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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 detailEtude tribologique des matériaux de cage de roulement à billes en ambiance cryogénique
Servais, Christophe ULg

Master's dissertation (2011)

Le lien étroit entre le matériau constituant entièrement ou partiellement la cage d’un roulement à billes fonctionnant en ambiance cryogénique et la lubrification solide, employée dans ce domaine ... [more ▼]

Le lien étroit entre le matériau constituant entièrement ou partiellement la cage d’un roulement à billes fonctionnant en ambiance cryogénique et la lubrification solide, employée dans ce domaine particulier, a été mis en avant. Une comparaison des forces présentes aux contacts des billes et des bagues du roulement a pu être effectuée dans deux cas bien précis : en présence et en l’absence d’un lubrifiant. Ainsi, ces calculs ont montré une nette différence entre les deux configurations précitées, à l’avantage des pistes lubrifiées. Plus encore, la corrélation entre une défaillance au niveau de la lubrification et l’apparition d’un mouvement erratique du séparateur a été observée et quantifiée. De fait, une modélisation bidimensionnelle de la cage a été développée dans ce travail et le comportement de cette dernière a en effet révélé que plusieurs paramètres tribologiques interviennent de près ou de loin dans l’entrée en phase instable de ladite cage. [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. 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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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See detailMolecular characterization of embryogenesis in Phaseolus
Abid, Ghassen ULg

Doctoral thesis (2011)

Chez les végétaux supérieurs, l’embryogenèse est une phase clé du développement au cours de laquelle l’embryon établit les principales structures de la future plante. La compréhension des processus ... [more ▼]

Chez les végétaux supérieurs, l’embryogenèse est une phase clé du développement au cours de laquelle l’embryon établit les principales structures de la future plante. La compréhension des processus moléculaires et physiologiques menant à la formation de la graine est donc d’un intérêt agronomique majeur. Chez Phaseolus la caractérisation moléculaire de l’embryogenèse permet de mieux comprendre les mécanismes du développement embryonnaire et de son dysfonctionnement observé chez les hybrides interspécifiques. Cette thèse s’inscrit dans ce cadre et vise à identifier et caractériser des gènes clés impliqués dans le développement de l'embryon chez Phaseolus. Des hybridations interspécifiques ont été réalisées entre l’espèce P.vulgaris L. (cultivar NI637) utilisée comme parent mâle et l’espèce P. coccineus L. (cultivar NI16) utilisée comme parent femelle. Des analyses ont aussi été effectuées sur un mutant obtenu par mutagenèse chimique à l'EMS (Ethyl Méthyl Sulfonate) de graines de la variété BAT93 de P.vulgaris. Une étude histologique comparative a permis de suivre la dynamique de l’embryogenèse du haricot commun à partir d’embryons prélevés 3 à 12 jours après la pollinisation et provenant de plantes normales et déficients dans la production de graines. Les embryons de P. vulgaris se développent plus rapidement par rapport à ceux issus du mutant EMS. Ces derniers présentent des anomalies au niveau de l’embryon et du suspenseur. La caractérisation fonctionnelle de deux gènes candidats MIPS (myo-inositol phosphate synthase) et Sus (sucrose synthase) a été réalisée par RT-PCR quantitative et hybridation in situ suite à une étude spatio-temporelle d’expression de ces deux gènes candidats au cours de développement embryonnaire chez Phaseolus. L’analyse du profil d’expression de ces deux gènes montre qu’ils sont exprimés différemment au niveau des tissus de l’embryon et du suspenseur. L’analyse in silico nous a permis de sélectionner 22 gènes candidats dont nous avons vérifié l'expression au cours de développement de la graine chez Phaseolus. Des variations au niveau de la méthylation de l’ADN ont été déterminées chez les hybrides interspécifiques comparativement à leurs parents. La technique de l’HSS a permis d’isoler des fragments d’ADNs complémentaires différemment exprimés au cours de développement de la graine chez Phaseolus. L’analyse des séquences de ces ADNs complémentaires montre qu’ils codent pour plusieurs protéines intervenant dans le développement cellulaire et embryonnaire, en particulier le "storage protein activator" (SPA), le "pentatricopeptide repeat-containing protein" (PPR) et l’acetyl-CoA carboxylase (ACCase). La caractérisation de ces différents gènes exprimés au cours du développement de la graine, fournit de nouveaux outils susceptibles de mettre en évidence des mécanismes de dysfonctionnement embryonnaire chez le genre Phaseolus. [less ▲]

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See detailDevelopment and optimisation of methods to synthesise sol-gel nanoparticles and sol-gel core-shell nanoparticles to produce nanosensors
De Bleye, Charlotte ULg

Master's dissertation (2011)

The aim of this project was to synthesise nanosensors. It can be defined as an inert, biofriendly matrix in which sensing molecules are entrapped, allowing determination of analytes concentration. Two ... [more ▼]

The aim of this project was to synthesise nanosensors. It can be defined as an inert, biofriendly matrix in which sensing molecules are entrapped, allowing determination of analytes concentration. Two types of nanosensors were synthesised according to the Stöber method and characterised by a scanning electron microscope and a CPS disc centrifuge. The nanosensors were calibrated with succes using a fluorimeter. [less ▲]

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See detailImplémentation d'une méthode de région de confiance pour le diagnostic industriel
Gerard, Damien ULg

Master's dissertation (2011)

Detailed reference viewed: 51 (16 ULg)
See detailOptimal experimental designs for funtional magnetic resonance imaging
Maus, Bärbel ULg

Doctoral thesis (2011)

Detailed reference viewed: 12 (1 ULg)
See detailInteractions entre les gorilles des plaines de l'Ouest et l'exploitation forestière : Implications sylvicoles pour une forêt du Centre du Gabon
Haurez, Barbara ULg

Master's dissertation (2011)

The aim of this master thesis is to study the interactions between western lowland gorillas (Gorilla gorilla gorilla Savage & Wyman) and timber exploitation in a forest of Central Gabon. The research work ... [more ▼]

The aim of this master thesis is to study the interactions between western lowland gorillas (Gorilla gorilla gorilla Savage & Wyman) and timber exploitation in a forest of Central Gabon. The research work has been organized around tree main axis: (i) The determination of the impact of timber exploitation on gorilla density. Gorillas’ densities have been estimated in unlogged forest and in logged forest by pedestrian inventories of nesting sites. They are respectively equal to 3.7 and 1.7 weaned gorillas per km². Nevertheless these values are based upon small size samplings and it is not possible to assess if the difference between them is significant. (ii) The characterization of nesting habitat. We brought to light gorillas’ preference for relatively open sites for nesting. Particularly swamps and open terra firme forest are appreciated by gorillas for the construction of the nests. The vegetation type in which the nesting site is located has an influence on the structure and the composition of the nest. Plants of the Marantaceae and Zingiberaceae families are the most frequently used for nest construction. Moreover, we noticed the use of the old road logging network for nesting and feeding. (iii)The determination of the effect of endozoochory on seeds germination. The effect of endozoochory depends upon the botanical species of the seed. Too few results have been obtained in order to allow a reliable comparison of germination rates between ingested seeds and seeds extracted from fruits. However, the germination rate of the species Santiria trimera (Oliv.) Aubrév. (Burseraceae) seems to be enhanced by endozoochory, in particular by the removal of the pulp surrounding the seeds. This study demonstrates that western lowland gorilla is a species that adapts relatively well to timber exploitation. Besides thanks to its highly frugivorous diet and its nesting behavior, the gorilla is an effective seeds disperser. The role of the gorilla in forest regeneration seems to be inconsiderable. Complementary studies, particularly a long term study, would be necessary in order to examine thoroughly into the conclusions brought by this work. [less ▲]

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See detailNietzsche et le langage : une herméneutique vitaliste par-delà les mots
Remacle, François ULg

Master's dissertation (2011)

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See detailApplication de la méthode des éléments finis au pricing d'options
Janas, Sébastien ULg

Master's dissertation (2011)

Detailed reference viewed: 59 (13 ULg)
See detailLa famine Ruzagayura (Rwanda, 1943-1944): causes, conséquences et réactions des autorités
Singiza, Dantès ULg

Master's dissertation (2011)

Notre mémoire de Master en histoire à finalité approfondie, consacré à l’étude de la famine Ruzagayura (Rwanda, 1943-1944), a été soutenu à l’Université de Liège en septembre 2011. Dirigé par Catherine ... [more ▼]

Notre mémoire de Master en histoire à finalité approfondie, consacré à l’étude de la famine Ruzagayura (Rwanda, 1943-1944), a été soutenu à l’Université de Liège en septembre 2011. Dirigé par Catherine Lanneau, chargée de cours, il a également bénéficié des conseils et orientations de deux lecteurs, les Professeurs Francis Balace et Philippe Raxhon. Nous avons tenté d’y répondre aux principales questions que pose cette famine : quelles en furent les causes, le domaine d’extension, la durée et les conséquences à court et moyen terme ? Quelles furent les réactions des différentes autorités, locales et mandataires, mais également des missionnaires face à cette situation d’urgence ? Parmi les principales sources exploitées, mentionnons la correspondance et les rapports annuels conservés aux Archives africaines du Ministère des Affaires étrangères belge, la correspondance de l’ancien ministre des Colonies Albert de Vleeschauwer, conservée au KADOC mais aussi la correspondance et les diaires des missionnaires Pères Blancs et Sœurs Blanches, consultés à Rome. Enfin, des témoins ont pu être interrogés et ont contribué à enrichir ce mémoire de leurs souvenirs. La famine Ruzagayura est imputable à divers facteurs : la sécheresse, les travaux de l’effort de guerre et les agents destructeurs, comme le mildiou et la rhizoctonie. Elle est aggravée par les réquisitions de vivres et du bétail. La famine commence vers le mois d’octobre 1943 et se répand sur presque toute l’étendue du pays. Les autorités apprennent son existence quelque temps après son éclatement. Certains fonctionnaires, tant belges que rwandais, dissimulent son existence. D’autres nient sa réalité, ce qui leur attire les reproches de la part du résident Jean Paradis. Quant à celui-ci, il ne relaie pas non plus les informations en sa possession au vice-gouverneur général Eugène Jungers. Plus que des reproches, ce comportement lui vaut d’être destitué et muté au Congo par le vice-gouverneur général. Celui-ci aurait en effet peu apprécié d’apprendre l’existence de la famine au Rwanda lors d’un voyage anodin dans ce pays. Il le reproche également au roi Mutara III Rudahigwa. Une fois la famine reconnue, l’administration coloniale organise le ravitaillement en vivres. Elle confie leur distribution aux missionnaires qui encadrent en même temps les centres d’accueil d’affamés. Les chefs et les sous-chefs fournissent les vaches laitières et les vaches de boucherie pour nourrir la population. Celle-ci reçoit également des houes, de nouvelles semences de vivres et des boutures de manioc et de patates douces. De ce fait, elle reprend, sous la supervision des chefs rwandais, les cultures de champs et de marais en janvier 1944. La pluie tombant régulièrement, les récoltes augmentent et la situation vivrière se redresse. Les centres d’accueil ferment vers la deuxième moitié de 1944. La population restée démunie est convoyée dans les localités de Gishari et de Mokoto du territoire de Masisi, au Congo belge. La famine Ruzagayura a entraîné in fine un nombre important de décès, évalué à plusieurs dizaines de milliers de personnes. Elle a également provoqué d’importants déplacements de population. Par ailleurs, elle a poussé certaines personnes à voler des vivres pour subsister et s’est donc soldée par un accroissement de la criminalité. Son intensité et son extension au pays, associées aux travaux de l’effort de guerre, aux réquisitions de vivres et aux autres travaux agricoles, ont contrarié la population rwandaise au point de la pousser à s’opposer à l’autorité de ses chefs, du roi Mutara, de l’administration mandataire et des missionnaires. Certains en seraient mêmes arrivés à rêver de l’émancipation du pays. [less ▲]

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See detailÉtude de la représentation du cannabis en Communauté Germanophone de Belgique : étude réalisée auprés de 398 élèves de la quatrième à la sixième année de l’enseignement secondaire et de la première à la troisième année de l’enseignement en alternance
Dejozé, Michaël ULg

Master's dissertation (2011)

Étude de la représentation du cannabis et l’utilisation qu’en font les étudiants de la troisième à la sixième année de l’enseignement secondaire et de la première à la troisième année de l’enseignement en ... [more ▼]

Étude de la représentation du cannabis et l’utilisation qu’en font les étudiants de la troisième à la sixième année de l’enseignement secondaire et de la première à la troisième année de l’enseignement en alternance de la Communauté Germanophone de Belgique. [less ▲]

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See detailLattice dynamics in thermoelectric Zintl phases
Möchel, Anne ULg

Doctoral thesis (2011)

A brief introduction to the thermoelectric effects, the studied materials, and the experimen- tal methods is given in the first chapter. The introduction is not intended to be exhaustive, but only to ... [more ▼]

A brief introduction to the thermoelectric effects, the studied materials, and the experimen- tal methods is given in the first chapter. The introduction is not intended to be exhaustive, but only to summarize important basic information for the reader. The introduction is followed by four chapters dedicated to detailed experimental studies of the lattice dynamics in selected thermoelectric Zintl phases. First, the lattice dynamics in the unfilled and filled skutterudites FeSb3 , CoSb3 , and YbFe4 Sb12 were studied by nuclear inelastic scattering, inelastic neutron scattering, and several macroscopic methods. These studies reveal that FeSb3 exhibits softer Sb bonds than CoSb3 , that the density of phonon states is shifted towards lower energies and the velocity of sound is lower in FeSb3 as compared to CoSb3 . It appears thus that the soft [Fe4 Sb12 ] framework dynamics might play an important role in the thermoelectric properties of filled skutterudites. The observed anomalous temperature dependence of the elastic constants and the rearrangement of the spectral weight of the Yb phonon states in YbFe4 Sb12 can be explained by a change of the Yb valence state with the temperature. Second, the lattice dynamics in the Sr8 Ga16 Ge30 clathrate was investigated by inelastic neutron scattering measurements on a single crystal. We found that several mechanisms contribute to the low thermal conductivity in this system and that the reduction of the heat capacity contribution to the thermal conductivity plays a significant role to the low thermal conductivity, besides the reduction in the phonon lifetime and the phonon group velocity that is related to the guest atom. Third, the lattice dynamics of the Zintl phase Yb14 MnSb11 was studied by inelastic neu- tron scattering and nuclear inelastic scattering measurements. All phonon modes of these complex crystal systems are in a narrow energy range below ∼25 meV and the Debye tem- perature, the velocity of sound and the mean force constants are small compared to those of other thermoelectric materials such as Zn4 Sb3 . By comparing the lattice dynamics in Yb14 MnSb11 and Zn4 Sb3 different mechanisms which lead to the low thermal conductivity in Zintl phases have been identified. Between 300 and 1200 K no softening of the velocity of sound in Yb14 MnSb11 was observed by temperature dependent inelastic neutron scattering measurements, which is in line with its large melting temperature. [less ▲]

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See detailDéveloppement d’un modèle hydrologique sol et zone vadose afin d’évaluer l’impact des pollutions diffuses et des mesures d’atténuation sur la qualité des eaux en Région wallonne
Sohier, Catherine ULg

Doctoral thesis (2011)

Implementation of new European directives in the environmental field and, specially, in the water field, generate a request from policy-makers for news tools able to evaluate impact of measures token in ... [more ▼]

Implementation of new European directives in the environmental field and, specially, in the water field, generate a request from policy-makers for news tools able to evaluate impact of measures token in order to reduce pressures on ecosystems. In this context, the objective of this PhD thesis is to develop a “soil and vadose” hydrological model in order to evaluate impact of diffuses pollutions and mitigation measures on water quality in the Walloon region. The “soil and vadose zone” model of the Walloon region (EPICgrid model) has been developed at catchment scale with an original modular concept on the basis of the field scale “water-soil-plant” EPIC model (Williams et al., 1984). After that the model was validated at field scale and at catchment scale, the EPICgrid model was used to simulate the hydrological behaviour of the Walloon region catchments and to produce environmental indicators for surface water and groundwater bodies of the Walloon region. The simulated fluxes are related to unsaturated or temporarily saturated soils. The simulations are focused, on the one hand, on hydrological balance terms (direct runoff, subsurface fluxes, groundwater recharge, soil moisture variability, actual evapotranspiration) and, on the other hand, on associated fluxes of nitrogen, phosphorus, organic matters and sediments, from agricultural origin. The EPICgrid model was then used to evaluate water quality impact of mitigation measures token in order to reduce agricultural diffuse pollution effect on the quality on surface water and groundwater bodies in the Walloon region. [less ▲]

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See detailDétection de zones humides dans le béton par GPR en présence d’un gradient d’humidité.
Louis, Arnaud ULg

Master's dissertation (2011)

The objective of this master thesis is to highlight the impact of the presence of a humidity gradient on the detection of a wet area in concrete by combining a numerical approach and experimental results ... [more ▼]

The objective of this master thesis is to highlight the impact of the presence of a humidity gradient on the detection of a wet area in concrete by combining a numerical approach and experimental results. In order to achieve this objective, several models have been conducted using a numerical simulation program of electromagnetic waves propagation. Influence of the size of the gradient, but also their position and shape, have been studied. Meanwhile, two experimental programs have been established in order to artificially generate a gradient of moisture into the concrete. This gradient was established by capillary rise in one case and by drying in the other case. Humidity sensors placed in the slabs allowed us to control the evolution of the transition zone located above the wet area. We tried then to correlate the evolution of the gradient with results from a Ground Penetrating Radar with 2.3 GHz antenna. We studied the influence of the gradient on the evolution with time of the electromagnetic field. This experimental program required many preliminary tests to define the dielectric properties of the slabs and the specific response of the sensors. Based on modeling, we concluded that the detection of the wet area remains possible as long as it is far enough from the direct wave and as its thickness is less than 2/5 of the signal wavelength. Regarding the experimental results, we were able to highlight the signal evolution with regard to the evolution of the moisture gradient. In the case of capillary rise, we were also able to confirm the trends predicted by modeling. [less ▲]

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See detailEtude de l'activité antifongique des bactéries lactiques isolées de produits alimentaires fermentés et caractérisation de leurs métabolites inhibiteurs
Ndagano, Dora ULg

Doctoral thesis (2011)

Summary: The aim of this present research was to study the antifungal properties of lactic acid bacteria (LAB) isolated from fermented Mill flour and fermented cassava in order to use them for ... [more ▼]

Summary: The aim of this present research was to study the antifungal properties of lactic acid bacteria (LAB) isolated from fermented Mill flour and fermented cassava in order to use them for biopreservation. Antifungal activity of these LAB were assessed in MRS solid medium against food spoilage moulds as Aspergillus niger MUCL 28699, Aspergillus niger CWBIF194, Aspergillus tubingensis MP1 and Penicillium crustosum MY1. Three strains, Lactobacillus plantarum VE56, Weissella cibaria FMF4B16 and Weissella paramesenteroides LC11 were selected among 116 for their strongest inhibitory activity and their broad inhibitory spectrum against food moulds. The 4-fold concentrated supernatant of L. plantarum VE56 and W. paramesenteroides LC11 had the strongest inhibitory activity to compare to W. cibaria FMF4B16. The antifungal activity of the cell-free supernatant was pH dependent and insensitive to proteolytic enzymes action suggesting that the inhibitory activity was due to other compounds than proteins. The identification of antifungal compounds by chromatographic studies highlighted the production of phenyllactic acid by the three strains. In addition, 2-hydroxy-3-methylpentanoic acid and 2-hydroxy-4-methylpentanoic acid were produced by L. plantarum VE56 and W. paramesenteroides LC11. However, the concentration assessed in the supernatant was lower than the minimal inhibitory concentration showing a synergic action of all these produced compounds. The effect of the antifungal supernatant of L. plantarum VE56 and W. paramesenteroides LC11 on Aspergillus flavus NRRL 3357 resulted to an inhibition of conidial development and aflatoxin B1 production which was reflected in decreased gene expression of brlA (conidiophore specific transcription factor) and laeA (global regulator of secondary metabolism). These two bacteria also delayed Penicillium expansum MUCL 14498 conidial development in bread. [less ▲]

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See detailSonia Hajjar Domaine : Human resource management Titre : Status of Female Auditors in Lebanon: Careers and Family Concerns
Hajjar, Sonia ULg

Doctoral thesis (2011)

This research discusses the status of female auditors in Lebanon with a special emphasis on individual career and family concerns. It attempts at investigating the status of female auditors, and at ... [more ▼]

This research discusses the status of female auditors in Lebanon with a special emphasis on individual career and family concerns. It attempts at investigating the status of female auditors, and at pointing out the major hindrances that they face when trying to achieve a balance between career and family life; thus, issues such as organizational, individual, and social factors are discussed. The focus is to discuss the status of female Lebanese auditors through analysis and conclusions drawn from practical experience and to present a model of the issues in relation to certain variables and factors. Questionnaires and interviews were used to collect the data. Results show that the above-mentioned factors, cross-referenced with the glass ceiling, work life balance, and turnover, are combined. Research revealed that many factors mold the status of female auditors in Lebanon. The limitations of the study stem from the fact that no such studies have been conducted in Lebanon and, thus, the literature review was mainly constructed on published research done in the West. Results reveal that the individual Lebanese female auditor is faced with a glass ceiling only because she chose her family over her career, and when she chose to leave the profession (turnover) it was because of her family duties, the long working hours, stress, and work life balance that forced her to make a choice between herself as a career women, or as a mother and wife. The study is aimed at establishing possible relationship between academia, audit profession, and the business market. [less ▲]

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See detailLe traitre et ses manières : La métaphysique de l'Idée dans la pensée de Gilles Deleuze
Barbion, Sébastien ULg

Master's dissertation (2011)

Ce texte dégage la systématicité de la métaphysique deleuzienne de l’Idée autour d’un concept discret, mais décisif de Différence et répétition : le concept de traîtrise – plutôt que le modèle et ses ... [more ▼]

Ce texte dégage la systématicité de la métaphysique deleuzienne de l’Idée autour d’un concept discret, mais décisif de Différence et répétition : le concept de traîtrise – plutôt que le modèle et ses copies, le traître et ses manières. Selon Deleuze, les représentations empiriques de l’Idée ne se comprennent pas depuis leur plus ou moins grande conformité ou adéquation à la nature de l’Idée elle-même. L’Idée n’existe que par ses représentations, selon des trahisons essentielles qui la constituent comme toujours déjà différente d’avec soi. Ce texte tente de montrer que l’empirisme transcendantal – ou la métaphysique de l’Idée – de Gilles Deleuze repose sur ce projet d’une théorisation des différentes manières dont l’Idée est trahie et se manifeste. [less ▲]

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See detailLes cultes de l'île de Cos après le synécisme de 366 avant notre ère. Contribution à l'étude du fonctionnement du polythéisme grec
Paul, Stéphanie ULg

Doctoral thesis (2011)

L’étude des cultes de l’île de Cos vise à discerner les modalités selon lesquelles une cité grecque organise ses relations avec le monde supra-humain. L’exposé est articulé en deux volets complémentaires ... [more ▼]

L’étude des cultes de l’île de Cos vise à discerner les modalités selon lesquelles une cité grecque organise ses relations avec le monde supra-humain. L’exposé est articulé en deux volets complémentaires. La première partie propose une analyse systématique des différents cultes attestés dans l’île, fondée sur l’exploitation de toutes les sources à disposition, épigraphiques principalement, mais également littéraires et archéologiques. Les cultes sont ordonnés selon une répartition géographique, ceux de la cité, puis des dèmes. Le sanctuaire de l’Asclépieion, situé à quelques kilomètres à l’extérieur de la ville de Cos et jouissant d’une cohérence propre, fait l’objet d’un chapitre à part. Cette analyse exhaustive, incluant les nouvelles inscriptions publiées en nombre ces dernières années et encore peu étudiées, permet de pallier une lacune dans la bibliographie actuelle. La seconde partie du travail se conçoit comme une synthèse de cette analyse des cultes et propose une réflexion sur le fonctionnement du polythéisme tel que la cité de Cos permet de le saisir. Le premier chapitre, consacré aux « configurations du panthéon », s’attache à définir, dans la mesure du possible, le profil des divinités qui constituent ce dernier, ainsi que les relations qui se nouent entre elles. L’intérêt d’une telle approche régionale est de pouvoir ancrer ces cultes dans le contexte historique auquel ils appartiennent, et cela se justifie d’autant plus que les panthéons locaux « cristallisaient » les préoccupations des communautés qui les construisaient. Ainsi, on observe qu’un événement particulier de l’histoire de l’île a eu une influence remarquable sur l’organisation des cultes. Il s’agit du synécisme de 366 avant notre ère, qui a vu l’unification des différentes communautés en une seule cité, dont le centre urbain a été fondé sur la pointe nord de l’île. Cette influence résulte notamment en une orientation spécifique conférée à une série de cultes, qui mettent une emphase particulière sur la communauté et sur l’unité de la cité, tels que ceux de Zeus Polieus ou d’Aphrodite Pandamos. En outre, et en dépit de l’ancrage local de cette étude, le recours fréquent à la comparaison avec les panthéons d’autres cités grecques permet d’inscrire largement l’interprétation de celui de Cos sur un plan panhellénique. À côté de cette réflexion sur le panthéon de Cos, un second chapitre se propose d’affiner l’interprétation de certaines procédures sacrificielles, décrites dans les inscriptions et évoquées dans la première partie, et de les mettre en perspective par rapport au reste de la documentation de Cos. Une telle étude contextuelle du sacrifice a l’avantage d’apporter un éclairage complémentaire aux études thématiques plus générales, qui ne permettent guère de remettre les pratiques en contexte. L’acte sacrificiel étant au cœur du système religieux des Grecs et de leur communication avec le monde supra-humain, son étude ne peut être dissociée de celle de la représentation du divin. Ainsi, la manière dont ces actes sacrificiels sont posés est porteuse de sens quant au profil du destinataire ou encore au message précis qui lui était adressé. En conclusion, par les diverses configurations qu’elle met en évidence, qu’elles relèvent de spécificités locales ou de représentations plus largement partagées, l’étude des cultes de Cos permet d’apporter une contribution à notre compréhension du système religieux des Grecs et de son imbrication dans la vie des communautés. [less ▲]

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See detailPhysical modelling of overbank flows with a groyne set on the floodplain
Peltier, Yann ULg

Doctoral thesis (2011)

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See detailModeling of the surface mass balance in Svalbard with the regional climate model MAR over 1958-2010
Lang, Charlotte ULg

Master's dissertation (2011)

It is well known that high latitude zones are very sensitive to climate change. As a result of global warming, ice sheet melting has increased which in turn has an influence on climate through ... [more ▼]

It is well known that high latitude zones are very sensitive to climate change. As a result of global warming, ice sheet melting has increased which in turn has an influence on climate through modifications of the thermohaline circulation, feedback of ice albedo, sea level rise,. . . Svalbard is an archipelago located between 74 and 81 ◦lat N and 60 percent of its area (62 248 km2 ) is covered with glaciers and ice sheets. The impact of global warming on the Svalbard cryosphere can be estimated with climate models. However, we need to use regional climate models as they offer the possibility of a higher resolution than general circulation models. We have carried out a simulation of the Svalbard climate over the last 50 years (from 1958 to 2010) with the regional climate MAR model (tuned for the Greenland ice sheet) at a 10 km resolution forced with the ECMWF reanalysis. As validation, the modeled climate has been compared to near surface measurements at several weather stations through the archipelago. The results show a large interannual variability of the surface mass balance over Svalbard along with an increasing melting. The increase in temperature is responsible for the melting rate and the interannual variability is due to the variations of the mean summer temperature. [less ▲]

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See detailModelling the hydrological response of an urban watershed Diachronic analysis of the effects of land use changes on storm runoff generation in the Upper Bukit Timah basin, Singapore
Cesar, Emilie ULg

Master's dissertation (2011)

This work consisted in the modelling of the rainfall-runoff relationships in the Upper Bukit Timah catchment in Singapore, in order to highlight the impacts of urbanisation on hydrology. The SWMM model, a ... [more ▼]

This work consisted in the modelling of the rainfall-runoff relationships in the Upper Bukit Timah catchment in Singapore, in order to highlight the impacts of urbanisation on hydrology. The SWMM model, a one-dimensional physically based model especially developed for urban areas, was mainly used. The parameters encoded into the model were determined by different means and several methods were used for their determination in order to assess their influence on the modelling.Using the final adjustment of the SWMM model, a diachronic analysis was performed in order to present the effects of urbanisation on runoff. [less ▲]

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See detailÊtre jeune et Franstalig à Gand. Enquête sociolinguistique exploratoire au sein de la communauté des francophones de Flandre.
Dassargues, Alix ULg

Master's dissertation (2011)

Ce travail explore le champ des attitudes et des représentations linguistiques de francophones de Flandre et plus particulièrement celles de jeunes (15-25ans) francophones gantois. L’analyse de données ... [more ▼]

Ce travail explore le champ des attitudes et des représentations linguistiques de francophones de Flandre et plus particulièrement celles de jeunes (15-25ans) francophones gantois. L’analyse de données quantitatives recueillies par un questionnaire écrit et de données qualitatives provenant d’interviews et d’observations participatives a permis de mettre au jour une série de comportements sociolinguistiques originaux. Ces nouveaux apports ont, en outre, été confrontés aux résultats d’une étude sociolinguistique effectuée par Yolande Van den Branden (UGent) sur une population semblable trente ans auparavant. La comparaison des données qualitatives des deux enquêtes met ainsi en évidence la lente et profonde évolution de la situation du français en Flandre entre 1983 et 2011. [less ▲]

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See detailModulation de l'effet scale-down chez Saccharomyces cerevisiae par ajout d'acide oléique
Zune, Quentin ULg

Master's dissertation (2011)

Scale-down technology allows to simulate heterogeneities created in an industrial reactor at a laboratory scale. In this kind of bioreactor, fed-batch production of Saccharomyces cerevisiae on glucose ... [more ▼]

Scale-down technology allows to simulate heterogeneities created in an industrial reactor at a laboratory scale. In this kind of bioreactor, fed-batch production of Saccharomyces cerevisiae on glucose induces the apparition of the scale-down effect. It means a decrease in biomass synthesis and an increase in ethanol production as time of culture in comparison with an ideal bioreactor where the mixing operation is perfect. In a recent study, FERIA-GERVASIO et al., (2008) notice that ethanol production is delayed on behalf biomass synthesis when a glucose pulse occurs in a chemostat glucose/oleic acid. The goal of this work is to study the modulation of the scale-down effect by the presence of oleic acid in a fed-batch production of Saccharomyces cerevisiae (boulardii). The methodology is separated in three parts: - development of a yeast conditioning protocol with oleic acid - yeast production with a mixed substrate composed of glucose and oleic acid in a scale-down reactor - computer simulation of glucose gradients experienced by yeast during their displacement in the bioreactor In addition to the measurements performed to describe growth kinetic of yeast on this mixed substrate, an original phenotypic analysis of yeast has been achieved throughout each culture thanks to flow cytometry. At the end of this work, vacuoles staining with fluoro-isothiocyanate has revealed the induction of peroxisomes infered during the yeast conditioning by flow cytometry. Then, it was demonstrated that in a culture in a scale-down reactor preceded by the conditioning, oleic acid naturally reduces ethanol production for the benefit of the biomass synthesis in comparison with a yeast cultivated on glucose only in scale-down reactors. Flow cytometry has not identified a negative influence of oleic acid on cell viability. Finally, simulation of glucose gradients experienced by yeast in the scale-down reactor with oleic acid has demonstrated that yeast feel important extracellular fluctuations in the recycle loop. [less ▲]

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See detailA 3D model of ocean biogeochemical cycles and climate sensitivity studies
Mouchet, Anne ULg

Doctoral thesis (2011)

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See detailPhenomenology of supersymmetric neutrino mass models
Vicente, Avelino ULg

Doctoral thesis (2011)

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See detailRecherches autour de la figure de Crésus de Lydie
Leloux, Kevin ULg

Master's dissertation (2011)

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See detailLes meubles cultuels des églises paroissiales ou cathédrales
Desseilles, François ULg

Master of advanced studies dissertation (2011)

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See detailStructured sparse principal component analysis for fMRImaging
Liegeois, Raphaël ULg

Master's dissertation (2011)

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See detailSupervised Learning for Sequential and Uncertain Decision Making Problems - Application to Short-Term Electric Power Generation Scheduling
Cornélusse, Bertrand ULg

Doctoral thesis (2010)

Our work is driven by a class of practical problems of sequential decision making in the context of electric power generation under uncertainties. These problems are usually treated as receding horizon ... [more ▼]

Our work is driven by a class of practical problems of sequential decision making in the context of electric power generation under uncertainties. These problems are usually treated as receding horizon deterministic optimization problems, and/or as scenario-based stochastic programs. Stochastic programming allows to compute a first stage decision that is hedged against the possible futures and -- if a possibility of recourse exists -- this decision can then be particularized to possible future scenarios thanks to the information gathered until the recourse opportunity. Although many decomposition techniques exist, stochastic programming is currently not tractable in the context of day-ahead electric power generation and furthermore does not provide an explicit recourse strategy. The latter observation also makes this approach cumbersome when one wants to evaluate its value on independent scenarios. We propose a supervised learning methodology to learn an explicit recourse strategy for a given generation schedule, from optimal adjustments of the system under simulated perturbed conditions. This methodology may thus be complementary to a stochastic programming based approach. With respect to a receding horizon optimization, it has the advantages of transferring the heavy computation offline, while providing the ability to quickly infer decisions during online exploitation of the generation system. Furthermore the learned strategy can be validated offline on an independent set of scenarios. On a realistic instance of the intra-day electricity generation rescheduling problem, we explain how to generate disturbance scenarios, how to compute adjusted schedules, how to formulate the supervised learning problem to obtain a recourse strategy, how to restore feasibility of the predicted adjustments and how to evaluate the recourse strategy on independent scenarios. We analyze different settings, namely either to predict the detailed adjustment of all the generation units, or to predict more qualitative variables that allow to speed up the adjustment computation procedure by facilitating the ``classical'' optimization problem. Our approach is intrinsically scalable to large-scale generation management problems, and may in principle handle all kinds of uncertainties and practical constraints. Our results show the feasibility of the approach and are also promising in terms of economic efficiency of the resulting strategies. The solutions of the optimization problem of generation (re)scheduling must satisfy many constraints. However, a classical learning algorithm that is (by nature) unaware of the constraints the data is subject to may indeed successfully capture the sensitivity of the solution to the model parameters. This has nevertheless raised our attention on one particular aspect of the relation between machine learning algorithms and optimization algorithms. When we apply a supervised learning algorithm to search in a hypothesis space based on data that satisfies a known set of constraints, can we guarantee that the hypothesis that we select will make predictions that satisfy the constraints? Can we at least benefit from our knowledge of the constraints to eliminate some hypotheses while learning and thus hope that the selected hypothesis has a better generalization error? In the second part of this thesis, where we try to answer these questions, we propose a generic extension of tree-based ensemble methods that allows incorporating incomplete data but also prior knowledge about the problem. The framework is based on a convex optimization problem allowing to regularize a tree-based ensemble model by adjusting either (or both) the labels attached to the leaves of an ensemble of regression trees or the outputs of the observations of the training sample. It allows to incorporate weak additional information in the form of partial information about output labels (like in censored data or semi-supervised learning) or -- more generally -- to cope with observations of varying degree of precision, or strong priors in the form of structural knowledge about the sought model. In addition to enhancing the precision by exploiting information that cannot be used by classical supervised learning algorithms, the proposed approach may be used to produce models which naturally comply with feasibility constraints that must be satisfied in many practical decision making problems, especially in contexts where the output space is of high-dimension and/or structured by invariances, symmetries and other kinds of constraints. [less ▲]

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See detailMachine Learning Solution Methods for Multistage Stochastic Programming
Defourny, Boris ULg

Doctoral thesis (2010)

This thesis investigates the following question: Can supervised learning techniques be successfully used for finding better solutions to multistage stochastic programs? A similar question had already been ... [more ▼]

This thesis investigates the following question: Can supervised learning techniques be successfully used for finding better solutions to multistage stochastic programs? A similar question had already been posed in the context of reinforcement learning, and had led to algorithmic and conceptual advances in the field of approximate value function methods over the years. This thesis identifies several ways to exploit the combination "multistage stochastic programming/supervised learning" for sequential decision making under uncertainty. Multistage stochastic programming is essentially the extension of stochastic programming to several recourse stages. After an introduction to multistage stochastic programming and a summary of existing approximation approaches based on scenario trees, this thesis mainly focusses on the use of supervised learning for building decision policies from scenario-tree approximations. Two ways of exploiting learned policies in the context of the practical issues posed by the multistage stochastic programming framework are explored: the fast evaluation of performance guarantees for a given approximation, and the selection of good scenario trees. The computational efficiency of the approach allows novel investigations relative to the construction of scenario trees, from which novel insights, solution approaches and algorithms are derived. For instance, we generate and select scenario trees with random branching structures for problems over large planning horizons. Our experiments on the empirical performances of learned policies, compared to golden-standard policies, suggest that the combination of stochastic programming and machine learning techniques could also constitute a method per se for sequential decision making under uncertainty, inasmuch as learned policies are simple to use, and come with performance guarantees that can actually be quite good. Finally, limitations of approaches that build an explicit model to represent an optimal solution mapping are studied in a simple parametric programming setting, and various insights regarding this issue are obtained. [less ▲]

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See detailModelling Transient Air-water Flows in Civil and Environmental Engineering
Kerger, François ULg

Doctoral thesis (2010)

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See detailSynthèse et caractérisation de nanomatériaux fonctionnels siliciques structurés à l’aide de micelles complexes de copolymères séquencés doublement hydrophiles
Warnant, Jérôme ULg

Doctoral thesis (2010)

This study focused on the design and development of new structuring agents of silica constituted of induced and reversible assemblies of original copolymers, the double hydrophilic block copolymers (DHBC ... [more ▼]

This study focused on the design and development of new structuring agents of silica constituted of induced and reversible assemblies of original copolymers, the double hydrophilic block copolymers (DHBC). The first system studied consists of a neutral-anionic DHBC PAPEO-b-PAA ou poly(acrylate methoxy poly (ethylene oxide))-b-poly (acrylic acid). The PAA block is a weak polyacid with a degree of ionization depending on the pH. In aqueous solution and in a right pH range, the association of this copolymer with a weak polybase, an oppositely charged polyamine, such as an oligochitosan, leads to the formation of polyion complex micelles (PIC) with a core/corona structure. These micelles can direct the structure of highly organized inorganic materials with different types of mesostructures. In a second step, by adjusting the conditions of pH, ionic strength, it is possible to "control" the extraction of organic species to get functional porous materials able to trap species of charge opposite to the functionality. Organized materials are obtained because of a favourable balance of the interactions between organic and inorganic species. If a polyamine/silica interaction occurs at the expense of the interaction polyamine/DHBC, the mesostructuring process by the micelles is limited. A neutral-cationic DHBC PEO-b-PDMAEMA poly(ethylene oxide)-b-poly(2-(dimethylamine)ethyl) associated with an anionic PVS poly(vinyl sulfonic acid) polymer can play a dual role in the synthesis of silica materials: firstly managing the growth of silica particles by interacting with the silicates and secondly acting as a structuring agent in association with PVS, confering a mesostructuration to the material. Finally, a very promising approach allowed to encapsulate water-soluble and charged drugs in a material by using as silica complexing agent a complex between the drug and a DHBC. [less ▲]

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See detailLES PRODUCTIONS LITHIQUES DU PALÉOLITHIQUE MOYEN DE BELGIQUE : VARIABILITÉ DES SYSTÈMES D’ACQUISITION ET DES TECHNOLOGIES EN RÉPONSE À UNE MOSAÏQUE D’ENVIRONNEMENTS CONTRASTÉS
Di Modica, Kévin ULg

Doctoral thesis (2010)

LITHIC PRODUCTION FROM THE MIDDLE PALAEOLITHIC OF BELGIUM VARIABILITY OF RAW MATERIAL PROCUREMENT SYSTEMS AND TECHNOLOGIES AS A RESPONSE TO A MOSAIC OF CONTRASTING ENVIRONMENTS Belgium is noted for its ... [more ▼]

LITHIC PRODUCTION FROM THE MIDDLE PALAEOLITHIC OF BELGIUM VARIABILITY OF RAW MATERIAL PROCUREMENT SYSTEMS AND TECHNOLOGIES AS A RESPONSE TO A MOSAIC OF CONTRASTING ENVIRONMENTS Belgium is noted for its many ancient prehistoric sites which are spread over a limited geographic area. Despite its limited size, this area shows important regional contrasts in terms of topographic relief and availability of mineral resources. These factors in conjunction with important regional differences related to the types of sites represented (cave/open air) as well as the proximity and morphology of the available flint make this area favorable for the study of man's relationship with his environment. The connection between the Neanderthal populations and the types of environments encountered constitutes the focus of this study which is divided into four closely associated parts. The first part is devoted to environmental variation starting with the interface between the flint-rich plains of Middle Belgium and the deep valleys of Upper Belgium. Only a few kilometers separate these two contrasting environments. Chronological variations follow because quaternary sedimentation had as much impact on the accessibility of lithic resources as on site preservation. The history of the research from 1829 to the present is also addressed. The motives and constraints of the researchers are responsible for both the abundance of documentary evidence and for the extremely variable quality of these documents. The second part concerns the previously mentioned documentation. Artifacts attributable to the Middle Paleolithic have been recovered from 437 sites : 46 sites (16 major ones) are found in karstic contexts and 391 sites (31 major ones) are open air sites. The distribution of these sites is a direct result of taphonomic processes, circumstances of discovery, and choices made by the Neanderthals themselves. In particular, two environments were favored : the plains which have abundant flint resources and the caves of the Mosan Basin. Prehistoric Man's choice of sites appears to be linked to topographical position : plateaus or cliff tops overhanging small valleys were preferred. Chronological distribution is also examined. It notably shows an abundant documentation from the Beginning of the Weichselian Pleniglacial and an absence of occupation during the Lower Weichselien Pleniglacial It also shows a concentration of archaeological evidences related to the Middle Weichselian Pleniglacial which is very exceptional for Northwest Europe. Based on research to date, Scladina Cave (38.000 B.P.) gives the most recent date for Middle Palaeolithic industries and Betche-aux-Rochtes at Spy (36.000 B.P.) provides the date for the last Neanderthals. The third part consists of a detailed study of ten lithic industries and their environmental context. Several general tendencies were detected in the way Palaeolithic populations adapted their systems of acquisition and exploitation of rocks. Clear variations in the systems of acquisition and exploitation along a northwest/southeast gradient were noted. In Lower Belgium, the use of local flint pebbles was coupled with the importation of nuclei and flakes from Middle Belgium. In Middle Belgium, the available local flint was used almost exclusively. Recourse to other local rocks or to imports was very exceptional. In Upper Belgium, the importation of flint from Middle Belgium in combination with other locally available materials constituted the rule. These variations in the systems of raw material procurement generated diversity in terms of nature, morphology, conditioning, and availability of the nodules chosen by the knappers. These diverse parameters impacted the technical choices of the Neanderthals during the reduction or debitage stage. Other important regional differences were also observed. The sites of Upper Belgium exhibited economic options which manifested in the reduction of blocks (Trou du Diable at Hastière) and in extreme adaptations or manipulation of concepts of reduction such as those recognized in several refittings from Scladina Cave. The sites of Middle Belgium exhibited an extravagant use of the primary material and a strict expression of different concepts : mainly Levallois, also Discoid, and volumetric blade production (gisement paléolithique d'otrange, Obourg Canal). The fourth part is devoted to a discussion of the results and a preliminary comparison to the rest of Europe. The connection of the diversity in lithic productions and the geographic position of the sites is particularly important. Lithic industries from the two occupation layers of Scladina (layers 5 and 1A) present more analogies between themselves than other plenicomtemporaneous sites in different environments (lays 1A of Scladina and WFL of Veldwezelt-Hezerwater). Other factors of variability superimpose themselves in this diverse region : function of the sites, cultural traditions and techniques, palaeoenvironmental variations, chronology. Comparisons with the results obtained from regions bordering Belgium as well as those obtained from greater distances showed some behavioural similarities in southern Europe in environments which evoke aspects of the karst valleys of the Mosan Basin. Translation : Cheryl Roy, Department of Anthropology, Faculty of Social Sciences, Vancouver Island University [less ▲]

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See detailOn the influence of indenter tip geometry on the identification of material parameters in indentation testing
Guo, Weichao ULg

Doctoral thesis (2010)

The rapid development of structural materials and their successful applications in various sectors of industry have led to increasing demands for assessing their mechanical properties in small volumes. If ... [more ▼]

The rapid development of structural materials and their successful applications in various sectors of industry have led to increasing demands for assessing their mechanical properties in small volumes. If the size dimensions are below micron, it is difficult to perform traditional tensile and compression tests at such small scales. Indentation testing as one of the advanced technologies to characterize the mechanical properties of material has already been widely employed since indentation technology has emerged as a cost-effective, convenient and non-destructive method to solve this problem at micro- and nanoscales. In spite of the advances in indentation testing, the theory and development on indentation testing are still not completely mature. Many factors affect the accuracy and reliability of identified material parameters. For instance, when the material properties are determined utilizing the inverse analysis relying on numerical modelling, the procedures often suffer from a strong material parameter correlation, which leads to a non-uniqueness of the solution or high errors in parameter identification. In order to overcome that problem, an approach is proposed to reduce the material parameter correlation by designing appropriate indenter tip shapes able to sense indentation piling-up or sinking-in occurring in non-linear materials. In the present thesis, the effect of indenter tip geometry on parameter correlation in material parameter identification is investigated. It may be helpful to design indenter tip shapes producing a minimal material parameter correlation, which may help to improve the reliability of material parameter identification procedures based on indentation testing combined with inverse methods. First, a method to assess the effect of indenter tip geometry on the identification of material parameters is proposed, which contains a gradient-based numerical optimization method with sensitivity analysis. The sensitivities of objective function computed by finite difference method and by direct differentiation method are compared. Subsequently, the direct differentiation method is selected to use because it is more reliable, accurate and versatile for computing the sensitivities of the objective function. Second, the residual imprint mappings produced by different indenters are investigated. In common indentation experiments, the imprint data are not available because the indenter tip itself shields that region from access by measurement devices during loading and unloading. However, they include information about sinking-in and piling-up, which may be valuable to reduce the correlation of material parameter. Therefore, the effect of the imprint data on identification of material parameters is investigated. Finally, some strategies for improvement of the identifiability of material parameter are proposed. Indenters with special tip shapes and different loading histories are investigated. The sensitivities of material parameters toward indenter tip geometries are evaluated on the materials with elasto-plastic and elasto-visoplastic constitutive laws. The results of this thesis have shown that first, the correlations of material parameters are related to the geometries of indenter tip shapes. The abilities of different indenters for determining material parameters are significantly different. Second, residual imprint mapping data are proved to be important for identification of material parameters, because they contain the additional information about plastic material behaviour. Third, different loading histories are helpful to evaluate the material parameters of time-dependent materials. Particularly, a holding cycle is necessary to determine the material properties of time-dependent materials. These results may be useful to enable a more reliable material parameter identification. [less ▲]

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