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See detailGeometric optimization algorithms for linear regression on fixed-rank matrices
Meyer, Gilles ULg

Doctoral thesis (2011)

Nowadays, large and rapidly evolving data sets are commonly encountered in many modern applications. Efficiently mining and exploiting these data sets generally results in the extraction of valuable ... [more ▼]

Nowadays, large and rapidly evolving data sets are commonly encountered in many modern applications. Efficiently mining and exploiting these data sets generally results in the extraction of valuable information and therefore appears as an important challenge in various domains including network security, computer vision, internet search engines, bioinformatics, marketing systems, online advertisement, social networks, just to name a few. The rapid development of these modern computer science applications sustains an ever-increasing demand for efficient machine learning algorithms that can cope with large-scale problems, characterized by a large number of samples and a large number of variables. The research reported in the present thesis is devoted to the design of efficient machine learning algorithms for large-scale problems. Specifically, we adopt a geometric optimization viewpoint to address the problem of linear regression in nonlinear and high-dimensional matrix search spaces. Our purpose is to efficiently exploit the geometric structure of the search space in the design of scalable linear regression algorithms. Our search space of main interest will be the set of low-rank matrices. Learning a low-rank matrix is a typical approach to cope with high-dimensional problems. The low-rank constraint is expected to force the learning algorithm to capture a limited number of dominant factors that mostly influence the sought solution. We consider both the learning of a fixed-rank symmetric positive semidefinite matrix and of a fixed-rank non-symmetric matrix. A first contribution of the thesis is to show that many modern machine learning problems can be formulated as linear regression problems on the set of fixed-rank matrices. For example, the learning of a low-rank distance, low-rank matrix completion and the learning on data pairs are cast into the considered linear regression framework. For these problems, the low-rank constraint is either part of the original problem formulation or is a sound approximation that significantly reduces the original problem size and complexity, resulting in a dramatic decrease in the computational complexity of algorithms. Our main contribution is the development of novel efficient algorithms for learning a linear regression model parameterized by a fixed-rank matrix. The resulting algorithms preserve the underlying geometric structure of the problem, scale to high-dimensional problems, enjoy local convergence properties and confer a geometric basis to recent contributions on learning fixed-rank matrices. We thereby show that the considered geometric optimization framework offers a solid and versatile framework for the design of rank-constrained machine learning algorithms. The efficiency of the proposed algorithms is illustrated on several machine learning applications. Numerical experiments suggest that the proposed algorithms compete favorably with the state-of-the-art in terms of achieved performance and required computational time. [less ▲]

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See detailMultidisciplinary study of trophic diversity and functional role of amphipod crustaceans associated to Posidonia oceanica meadows
Michel, Loïc ULg

Doctoral thesis (2011)

Posidonia oceanica is the most abundant seagrass of the Mediterranean Sea. It can cover extensive areas with monospecific formations, called meadows. These meadows, whose extent is estimated to about 40 ... [more ▼]

Posidonia oceanica is the most abundant seagrass of the Mediterranean Sea. It can cover extensive areas with monospecific formations, called meadows. These meadows, whose extent is estimated to about 40,000 km2, are critical features of the Mediterranean coastal zones. Moreover, they shelter important biomass and biodiversity of vagile invertebrates. Among these invertebrates, amphipod crustaceans are, alongside gastropod mollusks and polychaete annelids, one of the dominant groups. Amphipods are key-features of other temperate seagrass systems. As they are generally primary consumers, they are important in the transfers of organic matter from producers to higher rank consumers. In addition, their grazing activity on the epiphytes that grow on the seagrasses influence the dynamics of the epiphytic cover, and therefore the functioning of the whole meadow as an ecosystem. However, the situation in Mediterranean Posidonia oceanica meadows is still unclear. In particular, several lacks of information limit the comprehension of actual trophic ecology of amphipods, and of the impact of their feeding activity on the meadow functioning. In this context, the main goal of this work was to enhance the knowledge of the trophic diversity and the functional role of amphipods associated to Posidonia oceanica meadows. To achieve this, we structured our research in three main tasks. For each of these tasks, we chose Calvi Bay (NW Corsica, France) as study site, and all sampling and experimentation was undertaken from the STARESO research station (University of Liège). The first task (chapter 3) was the study of the precise composition of the amphipod community structure at our study site, and its temporal variation at day/night and seasonal scale. Our results show that the fauna of Posidonia oceanica meadows of Calvi Bay is abundant and diverse. The density and the structure of the community were different in each season (November, March and June), probably in relation with meadow parameters such as foliar surface, epiphytic biomass and abundance of litter in the meadow. Moreover, day/night variations were very important. Most amphipods performed vertical migrations that could be a mechanism to avoid predation and/or competition for food and habitat. The comparison of three sampling techniques (hand-towed net, litter collection and light traps) yielded deeply different results, suggesting that each of them only collects a subset of a complex assemblage. Combination of several sampling methods is therefore advised to have a holistic and accurate view of the community. These faunistic data also allowed highlighting the most abundant and/or representative species of the studied community. These include Apherusa chiereghinii, Aora spinicornis, Dexamine spiniventris, Amphithoe helleri, Caprella acanthifera, Gammarella fucicola and Gammarus aequicauda. These species were therefore chosen as target species for the second task. The second task (chapter 4) was the assessment of the extent of interspecific trophic diversity among the studied community. This phenomenon could indeed be important to limit food competition. We tried to perform a full reconstruction of the diet of the dominant species of the community and to evaluate the contribution of each of the potential food items offered by the meadow (animal and vegetal epiphytes from the leaves, rhizomes and litter fragments, SPOM, BPOM, living and dead P. oceanica material). To have an accurate view of the dietary habits of the dominant species, we used a triple strategy based on the joint use of traditional methods (gut content examination) and trophic markers (stable isotopes of C & N, fatty acids). The combination of these three methods proved to be successful, as each method had specific strengths and weaknesses. Overall, results indicate that all dominant species relied on macroalgal epiphytes for a large part of their diet. Our insights were unfortunately limited by the poor discrimination between potential food items, due to high inter-source similarity. Considerable interspecific differences could nonetheless be highlighted, notably concerning preferences of epiphytes from leaves or litter fragments vs. epiphytes from rhizomes. In addition, most species had a mixed diet, and relied on several food items. None of the examined species seemed to graze on their seagrass host, but Gammarus aequicauda partly relied on seagrass leaf detritus. Contribution of microepiphytes (e.g. diatoms) to the diet of amphipods was apparently anecdotical. Our data also suggested the existence of a certain extent of intraspecific trophic diversity that should be taken into account for future work. In the third and final task (chapter 5), we aimed to put the data obtained in the first two parts of this study in the wider context of the functioning of the Posidonia oceanica meadow as an ecosystem. We used in vitro and in situ microcosms experiments to characterize the interaction between epiphytes and amphipods from a triple point of view (resource depletion, resource assimilation by the consumer and secondary production), and to understand how amphipod grazing could influence the dynamics of the epiphytic cover of the leaves of P. oceanica. Amphipod grazing had no effect on the total epiphytic biomass, or on the encrusting epiphytes’ biomass. However, all three taxa (A. chiereghinii, D. spiniventris and Gammarus spp.) consumed significant amounts (45 to 90 % of total biomass) of erected epiphytes, both vegetal and animal. This selective top-down control might influence the structure and biomass-specific productivity rates of the epiphytic cover. In addition, amphipod grazing caused an increase in N availability and residence time. Through epiphyte removal and N enrichment, amphipods could boost seagrass production. Overall, amphipods of Posidonia oceanica meadows could be seen as ecosystem engineers. Assimilation of the consumed epiphytes was clear for all taxa. However, the utilization of this biomass for secondary production was hard to measure, due to low survival rates of animals. In fine, by combining in situ sampling and microcosm experimentation, and trough the joint use of traditional and innovative techniques, we showed that feeding activity of amphipods influence their biotope through several effects, and that they could be pivotal items of Posidonia oceanica meadows. In doing so, we improved, to some extent, the understanding of these critically important, yet endangered ecosystems. [less ▲]

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See detailToxicocinétique du sélénium chez les tortues. Exposition in vivo chez Trachemys scripta scripta
Dyc, Christelle ULg

Master's dissertation (2011)

Le sélénium est un élément essentiel possédant un seuil « carence-excès » très étroit. L’étude toxicocinétique de cet élément, constitue une étape préliminaire importante à la compréhension des effets ... [more ▼]

Le sélénium est un élément essentiel possédant un seuil « carence-excès » très étroit. L’étude toxicocinétique de cet élément, constitue une étape préliminaire importante à la compréhension des effets néfastes qu’il est susceptible de causer chez les populations de reptiles. Une expérimentation impliquant 130 tortues de Floride juvéniles (Trachemys scripta scripta) a été réalisée. Le groupe contrôle a été alimenté avec une nourriture de base, alors que les deux conditions expérimentales ont reçu une nourriture supplémentée avec 64 µg/g et 134 µg/g de séléno-L-méthionine (PS), pendant huit semaines. L’accumulation du Se a été mesurée dans le foie, les reins, le muscle, la peau, les écailles, la carapace et le sang, ce qui a permis d’observer que le transfert trophique du sélénium se réalisait de manière dose-dépendante. Durant quatre semaines supplémentaires, une cinétique d’élimination du Se a également pu être observée. De plus, la concentration en Se dans le sang, dans la carapace et dans la peau est apparue fortement corrélée à celle des tissus internes. Cette observation semble intéressante pour la mise en place d’un biomonitoring peu invasif des tortues dans leur milieu naturel. Les concentrations toxiques auxquelles les tortues ont été soumises n’ont pas permis de détecter d’effets néfastes au niveau de la croissance, de la prise alimentaire et de la survie des tortues. [less ▲]

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See detailResidency Patterns, Abundance and Social Composition of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina
Vermeulen, Els ULg

Master of advanced studies dissertation (2011)

Residency patterns, abundance and social composition of bottlenose dolphins (Tursiops truncatus) were assessed during 2008-2010 in Bahía San Antonio (BSA), Patagonia, Argentina. A total of 462.3 survey ... [more ▼]

Residency patterns, abundance and social composition of bottlenose dolphins (Tursiops truncatus) were assessed during 2008-2010 in Bahía San Antonio (BSA), Patagonia, Argentina. A total of 462.3 survey hours resulted in 80.7 contact hours with in total 107 dolphin groups. Data indicated that dolphins spend most of their time resting, feeding and travelling in BSA, although their time-budget changed over the different seasons. As such, dolphins increased their time feeding and socializing during winter and spring, whereas during summer they spent up to 46% of their time diving, a behaviour presumably associated with a tail out/peduncle-dive foraging strategy. Dolphin groups had a median size of 4 individuals ranging between 1 and 40. Group size seemed to vary significantly over the different seasons and behaviours, with groups being larger during winter and during socializing and feeding. Group size was further positively correlated with the presence of calves. A total of 63 dolphins were individually identified in the bay and re-identified up to 35 days. Of these, 57% could be regarded as resident in the area (year-long or seasonally), including all mother and calf pairs. Using the closed time heterogeneity model (Mth), and accounting for the proportion of unidentifiable individuals, calculations resulted in a maximum corrected abundance estimate of 97 and 83 individuals during winter, and a minimum abundance of 34 and 38 individuals during autumn of 2009 and 2010 respectively. At all times, between 25% and 68% of the population consisted out of unidentifiable individuals (juveniles and calves) depending on the season. Results further revealed that bottlenose dolphins in BSA associated at random and that the entire community existed out of two levels of casual acquaintances. Data presented herein suggest that the shallow and protected waters of BSA support a resident community of bottlenose dolphins, between 35 to 97 individuals depending on the season, living in a fission-fusion society in which companionships frequently change. It was further suggested that dolphins specifically use BSA to rest and feed, and that the region is preferred by females to give birth and raise their young, with a possible increased calving period during winter and spring based on an increasing prey availability. [less ▲]

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See detailDéveloppement d’approches complémentaires pour limiter la transmission virale par les pucerons dans la Province du Shandong
Bosquée, Emilie ULg

Master's dissertation (2011)

Nowadays, in China, the control of aphids lies on the systematic use of synthetic insecticides. A socio-economical analysis of rural households’ structure in the Shandong province was carried out. The ... [more ▼]

Nowadays, in China, the control of aphids lies on the systematic use of synthetic insecticides. A socio-economical analysis of rural households’ structure in the Shandong province was carried out. The latter highlighted the farmers’ unawareness of the chemicals’ harmful effects on the environment and on human health. This observation led to some research aiming at the development of new alternative methods that would be efficient for Chinese producers. Within this context of biological control against aphids and their virus transmission (Potato virus Y (PVY), Cucumber mosaic virus (CMV) et Potato Leaf Roll Virus (PLRV)), three semiochemical substances namely (E)-β-farnesene (EBF), cis-3-hexenyl acetate, garlic extract and peas intercropping were separately tested. Yellow traps were used and the treatments were applied on potatoes and courgettes fields. No significant difference is observed between the different treatments. However, a tendency for cultural association is showed. Another kind of biological control was envisaged: the use of lectins. In this study, the effects of three glycoproteins on the virus transmission of three non-persistant viruses were tested in laboratory on Myzus persicae via the use of artificial diets. The glycoproteins used were Canavalia ensiformis agglutinin (ConA), Galanthus nivalis agglutinin (GNA) and wheat germ agglutinin (WGA) as for the viruses; PVY, CMV and TuMV (Turnip Mosaic Virus). An interference between GNA and all viruses was observed. In addition, a competition between WGA and two viruses i.e. CMV and TuMV was highlighted. In consequence, the two latter lectins are considered as promising proteins. In order to share the results of this study with Chinese farmers, simplified technical specifications on the insect fauna of vegetable crops grown previously, the hazard of pesticides and on the tested alternative methods of control were written and distributed. [less ▲]

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See detailCaractérisation hydrogéologique du bassin du Lilot
Briers, Pierre ULg

Master's dissertation (2011)

Le Lilot, ruisseau de la région de Marchin (province de Liège) s’écoule majoritairement sur des formations givetiennes karstifiées. Ce contexte laisse supposer une forte vulnérabilité de l’aquifère ... [more ▼]

Le Lilot, ruisseau de la région de Marchin (province de Liège) s’écoule majoritairement sur des formations givetiennes karstifiées. Ce contexte laisse supposer une forte vulnérabilité de l’aquifère. Cependant, cette vulnérabilité n’est pas avérée car il faut encore qu’un volume suffisant de polluant s’infiltre et que le taux de renouvellement de l’aquifère ne puisse diluer cette contamination. De plus, rien n’indique que les eaux qui s’infiltrent au niveau des pertes rejoignent la nappe aquifère. L’objectif de ce travail est d’effectuer une caractérisation hydrogéologique du bassin et d’étudier les interactions entre les eaux de surface et les eaux souterraines. Cela a été réalisé à l’aide de divers outil tels qu’une étude du cycle hydrologique et un calcul de bilan, des profils débimétriques et physicochimiques du cours d’eau et un essai de traçage. [less ▲]

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See detailComparaison histologique et comportementale de différentes souches de souris après un épisode d’ischémie cérébrale
Fassotte, Ludivine ULg

Master's dissertation (2011)

L’ischémie cérébrale, qui correspond à une interruption du flux sanguin causée par l’obstruction d’une artère cérébrale, est occasionnée dans plus de 80% des AVCs humains. Cette maladie neurologique est ... [more ▼]

L’ischémie cérébrale, qui correspond à une interruption du flux sanguin causée par l’obstruction d’une artère cérébrale, est occasionnée dans plus de 80% des AVCs humains. Cette maladie neurologique est la seconde cause de mortalité dans les sociétés industrialisées et son impact est lourd sur les survivants. En effet, elle génère des déficits fonctionnels subsistant pendant des mois, voire des années. Ce travail s’inscrit dans la perspective de développement d’un traitement permettant une récupération fonctionnelle de ces déficits par la recherche de techniques permettant de mimer un AVC humain sur différentes souches de rongeurs. Le présent travail consiste en la mise en place d’une batterie de tests comportementaux permettant l’évaluation à court et à long terme des déficits sensorimoteurs, comportementaux et cognitifs causés par une ischémie cérébrale expérimentale de 30 minutes induite par la technique d’occlusion de l’artère cérébrale moyenne (MCAo) à droite. Dans cette perspective, deux souches murines couramment utilisées en laboratoire, 129S2/SvPas et C57Black6J ont été comparées. Une semaine puis trois semaines après l’opération, les capacités sensorimotrices des animaux sont évaluées à l’aide du rotarod, du pole test, du test d’agrippement tandis que l’activité locomotrice et l’anxiété sont mesurées dans un open field. Après un mois, l’endurance et la motivation sont testées par un programme de FR progressif alors que la flexibilité cognitive est évaluée à l’aide du programme du reversal learning. Au terme de l’évaluation comportementale, le cerveau des animaux est prélevé et l’étendue de la lésion cérébrale est évaluée à l’aide d’une révélation immunohistochimique utilisant le marquage anti-neuronal NeuN. Les résultats témoignent d’un effet significatif de l’ischémie chez la souche C57 sur les capacités sensorimotrices des animaux (rotarod et locomotion). Les résultats au FR progressif montrent qu’une ischémie de 30 minutes altère l’endurance des animaux lorsque le nombre d’appuis demandé est élevé. De même, un trouble des fonctions exécutives est également observé (passage d’un comportement à un autre). La lésion occasionnée par l’ischémie touche le striatum dorsolatéral chez les deux souches ainsi qu’une portion plus moins étendue du cortex cérébral dans le cas de la souche C57. L’étendue plus ou moins importante de la lésion est liée à l’anatomie vasculaire cérébrale qui est variable d’une souche à l’autre. Puisque le cortex moteur n’est pas affecté, les troubles observés sont probablement liés à la lésion du striatum, une portion du cerveau qui est étroitement connectée avec le cortex moteur. A l’issue de ces expériences, l’utilisation de la souche C57 semble être plus appropriée à l’étude de l’ischémie cérébrale transitoire chez la souris que la souche 129S2. Le présent travail montre que l’établissement d’une batterie de tests comportementaux sensibles à l’ischémie doit comporter à la fois des tests sensorimoteurs afin de déceler des troubles transitoires tels que la coordination motrice et l’endurance. Une telle batterie doit également comporter des tests cognitifs détectant des déficits subsistant à long terme tels que les troubles de la fonction exécutive. La sélection d’un modèle animal le plus approprié ainsi que la mise en place d’une telle batterie de tests permettront idéalement de corréler les déficits observés et les structures nerveuses impliquées dans les fonctions touchées par l’ischémie cérébrale. Dès que ces bases auront été posées, de nouveaux traitements appropriés pourront alors être testés. [less ▲]

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See detailModélisation d'évènements rares à l'aide de distributions non normales : application en finance avec la fonction sinh-arcsinh
Hambuckers, julien ULg

Master's dissertation (2011)

In 2008, the financial crisis put forward the relative inaccuracy of the market risk forecasting models in the financial industry. In particular, extreme events were shown to be regularly underestimated ... [more ▼]

In 2008, the financial crisis put forward the relative inaccuracy of the market risk forecasting models in the financial industry. In particular, extreme events were shown to be regularly underestimated. This problematic, initially developed in the seminal work of Mandelbrot (1963), is mainly due to financial models using the normal law while empirical evidence show strong leptokurticity in financial time series. This stylized effect is particularly damaging the forecasting of indicators like Value-at-Risk (VAR). In this study, we try to tackle problem by testing a newly-developed probability distribution, never used in finance: sinh-arcsinh function. By creating different datasets from non-parametric and GARCH models, we adjust common functions (normal, t location-scale, GED, gen. hyperbolic) and sinh-arcsinh function on the data. We show that, regarding the leptokurtic datasets extracted from the DJA and the NIKKEI 225, the sinh-arcsinh function performs a better adjustment than any other function tested. We also tested simple VAR models using normal laws, Student’s t or sinh-arcsinh functions, to assess the operational efficiency of the sinh-arcsinh function. We show that models using sinh-arcsinh functions provide more accurate and better in-sample and out-of-sample VAR forecasts than any other model using the normal laws. [less ▲]

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See detailArticle de régulation
Scheffers, Patricia ULg

Master's dissertation (2011)

Les outils pédagogiques (*) mis en place dans le cadre du cours d'atelier de projet d'architecture de 3e Bachelier sont-ils de nature à favoriser l’autonomisation de l'étudiant et à en rendre compte dans ... [more ▼]

Les outils pédagogiques (*) mis en place dans le cadre du cours d'atelier de projet d'architecture de 3e Bachelier sont-ils de nature à favoriser l’autonomisation de l'étudiant et à en rendre compte dans le cadre du développement de la compétence visée ? (*) Abstract, journal de bord, fiches d'auto-évaluation, plannings [less ▲]

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See detailEtude protéomique de l'incidence d'une hypertriglycéridémie sur le métabolisme hépatique de la souris
Ehx, Grégory ULg

Master's dissertation (2011)

L’hypertriglycéridémie est une pathologie largement répandue chez l’homme sédentarisé. Elle se définit comme un taux plasmatique de triglycérides (TAG) anormalement élevé (supérieur à 200 mg/dl). La ... [more ▼]

L’hypertriglycéridémie est une pathologie largement répandue chez l’homme sédentarisé. Elle se définit comme un taux plasmatique de triglycérides (TAG) anormalement élevé (supérieur à 200 mg/dl). La souris transgénique HuApoC-III est un animal modèle idéal pour l’étude de l’hypertriglycéridémie indépendamment des effets confondants qui y sont généralement associés (en particulier l’obésité et la résistance à l’insuline). En effet, elles sont hypertriglycéridémiques mais ne sont ni obèses ni résistantes à l’insuline. Dans la continuité d’une étude des adaptations mitoprotéomiques hépatique à une hypertriglycéridémie sévère (taux de TAG supérieur à 500 mg/dl) récemment menée par notre laboratoire, nous avons caractérisé par une technique de protéomique comparative, le 2DDIGE, les adaptations protéomiques de la membrane interne mitochondriale et du protéome cellulaire à ce même type d’hypertriglycéridémie, chez la souris HuApoC-III. Comme prédit lors de notre étude antérieure, le protéome de la membrane interne s’est avéré ne présenter aucune modification de sa composition entre les souris HuApoC-III et sauvages. Comme il a été rapporté que les souris HuApoC-III présentent une vitesse de respiration mitochondriale à l’état III sur succinate similaire à celle des souris sauvages, cette invariance de la composition protéique de la membrane interne pourrait refléter des altérations de sa composition lipidique ou de sa structure. L’analyse du protéome cellulaire total a permis de confirmer l’augmentation de la capacité du catabolisme des acides aminés et de la glycolyse suggérée par nos résultats antérieurs. Cette augmentation, accompagnée de l’augmentation de la capacité de la β- oxydation également décrite antérieurement, permettrait d’augmenter le taux de production d’acétyl-CoA, de glycérol-3-phosphate et d’ATP fin de supporter la production élevée de TAG des hépatocytes des souris HuApoC-III. Cette analyse a par ailleurs révélé que les hépatocytes des souris HuApoC-III présentent un stress oxydatif cytoplasmique, une probable accumulation de fer intracytoplasmique et une prolifération accrue. Ce stress oxydatif pouvant induire des lésions cellulaires et tissulaires ainsi que l’inflammation du foie, nous proposons que les souris HuApoC-III présentent une fibrose hépatique. [less ▲]

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See detailL’impact de la mobilité internationale sur le projet de carrière et la construction de l’identité professionnelle des cadres internationaux à la lumière des ancres de carrière et des typologies identitaires : Analyse comparative des motivations personnelles et professionnelles des cadres en mobilité internationale
Gérard, Julie ULg

Master's dissertation (2011)

Fondée sur une recherche empirique menée auprès de trente-trois cadres en situation de mobilité internationale, cette étude analyse l’impact de la mobilité internationale sur le projet de carrière et la ... [more ▼]

Fondée sur une recherche empirique menée auprès de trente-trois cadres en situation de mobilité internationale, cette étude analyse l’impact de la mobilité internationale sur le projet de carrière et la construction de l’identité professionnelle des cadres internationaux, en s’appuyant sur la théorie des ancres de carrière de Schein (1978, 1990) et la théorie des stratégies identitaires de Pierre (2003). Sur la base du récit de vie de ces trente-trois cadres, nous avons étudié leurs motivations personnelles et professionnelles afin de dresser une typologie nuancée et circonstanciée de leur stratégie d’identification. [less ▲]

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See detailContribution to the study on sound production in clownfishes (Perciformes, Pomacentridae): a multidisciplinary approach
Colleye, Orphal ULg

Doctoral thesis (2011)

Clownfishes (Amphiprion spp.) are brightly colored fishes that are members of the Pomacentridae family. They are well known for their mutualistic relationship with tropical sea anemones. These fishes live ... [more ▼]

Clownfishes (Amphiprion spp.) are brightly colored fishes that are members of the Pomacentridae family. They are well known for their mutualistic relationship with tropical sea anemones. These fishes live in social groups in which there is a size-based dominance hierarchy. In this structure where sex is socially controlled, agonistic interactions are numerous and serve to maintain size differences between individuals adjacent in rank. Several studies have reported that vocalizations are associated with agonistic interactions but precise data are lacking and further investigations are needed. The nature of the sound-producing mechanisms also remained unresolved, only resting on few assumptions. Thereby, the main aim of the present thesis is (1) to determine the fundamental components of the acoustic communication in clownfishes, and (2) to explain the mechanisms of sound production. In order to achieve these objectives, the research has been divided into three different axes. Firstly, the study of the acoustic behaviors shows that no acoustic signal is associated with reproductive activities in clownfishes. Sound recordings during agonistic interactions indicate that these fishes produce two types of sounds. Aggressive sounds are produced during chases and threat displays while submissive (or head shaking) sounds are emitted in reaction to aggressive acts by dominant. Both types of sounds show size-related intraspecific differences in dominant frequency and pulse duration: smaller individuals produce higher frequency and shorter duration pulses than larger individuals, and inversely. Consequently, these sonic features might be useful cues for individual recognition and maintenance of cohesion within the group. Secondly, the study of the sound-producing mechanism highlights that aggressive sounds are initiated by buccal jaw teeth snapping caused by rapid mouth closure attributed to a sonic ligament. It appears that the swimbladder does not function as a resonator that amplifies and changes the quality of sounds. This structure is a highly damped sound source prevented from prolonged resonant vibrations. On the other hand, the rib cage might be the major acoustic radiator and its resonant properties might explain the size-related variations observed in pulse duration and dominant frequency. Thirdly, the comparison of aggressive sounds among fourteen clownfish species indicates that the same relationship between fish size and both dominant frequency and pulse duration is spread over the entire group (i.e. tribe Amphiprionini). These results highlight all species use a highly conservative mechanism of vocalization. Pulse period appears to be the most variable acoustic feature and could be involved in species-specific recognition, as well as pulse duration and dominant frequency in a lesser extent through their relationship with body size. Although sound production appears to be restricted to some agonistic behaviors, these sounds seem to constitute an integral part of the peculiar way of life of clownfishes. The aggressive and submissive sounds would also result from two different mechanisms.   [less ▲]

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See detailREGULATION DE L'EXPRESSION ET DE LA REPLICATION DU VIRUS T-LYMPHOTROPE HUMAIN DE TYPE I (HTLV-1) PAR LE COMPLEXE MINICHROMOSOME MAINTENANCE 2-7 (MCM2-7)
Barez, Pierre-Yves ULg

Master's dissertation (2011)

First human retrovirus discovered, HTLV-1 infects approximately 20 million individuals worldwide. HTLV-1 is the etiological agent of adult T-cell leukemia and a neurodegenerative disorder called HAM/TSP ... [more ▼]

First human retrovirus discovered, HTLV-1 infects approximately 20 million individuals worldwide. HTLV-1 is the etiological agent of adult T-cell leukemia and a neurodegenerative disorder called HAM/TSP (HTLV-1 associated myelopathy/Tropical spastic paraparesis). The MCM2-7 complex seems to play a key role in the biology of viruses, such as EBV (Epstein-Barr virus), KSHV (Kaposi’s sarcoma associated virus) or Influenza. This is also the case for HTLV-1 virus because we revealed the recruitment of MCM2-7 onto the viral promoter. The role of this interaction does not pertain to viral replication but is involved in transcriptional regulation. In fact, overexpression of MCM3 increases Tax transactivation activity dependently on Tax/MCM3 interaction and MCM3 carboxy-terminal domain. Finally, our observations indicate that MCM3 is likely required for Tax nuclear shuttling. This work thus gives insights into new mechanisms by which Tax ensures the viral persistence and leads to the development of HTLV-1 associated diseases. [less ▲]

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See detailRôles des hydrocarbures dans le comportement agrégatif de la coccinelle asiatique, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae)
Fassotte, Bérénice ULg

Master's dissertation (2011)

In order to protect themselves against cold and to survive through the winter, the Asian ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) forms large aggregates inside dwellings to ... [more ▼]

In order to protect themselves against cold and to survive through the winter, the Asian ladybeetle Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) forms large aggregates inside dwellings to overwinter. In this work, the implication of hydrocarbons on the aggregative behaviour of this invasive species has been examined to understand the mechanisms involved in this particular phenomenon. The evolution of non-volatile compounds, proved to be used by H. axyridis in this phenomenon, on one hand to guide individuals to the aggregate ("trail") and on the other hand, to ensure the cohesion of the cluster ("aggregation blend"), has been studied by performing chromatographic analyses and behavioural tests. The results show that the composition of the trail deposited by individuals, and its biological activity on ladybirds, change over months. However, the change in ladybirds’ response towards these trails is not due to a modification of blend attractiveness but well to a change in the physiological state of ladybugs. Furthermore, the effect of photoperiod on the induction of that hivernation state was tested. It was highlighted that only a short photoperiod could not be responsible for the aggregation state of H. axyridis. Then, the maturing process of the aggregation blend was studied, demonstrating that saturated hydrocarbons were more persistent and suggesting their use by ladybirds to join the same aggregation sites year after year. Moreover, it turned out that cuticular hydrocarbons, as well as thigmotaxis, play a role in the aggregation behaviour of H. axyridis. However, this second factor is involved to a lesser extent. [less ▲]

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See detailContribution à la conservation de la flore cupro-cobalticole endémique du Katanga (R.D.C.) : Conservation en banque de graines et régénération d'espèces métallicoles
Boisson, Sylvain ULg

Master's dissertation (2011)

Metallophytes are plants that represent the biodiversity of metal-rich soils. Some of them are able to accumulate high metal concentrations: metal hyperaccumulators plants. In Katanga (RD Congo), 32 ... [more ▼]

Metallophytes are plants that represent the biodiversity of metal-rich soils. Some of them are able to accumulate high metal concentrations: metal hyperaccumulators plants. In Katanga (RD Congo), 32 species have been identified as copper-cobalt endemic but mining activities are still a threat to outcrop ecosystems. We must characterize native environmental parameters (realized niche) and the full range of environmental conditions in culture (fundamental niche) to conserve, preserve and restore these ecosystems. Six representative species of the natural copper gradient were selected after soil-species data analyses (Crepidorhopalon perennis, Crotalaria cobalticola, Gladiolus ledoctei, Haumaniastrum robertii, Lopholaena deltombei and Sopubia mannii). The study determined their behavior (germination, survival) and their development (vegetative measures) on one group of natural soil (from three copper gradients of Fungurume V hill), two groups of artificially contaminated soils with incremental doses (copper sulfate and copper hydroxycarbonate: 500, 2000 and 5000 mg.kg-1) and one uncontaminated soil (control) by two types of plant establishment (direct seeding and transplant from Petri dishes). The results depend on species habitat and show that four of these species can grow on uncontaminated soil in the early stages of growth. In addition, the seed bank (in Faculty of Agronomy - University of Lubumbashi) management (cleaning, updating and germination tests of accessions) was maintained using standard methods. The results of germination tests demonstrated the effectiveness of some conservation methods and helped to provide recommendations for the methodology. [less ▲]

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See detailMise en place de différentes stratégies visant à favoriser l’approche « push-pull » pour le contrôle des pucerons en cultures maraîchères dans l’est de la Chine
Chevalier Mendes Lopes, Thomas ULg

Master's dissertation (2011)

The Chinese farmers apply a lot of pesticides in their vegetable crops. This situation, due to the socio-economic context of the rural population of the country, affects the food security. This work aims ... [more ▼]

The Chinese farmers apply a lot of pesticides in their vegetable crops. This situation, due to the socio-economic context of the rural population of the country, affects the food security. This work aims to study alternatives to the intensive use of synthetic pesticides, namely by the establishment of “push-pull” strategies, in courgettes and potato fields. We used three semiochemicals, the (E)-β-farnésène, the (Z)-3-Hexenyl acetate and a garlic extract and intercropping with pea. The effect of these treatments in the populations of aphidiphagous beneficial insects was determined by five weeks of insect trapping and observations on the plants. The results indicate that none of the modalities has a significant effect on the populations of beneficial insects and aphids. However, we observed some trends, especially with the (E)-β-farnésène in the courgettes fields. In addition, information sheets were made to inform and raise awareness of the Chinese farmers about the use of pesticides and the role of beneficial insects in the control of aphid populations. [less ▲]

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See detailLa place de l'identité dans la politique étrangère. Le cas de la Turquie dans la période de pos-11 septembre 2001
Arslan, Nevzat ULg

Doctoral thesis (2011)

Il est question, dans ce travail, de découvrir les variables qui jouent un rôle dans l'orientation et dans la détermination de la politique étrangère turque. Il s'agit donc de s'intéresser aux variables ... [more ▼]

Il est question, dans ce travail, de découvrir les variables qui jouent un rôle dans l'orientation et dans la détermination de la politique étrangère turque. Il s'agit donc de s'intéresser aux variables causales découlant de la politique intérieure de la Turquie. Ainsi est évaluée l'importance des variables individuelles, institutionnelles, gouvernementales et systémiques dans la détermination des idées et des intérêts défendus par les différents acteurs internes. Adoptant une approche constructiviste des relations internationales, cette étude consiste, d'une part, en une description de l'identité nationale de l'État turc et de l'autre en une explication de la redéfinition de cette identité par une nouvelle idéologie, défendue par une nouvelle classe dirigeante. Nous nous sommes penchés sur les valeurs et les identités nationales qui ont contribué à façonner les conceptions et les priorités de la politique étrangère turque. Ainsi, l'approche théorique choisie doit tenir compte de ces divers facteurs, qui exercent une influence sur la formulation des intérêts nationaux. [less ▲]

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See detailContribution à la recherche et à l’étude d’améliorants de panification
Dubrowski, Thomas ULg

Master's dissertation (2011)

This work takes place in the current trend aiming to find new substances that, once added to the formulation of bread, improve its characteristics. To do this, a homologous series of three emulsifiers ... [more ▼]

This work takes place in the current trend aiming to find new substances that, once added to the formulation of bread, improve its characteristics. To do this, a homologous series of three emulsifiers, synthesized from glucuronic acid on which were grafted hydrocarbon chains of different lengths (from 14 to 18 carbon atoms), was obtained by glycosylation. The purification of these three surfactants is also described as feasible, with an almost complete separation of the two anomers obtained through this synthesis. Then these three synthesized products were applied to bakery by conducting laboratory tests (farinograph, alveograph) followed by micropanification tests in real conditions. In order to compare their results, two commercial references (DATEM and SSL) have also been used. It appears that none of the alkyl glucuronolactone possesses a “dough strengthener” effect while a “crumb softener” effect was noted (P < 0.05) for GlcA-O-C14 and -C16 in comparison with the “control”, with in the latter case, a greater decrease of firmness than with SSL, already popular for its action. The role of these molecules on staling was also analyzed and it seems that they slow down the hardening of bread after 27 h (P < 0.05) more than the commercial references, whereas after 48 h, only GlcA-O-C18 retains an advantage against the formulation without any emulsifier, even if it is no longer significant. [less ▲]

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See detailDa Alessandro ai Theoi Adelphoi. Fondazione e legittimazione della dinastia tolemaica, tra IV e III secolo a.C.
Caneva, Stefano ULg

Doctoral thesis (2011)

The research focuses on the first century of the Macedonian rule over Egypt in order to study how the Ptolemies had their power legitimated in Africa and in the broader Mediterranean context. Literary ... [more ▼]

The research focuses on the first century of the Macedonian rule over Egypt in order to study how the Ptolemies had their power legitimated in Africa and in the broader Mediterranean context. Literary sources (both prose and verse, in Greek and Egyptian language), inscriptions, papyri, and iconography are used to set an interdisciplinary approach to the topic. Major attention is paid to the social contexts where ideological motifs originate and spread; to the link between media, genres and consensus making; to the genealogy and development of specific legitimating themes and their later incorporation in learned traditions or local identities. Section I: From Alexander to the Ptolemies. Chapter I: Alexander in Egypt: focus is on the role of Siwah in the perspective of the Greek, Macedonian, and Egyptian legitimation of Alexander's power in Egypt; particular attention is paid to how legitimating traditions are used and reshaped to the purposes of broadening the limits of Macedonian kingship, depicting Alexander as a Greek hero, interpreting Egyptian kingship for Greeks and Macedonians and naturalizing Alexander as a Pharaoh. Chapter II: In the name of Alexander: how Ptolemy adapted to the hierarchy of proximity to the king to legitimate his power in Egypt and finally to establish a new dinasty; main topics are the use of Alexander's body in the historical context of the succession and in the local tradition of Alexandria; the historical events of the last decades of IV century are considered from the perspective of the development of legitimating themes, such as the political allegiance to Alexander, the right of conquest, the use of marriage diplomacy. Section II: The Political Use of Religious Festivals under Ptolemy II. Chapter III: Sources and Historical Problems concerning the Ptolemaia: sources on the Ptolemaia, Pentaeteris and Callixeinus' report in Athen. V are discussed to study dynastic festivals during Ptolemy II’s reing. Chapter IV: Anatomy of a Festival: The Grand Procession of Ptolemy II: focus is on the making of an historical and mythic legitimating past through the scenes in the procession. Section III: Patterns of Female Power: The Case of Arsinoe II Chapter V: Shaping Female Power: Arsinoe II as a Queen: Arsinoe II's career and political legacy are discussed to offer a gender-related evaluation of her role as a queen in both Greco-Macedonian and Egyptian traditions. Chapter VI: Female Ruler Cults. Arsinoe in Early Hellenistic Context: the analysis combines court poetry, iconography and documentary texts to study the cults for Arsinoe both as a member of the Theoi Adelphoi and as an individual goddess, the Philadelphos. Arsinoe's case is then discussed in the broader perspective of female ruler cults in early Hellenism. [less ▲]

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See detailCaracterización del producto cerámico en las comunidades neolíticas de mediados del V milenio Cal BC: El valle del Éufrates y el valle del Khabur en el Halaf final (Siria).
Gomez Bach, Ana Maria ULg

Doctoral thesis (2011)

The characterization of pottery production in the mid-sixt millennium cal BC in Neolithic communities: the Euphrates valley and Khabur basin in Late Halaf. SUMMARY The characterization of pottery ... [more ▼]

The characterization of pottery production in the mid-sixt millennium cal BC in Neolithic communities: the Euphrates valley and Khabur basin in Late Halaf. SUMMARY The characterization of pottery production in the mid-sixth millennium cal BC contexts in the Middle East arises from the need to understand how consolidated agricultural and pastoral communities of the Fertile Crescent were structured and organized. This chrono cultural period is embodied in an archaeological record of great interest in order to identify the different economic, social and symbolic responses at the final moment of the so-called Halaf culture. The opportunity to study the pottery assemblages from two sites and two regions, such as the Euphrates valley and the valley of Khabur, with new material from Tell Halula (16,668 sherds) and Chagar Bazar (21,194 sherds), allowed us to study and apply the same methodology to both sets from the very beginning of fieldwork. The analysis of 37,882 fragments from a comprehensive perspective and by using archaeometric techniques (chemical, petrographic and PIXE analysis) as well as morphometric and basic techno functional characterization analysis set new guidelines on the archaeological potential of these sets. Drawn up from Archaeology and Materials Science, this contribution has its methodological framework focused on rebuilding the chaîne operatoire. This reconstruction has allowed us to study and isolate two assemblages and to outline the existence of different socio economic practices, some of which had clear regional links and a strong substrate, but above all with basic subsistence practices which can be addressed from the ceramic product itself. Likewise, the specific chronological framework provided by new radiocarbon dates of both sites, which are between 5600-5300 cal BC, enables not only to characterise these productions but also to arise new questions to understand the interaction mechanisms between communities; mechanisms that cover from basic subsistence practices, i.e. the handling and processing of food and products, to mechanisms which regulate and structure the group. [less ▲]

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See detailDifférenciations sociospatiales et gouvernance municipale dans les banlieues de Beyrouth : à travers l'exemple de Sahel AlMatn AlJanoubi et des municipalités de Chiyah, Ghobeiri et Furn AlChebbak
Farah, Jihad ULg

Doctoral thesis (2011)

La thèse s’inscrit dans le débat sur une des “grandes questions urbaines contemporaines”: comment dans la multiplication des projets individuels et collectifs de plus en plus fragmentés se construit la ... [more ▼]

La thèse s’inscrit dans le débat sur une des “grandes questions urbaines contemporaines”: comment dans la multiplication des projets individuels et collectifs de plus en plus fragmentés se construit la ville d’aujourd’hui? Dans un contexte d’étalement urbain continu et de crise des “grands récits” de la modernité, l’individu comme le groupe connaît de plus en plus de difficultés à trouver sa place, son “lieu”, en ville. La recherche de l’entre-soi et l’altérité devient de plus en plus importante dans cette quête. La thèse revient sur les différents concepts traitant des différenciations sociospatiales en ville (ségrégation, marginalisation, relégation, fragmentation). Elle remarque que ces concepts favorisent une lecture systémique de la réalité urbaine où les éléments factoriels économiques, culturels et politiques ont un rôle central dans l’explication. Tout en se mettant dans la continuité de ces travaux, la thèse privilégie une lecture se basant sur trois entrées: - La crise de citoyenneté urbaine (crise de définitions de la ville, de ses limites, de ses citoyens, de leurs droits et surtout de sa gouvernance) comme principale grille explicative - Le local. Ce dernier étant d’une part l’échelle où ces différenciations sociospatiales sont les plus manifestes, et d’autre part car c’est à cette échelle que les phénomènes systémiques doivent se “redéfinir” en s’inscrivant dans le contexte. - Les périphéries et les banlieues où la cirse de citoyenneté est plus nette et où les acteurs locaux – dans un milieu à la recherche de sens, et en continuelle redéfinition – cherchent à avoir plus d’emprise sur leur milieu direct. Dans ce contexte la thèse avance que les spécificités du local, notamment la gouvernance locale et la spécialisation économique ont un poids déterminant dans la définition des dynamiques territoriales et par suite des différenciations sociospatiales. Cette hypothèse est déclinée en deux hypothèses opérationnelles: 1. - L’une s’inscrivant dans une perspective historique: Si incontestablement des dynamiques induites de la globalisation affectent les différenciations sociospatiales dans l’espace beyrouthin, nous pensons que l’héritage d’un temps long dans ses dimensions politiques et économiques pèse encore fortement sur ces différenciations dans les banlieues de Beyrouth. 2. L’autre dans une perspective politique: La stabilisation du régime municipal est aujourd’hui la rationalité qui domine l’action municipale. Elle est déterminante de la gouvernance locale dans chaque commune et par suite consubstantielle de l’évolution des différenciations sociospatiales dans ces banlieues. Les banlieues de Beyrouth, considérées comme cas révélateur, sont retenues pour comme terrain d’étude Deux méthodes d’analyse complémentaires sont mobilisées. L’une dite diachronique essaie de repérer les constantes et les variables dans l’histoire d’un district de ces banlieues comprenant les actuelles banlieues sud et sud-est, en insistant sur les rôles particuliers de la gouvernance et de l’économie. L’autre dite synchronique tente de souligner des liens entre des typologies de gouvernance urbaine différentes et leurs impacts en termes de différenciations sociospatiales en mobilisant le concept de régimes urbains. Les principales conclusions sont: - Des arrière-pays consolidés, avant l’étalement des villes centres, ayant leurs propres dynamiques: leur urbanisation, leurs économies et leurs gouvernances locale, leurs trajectoires propres connaissent très tôt la fragmentation urbaine (conclusion en porte-à-faux par rapport au corpus de la fragmentation soulignant le rôle fondateur de la globalisation) - L’architecture du régime urbain local et sa recherche de stabilité interne affectent fortement l’articulation de l’échelle d’action locale aux échelles d’action supérieures. Comme elles affectent certaines formes de dynamiques territoriales locales (notamment celles inscrites dans le registre de construction identitaire des territoires). Toutefois elles semblent avoir moins d’impact sur les aspects centralités et flux des dynamiques territoriales. - La fragmentation politique du territoire peut s’avérer une ressource importante pour les acteurs locaux pour négocier et s’approprier une place, un “lieu” dans les agglomérations urbaines d’aujourd’hui. D’autre part, devant la pression continue que connaissent les territoires urbains des périphéries pour se redéfinir et s’articuler à de nouvelles entités sociospatiales en formation, on peut observer dans certains cas de la véritable innovation en termes de politiques urbaines. Ces municipalités peuvent représenter, comme dans le cas de certaines dans les banlieues de Beyrouth, des laboratoires qui font émerger des nouveaux outils urbains qui pourront servir pour penser et gérer la ville à d’autres échelles. [less ▲]

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See detailDes loups dans la Cité. Eléments d'écologie pragmatiste
Doré, Antoine ULg

Doctoral thesis (2011)

Les politiques contemporaines sont marquées par des bouleversements écologiques qui interrogent la place à accorder à une liste toujours plus longue et hétérogène de prétendants à la vie publique. Cette ... [more ▼]

Les politiques contemporaines sont marquées par des bouleversements écologiques qui interrogent la place à accorder à une liste toujours plus longue et hétérogène de prétendants à la vie publique. Cette thèse propose un examen empirique d’une telle dynamique à partir du cas de la mise en politique des loups en France. En traçant les multiples manières dont les loups interpellent ceux et ce qui les entourent, en décrivant les agencements hybrides d’humains et de non-humains qu’ils forment et transforment sur leur passage et en prêtant attention aux différentes manières dont les acteurs affectés prennent en charge les situations générées par ces animaux, il s’agit d’identifier et de suivre, pas à pas, des portions importantes de quelques-unes des trajectoires qui composent la carrière politique des loups. Cette recherche montre alors comment des scientifiques, des juristes, des publics, des représentants de l’État, des journalistes, etc., mais aussi les loups eux-mêmes, composent ces trajectoires spécifiques marquées par des pratiques, des temporalités, des spatialités, des matérialités particulières. L’analyse révèle comment la présence publique des loups est instaurée par la science, le droit, l’État, etc. Elle rend compte également réciproquement de la manière dont la science, le droit, l’État, etc., s’inventent et se transforment à travers les loups. Cette thèse propose finalement un compte rendu synthétique et réaliste des modalités de construction d’une politique des loups et vise à éclairer deux questions plus générales : dans quel sens peut-on parler des implications politiques de la nature et en quoi cela nous invite-t-il à changer nos habitudes de description et d’aménagement de la vie ensemble ? [less ▲]

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See detailAnalyse comparative de différentes démarches de modélisation hydrologiques pour la représentation de la couverture forestière dans le bassin versant de la Houille (Contribution au projet INTERREG : P2IH)
Deraedt, Deborah ULg

Master's dissertation (2011)

The more simplistic models often overlook the representation of forest cover. Nevertheless it has a significant impact with water uptakes that follows a seasonal variation for example. The comparison of ... [more ▼]

The more simplistic models often overlook the representation of forest cover. Nevertheless it has a significant impact with water uptakes that follows a seasonal variation for example. The comparison of the two global models, PDM and GR4J, highlights the poor quality of simulation on the wooded watershed of the Houille (Belgium). In the case of PDM results are disappointing both in calibration and in validation. The Nash criteria are 0.65 and 0.52 respectively. Calibration of GR4J was a little more promising. But the validation has proved the weakness of the model to simulate the peaks coming from melting snow. The Nash coefficients go down from 0.81 to 0.65. We have tested the EPIC model with the plant parameters recommended for SWAT (which uses the same plant growth module) for spruce and oak. The parameters characterizing the soil are adjusted to the water content values obtained on two measurement sites. One is located in a spruce stand and the other in an oak stand. The comparison of the EPIC model simulation, as describes before, and in situ measurements shows an important difference in terms of water uptake. The model tends to overestimate trees water consumption. It proves the importance of using proper plant parameters to remain representative of the site dynamics and on larger scale, of the watershed dynamics. [less ▲]

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See detailClassification automatique d'images biologiques par variantes d'arbres de décision
Mathéi, Axel ULg

Master's dissertation (2011)

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See detailPrédiction de structures de macromolécules par apprentissage automatique
Marcos Alvarez, Alejandro ULg

Master's dissertation (2011)

Proteins are an essential constituent of cellular life whose biggest part of their function is determined by their tridimensional shape. Nowadays, however, no method is able to predict efficiently ... [more ▼]

Proteins are an essential constituent of cellular life whose biggest part of their function is determined by their tridimensional shape. Nowadays, however, no method is able to predict efficiently tridimensional protein structures based only on their amino acids sequence. We propose here an "ab initio" approach based on the concept of learning for search. Protein structure prediction is modeled in the form of an optimization problem solved by an optimization algorithm that follows an iterative framework in which a structure modification operator is selected and then applied to the current structure. The quality of the new structure is then assessed by an oracle that will determine whether or not the structure is accepted. The repetition of this framework will eventually lead to the sought structure. The critical point of this rationale lies in the choice of the modification operator, which has to be done very accurately in order to avoid the classical pitfalls of optimization problems. The operator selection step will then be subjected to machine learning thus legitimizing the term "learning for search" of the proposed method. The goal of this thesis is to show that machine learning can improve the results obtained via a simple optimization procedure. Our experiments show that this goal is fulfilled. We however know that many choices that we did should be questioned regarding both the optimization and the machine learning procedures. Finally, we can notice that the application domain of this work extends beyond the protein structure prediction problem. There exist indeed many optimization problems in the scientific literature for which no exact neither approximation algorithm exists and that are thus still very badly solved. Such problems could greatly benefit from a "learning for search" approach such as the one described in this work. [less ▲]

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See detailStockage géologique du CO2: l'étanchéité des puits
Dieudonné, Anne-Catherine ULg

Master's dissertation (2011)

Carbon capture and storage is an innovator approach to fight climate changes through the reduction of greenhouse gas emissions. Abandoned coal mines are currently less studied than other reservoirs but ... [more ▼]

Carbon capture and storage is an innovator approach to fight climate changes through the reduction of greenhouse gas emissions. Abandoned coal mines are currently less studied than other reservoirs but could also be used for the storage of carbon dioxide. However the problem of shaft sealing appears to be central as far as the safety, economic, ecologic and health stakes of geological storage are concerned. The purpose of the present work is the study of shaft sealing in the framework of CO2 storage projects. More precisely the problem consists in the numerical study, with the LAGAMINE finite elements code, of gas transfers around a shaft seal system. A coupled hydro-mechanical model of unsaturated geomaterials is presented. The response of the flow model is first studied through a simple synthetic problem simulating the injection of gas in a concrete-made column. It stands out of this first modeling that the advection of the gas phase represents the main transfer mechanism of CO2 in highly unsaturated materials. Furthermore the setting of a bentonite barrier seal allows limiting considerably gas influx to the biosphere. A 2D axisymetric hydromechanical modeling of the Anderlues natural gas storage site is then performed. The design of the shaft seal system appears to be a determinant element to evaluate the risks of CO2 leakage. [less ▲]

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See detailDark atoms : properties and observational consequences
Wallemacq, Quentin ULg

Master's dissertation (2011)

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See detailAlternative strategies for aphid biological control: special regard on honeydew and bacteria from aphids
Leroy, Pascal ULg

Doctoral thesis (2011)

Aphids constitute a scourge in agriculture and are a major problem for crops worldwide. By feeding on the phloem sap but also by injecting saliva and viruses in plant tissues, they cause a weakening and ... [more ▼]

Aphids constitute a scourge in agriculture and are a major problem for crops worldwide. By feeding on the phloem sap but also by injecting saliva and viruses in plant tissues, they cause a weakening and impair the growth of the host-plant. Moreover, honeydew, the aphid excretory product, reduces transpiration and photosynthesis. But honeydew also attracts many predators and parasitoids of aphids, playing a key role in tritrophic interactions between plants, pests and beneficial insects. In this context, the main objective of this thesis was to promote the use of the hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae) as an efficient biological control agent in aphid management strategies. Two different approaches have been developed here with success: (1) the introduction of this auxiliary in the fields or under greenhouses, using a biological control device developed in this work and (2) the attraction, the retention and the oviposition stimulation of the populations naturally present or manually introduced in the fields. To achieve these objectives, special attentions were focused on the aphid honeydew that is abundant on aphid infested plants, with special attention to the bacteria present in this aphid secretion. First, our studies allowed determining that honeydew acts as a volatile and a contact kairomone both for the E. balteatus larvae and adults but also on the Asian coccinellid Harmonia axyridis (Pallas) helping these aphidophagous predators to locate prey. In a second time, using semiochemicals from plants [(Z)-3-hexenol, R-(+)-limonene] and aphids [E-(β)-farnesene] but also crude and artificial honeydew, the hoverfly oviposition was artificially induced (without plants or aphids) on an inert surface. The so obtained eggs were then introduced in field crops to regulate aphid populations (biological control device). Then, the volatile compounds associated with honeydew were identified and tested as potential attractants and ovipositional stimulants: an artificial honeydew as well as an attractive formulation were composed and successfully tested in field crops since they both increased the presence of auxiliaries in targeted areas. Finally, the interaction between the host plant and aphids was envisaged to determine whether aphids are able to modify the host plant amino acid content in order to ingest sufficient nitrogen for growth: this study highlighted that the proportions of glutamine and asparagine significantly increase in the phloem sap when plants are infested. [less ▲]

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See detailSur les ensembles paradoxaux : de Banach-Tarski à Dougherty-Foreman
Kleyntssens, Thomas ULg

Master's dissertation (2011)

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See detailImprimeurs et société dans les Pays-Bas méridionaux et en principauté de Liège (1473-ca 1520)
Adam, Renaud ULg

Doctoral thesis (2011)

La thématique placée au centre de cette dissertation doctorale pourrait se résumer à cette question : comment les premiers imprimeurs se sont intégrés au tissu socio-économique des Pays-Bas méridionaux et ... [more ▼]

La thématique placée au centre de cette dissertation doctorale pourrait se résumer à cette question : comment les premiers imprimeurs se sont intégrés au tissu socio-économique des Pays-Bas méridionaux et de la principauté de Liège aux tournants des XVe et XVIe siècles ? Cette étude a été structurée autour de trois axes. La vétusté des synthèses sur le sujet et l’évolution constante de la recherche ont rapidement imposé la nécessité de réécrire en premier lieu un historique détaillé, ville par ville, de l’introduction de l’art typographique et de son évolution jusqu’en 1520. Les regards se sont ensuite portés sur le métier d’imprimeur avec des questionnements centrés sur le statut juridique et l’organisation de cette profession, sur le fonctionnement interne d’une imprimerie ainsi que sur la commercialisation des livres et le profil de la clientèle. Les résultats de la dernière partie sont le fruit d’une investigation dans la composition de la communauté typographique et d’une tentative de décorticage des trames réticulaires nouées avec les autres acteurs de la société urbaine. [less ▲]

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See detailEvidence for a role of microRNA-21 and microRNA-125b in negatively regulating angiogenic processes
Malvaux, Ludovic ULg

Doctoral thesis (2011)

Recently discovered, miRNAs have quickly become strong regulators of biological processes. These small non-coding RNAs of about 22 nucleotides partially base pair to the 3’UTR of the targeted mRNAs and ... [more ▼]

Recently discovered, miRNAs have quickly become strong regulators of biological processes. These small non-coding RNAs of about 22 nucleotides partially base pair to the 3’UTR of the targeted mRNAs and repress them. Due to their wide range effects, microRNAs were extensively studied in various diseases and were rapidly demonstrated to be deregulated in pathologies such as cancer. More recently, they have been shown to be implicated in vascular network formation (angiogenesis) and were proposed to be used in anti-angiogenic therapies. Nowadays about twenty angiomiRs have been discovered including the endothelial specific miR-126. As observed in several miRNA profiling of endothelial cells and confirmed in our laboratory in HUVECs (human umbilical veins endothelial cells), miR-21 and miR- 125b are highly expressed in this cell type suggesting that these miRNAs could play a role in vascular network formation. We then studied the implication of miR-21 and miR-125b in in vitro as well as in vivo angiogenesis. One of the most studied miRNA in cancer progression is miR-21 as it was shown to modify proliferating properties of numerous tumor cells. Our experiments revealed that miR-21 overexpression and inhibition have no direct effect on endothelial cells proliferation rate. However, miR-21 overexpression leads to the inhibition of HUVECs migration and tube formation as demonstrated in in vitro angiogenic assays. Moreover, opposite effects were observed upon miR-21 inhibition. We also confirmed that RhoB, a small Rho-GTPase implicated in stress fibers formation, is involved in these phenomena as RhoB inhibition using siRNA mimics miR-21 overexpression in endothelial cells. Moreover, miR-21 modulation affects RhoB mRNA and protein expressions. We further demonstrated a direct interaction between miR-21 and the RhoB 3’UTR confirming that miR-21 modulates angiogenesis partially through its effect on RhoB expression. A similar approach was used to study the implication of miR-125b in vascular network formation. In vivo, miR-125b expression was modulated in the zebrafish revealing that miR-125b expression needs to be controlled for proper intersomitic blood vessels establishment. In vitro, miR-125b overexpression decreases HUVECs migration and tube formation whereas miR-125b inhibition increases these functions. A transcriptomic analysis suggests that numerous adhesion molecules such as VE-cadherin or MCAM are involved in these processes. Furthermore, other proteins known to regulate angiogenesis such as the transcription factor ETS1 and the VEGFA receptor, VEGFR2 were also shown to be regulated by miR-125b. This observation confirms that miR-125b modulates angiogenic properties of endothelial cells. Finally, we investigated the impact of miR-21 and miR-125b overexpression in an in vivo pathological model of angiogenesis. In a mouse model of choroïdal neovascularization we demonstrated that miR-21 or miR-125b overexpression in the eyes of these mice decreases blood vessel establishment suggesting that these microRNAs could be used as therapeutic antiangiogenic agents. Taken together, the results presented in this thesis show that miR-21 and miR-125b regulate angiogenesis in vitro and in vivo. [less ▲]

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See detailIntermédiaires et dynamique des réseaux fluides. Du mode d'existence de la norme ISO 14001 en Région wallonne
Semal, Nathalie ULg

Doctoral thesis (2011)

How does a standard "make a living"? How does a written list of requirements acquire some reality? How can a particular agreement take effect in numerous worldwide distant sites?

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See detailRole de l'ADN endogène et d'Interferon Response Factor-3 dans l'induction des réponses immunitaires médiées par les lymphocytes T auxiliaires de type 2.
Marichal, Thomas ULg

Doctoral thesis (2011)

Adaptative type 2 helper T cell (Th2) responses represent an important component of adaptative immunity and are implicated in various (patho)physiological processes such as allergic diseases, host defense ... [more ▼]

Adaptative type 2 helper T cell (Th2) responses represent an important component of adaptative immunity and are implicated in various (patho)physiological processes such as allergic diseases, host defense against helminths and artificially adjuvanted vaccination. Induction of adaptative T responses occurs with the help of innate immune cells, especially dendritic cells (DCs). These DCs make the link between innate and adaptative immunity by taking up antigens in peripheral tissues, migrating to lymphoïd organs and presenting antigens to T lymphocytes. Direct or indirect activation of these cells depends on the interaction between exogenous or endogenous danger signals and conserved innate immune receptors, mainly represented by Pattern Recognition Receptors (PRRs). Despite the importance of Th2 responses, the innate immune mechanisms leading to their activation remain partially unknown. For this reason, we have been interested in immune mechanisms underlying the induction of Th2 responses in two major Th2-dependent immunological processes : airway allergy and vaccination with aluminium hydroxides (alum). Airway allergy, of which the most severe manifestation is allergic ashma, is a constantly increasing disease in developped countries. It appears clearly that the stimulation of PRRs by allergens or immunostimulatory molecules plays a key role in the pathophysiology of airway allergy. In addition, PRRs transduce the signal though a limited number of signaling pathways and the role of Interferon Response Factor (IRF)-3 and IRF-7, two important transcription factors downstream of various PRRs, in the pathogenesis of allergic asthma, remains unknown. Therefore, we have investigated their potentiel implication in this disease. We have discovered that IRF-3, but not IRF-7, plays an essential role in allergic airway sensitization against house dust mite antigens, the main allergen source in humans. We have further demonstrated that IRF-3 was intrinsically required in lung DCs for their proallergic function. The IRF-3-dependent effects were independent of type I interferons, the main target genes of IRF-3. Alum is the most widely used artificial adjuvant in human and animal vaccination. Yet, little is known about its mechanism of action, in particular regarding the nature of signals and signaling pathways promoting Th2 responses. We have postulated that alum, like any other efficient adjuvant, must be expected to stimulate innate immunity. On one hand, alum does not contain any molecular pattern that is recognized by PRRs and, on the other hand, alum is known to be cytotoxic. Therefore, we hypothetised that alum-induced endogenous danger signals could play a role in its adjuvant activity. Here, we report that alum induces cell death and subsequent DNA release. This DNA acts as a endogenous immunostimulatory signal relaying alum adjuvant activity on adaptative responses. Furthermore, we propose that host DNA differentially regulates IgG1 and IgE production following alum immunization. Indeed, an IRF-3-dependent DNA signaling pathway plays a role in the activation of inflammatory DCs, the subsequent induction of Th2 response and IgE isotype switching, whereas DNA also induces IgG1 production through IRF-3- independent mechanisms. The finding that host cell endogenous DNA is a damageassociated molecular pattern relaying alum adjuvant activity may thus help in the comprehension of the mechanisms of action of current vaccines and in the design of novel adjuvants. In conclusion, this work has identified a previously unappreciated role for IRF-3, a transcription factor downstream of various PRRs primarily implicated in antiviral responses, in two Th2-dependent immunological processes: allergic asthma and alum-based vaccination. In these models, we have shown that IRF-3 was intrinsically required in professional antigen presenting cells, namely DCs, in order to activate them, a precondition for the priming of adaptative Th2 responses. In addition, we also discovered that host DNA released upon alum treatment acts as an endogenous danger signal mediating the adjuvant activity of alum. [less ▲]

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See detailSemi-solid constitutive modeling for the numerical simulation of thixoforming processes.
Koeune, Roxane ULg

Doctoral thesis (2011)

Semi-solid thixoforming processes rely on a material microstructure made of globular solid grains more or less connected to each other, thus developing a solid skeleton deforming into a liquid phase ... [more ▼]

Semi-solid thixoforming processes rely on a material microstructure made of globular solid grains more or less connected to each other, thus developing a solid skeleton deforming into a liquid phase. During processing, the material structure changes with the processing history due to the agglomeration of the particles and the breaking of the grains bonds. This particular evolutive microstructure makes semi-solid materials behave as solids at rest and as liquids during shearing, which causes a decrease of the viscosity and of the resistance to deformation while shearing. Thixoforming of aluminum and magnesium alloys is state of the art and a growing number of serial production lines are in operation all over the world. But there are only few applications of semi-solid processing of higher melting point alloys such as steel. This can partly be attributed to the high forming temperature combined with the intense high temperature corrosion that requires new technical solutions. However the semi-solid forming of steels reveals high potential to reduce material as well as energy consumption compared to conventional process technologies, such as casting and forging. Simulation techniques exhibit a great potential to acquire a good understanding of the semi-solid material process. Therefore, this work deals with the development of an appropriate constitutive model for semi-solid thixoforming of steel. The constitutive law should be able to simulate the complex rheology of semi-solid materials, under both steady-state and transient conditions. For example, the peak of viscosity at start of a fast loading should be reproduced. The use of a finite yield stress is appropriate because a vertical billet does not collapse under its own weight unless the liquid fraction is too high. Furthermore, this choice along with a non-rigid solid formalism allows predicting the residual stresses after cooling down to room temperature. Several one-phase material modeling have been proposed and are compared. Thermo-mechanical modeling using a thermo-elasto-viscoplastic constitutive law has been developed. The basic idea is to extend the classical isotropic hardening and viscosity laws to the non solid state by considering two non-dimensional internal parameters. The first internal parameter is the liquid fraction and depends on the temperature only. The second one is a structural parameter that characterizes the degree of structural build up in the microstructure. Those internal parameters can depend on each other. The internal parameters act on the the viscosity law and on the yield surface evolution law. Different formulations of viscosity and hardening laws have been proposed and are compared to each other. In all cases, the semi-solid state is treated as a particular case, and the constitutive modeling remains valid over the whole range of temperature, starting from room temperature to above the liquidus. These models are tested and illustrated by mean of several representative numerical applications. [less ▲]

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See detail"Intentionnalité et inconscient. Réflexions sur le fonctionnement de la vie psychique à partir du premier Husserl et de Freud"
Gyemant, Maria ULg

Doctoral thesis (2011)

This work tries the limits of Husserl’s concept of intentionality as it is conceived in the Logical Investigations. Once these limits exposed, we claim that Husserl’s theory of intentionality be completed ... [more ▼]

This work tries the limits of Husserl’s concept of intentionality as it is conceived in the Logical Investigations. Once these limits exposed, we claim that Husserl’s theory of intentionality be completed with a theory of the unconscious of Freudian inspiration. Thus, on the conceptual basis of Husserl and Freud’s work we elaborate an exhaustive map of the human mind, that shows not only the consciousness, but also the other mental phenomena. Our first section shows that Husserl’s concept of intentionality is established in opposition to Brentano’s intentionality. We also analyse the problem it is meant to solve, namely how exactly the mind connects with its objects. We show that this way of understanding intentionality cannot explain the dynamical aspect of intentional acts. Our second section is thus dedicated to this issue. A group of texts written by Husserl around 1913-1914 on the concept of tendency show clearly that Husserl never stopped in fact questioning the dynamical character of intentionality although he couldn’t explain it without thinking it as a form of intentionality. This solution leads nevertheless to an infinite regress. We have chosen thus in our third section to try a new approach of the dynamical aspect by using Freud’s approach to the Unconscious. The Freudian Unconscious has thus been articulated to Husserl’s theory of intentionality and at the same time the dynamical aspect of the latter has found an appropriate conceptual expression. [less ▲]

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See detailOn the sets of real vectors recognized by finite automata in multiple bases
Brusten, Julien ULg

Doctoral thesis (2011)

This thesis studies the properties of finite automata recognizing sets of real vectors encoded in positional notation using an integer base. We consider both general infinite-word automata, and the ... [more ▼]

This thesis studies the properties of finite automata recognizing sets of real vectors encoded in positional notation using an integer base. We consider both general infinite-word automata, and the restricted class of weak deterministic automata, used, in particular, as symbolic data structures for representing the sets of vectors definable in the first order additive theory of real and integer numbers. In previous work, it has been established that all sets definable in the additive theory of reals and integers can be handled by weak deterministic automata regardless of the chosen numeration base. In this thesis, we address the reciprocal property, proving that the sets of vectors that are simultaneously recognizable in all bases, by either weak deterministic or Muller automata, are those definable in the additive theory of reals and integers. Precisely, for weak deterministic automata, we establish that the sets of real vectors simultaneously recognizable in two multiplicatively independent bases are necessarily definable in the additive theory of reals and integers. For general automata, we show that the multiplicative independence is not sufficient, and we prove that, in this context, the sets of real vectors that are recognizable in two bases that do not share the same set of prime factors are exactly those definable in the additive theory of reals and integers. Those results lead to a precise characterization of the sets of real vectors that are recognizable in multiple bases, and provide a theoretical justification to the use of weak automata as symbolic representations of sets. As additional contribution, we also obtain valuable insight into the internal structure of automata recognizing sets of vectors definable in the additive theory of reals and integers. [less ▲]

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See detailLes papyrus scolaires grecs et latins chrétiens
Carlig, Nathan ULg

Master's dissertation (2011)

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See detailNutrient fluxes and soil microbial processes
Bazgir, Masoud ULg

Doctoral thesis (2011)

Because of previous intense forest use and over exploitation in the past centuries, the plantation of coniferous stands, especially Norway spruce (Picea abies L. KARST.) with high production potentials ... [more ▼]

Because of previous intense forest use and over exploitation in the past centuries, the plantation of coniferous stands, especially Norway spruce (Picea abies L. KARST.) with high production potentials has been a common European afforestation strategy. However, the characteristics of Norway spruce such as susceptibility to windfall, forest dieback, drought, as well as soil acidification have caused negative ecological impacts in many sites. Conversion of conifers into deciduous or mixed stands has been suggested by some foresters, in order to improve the stability, ecology and biodiversity of forest ecosystems. Such changes in forest management require specific information on the impact of tree species on nutrient cycling, soil properties and microbial activities. In this study, six broadleaved species were growing at the same site with similar condition in terms of soil type, land use history and climate. Thus, the potential effects on biogeochemical cycling could be attributed to tree species. In this thesis, I focused on the effect of broadleaved species (conversion scenario) contrasting in terms of ecological characteristics (pioneer species versus main forestry species) and physiological characteristics (N2-fixing tree species (alder) versus non N2-fixing species) and Norway spruce (no conversion scenario) on (a) soil chemical properties (b) soil microbial activities and microbial biomass (c) nutrient input fluxes from throughfall and litterfall (d) foliar nutrient status. This investigation was carried out in south-eastern Belgium at a site converted in 1998 to a mixed deciduous stand, after two spruce generations. Plantations of common alder (Alnus glutinosa (L.) GAERTN.), european beech (Fagus sylvatica L.), pedunculate oak (Quercus robur L.), silver birch (Betula pendula ROTH.), goat willow (Salix caprea L.) and rowan (Sorbus aucuparia L.) were located in 4 fenced plots within a 81 ha catchment. Soil chemical properties (soil organic matter, pH, cation exchange capacity, base saturation, exchangeable cations), soil microbial activities (net N mineralization, potential nitrification, basal respiration) and microbial biomass (microbial biomass C and N) were measured under broadleaves and spruce. Soil chemistry of this highly acid soil was improved, 11 years after conversion, through an increase in base saturation and the exchangeable Mg2+ pool under rowan, as well as an increase in the exchangeable Ca2+ pool under alder, oak and rowan. Exchangeable acidity due to H+ in the forest floor also decreased under broadleaves. Nitrification was increased under the N2 fixing alder and decreased under young spruce. The C:N ratio of cold water-extractable soil organic matter fractions revealed to be a good indicator of potential nitrification rates within this site and across species, with a threshold of a C:N ratio of 10 above which soils did not nitrify. Throughfall and litterfall under the tree species were investigated by installing 63 throughfall collectors and 63 litter traps within 3 fenced plots (broadleaves) and across the catchment (young spruce). We measured the quantity of litterfall (foliar, twigs, reproductive parts and total), the quality of foliar litterfall (macro and micro-elements and C/N ratio) and calculated the potential nutrient return to the forest floor though foliar litterfall. For throughfall, we analyzed macro and micro-element concentrations and throughfall fluxes. Foliar nutrient status was determined by chemical analyses of fresh leaves and spruce needles of 3 age classes. The throughfall deposition of Ca2+, Mg2 and K+ was significantly higher under rowan and birch. NO3--N throughfall fluxes were significantly higher under young spruce compared to broadleaves. We observed the lowest total litterfall quantity produced by oak, while the highest litterfall quantity observed under rowan. Foliar litterfall of rowan showed significantly higher potential nutrient fluxes of Ca, Mg and K compared to other species, which corresponds to fresh foliage concentrations. The foliar litterfall was a main source of Ca, while for K throughfall was the main source of nutrient return to the forest floor in the study area. In spruce needles, Ca and Mg concentrations were at deficiency level and K concentrations at critical level, according to threshold values. Our results demonstrated that the plantation of pioneer species, especially rowan, may enhance the base cations in the forest floor on nutrient poor, acid soils through higher input in litterfall and throughfall. [less ▲]

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See detailApplication du Laser Cladding au rechargement et à la fabrication de pièces
Hardenne, Thibaut ULg

Master's dissertation (2011)

Ce travail commence par présenter les techniques de fabrication par addition de matière dont le procédé Laser Cladding (dépôt de poudre métallique par laser). Puis, ce procédé est comparé aux techniques ... [more ▼]

Ce travail commence par présenter les techniques de fabrication par addition de matière dont le procédé Laser Cladding (dépôt de poudre métallique par laser). Puis, ce procédé est comparé aux techniques de rechargement conventionnelles sur base de résultats présentés dans la littérature. Deux types d'essais expérimentaux ont ensuite été étudiés. Premièrement, des blocs ont été réalisés en acier inoxydable 316L sur un substrat en acier S235 à l'aide d'un laser bre de 300W. Les paramètres ont été optimisés a n d'obtenir une bonne fusion et un bon recouvrement entre cordons. L'optimisation se base sur des analyses d'échantillons polismiroir. La porosité a été estimée par seuillage d'image, mais les blocs étaient globalement fort denses. La microstructure a révélé des grains s'étendant sur plusieurs couches et compos és de cellules. Des essais de microdureté et des analyses EDX ont montré qu'il existait une zone de dilution plus dure à la frontière substrat/revêtement. La taille des cellules est plus grande au sommet des blocs qu'à la base, si bien que la dureté diminue en s'éloignant de la liaison. La stratégie de traçage in uence les propriétés mécaniques obtenues lors de tests de traction. Deuxièmement, des parois en titane Ti-6Al-4V ont été fabriquées sur un substrat de même nature, dans une tente gon ée à l'argon pour se protéger de l'oxydation. Cependant la surface colorée des parois et les essais de microdureté ont mis en évidence une oxydation des premiers cordons. Les parois ne contenaient pas de porosité et la microstructure était composée de grains colonaires s'étendant verticalement. Ces grains avaient une structure aciculaire de type Widmänstatten. Le travail se termine par une recherche bibliographique des possibilités de préchau age du substrat lors de la fabrication par Laser Cladding. [less ▲]

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See detailUn nouveau regard sur les reliefs en marbre noir de Theux sculptés au XVIe siècle à Liège et ses environs, 3 vol.
Warnauts, Samuelle ULg

Master's dissertation (2011)

Analyse et réévaluation critique suivies d’un catalogue complet d’œuvres réalisées en marbre noir dit de Theux.

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See detailImprovement of randomized ensembles of trees for supervised learning in very high dimension
Joly, Arnaud ULg

Master's dissertation (2011)

Tree-based ensemble methods, such as random forests and extremely randomized trees, are methods of choice for handling high dimensional problems. One important drawback of these methods however is the ... [more ▼]

Tree-based ensemble methods, such as random forests and extremely randomized trees, are methods of choice for handling high dimensional problems. One important drawback of these methods however is the complexity of the models (i.e. the large number and size of trees) they produce to achieve good performances. In this work, several research directions are identified to address this problem. Among those, we have developed the following one. From a tree ensemble, one can extract a set of binary features, each one associated to a leaf or a node of a tree and being true for a given object only if it reaches the corresponding leaf or node when propagated in this tree. Given this representation, the prediction of an ensemble can be simply retrieved by linearly combining these characteristic features with appropriate weights. We apply a linear feature selection method, namely the monotone LASSO, on these features, in order to simplify the tree ensemble. A subtree will then be pruned as soon as the characteristic features corresponding to its constituting nodes are not selected in the linear model. Empirical experiments show that the combination of the monotone LASSO with features extracted from tree ensembles leads at the same time to a drastic reduction of the number of features and can improve the accuracy with respect to unpruned ensembles of trees. [less ▲]

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See detailMéthodes d'identification des paramètres dans un modèle du système cardiovasculaire
Pironet, Antoine ULg

Master's dissertation (2011)

Les dysfonctions du système cardiovasculaire sont une origine majeure des admissions dans les unités de soins intensifs. Dans ces unités, les patients sont très instables et les cliniciens disposent d’un ... [more ▼]

Les dysfonctions du système cardiovasculaire sont une origine majeure des admissions dans les unités de soins intensifs. Dans ces unités, les patients sont très instables et les cliniciens disposent d’un nombre limité de mesures pour prendre rapidement les bonnes décisions. L’utilisation de modèles patient-spécifiques pour guider les clini- ciens offre alors des perspectives réelles. Un modèle simple à six compartiments du système cardiovasculaire a été développé par Smith et al. et une méthode d’identification des paramètres de ce modèle a été développée par Revie et al. Ce modèle a été étendu en y ajoutant deux compartiments représentant les oreillettes, dont le comportement est décrit par un modèle inspiré de travaux existants. Une méthode d’identification similaire à celle utilisée par Revie et al. a été développée pour les nouveaux paramètres. Pour ne pas devoir recourir à la pression auriculaire, difficile à mesurer expérimentalement, une méthode permettant de déduire la pression auriculaire à partir de la pression ventriculaire a également été introduite. L’application du modèle étendu et de la méthode d’identification correspondante à des données expérimentales montre que l’introduction des oreillettes dans le modèle ne cause pas de trop grandes erreurs et que la méthode d’estimation de la pression auriculaire est correcte. En conclusion, la valeur ajoutée de la méthode développée dans ce travail est grande, puisqu’elle permet d’obtenir des informations supplémentaires sans introduire de grandes erreurs et sans imposer le besoin de recourir à de nouvelles mesures. [less ▲]

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See detailActivité et modulation de la NADPH oxydase des neutrophiles équins: tests in vitro sur cellules entières et mise au point du dosage en "cell-free system"
Derochette, Sandrine ULg

Master's dissertation (2011)

Chez le cheval, la réponse inflammatoire causée par certaines pathologies (obstruction intestinale, fourbure,…) implique une stimulation excessive des polymorphonucléaires neutrophiles (PMNs) libérant de ... [more ▼]

Chez le cheval, la réponse inflammatoire causée par certaines pathologies (obstruction intestinale, fourbure,…) implique une stimulation excessive des polymorphonucléaires neutrophiles (PMNs) libérant de grandes quantités d’espèces activées de l’azote et de l’oxygène (RNOS). La première enzyme impliquée dans la formation de ces espèces activées est la NADPH oxydase, produisant l’anion superoxyde (O2.-) d’où dérivera la formation de diverses RNOS. Actuellement, la NADPH oxydase est considérée comme une cible privilégiée pour la modulation de l’inflammation excessive. Le but de ce travail a été d’étudier l’effet de molécules modulant la réponse inflammatoire (la curcumine, la quercétine et l’acépromazine : ACP) ou l’activité de la NADPH oxydase (le diphénylène iodonium : DPI) sur la production de RNOS par les PMNs stimulés. L’étude a été menée sur des PMNs équins isolés où la production de RNOS a été mise en évidence par trois techniques différentes : la chimiluminescence assistée par la lucigénine et la réduction du ferricytochrome C, ciblant essentiellement la production d’O2.- ; et une technique de fluorescence utilisant la 2’,7’-dichlorofluorescine-diacétate (DCFH-DA), ciblant la production intra et extracellulaire de RNOS. L’effet de ces molécules a pu être testé de façon plus spécifique sur la NADPH oxydase par une mesure en « cell-free system » que nous avons mise au point et consistant en la reconstitution in vitro de la NADPH oxydase. Nous avons constaté que les molécules polyphénoliques testées (quercétine et curcumine) agissaient surtout comme des antioxydants stoechiométriques en neutralisant les RNOS intracellulaires et extracellulaires sans pour autant être des inhibiteurs de la NADPH oxydase. Nous avons également démontré que certaines molécules (l’ACP et le DPI) utilisées à forte concentration pouvaient amplifier la réponse oxydante des PMNs. Enfin, grâce à la technique du « cell free system » nous avons démontré, pour la première fois, l’effet anti-catalytique du DPI sur la NADPH oxydase équine. La complémentarité de ces techniques permettra de faire la distinction entre un effet antioxydant, pro-oxydant ou anti-catalytique d’une molécule biologique pouvant moduler la réponse inflammatoire. Enfin, ce travail présente les premiers résultats de l’isolement des sous-unités membranaires de la NADPH oxydase équine. Les résultats sont encourageants et la purification à plus long terme du complexe enzymatique entier avec la production d’anticorps spécifiques devrait permettre la mise au point d’un dosage original de la NADPH oxydase consistant en l’immuno-capture de l’enzyme active afin de cibler l’effet de substances biologiques sur son assemblage et son activité spécifique. [less ▲]

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See detailEconomic and environmental impacts of several retrofit options for residential buildings
Gendebien, Samuel ULg

Master's dissertation (2011)

Nowadays, important efforts are deployed to reduce our actual residential building consumption which represents about 40% (25% for the residential sector and 15% for the non-residential sector) of the ... [more ▼]

Nowadays, important efforts are deployed to reduce our actual residential building consumption which represents about 40% (25% for the residential sector and 15% for the non-residential sector) of the total energy consumption in Europe. The aim of this paper is to evaluate the environmental and economical impact of several retrofit options for residential buildings. Our study focuses on the Walloon Region of Belgium. A “bottom-up” methodology is applied: this methodology focuses first on a micro-analysis. Results from this micro-analysis are then used and extended to a macro-analysis. The presented methodology does not permit to determine with precision the global consumption of residential buildings in the Walloon Region. However, the latter methodology allows pointing out some economical and environmental trends related to the different investigated retrofit options. The first part of this end-of-study work offers an overview of the Walloon building stock by presenting statistic data on the Walloon residential houses. From these latter statistic data, it is possible to divide the Walloon building stock by means of arborescence. Each type of building is characterized by constructive data (mean area, Uwall, Uwindow…) and by heating production system efficiency. Thanks to these data, it is possible to determine the gas and electrical annual consumption for each type of residential building by means of a computer program that simulates residential building. The latter computer program is also used to determine the annual energy consumption of envelope retrofitted houses. Retrofit options related to heat and/or cool production are also investigated. A macro-point of view study is carried out in order to determine the potential of energy saving of each investigated options. An environmental comparison between the several envisaged retrofit options is realized in terms of CO2 emission, final and primary annual energy consumption for each type of building. An economical study is carried out in order to determine the profitability of each investigated options for citizens. The work also proposes a reflection about the actual incentive policies. [less ▲]

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See detailTheoretical and Experimental Analysis of Liquid Flooded Compression in Scroll Compressors
Bell, Ian ULg

Doctoral thesis (2011)

Adding liquid to the working fluid in scroll compressors can allow for a working process that approaches isothermal compression. When liquid flooding and regeneration is applied to refrigeration and heat ... [more ▼]

Adding liquid to the working fluid in scroll compressors can allow for a working process that approaches isothermal compression. When liquid flooding and regeneration is applied to refrigeration and heat pump systems, simple cycle modeling predicts that for systems that operate at very large temperature lifts, the increase in system coefficient of performance can be greater than 50%. In order to better understand the liquid-flooded working process, a detailed scroll compressor model has been developed which comprises a geometric model and an overall compressor model. The geometric model includes numerically validated analytic solutions for all geometric parameters, including force terms, for constant wall thickness scroll wraps that can have multiple pairs of compression chambers. The overall model includes a frictionally-corrected isentropic nozzle leakage model, adaptive Runge-Kutta solver for the system of differential equations, and numerically efficient thermodynamic and transport property routines. The compressor model has been validated against testing conducted on the Liquid-Flooded Ericsson Cycle for oil mass fractions as high as 92% oil by mass with error in predictions of shaft power and mass flow less than 3%. Optimization of the compressor performance with flooding for several applications is carried out, and with optimization, overall isentropic efficiencies over 75% are predicted for configurations with large amounts of oil flooding. Further testing on a refrigerant R410A vapor injected compressor with oil injection has shown that the performance with oil injection improves monotonically with the oil injection rate as long as the oil is cooled prior to injection. [less ▲]

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See detailNational Mythology and Colonial Trauma in Alex Miller’s Journey to the Stone Country
Joubail, Houda ULg

Master's dissertation (2011)

In 1991 the Australian government instigated a process of reconciliation between indigenous and non-indigenous people. This process aimed at laying the foundations of a postcolonial nation through the ... [more ▼]

In 1991 the Australian government instigated a process of reconciliation between indigenous and non-indigenous people. This process aimed at laying the foundations of a postcolonial nation through the establishment of the truth about the past, the acknowledgment of the injustices inflicted on the natives, and the development of appropriate forms of justice. Hidden facts about dispossession and genocide were divulged thanks to various inquiries carried out throughout the country. Such hideous facts plunged settler Australians into angst and guilt and prompted many contemporary white novelists to tackle the hitherto taboo issue of colonialism and its legacies in their works. At first glance, this literary endeavour to deal with the darkest chapter in the Australian history appears as a genuine determination to confront the trauma of the colonial past. Nevertheless, a closer look at some contemporary Australian novels reveals an altogether different intention. My dissertation seeks to explore the fictional representations of colonialism and Aboriginal suffering in one of these novels, namely, Alex Miller’s Journey to the Stone Country (2002), in order to emphasise how, through the use of subtle representational and discursive strategies, the author contrives to lessen the impact of the colonial violence. Annabelle Beck, a descendant of British settlers, and Bo Rennie, a former Aboriginal ringer, set out on a journey from Burranbah in Central Queensland to the sacred ground of the Jangga people. As the journey unfolds, a disturbing past of injustice and loss emerges. The two main protagonists are brought to discover their common history as members of neighbouring families. The exploration of their past culminates in the revelation of a massacre in which Bo’s ancestors were savagely killed by Annabelle’s grandfather and his friends. Admittedly, the author tackles the controversial issues of inter-racial relationships, dispossession, and the legacies of colonial violence, yet his approach is far from being postcolonial. The first part of the dissertation will, indeed, attempt to examine how he makes use of the representational strategies to portray the Aboriginal characters as uneducated, untrustworthy, and racist. Furthermore, this part will emphasise that Miller tends to dismantle colonial myths only to construct neo-colonial ones, particularly, the equal importance of European and Aboriginal heritages. This assumption of egalitarianism is, in fact, not as fair as it seems at first sight given the long history of injustices to which Aborigines were subjected. The second part of the dissertation is dedicated to the analysis of the author’s response to the colonial trauma. A close reading of the novel in the lights of trauma theories reveals that the author resists the full understanding and acknowledgement of the truth about the past. He, indeed, undermines his avowed intention of exposing the atrocities inflicted on Aboriginal people through a series of discursive strategies. The dissertation will mainly draw on Dominick LaCapra’s writings about trauma to suggest that Miller is caught within the process of what LaCapra refers to as “acting out”, that is to say the tendency to repress the traumatic past to avoid any critical confrontation. Therefore, though he apparently engages in the venture of exploring the colonial past, Miller advocates the law of silence, a law which is hardly compatible with the requirements of a true reconciliation. [less ▲]

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See detailEpigenetic Therapy of Lung Cancers: Anti-tumoral effect of valproate on small cell lung cancer
Hubaux, Roland ULg

Doctoral thesis (2011)

Lung cancer is the leading cause of cancer-related death worldwide. Among lung carcinomas, the outcome of small cell lung carcinoma (SCLC) patients is the poorest of any histological subtype with five ... [more ▼]

Lung cancer is the leading cause of cancer-related death worldwide. Among lung carcinomas, the outcome of small cell lung carcinoma (SCLC) patients is the poorest of any histological subtype with five-year survival rate of less than 20 and 5 % for limited and extensive stage respectively. Based on increasing evidence that inhibitors of histones deacetylases (HDAC) have anticancer properties, the goal of this study was to evaluate the ability of valproate (VPA) to improve efficacy of chemotherapeutic regimen in SCLC. We show that VPA directly induces apoptosis of SCLC cell lines at concentrations relevant for clinical uses. Furthermore, VPA synergizes with two chemotherapeutic regimen used in first (cisplatin + etoposide) and second line (cyclophosphamid + vindesine + doxorubicin) treatments. Both mitochondrial and death receptor pathways are involved in VPA-induced apoptosis. Although VPA promotes production of reactive oxygen species, free radical scavenger N-acetylcystein is not sufficient to inhibit apoptosis. As expected, VPA triggers hyperacetylation of histone H3 and increases expression of p21. VPA reduces levels of BclxL, induces cleavage of Bid, translocation of Bax to mitochondria, release of cytochrome c into cytosol and phosphorylation of Erk and H2AX. Transcriptomic analyses by microarrays and quantitative RT-PCR have underscored a series of genes candidates potentially implicated into sensitivity of SCLC to VPA. Among these, the Fzd7 receptor of the WNT pathway is essential for VPA proapoptotic activity. Efficiency of VPA combined to first and second line chemotherapeutic agents is supported by preclinical models of SCLC cells engrafted into SCID mice. The second line combination is presently tested in a clinical trial with patients presenting with refractory or relapsing small cell lung cancer (protocol 01081 at http://www.elcwp.org). [less ▲]

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See detailOptimally Locating Facilities with Variable Characteristics
Kucukaydin, Hande ULg

Doctoral thesis (2011)

Facility location problems aim at optimally locating facilities like plants, warehouses, convenience stores, shopping malls etc. They can have different objectives such as maximizing the profit gained ... [more ▼]

Facility location problems aim at optimally locating facilities like plants, warehouses, convenience stores, shopping malls etc. They can have different objectives such as maximizing the profit gained from the customers or minimizing the costs of locating facilities and serving the customers. In this thesis, we mainly focus on competitive facility location problems which constitute a special family. In a competitive facility location problem, a firm or franchise is concerned with installing new facilities to serve customers in a market where existing facilities with known locations and attractiveness levels compete for increasing their market share and profit. We can classify these problems into two groups: those with non-reactive competition and those with reactive competition. Three different types of competitive facility location models are proposed in order to determine the locations and attractiveness levels of the new facilities to maximize the profit in this thesis. The first one belongs to the former class, where the last two models fall into the latter one. We formulate the first one as a mixed-integer nonlinear programming problem and propose three methods for its solution: a Lagrangean heuristic, a branch-and-bound method with Lagrangean relaxation, and a branch-and-bound method with nonlinear programming relaxation. The computational results obtained on a set of problem instances show that the branch-and-bound method using nonlinear programming relaxation is the most efficient and accurate solution method in order to solve the proposed problem. We consider next an extension of this model by relaxing the assumption that the competitor in the market does not react to the opening of new facilities. In other words, the competitor can react by adjusting the attractiveness levels of its existing facilities with the objective of maximizing its own profit. To this end, a bilevel mixed-integer nonlinear programming model is formulated. We transform this bilevel model into an equivalent one-level mixed-integer nonlinear program and solve it by a global optimization method. For this problem, we also consider a scenario in which the new entrant firm ignores the reaction of the competitor. The experimental results indicate that anticipating the competitor's reaction by including this into his optimization problem increases the profit of the new entrant firm, whereas the competitor's profit is decreased. The last competitive facility location model relaxes the limitation about the competitor's reaction: now the competitor can also open new facilities, close existing ones and/or adjust their attractiveness. This also formulates a bilevel mixed-integer nonlinear programming problem which we try to solve by combining tabu search with global optimization algorithms. We develop three different tabu search methods and the computational results on a set of problem instances for comparing the performance of the solution methods show that the third tabu search method is the most accurate one, while the second tabu search method is the most efficient solution procedure. Finally, we consider a different facility location problem which takes the customer preferences into account. The facilities are not necessarily identical and customers visit different types of facilities according to some given probability distribution and the maximum distance which they are willing to travel. We formulate a binary linear programming problem and solve it by three procedures that include a Lagrangean heuristic whose solution is improved further using a local search method. Based on the experimental results carried out on a set of problem instances the third solution method is the most efficient one. However, a statistical analysis on the quality of the solutions states that there is no significant difference between the three solution procedures. [less ▲]

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See detailDéfinition du régulon DasR chez Streptomyces coelicolor, un réservoir pour la découverte de nouveaux gènes essentiels à l'induction de la différenciation morphologique et la production de métabolites secondaires
Colson, Séverine ULg

Doctoral thesis (2011)

Ce travail vise à comprendre les mécanismes d’induction du développement chez les Streptomyces. Chez ce genre bactérien, le facteur de transcription DasR a été identifié comme le premier régulateur global ... [more ▼]

Ce travail vise à comprendre les mécanismes d’induction du développement chez les Streptomyces. Chez ce genre bactérien, le facteur de transcription DasR a été identifié comme le premier régulateur global à la charnière entre le métabolisme primaire et le métabolisme secondaire, capable de percevoir l'état nutritionnel de l'environnement et d'adapter en conséquence la réponse des différents processus associés au développement (Rigali et al., 2006 et Rigali et al., 2008). La première ambition de cette thèse de doctorat a été d'évaluer l'ampleur du régulon DasR chez S. coelicolor afin d'obtenir une liste - exhaustive et appuyée par des critère de fiabilité - des gènes ciblés par ce régulateur global. L'hypothèse à la base de ce travail de prédiction était qu'au sein du régulon DasR se trouvaient peut-être des gènes de fonction encore inconnue mais essentiels au développement. Comprendre le rôle de ces protéines pouvait déboucher sur l'élucidation de nouvelles voies d'induction du développement et donc peut-être de nouvelles voies à exploiter pour induire le réveil des gènes cryptiques. La première démarche visant à répondre à ce premier objectif nous a amené à constater les lacunes des programmes web de prédiction des régulons existant, notamment le manque de flexibilité au niveau des critères de recherche et au niveau de l'exploitation des résultats obtenus, ainsi que l'absence de moyen permettant d'estimer la fiabilité de la prédiction. C'est pourquoi, dans un premier temps, nous nous sommes lancés le défi de créer un nouvel outil de prédiction des régulons procaryotiques qui répondrait davantage aux attentes des biologistes. Ce programme, nommé PREDetector (Prokaryotic Regulatory Elements Detector), a été réalisé en collaboration avec le Professeur Louis Wehenkel (Department of Electrical Engineering and Computer Science, Université de Liège) (Hiard et al., 2007). Les caractéristiques et les possibilités offertes par PREDetector sont expliquées et illustrées dans le premier chapitre des résultats. Le second chapitre des résultats - ainsi que l'annexe de cette thèse - sont quant à eux dédiés à l'exploitation de ce programme et la caractérisation de l'ensemble des cibles de DasR prédites chez S. coelicolor. Ensuite, et toujours motivé par un souci de présenter un travail fiable pour d'ultérieures investigations, une comparaison des régulons DasR prédits chez différents streptomycètes et autres actinomycètes (prédictions et démarches détaillées dans l'annexe de thèse), vient appuyer notre définition du noyau dur du régulon DasR - conservon DasR - déduit pour l'organisme modèle S. coelicolor. Enfin, nous passons à l'étape d'utilisation de ces données bioinformatiques avec l'étude de gènes/protéines dont l'expression est dépendante de DasR dans le but de peut-être établir de nouvelles connexions entre le métabolisme primaire et le développement chez la souche modèle S. coelicolor. De manière intéressante, le régulon DasR de S. coelicolor comprend plusieurs gènes codant pour des systèmes de transport ABC de sucre. A l'instar du PTSGlcNAc, ces transporteurs situés à l'interface cellule/environnement peuvent aussi être les senseurs de molécules cruciales pour l'induction du développement. Après le PTSGlcNAc, nous nous sommes donc concentrés sur l'étude du premier transporteur ABC de sucre régulé par DasR - en termes de fiabilité des prédictions et de conservation inter-espèces/-genres -, c'est-à-dire, le système DasABC. Dans le troisième chapitre des résultats nous démontrerons ainsi que DasA est une protéine impliquée dans le processus de différenciation morphologique de S. coelicolor (Colson et al., 2008). [less ▲]

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See detailVERS UNE EXPERTISE HYBRIDE AU SERVICE DU DROIT: LE CAS DES ALIMENTS FONCTIONNELS ET DU DOMMAGE ECOLOGIQUE
Kouembeu Tagne, Jean Jacques ULg

Doctoral thesis (2011)

L’apparition récurrente de phénomènes nouveaux et incertains dans le domaine de l’environnement bouscule de façon permanente les cadres de références législatives et interpelle quant à la place, le rôle ... [more ▼]

L’apparition récurrente de phénomènes nouveaux et incertains dans le domaine de l’environnement bouscule de façon permanente les cadres de références législatives et interpelle quant à la place, le rôle et à l’apport des prétendants à l’expertise. Au sens de la Cour de cassation belge, (Cass 15.02.2006, numéro RC 062F2_7, numéro de rôle P051583F) l’expert judiciaire est un auxiliaire de justice. Il n’est ni mandataire, ni préposé des parties. Il assiste le juge, sans empiéter sur la fonction de juger qui est confiée à ce dernier. L’expert est alors appelé à traduire des preuves scientifiques en preuves factuelles destinées à des profanes de sa discipline que sont les juges. Dans ce cas de figure, l’expertise participe de la bonne organisation judiciaire, assure une base de connaissance solide à l’élaboration des décisions judiciaires et se présente comme un partenaire qui pénètre dans le cœur du droit. L’expertise est considérée de la même manière quand dans les processus législatifs elle s’adresse à des parlementaires ou quand elle est convoquée par des politiques voire par le public. Considérée sous cet angle, l’expertise se présente comme un savoir limité aux faits, et non une connaissance discutable, en train de se construire. Cette thèse examine comment, dans des domaines complexes caractérisés par l’incertitude, le savoir objectif n’existe que comme construction. L’expertise n’est plus spécifique à une branche, elle est hétérogène, elle est hybride. Plus fondamentalement, cette expertise est appelée à articuler et à intégrer plusieurs objectivités à la fois, qu’elles soient scientifiques, socio-économiques, sanitaires ou politiques. Cette thèse montre à partir des cas de la réglementation sur les aliments fonctionnels d’une part et celui du dommage écologique d’autre part, comment les cadres juridiques sont investis par des scientifiques, des publics, des juristes, des associations, des politiques, des industriels, etc., et comment ceux-ci contribuent en retour à la modification de ces cadres. Si le droit se singularise par son devoir de qualification, c’est-à-dire, celui qui lui permet d’établir une distance avec les autres disciplines, avec le monde extérieur, la complexité des phénomènes environnementaux invite aujourd’hui à aller au-delà des cloisonnements du raisonnement juridique. En ce sens, cette thèse vise à éclairer la question essentielle suivante : comment le droit peut-il intégrer plusieurs objectivités dans un processus d’élaboration de la norme environnementale ? [less ▲]

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See detailContribution to the study of semiochemical slow-release formulations as biological control devices
Heuskin, Stéphanie ULg

Doctoral thesis (2011)

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been widely considered within various integrated pest management (IPM) strategies. In the present thesis ... [more ▼]

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been widely considered within various integrated pest management (IPM) strategies. In the present thesis, two sesquiterpenoids, E-β-farnesene and E-β-caryophyllene, were formulated for their related properties as aphid enemy attractants. E-β-farnesene, the alarm pheromone of many aphid species, was also identified as a kairomone by attracting and inducing oviposition of aphid predators (Episyrphus balteatus De Geer (Diptera: Syrphidae)) and by attracting aphid parasitoids (Aphidius ervi Haliday (Hymenoptera: Braconidae)). E-β-caryophyllene was identified as a potential component of the aggregation pheromone of the Asian ladybird, Harmonia axyridis Pallas, another aphid predator. The two products were purified from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae) for E-β-farnesene and E-β-caryophyllene, respectively. Natural and biodegradable slow-release formulations were then investigated in order to deliver these molecules on crop fields for a long period of time as biological control devices. Due to their sensitivity to oxidation, both sesquiterpenes needed to be protected from oxygen degradation. For this purpose, alginate – hydrophilic matrix with low oxygen permeability – was used as polymer for the formulations: the main objective was to deliver semiochemical substances in the air in a controlled way. Consequently, a careful selection of alginates was realised. Formulated beads showed different structural and encapsulation properties depending on various formulation factors. Alginate formulations were characterized by texturometry and by confocal microscopy in order to observe the distribution of semiochemicals in alginate network. The last step of alginate bead characterisation consisted in studying release rate of semiochemicals in laboratory-controlled conditions by optimised trapping and validated Fast-GC procedures. Finally, the efficiency of formulations as aphid predator (Syrphidae) and parasitoids (A. ervi) attractants was demonstrated by field trapping and olfactometry experiments. [less ▲]

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See detailLa qualité de vie dans la maladie d'Alzheimer et les syndromes apparentés
Missotten, Pierre ULg

Doctoral thesis (2011)

La question de la qualité de vie dans la démence, envisagée par rapport au patient, constitue l’objet d’étude de ce travail de thèse. Plus précisément, la première partie théorique du présent travail fait ... [more ▼]

La question de la qualité de vie dans la démence, envisagée par rapport au patient, constitue l’objet d’étude de ce travail de thèse. Plus précisément, la première partie théorique du présent travail fait le point sur les connaissances actuelles dans la littérature sur la qualité de vie. Cette dernière est appréhendée sous la double perspective conceptuelle et méthodologique. L’état des lieux dans la démence constitue, pour chacune des différentes caractéristiques conceptuelles et méthodologiques envisagées, le dernier élément qui est aussi le plus détaillé. Il est précédé d’un point centré sur la littérature gérontologique qui, lui-même, est devancé par une petite recherche focalisée sur la littérature « générale » (essentiellement issue de la littérature centrée sur des populations adultes). En ce sens, le développement de chaque caractéristique, tant conceptuelle que méthodologique, se fait donc en trois temps : général, gérontologie et démence. Ces trois phases témoignent d’une présentation allant dans le sens du général au spécifique et du moins développé au plus développé. Pour clôturer la première partie théorique, un recensement des outils de qualité de vie (instruments et méthodes d’observation directe) est présenté. En accord avec ce qui vient d’être énoncé pour les caractéristiques conceptuelles et méthodologiques, ce développement des outils est surtout détaillé pour la démence. Ensuite, les objectifs du travail de thèse sont développés pour commencer la partie expérimentale. Ils sont suivis par la présentation des quatre articles scientifiques. Ceux-ci sont centrés sur l’étude transversale et longitudinale (follow-up de 2 ans) de la qualité de vie et des principaux paramètres sociodémographiques (âge, sexe, lieu de résidence) et cliniques (fonctionnement cognitif, dépendance, troubles psychologiques et comportementaux, stade évolutif) de patients déments situés à tous les stades de l’évolution démentielle. De manière générale, les résultats démontrent que les patients déments sont capables de maintenir un niveau de qualité de vie acceptable. Cette constatation a notamment été établie sur base de la comparaison de la qualité de vie de ces patients avec celle de patients présentant des troubles cognitifs légers ainsi que des personnes âgées « contrôles ». Le niveau de qualité de vie des sujets déments est influencé par les variables cliniques dont l’impact a tendance à augmenter avec le temps. Toutefois, une part importante de la variance reste non expliquée, ce qui démontre l’influence d’autres variables. Enfin, le profil de qualité de vie en fonction du lieu de résidence et du fonctionnement cognitif montre des périodes de stabilisation et de détérioration. Cette observation permet 1) d’affiner la question du lien entre qualité de vie et paramètres cliniques ; 2) de démontrer l’absence de diminution strictement linéaire de la qualité de vie en fonction de l’état cognitif ; 3) de questionner le postulat d’une qualité de vie nécessairement meilleure au domicile par rapport à l’institution. Suite à la présentation de ces articles, le présent travail se centre sur une discussion générale. Celle-ci débute par une synthèse intégrée des résultats dégagés au sein des quatre articles. Elle se poursuit par le dégagement des principaux points conceptuels et méthodologiques avant de se terminer par une réflexion clinique et scientifique basée sur les résultats des articles et les principaux points théoriques abordés. Aussi, la présence d’un niveau de qualité de vie non catastrophique pour les patients déments est mis en parallèle avec les notions de buts et de priorités retrouvées dans la prise en charge actuelle des patients déments mais également avec les concepts de personnalité et de citoyenneté ainsi qu’avec les théories du vieillissement réussi et les stratégies d’adaptation. Enfin, ce travail se clôture par une conclusion générale. [less ▲]

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See detailFluorine in the atmosphere: Inorganic fluorine budget and long-term trends based on FTIR measurements at Jungfraujoch
Duchatelet, Pierre ULg

Doctoral thesis (2011)

High resolution solar spectra are routinely recorded since more than two decades by the University of Liège at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m ... [more ▼]

High resolution solar spectra are routinely recorded since more than two decades by the University of Liège at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m asl) with Fourier Transform Infrared (FTIR) spectrometers. Over the last years, major improvements have been implemented in the algorithms used to retrieve the abundances of atmospheric constituents accessible to the FTIR technique. Now, in addition to total column, information on the vertical distribution of the target gas is often available, allowing producing partial column data sets. We take advantage of these improvements to generate and characterize long-term total and partial columns time series of some important inorganic fluorinated trace gases deduced from FTIR measurements performed at Jungfraujoch. First, our investigations on hydrogen fluoride (HF) indicate that the adoption of a Galatry line shape model for this species significantly improves the fitting quality of the retrievals. The sensitivity of our FTIR measurements to HF inversions in three distinct regions that range from the low to the high stratosphere is confirmed thanks to products derived from two satellites and from two numerical models. We further demonstrate that the HF seasonal variations that occur in the low stratosphere are mainly responsible for the seasonal cycle observed in our HF total column time series. We have also developed an original multi-spectrum multi-window retrieval strategy allowing to derive, for the first time, some information on the vertical distribution of carbonyl fluoride (COF2) from ground-based FTIR measurements. After comparison with model data, our COF2 and HF FTIR datasets are combined to assess the atmospheric inorganic fluorine burden Fy. A trend analysis of our HF, COF2 and Fy time series is then performed for four different time periods spanning the 1985-2010 time interval. While we observe a recent stabilization for HF, corresponding COF2 data show a significant rise, after a period of significant reduction in its accumulation rate. This is probably ascribable to the combination of the decrease of its main source gas CFC-12 with the increase of the substitute product HCFC-22. However, this increase in the COF2 rate of change does not significantly impact the Fy trend, which is essentially driven by the change in HF. In addition, we show that the partitioning between the two major fluorine reservoirs HF and COF2 has not changed since the beginning of this century. Together, they account for around 95% of total inorganic fluorine in the atmosphere. Finally, we study the long-term evolution of carbon tetrafluoride (CF4), for the first time from ground-based FTIR measurements. The trend analysis of our time series indicates a slowing, initiated during the nineties, in the CF4 growth rate despite the fact that the absolute loading of this compound is still increasing. Our linear accumulation rates are consistent with those deduced from space or surface measurements. [less ▲]

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See detailEtude de l’évolution de l’état de surface de matériaux optiques sous bombardement ionique à faible énergie
Gailly, Patrick ULg

Doctoral thesis (2011)

In this work the roughness and topography evolution of optical materials sputtered with low energy ion beam (≤1 keV) has been investigated. These materials (bulk or thin layer) are used in the ... [more ▼]

In this work the roughness and topography evolution of optical materials sputtered with low energy ion beam (≤1 keV) has been investigated. These materials (bulk or thin layer) are used in the manufacturing of mirrors for scientific (ground or space) instruments or for other optical applications. In the first part of the work, the roughness evolution of optical surfaces under sputtering has been investigated in the frame of the industrial process known as Ion Beam Figuring. This technique consists in removing shape errors on optical surfaces with a low energy ion beam (≤1 keV). One disadvantage of this process is a potential increase of roughness for surfaces under treatment. The roughness evolution of some materials relevant to the optical industry has been accurately characterized as function of etching depth down to 5 µm. These sputtering experiments have been carried out at normal incidence, mainly with argon ions (but also in a lesser extent with krypton and xenon ions), ion current density of ~1 mA/cm2 and ion beam energy ranging from 200 eV to 1000 eV. The roughness evolution under sputtering is low for materials with amorphous (glass, electroless nickel), monocrystalline (silicon) or even polycrystalline structure (CVD silicon carbide, PVD gold or nickel film), whereas it is considerably more important for some other metallic materials such as electroplated nickel and aluminium. This work has shown small differences in the roughness evolution of CVD silicon carbide as function of the ion beam energy. The roughness increase is faster at low ion energy (<500 eV) than at higher ion energy (650-1000 eV). The grain structure of this material is less revealed at higher energy, which is supposed to be due to a larger amorphization of the sputtered layer in this case. The influence of the ion mass on CVD silicon carbide and gold films on nickel substrates has been also illustrated. Our measurements have been also compared to scaling laws. Various growth and roughness exponents have been found, sometimes rather different from those foreseen by the KPZ equation. In the second part, we focus on periodically modulated structures (ripples) which developed on many solids when sputtered by an off-normal ion bombardment. In this work, we first observed these ripples on gold films deposited on electroplated nickel (materials used as reflective surfaces for X-ray space telescope) sputtered at grazing incidence. We studied the influence of sputtering parameters (ion beam incidence angle, energy and flux) on the characteristics of ripples induced on gold and silver thin film (~0.2 µm). Ion-induced ripples have also been observed on CdS, an interesting semiconductor crystal for optical applications. The ripples orientation and dimensions (spatial wavelengths from 0.13 µm to 0.29 µm) have been confronted to the Bradley-Harper (B-H) linear model. We used the SRIM software to evaluate the deposited energy and the surface tension coefficient distributions. Our results can be in great part explained by the current theories (Bradley-Harper, Makeev) on morphology of ion-sputtered surfaces. These results can be summarized hereunder: • Clear development of ripples for angle of incidence equal or higher than 60° on gold film and 70° on silver film. • In this work the ripples wave vector is always perpendicular to the ion beam direction for all angles, whereas the change in ripple orientation beyond a critical angle is usually reported in literature. This is a due to the different shape of the energy distribution function for our sputtering conditions. • Different regimes for roughness and topography evolution (grains, ripples) have been observed in function of the angle of incidence. 3 different areas can be distinguished, as predicted by Makeev non-linear model. • The diminution of ripple wavelength with ion energy shows that thermal diffusion is the main relaxation mechanism. [less ▲]

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See detail'D’abord sa manière étoit gottique'. L'œuvre peint de Bernard van Orley jusqu'au début des années 1520
Galand, Alexandre ULg

Doctoral thesis (2011)

Les années 1510 et 1520 apparaissent comme un moment crucial pour l’introduction de la Renaissance dans les anciens Pays-Bas. Or, cette période coïncide avec la première période d’activité de Bernard van ... [more ▼]

Les années 1510 et 1520 apparaissent comme un moment crucial pour l’introduction de la Renaissance dans les anciens Pays-Bas. Or, cette période coïncide avec la première période d’activité de Bernard van Orley, un témoin majeur de cette époque de transition. Jusqu’à présent, la recherche a surtout envisagé l’artiste par le prisme de ses magnifiques tapisseries. De la fin de la première décennie du 16e siècle à 1521 où il signe le monumental Polyptyque de Job et de Lazare (Bruxelles, MRBAB/KMSKB, Inv. 1822), l’artiste a pourtant élaboré un œuvre peint de plus en plus perméable aux formes en provenance de la péninsule italienne. Ce changement de perspective a-t-il entraîné des différences importantes en termes de pratiques d’atelier ? Comment peuvent être caractérisées de manière précise les œuvres constituant le noyau dur d’un catalogue aux frontières mouvantes ? En quoi les documents d’archives peuvent-ils donner un nouvel éclairage sur l’activité de l’artiste ? Ces questions sont au centre d’un travail qui se donne pour ambition de renouveler la vision de la peinture de Bernard van Orley, domaine jusqu’à aujourd’hui négligé. [less ▲]

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See detailEtude expérimentale de la cristallochimie et de la stabilité des phosphates à structure fillowite
Rondeux, Mélanie ULg

Doctoral thesis (2011)

Les minéraux du groupe de la fillowite sont des phosphates sodiques de manganèse, de fer, de magnésium et de calcium. On rencontre ces phosphates essentiellement dans les pegmatites granitiques, en ... [more ▼]

Les minéraux du groupe de la fillowite sont des phosphates sodiques de manganèse, de fer, de magnésium et de calcium. On rencontre ces phosphates essentiellement dans les pegmatites granitiques, en contextes métamorphiques, mais aussi dans certaines météorites. A l’heure actuelle, on compte cinq minéraux appartenant à ce groupe ; la fillowite sensu stricto [Na2CaMn7(PO4)6], la chladniite [Na2CaMg7(PO4)6], la galileiite [Na2Fe2+8(PO4)6], la johnsomervilleite [Na2CaFe2+7(PO4)6] et la stornesite-(Y) [(Y,Ca)□2Na6(Ca,Na)8(Mg,Fe)43(PO4)36]. Ces minéraux cristallisent dans le système rhomboédrique (groupe spatial R ) et présentent une maille cristalline de très grande taille (a = 15,28 Å, c = 43,51 Å, Z = 18) contenant 756 atomes dont 45 sont non équivalents. Le premier but de ce travail a été d’obtenir de nouvelles données sur la cristallochimie des minéraux du groupe de la fillowite, et de déterminer les limites d’incorporation de différents cations dans cette structure. La synthèse par voie sèche a été utilisée, à diverses températures (entre 650 et 970°C), lors des essais d’insertion des cations monovalents (Li+, Ag+ et K+), des cations bivalents (Mg2+, Fe2+, Zn2+, Ni2+, Ca2+ et Cd2+) et des cations trivalents (Fe3+, Al3+, Y3+, Cr3+ et Sc3+). Les cations monovalents sont toujours présents dans les minéraux du groupe de la fillowite. Nos résultats confirment cette observation et indiquent que, à l’exception de Ag+ qui peut totalement se substituer à Na+, les autres cations monovalents (Li+ et K+) ne rentrent que très difficilement dans la structure fillowite. Concernant les cations bivalents, les résultats de nos recherches montrent que c’est le manganèse qui s’incorpore le plus facilement dans la structure fillowite. En effet, la synthèse des phosphates de compositions Na2Mn8(PO4)6 ou encore Na2CaMn7(PO4)6, isotypes à la fillowite, est très commode. De plus, les analyses chimiques à la microsonde électronique des fillowites, obtenues par voie hydrothermale dans les systèmes Na-Mn-Fe2+-Mg-(PO4) et Na-Ca-Mn-Fe2+-Mg-(PO4), se localisent essentiellement dans la partie riche en Mn des diagrammes Mn-Fe-Mg. Nous avons également prouvé expérimentalement que d’autres cations bivalents comme le magnésium, le calcium et le cadmium peuvent également s’y introduire assez aisément, à l’opposé du zinc et du nickel qui forment préférentiellement des phases orthorhombiques ou de l’alluaudite. Finalement nos données montrent que le fer ferreux se substitue au manganèse, jusqu’à la composition Na2,244(Fe2+3,791Mn3,172Fe3+0,610)(PO4)6 obtenue à 600°C / 1 kbar. La structure fillowite ne semble pas affectionner les cations trivalents. Nos données corroborent cette observation car il est plus aisé d’insérer des cations bivalents que des cations trivalents, à l’exception de Sc. En effet, le scandium, dont le rayon ionique est le plus proche de celui de Mg2+, s’incorpore bien dans la structure fillowite. L’insertion de Al3+ dans cette structure se révèle également assez facile, comme en témoigne la détection de composés à structure fillowite obtenus sans impuretés dans les échantillons de compositions de départ : Na2(Mn7,4Al0,4)(PO4)6 et Na2Ca(Mn6,25Al0,5)(PO4)6. Enfin, ce sont Fe3+, Cr3+ et Y3+ qui entrent le plus difficilement dans cette structure. La substitution de Mn2+ par Fe3+ ou Cr3+ dans les systèmes étudiés en voie sèche induit immédiatement l’apparition de composés à structure alluaudite en association avec les phosphates à structure fillowite. Des analyses chimiques à la microsonde électronique indiquent toutefois que Fe3+ s’incorpore en faible teneur dans la structure fillowite. Le second objectif de ce travail a été d’appliquer les techniques de synthèse hydrothermale afin de mieux cerner la stabilité des minéraux du groupe de la fillowite. Dans ce but, les systèmes Na-Mn-Fe2+-Mg-(PO4) et Na-Ca-Mn-Fe2+-Mg-(PO4) ont été investigués, à des températures comprises entre 400 et 700°C (1 kbar). Des phosphates à structure fillowite sont formés, sans impureté, à toutes les températures étudiées, à partir des mélanges initiaux dépourvus de fer. L’incorporation du fer implique immédiatement l’apparition d’alluaudite et de sarcopside, alors que la marićite cristallise comme phase supplémentaire pour les compositions très riches en fer. Le contenu de ce dernier dans les composés à structure fillowite augmente entre 400 et 600°C, puis diminue légèrement entre 600 et 700°C (1 kbar). La composition de ces phosphates, obtenus à 600°C / 1 kbar, est très proche de celles des johnsomervilleites naturelles de Loch Quoich (Ecosse) et de Kiluli (Rwanda) indiquant que ceux-ci auraient pu se former dans des conditions similaires. Pour le mélange initial Na2Fe2+8(PO4)6, les phosphates à structure fillowite sont absents à 1 kbar, alors qu’ils apparaissent timidement lors des synthèses réalisées à 3 kbar. Ces résultats démontrent le rôle essentiel joué par la pression sur l’incorporation du fer dans la structure fillowite. [less ▲]

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See detailParameter identification for biological models
Fey, Dirk ULg

Doctoral thesis (2011)

This thesis concerns the identification of dynamic models in systems biology. and is structured into two parts. Both parts concern building dynamic models from observed data, but are quite different in ... [more ▼]

This thesis concerns the identification of dynamic models in systems biology. and is structured into two parts. Both parts concern building dynamic models from observed data, but are quite different in perspective, rationale and mathematics. The first part considers the development of novel identification techniques that are particularly tailored to (molecular) biology and considers two approaches. The first approach reformulates the parameter estimation problem as a feasibility problem. This reformulation allows the invalidation of models by analysing entire parameter regions. The second approach utilises nonlinear observers and a transformation of the model equations into parameter free coordinates. The parameter free coordinates allow the design of a globally convergent observer, which in turn estimates the parameter values, and further, allows to identify modelling errors or unknown inputs/influences. Both approaches are bottom up approaches that require a mechanistic understanding of the underlying processes (in terms of a biochemical reaction network) leading to complex nonlinear models. The second part is an example of what can be done with classical, well developed tools from systems identification when applied to hitherto unattended problems.In particular, part two of my thesis develops a modelling framework for rat movements in an experimental setup that it widely used to study learning and memory.The approach is a top down approach that is data driven resulting in simple linear models. [less ▲]

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See detailDes guerres en Italie avant les Guerres d'Italie. Les entreprises militaires françaises dans la Péninsule à l'époque du Grand Schisme d'Occident
Masson, Christophe ULg

Doctoral thesis (2011)

Si la guerre de Cent Ans stricto sensu, est depuis des années l'objet de recherches de tout premier plan, la question des expéditions françaises en Italie à l'époque du Grand Schisme d'Occident était ... [more ▼]

Si la guerre de Cent Ans stricto sensu, est depuis des années l'objet de recherches de tout premier plan, la question des expéditions françaises en Italie à l'époque du Grand Schisme d'Occident était restée vierge de toute étude de synthèse, à tout le moins sur le plan qui semble pourtant le plus évident, celui de la guerre, et ce alors même que les implications politiques de ces mêmes guerres italiennes sont étudiées depuis aujourd'hui plus d'un siècle. Au croisement des sources – sources narratives et documents d'archives se sont révélés être le socle sur lequel s'est progressivement construite notre synthèse puisqu'au caractère lacunaire des premières en terme de fiabilité ou de chronologie a fait pièce la précision des secondes qui trouvaient pour leur part dans la confrontation avec les chroniques les éléments de nature à enrayer l'aridité des relevés financiers – fait écho celui des approches, que nous avons souhaitées multiples, de notre sujet d'études. Pour appréhender le fait militaire, nous avons privilégié une vision globalisante, eu égard au fait que, à nos yeux, l'armée représentait un tout qui se doit d'être étudié de la sorte. Les divers éléments qui la composent étant interdépendants, on ne peut connaître l'un sans envisager l'autre. Il ressort de cette approche plurielle plusieurs observations. Alors que l'Europe se cliche au gré des intérêts politiques et spirituels en obédiences rivales, l'on aurait pu s'attendre à ce que des princes français, traditionnellement favorables à la papauté d'Avignon, deviennent les champions des prélats des bords du Rhône. Or, il n'en fut rien. Ce qui intéressa au premier chef les ducs d'Anjou fut non de déposer celui qu'il tenait pour un usurpateur et d'établir le successeur de saint Pierre pour lequel ils avaient opté sur le trône de Rome mais de profiter des ressources financières de la papauté, considérées alors, avec le trésor du roi de France, comme les plus massives de l'Occident. De la même façon, les ressources du duc d'Orléans et celles du roi de France furent, en toute logique, très largement sollicitées par les lieutenants de ceux-ci. Mais, à cette occasion encore, on constate une indépendance certaine des bénéficiaires vis-à-vis de leurs bailleurs de fonds. La mission qui leur est confiée offre un cadre relativement lâche à leurs actions, cadre qui, joint à l'éloignement géographique, facilite l'exercice d'un pouvoir des capitaines ouvertement personnel. Les actions menées en Italie se trouvent tout à fait différer des usages en cours lors de la guerre qui opposait la France à l'Angleterre. Depuis Charles V, en effet, les armées françaises s'étaient vues ordonner l'abandon de la charge de cavalerie au profit d'options tactiques mieux à même de contrer une infanterie adverse qui s'était signalée lors des sanglantes batailles de Crécy et de Poitiers. En Italie, au contraire, si les compagnies fleurdelysées ressemblaient par la taille à leurs homologues cisalpines, leur aspect les en faisait parfaitement différer. La prééminence est à nouveau le fait d'hommes d'armes montés. Le basculement est donc complet et rapide de la part de guerriers qui s'adaptent d'autant plus rapidement à leur nouvel ennemi que celui-ci se révèle être un fervent adepte du choc frontal, du moins lorsqu'il accepte le combat. C'est d'ailleurs un trait marquant des opérations françaises que de n'avoir que rarement produit de grandes batailles. Au vrai, les Italiens s'efforçaient le plus souvent d'éviter tout affrontement d'importance afin de tirer profit de leur établissement dans le royaume de Naples ou dans la République de Gênes. Partant, les Français organiseront leurs campagnes autour d'un objectif prioritaire, la soumission de la capitale adverse et auront donc recours à des moyens moins typiquement « chevaleresques » pour assurer le triomphe de leur cause. Si Louis Ier d'Anjou n'a visiblement pu compter que sur une faible artillerie, ceux qui, à sa suite, prirent le chemin de l'Italie ne semblent pas avoir négligé cette composante de plus en plus importante de l'art de la guerre. D'autres moyens pour emporter des places fortes furent mis en œuvre, qui tous s'éloignaient un peu plus de la morale traditionnellement défendue par cette classe sociale particulière qu'était la chevalerie. Or, ces pratiques étaient loin d'être étrangères aux capitaines royaux et ducaux. L'idée de l'honorable et pur chevalier parangon de vertu confronté à des réalités italiennes qu'il ne peut comprendre car trop ignobles ne résiste pas à l'examen attentif des faits. Les armées médiévales – de terre ou de mer – tiraient évidemment leur puissance de leur importance numérique. Par suite, ce sont les chefs de guerre à la tête des plus nombreuses compagnies qui reçurent le commandement de l'ensemble des troupes. Le recrutement en cascade – les fidèles d'un seigneur conduisant à leurs côtés certains de leurs fidèles et ainsi de suite – explique que, contrairement, une fois encore, à ce que l'on aurait pu croire, le service d'Italie ne s'est pas révélé un accélérateur de carrière chez les gens d'armes. Leur présence dépendait plus de liens personnels les unissant à un chef de guerre que de relations de service ou de vassalité les attachant au souverain commanditaire de l'entreprise. Nulle surprise donc à ce que ce dernier ne juge pas nécessaire de les récompenser à la fin de leur mission. Au contraire, ce sont les techniciens, gens de finances et de lettres, qui bénéficièrent de promotions à leur retour d'Italie. La guerre dans la Péninsule n'était qu'une étape de plus dans la carrière d'un homme d'armes alors qu'elle prouvait les capacités des « petites mains » de l'armée à affronter des situations auxquelles l'on ne pouvait se préparer. Si la délégation de pouvoir est importante, il n'en reste pas moins que l'on assiste tout au long de ces campagnes à la négation de la personnalité du capitaine dans le domaine pourtant si important des symboles politiques. L'armée demeure ainsi un instrument de pouvoir aux mains du souverain. Au-delà de l'aspect spécifiquement politico-militaire, elle exprime l'excellence de ce dernier, qu'il s'agisse des ducs d'Anjou et d'Orléans ou du roi de France, lequel prouve par le succès des armes et la qualité – sociale aussi bien qu'esthétique – de son armée la valeur et la justesse de ses prétentions. Au vrai, si c'est la noblesse qui, logiquement, compose les armées françaises et occupe les principales charges de gouvernement, elle est subjuguée par l'État qu'elle sert. Elle en retire un prestige certain mais renonce aussi, simultanément, à son indépendance. Ici encore, l'état moderne en construction se bâtit sur et grâce à une aristocratie relais des intérêts ducaux ou royaux. De la même façon, la présence de Français au sein de ces administrations locales trahit l'importance prise par les liens sociaux dans l'exercice du pouvoir et sa délégation. Ce sont leur proximité et leur amitié qui font des lieutenants du capitaine les officiers du roi. La fidélité personnelle intervient donc comme ciment d'un pouvoir étatique. La noblesse, bien qu'elle soit en Italie moins soumise au pouvoir royal en Italie qu'en France, constitue le véritable cœur de l'armée, tout comme cette dernière est le noyau de l'état princier que l'on développe outremonts grâce au cadre fourni par le modèle royal. [less ▲]

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See detailInnovative strategies for the control of apple scab (Venturia inaequalis [Cke.] Wint.) in organic apple production
Jamar, Laurent ULg

Doctoral thesis (2011)

The aim of this thesis, conducted over six growing seasons (2003-2008), is to define new measures for reducing the use of fungicides and in particular, copper fungicides, for the control of apple scab (V ... [more ▼]

The aim of this thesis, conducted over six growing seasons (2003-2008), is to define new measures for reducing the use of fungicides and in particular, copper fungicides, for the control of apple scab (V. inaequalis) in organic apple production. Special emphasis is put on primary scab infection control during spring season. An original approach is proposed for defining a specific spray timing involving spraying during the infection processes, especially before fungal penetration, determined by the RIMpro software warning system. This ‘during-infection’ spray strategy allows reducing from 30 to 50% the amount of fungicide usually used for effective apple scab control, on high scab-susceptible cultivars. The field study shows that six alternative products (e.g., potassium bicarbonate and lime sulphur), among 60 products tested, have the potential to reduce copper use. However, copper use, even with low doses, seems to be still necessary in presence of scab-susceptible cultivars. The results obtained in these experiments could not be attributed to the specific technical performances of the tunnel sprayer used, which however, offer valuable environmental benefits. On the basis of the present study, the organic management system seems a good farming approach for maintaining soil quality with regard to biological indicators. This work shows and draws attention to the fact that (i) planting cultivars with polygenic scab-resistance traits, (ii) increasing emphasis on sanitation practices aimed at reducing initial inoculum in autumn, and (iii) applying an accurate spray strategy in spring, as defined in the present study, are the three most promising approaches for substantial further reductions in protection products fully compliant with international organic crop production standards. [less ▲]

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See detailOptimisation contrainte et non-contrainte par régions de confiance avec approximations locales quadratiques
Walmag, Jérôme ULg

Doctoral thesis (2011)

This work deals with optimisation problems in which the numerical cost associated with the evaluation of the target function and/or of the constraints is large; the number of calls to these functions by ... [more ▼]

This work deals with optimisation problems in which the numerical cost associated with the evaluation of the target function and/or of the constraints is large; the number of calls to these functions by the optimisation algorithm should therefore be kept as small as possible. The first part of the work is about globalisation by trust regions where the objective function and the constraints are replaced by a local approximation, easier to use, in a certain region of confidence. Different types of local approximations are introduced but the main part of the work deals with quadratic approximations. The theoretical aspects of the global convergence of trust regions methods are also presented. One of the applications considered in this work is the parametrical identification of a dynamical model with respect to experimental measurements. This identification can be expressed in the form of an unconstrained optimisation problem. For the practical implementation of the identification algorithm, the derivative of the objective function is required, which asks for the derivation of the underlying model. An algorithm, named Trust, has been implemented: it is a trust region method of quasi-Newton type which uses quadratic local approximations. The choice of the differentiation method is analysed in details in relation with its influence on the rate of convergence. A brand new update strategy of the trust region radius is also introduced. The trust region radius is a parameter that measures the size of the trust region around the current iterate. The new approach relies on the identification and appropriate handling of so-called “too successful iterations” that lead to a much more important reduction of the function objective than predicted by the local approximation. This approach goes with a significant improvement of the performances of the algorithm. Constrained optimisation is then considered using sequential quadratic methods. A fully effective algorithm for the resolution of quadratic convex sub-problems with quadratic constraints is introduced. This original method, named UVQCQP, makes use of an exact non-differentiable penalty function to addresses the constrained optimisation problem. The algorithm relies on a decomposition of the variable space into three orthogonal subspaces: a first subspace taking into account bound constraints, a second one in which the objective function is continuously derivable and a third one with slope discontinuities. The performances of this algorithm are further improved by the implementation of a fast mode taking into account the second order corrections. Eventually, the UVQCQP algorithm is applied within the framework of sequential algorithms of quadratic programming with quadratic constraints: its advantages are demonstrated through some examples. The numerical tests carried out reveal very encouraging prospects. [less ▲]

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See detailLa représentation documentaire des années de plomb allemandes (1970-1979): de la contrinformation au mélancolique
Hamers, Jérémy ULg

Doctoral thesis (2011)

Comment représenter un ensemble d’évènements affectés par leur inaccessibilité, la polarisation extrême du contexte qu’ils contribuent à mettre en place, et une censure à la fois morale et financière ... [more ▼]

Comment représenter un ensemble d’évènements affectés par leur inaccessibilité, la polarisation extrême du contexte qu’ils contribuent à mettre en place, et une censure à la fois morale et financière ? Telle était la question de départ de notre recherche doctorale, à laquelle nous avons soumis un corpus de films documentaires allemands traitant des événements de la crise terroriste des années septante, et réalisés entre 1970 et 1979. Un rappel chronologique de quelques évènements saillants des années de plomb allemandes nous a permis d’examiner d’abord les multiples liens et interactions entre terrorisme allemand et représentation. L’analyse de l’usage des médias par les terroristes et l’examen de quelques représentations produites par les médias, ont révélé un double lien symbiotique entre acte terroriste et discours médiatique : intrication de l’événement et de sa représentation en vertu de laquelle certaines images s’érigent d’abord en emblèmes des évènements avant de s’y substituer totalement ; chassé-croisé de représentations terroristes, étatiques et médiatiques, qui révèle que les productions audiovisuelles des terroristes et les représentations produites par l’Etat appartiennent en réalité à un seul et même grand réseau de représentations, sémantiquement violentes, dont les principaux moteurs sont la citation et le détournement ainsi que le remplissage de décors vides dans lesquels se sont déroulés des événements révolus. Cet état de fait compromet a priori toute approche documentaire indépendante des événements. La suite de notre étude a dès lors été consacrée à la recherche d’une forme documentaire qui serait en mesure d’échapper à ce grand réseau de représentations. Cette recherche a d’abord abouti à l’analyse de six documentaires – totalement ignorés par la littérature scientifique pour la plupart – issus d’écoles de cinéma et de groupes de vidéastes militants. Ces films ont été réunis au nom de leur capacité structurelle à échapper à la censure financière et morale de l’époque. L’analyse de ces œuvres nous a permis d’identifier quelques modes de représentation qui tous peuvent contribuer à l’élaboration d’un regard sur le réel, affranchi partiellement de l’irreprésentabilité de la crise terroriste et du réseau de représentations qu’elle contribue à mettre à place. Mais il est également apparu que ces œuvres reproduisent des logiques narratives et informationnelles héritées des médias, qui compromettent in fine l’existence d’un regard non polarisé sur les événements. La suite de notre étude s’est alors focalisée sur le film collectif L’Allemagne en automne. L’analyse de différentes formes de signatures auctoriales a révélé d’abord que si le film est à considérer comme une œuvre signée en groupe, sa signature « désindividualisante » entre aussi en concurrence directe avec un ensemble de marqueurs d’énonciation individuelle. En résulte l’oscillation d’un auteur, reconnaissable et anonyme, proposant de la sorte un nouveau lieu du discours. Enfin, nous nous sommes penchés sur les mises en scène des séquences du film. Notre analyse a mis en évidence que les évènements précis de l’automne '77 agissent seulement comme des rappels visuels d’un contexte particulier. Ce contexte anxiogène nous a amené à conclure provisoirement à l’échec de l’auteur : incapable de se libérer du camp qui lui est attribué a priori, il reproduit les comportements et regards de ses « adversaires » (point de vue du « policier embusqué, etc.). Conscient de cette paralysie, l’auteur est pourtant aussi le premier créateur de ces manifestations d’échec. En ce sens, il ne subit pas la crise dans laquelle le précipite l’Automne Allemand, mais il la (re)met en scène. Le produit de cette lucidité, de cette conscience est le mélancolique : une représentation ou un discours produits par un sujet conscient mettant en abyme le retournement contre soi, la perte de soi qui lui paraît inéluctable dans le contexte des années de plomb. [less ▲]

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See detailProphétisme, hétérodoxie et dissidence. L’imaginaire kimbanguiste en mouvement
Melice, Anne ULg

Doctoral thesis (2011)

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See detailMolecular characterization of the host-pathogen relationships involved during an infection of GF-305 peach trees by the Peach latent mosaic viroid (PLMVd)
Parisi, Olivier ULg

Doctoral thesis (2011)

The Peach latent mosaic viroid (PLMVd) infects peach trees in all production areas. This pathogen is responsible of direct and indirect crop losses. However only a few data are available as regards on one ... [more ▼]

The Peach latent mosaic viroid (PLMVd) infects peach trees in all production areas. This pathogen is responsible of direct and indirect crop losses. However only a few data are available as regards on one hand the determinant of pathogenicity of this viroid and on the other hand the resistance mechanisms of plants against this pathogen. The original approach of this work was to give the foundation of this double characterization. Firstly, the role of the P8 pseudoknot, present in every sequenced PLMVd, was studied by directed mutagenesis. Secondly, the molecular response of different peach trees infected by different variants was evaluated by the use of the cDNA-AFLP. The main objective of this thesis was to identify a metabolic pathway implicated in the plant defence against the PLMVd. In the term of this work, it seemed that the P8 pseudoknot was implicated either in the stability or in the replication of the viroid into the infected cells. Indeed, the inoculated variant (with a destabilized pseudoknot) has shown a reduced replication during the cultural season. In spite of the presence of the mutated variant in the plants, no symptom was observed on the peach tree leaves. However, we cannot conclude if this absence of symptom is due to the low viroid quantity either to an implication of the pseudo-knot in the pathogenicity of the PLMVd. The characterization of the gene expression in the infected peach trees has allowed to highlight that the PLMVd represses genes implicated in the photosynthesis and more specifically genes involved in the protection of the two photosystems. This particular gene expression in the infected leaves was linked to the chlorosis and mosaic induced by the PLMVd. However, we cannot conclude with certitude if these symptoms are a cause or a consequence of this particular genes expression. The cDNA-AFLP has also allowed to identify the repression of genes coding for heat shock proteins (HSPs) in symptomatic leaves. These proteins generally have a role in the protein folding, assembly, translocation, stabilization and degradation. The regulation of their expression may have a great influence in the infected plants and, maybe, play a role in the symptoms expression. The gene coding for the novel cap-binding protein (nCBP) was also identified has repressed in the symptomatic leaves. The biological role of these proteins is unclear but it seems that these proteins act in the regulation of the mRNA translation. The repression of nCBP may thus have an important impact and to destabilize various biological pathways. Finally, two genes implicated in the plant defence were identified. One coding for a polygalacturonase inhibitor (over-expressed in symptomatic leaves) and the other one coding for a thiamine intermediate (involved in the SAR and over-expressed in the non-symptomatic leaves). The role of these proteins in the plant defence against the PLMVd is however unclear. To our knowledge, this is the first work where the host-pathogen relationship established during a PLMVd infection are studied. This is also the first time were the gene expression is linked to the viroid-induced symptoms. [less ▲]

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See detailApproaches for assessing the presence and impact of thyroid hormone disrupting chemicals in sea bass (Dicentrarchus labrax) from European coasts
Schnitzler, Joseph ULg

Doctoral thesis (2011)

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro ... [more ▼]

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro-Diphenyl-Trichloroethane (DDTs), Hexachlorocyclohexanes (HCHs), aldrin, dieldrin and trace elements (Cd, Cu, Se, Pb, Zn and Hg) were analysed in the muscle of sea bass (Dicentrarchus labrax) sampled in coastal regions near several important European river mouths (Gironde, Charente, Loire, Seine and Scheldt). We applied a multi-level approach of thyroid function assessment. Thyroxine (T4) and triiodothyronine (T3) concentrations in muscle were analyzed by radioimmunoassay. The activity of hepatic enzymes involved in extrathyroidal pathways of thyroid hormone metabolism, viz. deiodination, glucuronidation and sulfation were analyzed. Last, follicle diameter and epithelial cell heights were measured. We observed changes that lead to an increased conversion of T4 to T3 and lowered thyroid hormone excretion. The changes in the metabolic pathways of thyroid hormones can be interpreted as a pathway to maintain thyroid hormone homeostasis. The higher chlorinated PCBs seemed to be the most implicated in this perturbation. To gain a more integrated insight, we examined the effect of subchronic exposure to a mixture of Aroclor standards on thyroid hormone physiology and metabolism in juvenile sea bass. After 120 days of exposure, histomorphometry of thyroid tissue, muscular thyroid hormone concentration and activity of enzymes involved in metabolism of thyroid hormones were assessed. The results show that the effects of PCB exposures on the thyroid system are dose-dependent. Exposure to environmentally relevant doses of PCB (0.3 to 1.0 μg Σ7PCBs per g food pellets) increases thyroid hormone synthesis and stimulates hepatic T4 outer ring deiodinase and T4 sulfation. Thyroid hormone tissue levels were preserved thanks to the PCB induced changes in T4 dynamics. At 10 times higher concentrations (10 μg Σ7PCBs per g food pellets) an important depression of T3 and T4 levels could be observed which are apparently caused by degenerative histological changes in the thyroid tissue. We propose accurate interpretations, by reviewing the different stages of teleost thyroid function and regulation. [less ▲]

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See detailUn médiateur invisible. Analyse et mise en perspective du régime de régulation des ondes électromagnétiques
Joris, Geoffrey ULg

Doctoral thesis (2011)

La présente thèse de doctorat propose une analyse du régime de régulation des risques liés à la téléphonie mobile et ce à différents niveaux de pouvoir (International, européen, belge - échelons fédéral ... [more ▼]

La présente thèse de doctorat propose une analyse du régime de régulation des risques liés à la téléphonie mobile et ce à différents niveaux de pouvoir (International, européen, belge - échelons fédéral, régional et local). L'idée est de démontrer la dynamique d'ouverture et de fermeture tout au long de la "séquence" de la politique publique construisant progressivement un régime de régulation du risque "électromagnétique" [less ▲]

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See detailOptimisation et caractérisation d’un extrait de cassis riche en antioxydants utilisable comme complément alimentaire
Tabart, Jessica ULg

Doctoral thesis (2011)

Blackcurrant (Ribes nigrum, family Saxifragaceae) produces fruits with a high antioxidant content. This shrub is much known for its strongly aromatic fruits. It is largely used in the industrial ... [more ▼]

Blackcurrant (Ribes nigrum, family Saxifragaceae) produces fruits with a high antioxidant content. This shrub is much known for its strongly aromatic fruits. It is largely used in the industrial production of syrups and of concentrates, it contains very high quantities of phenolic compounds, particularly anthocyanins. Blackcurrant buds and leaves are also used as a food complement for their tonic and diuretic properties, as well as for the treatment of rheumatic affections. With this plant, we tried to develop, on a laboratory scale, a flavonoid-rich extract, stable in time and to show several biological activities. Initially, different plant materials were compared (fruits, leaves, buds, from different cultivars harvested at different times) and the method of extraction were optimized. Lyophilised-leaf extracts obtained with the acetone-water-acetic acid mixture (70: 28: 2) show an excellent yield in antioxidant compounds. These freeze-dried extracts have also the advantage of being stable for several months. We characterized these extracts for their content in various classes of antioxidant molecules. The leaves and the buds yielded extracts containing mainly flavonols, flavanols and total phenolic compounds, as compared to berries. On the other hand, these fruits showed higher contents of ascorbic acid and anthocyanins. In a third part, we analyzed certain health-properties (antioxidant capacity, anti-inflammatory capacity and the properties in vasorelaxation process) of the blackcurrant extracts by using in vitro methods as well as cellular and isolated organ models. Our study highlighted the intracellular and the extracellular properties of the blackcurrant extract as radical scavenger. We also showed an inhibition of the myeloperoxydase activity in the activated neutrophils, and an activation of the vasorelaxation process of the blood-vessels (production of NO, modulation of the expression of ARNm eNOS in the endothelial cells and relaxing effect in isolated organ), and this, without presenting any toxic effects. In conclusion, the black currant leaf extract obtained through extraction in acetone-water- acetic acid mixture has many interesting properties for health-protection. This extract, rich in phenolic compounds and having a high antioxidant activity, can also modulate the activity of several enzymes involved in inflammation or in vascular motricity. [less ▲]

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See detailContributions to Batch Mode Reinforcement Learning
Fonteneau, Raphaël ULg

Doctoral thesis (2011)

This dissertation presents various research contributions published during these four years of PhD in the field of batch mode reinforcement learning, which studies optimal control problems for which the ... [more ▼]

This dissertation presents various research contributions published during these four years of PhD in the field of batch mode reinforcement learning, which studies optimal control problems for which the only information available on the system dynamics and the reward function is gathered in a set of trajectories. We first focus on deterministic problems in continuous spaces. In such a context, and under some assumptions related to the smoothness of the environment, we propose a new approach for inferring bounds on the performance of control policies. We also derive from these bounds a new inference algorithm for generalizing the information contained in the batch collection of trajectories in a cautious manner. This inference algorithm as itself lead us to propose a min max generalization framework. When working on batch mode reinforcement learning problems, one has also often to consider the problem of generating informative trajectories. This dissertation proposes two different approaches for addressing this problem. The first approach uses the bounds mentioned above to generate data tightening these bounds. The second approach proposes to generate data that are predicted to generate a change in the inferred optimal control policy. While the above mentioned contributions consider a deterministic framework, we also report on two research contributions which consider a stochastic setting. The first one addresses the problem of evaluating the expected return of control policies in the presence of disturbances. The second one proposes a technique for selecting relevant variables in a batch mode reinforcement learning context, in order to compute simplified control policies that are based on smaller sets of state variables. [less ▲]

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See detailRhizosphere-driven lipopeptide production by different strains of Bacillus spp. as mechanism involved in biological control of plant pathogens
Nihorimbere, Venant ULg

Doctoral thesis (2011)

Some plant-beneficial bacteria with biopesticide potential produce antimicrobial compounds that are tightly involved in multitrophic interactions occurring in the phytosphere among which antagonism toward ... [more ▼]

Some plant-beneficial bacteria with biopesticide potential produce antimicrobial compounds that are tightly involved in multitrophic interactions occurring in the phytosphere among which antagonism toward a diverse range of phytopathogens. However, there is a crucial need for an accurate assessment of antibiotic production rate in this environment colonized by these bacteria. In this context, we conducted the present thesis work with the scope to better understand how two different Bacillus genus strains produce lipopeptides in the rhizosphere of plants. In the first part, one of the strains (B. amyloliquefaciens S499) was selected out of other isolates for its technological traits and in vitro inhibition growth activity of plant pathogenic fungi. We further demonstrated its biocontrol potential in tomato open-field experiments where plantings have been devastated by a local fungus preliminary identified as Fusarium semitectum. In a second part, we combined two mass spectrometry-based approaches (electrospray ionization and imaging) to analyze the pattern of surfactin, iturin and fengycin lipopeptide families produced in planta by strain S499. Our results show that rhizosphere conditions are conducive for surfactin synthesis but not for other types of lipopeptides and that the lipopeptide pattern can be markedly influenced by nutritional factors, biofilm formation and oxygen availability. In a last part, surfactin gene expression (srfA) level was evaluated in situ on tomato root using the reporter gene (LacZ) inserted in B. subtilis strain BGS3. Results showed effective expression of srfA and production of surfactin in biologically important level quantities upon establishment of bacterial population on roots. Our results also demonstrate that BGS3 developing in colonies, efficiently utilizes the main substrates from plant exudates to produce surfactins. The production may also be favored in bacteria growing slowly in the rhizosphere. Globally, this work contributes to better appreciate the impact of some environmental factors on the in situ biosynthesis of lipopeptides by strains of Bacillus which is probably an essential step for improving the level and reliability of their efficacy as biological agents for the control of plant diseases. [less ▲]

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See detailConscience de soi dans le vieillissement normal et pathologique
Feyers, Dorothée ULg

Doctoral thesis (2011)

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See detailContribution to pomegranate seeds conservation (Punica granatum L.) by osmotic dehydration
Bchir, Brahim ULg

Doctoral thesis (2011)

The aim of this work was to create a complete conservation process of pomegranate seeds (Punica granatum L.). This process is essentially based on osmotic dehydration (OD), which was associated to ... [more ▼]

The aim of this work was to create a complete conservation process of pomegranate seeds (Punica granatum L.). This process is essentially based on osmotic dehydration (OD), which was associated to freezing and air-drying process. Several parameters were studied to optimize the process such as osmotic solution (sucrose, glucose, and sucrose/glucose and date juice with sucrose added), temperature (30, 40, and 50°C) and state of the fruit (fresh and frozen). All these conditions were linked to seed proprieties (texture, structure, and colour). The study of osmotic dehydration parameters (water loss (WL), solids gain (SG) and weight reduction (WR)) showed that most significant changes of mass transfer took place during the first 20 min of dewatering using frozen seeds, independently of temperature and sugar type. During this period, seeds water loss was estimated at 46% in sucrose, 41% in sucrose/glucose mix, 39% in date juice, and 37% in glucose. Mass transfer was slower starting from fresh fruit but led to a higher rate of WL at the end of the process. This fact can be explained by scanning electron microscopy, which showed damage of seed cell structure after freezing. This has practical consequences in terms of the modification of seeds texture. The same process also revealed a modification of seed texture and cell structure after osmotic dehydration. Using a sucrose solution and a temperature of 50°C favoured the best mass transfer. The determination of different water fractions of seed by differential scanning calorimetry (DSC) showed that the % of frozen water decreased 3.5 times contrary the % of unfreezable water that increased 2.5 times. This favours a better seeds conservation. During osmotic dehydration, there was a non negligible leaching of natural solutes from seeds into the solution, which might have an important impact on the sensorial and nutritional value of seeds. Using only osmotic dehydration could not maintain the stability of seeds during conservation. In fact, after the osmotic process, water activity of seeds was found to be higher than 0.9, allowing to the development of microorganisms and some undesirable reactions. As a consequence, a drying of the pomegranate seeds (during four hours) was investigated at three different temperatures (40, 50, and 60 °C) with air flow rate of 2 ms-1. Prior to the drying process, seeds were osmodehydrated in a sucrose solution (55°Brix) during 20 min at 50°C. The drying kinetics and the effects of OD and air-drying temperature on antioxidant capacity, total phenolic, colour, and texture were determined. This work is a contribution to the study of physico-chemical properties of pomegranate seeds (Punica granatum L.) during freezing, osmotic dehydration and drying. After the global process, the pomegranate seed characteristics lead to new industrial developments. [less ▲]

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See detailInfluence of Biomaterials in Alveolar Bone Regeneration and Preservation
LAMBERT, France ULg

Doctoral thesis (2011)

Dental implants are nowadays a reliable solution to replace missing teeth and have been widely documented. However, they require a minimal bone quantity (in height and thickness). But alveolar bone ... [more ▼]

Dental implants are nowadays a reliable solution to replace missing teeth and have been widely documented. However, they require a minimal bone quantity (in height and thickness). But alveolar bone defects are very frequent, for instance due to periodontitis, traumatism or acute dental infection. Moreover, a simple tooth extraction leads to significant bone resorption. Therefore, alveolar bone regeneration is often necessary in order to place implants and to restore the patient's dentition with implant-supported prosthesis. Even though alveolar bone reconstructions have been considered as traumatic, especially due to the need of a second surgical site for bone harvesting, techniques have evolved with the introduction of biomaterials. However, it is difficult to compare the influences of such biomaterials on osteogenesis and to elaborate on the advantages of one product over another. The overall objective of this thesis is to contribute to the understanding of the biological concept of alveolar bone regeneration, in particular sinus lift and socket preservation procedures. The influence of biomaterials on bone regeneration has been emphasized through preclinical and clinical studies. The number of commercially available biomaterials for bone regeneration is growing every day and some materials are not supported by strong scientific data in the literature. The first part of this thesis (Chapter 1) is dedicated to the characterization of several biomaterials often used in dentistry. The impact of their various characteristics on osteogenesis has been reviewed, from chemical aspect to micro- and macromorphology. Furthermore, a data sheet integrating the physico-chemical and morphological properties of each studied biomaterial has been developed as a tool for clinicians. Sinus floor elevation has often been considered as a bone graft. In 1996, a consensus conference on “sinus lift” took place and the procedure was qualified as “sinus bone-graft”. But new scientific evidence has shown that this qualification is not justified. Chapter 2 aims at understanding the physiology and the biological model of sub-sinusal bone augmentation by using either a simple blood clot, autogenous bone chips or biomaterials (BHA) as space fillers under the lifted sinusal membrane. If bone formation did occur with the 3 types of space fillers, the augmented volumes significantly dropped with the blood clot or the autogenous bone chips but remained stable with BHA. Therefore, a slowly resorbable biomaterial such as BHA might be suitable in sub-sinusal bone augmentation to prevent the re-expansion process. Understanding the biological concept of sinus lift procedures, several authors demonstrated the clinical efficacy of biomaterials when used alone in this specific model. Nevertheless, biomaterials known to be resorbable led to a lamellar bone architecture that might not be able to maintain the volume of the regenerated tissue over time. Moreover, many types of biomaterials are available and scientific evidence of short and long-term performance of newly introduced biomaterials is still poor. Chapter 3 aims at comparing the performances, in terms of bone formation, resorption rate and 3-D stability, of four calcium phosphate-based biomaterials often used for sub-sinusal bone augmentation, in a rabbit model. Particulated space-filling biomaterials seemed to be more efficient to promote osteogenesis compared to paste-like biomaterials. Highly resorbable biomaterials appeared to withstand intrasinusal pressure after a period of six months in rabbits. Non- or slowly resorbable biomaterials are of great interest in the dental field because the long-term stability of 3-D bone augmentation is a key factor for dental implant and aesthetic outcomes. Therefore, the mechanical and non-resorbable properties of titanium, known to be highly compatible in vivo and highly resistant to body fluid corrosion, are potential advantages for bone augmentation prior to dental implantation. Nevertheless, the use of titanium particles as space fillers in bone regeneration was weakly reported in the literature from a histological point of view. Thus, Chapter 4 compares the behavior and the effect of porous titanium particles versus the well-documented BHA. Even though both biomaterials allowed osteogenesis and adequate 3-D stability, the bone architecture, and more specifically the amount of bone-to-material contact (BMC), was significantly different. Inclusion of the particles in a carrier or in binding agents such as a collagen gel or fibers might be of interest in order to ease surgical handling. However, the possible influence of those collagen carriers on bone tissue responses remains poorly investigated. The objective of Chapter 5 was to investigate the effect of collagen at different stages of the osteogenesis process, still in the same rabbit model. The findings clearly showed the presence of inflammatory cells at an early stage of bone regeneration when collagenated xenogenic biomaterials were used compared to collagen-free xenogenic granules. Nevertheless, despite the transient inflammation, the final quantity of newly formed bone was similar in the various groups. The last two chapters of this thesis take some of the preclinical findings of the previous chapters to the clinical field. The objective of Chapter 6 was to assess the clinical outcome of a minimalized sub-sinusal bone augmentation procedure using only biomaterials, simultaneously with the placement of 102 non-submerged implants in 40 patients. Implant and prosthodontic survival rates as well as complications were evaluated after a follow-up period of 2 to 6 years. This clinical trial emphasized that, if the amount of remaining bone height is sufficient to ensure implant primary stability, their placement can be performed simultaneously with sinus lifting, even in a non-submerged fashion. This procedure reduces the number of surgeries and the time before prosthetic rehabilitation. The objective of Chapter 7 was to to develop a new method to objectively evaluate in humans the 3-D volume variation of alveolar socket preservation over time by means of computed tomography and 3-D image analysis. Short summary: Before placing dental implants, alveolar bone regeneration is often required due to bone defects caused by periodontitis, traumatism or even a simple tooth extraction. Bone augmentation surgical procedures have very much evolved thanks to a better understanding of biological processes and to the introduction of biomaterials. The overall objective of this thesis is to bring a contribution to the understanding of the biological concept of alveolar bone regeneration, and in particular sinus lift and socket preservation procedures. The influence of biomaterials on bone regeneration has been emphasized through preclinical and clinical studies. [less ▲]

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See detailDesign and Implementation of a Distributed Lattice Boltzmann-based Fluid Flow Simulation Tool
Dethier, Gérard ULg

Doctoral thesis (2011)

Lattice Boltzmann-based (LB) simulations are well suited to the simulation of fluid flows in complex structures encountered in chemical engineering like porous media or structured packing used in ... [more ▼]

Lattice Boltzmann-based (LB) simulations are well suited to the simulation of fluid flows in complex structures encountered in chemical engineering like porous media or structured packing used in distillation and reactive distillation columns. These simulations require large amounts of memory (around 10 gigabytes) and would require very long execution times (around 2 years) if executed on a single powerful desktop computer. The execution of LB simulations in a distributed way (for example, using cluster computing) can decrease the execution time and reduces the memory requirements for each computer. Dynamic Heterogeneous Clusters (DHC) is a class of clusters involving computers inter-connected by a local area network; these computers are potentially unreliable and do not share the same architecture, operating system, computational power, etc. However, DHCs are easy to setup and extend, and are made of affordable computers. The design and development of a software system which organizes large scale DHCs in an efficient, scalable and robust way for implementing very large scale LB simulations is challenging. In order to avoid that some computers are overloaded and slow down the overall execution, the heterogeneity of computational power should be taken into account. In addition, the failure of one or several computers during the execution of a simulation should not prevent its completion. In the context of this thesis, a simulation tool called LaBoGrid was designed. It uses existing static load balancing tools and implements an original dynamic load balancing method in order to distribute the simulation in a way that minimizes its execution time. In addition, a distributed and scalable fault-tolerance mechanism based on the regular saving of simulation’s state is proposed. Finally, LaBoGrid is based on a distributed master-slave model that is robust and potentially scalable. [less ▲]

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