vascular network is established through ... [more ▼]

Vascular system in all vertebrate organisms has in charge essential functions such as to bring nutrients, oxygen and signalling molecules to distant organs. Vascular network is established through sequential and distinct processes. During embryogenesis, angioblasts give rise to differentiated endothelial cells, which form primary vessels through vasculogenesis. Expansion of this primary network is then achieved through a multistep process known as angiogenesis. During angiogenesis, remodelling of endothelial cell shape relies on cytoskeleton dynamics. In this study, our goal was to investigate the potential role of the SoHo family of adaptor proteins in angiogenesis. The SoHo family comprises three members, Sorbs1, Sorbs2 and Sorbs3. Although accumulative evidence links this protein family to the regulation of cell adhesion and actin cytoskeletal organisation, their expression and potential functions in endothelial cells remain unknown. Using zebrafish loss of function experiments combined with confocal imaging, we show that loss of Sorbs1 affects caudal vein-derived vessel formation, whereas Sorbs2 depletion impairs ISV development essentially derived from the dorsal aorta. We then demonstrated that both members impact on EC behaviour via regulation of RhoGTPases activity, leading to the vascular defects observed in vivo. Using a series of in vitro functional assays, we found that Sorbs1 and Sorbs2 have opposite effects on adhesives properties of HUVECs related to their ability to regulate different RhoGTPases. Sorbs1 depleted ECs adhere excessively to the ECM due to decrease in Rac1 activity. In contrast, loss of Sorbs2 impaired RhoA activation during adhesion and decreases cell adhesiveness to the matrix. Interestingly, these opposite effects on cell adhesion lead to similar outcome on EC migratory abilities, a decrease in cell migration. Here, for the first time, we establish a role for Sorbs1 and Sorbs2 in angiogenesis and demonstrate that these SoHo members are essential for EC adhesiveness and subsequent migratory abilities. [less ▲]

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See detailExtension of the Direct Strength Method to hot-rolled and welded H profile cross-sections
Li, Yongzhen ULg

Doctoral thesis (2014)

The cross-sectional capacity is limited by material yielding on one hand and local buckling on the other hand. Most current metallic structural design codes use the concept of section classification for ... [more ▼]

The cross-sectional capacity is limited by material yielding on one hand and local buckling on the other hand. Most current metallic structural design codes use the concept of section classification for determining the section capacity of hot-rolled profiles. In this system, there exists a discontinuity between the classes 2 and 3 under pure bending load condition, while for the class 4, the effective width method (EWM) must be used to account for local buckling phenomenon. With the appearance of the more complex cross-sections, especially for thin-walled steel structures, the calculation using EWM becomes more and more intolerable and complicated. In order to overcome these difficulties when evaluating the cross-section strength, the alternative Direct Strength Method (DSM) approach, developed only for cold-formed thin-walled members, has gained importance over the last few years, and has been adopted by the North American and Australian standards for the design of cold-formed steel structural members recently. This thesis investigates the possibility to extend the DSM method to hot-rolled and welded structural steel members, and the objective is to derive a new formulation that would cover the whole field of section slenderness without section classification system used in Eurocode 3, using the same procedure for the DSM developed for cold-formed thin-walled steel structural members. Hot-rolled and welded H sections are mainly considered in this thesis. The DSM is premised on the assumption that the strength can be predicted from the yield strength to the elastic critical load ratio used in conjunction with a strength curve; i.e. the same concept than the one used in Eurocode 3, in terms of member buckling phenomenon. In the DSM approach applied for cold-formed thin-walled sections, local buckling and distortional buckling modes should be considered. For common hot-rolled or welded sections, only local buckling needs to be considered since distortional buckling does not occur for these sections. All available test results in literature are collected and evaluated with the current methods for calculating the cross-section resistance such as EWM, DSM, and the recent Continuous Strength Method (CSM). A short comparison is made and their domains of applicability are commented. A consistent approach has been adopted to develop numerical models for hot-rolled and welded sections subjected to compression and bending respectively. The FE model was built in FineLg and verified against test results of the “Semi-comp: Plastic member capacity of semi-compact steel sections - a more economic design” project, which was carried out earlier with the objective of improving the utilization of plasticity in rolled and welded sections with medium cross-section slenderness. Measured material and geometric properties, initial geometrical imperfections and residual stresses distributions have been highlighted. Once verified against the test results, the FE models have been used to carry out a parametrical study aimed at providing more FE results and highlighting the local buckling interaction between the webs and the flanges. All the experimental and FE numerical results constitute data base for the derivation of the new DSM curves. On the basis of Winter Formula for plate buckling and the generic DSM strength curve, different formulas are proposed for hot-rolled and welded H cross-sections under axial and bending load respectively. Also the statistical evaluation and safety study is conducted to obtain the safety factor γ_M, which is required for practical design. [less ▲]

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See detailIdentification et rôle des médiateurs sonores dans les phases de colonisation et d’installation de poissons dans un environnement corallien
Berten, Laetitia ULg

Doctoral thesis (2014)

La majorité des poissons de récifs coralliens présentent un cycle de vie complexe, caractérisé par une phase larvaire pélagique dispersive en milieu océanique, suivie d’une phase benthique au sein du ... [more ▼]

La majorité des poissons de récifs coralliens présentent un cycle de vie complexe, caractérisé par une phase larvaire pélagique dispersive en milieu océanique, suivie d’une phase benthique au sein du lagon ou sur la pente externe du récif. Ce travail porte sur l'influence du stimulus sonore lors de la colonisation et de l'installation, au sein du récif, des larves de poissons. De récentes études ont montré un effet attracteur du son de récifs sur les larves de poissons et de crustacés. Mais on ignore encore la distance à laquelle les larves sont capables de repérer le son du récif, ni si elles sont attirées par une signature spectrale complexe ou plus simplement par la présence d'un "bruit". Enfin, on ignore si les différents habitats d’un récif peuvent présenter des signatures acoustiques propres, ni si les sons des habitats peuvent guider les larves lors de leur installation au sein du récif. L'étude de mesures de pression sonore le long de trois transects de 2 km effectuées sur la côte nord de l'île de Moorea (Polynésie Française) met en évidence une diminution régulière de l'intensité sonore jusqu'à une distance à la crête de 750-1000 m. Au-delà de cette distance, et jusqu'à 2 km, une augmentation graduelle de la pression sonore est observée. Dès lors, une larve située à 750-1000 m du récif se retrouve confrontée à deux gradients de pression, l'un dirigés vers l'océan et l'autre vers le récif, et devra faire appel à d'autres stimuli pour s'orienter vers ce dernier. Au sein du récif, les sons provenant de 5 habitats de Moorea (crête interne, récif barrière, récif frangeant, chenal et mangrove) ont été étudiés. Les signatures sonores de chaque habitat (hormis crête interne et récif barrière) diffèrent des autres sur une certaine gamme de fréquences, et ces différences sont conservées avec la distance (plusieurs km). De plus, l'étude de l'influence des sons d'habitats et d'un son artificiel sur le comportement des larves met en évidence une modification du comportement chez 16 des 20 espèces testées. Les différentes réponses illustrent deux stratégies d'installation sur base du son: soit une sélection directe de l'habitat, soit un évitement de certains habitats, et donc une sélection "par défaut" des habitats restants. Pourtant, les niveaux de pression sonore des habitats du lagon sont sous les seuils de capacités sonores des juvéniles d'Abudefduf vaigiensis, Acanthurus triostegus, Chaetodon citrinellus, Rhinecanthus aculeatus et Myripristis kuntee. Ce paradoxe nous pousse à remettre en question l'utilisation de l'outil "ABR" (Auditory Brainstem Response) dans les études de perception et d'influence des sons sur le comportement des poissons. [less ▲]

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See detailNew perspectives on probabilistic methods for nonlinear transient dynamics in civil engineering
Canor, Thomas ULg

Doctoral thesis (2014)

The objective of this thesis is to develop probabilistic methods to perform nonlinear transient analysis in civil engineering applications. The manuscript is divided into two parts. For large-dimensional ... [more ▼]

The objective of this thesis is to develop probabilistic methods to perform nonlinear transient analysis in civil engineering applications. The manuscript is divided into two parts. For large-dimensional structures subject to coherent random loads, an asymptotic expansion-based method is used to improve linear evolutionary spectral analysis. Then, this method is extended to equivalent statistical linearization by a multiple timescales approach. The second part of the thesis is focused on small-dimensional systems. It explores the solution of the Fokker-Planck equation with the smoothed particle hydrodynamics method. This meshless Lagrangian method particularly ensures the conservation and the positivity of the probability field. The accuracy and efficiency of both approaches are compared with Monte-Carlo simulations. [less ▲]

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See detailCaractérisation des modes de consommation alimentaire des ménages à Kinshasa : analyse des interrelations entre modes de vie et habitudes alimentaires
Muteba Kalala, Damien ULg

Doctoral thesis (2014)

This study was initiated at the start of a hypothesis that households are in a situation of food insecurity when their lifestyles and livelihoods have changed or have not adapted and they have not the ... [more ▼]

This study was initiated at the start of a hypothesis that households are in a situation of food insecurity when their lifestyles and livelihoods have changed or have not adapted and they have not the ability to find a balance between a set of needs. Households’ food demand cannot be analyzed independently from all livelihoods and living conditions. For this study, a methodology based on household surveys was adopted. Based on their supposed wealth level, three districts were selected, the Residential Area in Limete, the Mabulu neighbourhood in Makala and Quarters I and VII in Ndjili. A sample of 346 households was selected. The results of the first survey on the characterization of households have achieved the first three objectives of the study. The second survey consisted of a household monitoring defined according to specific criteria. Thirty households were selected at the rate of 10 in each of three quarters. They were followed first during the dry season for three months, from June to August 2011, and subsequently in the rainy season for three months also between February and April 2012. The results of this study show among other things that food expenditures are much higher in the rainy season than in the dry season. However, the quantities consumed are relatively higher in the dry season than in the rainy season. The amount of food consumed per person per day was estimated in the dry season respectively at 1.202g (in the richest households), 833g (in average households) and 506g (in poor households). During the rainy season, quantities consumed are respectively of 1.120g (in the richest neighborhood), 801g (in the average households) and 493g (in less well-off households). Energy intake per person per day in the dry season is respectively 2571 calories (in the richest households), 1.864 calories (in average households) and 1,094 calories (in poor households). Energy intake was also lower in the rainy season. It reaches respectively 2.452 calories (in wealthy households), 1,838 calories (in average households) and 1,130 calories (in poor households). Protein intake per person per day was estimated in the dry season respectively at 102g (wealthier households), 81g (in average households) and 51g (in poor households). During the rainy season, these contributions are also low. They are around of 100g in the wealthier households, 80g in the average households and 50g in poor households. The analysis of different consumption patterns showed that the dietary habits of Kinshasa do not seem to meet the nutritional requirements. Considerations between the two parameters show that households are scarcely managing to find a balance. The evidence supporting this difficult balancing includes: food monotony in households, the tendency to promote the consumption of cheap food, food choices unrelated to dietary considerations, the appearance of more and more public health problems related to food consumption patterns. However, the dietary imbalance in Kinshasa households is not always linked to income. [less ▲]

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See detailEntre recettes du Soi et recettes de l'Autre. Ethnographie de pratiques culinaires marocaines à Sesto San Giovanni (Milan, Italie)
Mescoli, Elsa ULg

Doctoral thesis (2014)

La thèse porte sur les processus de subjectivation d’un groupe de femmes marocaines résidant dans la ville de Sesto San Giovanni, dans le nord de l’Italie. Elsa Mescoli considère les habitudes ... [more ▼]

La thèse porte sur les processus de subjectivation d’un groupe de femmes marocaines résidant dans la ville de Sesto San Giovanni, dans le nord de l’Italie. Elsa Mescoli considère les habitudes alimentaires et les pratiques culinaires de ces femmes et de leurs familles, facteurs qui agissent dans la construction de soi à plusieurs niveau : celui intime, en contexte domestique ; celui partagé/contesté, en contexte publique. L’étude se situe au croisement entre l’anthropologie de l’alimentation, l’anthropologie de la culture matérielle et l’anthropologie des migrations. En fait, ces processus sont analysés en adoptant une perspective praxéologique, c’est-à-dire en portant l’attention sur la matérialité. La thèse met en évidence les « ingrédients » concrets de la définition de soi des femmes considérées, ainsi que de leurs rapports interpersonnels et « interculturels ». [less ▲]

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See detailEtude des propriétés des variants amyloïdogéniques du lysozyme humain à l’aide de fragments d’anticorps à chaînes lourdes comme sondes structurales
Dumont, Janice ULg

Doctoral thesis (2014)

Les fibres amyloïdes sont des agrégats de protéines hautement organisés qui sont associés à une trentaine de maladies appelées amyloses, dont les maladies d'Alzheimer et de Parkinson et la maladie de la ... [more ▼]

Les fibres amyloïdes sont des agrégats de protéines hautement organisés qui sont associés à une trentaine de maladies appelées amyloses, dont les maladies d'Alzheimer et de Parkinson et la maladie de la vache folle. L'amylose systémique à lysozyme est une amylose non-neuropathique héréditaire associée à sept variants de la protéine (Y54N, I56T, F57I, W64R, D67H, F57I/T70N et W112R/T70N). Ces protéines forment des fibres amyloïdes extracellulaires qui se déposent dans de nombreux tissus et organes tels que le foie, la rate et les reins. Il a été montré que les mutations I56T et D67H diminuent la stabilité et la coopérativité globale de la protéine. Ainsi, dans des conditions proches des conditions physiologiques, ces variants forment, in vitro, transitoirement un état intermédiaire dans lequel le domaine β et l'hélice C se déplient de manière coopérative, alors que le reste du domaine α conserve sa structure native. La formation d'interactions intermoléculaires entre les régions dépliées serait à l'origine du processus d'agrégation qui conduit à la formation et au dépôt de fibres amyloïdes dans les tissus des patients porteurs de ces mutations. Il a également été montré que la liaison de trois fragments d'anticorps à chaînes lourdes de camélidés (VHH), dirigés contre le lysozyme humain de sauvage, inhibe in vitro la formation de fibres amyloïdes par les variants D67H et I56T. Ces trois VHH se lient à des régions différentes du lysozyme et inhibent la formation de fibres amyloïdes selon différents mécanismes. Au cours de ce doctorat, seize nouveaux VHH spécifiques du lysozyme humain ont été générés. Des expériences de liaisons compétitives suivies par résonnance plasmonique de surface ont montré que les 16 VHH se lient à cinq épitopes distincts à la surface du lysozyme. Quatre d’entre eux sont capables de se lier au lysozyme dans les conditions utilisées in vitro pour induire la formation de fibres amyloïdes par les variants du lysozyme. Leur site de liaison a été déterminé par RMN. Deux d'entre eux reconnaissent des épitopes différents de ceux des trois VHH caractérisés précédemment. Des expériences d’échange H/D analysés par spectrométrie de masse ont montré que les 4 VHH ont des capacités différentes à restaurer la coopérativité globale du variant D67H du lysozyme. L’analyse de l’ensemble des résultats nous a permis d’identifier qu'elles sont les régions du lysozyme qui doivent être affectées par la liaison d'un VHH afin de restaurer la coopérativité globale de la protéine. La liaison simultanée aux deux domaines (i.e. α et β) semble être le dénominateur commun de tous les VHH restaurant la coopérativité globale du variant D67H. La liaison aux hélices B et C, ainsi que de l'interface des deux domaines semble aussi contribuer à la restauration de la coopérativité globale. A l'inverse, une liaison qui perturbe la partie N-terminale ne permet pas de restaurer la coopérativité globale de la protéine. La liaison d’un VHH, cAb-HuL9a, au variant D67H du lysozyme inhibe de manière similaire la formation de l’intermédiaire partiellement déplié, l'élongation de fibres amyloïdes préformées et la formation de fibres amyloïdes in vitro. Cette observation est en accord avec l’hypothèse selon laquelle, la formation de cet intermédiaire est à l’origine de l’amyloïdogénicité des variants du lysozyme. Afin d'étudier les effets des mutations amyloïdogéniques récemment identifiées sur les propriétés du lysozyme et ainsi obtenir une meilleure connaissance du mécanisme de formation des fibres amyloïdes, il est nécessaire de produire ces variants en grande quantité. Les variants D67H, I56T et F57I sont produits dans Aspergillus niger. L'expression des variants dans ce micro-organisme est toutefois particulièrement chronophage alors que les rendements de production sont relativement faibles. Les tentatives d'utiliser d'autres systèmes de production tels que Pichia pastoris ou le système bacculovirus n'ont pas été concluantes. Aussi, dans le cadre de mon doctorat, j’ai étudié la possibilité de produire le variant D67H sous forme de corps d'inclusion dans Escherichia. coli. Un protocole permettant de produire 20 mg de protéine sous forme de corps d’inclusion par litre de culture a été développé. Différents stratégies ont été testées pour replier la protéine à partir des corps d’inclusion. Cette approche a permis d’obtenir une protéine ayant 90% d’activité spécifique du lysozyme. Le rendement massique obtenu après repliement est néanmoins très faible. [less ▲]

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See detailMultiscale modelling of angiogenesis during normal and impaired bone regeneration
Carlier, Aurélie ULg

Doctoral thesis (2014)

Bone regeneration is, like many other healing events, a complex, well-orchestrated process involving a myriad of different cell types and regulated by countless biochemical, physical and mechanical ... [more ▼]

Bone regeneration is, like many other healing events, a complex, well-orchestrated process involving a myriad of different cell types and regulated by countless biochemical, physical and mechanical factors. But unlike other adult biological tissues, the majority of bone fractures can heal without the production of scar tissue, eventually recovering the original bone shape, size and strength. Despite bone’s remarkable healing capacity and the continuing research efforts, the impaired healing of complex orthopaedic cases is still not fully understood. This PhD work hypothesises that computational modelling can make a substantial contribution to the bone regeneration field by proposing and testing the underlying mechanisms of action as well as by designing and optimising experimental strategies in silico. In the first part of this work, an existing bioregulatory model of fracture healing is extended with an intracellular module of Dll4-Notch1 signalling in order to capture the ingrowth of new blood vessels through sprouting angiogenesis. The predictions of the new MOSAIC model are compared to experimental results and an extensive sensitivity analysis is performed on the newly introduced parameters. The potential of the MOSAIC model to investigate the influence of the molecular mechanisms on angiogenesis and consequently the bone formation process is illustrated. In the second part of this work, the MOSAIC model is further improved with a rigorous implementation of the influence of oxygen on the behaviour of skeletal cells. A comprehensive literature study is performed in order to ensure the correspondence of the oxygen ranges of the cell-specific oxygen-dependent processes with the state-of-the-art experimental knowledge. The oxygen model is corroborated with previously published experimental results. The robustness of the oxygen model with respect to the newly introduced oxygen thresholds is demonstrated by a sensitivity analysis. Some limitations and shortcomings of the oxygen model are identified together with suggestions for future work. In the last part of this work, the added value of the oxygen model is shown by applying it to three cases of impaired bone healing: the occurrence of nonunions in critical size defects, bone graft healing in a compromised environment and the impaired healing of bone fractures in NF1 patients. Not only is the oxygen model used to determine the underlying mechanisms of action, potential treatment strategies for the respective challenging orthopaedic conditions are also designed and optimised in silico. In conclusion, this PhD thesis demonstrates the potential of an integrative in vivo-in silico approach to advance our current understanding of bone regeneration as well as to design effective treatments of complex bone fractures. [less ▲]

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See detailÉtude des Culicoides Latreille (Diptera: Ceratopogonidae) vecteurs d'agents pathogènes: état des lieux des espèces belges, de leurs micro-habitats larvaires et de leurs préférences trophiques
Zimmer, Jean-Yves ULg

Doctoral thesis (2014)

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are the biological vectors of many recently described pathogens in Northern Europe, including the Bluetongue and Schmallenberg viruses ... [more ▼]

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are the biological vectors of many recently described pathogens in Northern Europe, including the Bluetongue and Schmallenberg viruses. These arboviral diseases have led to considerable economic loss in sheep and cattle livestock. However, many uncertainties remain regarding the distribution, biology, and ecology of these vectors. This research project had three main objectives. The first objective was to conduct an inventory of the different Culicoides species on different Belgian farms and on wetlands, using light traps. Many more Culicoides were caught in the vicinity of buildings than in meadows; this finding seemed to be influenced by the density of hosts near the trap and the opening of buildings. The Obsoletus complex was predominant inside buildings and in the meadows of farms; however, the meadows exhibited greater species diversity. The oligotrophic species C. impunctatus, a potential vector of several pathogens, was particularly abundant in peat bogs. The traps that were used herein enabled the identification of three species that have not previously been reported in Belgium, bringing the total number of Belgian species to 52. The second objective was to identify and characterize larval microhabitats of the main Belgian species of Culicoides, and to study the distribution of coprophilous species (C. chiopterus and C. dewulfi) in meadows. Ten Belgian cattle farms were monitored for two consecutive years, and sixteen substrates conducive to the larval development of these biting midges were identified. The most significant finding was that different types of silage residues (e.g., corn, grass, beet pulp, and their combinations) were favourable to the larvae of the two species that compose the Obsoletus complex. A larval microhabitat that is appropriate to these two species was also identified, for the first time, directly inside a barn: specifically, within the dried dung stuck to the barn walls and resulting from the partial removal of used litter. Therefore, Culicoides could complete their life cycle in the vicinity of the stables, which might explain the persistence of the virus from one year to the next despite harsh winters. Influences of the carbon-to-nitrogen ratio, lignin, insoluble fibre, magnesium, and calcium on the presence of larvae were also examined. The third objective was to study the feeding preferences of the species C. obsoletus. This species is prevalent on Belgian farms and has considerable medical and veterinary relevance. Behavioural analyses were performed under field and laboratory conditions, respectively through a flight tunnel containing potential hosts (human, calf, sheep and chicken) and a two-choice olfactometer containing volatile extracts of host skin. The field experiment revealed the preference of C. obsoletus females for large hosts, probably caused by greater emission of carbon dioxide. In contrast, these midges were more attracted to volatile organic compounds released from the skin surface of chicken and sheep during the laboratory experiment. This study contributed to improve the fundamental knowledge of Palaearctic species of the genus Culicoides, and highlighted promising avenues to control these biting midges. Knowledge of the breeding sites of Culicoides could thus allow substrates to be monitored and control or hygiene measures to be implemented, while preventing new sites from being created. A better understanding of the vector-host interactions may aid in developing new strategies to control adult midges, while improving understanding of the pathogen transmission cycle and the epidemiology of associated diseases. [less ▲]

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See detailControl of attosecond electronic dynamics in molecules
Mignolet, Benoît ULg

Doctoral thesis (2014)

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See detailLe rôle du commerce frontalier des produits alimentaires avec le Rwanda dans l'approvisionnement des ménages de la ville de Bukavu (Province du Sud-Kivu)
Vwima Ngezirabona, Stany ULg

Doctoral thesis (2014)

This thesis aims at highlighting the importance of food supply from the Rusizi District (Rwanda) in the food security of the city Bukavu (Democratic Republic of Congo). Due to the informal nature of this ... [more ▼]

This thesis aims at highlighting the importance of food supply from the Rusizi District (Rwanda) in the food security of the city Bukavu (Democratic Republic of Congo). Due to the informal nature of this supply, it was necessary to characterize its magnitude, drivers, and consequences as well as to develop policies that are likely to improve this supply and facilitate regional integration. The fieldwork consisted of two series of investigations. The first series of data collection included scoring the flow of food supply from Rusizi District during three months and for each of the food supply axes of Bukavu city. Secondly, a questionnaire was administered to a sample of 233 households, wherein 76 consuming households and 157 reselling households. Results from the scoring exercise show that 2,021 households on average cross both borders (Rusizi 1 and Ruzizi 2) for their food supply daily. A total of 661 of these households (about 32.7%) are direct food consumers and 1,360 households (about 67.3%) are food resellers. Excepted for cassava (which is a traditional staple of South Kivu), plantains (because of conservation problem, much more coming from within the province), and beans (much more from North Kivu), other major food products are imported from Ruzizi district in Rwanda. In this regard, the dependency ratios towards Rwanda remain much higher for products such as maize (66%), potatoes (82%), sorghum (73%), groundnut (69%), sweet potato (98%), rice (70%), and beef and pork meat (85%). With such dependency ratios, Bukavu is a major food market of the Rusizi District (Rwanda) food products. This is however far from being confirmed by official import statistics of the Congolese Control Office (CC0) which, except for rice, underestimates the border trade for a large portion of food commodities flows. The commodities analyzed provide the population of the city of Bukavu 1027 kcal per person per day from which 593.5 kcal, 338.9 kcal and 92.4 kcal are provided by products respectively from Rwanda, North-Kivu and South-Kivu. The calories consumed in the city of Bukavu are mainly of vegetable origin dominated by maize (563.1 kcal), cassava (120 kcal) and beans (167.1 kcal), which play a strategic role given their importance in the food habits of Bukavu. The significant flows of food supplies from Rusizi district are a major contribution to the livelihood of thousands of families in the city of Bukavu. It emerges that all products supplied from Rusizi district by reselling households generate positive return per month demonstrating a positive remuneration not only for the invested capital, but also for the time and effort invested in the activity (average 5.67 hours). More than 68 % of reselling households claim are satisfied with the result of this activity and allocate the generated income mainly to cover subsistence needs. In this sense, the economic impact of border trade on incomes of reselling households is a reality. The analysis of budgets of consuming households shows that 69.1% of food expenditure and 48.8% of total expenditure of consuming households cross the border. The significant impact of food supplies from the Rusizi district on reducing households’ income poverty, reflects the interests of border trade which only reinforces the structural and relative decline of the agricultural sector in South Kivu already confronted to various problems. The free trade policy advocated by a large number of sub-regional and regional communities such as CEPGL and COMESA will make the Rusizi originating food supply of Bukavu more efficient, but it remains a short-term solution of food security of the city and the province in general. In the long term, it would be better to stimulate the production and promote local food trade. To achieve this, investments need to be channeled to the agricultural sector. It is at this price that the agricultural sector in South-Kivu can be revived and reach the threshold of self-sufficiency, and even create a surplus for export. Admittedly, this solution then poses the problem of reconversion of consuming households and sellers-households that we should rethink from the outset. [less ▲]

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See detailA Frequency-domain Approach to Subspace Identification of Nonlinear Systems, Application to Aerospace Structures
Noël, Jean-Philippe ULg

Doctoral thesis (2014)

The construction of mathematical models from experimental data is an essential step in the design process of engineering systems. The different tasks involved in this activity, from the measurement and ... [more ▼]

The construction of mathematical models from experimental data is an essential step in the design process of engineering systems. The different tasks involved in this activity, from the measurement and processing of data to the validation of the model, fall into the general field of system identification. In structural dynamics, the theoretical and experimental aspects of linear system identification have been successfully addressed since the early seventies, and mature analytical, computational and testing tools have emerged. Nonlinear system identification of vibrating structures has also enjoyed significant advances during the past few years. However, the common practice in industry is to ignore nonlinearities, arguably because their analysis is still regarded as impractical. The objective of this doctoral thesis is precisely to progress towards the development of a practical system identification methodology dedicated to real-life nonlinear structures. The first facet of the thesis is to introduce a nonlinear generalisation in the frequency domain of the so-called subspace identification methods. The proposed frequency-domain nonlinear subspace identification (FNSI) approach yields accurate models of large-scale systems comprising strong nonlinearities, closely-spaced modes and high damping. Because it can also estimate a large number of parameters while maintaining an acceptable computational burden, the second facet of this research is to investigate the utilisation of cubic splines as a very flexible means to model complex nonlinearities. Finally, the third facet of the present work is to derive nonlinear models with optimal statistical properties in the presence of measurement noise. This is achieved by embedding the FNSI method into the maximum likelihood identification framework. The scope of the identification and modelling tools developed in this thesis encompasses nonlinear structural systems originating from the various areas of vibration engineering, including the aerospace, mechanical or civil fields, amongst others. Throughout the dissertation, these tools are illustrated using numerical and experimental structures of increasing complexity, mainly related to aerospace applications. [less ▲]

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See detailIncertitudes liées à la modélisation agro-environnementale en vue de développer des outils d'aide à la décision
Dumont, Benjamin ULg

Doctoral thesis (2014)

The European Nitrates Directive 91/6/76/EEC aims to ensure water quality by preventing pollution of surface and groundwater induced by nitrates originating from agricultural sources and by promoting ... [more ▼]

The European Nitrates Directive 91/6/76/EEC aims to ensure water quality by preventing pollution of surface and groundwater induced by nitrates originating from agricultural sources and by promoting agronomical good practices. While the implementation of this Directive seems effective, it appears however that the use of nitrogen has still increased by 6% over the last four years in 27 European countries. Furthermore, agricultural sources would be still at the origin of 50% of the total amount of nitrogen discharged into surface waters (http://ec.europa.eu/environment/water/water-nitrates/index_en.html). In Wallonia (Belgium), the Nitrates Directive has been transposed under the Sustainable Nitrogen Management in Agriculture Program (PGDA). Launched in 2002, it involves different sets of actions, like rules definitions concerning fertilizers application, specific and appropriate crop management in vulnerable areas, the control of potentially leachable nitrogen (APL) levels in soils, etc. This is the global context in which lies the present thesis. The main aim is to optimise the nitrogen fertiliser practices to ensure that the needs of a winter wheat culture (Triticum aestivum L.) could be met while reducing the environmental pressure. It relies on the use of crop models, which describe the growth and the development of a culture interacting with its environment, namely the soil and the atmosphere. The major difficulty while working with crop models and model-based decision support tools lies in the fact that different sources of uncertainties have an impact on the modelled phenomena. Indeed, crop models are constituted by a consequent number of differential non-linear equations, involving a lot of parameters which need to be determined as accurately as possible in order to match as close as possible observed sequences of measurements. The first source of uncertainty is thus constituted by the parameters definition. Once the model has been correctly and robustly calibrated it can be used to perform predictions. However, in an agronomical context, the time-delay between sowing and harvest is consequent. As the end-season yield is often the expected output, the uncertainty linked to the non-knowledge of the future implies for the modeller to refer to different hypothesis concerning upcoming climatic scenarios. Finally, moving from models to decision systems dealing with N management involves a last source of uncertainty. Indeed the main problem is that the impact of a given practice is delayed in time from its realisation. In addition to the uncertainty linked to climatic projections themselves, it is highly important to consider the interactions between the practices and the climate. Furthermore, in a decision-making process, it could be highly relevant to know the uncertainty's estimation that could be tolerated on the decision.. Therefore, the present thesis aims to study these different sources of uncertainty in order to design an efficient decision support system. It is divided into five parts. In the first part, a Bayesian sampling algorithm, known as DREAM (DiffeRential Evolution Adaptative Metropolis) will be presented. It was successfully coupled with the STICS soil-crop model used in this study. The a posteriori probability density function of many parameters was sampled in order to improve the simulations of the growth of a winter wheat culture (Triticum aestivum L.). The DREAM algorithm offers different advantages in comparison to usual methods. Among these, it is possible to study i) the most probable a posteriori parameters distributions, ii) the parameters correlations, and iii) the uncertainties impacted on model outputs. Furthermore, a new version of the likelihood function was proposed, making an explicit use of the coefficient of variation. Results showed that it allowed the noise existing on measurements to be considered, but also the heteroscedasticity phenomenon usually encountered in biological growth processes. In parallel, assimilation data is another way to improve models simulations. These techniques allow considering measurements performed in real-time (e.g. remote measures of LAI or soil water content) in order to correct and adjust the possible drift of model simulations. In particular, a recently developed algorithm, known as variational filter, was evaluated. Its superiority, both in term of state variables simulations improvement and parameter resampling, was demonstrated. The third part of the research focuses on the real-time end season yield prediction. It involves building climate matrix ensembles, combining different time ranges of projected mean data and real measured weather originating from the historical records. As the crop growing season progresses, the effects of real monitored data plays a greater role and the prediction reliability increases. Our results demonstrated that a reliable predictive delay of 3-4 weeks before harvest could be obtained. Finally, using real-time data acquired with a micrometeorological station enabled to (i) predict, daily, potential yield at the local level, (ii) detect stress occurrence, and (iii) quantify yield losses (or gains). Being based on projected seasonal norms, this methodology is in opposition to another technique that consists to offer a panel of solution for what concerns the future. Such probabilistic technique relies on the use of stochastic weather generator (LARS-WG in this case). However, in the fourth part of this thesis, on the basis of the convergence in law theorem, it was demonstrated that in 90% of the climatic situations, both approaches were equivalent, exhibiting RRMSE and normalised deviation criteria inferior to 10%. Furthermore the two approaches offered similar predictive delay-time. The main difference between techniques lies in the finality. The first allows to quickly simulate the remaining yield potential, while the second aims to quantify the uncertainty level associated to the predictions. In the fifth and last part of this thesis, in order to quantify the uncertainty level associated to different modalities of N applications, the STICS model answers were studied under stochastic climatic realisations. It was demonstrated that, if no N was applied, under our temperate climatic conditions, the yield distribution could be considered as normal. However, with increasing N practices, the asymmetry level was found itself increasing. As soon as N was applied, not only were the yields higher, but also was the probability to achieve yields that were at least superior to the mean of the distribution. This undoubtedly reduced the risk for the farmer to achieve low yields levels. To summary all the researches conducted in this thesis, a N strategic decision support system was developed. In a general way, for what concerns the Hesbaye Region, the superiority of three fractions N protocols was demonstrated. In addition, the three rates fertilisation management based on the systematic applications of 60 kgN.ha-1 at tillering and stem extension stages and offering the possibility to adapt the flag-leaf fraction in real-time appeared as an optimal strategy. Within this tool, the uncertainty associated to climatic variability could be finely characterised, and the risk encountered by the farmer was quantified for different investigated practices. But far more important, it was demonstrated that N management could be optimised in real-time. In a general way, the research should be pursued by studying more fundamentally and systematically a wide range of different agro-environmental situations. In particular, it would be interesting to study of the Genotype × Environment × Cultural practices interactions to ensure food security in a climatic changing world. [less ▲]

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See detailEtude du mécanisme d’activation du zymogène proDer p 6 de l’acarien Dermatophagoides pteronyssinus et du rôle de son propeptide dans l’inhibition, le repliement et l’immunogénicité de l’allergène
Herman, Julie ULg

Doctoral thesis (2014)

L’allergie aux acariens touche 20 à 30% de la population occidentale. L’allergène Der p 6 de l’acarien Dermatophagoides pteronyssinus est une protéase à sérine active de la famille de la chymotrypsine ... [more ▼]

L’allergie aux acariens touche 20 à 30% de la population occidentale. L’allergène Der p 6 de l’acarien Dermatophagoides pteronyssinus est une protéase à sérine active de la famille de la chymotrypsine. Son activité protéase pourrait être impliquée dans l’augmentation de la réponse allergique chez les patients atopiques. Der p 6 est synthétisée chez l’acarien sous la forme d’une pré-pro-protéine constituée d’un peptide signal (17 résidus) et d’un zymogène présentant un propeptide de 34 résidus en amont du domaine protéase de 231 résidus. Après avoir produit en Pichia pastoris et purifié le zymogène proDer p 6, son mécanisme d’activation a été élucidé dans la première partie de ce travail. Il s’agit d’un mécanisme tout à fait particulier, propre à l’acarien lors duquel la protéase à cystéine active Der p 1 mature proDer p 6. Un mécanisme similaire avait pu être montré pour le trypsinogène proDer p 3. Pour la première fois, la forme recombinante de Der p 6 a pu être produite. Celle-ci présente la même activité que la protéase naturelle présente dans les extraits d’acariens. Dans la seconde partie de ce travail, Der p 6 ainsi que Der p 1 ont pu être mis en évidence au niveau du tube digestif de l’acarien D. pteronyssinus, ce qui confirme que ces protéases sont impliquées dans la digestion de l’acarien. La protéase Der p 1 est présente au niveau de l’intestin moyen, tandis que Der p 6 est présente dans le gros intestin. Dans cette dernière partie de l’intestin, les protéases sont co-localisées, ce qui indique que le procédé de maturation observé in vitro pourrait se dérouler in vivo. Dans la troisième partie de ce travail, nous avons montré que le propeptide de proDer p 6 est un inhibiteur spécifique de la protéase Der p 6. Le propeptide est donc impliqué dans le contrôle spatio-temporel de l’activation de la protéase. Lors de ce processus, les quatre résidus en amont du site de clivage (résidus P4 à P1) sont nécessaires et suffisants pour la reconnaissance et le clivage du propeptide par Der p 1. Comme cela a été montré pour Der p 3, aucun rôle du propeptide dans le repliement de la protéase Der p 6 n’a pu être mis en évidence. Dans la dernière partie, une étude préliminaire de l’allergénicité de Der p 6 a été réalisée. Der p 6 serait un allergène mineur avec une prévalence d’environ 30 %. Les études par ELISA et activation des basophiles, réalisées avec les formes naturelles, recombinantes ou inactives de Der p 6 indiquent que ces différentes formes pourraient être utilisées en diagnostic. Des prédictions bioinformatiques ont également été réalisées afin de déterminer les épitopes B de Der p 6. [less ▲]

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See detailChimie Intégrative dédiée aux morphosynthèses de matériaux composites multi-échelles et étude de leurs applications en photoluminescence, photocatalyse et photovoltaïque
Kinadjian, Natacha ULg

Doctoral thesis (2014)

The shaping of functional materials and the control of their texture at all length scales are sine qua non conditions for the improvement of current systems. This PhD project consists in creating complex ... [more ▼]

The shaping of functional materials and the control of their texture at all length scales are sine qua non conditions for the improvement of current systems. This PhD project consists in creating complex solid architectures using interdisciplinary methods such as sol-gel chemistry or complex fluids physics. Therefore, it is possible to synthesize Titanium Dioxide macroscopic fibers or films which possess a hierarchical porosity. This organization allows the optimization of the matter transport (liquid/gaz) for air depollution application (photocatalysis) or dye-sensitized solar cells. In another project, we were able to control the alignment of zinc oxide nanorods within a macroscopic fiber. This alignment provides to the fiber an anisotropic photoluminescence behavior which can be useful for switching devices application. Finally, we synthesized anisotropic particles and nano-sheets of polypyrrole (conducting polymer) in order to obtain smooth thin films presenting interesting electrical properties. The objective was to use them as electrolyte and/or electrode in dye-sensitized solar cells. [less ▲]

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See detailL'ordinaire du contentieux administratif : Analyse du processus décisionnel au Conseil d'Etat belge francophone
Colemans, Julie ULg

Doctoral thesis (2014)

La thèse porte sur le processus décisionnel au Conseil d’Etat belge. Le raisonnement juridique pratique a été étudié à travers les activités concrètes que les auditeurs et conseillers accomplissent tout ... [more ▼]

La thèse porte sur le processus décisionnel au Conseil d’Etat belge. Le raisonnement juridique pratique a été étudié à travers les activités concrètes que les auditeurs et conseillers accomplissent tout au long du parcours du dossier. De cette manière, le raisonnement juridique n’est pas appréhendé comme une opération logique de la pensée mais comme un accomplissement pratique qui se déploient dans un horizon de sens partagé incarné par le concept de « raisonnable ». [less ▲]

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See detailDynamique et composition des atmosphères supérieures de Mars et Vénus observées par les spectrographes ultraviolets à bord de Mars Express et Vénus Express
Stiepen, Arnaud ULg

Doctoral thesis (2014)

Venus has a dense CO2-dominated atmosphere. Above 50 km, the atmospheric circulation is composed of two dominants patterns: the Retrograde Superrotating Zonal (RSZ) circulation up to 65 km and the ... [more ▼]

Venus has a dense CO2-dominated atmosphere. Above 50 km, the atmospheric circulation is composed of two dominants patterns: the Retrograde Superrotating Zonal (RSZ) circulation up to 65 km and the subsolar to antisolar (SSAS) circulation beyond 120 km. The SSAS is caused by the temperature gradient between the day and the night hemispheres and it generates a global flow from the dayside to the nightside. Between 65 and 120 km, the circulation is complex as it is the superposition of the two main components. I have used the nightglow emitted by the NO* molecule (180-300 nm) produced by recombination of N(4S) and O(3P) atoms. These atoms are created by photodissociation of N2 and CO2 molecules on the dayside and carried to the nightside by the SSAS circulation. I analyze the full set of measurements of the NO δ and γ bands measured by the SPICAV instrument on board the ESA Venus Express spacecraft. I discuss the altitude and brightness of the emission peak (60 kR at 115 km) and show that the emission profile exhibits a secondary peak in ~10% of the cases. This additional peak is probably caused by upward-moving gravity waves propagating from below. I have developed an inversion method of the observed limb profiles to compare the results with a chemical-diffusive model of the atmosphere of Venus and constrain the vertical fluxes of N and O. On the basis of an extended statistical analysis, I characterize the presence of a bright spot of the nightglow of NO shifted from the antisolar point and located around 0230LT, 10°S. I use the vast SPICAV airglow database to statistically demonstrate that the NO nightglow is highly variable, both temporally and spatially. Mars experiences seasons as its rotation axis is inclined from its spin axis. Its upper atmospheric dynamics is dominated by summer-to-winter global transport. I study the upper atmosphere of Mars using nightglow observations performed by the SPICAM instrument on board ESA’s Mars Express spacecraft. I analyze the δ and γ bands of molecule NO in the nightside mesosphere to confirm, on statistical basis, the peak brightness and altitude of the NO UV emission (5 kR at 72 km). I show that the NO nightglow is located following the relation Latitude = -80xsin(Solar Longitude), in agreement with results based on stellar occultations and from the LMD model, which simulates the photochemistry and dynamics of the Mars atmosphere. I have performed a detailed study of the CO Cameron band (170 to 270 nm) and CO2+ doublet (290 nm) dayglow. I have developed a method to deduce the temperature profile around 150 km, an important study as the distribution of the temperature in the Mars atmosphere is poorly known. I showed that the temperature at high altitude is only weakly correlated with the solar EUV flux. This result suggests that the variability of the upper atmosphere may include internal processes. Comparisons with the Mars Global Ionosphere Thermosphere Model show that the model can reproduce the observation for high solar conditions but predicts lower temperature for low to moderate solar conditions. Further study will therefore be necessary to identify and understand the mechanisms that govern the temperature variability. [less ▲]

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See detailModélisation 2D par éléments finis du contact : effet de l’utilisation de méthodes de représentation des surfaces présentant un ordre de continuité élevé et méthodes permettant de passer le patch test
Nguyen, Duc Tue ULg

Doctoral thesis (2014)

Ce travail de thèse concerne la mécanique numérique du contact entre les solides déformables. La simulation numérique des problèmes de contact comporte de nombreuses difficultés notamment dans un contexte ... [more ▼]

Ce travail de thèse concerne la mécanique numérique du contact entre les solides déformables. La simulation numérique des problèmes de contact comporte de nombreuses difficultés notamment dans un contexte de grands déplacements et de grandes déformations. Le but de ce travail est d’analyser l’influence de l’ordre de continuité élevé de la représentation de surface et de développer une méthode pour passer le patch test, à savoir qu’un élément passe le patch test si il transmet correctement des pressions de contact entre deux surfaces. Pour la discrétisation des éléments finis, l'interface de contact est représentée par une série de lignes et de courbes à continuité C0. Par conséquent, lors du passage du nœud esclave entre deux segments maîtres adjacents, il peut arriver avoir une discontinuité de la direction du vecteur normal. Cette situation peut mener à des problèmes de convergence de l'algorithme de résolution. Pour éviter ce problème, l’approche proposée consiste à développer les représentations de surface maître à ordre de continuité C1 ou C2 pour les éléments nœud-surface linéaires et quadratiques. Les éléments nœud-surface ne passent pas le patch test. Plus récemment, un élément linéaire utilisant la méthode des nœuds esclaves virtuels pour Passer le Patch Test (PPT) a été proposée dans la littérature. Cependant, cet élément est à ordre de continuité C0 et peut donner des grandes oscillations de la pression de contact à cause des pénétrations initiales des nœuds esclaves virtuels qui sont les pénétrations des nœuds esclaves virtuels dans la surface maître à l’état initial. Pour tenter de surmonter cette difficulté, une nouvelle approche repose sur un élément linéaire utilisant la méthode PPT et la représentation de surface à ordre de continuité C1 pour la surface maître et pour la surface esclave. L’élément quadratique nœud-surface donne des oscillations de pression de contact à cause de la distribution non-uniforme des forces nodales. Afin de résoudre ce problème, la méthode PPT est développée pour l’élément quadratique. [less ▲]

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See detailTheoretical studies of gravitational lensing phenomena: the case of multiply imaged quasars
Wertz, Olivier ULg

Doctoral thesis (2014)

In the early 1960s, gravitational lensing has received a special attention when S. Liebes and S. Refsdal have derived in detail some of the basic equations of the theory. While Liebes (1964) discussed the ... [more ▼]

In the early 1960s, gravitational lensing has received a special attention when S. Liebes and S. Refsdal have derived in detail some of the basic equations of the theory. While Liebes (1964) discussed the probability of detecting these effects and considered several astrophysical applications, Refsdal (1964) derived, inter alia, his famous relation which links the Hubble parameter (H0) to the expected time delays between pairs of lensed images. From that moment, the scientific community fully realized that gravitational lensing effects offer a new way of probing cosmology. However, an important fact has been to accept that the determination of H0 seems to be model dependent, not only on the universe model, but also on the mass distribution of the deflector. The main topic of the present thesis constitutes a straight continuation of this inquiry. We have been sounding parts of the mathematical lensing framework on two fronts. First, considering to first order a very small misalignment between the source, the lens and the observer, we have derived the expressions of the lensed image positions along with their amplification ratios, for the case of power-law axially symmetric mass distributions, the so-called ε-γ family of models (Wertz, Pelgrims & Surdej, 2012). After combining these results, it has allowed us to derive an expression for H0 independently of the model parameters. We have extended this study to the ε-γ family of models with external shear, as well as to the singular isothermal ellipsoid (SIE) models. For both these types of models, we have obtained an expression of H0 which is once again independent, to first order, of the model parameters. Furthermore, even though these families of models remain rigorously distinct, except for the singular isothermal sphere (SIS) and the perfect alignment, the expression of H0 in terms of observable quantities and of the source position takes surprisingly the same simple form. In addition, we have demonstrated the feasibility of analytically constraining to first order the model parameters by only using the astrometric positions of the lensed images. Therefore, for the case of a small misalignment between the source, the deflector and the observer, it is straightforward to determine whether the ε-γ or SIE family of models constitutes a judicious representation of the mass distribution of the deflector. It is conceivable that similar results can be deduced for other families of models. Secondly, we have developed a new analytical approach in order to determine the expression of the deflection angle, hereafter α. Since the latter depends on the deflector mass distribution, there exists no global explicit expression but only an implicit definition of α. Therefore, the analytical methods used to obtain the explicit expression differ for different types of mass distribution. However, using the Fourier transform theory, one may basically express α in terms of the Fourier transform of the surface mass density. Such a method allows us to approach any mass distribution in a unique way. As a first application, we have separately derived the expression of the two components of α for the case of homoeoidal symmetric lenses (Wertz & Surdej, 2013). This original result constitutes a first proof that the Fourier approach constitutes a promising alternative to the complex formalism introduced by Bourassa & Kantowski (1975, corrected by Bray 1984). A particular case of homoeoidal symmetric lenses lies in the non-singular isothermal ellipsoid (NSIE) family of models for which the analytical treatment has been somewhat limited (Kormann & al. 1994). The use of the Fourier approach has made possible to derive a complete analytical treatment of the NSIE, i.e. the expressions of the deflection angle, the deflection potential, and the critical and caustic curves even off the axis (Wertz & Surdej, submitted to MNRAS in february 2014). This original result has allowed us to investigate and better understand this family of models. Furthermore, it is of great interest for mass distribution modeling and to rigorously determine the expected time delays between pairs of lensed images. The previous analytical treatments mainly consisted of parametrical models for the deflector. An alternative way to grasp lenses consists in modeling their mass distribution using non-parametric models. With this aim in mind, we have proceeded as follows: we tessellate the lens plane with squared pixels, and associate to each of them a constant surface mass density. Making use of the Fourier approach, we have derived the expression of the deflection angle for the whole grid. This result contains the main advantage of the non-parametric models, i.e. to model any type of mass distribution without any preconception, and the usefulness of handling quantities which can be described with analytical functions. [less ▲]

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See detailIntegration of near-surface geophysical, geological and hydrogeological data with multiple-point geostatistics in alluvial aquifers
Hermans, Thomas ULg

Doctoral thesis (2014)

Alluvial plains constitute essential geological bodies for environmental studies such as contaminated sites remediation, low-enthalpy geothermal energy or groundwater resources. The heterogeneity of these ... [more ▼]

Alluvial plains constitute essential geological bodies for environmental studies such as contaminated sites remediation, low-enthalpy geothermal energy or groundwater resources. The heterogeneity of these deposits governs flow processes and needs to be quantified. A proper description of such complex deposits requires an integrated approach combining geological, geophysical and hydrogeological data. Solving such spatial inverse problems in the Earth Sciences remains a considerable challenge given the large number of parameters to invert for, the non-linearity of forward models and, as a result, the ill-posedness of the problem. Geostatistics is therefore needed to specify prior models, more particularly, information to control the spatial features of the inverse solutions. Two-point geostatistical approaches have been developed to describe the heterogeneity of one geological formation but fail to reproduce the heterogeneity of fluvial deposits with multiple facies. Multiple-point statistics (MPS) introduced the training image (TI) concept to replace the variogram within an extended sequential simulation framework. The use of geophysics to constrain such simulations has been studied in the petroleum industry with wave-based methods (seismic reflection), but little research has been done to assess the use of near-surface potential methods to condition MPS in environmental studies. In this work, we propose to integrate geological (borehole logs), geophysical (electrical resistivity tomography (ERT) profiles) and hydrogeological (hydraulic heads) data within MPS models on the alluvial plain of the Meuse River, Belgium. Potential-based geophysical methods being integrative, they suffer from a relatively poor resolution. We first study how we can improve the informative content of geophysical inversion by including prior information in the ERT inverse problem. Three methods are tested and compared in several field cases, namely the reference model inversion, the structural inversion and the regularized geostatistical inversion. If every method has advantages and drawbacks, the best suited method for the considered problem is the regularized geostatistical method. Electromagnetic borehole logs enable to derive the vertical correlation length of electrical resistivity in the deposits and to subsequently use it to constrain the inversion. In addition to the knowledge of the bedrock position, it enables to retrieve an electrical resistivity distribution of the deposits close to direct observations. This ensures that geophysical models will be informative to constrain MPS simulations. Given the lack of geological and sedimentological data to build accurate TIs, a data base of TIs is built using several different parameters and scenarios. They are all based on a three facies description: clay/loam, sand and gravel corresponding to low, intermediate and high hydraulic conductivity. Then, we develop a methodology to verify the consistency of independently-built TIs with geophysical data. Our methodology starts by creating subsurface models with each TI. From these models we create synthetic geophysical data and from this synthetic data, synthetic inverted models. These models are now compared with a single inverted model obtained from the field survey, allowing for our definition of what is ``consistent''. To that extent, we calculate the Euclidean distance between any two inverted models as well as field data and visualize the results in a 2D or 3D space using multidimensional scaling (MDS). With this technique, it is possible to verify if field cases fall in the distribution represented by synthetic cases, and thus are consistent with them. In a second step, we present a cluster analysis on the MDS-map to highlight which parameters are the most sensitive for the construction of TI. Based on this analysis, a probability of each geological scenario is computed through kernel smoothing of the densities in reduced projected metric space. The integration of hydrogeological data is made through a stochastic inversion method: the probability perturbation method (PPM), using MPS constrained with geophysical data to generate models. The PPM algorithm automatically seeks solutions fitting both hydrogeological data and training-image based geostatistical constraints. Only geometrical features of the model are affected by the perturbation, i.e. we do not attempt to directly find the optimal value of hydrogeological parameters (chosen a priori), but the optimal spatial distribution of facies whose prior distribution is quantified in a training image. Tracing experiments may be used to further constrain hydrogeological models. ERT has proven its ability to monitor salt tracer tests, but few studies have investigated its performances in thermal tracing experiments. In this study, we demonstrate the ability of surface and crosshole ERT to image quantitatively temperature changes during heat injection experiments. Such resistivity data provides important information to improve hydrogeological models. Our study proves that ERT, especially crosshole ERT, is a reliable tool to follow thermal tracing experiments. It also confirms that ERT should be included to in situ techniques to characterize heat transfer in the subsurface and to monitor geothermal resources exploitation. [less ▲]

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See detailUtilisation de biocapteurs microbiens GFP pour la caractérisation des performances des bioréacteurs
Brognaux, Alison ULg

Doctoral thesis (2014)

The scale-up of bioprocesses is a critical step during bioproducts development. Actually, the mixing operation’s efficiency drops when the reactor volume increases: gradients of glucose and oxygen appear ... [more ▼]

The scale-up of bioprocesses is a critical step during bioproducts development. Actually, the mixing operation’s efficiency drops when the reactor volume increases: gradients of glucose and oxygen appear when operating in fed-batch mode, causing losses of production. The aim of this project is the scale-up and sizing of bioreactors based on the direct physiological parameters to consider this heterogeneity. Concretely, it consists in obtaining an on-line signal of the physiological status of micro-organisms. The coding sequence of the Green Fluorescent Protein (GFP) has been inserted after gene promoters of interest in Escherichia coli to built biosensors. A particular focus has been paid on promoters responding to general stress or specifically to lack of glucose and on those responding to cell growth rate. The GFP biosensors of interest have been tested in scale-down bioreactors, allowing to reproduce industrial hydrodynamic conditions at a laboratory scale. A mini-bioreactor platform has also been developed to enable a high throughput screening of biosensors. The intracellular accumulation of GFP has been measured by flow cytometry and GFP release has been monitored by western blot analyses. For biosensors sensitive to stress general response or glucose limitation, GFP has been induced during a glucose limitation and repressed by comparison when glucose heterogeneities appear. The use of a destabilized GFP has been considered in this project for ribosomal biosensors to approach more instantaneous physiological responses of microorganisms. For these ones, the response is proportional to growth rate during the batch phase, but more complex mechanisms take part during a prolonged glucose limitation. Membrane permeability has also been studied and has been noticed more important in homogeneous fed-batch bioreactors than in scale-down reactors. As GFP leakage has been noted in the extracellular medium, a study has also been carry out about proteins released in the extracellular medium (leakage), and correlated with the cell permeability. Finally, an on-line flow cytometer has been developed for the characterization of physiological status of micro-organisms during the bioprocess, and a 3D-ORM probe allowed to measure their viability on-line [less ▲]

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See detailDétermination de la broyabilité des plaquettes et des pellets de bois
Temmerman, Michaël ULg

Doctoral thesis (2014)

The literature about energy requirements for product milling in mining industry shows the subject has been, and still is, considered by numerous authors. Several milling theories have been proposed for ... [more ▼]

The literature about energy requirements for product milling in mining industry shows the subject has been, and still is, considered by numerous authors. Several milling theories have been proposed for these industries, especially concerning ores milling. Biomass milling, prior to its use as biofuel, has been, by far, less studied. Nevertheless, few measurements are available about energy needed for milling of particular biomass, in particular systems. But studies taking into account enough characteristic of the milled material (origin, moisture content, particle size distribution) are scarce. Moreover, the methods used to measure these properties are generally different. In consequence, nearly none biomass milling model has been proposed. Concerning wood densified product (pellets & briquettes) apparently no data are available yet. . This study draws upon the milling theories developed for the ore processing industry (Von Rittinger, Kick and Bond theories which have been merged by Charles and Hukki) in order to define a method for characterizing wood chip and pellet energy consumption during milling. Thus it proposes parameters and measurement methods that have to be taken into account when milling modelling comes to an end for biomass or densified biomass Energy consumption during wood milling depends on three main factors: the material moisture content, the particle size difference between the feed and the milled product, and the material itself. The latter may be characterized by a single grindability parameter based on an adaptation of Von Rittinger’s constant. A relation characterizing wood pellet energy consumption as a function of the particle size distribution of the pellet ingredients and the milled pellets is proposed as well. This is characteristic of each type of pellet for each moisture content value considered [less ▲]

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See detailL’antonymie. Définition de l’antonymie en langue et description des fonctions sémantico-référentielles de la co-présence antonymique en discours
Steffens, Marie ULg

Doctoral thesis (2014)

Grâce à un examen critique des travaux consacrés à l’antonymie, nous avons pu définir l’antonymie comme une relation multiforme qui touche des unités très différentes sur les plans sémantique et morpho ... [more ▼]

Grâce à un examen critique des travaux consacrés à l’antonymie, nous avons pu définir l’antonymie comme une relation multiforme qui touche des unités très différentes sur les plans sémantique et morpho-syntaxique mais dont l’unicité réside dans une opposition binaire fondamentale enracinée lexicalement. Nous avons ainsi dépassé la simple distinction entre contraires et contradictoires pour entrer dans la fascinante diversité de l’opposition et montrer comme les notions de graduation, de graduabilité, de scalarité, de borne et de seuil se combinent pour forger l’identité sémantique de chaque paire d’antonymes, la rapprocher ou la distinguer des autres. Grâce à l’analyse empirique d’énoncés extraits du journal Le Monde, nous avons montré que la co-présence antonymique en contexte s’appuie pour faire sens sur les relations antonymiques inscrites dans la mémoire linguistique des locuteurs, où sont fortement associées la forme et le sens des antonymes. Nous avons également montré comment la plongée de deux antonymes dans un contexte d’emploi peut moduler leur opposition et la définition du lexème neutre ou intermédiaire, lorsqu’il existe. Les antonymes co-présents, grâce aux rôles sémantico-syntaxiques qu’ils peuvent jouer, contribuent à la structuration des énoncés dans lesquels ils sont employés parce qu’ils organisent les unités qui les entourent sur le plan sémantico-référentiel. [less ▲]

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See detailWhen Firms Cross-List, do Investors care?
Mouchette, Xavier ULg

Doctoral thesis (2014)

Over the past three decades, financial markets have experienced a tremendous increase in global linkages. Cross-Listing is one prominent example of these trends. By cross-listing firms can proactively ... [more ▼]

Over the past three decades, financial markets have experienced a tremendous increase in global linkages. Cross-Listing is one prominent example of these trends. By cross-listing firms can proactively broaden their shareholder basis, overcome limitations of their domestic markets, and link their securities to multiple capital markets at a time. Its far-reaching financial effects are associated with this internationalization of the firm’s capital structure. This thesis focuses on the valuation implications of cross-listing towards major international exchanges. Early attempts to explain these valuation effects called upon international capital market segmentation. This view has since then been highly challenged. Nevertheless, the magnitude of segmentation and its relationship with cross-listing has received much less attention. Our empirical investigations first establish that firms that are about-to-cross-list are not entirely integrated with global capital markets. Furthermore, previous cross-listings which originate from the same home country and country funds both have significant importance to assess the degree of this integration. We next disentangle between the validity of segmentation and informational improvement arguments in explaining the magnitude of cross-listing price effects. Our results suggest that firms that cross-list towards the US markets obtain benefits through the resolution of informational barriers only, while firms from emerging markets derive benefits as a function of their pre-cross-listing segmentation. Crucially, both channels appear conditional on the preceding cross-listing activity. Finally, reactions to cross-listing prove to be not as immediate as assumed by the classical event study literature. Substantial investors' anticipation of the cross-listing decision is demonstrated, as well as the variation regarding the speed and length of the reactions. Size, destination exchange, and the extent to which the firm is integrated into international capital markets appear to be the most influential factors. [less ▲]

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See detailCharacterization of thin layers into concrete with Ground Penetrating Radar
Van der Wielen, Audrey ULg

Doctoral thesis (2014)

The Ground Penetrating Radar (GPR) is a non-destructive method used for roads and buildings inspection: it is well adapted to detect the different layers constituting the structures. The objective of this ... [more ▼]

The Ground Penetrating Radar (GPR) is a non-destructive method used for roads and buildings inspection: it is well adapted to detect the different layers constituting the structures. The objective of this thesis is to develop a method for a fast determination of the properties of a buried layer on the basis of surface GPR measurements. The observation of the GPR waves propagation in numerical simulations led to develop an analytical model, which could be applied to the experimental determination of laboratory layered structures. [less ▲]

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See detailNonlinear Modal Analysis of Conservative and Nonconservative Aerospace Structures
Renson, Ludovic ULg

Doctoral thesis (2014)

The concept of nonlinear normal modes (NNMs) provides a solid and rigorous theoretical framework for the analysis of the nonlinear oscillations of mechanical systems. If NNMs have been studied since more ... [more ▼]

The concept of nonlinear normal modes (NNMs) provides a solid and rigorous theoretical framework for the analysis of the nonlinear oscillations of mechanical systems. If NNMs have been studied since more than fifty years, it is only very recently that contributions dealing with their numerical calculation have been reported in the literature. Although these methods pave the way for the application of NNMs to more complex systems, they have not yet reached the necessary maturity. In this context, the purpose of this research is (i) to further investigate the performance of an existing method for computing the NNMs of conservative systems and (ii) to propose two new methods for the computation of NNMs of nonconservative systems. The first contribution of this thesis is to calculate the NNMs of a real-life aerospace structure, the SmallSat spacecraft developed by EADS Astrium. An algorithm that combines an advanced shooting method with the pseudo-arclength continuation technique is utilized. We show that the NNMs provide a very useful interpretation of the strongly nonlinear dynamics of the spacecraft. One specific contribution is to numerically reproduce with great fidelity several interactions between modes with noncommensurate linear frequencies that were observed experimentally. The second original contribution of this thesis is to develop two new methods for computing the NNMs of damped systems. The first method solves the partial differential equations (PDEs) governing the geometry of the NNM. The PDEs are recognized as hyperbolic, and it is shown that they require appropriate numerical treatments including specific boundary conditions. The proposed method combines a streamline upwind Petrov-Galerkin finite-element formulation with a resolution strategy based on annular domains to grow sequentially the manifold. The algorithm is demonstrated using a wide variety of systems ranging from two-degree-of-freedom to multi-degree-of-freedom nonlinear systems with linear and nonlinear damping. The applicability of the algorithm to complex real-life structures is demonstrated using a full-scale aircraft. The second method presented in this work computes a NNM as a collection of trajectories defined with boundary value problems (BVPs). The method has the distinctive advantage that it does not rely on a parameterization of the NNM. It is demonstrated on two-degree-of-freedom examples featuring linear and nonlinear damping. [less ▲]

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See detailDroit électoral et principe d'égalité. L'élection des assemblées législatives nationales en droit allemand, belge et britannique
Bouhon, Frédéric ULg

Doctoral thesis (2014)

The study concerns the election law and the equality principle in three European legal systems, i.e. the Federal Republic of Germany, the Kingdom of Belgium and the United Kingdom. In this framework, the ... [more ▼]

The study concerns the election law and the equality principle in three European legal systems, i.e. the Federal Republic of Germany, the Kingdom of Belgium and the United Kingdom. In this framework, the research is structured into two principal questions. I firstly wonder whether the election law guarantees equality among the governed people. Should the answer to that question be negative, I secondly check if the inequality can be legally justified in democratic systems. My thesis is a nuanced answer to these questions. The work shows that election law, considered under the scope of the equality principle, includes two categories of legislations which effect is opposed: some legal rules tend to distribute equally the faculty to influence the composition of the elected assemblies, while others tend to distribute unequally that faculty. Among the rules of the second category, I argue that the tendency to inequality can be partly legally justified by the purposes of these rules, but is also a mean – hardly justifiable in a democratic system – that helps persons and parties in government to remain in power. [less ▲]

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See detailSynthèse et étude du composé Li4Ti5O12 comme électrode négative dans les accumulateurs Li-ion
Jamin, Claire ULg

Doctoral thesis (2014)

Electrical energy consumption has increased dramatically and its mode of consumption has diversified over the years, with the development of mobile energy storage devices such as lithium batteries. The ... [more ▼]

Electrical energy consumption has increased dramatically and its mode of consumption has diversified over the years, with the development of mobile energy storage devices such as lithium batteries. The present thesis is dedicated to the synthesis and study of the compound Li4Ti5O12 as negative electrode in Li-ion batteries. The main objective is the development of innovative synthesis techniques based on soft chemistry in order to control and study the effect of structural and microstructural parameters on the electrochemical properties of the compound. Because of its ability to intercalate/deintercalate Li+ ions in its structure without stress-generating volume changes of the structure, Li4Ti5O12 is considered as a so-called "zero-strain" electrode, favouring excellent cycling performance. Therefore, this compound appeared to us a most interesting candidate in this study. The first part of this work investigates a method involving the freeze-drying of a gel precursor followed by self-ignition. Hydroxypropylmethylcellulose is used as an additive and the synthesis of Li4Ti5O12 takes place in four steps : Gelling – Freeze-drying – self-ignition – Calcination. Ammonium nitrate was also added to the reactants to determine the impact on the self-ignition process and the consequences on the structure, microstructure and electrochemical properties of the compound. Indeed, a major issue usually encountered in self-ignition is controlling the amount of heat released, and therefore the temperature during self-ignition. These factors greatly influence the structural and microstructural properties of the compound. The results show that addition of ammonium nitrate leads to an excessive crystal growth which is unfavorable to electrochemical properties of the compound. In the second part of the thesis, the spray-drying method has been investigated using both a lab-scale and a pilot-scale equipment, to take into account possible developments on an industrial scale. For both devices, the influence of concentration on particle morphology was observed. The lab spray-dryer allowed us to obtain a convex to mushroom morphology. For the pilot spray-dryer, the morphologies vary from cauliflower to smooth hollow spheres, and can be further modified by addition of a carbonate source which decomposes during calcination. Depending on the particle morphology and its surface for intercalation of Li+ ions, the electrochemical performances have been improved, sometimes considerably. The drying temperature also affects the performance of the compound through the agglomeration rate of the particles. In conclusion, a wide panel of microstructures has been obtained by investigating two synthesis methods with various sets of experimental conditions. Although all these powders are Li4Ti5O12, there is a significant variation of their electrochemical performance and we have attempted to correlate these with particle morphology. Some prominsing results have been obtained and suggest that performance can be further improved through future work, on both fundamental and applied aspects. [less ▲]

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See detailAcoustic communication in Ophidiiformes: a case study using Ophidion rochei
Kever, Loïc ULg

Doctoral thesis (2014)

A ce jour, la biologie des Ophidiiformes reste peu connue car la majorité des espèces de ce groupe est inféodée aux eaux profondes. Celles qui ne le sont pas ont adopté un mode de vie nocturne, passant la ... [more ▼]

A ce jour, la biologie des Ophidiiformes reste peu connue car la majorité des espèces de ce groupe est inféodée aux eaux profondes. Celles qui ne le sont pas ont adopté un mode de vie nocturne, passant la journée cachées dans le sable, les anfractuosités d’un récif, ou un hôte invertébré en fonction de l’espèce considérée. Des études antérieures ont montré que les appareils de production de sons des Ophidioidei (Ophidiidae et Carapidae) sont complexes et présentent des différences interspécifiques marquées. De plus, l’oreille interne est généralement bien développée. Ces poissons étant actifs dans le noir, la communication acoustique devrait tenir un rôle important dans leur biologie. Ce travail de recherches s’attèle, par différentes approches, à étudier cette thématique en utilisant Ophidion rochei comme cas d’étude. Cet Ophidiidae psammobionte, présente un dimorphisme sexuel marqué au niveau de l’appareil de production de sons avec notamment la présence chez les mâles d’une structure minéralisée à l’avant de la vessie natatoire : le « rocker bone ». Pour mieux cerner la fonction des différentes structures intervenant dans la production et la réception de sons, des comparaisons ont été réalisées avec deux Carapidae : Onuxodon fowleri pour la production de sons et Carapus acus pour la réception de sons. L’étude établit que les espèces O. rochei et C. acus peuvent entendre les sons de leurs conspécifiques. Cependant, l’apport principal de cette partie est la démonstration que la grande taille des otolithes (en valeur absolue ou relative) n’est pas liée à de meilleures capacités auditives. De gros otolithes seraient principalement associés à une plus grande acuité de l’appareil stato-acoustique pour des espèces vivant dans des milieux accidentés. Les mâles et les femelles O. rochei produisent des sons uniquement après le coucher du soleil, durant la période de reproduction qui se déroule de juin à octobre. Ces sons apparaissent courts et tonaux chez les femelles, longs et pulsés chez les mâles. Ces différences dans les signatures acoustiques sont clairement liées au dimorphisme sexuel marqué bien qu’un patron moteur commun soit conservé chez les deux sexes. Brièvement, le muscle sonique dorsal servirait à mettre la vessie natatoire sous tension et le muscle sonique ventral serait à l’origine de l’émission de chaque pulse. De plus, les mâles présentent dans les caractéristiques sonores des différences individuelles marquées qui doivent refléter leur statut reproducteur et/ou leur taille. Chez O. fowleri, les deux sexes possèdent des « rocker bones » de taille et de forme différentes. Les sons enregistrés sont uniquement pulsés, mais ces poissons se distinguent de nombreux téléostéens par leur capacité à moduler le taux de pulsation. La comparaison des morphologies et mécanismes permet de soutenir l’hypothèse selon laquelle les « rocker bones » des deux taxa sont le résultat de convergences évolutives. Chez beaucoup de téléostéens, les sons sont utilisés pour supporter des stimuli d’ordre visuel. Les Ophidioidei étant actifs dans le noir, les contraintes évolutives ont principalement dû se marquer au niveau de l’appareil producteur de sons. En conclusion, la morphologie des appareils de production de sons, le dimorphisme sexuel, les caractéristiques uniques des sons produits, leur moment d’émission dans l’année et dans la journée soulignent la place importante de la communication acoustique au sein des Ophidioidei. [less ▲]

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See detailProduction, transformation artisanale et commercialisation locale des produits alimentaires traditionnels au Vietnam: le cas du vermicelle de tolomane à Hung Yen
Le, Thi Long Vy ULg

Doctoral thesis (2014)

In Vietnam, the vermicelli of Canna edulis Ker Gawl. (C. indica L.) is an artisanal and traditional product, regularly consumed in the festive occasions. From Canna edulis Ker Gawl cultivation to trading ... [more ▼]

In Vietnam, the vermicelli of Canna edulis Ker Gawl. (C. indica L.) is an artisanal and traditional product, regularly consumed in the festive occasions. From Canna edulis Ker Gawl cultivation to trading of vermicelli of Canna edulis at the local level, the vermicelli commodity chain belongs to peasant economy with many actors involved. This research aims at a better understanding of how the actors of vermicelli commodity chain adapt to current socio-economic and environmental conditions of the villages which belong to two communes (Tu Dan and Yen Phu) located in Hung Yen Province. The surveys among 90 farmers and discussions with a group of producers who cultivate the canna and practice flour processing, and a group of vermicelli processors have been carried out from 2010 to 2012. According to our research results, vermicelli commodity chain has created a considerable additional quantity of jobs for local people within the villages of vermicelli processing and the neighboring ones. Thanks to these activities, the rural households income and production investment have been increased. Net income estimated per hectare of canna is about 22.2 million VND (about 822 €), and nearly 4.5 million VND (167 €) per ton of flour produced, and up to 1.7 million VND per ton of vermicelli product (about 63 €). In addition, these activities allow to diversify the sources of family incomes in the countryside. These activities also contribute to stabilize and increase the living standard of farmers (in 2010, the net family income (NFI) due to canna production accounted for 8% to 34 % of farming income; the NFI of vermicelli processing represented between 35% and 86 % of total processing family income). The value-added generated from this vermicelli commodity chain is important, up to 186 million VND (about 7,900 €) per hectare of canna, in which 38 % for flour processing; 20% for vermicelli processing and 20 % for canna cultivators. Thus, the vermicelli commodity chain contributes to meet a specific demand for traditional food in Vietnam. This chain contributes to the rural economy of traditional villages through improving the sources of familial income. However, it is necessary to increase the product quality and to improve the vertical and horizontal linkages between the actors in order to guarantee the sustainable development of this vermicelli chain. [less ▲]

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See detailMénages ruraux et lutte contre la pauvreté : cas des communes de Tu Ly et de Xuang Phong dans la province de Hao Binh Viet Nam
Mai, Lan Phuong ULg

Doctoral thesis (2014)

Since 1998, Viet Nam developed many poverty reduction strategies with the assistance of the WB and the IMF. However, although the national rate of poverty decreased in absolute terms, it does not reflect ... [more ▼]

Since 1998, Viet Nam developed many poverty reduction strategies with the assistance of the WB and the IMF. However, although the national rate of poverty decreased in absolute terms, it does not reflect a real reduction in poverty and does not take into account the nature of poverty. Income and opportunities inequality increased between urban and rural areas, between different social classes and between the Kinh (majority group in Viet Nam) and ethnic minorities. Poverty of ethnic minorities has become an ongoing challenge. In 2010, there were 66.3% of the poor among ethnic minorities against only 12.9% for the Kinh population. This thesis illustrates a reflection on the issue of poverty in Viet Nam and in particular mountainous northern regions where the poverty rate is the highest, reaching 39.4 % in 2012. The historical approach, the capacity approach, the descriptive statistical analysis and case analysis are used to conduct this research. The first difficulty is the identification of poor households and beneficiaries of poverty reduction strategies. Other difficulties are disclosed by the analysis of strategies against poverty: information confusion, budget limitation, insufficient participation of local people in program planning and monitoring, limited autonomy at the local level. Finally it appears that strategies against poverty are not efficient. In addition, land resource privatization, particularly forest resources, limits minority farmers’ ability to cope with unexpected risks Faced with this situation, a possible solution could be to strengthen the role of farmers' associations. Taking into account the ideas and initiatives of local actor, driven by farmers' associations, would have a positive impact on the poverty reduction strategy. Donations and subsidies to individuals should no longer be practiced. In the present threatening world, solidarity among small farmers is necessary to enable them to find their place in the production system and keep the justified profits. In the long run, it is better to give financial support to assist groups and support initiatives by associations of small farmers to facilitate their participation in the market economy while improving their well-being. [less ▲]

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See detailAudiovisual spatial congruence, and applications to 3D sound and stereoscopic video
André, Cédric ULg

Doctoral thesis (2014)

While 3D cinema is becoming increasingly established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D ... [more ▼]

While 3D cinema is becoming increasingly established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D) movie. The perceptual relevance of such spatial audiovisual coherence is of significant interest. In this thesis, we investigate the possibility of adding spatially accurate sound rendering to regular s-3D cinema. Our goal is to provide a perceptually matched sound source at the position of every object producing sound in the visual scene. We examine and contribute to the understanding of the usefulness and the feasibility of this combination. By usefulness, we mean that the technology should positively contribute to the experience, and in particular to the storytelling. In order to carry out experiments proving the usefulness, it is necessary to have an appropriate s-3D movie and its corresponding 3D audio soundtrack. We first present the procedure followed to obtain this joint 3D video and audio content from an existing animated s-3D movie, problems encountered, and some of the solutions employed. Second, as s-3D cinema aims at providing the spectator with a strong impression of being part of the movie (sense of presence), we investigate the impact of the spatial rendering quality of the soundtrack on the reported sense of presence. The short 3D audiovisual content is presented with three different soundtracks. These soundtracks differ by their spatial rendering quality, from stereo (low spatial coherence) to Wave Field Synthesis (WFS, high spatial coherence). The original stereo version serves as a reference. Results show that the sound condition does not impact on the sense of presence of all participants. However, participants can be classified according to three different levels of presence sensitivity with the sound condition impacting only on the highest level (12 out of 33 participants). Within this group, the spatially coherent soundtrack provides a lower reported sense of presence than the other custom soundtrack. The analysis of the participants' heart rate variability (HRV) shows that the frequency-domain parameters correlate to the reported presence scores. By feasibility, we mean that a large portion of the spectators in the audience should benefit from this new technology. In this thesis, we explain why the combination of accurate sound positioning and stereoscopic-3D images can lead to an incongruence between the sound and the image for multiple spectators. Then, we adapt to s-3D viewing a method originally proposed for 2D images in the literature to reduce this error. Finally, a subjective experiment is carried out to prove the efficiency of the method. In this experiment, an angular error between an s-3D video and a spatially accurate sound reproduced through WFS is simulated. The psychometric curve is measured with the method of constant stimuli, and the threshold for bimodal integration is estimated. The impact of the presence of background noise is also investigated. A comparison is made between the case without any background noise and the case with an SNR of 4 dBA. Estimates of the thresholds and the slopes, as well as their confidence intervals, are obtained for each level of background noise. When background noise is present, the point of subjective equality (PSE) is higher (19.4° instead of 18.3°) and the slope is steeper (-0.077 instead of -0.062 per degree). Because of the overlap between the confidence intervals, however, it is not possible to statistically differentiate between the two levels of noise. The implications for the sound reproduction in a cinema theater are discussed. [less ▲]

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See detailLa résilience chez les plus vulnérables au Rwanda
Militery Ngamata, Olivier ULg

Doctoral thesis (2014)

After the tragedy of the genocide against Tutsi in 1994, the Rwandan Government has developed and implemented different programmes and interventions in the sector of social protection in order to reduce ... [more ▼]

After the tragedy of the genocide against Tutsi in 1994, the Rwandan Government has developed and implemented different programmes and interventions in the sector of social protection in order to reduce the poverty of the vulnerable populations and so reach the Millennium Development Goals (MDGs). The different interventions done in the context of social security of the poor people are considered as means of increasing the economy, integrating people in employment market, improving human development thanks to a better access to health and education, and reducing poverty. After the context and justification of the research as well as the methods for data collection, this study focuses primarily on the conceptualization of resilience and connected concepts. Secondly, it scrutinizes the impact of the three programmes of social protection that were developed to reduce poverty of the beneficiaries. The first programme is FARG that supports the survivors of the 1994 genocide against the Tutsi in the domain of education, access to accommodation, medical health and income generating activities. The second programme is Ubudehe-VUP-2020. This one helps very poor households via direct financial transfers, creation of jobs and access to financial services. Girinka is the third programme; it contributes to food improvement, subsistence means and land fertility by supplying a dairy cow to poor families. In third position, this research assesses the achievements of the association of the widows survivors of genocide called - Agahozo (AVEGA) as well as the successes so far reached by the widows beneficiaries. The widows consider AVEGA as an important ‘tutor for resilience’ because it not only deals with their psychological aspects related to the tragedies they experienced but also the promotion and development of economic activities that can supply them with an income for their social reintegration at both economic and social levels. Thus, AVEGA involves a diversity of actors in order to help the widows and implement various income generating activities. Research conducted on the field has targeted, in last position, the most resilient widows. These widows have got support from social protection programmes and AVEGA, in order to involve in income generating activities among which the most developed are agriculture, animal rearing and commerce. All in all, the widows of genocide who were surveyed positively commented the support they get from SPP and AVEGA regarding the reinforcement of their economic resilience. [less ▲]

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See detailEtude des possibilités de culture de Jatropha curcas L. dans la région de Kinshasa en République Démocratique du Congo (RDC)
Minengu Mayulu, Jean de Dieu ULg

Doctoral thesis (2014)

Au cours de ces dernières années, des plantations de Jatropha curcas L. ont été mises en place dans de nombreuses régions d’Afrique subsaharienne pour la production d’agrocarburants sans connaissances ... [more ▼]

Au cours de ces dernières années, des plantations de Jatropha curcas L. ont été mises en place dans de nombreuses régions d’Afrique subsaharienne pour la production d’agrocarburants sans connaissances préalables des conditions de rentabilité et des techniques de production les mieux adaptées aux contextes locaux. L’objectif du présent travail est de lever cette lacune pour la région de Kinshasa en apportant des réponses aux principales questions qui conditionnent la mise au point d’un agrosystème durable basé sur la culture de J. curcas. Pour atteindre cet objectif, les performances d’une plantation pilote installée à proximité de la cité de Mbankana en décembre 2007 ont été évaluées et quatre essais ont été réalisés à partir de juillet 2009 à janvier 2013 dans deux sites représentatifs des conditions du Plateau des Batéké (Mbankana et Mongata) et à proximité de la rivière N’sele dans la banlieue de Kinshasa. Les résultats obtenus montrent que les facteurs de l’environnement et les pratiques culturales ont une influence sur le rendement en graines et en huile de J. curcas. Les faibles rendements obtenus, le coût très élevé des intrants (engrais et insecticides) et les faibles quantités de graines récoltées par journée de travail sont les principales causes de l’absence de rentabilité de la culture pure de J. curcas dans les premières plantations mises en place avec du matériel végétal local subspontané. Les principaux insectes ravageurs de J. curcas dans la zone d’étude sont les grillons Brachytrupes membranaceus Drury (Orthoptera, Grillidae) qui s’attaquent aux jeunes plantes lors de leur mise en place en saison pluvieuse (octobre à décembre), les chenilles mineuses de feuilles Stomphastis thraustica Meyrick (Lepidoptera, Gracillariidae), les chrysomèles Aphthona sp. (Coleoptera, Chrysomelidae) qui consomment le limbe des feuilles et les bourgeons, ainsi que les punaises à bouclier Calidea sp. (Heteroptera, Scutelleridae) qui causent des dégâts aux fleurs et aux capsules. Parmi ceux-ci, la chrysomèle est pour l’instant le ravageur le plus dommageable. En l’absence de traitements insecticides, le niveau des pertes de rendement occasionnées par ces insectes ravageurs atteignent 90% en culture pure sur le Plateau des Batéké. La gravité des dégâts des insectes ravageurs sur J. curcas est plus élevée en culture pure (>60%) que quand il est associé à d’autres cultures annuelles (<45%). La mise au point de méthodes durables de contrôle des ravageurs est une des conditions indispensables à l’installation de plantations de J. curcas dans la région de Kinshasa. L’application de la taille, de la fertilisation minérale et de la couverture du sol avec Stylosanthes guianensis (Aublet) Swartz, permet d’améliorer significativement le rendement en graines de J. curcas Onze écotypes de J. curcas, collectés dans les différentes régions de la RDC et mis en culture au Plateau des Batéké, ont montré des différences significatives en termes du développement végétatif et des rendements en graines et en huile. Le rendement moyen obtenu en 3eme année de production par l’écotype le plus productif (Panu : 473,1±3,6 kg de graines sèches ha-1) était près de 7 fois plus élevé que le rendement de l’écotype qui a produit le moins (Ilebo : 68,6±3,6 kg ha-1). Contrairement à ce qui était annoncé dans la littérature, le temps nécessaire pour l’entrée en pleine production de J. curcas en conditions tropicales humides est supérieur à 5 ans. Il n'est pas possible de déterminer sur base de nos résultats, le niveau exact de rendement qui sera obtenu quand les plantes entreront en pleine production. Quel que soit celui-ci, le coût très élevé de la main d’œuvre nécessaire à la collecte des graines de J. curcas et au désherbage limite fortement les perspectives de rentabilité de la culture pure dans la région de Kinshasa. Dans les zones enclavées du pays, où le coût de la main d’œuvre est moindre et où le prix du diesel est plus élevé, la production de J. curcas peut constituer l’une des solutions pour résoudre les problèmes d’accès à l’énergie. [less ▲]

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See detailDistributed control of electromechanical oscillations in very large-scale electric power systems
Wang, Da ULg

Doctoral thesis (2014)

Electromechanical oscillations threaten the secure operation of power systems and if not controlled efficiently can lead to generator outages, line tripping and even large-scale blackouts. Different ... [more ▼]

Electromechanical oscillations threaten the secure operation of power systems and if not controlled efficiently can lead to generator outages, line tripping and even large-scale blackouts. Different damping devices, like Power System Stabilizers (PSSs), Thyristor Controlled Series Compensators (TCSCs), and so on, are installed to damp these oscillations. This thesis proposes a trajectory-based supplementary control to improve damping effects of existing controllers, which treats damping control as a multi-step optimization control problem with discrete dynamics and costs. At each control time, it collects current system states, solves the optimal control problem and superimposes the calculated supplementary inputs on the outputs of existing damping controllers, in order to enhance the damping. These supplementary signals are continuously updated, which allows to adaptively adjust and coordinate a subset of existing damping controllers, and eventually all of them. Two kinds of methods, Model Predictive Control (MPC) and Reinforcement Learning (RL), are used to embody the proposed supplementary damping control. Firstly, a fully centralized MPC scheme is designed based on a linearized, discrete, complete state space model. Its performances are evaluated both in ideal conditions and considering realistic state estimation errors, and computation and communication delays. The effects of the number and type of available damping controllers are also studied. This scheme is further extended into a distributed scheme with the aim of making it more viable for very large-scale or multi-area systems. Different ways of decoupling and coordinating between subsystems are analyzed. Finally, a robust hierarchical multi-area MPC scheme is proposed, introducing a second layer of MPC based controllers at the level of individual power plants and transmission lines. Secondly, a tree-based batch mode RL algorithm is applied to carry on the proposed supplementary damping control. Using a set of dynamic and reward four-tuples, it constructs an approximation of the optimal $Q$-function over a given temporal horizon. The actions greediest with respect to the $Q$-function are applied as supplementary signals to existing damping controllers. The scheme is firstly tested on a single generator, and then on multiple generators. Different reward signals and damping levels are also considered. Finally, the combined control effects of MPC and RL are investigated. [less ▲]

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See detailAbondance et variabilité des méduses en Baie de Calvi (Corse)
Collignon, Amandine ULg

Doctoral thesis (2014)

L’importance et la variabilité temporelle des méduses calycophores et de la méduse schyphozoaire, Pelagia noctiluca en Baie de Calvi (Corse) ont été étudiées en utilisant une série temporelle planctonique ... [more ▼]

L’importance et la variabilité temporelle des méduses calycophores et de la méduse schyphozoaire, Pelagia noctiluca en Baie de Calvi (Corse) ont été étudiées en utilisant une série temporelle planctonique hebdomadaire de 2003 à 2013. Cette variabilité a été comparée à celles des variables biotiques et abiotiques grâce à la technique du calcul des anomalies saisonnières et interannuelles. La diversité des méduses siphonophores calycophores a été décrite et les critères taxonomiques permettant d’identifier les espèces dominantes (Chelophyes appendiculata, Lensia subtilis, Abylopsis tetragona et Muggiaea atlantica) et de leurs stades de développement ont été précisés. Le cycle de développement de Chelophyes appendiculata a été établi sur base de la variation saisonnière climatique des différents stades moyennée sur les 10 années. Cette espèce est rencontrée toute l’année et présente deux générations, par an. Ce cycle est en phase avec les périodes d’abondance du zooplancton et en particulier des copépodes. Il s’inscrit dans la séquence des événements planctoniques liés à stratification de la colone d’eau. La variation interannuelle se marque par la succession des différentes espèces dont l’abondance augmente sur une période de quatre ans environ. Ainsi au cours des 10 ans, Chelophyes est progressivement remplacé par Lensia. La corrélation entre la moyenne annuelle de l’abondance des eudoxies et celle de la température de surface est très significative et suggère le contrôle de la reproduction par la température. Une relation inverse de l’abondance des stades polygastriques et l’abondance du zooplancton suggère un contrôle de ces méduses sur ce dernier. La distribution spatiale des calycophores a été étudiée au large de la Corse en relation avec les différentes masses d’eau et structures hydrologiques associées au front Liguro-provençal. Les plus fortes abondances sont situées au niveau du plateau continental. Dans 90% des échantillons de surface de fortes abondances de microplastiques étaient associées au zooplancton et aux méduses en particulier. L’étude de la variabilité de la méduse Pelagia noctiluca en Baie de Calvi a confirmé que les invasions obéissent à un cycle pluriannuel indépendamment de la pollution. La distribution en essaims a été étudiée en relation avec les contraintes du milieu. [less ▲]

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See detailComputational homogenization of cellular materials capturing micro-buckling, macro-localization and size effects
Nguyen, Van Dung ULg

Doctoral thesis (2014)

The objective of this thesis is to develop an efficient multi-scale finite element framework to capture the macroscopic localization due to the micro-buckling of cell walls and the size effect phenomena ... [more ▼]

The objective of this thesis is to develop an efficient multi-scale finite element framework to capture the macroscopic localization due to the micro-buckling of cell walls and the size effect phenomena arising in structures made of cellular materials. Under the compression loading, the buckling phenomenon (so--called micro--buckling) of the slender components (cell walls, cell faces) of cellular solids can occur. Even if the tangent operator of the material of which the micro--structure is made, is still elliptic, the presence of the micro--buckling can lead to the loss of ellipticity of the resulting homogenized tangent operator. In that case, localization bands are formed and propagate in the macroscopic structure. Moreover, when considering a cellular structure whose dimensions are close to the cell size, the size effect phenomenon cannot be neglected since deformations are characterized by a strain gradient. On the one hand, a classical multi-scale computational homogenization scheme (so-called first-order scheme) looses accuracy with the apparition of the macroscopic localization or the high strain gradient arising in cellular materials because the underlying assumption of the local action principle, in which the stress state on a macroscopic material point depends only on the strain state at that point, is no--longer suitable. On the other hand, the second-order multi-scale computational homogenization scheme proposed by Kouznetsova exhibits a good ability to capture such phenomena. Thus this second--order scheme is improved in this thesis with the following novelties so that it can be used for cellular materials. First, at the microscopic scale, the periodic boundary condition is used because of its efficiency. As the meshes generated from cellular materials exhibit a large void part on the boundaries and are not conforming in general, the classical enforcement based on the matching nodes cannot be applied. A new method based on the polynomial interpolation without the requirement of the matching mesh condition on opposite boundaries of the representative volume element (RVE) is developed. Next, in order to solve the underlying macroscopic Mindlin strain gradient continuum of this second-order scheme by the displacement-based finite element framework, the presence of high order terms (related to the higher stress and strain) leads to many complications in the numerical treatment. Indeed, the resolution requires the continuities not only of the displacement field but also of its first derivatives. This work uses the discontinuous Galerkin (DG) method to weakly impose these continuities. This proposed second--order DG--based FE2 scheme appears to be easily integrated into conventional parallel finite element codes. Finally, the proposed second-order DG-based FE2 scheme is used to model cellular materials. As the instability phenomena are considered at both scales, the path following technique is adopted to solve both the macroscopic and microscopic problems. The micro--buckling leading to the macroscopic localization and the size effect phenomena can be captured within the proposed framework. [less ▲]

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See detailA framework for using decision-support tools at various spatial scales for the management of irrigated agriculture in semi-arid West-Africa
Wellens, Joost ULg

Doctoral thesis (2014)

The Kou watershed, situated in the Southwestern part of Burkina Faso, has succumbed since a couple of decades to a typical theater play of anarchistic water management. With its 1.800 km², this small ... [more ▼]

The Kou watershed, situated in the Southwestern part of Burkina Faso, has succumbed since a couple of decades to a typical theater play of anarchistic water management. With its 1.800 km², this small watershed includes the second largest city of Burkina Faso (Bobo-Dioulasso), a former state run irrigated rice scheme and several informal agricultural zones. Despite the abundance of water resources, most water users find themselves regularly faced with shortages due to an increase in population and low irrigation efficiencies. Local stakeholders are hence in need of easy to use and low-cost decision support tools for the monitoring and exploitation of the water resources at different spatial and user levels. A top-to-bottom string of adapted water management tools has successfully been installed to tackle the problems: from watershed (top) to field level (bottom), not to mention the 1200 ha irrigation scheme. Land use maps have been derived from satellite and aerial images. Combined with data from a network of hydrologic gauging stations, regional water use maps were established. Hot spots in inefficient water use could be geographically identified and more detailed actions undertaken. Scheme Information Management Information System (SIMIS) was put in place for the management of the regions irrigated rice scheme. A more equitable distribution for the ever diminishing available water resources could be elaborated. A public-private partnership was installed to guarantee its sustainability. Day to day water use on irrigated plots was monitored by soil humidity and crop canopy measurements. A simple field-crop-water balance model AquaCrop was calibrated and validated, and is used by extension workers to draft optimal irrigation charts. Each tool is applied independently, requiring only limited data; but their combined results contribute to an improved integrated water management. [less ▲]

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See detailImplication de la clusterine dans la survie des cellules prostatiques lors de l'apoptose
Ammar, Hayet ULg

Doctoral thesis (2014)

Prostate cancer is the second leading cause of cancer death in men. Although androgen ablation remains the most effective management option, most patients with advanced disease progress to castration ... [more ▼]

Prostate cancer is the second leading cause of cancer death in men. Although androgen ablation remains the most effective management option, most patients with advanced disease progress to castration resistant prostate cancer (CRPC), within two years of treatment. This results, in part, from the increase in the anti-apoptotic molecules expression following androgen withdrawal. Among the proteins involved in this phenomenon, clusterin, also known as testosterone repressed message-2 (TRPM- 2), which exists in two forms: a pro-apoptotic nuclear form (nClU) and a secreted survival factor (sClU). In our study we investigated the role of the secreted form of clusterin in preventing cells from TNFα-induced apoptosis. For this, we first generated a sCLU inducible stable prostatic cancer MLL rat cell line by using the Tet-On gene expression system. With this model we revealed a new mechanism by which sCLU promotes survival in androgenindependent prostate cancer cells, implicating its receptor megalin and the Akt survival pathway. By applying a comparative proteomic analysis in the androgen-independent epithelial cell line MLLTet-sClu induced to overexpress sClu or non induced control-cells, we identified five proteins known to play a role in cancer. These proteins candidates are heat shock proteins Hsp90 and Hsp70, osteopontin (bone sialoprotein, OPN), proliferating cell nuclear antigen (PCNA) and ADP-ribosylation factor 1 (Arf1). Altogether, our data provide new mechanistic insight in sCLU dependent activation of the major survival pathway upregulated in refractory prostate cancer. The identification of the new sCLU protein targets open new avenues for more research to elucidate the significance of clusterin in prostate cancer progression and resistance to therapy. [less ▲]

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See detailL'utilisation de la spectrométrie (NIR) et l’imagerie hyperspectrale (NIR-HIS) proche infrarouge pour étudier la composition chimique et botanique de des fourrages
Dale, Laura-Monica ULg

Doctoral thesis (2014)

Forage quality or nutritive value is related to chemical composition, which can be determinated by laboratory methods. The NIR technique in comparison with classical methods is non-destructive, non ... [more ▼]

Forage quality or nutritive value is related to chemical composition, which can be determinated by laboratory methods. The NIR technique in comparison with classical methods is non-destructive, non-polluting, fast and relatively inexpensive per analysis. Investigations on nutritional quality of Carpathians Apuseni Mountains (Romania) grasslands are rarely performed with NIR technique. Therefore, the objective of the thesis was to develop non-destructive methods for evaluating the quality of feed originating from the Gârda area of the Carpathians Apuseni Mountains (Romania) potentially and to similar grassland arround the world. The first task was to study the potential of NIR spectroscopy for building a spectral database for forage quality based on a large collection of semi-natural grassland samples, using a ‘local’ calibration model built by the Walloon Agricultural Research Centre (CRA-W), in Belgium, to determine various parameters (e.g., protein, dry matter, ash, fibre, fat, aNDFom, ADF, lignin, digestibility, crude energy) from samples collected worldwide, outside Romania. The second task was to develop calibration models for an NIR-HSI system, which involved larger spectral data registration as an image. Until now, analyses to determine plant species were based on botanical composition evaluation, including visual observation, which is a subjective method involving identifying plants directly in the field. Distinguishing samples of pure grassland species can be time consuming, and it was therefore decided to build a spectral database of pure samples and then discriminate these samples into binary and ternary artificial sample mixtures. The main objective of these tasks was to identify the botanical families to which the samples belonged (Poaceae, Fabaceae and Other Botanical Families [OBF]). The focus was not on quantity monitoring, but rather on determining forage quality from stationary experiments in the grasslands. To conclude, this research has shown that it is possible to develop calibration models not only for quality assessment, but also for sample discrimination in dry powder samples. It was intended, that the mathematical models constructed and the database obtained, would be used for future research. [less ▲]

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See detailLa nozione di "partecipazione" nella Glossematica di Louis Hjelmslev
Cigana, Lorenzo ULg

Doctoral thesis (2014)

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See detailStudy of the multi-decadal evolution of the Black Sea hydrodynamics and biogeochemistry using mathematical modelling
Capet, Arthur ULg

Doctoral thesis (2014)

This thesis addresses the biogeochemical cycles in the Black Sea (BS) during the shifting environmental context that affected the BS during the last decades of the 20th century. The study is based on ... [more ▼]

This thesis addresses the biogeochemical cycles in the Black Sea (BS) during the shifting environmental context that affected the BS during the last decades of the 20th century. The study is based on sophisticated data analysis tools and on the development and implementation of a coupled 3D biogeochemical model on the BS domain. The long term variability of the BS hydrodynamical structure was first examined on the basis of in-situ profiles (1950-2012), satellite imagery (1985-2000) and 3D modelling (1960-2000). Profiles of temperature and salinity were used to derive vertical characteristics of the BS structure: the mixed layer depth and the cold content of the Cold Intermediate Layer. To untangle the spatial and temporal trends from this heterogeneous dataset, a general methodology was proposed and embedded in the data analysis software DIVA. The detrended climatologies and long-term time series provided by this approach were used to assess statistical relationships with local atmospheric conditions. Satellite data (sea surface temperature and altimetry) and model results were then analyzed to relate observable surface dynamics to internal hydrodynamic properties. The main multivariate modes of variability of the BS hydrodynamic structure were highlighted on the basis of Empirical Orthogonal Function analysis. Their temporal evolution was explained by the occurrences of specific atmospheric patterns, identified on the basis of neural algorithm analysis and related to the phases of well known teleconnection systems (i.e. the North Atlantic and East Asia/West Russia oscillations). To study the dynamics of eutrophication in the shallow Black Sea NorthWestern Shelf (BS-NWS), a benthic model component was developed that considers the environmental control on diagenetic processes and the bottom shear stress restriction on organic matter deposition. The model accurately reproduced the seasonal and spatial variability depicted by in-situ estimates of benthic nutrients and oxygen fluxes in the BS-NWS. Outputs were used to review the role of the benthic component in BS biogeochemical cycles. The multi-decadal simulations, enabled by the low computational requirements of the benthic-pelagic coupling approach, revealed an inertial component in the dynamics of eutrophication resulting from the accumulation of organic matter during the years of important nutrient loads. This refined resolution of the BS-NWS biogeochemistry allowed us to study the phenomenon of seasonal hypoxia, which is believed to have played a part in the sudden collapse of the fisheries stocks in the late 80s. An index H, combining the spatial and temporal extension of the seasonal hypoxic event, was proposed to quantify the annual intensity of hypoxia as a pressure on benthic communities. We have shown that hypoxia was first triggered in the late 70s by high nitrogen loads, and sustained by sedimentary organic matter accumulation after a rapid reduction of these loads in the 90s. After 2000, warmer summers again led to a increase of the H-index, by entraining hypoxic events of smaller spatial extension but increased duration. A practical relationship distinguishing the impacts of eutrophication and climatic drivers was proposed to assess the effect of their projected values on the future intensity of hypoxia. [less ▲]

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See detailÉtude de l’entomofaune au sein d’associations culturales comprenant le Safoutier (Dacryodes edulis) dans le Haut-Ogooué (Gabon).
Poligui, René Noël ULg

Doctoral thesis (2014)

Le safoutier Dacryodes edulis (Burseraceae) est un important arbre fruitier originaire du Golfe de Guinée. Ses fruits (safou) sont nutritionnels, beaucoup consommés et commercialisés sur les marchés ... [more ▼]

Le safoutier Dacryodes edulis (Burseraceae) est un important arbre fruitier originaire du Golfe de Guinée. Ses fruits (safou) sont nutritionnels, beaucoup consommés et commercialisés sur les marchés urbains d’Afrique centrale et sur les marchés africains d’Europe, générant des revenus substantiels aux producteurs et aux commerçants. Le safoutier est susceptible d’apporter des revenus considérables aux économies des pays d’Afrique centrale. Cependant, malgré cette importance alimentaire et économique, il existe très peu d’études sur le safoutier au Gabon, et ses ravageurs sont peu connus dans toute son aire de culture. La présente étude a donc été entreprise pendant les saisons de floraison et de fructification de cet arbre, d’Août à Décembre 2009 à 2011. Le principal objectif était d’évaluer l’entomofaune fréquentant le safoutier au sein des agroécosystèmes du Gabon. Des techniques complémentaires de surveillances entomologiques ont été utilisées, à savoir les pièges jaunes et les observations visuelles, en zones rurales et urbaines. L’étude révèle l’existence une typologie culturale constituée de jardins de case à dominance fruitière, et des jardins de cultures mixtes. Dans les deux systèmes culturaux, D. edulis est l’arbre fruitier majeur. Les abondances et la diversité entomologique ont été déterminées, et les ravageurs et insectes utiles les plus importants ont été identifiés suivant les associations culturales. L’exploitation des diagrammes de relations trophiques (food webs) a permis de caractériser les liens entre les espèces entomologiques et le type de cultures. Les abondances d’insectes sont plus élevées en milieu rural où D. edulis a une densité plus forte qu’en milieu urbain. La diversité d’insectes est similaire entre les deux milieux. L’intérêt et les caractéristiques phénologiques des ravageurs majeurs ont été décrits, et des mesures de lutte biologique ont été préconisées pour leur contrôle. Les ravageurs prédominants de l’agroécosystème rural sont Oligotrophus sp (Diptera: Cecidomyiidae), Pseudophacopteron serrifer Malenovsky (Phacopteronidae) et Selenothrips rubrocinctus Giard (Thysanopera: Thripidae), tandis que Pseudonoorda edulis Maes & Poligui (Lepidoptera: Crambidae), Bactrocera invadens Drew Tsuruta & White (Diptera: Tephritidae) et Physophoropterella bendroiti Poppius (Hemiptera: Miridae) sévissent prépondéremment dans l’agroécosystème urbain. Apis mellifera andansoni Latreille (Apidae) est la principale espèce pollinisatrice, en milieu urbain. Pseudonoorda edulis a été le ravageur le plus dommageable des fruits du safoutier, et des informations de base sur sa prévalence, sa biologie et ses caractéristiques morphométriques ont été fournies dans ce travail. Ces résultats apportent une meilleure connaissance des ravageurs et pollinisateurs de D. edulis au Gabon. Des études ultérieures devraient être conduites sur un environnement plus large de la culture, mais surtout cibler la recherche des mesures de contrôle biologique de P. edulis. [less ▲]

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See detailEtude du recyclage de l'eau résiduaire dans la flottation des minerais oxydés cuprocobaltifères du gisement de Luiswishi
Shengo Lutandula, Michel ULg

Doctoral thesis (2014)

The present work aims at improving practices in the management of wastewater from flotation of ores in the Katanga province and suggests the recycling considering its advantages on the environment ... [more ▼]

The present work aims at improving practices in the management of wastewater from flotation of ores in the Katanga province and suggests the recycling considering its advantages on the environment safeguarding, the sustainable management of hydric resources and the economy of flotation reagents standpoint. It focuses on the determination of the best process water-recycling rate in flotation of copper - cobalt oxidised ores from the Luiswishi deposit and on the explanation of phenomena implicated in the depression of malachite and heterogenite in the recycled water presence. The studied ores have been sulphidised (NaSH) prior to flotation with KAX using the process water recovered from the industrial effluents and a Lab scale replication of the New Concentrator in Kipushi (NCK) flow sheet to simulate the full-size plant operations. The following methodological approach has been adopted: • The lab flotation tests of the pulps originating from the NCK grinding circuit while varying the proportion of the recycled process water added to the feed water in view to determine the proportion which gives a concentrate grading at least 2% Co at the recovery of 80% and at least 7% Co at the recovery of 60% respectively at the rougher and cleaner stages; • The study of the effects from the recycled water chemical components on flotation of malachite and heterogenite through flotation of the studied ores in the presence of S2O32-, SO42-, HCO3-, Ca2+ and Mg2+ introduced in the feed water (demineralised water) through dissolution of their analytical graded-salts and based on the follow-up of the Cu-Co recovery and the roughing flotation concentrates mineralogical analysis by the polarised light microscopy, the X- rays diffraction and the scanning electron microscopy; • The study of the behaviour of malachite and heterogenite based firstly on electrochemical investigations of the pulp (pH, Eh, Es and DO), the leaching tests and sulphidisation of malachite and heterogenite with NaSH in presence of S2O32-, SO42- and HCO3. Secondly, based on thermodynamical calculations for the establishment of the Pourbaix diagrams of the systems Cu(Co-Cu) – Chemical species – Water at 25 °C and the Drift spectroscopic analysis (4000 à 400 cm-1) of malachite after sulphidisation with NaSH and agitation with KAX in the presence of S2O32-, SO42- and HCO3-. The obtained results have shown that the process water recycling is successful when 20% of the recycled water is added to the feed water since one obtains a concentrate grading 2% Co at the recovery of 80% at the rougher stage. However, considering the significant drops in the grade and the recovery of cobalt in the concentrate observed at the cleaner stage, a proportion of 10% has been suggested as optimal for the overall flotation circuit because 82% cobalt were recovered at rougher stage bringing at the cleaner stage a concentrate grading 9.5% Co at the recovery of 63%. Beyond 10%, the process water recycling has proved detrimental to flotation efficiency owing to the build-up of chemical species (S2O32-, SO42-, HCO3-, Ca2+, Mg2+ and Cl-) in the feed water, which becomes corrosive and scaling leading to depression of malachite and heterogenite. This depression results from an increase in the valuable minerals hydrophilicity boosted-up by their strong dissolution in water in the presence of S2O32-, SO42 and HCO3- leading to alterations in their surface properties and the exaggerated liberation of copper and cobalt ions in solution responsible for the overconsumption of NaSH and KAX. [less ▲]

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See detailVariabilité morphologique, génétique et chimique de Cananga odorata [Lam.] Hook.f. & Thoms. en vue de l'amélioration qualitative de la production de l'huile essentielle d'ylang-ylang dans les îles de l'Océan Indien
Benini, Céline ULg

Doctoral thesis (2014)

Summary: Cananga odorata (Lam.) Hook f. & Thomson forma genuina (Annonaceae) commonly called ylang-ylang is an essential oil tree used in the preparation of cosmetics. Despite this plant is an ... [more ▼]

Summary: Cananga odorata (Lam.) Hook f. & Thomson forma genuina (Annonaceae) commonly called ylang-ylang is an essential oil tree used in the preparation of cosmetics. Despite this plant is an indispensable source of incomes for the producing islands, and despite its essential oil is valued by the cosmetic industry, only few studies have been conducted. Ylang-ylang essential oil sector is dying and conservation and valorization strategies are urgently needed to preserve it. During this thesis, we tried to gather the necessary data to achieve this goal. We thus characterized the variability of ylang-ylang at morphological, genetic and chemical levels. This study revealed an important variability in the chemical composition of ylang-ylang essential oil in the study area. In order to suggest valorization and conservation strategies tailored to the current context, we needed to know the causes responsible for the chemical polymorphism. These causes are to be found probably in the environmental variability. Indeed, the genetic structure only revealed few consistencies with the chemical polymorphism. It would be though wiser to further investigate these two potential causes of the chemical variability of ylang-ylang as our study is pioneer in this field. On the basis of the data collected, we then proposed a market-oriented valorization of the genetic and chemical diversity (uniformity of the quality and the composition of ylang-ylang essential oils, raw material sources and quality labels). In terms of genetic and chemical conservation, we propose a conservation strategy mainly based on an on-farm conservation in plantation. We also propose integrated valorization strategies of the on-farm conservation (direct sales and tourism). [less ▲]

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See detailDetermination of the relationship between foam morphology and electrical conductivity of polymer/carbon nanotube nanocomposite foams
Tran, Minh Phuong ULg

Doctoral thesis (2014)

The lightweight of porous nanocomposites makes them attractive materials for various applications such as thermal and sound barriers, shock absorbers, insulation, packaging, and their porous structure is ... [more ▼]

The lightweight of porous nanocomposites makes them attractive materials for various applications such as thermal and sound barriers, shock absorbers, insulation, packaging, and their porous structure is very interesting in bone tissue engineering. Moreover, the incorporation of appropriate carbonaceous nanoparticles into polymeric foams contributes to the reinforcement of their mechanical performances but also renders them electrically conductive, consequently extending their potential interest in electromagnetic shielding (EMI) and electrostatic discharge (ESD) applications for instance. In this PhD thesis, we aim at designing various polymeric foams containing a conductive nanofiller (carbon nanotubes) and to identify the main morphological parameters (pore size, cell density, cell wall thickness,…) that affect and govern the final properties of the foams. In this work, the electrical conductivity of the foams is the main property investigated because it is governing their performances as materials for EMI absorbers, the main application targeted in this work. These important morphology/electrical conductivity relationships would indeed be very useful to guide the foam development towards the material with the best performances for the targeted applications. Two different foaming methods are used in this work: (i) the supercritical CO2 (scCO2) foaming technology and (ii) the freeze-drying process. The first technique enables to produce isotropic foams with spherical closed cells structures and the second one, oriented anisotropic foams with cylindrical open cells. The variation of the foaming parameters allows preparing foams with a large panel of morphologies required for the establishment of the structure/properties relationships. In parallel to this main objective, an improvement of the overall conductive performances of the nanocomposites foams is also investigated through the optimization of the foam morphology and the content in conductive nanofillers. [less ▲]

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See detailDe l'écologie d'un discours heuristique d'acculturation à l'algèbre linéaire
DUNIA MWATI, Adrien

Doctoral thesis (2014)

ABSTRACT : Our research examines the sustainability of an acculturation heuristic discourse to Linear Algebra, prototypical gradual development of this discipline in a dialectical process with elementary ... [more ▼]

ABSTRACT : Our research examines the sustainability of an acculturation heuristic discourse to Linear Algebra, prototypical gradual development of this discipline in a dialectical process with elementary geometry. Our theoretical frameworks are borrowed from mathematics Didactic : mainly, Theory of Didactic Situations by Brousseau and Anthropological Theory of Didactics by Chevallard. These theories have enabled us to problematize the studied issue and make it a teaching "phenomenon" by giving intelligibility to the observations in a way that they are interpreted in a falsifiable hypothesis ( in Popper's sense ) which may integrate them all . In this context, the strict meaning given by Lakatos to heuristic speech has been broadly extended in terms of fundamental situation and praxeologies “modeling” according to Job and Schneider. A rational reading of historical and epistemological development of linear algebra then allowed us to build a "reference epistemological model" not only allowing us to answer to the question: "what is it to do linear algebra ?", but also to legitimize the referent heuristic discourse that served us as “phénoménotechnique”. Considering that our study is well marked, we have experimented in "secondary" and "university" institutions a heuristic device based on some selected aspects of the referent heuristic discourse. The analysis of observable that empirical work has identified has led us to identify several factors that combine to determine the ecological fragility of this speech and are at different levels of scale didactic codetermination (by Chevallard) : - The institutional variation of the curriculum of secondary education part in relation to linear systems. Including an emphasis on a resolution systems contract at the expense of their discussion, with a focus placed on the substitution method ; little technological discourse on the principles of equivalence systems and no intelligibility in terms of beams ; little work on equations as constraints with an impact on the lack of connection between the solution space of a system and the number of "independent" constraints, and finally, no ecological niche for the study of systems due to fragmentation of knowledge involved in multiple chapters. - The constraints inherent in the process of didactic transposition in terms of depersonalization and “désyncrétisation” of the knowledge but also in terms of progress in teaching time or chronogenesis. - Constraints related to teaching : a teacher accommodation to a socio-constructivist paradigm which appears as disguised exposition (ostension) and some ineffective activities ; a university pedagogy marked by “applicationnisme”, protectionism and a timing organization that puts theory on a pedestal where it is no longer in question. - An allegiance to the "mathematical" institution that is manifested, for instance, by some emblematic gestures linked to the mathematic rigor and which do not have great functionality. - Finally, an influence of the work of mathematicians on the didactic transposition, in the era of modern mathematics, which still inspires today didactic way, impeding (or being an obstacle for) linear algebra construction in dialectic with the geometry. The selected scenario for the role of interpretive hypothesis articulating these factors questions, in turn, all our education system which is too inspired by deductive theories in their completed text application. [less ▲]

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See detailLa discipline scolaire "français" : du questionnement identitaire à la conscience disciplinaire. Panorama sur les zones avancées de la francophonie et gros plan sur le cas particulier de l'enseignement du français au secondaire supérieur en Fédération Wallonie-Bruxelles
Van Beveren, Julien ULg

Doctoral thesis (2014)

Après avoir envisagé l'introduction de l'approche par compétences et l'élargissement du corpus des supports d'apprentissage du cours de français comme deux des causes possibles de la crise identitaire que ... [more ▼]

Après avoir envisagé l'introduction de l'approche par compétences et l'élargissement du corpus des supports d'apprentissage du cours de français comme deux des causes possibles de la crise identitaire que nous semble traverser cette discipline scolaire, nous nous sommes livré à l'analyse d'un grand nombre de livraisons de la revue de l'Association internationale des chercheurs en didactique du français, afin de nous interroger sur la rareté des publications ayant trait à la discipline scolaire "français" dans son ensemble. Dans la troisième partie de notre thèse, nous nous sommes penché sur la notion de discipline scolaire et sur quelques syntagmes qui y sont liés, avant de nous focaliser sur l'enseignement-apprentissage du français, au secondaire supérieur, en Fédération Wallonie-Bruxelles. Ajoutons que c'est surtout selon la perspective du didacticien-formateur que nous avons analysé cet enseignement-apprentissage. [less ▲]

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See detailSpace-variant optical phase retarders in liquid crystal polymers and their applications
Piron, Pierre ULg

Doctoral thesis (2014)

During the last decade, extensive investigations were performed to achieve optical phase retarders with a space-variant orientation of their fast axis. These retarders present unique behaviors and they ... [more ▼]

During the last decade, extensive investigations were performed to achieve optical phase retarders with a space-variant orientation of their fast axis. These retarders present unique behaviors and they can be used for several applications such as polarization analysis, beam splitting, phase mask coronagraphy, optical tweezers … The present thesis is dedicated to the development of space-variant retarders made out of liquid crystal polymers recorded by polarization holography. The liquid crystals define the fast axis orientation of the retarder. Polarization holography is based on the superimposition of differently polarized beams to achieve the electric field required to properly align the liquid crystals without mechanical action. In the present work, we start with an introduction about the space-variant retarders, their characteristics and current recording methods, which usually require mechanical action. In the second chapter, polarization holography and several simple examples are presented as well as the liquid crystal polymers, their generic recording process and the first prototypes. In chapter three, the first application that we developed is exposed. It consists in a polarization analysis method based on a retarder characterized by a variation in one dimension of its fast axis orientation. The principle of the method, numerical simulations and the first results are exposed. Chapter four cares about the second application based on a separator of polarization state. The mathematical model and its application to shearography are exposed. In chapter five, another kind of retarders is introduced. These retarders are characterized by a rotation of their fast axis along the center of the retarder. Their properties, the recording systems and the first prototypes are detailed and analyzed. In the last chapter, the application of our retarder to coronagraphy is presented and their performances are computed for different configurations based on experimental constrains. Finally, we conclude with the improvements of our applications and future uses of these retarders. [less ▲]

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See detailContribution à l’amélioration de l’épidémiosurveillance des maladies animales en Afrique francophone de l’Ouest et du Centre
Ouagal, Mahamat ULg

Doctoral thesis (2014)

Livestock is an important source of income in most developing countries. In Africa, it often makes up 10% to 20% of the gross national product at level. One of the major constraints to the development of ... [more ▼]

Livestock is an important source of income in most developing countries. In Africa, it often makes up 10% to 20% of the gross national product at level. One of the major constraints to the development of this sector is animal diseases, which sometimes generate significant economic losses with social consequences that are often very burdensome for farmers. They restrict trade between countries. Reducing the impact of these constraints necessarily involves the prevention and the control of diseases. For this purpose, an adequate knowledge of the epidemiology of the diseases is a prerequisite to define a strategy for their prevention and/or the design of appropriate monitoring measures. One of the essential tools of production remains the epidemiological information network for the surveillance of animal diseases. It is also a tool for decision in international trade involving livestock products. For this purpose, its effectiveness is a guarantee for its credibility. An effective network system must be well organized, meet scientific standards and satisfy the efficiency characteristics which are sensitivity, specificity, acceptability, responsiveness and cost. In west and central Africa, epidemiological surveillance networks of animal diseases are mostly created in the 1990s through the Pan African Program for the Control of Epizootics. A 2004 assessment carried out by this program revealed that these networks are at different stages and found weaknesses in their efficiency. To contribute to the improvement of these systems, an analysis of some performance parameters of these networks has been conducted and suggestions for improvement were made. To achieve this overall objective, the following specific objectives were listed: (i) analyze the technical and functional organization of epidemiological surveillance networks in West and Central Africa; (ii) compare the effectiveness of active surveillance and passive surveillance, the two main monitoring methods used by the networks in West and Central Africa using the case study of the epidemiological surveillance network, in Chad, namely REPIMAT; (iii) assess the sensitivity of an epidemiological surveillance network from an approach based on prevalence of a disease such as Foot and Mouth Disease; (iv) develop performance indicators for regular monitoring of the epidemiological surveillance network for animal diseases in West and Central Africa, again by taking the case of REPIMAT; and finally, (v) estimate the cost incurred by an epidemiological surveillance network in West and Central Africa, for example the REPIMAT. Each of these specific objectives leads to a specific study of which results are presented below: Organization of epidemiological surveillance networks in West and Central Africa The survey on technical and institutional organizations networks in west and central Africa was organised on the basis of a written questionnaire. It involved nine networks of which five were in West Africa (Senegal, Burkina Faso, Ivory Coast, Togo, Guinea) and four in Central Africa (Cameroon, Central African Republic, Democratic Republic of Congo and Chad). The results of this survey showed that the oldest epidemiological surveillance network is that of Chad, REPIMAT. There are more similarities than differences between these networks. In general, network monitoring of animal diseases in west and central Africa are technically and institutionally well formalized. The establishment and operation of the networks surveyed are mainly financed by foreign aid. In general, these are epidemiological surveillance networks that monitor several diseases. All countries surveyed have a central national laboratory for the analysis of samples collected. However, only four countries (Cameroon, Côte d'Ivoire, Guinea and Senegal) can make a diagnosis of all diseases selected for monitoring. The laboratories are considered as partners with surveillance networks in most of the countries surveyed. All networks use the PID/ARIS for data management. In addition to the latter, countries such as Guinea, DRC, Senegal and Chad use a national database developed with Access®. On average, 26% of veterinary stations on the total networks surveyed are involved in the monitoring. This proportion varies from 7% to 91%. However, insufficient diagnostic capacity of laboratories and inadequate operational steering committees are the two main weaknesses of the networks concerned with this survey. Comparison between active and passive surveillance within the network of epidemiological surveillance of animal diseases in Chad The comparison between active and passive surveillance involved 106 REPIMAT surveillance stations randomly divided into 52 active surveillance stations and 54 passive surveillance stations. Vaccination status of nine diseases and their respective prevalence levels are monitored by the network. A work plan was developed for each station. The stations of active surveillance make monthly visits to four herds (villages) to look for monitored diseases and also organise four information meetings with farmers how to react in case of suspicion of the monitored diseases. Passive surveillance stations only organise, monthly, four information meetings with farmers. Suspicions in each station are recorded on a specific form developed for each disease. The agent mentions if the suspicion is performed following a breeder call, a visit from herds or a sensitization meeting. Monitoring lasted 24 months. The results of this study showed that regardless of the type of surveillance, diseases monitored with the exception of rare diseases (Rinderpest, and Rift Valley fever) are reported by the monitoring agents. However, we note that the number of calls recorded following suspicions of farmers (41%) was significantly higher (p <0.05) than suspicions made during visits to herds (30%) or in meetings (29%). For moderately prevalent diseases, the suspicions are mainly calls farmers (77%) and regardless of the type of monitoring (73% for active surveillance and 84% for passive surveillance). On the other hand, for FMD, a disease with high prevalence, 37% of suspicions are recorded by visiting farms. Overall, no significant difference was observed between the types of surveillance because of a low rate of disease onset during sensitization meetings by the active surveillance stations. Passive surveillance stimulated by awareness meetings appears to be a mode for surveillance in the conditions of Chad and cheaper. However, for rare diseases, the specific methods of active surveillance (such as, for example, sentinel flocks) seems preferable. Evaluation of the sensitivity of the animal disease epidemiological surveillance network for Foot and Mouth Disease in Chad Evaluation of the sensitivity of the animal disease epidemiological surveillance network for Foot and Mouth Disease in Chad The study on the network sensitivity was carried out in REPIMAT by taking the surveillance of FMD as an example. FMD is the disease most frequently suspected by REPIMAT. However, the reporting of cases is limited to clinical suspicion. The samples for the purpose of laboratory diagnostic for confirmation of these suspicions are not made. In order to assess the sensitivity of REPIMAT for this disease, a serological survey was conducted in eight of the nine regional delegations with the highest cattle population of the country. The samples were analyzed by the National Reference Laboratory for FMD in Brescia (Italy) with the support of the European Commission action against FMD. The 3ABC and SP-ELISA tests were used for the detection of antibodies and the serotype of the virus. The number of FMD suspicions reported within the network was compared with the seroprevalence. Epidemiological information on the disease, including the circulating serotypes in Chad, was also provided. A total of 796 cattle sera were collected. The seroprevalence rate at individual level was 35.6% (95% CI: 32.2 to 39.0) and that at the herd level was 61.9% (95% CI: 51.9 to 71.2). A strong correlation was observed between the estimated prevalence and number of clinical suspicions reported within REPIMAT. The disease is present in all livestock regional delegations surveyed with a high prevalence in the delegations located in the south, the wettest area, and where cross-border movements are the most important. Serotypes A, O, SAT1and SAT2 were identified. Development of operating performance indicators of Chad epidemiological surveillance network for animal diseases: REPIMAT The maintenance and effectiveness of a disease monitoring system requires regular evaluation to identify timely deficiencies that may occur. For this purpose, the performance indicators are essential tools. One approach for developing performance indicators as well as their application in the operation of 43 monitoring stations REPIMAT was carried out. An analysis of the objectives and operation mechanism of REPIMAT allowed retaining three main components, namely the field workers, the animation cell and the laboratory. The activities of each of these components were listed. The analysis of the outcomes of these activities resulted in the development of the performance indicators that can be used in the operation of REPIMAT. The application of these indicators has highlighted the weaknesses of each component. Estimated cost of a network for animal diseases epidemiological surveillance in Central Africa: the case of Chad network In sub-Saharan Africa, most of the networks for epidemiological surveillance of animal diseases were temporarily financed by external aid. The sustainability of such decision support tools should have been insured by national public funds. The objective of this study was to estimate the costs involved in running an animal disease epidemiological surveillance network by taking the example of such network in Chad (REPIMAT) and its weight in the state budget. These costs were then compared to those of other epidemiological surveillance in West Africa networks. The results of this study showed that the total annual operating and implementing cost of REPIMAT is estimated at € 666 349 (437 096 291 FCFA) for the entire system comprising 106 monitoring stations constituting the local level, 26 livestock sectors, nine regional livestock delegations representing the intermediate level and an animation cell constituting the central level. This cost represents only 3% (2% of fixed costs and 1% of variable costs) of the budget allocated by the Chadian Ministry of Livestock. Fixed costs (72%) weighed more than variable costs (28%) regardless of the levels of intervention. This estimate is similar to the estimated costs of epidemiological surveillance networks in Benin, Ghana, Mauritania and Senegal. Considering only the variable costs (operation), the annual cost of operating a surveillance station, the most important entity in the system was only 932 € or 611 352 FCFA. The surveillance cost is mainly related at the local level (surveillance stations) and intermediate level (livestock sectors and regional livestock delegations) to the cost involved in health surveillance as well as the equipment it requires. This thesis allowed to analyze some parameters of effectiveness of a surveillance network for animal diseases including general organization, type of surveillance, sensitivity, cost and to develop a tool for continuous monitoring of operating a network. It is difficult to meet all the efficiency criteria of an animal disease surveillance network, however, the few parameters studied which are interrelated will help if they are used properly to improve the efficiency of an epidemiological surveillance system of animal diseases in sub-Saharan Africa. [less ▲]

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See detailMathematical modeling od the mitral valve. From local to global hemodynamics
Paeme, Sabine ULg

Doctoral thesis (2014)

Mitral valve dysfunction is a relatively common heart disease which typically requires mechanical valve replacement, with consequent high social and economic costs. More specifically, ischemic mitral ... [more ▼]

Mitral valve dysfunction is a relatively common heart disease which typically requires mechanical valve replacement, with consequent high social and economic costs. More specifically, ischemic mitral insufficiency following myocardial infarction has a dynamic behavior that can lead to failure in its detection in certain patients, creating a situation with increased risk of morbidity and mortality. Improving the tracking and the control of valvular pathologies is therefore crucial, as it offers significant opportunities to improve care, costs and prognosis for patients with this disease. To study heart and cardiac valve dysfunction, cardiologists need information about detailed pressure and flow dynamics around and through the valves, atria and ventricles. However, non-invasive information about pressure is currently limited to indices at specific times and invasive catheterization data, which is more traumatic for the patient, is not usually routinely available. One alternative to this involves mathematical modeling of the cardiovascular system which offers a non-invasive and inexpensive way of studying cardiac and circulatory dynamics. This is particularly beneficial where detailed, continuous measurements may not be practicable. This study consisted of the development of a multi-scale closed-loop model of the cardiovascular system that accounted for progressive mitral valve aperture area over the entire cardiac cycle. This multi-scale model, which included detailed mitral valve and left atrium models, was tested over a range of physiological situations and clinical data. The goal was to validate the model’s ability to reproduce clinically measured physiological and pathophysiological behavior in a manner that would enable a model to be made patient-specific using available data. The resulting model was designed to be made patient-specific, and thus capture and reproduce the patient’s unique hemodynamic state on both global and local scales. In particular, it was shown to provide significant information about the patient’s mitral valve dynamics and the detailed flow dynamics and pressure around it. These data are not currently available without extensive, invasive measurements, and this therefore represents a significant step forward in model-based sensing and diagnosis. It is hoped that the model and methods developed in this study will be a powerful tool in assisting medical teams in investigating, tracking, diagnosing and controlling the cardiovascular system. More specifically, the mitral valve, as well as other similar valves, could be directly monitored to improve the diagnosis, costs and prognosis of valvular dysfunction. Furthermore, the overall results justify detailed in vivo animal experiments to thoroughly validate these models and methods in advance of clinical trials. [less ▲]

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See detailProtein Structural Annotation: Multi-Task Learning and Feature Selection
Becker, Julien ULg

Doctoral thesis (2014)

Experimentally determining the three-dimensional structure of a protein is a slow and expensive process. Nowadays, supervised machine learning techniques are widely used to predict protein structures, and ... [more ▼]

Experimentally determining the three-dimensional structure of a protein is a slow and expensive process. Nowadays, supervised machine learning techniques are widely used to predict protein structures, and in particular to predict surrogate annotations, which are much less complex than 3D structures. This dissertation presents, on the one hand, methodological contributions for learning multiple tasks simultaneously and for selecting relevant feature representations, and on the other hand, biological contributions issued from the application of these techniques on several protein annotation problems. Our first methodological contribution introduces a multi-task formulation for learning various protein structural annotation tasks. Unlike the traditional methods proposed in the bioinformatics literature, which mostly treated these tasks independently, our framework exploits the natural idea that multiple related prediction tasks should be designed simultaneously. Our empirical experiments on a set of five sequence labeling tasks clearly highlight the benefit of our multi-task approach against single-task approaches in terms of correctly predicted labels. Our second methodological contribution focuses on the best way to identify a minimal subset of feature functions, {\em i.e.}, functions that encode properties of complex objects, such as sequences or graphs, into appropriate forms (typically, vectors of features) for learning algorithms. Our empirical experiments on disulfide connectivity pattern prediction and disordered regions prediction show that using carefully selected feature functions combined with ensembles of extremely randomized trees lead to very accurate models. Our biological contributions are mainly issued from the results obtained by the application of our feature function selection algorithm on the problems of predicting disulfide connectivity patterns and of predicting disordered regions. In both cases, our approach identified a relevant representation of the data that should play a role in the prediction of disulfide bonds (respectively, disordered regions) and, consequently, in protein structure-function relationships. For example, the major biological contribution made by our method is the discovery of a novel feature function, which has - to our best knowledge - never been highlighted in the context of predicting disordered regions. These representations were carefully assessed against several baselines such as the 10th Critical Assessment of Techniques for Protein Structure Prediction (CASP) competition. [less ▲]

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See detailNanobodies as tools to investigate the mechanism of aggregation of chimeric proteins made by the insertion of polyglutamine stretches into the beta-lactamase BlaP
Pain, Coralie ULg

Doctoral thesis (2014)

Among the neurodegenerative amyloidoses, ten disorders, referred to as polyglutamine (polyQ) diseases and including Huntington's disease and several spinocerebellar ataxias, are associated with ten ... [more ▼]

Among the neurodegenerative amyloidoses, ten disorders, referred to as polyglutamine (polyQ) diseases and including Huntington's disease and several spinocerebellar ataxias, are associated with ten proteins within which a polyQ tract is expanded above a threshold of typically 35-45 glutamine residues. Such expanded polyQ tracts lead to the aggregation of the host protein into amyloid fibrils that accumulate in the nucleus of some populations of neurons; these aggregates or some of their precursors are thought to contribute to neuronal death. So far, no preventive or curative treatment exists for these devastating pathologies. While the expansion of the polyQ tract above the threshold is the determinant factor for aggregation, recent studies suggest that non-polyQ regions of these proteins can play a significant role, either preventative or facilitative, in the aggregation process. The general principles governing the complex interplay between the role of the expanded polyQ tract and the role of the non-polyQ regions in the aggregation process are not well understood yet. In order to develop therapeutic strategies, it is important to better understand this complex interplay. To contribute to this aim, we have engineered chimeric proteins via the insertion of polyQ repeats of various lengths (23, 30, 55 and 79Q) into two sites (197 and 216) of the BlaP beta-lactamase from Bacillus licheniformis 749/C. The properties of these chimeric proteins recapitulate the characteristic features of the disease-associated polyQ proteins, i.e. (i) there is a minimum number of inserted glutamines (threshold) required to trigger the aggregation of the chimeras into amyloid fibrils, and (ii) above the threshold, the longer the polyQ tract, the faster the aggregation. Interestingly, for the same polyQ length, the chimeras with insertions in position 216 have an increased propensity to form amyloid fibrils compared to their counterparts with insertions in position 197. These findings highlight the strong influence of the overall protein context on aggregation triggered by expanded polyQ tracts. This thesis addresses the use of the variable domains of camelid heavy-chain antibodies, referred to as nanobodies or VHHs, as structural and mechanistic probes to better understand the different aggregating properties of the two sets of BlaP-polyQ chimeras (197 and 216). We have also performed limited proteolysis experiments and transglutaminase-mediated reactions on the monomeric form of the BlaP-polyQ chimeras to further investigate the effects of the polyQ insertions on the structure and dynamics of the BlaP moiety, as well as the structure of the polyQ tract itself. From the blood of a llama immunised with BlaP197(Gln)55, we isolated more than 60 VHHs specific to the BlaP-polyQ chimeras. Twenty eight of them were produced, purified and characterised. These VHHs were found to be all specific to the BlaP moiety and could be classified into four different groups recognising distinct epitopes on the surface of BlaP. One representative VHH of each group (i.e. cAb-A3S, cAb-H7S, cAb-F11N and cAb-G10S) was selected as probe to investigate the mechanism of aggregation of the BlaP-polyQ chimeras. The epitope of three of them was determined by X-ray diffraction and/or by NMR spectroscopy. Although they recognise distinct epitopes and exhibit different affinities for BlaP, the binding of the four VHHs significantly slows down the aggregation of all the BlaP-polyQ chimeras investigated (i.e. BlaP197(Gln)55, BlaP197(Gln)79 and BlaP216(Gln)79). The extent of inhibition depends however on the chimera and on the experimental conditions. We show that the inhibition of the aggregation of BlaP197(Gln)55 and BlaP197(Gln)79 upon binding of the four VHHs is correlated with the stabilisation of their native state. In the case of BlaP216(Gln)79, the extent of inhibition could not be only correlated to the stabilisation of its native state; the location of the epitope of the VHH is instead also determinant. This observation demonstrates that the lower thermodynamic stability of BlaP216(Gln)79 is not the unique factor responsible for its increased aggregation propensity. It also further highlights the complexity of the aggregation mechanism of polyQ proteins and the strong influence of the non-polyQ regions on the amyloid fibril formation triggered by the expanded polyQ tract. All together our results suggest that antibodies or antibody fragments raised against the non-polyQ regions of polyQ proteins associated with diseases could constitute a relevant therapeutic strategy. They also further demonstrate the power of nanobodies as probes to get a deeper knowledge of the underlying mechanisms of amyloid fibril formation. The preliminary limited proteolysis and transglutamination experiments obtained suggest that the polyQ tracts are all flexible, except that of 23 glutamines inserted in position 197 of BlaP, which seems to be more rigid than the others. The results obtained confirm that, globally, the structure of BlaP is not significantly modified by the insertions while the 216 chimeras seem more dynamic than the 197 chimeras. [less ▲]

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See detailContribution à l'étude de la réponse immune au cours d'une infection à Microsporum canis et établissement d'un modèle murin de dermatophytose
Cambier, Ludivine ULg

Doctoral thesis (2014)

Les dermatophytoses (ou « teignes ») sont des mycoses cutanées superficielles provoquées par des champignons filamenteux, appelés dermatophytes, affectant les animaux et l’homme. Microsporum canis est un ... [more ▼]

Les dermatophytoses (ou « teignes ») sont des mycoses cutanées superficielles provoquées par des champignons filamenteux, appelés dermatophytes, affectant les animaux et l’homme. Microsporum canis est un dermatophyte zoophile dont l’hôte naturel est le chat. Il touche principalement les carnivores domestiques et est un agent fréquent de zoonose. Les dermatophytes envahissant les structures kératinisées de l’épiderme, de nombreuses études ont porté sur la caractérisation des protéases sécrétées comme facteurs de virulence potentiels. Cependant, peu de recherches ont été consacrées aux mécanismes impliqués dans la mise en place de la réponse immune anti-dermatophytes. Il est couramment admis que la réponse immune protectrice lors d’une dermatophytose est une réponse à médiation cellulaire impliquant les lymphocytes de type Th1 et caractérisée par une réaction cutanée d’hypersensibilité de type retardé (Delayed Type Hypersentivity, DTH). Un constituant sécrété de M. canis correspondant au surnageant de culture du champignon cultivé sur milieu de Sabouraud liquide, appelé surnageant non induit (SNI), provoque des DTH chez le cobaye immunisé après une primo-infection, ce qui suggère que le SNI contient des antigènes potentiellement intéressants pour le développement d’un vaccin. Le cobaye est le modèle animal le plus utilisé pour étudier l’immunologie des dermatophytoses. Cependant, la quasi absence d’outils génétiques et immunologiques dans cette espèce ne permet pas d’étudier la réponse immune induite lors de dermatophytoses de manière satisfaisante. La mise au point d’un modèle murin de dermatophytose permettrait de pallier tous ces inconvénients. Au cours d’une dermatophytose à M. canis, les premières cellules rencontrées par le champignon lors de l’infection sont les kératinocytes qui, suite à l’activation par des composants fongiques, peuvent attirer les polymorphonucléaires neutrophiles (PMN) sur le site d’infection. Ces leucocytes sont, avec les macrophages, responsables in fine de l’élimination du dermatophyte. Cependant, le rôle des PMN dans les mécanismes liés à l’établissement de l’immunité anti-dermatophytes demeure inconnu. L’objectif général de ce travail était de contribuer à l’étude de la réponse immune au cours d’une dermatophytose à M. canis et de mettre au point un nouveau modèle animal de dermatophytose. Pour l’atteindre, trois études ont été réalisées : (1) l’évaluation du rôle des PMN félins dans la mise en place d’une réponse immune protectrice au cours d’une dermatophytose à M. canis, (2) l’évaluation des propriétés protectrices du SNI de M. canis dans un essai vaccinal en utilisant le cobaye comme modèle expérimental et (3) la mise au point d’un modèle murin de dermatophytose pour l’étude de l’immunité anti-dermatophytes. Résumé 2 Les résultats obtenus dans la première étude montrent que les PMN félins produisent des cytokines pro-inflammatoires telles le tumor necrosis factor (TNF)-α, l’interleukin (IL)-1β et l’IL-8 lorsqu’ils sont stimulés par les arthrospores vivantes du champignon ainsi que par des constituants structuraux, représentés par des arthrospores tuées par la chaleur, et sécrétés comme le SNI. De plus, après stimulation pendant 2 ou 4 heures par les arthrospores vivantes et tuées ainsi que par les protéases sécrétées Sub3 et Sub6, disponibles sous forme recombinante dans notre laboratoire, les taux d’ARNm du toll like receptor (TLR)-2 et du TLR-4 étaient augmentés dans les PMN. Ces résultats suggèrent que les PMN félins jouent un rôle dans l’établissement de la réponse immune anti-M. canis en produisant des cytokines pro-inflammatoires et que les mécanismes responsables de cette activation feraient intervenir les récepteurs TLR-2 et TLR-4. Dans la deuxième étude, les résultats indiquent que l’adjuvant monophosphoryl lipid-A (MPLA), dérivé non toxique du lipopolysaccharide et agoniste du TLR-4 a, à lui seul, un effet protecteur partiel chez les cobayes soumis à une épreuve d’infection par M. canis. En effet, les symptômes cutanés observés chez les cobayes ayant préalablement reçu l’adjuvant, étaient moins importants que ceux développés par les cobayes infectés n’ayant pas reçu l’adjuvant. En revanche, le SNI ne semble pas protéger les cobayes d’une infection expérimentale dans cet essai vaccinal. Les résultats obtenus dans la troisième étude démontrent que notre modèle murin de dermatophytose est valide et reproductible, en utilisant Arthroderma benhamiae et Arthroderma vanbreuseghemii. Ce n’est pas le cas avec M. canis. En effet, 100 % et 80 % des souris infectées respectivement par A. vanbreuseghemii et A. benhamiae ont développé des symptômes cutanés typiques de dermatophytose, à savoir de l’érythème, des squames, des croûtes et de l’alopécie alors que seulement 40 % des souris infectées par M. canis ont développé des signes cliniques, par ailleurs très discrets. Le recrutement important de PMN dans la peau des souris infectées par A. benhamiae et A. vanbreuseghemii et le profil cytokinique (transforming growth factor (TGF)-β, l’IL-1β, l’IL-6 et l’IL-22) généré par l’infection suggèrent l’implication de la voie Th17 dans la mise en place de la réponse immune anti-dermatophytes. En conclusion, l’ensemble de ce travail a contribué à élargir nos connaissances sur la réponse immune au cours d’une dermatophytose à M. canis. De plus, un nouveau modèle murin de dermatophytose à A. benhamiae et A. vanbreuseghemii a été mis au point et est approprié pour l’étude de la réponse immune anti-dermatophytes. [less ▲]

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