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See detailCaractérisation de l'hydrodynamique des écoulements gaz-liquide à contre-courant dans une colonne rectangulaire à empilage
Calvo, Sébastien ULg

Doctoral thesis (2010)

La recherche réalisée dans le cadre de cette thèse consiste à développer des électrodes positives pour les accumulateurs (ou "batteries") au lithium sous formes de films minces de quelques centaines de ... [more ▼]

La recherche réalisée dans le cadre de cette thèse consiste à développer des électrodes positives pour les accumulateurs (ou "batteries") au lithium sous formes de films minces de quelques centaines de nanomètres d'épaisseur. Afin de stocker un maximum d'énergie dans le volume réduit d'un accumulateur au lithium miniature, une architecture mésoporeuse (dont le diamètre des pores est compris entre 2 et 50 nm), permettant d’augmenter la surface spécifique du matériau, a été réalisée au sein des films. Deux méthodes de soft templating ont été utilisées dans cette thèse. Ces méthodes consistent à ajouter à la solution de précurseurs inorganiques un copolymère amphiphile formateur de micelles, dont l'élimination ultérieure par traitement thermique permet d'obtenir des films contenant des pores dont la dimension varie selon le copolymère utilisé. Dans la perspective du développement d'une électrode pour accumulateur au lithium, deux stratégies sont possibles : (i) la préparation d'un film mésoporeux de l'oxyde non lithié, suivie d'une insertion du lithium par voie électrochimique, ou (ii) la préparation directe d'un film mésoporeux de l'oxyde lithié. Ces deux voies ont été comparées et l’influence du lithium sur la synthèse des films minces mésoporeux par soft templating a donc pu être étudiée. En termes de compositions ciblées, les oxydes de vanadium et de lithium (Li-V-O), tels que LiV3O8 ou LiV2O5, constituent des objectifs évidents en raison de leurs performances électrochimiques reconnues. Etant donné le caractère a priori délicat de la condensation des réseaux à base d'oxyde de vanadium, d'autres systèmes ont également été abordés dans le cadre de la thèse, à savoir Li-V-Nb-O, Li-Nb-O et Li-Ti-O. [less ▲]

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See detailRuolo del gene AIRE nel melanoma
Conteduca, Giuseppina ULg

Doctoral thesis (2010)

Polymorphisms of AIRE, a transcription factor that up-regulates intrathymic expression of tissue-specific antigens including melanoma-associated antigens (MAAs), may variably affect the selection of MAAs ... [more ▼]

Polymorphisms of AIRE, a transcription factor that up-regulates intrathymic expression of tissue-specific antigens including melanoma-associated antigens (MAAs), may variably affect the selection of MAAs-specific thymocytes, generating T-cell repertoires protecting or predisposing individuals to melanoma. We found that AIRE single nucleotide polymorphisms (SNPs) rs1055311, rs1800520 and rs1800522 were significantly more frequent in healthy subjects than in melanoma patients, independently from sex, age and stages of melanoma. The presence of these SNPs was associated with increased frequency of two T-cell clonotypes specific for MAGE-1 linking their protective effect to selection/expansion of MAA-specific T cells. Interestingly, mRNA transcribed on the rs1800520 SNP showed increased free energy than the wild type suggesting that its reduced stability may be responsible for the different activity of the polymorphic AIRE molecule. This finding may contribute at identifying subjects with increased risk of developing melanoma or patients with melanoma that may take benefit from immunotherapy. [less ▲]

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See detailCost Effectiveness and Complexity Assessment in Ship Design within a Concurrent Engineering and "Design for X" Framework
Caprace, Jean-David ULg

Doctoral thesis (2010)

Decisions taken during the initial design stage determine 60% to 95% of the total cost of a product. So there is a significant need to concurrently consider performance, cost, production and design ... [more ▼]

Decisions taken during the initial design stage determine 60% to 95% of the total cost of a product. So there is a significant need to concurrently consider performance, cost, production and design complexity issues at the early stages of the design process. The main obstacle to this approach is the lack of convenient and reliable cost and performance models that can be integrated into a complex design process as is used in the shipbuilding industry. Traditional models and analysis methods frequently do not provide the required sensitivity to consider all the important variables impacting performance, cost, production and ship’s life cycle. Our challenge is that achieving this sensitivity at the early design stage almost requires data available during the detail design analysis. The traditional design methods do not adequately include, early enough, production and life cycle engineering to have a positive impact on the design. Taking an integrated approach throughout the life cycle of the ship and using concurrent engineering analysis tools can improve these traditional design process weaknesses. Innovation is required in structural design and cost assessment. The use of design for X, and particular design for production and cost schemes, during the design is the solution: to reduce failure during a ship’s life caused by design misconception, to reduce the overall design time and to shorten the build cycle of ships, to enlarge the number of design alternatives during the design process. The author has developed some assessment methods for cost effectiveness and complexity measurements intended to be used by ship designers for the real time control of cost process. The outcome is that corrective actions can be taken by management in a rather short time to actually improve or overcome predicted unfavourable performance. Fundamentally, these methods will provide design engineers with objective and quantifiable cost and complexity measures making it possible to take rational design decisions throughout the design stages. The measures proposed in this PhD are based on several techniques like decision analysis, data mining, neural network, fuzzy logic. They are objective facts, which are not dependent on the engineer’s interpretation of information, but rather on a model generated to represent the ship design. The objectivity aspect is essential when using the complexity and cost measures in a design automation system. Finally, with these tools, the designers should obtain well-defined and unambiguous metrics for measurement of the different types of cost effectiveness and complexities in engineered artefacts. Such metrics help the designers and design automation tools to be objective and perform quantitative comparisons of alternative design solutions, cost estimation, as well as design optimization. In this PhD, these metrics have been applied and validated with success in real industrial conditions on the design of passenger ships. [less ▲]

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See detailImpact of climate change on groundwater reserves
Goderniaux, Pascal ULg

Doctoral thesis (2010)

Estimating the impacts of climate change on groundwater represents one of the most difficult challenges faced by water resources specialists. One difficulty is that simplifying the representation of the ... [more ▼]

Estimating the impacts of climate change on groundwater represents one of the most difficult challenges faced by water resources specialists. One difficulty is that simplifying the representation of the hydrological system, or using too simple climate change scenarios often leads to discrepancies in projections. Additionally, these projections are affected by uncertainties from various sources, and these uncertainties are not evaluated in previous studies. In this context, the objective of this study is to provide an improved methodology for the estimation of climate change impact on groundwater reserves, including the evaluation of uncertainties. This methodology is applied to the case of the Geer basin catchment (480 km²) in Belgium. A physically-based surface-subsurface flow model has been developed for the Geer basin with the finite element model HydroGeoSphere. The simultaneous solution of surface and subsurface flow equations in HydroGeoSphere, as well as the internal calculation of the actual evapotranspiration as a function of the soil moisture at each node of the defined evaporative zone, improve the representation and calibration of interdependent processes like recharge, which is crucial in the context of climate change. Fully-integrated surface-subsurface flow models have recently gained attention, but have not been used in the context of climate change impact studies. This surface-subsurface flow model is combined with advanced climate change scenarios for the Geer basin. Climate change simulations were obtained from six regional climate model (RCM) scenarios assuming the SRES A2 greenhouse gases emission (medium-high) scenario. These RCM scenarios were statistically downscaled using two different methods: the 'Quantile Mapping Biased Correction' technique and a 'Weather Generator' technique. Both of them are part of the most advanced downscaling techniques. They are able to apply corrections not only to the mean of climatic variables, but also across the statistical distributions of these variables. This is important as these distributions are expected to change in the future, with more violent rainfall events, separated by longer dry periods. The 'quantile mapping bias-correction' technique generate climate change time series representative of a stationary climate for the periods 2011-2040, 2041-2070 and 2071-2100. The 'CRU' weather generator is used to generate a large number of equiprobable scenarios simulating full transient climate change between 2010 and 2085. All these scenarios are applied as input of the Geer basin model. The uncertainty is evaluated from different possible sources. Using a multi-model ensemble of RCMs and GCMs enables to evaluate the uncertainty linked to climatic models. The application of a large number of equiprobable climate change scenarios, generated with the 'weather generator', as input of the hydrological model allows assessing the uncertainty linked to the natural variability of the weather. Finally, the uncertainty linked to the calibration of the hydrological model is evaluated using the computer code 'UCODE_2005'. The climate change scenarios for the Geer basin model predict hotter and drier summers and warmer and wetter winters. Considering the results of this study, it is very likely that groundwater levels and surface flow rates in the Geer basin will decrease. This is of concern because it also means that groundwater quantities available for abstraction will also decrease. However, this study also shows that the uncertainty surrounding these projections is relatively large and that it remains difficult to state on the intensity of the decrease. [less ▲]

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See detailLilia florent : l’imaginaire politique et social à la cour de France durant les premières Guerres d’Italie (1494-1525)
Dumont, Jonathan ULg

Doctoral thesis (2010)

Ces dernières années, l’historiographie des premières Guerres d’Italie (1494-1525) s’est considérablement enrichie notamment grâce aux études de D. Le Fur, N. Hochner, A.-M. Lecoq et R. W. Scheller ... [more ▼]

Ces dernières années, l’historiographie des premières Guerres d’Italie (1494-1525) s’est considérablement enrichie notamment grâce aux études de D. Le Fur, N. Hochner, A.-M. Lecoq et R. W. Scheller. Croisant délibérément des sources variées (littéraires, politiques et iconographiques) ainsi que les méthodes (celle de l’historien des textes et celle de l’historien d’art), leurs travaux se sont attachés à définir les différents aspects du pouvoir royal et la manière dont celui-ci se met en scène tout spécialement sous les règnes de Charles VIII, de Louis XII et de François Ier. Force est donc de constater que la figure du roi de France domine l’historiographie récente des premières Guerres d’Italie. Pourtant, à chaque fois que les souverains des fleurs de lys sont mis en scène, ils n’occupent pas seuls le discours politique. D’autres personnages, la France et les Français, apparaissent à côté d’eux. Le premier est dépeint, selon une tradition établie, comme un espace bénéficiant de qualités exceptionnelles. Lesdites qualités conditionnent la nature du deuxième personnage – les Français –, lequel s’intègre dès lors à un portrait de la nation. Durant les Guerres d’Italie, ce discours sur la France et les Français ne sert pas uniquement à décrire le royaume lui-même. Il permet avant tout aux artisans de la propagande royale d’élaborer une pensée légitimant la conquête de l’Italie et permettant d’y imposer une nouvelle culture politique et sociale d’inspiration française. Cet amalgame d’images à propos de l’Italie française ou Franco-Italia traverse l’ensemble de la période, croisant parfois la figure royale, mais s’en éloignant aussi très souvent. L’étude d’une telle idéologie révèle enfin un intérêt supplémentaire. Au cours des premières décennies du XVIe siècle, la France connaît un véritable bouleversement de son modèle d’organisation sociale traditionnel. Nous voulons parler des trois ordres du féodalisme (oratores, bellatores et laboratores). Certes, dans la réalité quotidienne, le système ternaire ne reflète plus, depuis des siècles, la complexité des relations politiques et sociales. Par contre, la remise en cause de ce modèle au sein de la pensée politique curiale, en somme dans la culture de l’élite, est une donnée relativement nouvelle en ce début de XVIe siècle. Ainsi, le discours sur l’Italie française sert de champ d’expérimentation aux théoriciens du politique, aux polémistes ainsi qu’aux chroniqueurs et même aux poètes, leur permettant de redéfinir les contours d’un schéma ternaire qui, dans sa forme traditionnelle, leur apparaît désuet. On l’aura compris : notre thèse s’oriente donc vers l’étude, non d’un seul mode de pensée, mais plutôt d’une pluralité de concepts et d’opinions ayant comme dénominateur commun la redéfinition des contours de l’Italie et également de la France. Il s’agira de comprendre la manière dont les auteurs de la cour de France regardent la Péninsule et ses habitants et comment, de cette expérience de l’altérité, ils en arrivent à pratiquer un retour sur eux-mêmes et à relire leur propre mode d’organisation sociale, autrement dit, les cadres théoriques de leur existence. Cette histoire des lys qui s’évertuent à fleurir dans les champs d’une Italie pourtant bien décidée à les faucher sera l’occasion d’entrevoir sous un angle neuf cette période de bouleversements et d’inquiétudes que sont les premières Guerres d’Italie. [less ▲]

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See detailEssays in Empirical Finance: Portfolio Risk and Performance Management
Bodson, Laurent ULg

Doctoral thesis (2010)

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See detailEvaluation économique de la prise en charge de l'ostéoporose
Hiligsmann, Mickaël ULg

Doctoral thesis (2010)

Health economic evaluation is a method for evaluating the value for money of medical technologies by comparing alternative options in terms of their costs and consequences. This method is frequently used ... [more ▼]

Health economic evaluation is a method for evaluating the value for money of medical technologies by comparing alternative options in terms of their costs and consequences. This method is frequently used to inform decision makers about how to allocate scarce resources. Economic evaluation has become increasingly important nowadays, with the increasing health care expenditures, the rapid introduction of new medical technologies, and the extending role of economic evaluations in health care decision making. Osteoporosis becomes an increasingly major health problem around the world. It is a disease characterized by low bone mass with microarchitectural disruption and increased skeletal fragility, leading to increased fracture risk. Osteoporotic fractures result in significant morbidity and mortality, and impose a huge financial burden on health care systems. Financial resources are used to prevent, diagnose and treat osteoporosis. These resources must be allocated in an efficient manner. The general purpose of this thesis is therefore to contribute to the economic evaluation of osteoporosis management. More specifically, this thesis is divided into four parts. The first part is devoted to the development and the validation of a new Markov microsimulation model. This modelling approach accurately encompasses the complexity of osteoporosis, increasing the reliability of the results. The second part estimates the cost-effectiveness of osteoporosis screening strategies and provides recommendations for their implementation. The third part estimates the cost-effectiveness of new anti-osteoporotic therapies (strontium ranelate and denosumab). It is important to assess whether new drugs represent a good value for money compared to the relevant alternatives. Finally, the last part of the thesis investigates the clinical and economic implications of non-adherence to osteoporosis medications. This thesis provides new information on the cost-effectiveness of osteoporosis management, which may be useful to inform decisions makers about resources allocation for patients with osteoporosis. The results may also be used to raise awareness among public health authorities, the medical profession and the general population regarding the burden of osteoporosis, the importance of screening and adequate follow-up, as well as to the role of economic evaluation in health care decision making. [less ▲]

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See detailCaracterización funcional de Snail2 como represor de cadherina- E y como regulador del proceso de carcinogenésis química
Molina Ortiz, Patricia ULg

Doctoral thesis (2010)

The loss of expression of intercellular adhesion protein E-cadherin is a key event in the process of epithelial-mesenchymal transition (EMT), which allows cell migration during embryonic development and ... [more ▼]

The loss of expression of intercellular adhesion protein E-cadherin is a key event in the process of epithelial-mesenchymal transition (EMT), which allows cell migration during embryonic development and invasion of tumor cells of epithelial origin (carcinomas). The transcriptional repression is one of the main mechanisms of negative regulation of E-cadherin expression in both embryonic development and during tumor progression. In recent years there has been identified different transcriptional repressors of E-cadherin gene, which in turn induce TEM, including factors the zinc finger family of Snail (Snail1 and Snail2) and ZEB (ZEB - 1 and ZEB-2) and factors of the bHLH family (E47 and Twist). Previous studies of our laboratory, comparing gene expression profiles analysis of MDCK-II cells with stable expression of Snail1, Snail2 or E47 identified different genetic programs induced by each of these factors. These differences indicate that factors Snail1, Snail2 and E47 are regulating specific genetic programs that can modify the invasive capacity, migratory, proliferative and angiogenic capacity of cells that overexpress each of these factors. These results are consistent with the functional differences between these factors during embryonic development and tumor progression. This thesis analyzed the transcriptional mechanisms used by Snail2 for transcriptional repression of E-cadherin and its role in the induction of carcinomas in mice. Biochemical studies showed that Snail2 required the SNAG (Snail common domain and Gfi-1) and SLUG domains for the recruitment of different co-repressors, such as mSin3A, NCoR and CtBP1, and that these co-repressors functionally interact during transcriptional repression -E-cadherin. We have also identified in Snail2 different phosphorylated residues in vivo that can regulate the activity of Snail2. Finally, functional analysis of zinc fingers revealed that while the second zinc finger is essential for the repression activity of Snail2, the fifth zinc finger has a promoter context-dependent function, by altering the Snail2 capacity of repression dependent of the promoter. These results highlight differences and similarities between the mechanisms of transcriptional repression of Snail and Snail2, supporting the functional differences between the two. Animal model studies showed that Snail2 is essential for the survival and differentiation of keratinocytes. However, the absence of Snail2 increases the occurrence and malignant progression of carcinomas in the chemical carcinogenesis model in mouse skin. The anti-inflammatory treatment reduces malignant progression but not the emergence and growth of benign lesions. These results indicate that the absence of Snail2 during carcinogenesis promotes inflammatory processes that alter the terminal differentiation and proliferation capacity of keratinocytes by promoting carcinogenesis. [less ▲]

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See detailEtude de l'hydrodynamique dans une colonne de distillation réactive: Mesure de la distribution des phases par tomographie à rayons X.
Aferka, Saïd ULg

Doctoral thesis (2010)

Le mémoire concerne l’étude de l’hydrodynamique des écoulements dans des lits fixes parcourus par un écoulement à contre courant de gaz et de liquide. Il est plus particulièrement consacré à l’analyse par ... [more ▼]

Le mémoire concerne l’étude de l’hydrodynamique des écoulements dans des lits fixes parcourus par un écoulement à contre courant de gaz et de liquide. Il est plus particulièrement consacré à l’analyse par tomographie à rayons X de la distribution spatiale des phases liquide et solide dans des empilages de distillation et de distillation réactive. Le principe de la distillation réactive est de réaliser, dans une même colonne, une réaction chimique exothermique et la séparation des produits par distillation. L’industrie chimique marque beaucoup d’intérêt pour ce type d’appareil en raison des nombreux avantages qu’il offre : une réduction des investissements, puisqu’un seul appareil est utilisé au lieu de deux ; une très grande intégration énergétique des étapes de réaction et de séparation, puisque la chaleur générée par la réaction est directement utilisée pour la distillation ; la possibilité d'augmenter la conversion dans le cas des réactions limitées à l'équilibre ; … Les empilages utilisés en distillation réactive présentent généralement une structure modulaire. Chaque élément comporte une ou plusieurs zones catalytiques, dans lesquelles la réaction se déroule et une ou plusieurs zones de séparation, où la distillation peut être réalisée. Vu la structure extrêmement complexe de ces empilages, la compréhension et la description des écoulements en leur sein sont des tâches particulièrement ardues que très peu d’équipes de recherches ont entamées jusqu’à présent. Le but du présent travail de thèse est de collecter une information expérimentale aussi précise et aussi complète que possible, permettant de déterminer les mécanismes hydrodynamiques qui interviennent dans les empilages de distillation réactive. La tomographie à rayons X est utilisée pour mesurer la distribution des phases à différentes échelles, depuis l’échelle locale des détails de l’empilage, jusqu’à l’échelle de la colonne dans son ensemble. Les résultats obtenus permettent non seulement de quantifier les grandeurs hydrodynamiques macroscopiques comme la rétention ou l’aire interfaciale mais, ils permettent également et surtout d’expliquer leur évolution en fonction de la structure de l’empilage et des conditions opératoires. [less ▲]

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See detailExplaining Organisational Diversity in Fair Trade Social Enterprises
Huybrechts, Benjamin ULg

Doctoral thesis (2010)

This research aims to explain and understand the organisational diversity observed in the field of Fair Trade Social Enterprises or Fair Trade Organisations (FTOs). The transversal hypothesis is that such ... [more ▼]

This research aims to explain and understand the organisational diversity observed in the field of Fair Trade Social Enterprises or Fair Trade Organisations (FTOs). The transversal hypothesis is that such a diversity in organisational forms may be linked to the multidimensional (economic, social and/or political) nature of Fair Trade. First, since there are virtually no typologies focused on FTOs, it is necessary to look at how organisational diversity in FT can be categorised. A typology with five categories of organisational forms is suggested. Secondly, this work explores the reasons behind organisational diversity, using both an external, explanatory perspective, and an internal, interactionist perspective. A third key issue is to explore whether FTOs experience tensions between the different dimensions of FT, and how these tensions are managed in the different types of FTOs. These issues are examined under the light of different theoretical approaches linked to “new institutionalism” (economic, sociological and entrepreneurial) and resource dependence theory. The empirical material is provided by interviews with the leaders of 57 FTOs in four European regions: Belgium, France (Rhône-Alpes), the United Kingdom (England) and Italy (Rome). Eight of these FTOs, reflecting the different categories of organisational forms, are analysed more in depth. [less ▲]

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See detailMulti-scale modelling of shell failure for periodic quasi-brittle materials
Mercatoris, Benoît ULg

Doctoral thesis (2010)

In a context of restoration of historical masonry structures, it is crucial to properly estimate the residual strength and the potential structural failure modes in order to assess the safety of buildings ... [more ▼]

In a context of restoration of historical masonry structures, it is crucial to properly estimate the residual strength and the potential structural failure modes in order to assess the safety of buildings. Due to its mesostructure and the quasi-brittle nature of its constituents, masonry presents preferential damage orientations, strongly localised failure modes and damage-induced anisotropy, which are complex to incorporate in structural computations. Furthermore, masonry structures are generally subjected to complex loading processes including both in-plane and out- of-plane loads which considerably influence the potential failure mechanisms. As a consequence, both the membrane and the flexural behaviours of masonry walls have to be taken into account for a proper estimation of the structural stability. Macrosopic models used in structural computations are based on phenomenological laws including a set of parameters which characterises the average behaviour of the material. These parameters need to be identified through experimental tests, which can become costly due to the complexity of the behaviour particularly when cracks appear. The existing macroscopic models are consequently restricted to particular assumptions. Other models based on a detailed mesoscopic description are used to estimate the strength of masonry and its behaviour with failure. This is motivated by the fact that the behaviour of each constituent is a priori easier to identify than the global structural response. These mesoscopic models can however rapidly become unaffordable in terms of computational cost for the case of large-scale three-dimensional structures. In order to keep the accuracy of the mesoscopic modelling with a more affordable computa- tional effort for large-scale structures, a multi-scale framework using computational homogeni- sation is developed to extract the macroscopic constitutive material response from computa- tions performed on a sample of the mesostructure, thereby allowing to bridge the gap between macroscopic and mesoscopic representations. Coarse graining methodologies for the failure of quasi-brittle heterogeneous materials have started to emerge for in-plane problems but remain largely unexplored for shell descriptions. The purpose of this study is to propose a new periodic homogenisation-based multi-scale approach for quasi-brittle thin shell failure. For the numerical treatment of damage localisation at the structural scale, an embedded strong discontinuity approach is used to represent the collective behaviour of fine-scale cracks using average cohesive zones including mixed cracking modes and presenting evolving orientation related to fine-scale damage evolutions. A first originality of this research work is the definition and analysis of a criterion based on the homogenisation of a fine-scale modelling to detect localisation in a shell description and determine its evolving orientation. Secondly, an enhanced continuous-discontinuous scale tran- sition incorporating strong embedded discontinuities driven by the damaging mesostructure is proposed for the case of in-plane loaded structures. Finally, this continuous-discontinuous ho- mogenisation scheme is extended to a shell description in order to model the localised behaviour of out-of-plane loaded structures. These multi-scale approaches for failure are applied on typical masonry wall tests and verified against three-dimensional full fine-scale computations in which all the bricks and the joints are discretised. [less ▲]

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See detailIdentification des menaces sur la diversité floristique des pelouses calcicoles de Belgique et opportunités pour la restauration : de l'espèce au paysage
Piqueray, Julien ULg

Doctoral thesis (2010)

Current human activities can be responsible either of the loss or promotion of biodiversity at the regional scale. The study of the influence of human activities on patterns of biological diversity is ... [more ▼]

Current human activities can be responsible either of the loss or promotion of biodiversity at the regional scale. The study of the influence of human activities on patterns of biological diversity is therefore of primary importance in order to set up conservation strategies. We studied the influence of human activities on calcareous grassland floristic diversity in Belgium. During the past century, a high fragmentation of this habitat occurred within the study region. There was a delay between the process of fragmentation and the subsequent response in terms of species richness, which created an “extinction debt” in remnant calcareous grasslands. Although fragmentation was the main process involved, we also showed that some new habitat patches were created thanks to human activities during this period. These new habitat patches exhibited a species richness and composition that was found similar to old habitat patches. In the face of fragmentation, restoration programs were launched in the study region. Restored areas exhibited similar soil conditions as compared to reference grasslands. Plant species communities found in the oldest restorations tend to resemble reference grassland communities. However, some differences in species composition persisted after 15 years. It was also shown that some species did not colonize restored sites at all. With this respect, seed and germination microsite availability could be limiting factors for the colonization of restored sites. However, the absence or the lower colonization in restored areas compared to reference grasslands following seed addition and disturbance suggested that habitat quality could be considered as lower in restored habitats. Our results suggest therefore that restoration effort should be maintain in the study site. This effort is not vain as many species are able to colonize newly created sites. Finally, another threat to calcareous grasslands was studied i.e. the naturalization of the ornamental species Cotoneaster horizontalis. The analysis revealed that, although being at an early stage of naturalization, the species had an impact on vegetation structure and composition and on grassland diversity. Trade limitation for this species should be promoted in addition to management. [less ▲]

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See detailThérapie cellulaire de réparation tissulaire cardiaque par cellules souches hématopoïétiques et mésenchymateuses.
DELGAUDINE, Marie ULg

Doctoral thesis (2010)

Les scientifiques définissent les cellules souches (CS) en se basant sur 3 critères (Fig.1): (1) les CS sont douées de capacités d’auto-renouvellement qui leur permettent de maintenir leur « pool » stable ... [more ▼]

Les scientifiques définissent les cellules souches (CS) en se basant sur 3 critères (Fig.1): (1) les CS sont douées de capacités d’auto-renouvellement qui leur permettent de maintenir leur « pool » stable ; (2) une CS peut se différencier en plusieurs types de cellules fonctionnelles matures. Par exemple, les cellules souches hématopoïétiques (CSH) sont à l’origine des cellules sanguines ; les cellules souches neurales (CSN) donnent naissance aux neurones, astrocytes et oligodendrocytes ; les cellules souches mésenchymateuses (CSM) peuvent se différencier en fibroblastes, ostéoblastes, chondroblastes et adipocytes ; (3) les cellules souches peuvent repeupler un tissu lésé pour en restaurer la fonction, comme notamment, après une irradiation. [less ▲]

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See detailRic-8: un nuevo GEF con estructura tipo "armadillo"
Figueroa, Maximiliano ULg

Doctoral thesis (2010)

RIC-8 is a highly conserved cytosolic protein (63 KDa) initially identified in C. elegans as an essential factor in neurotransmitter release and asymmetric cell division. Two different isoforms have been ... [more ▼]

RIC-8 is a highly conserved cytosolic protein (63 KDa) initially identified in C. elegans as an essential factor in neurotransmitter release and asymmetric cell division. Two different isoforms have been described in mammals, RIC-8A and RIC-8B; each possess guanine nucleotide exchange activity (GEF) on heterotrimeric G-proteins, but with different Gα subunits specificities. To gain insight on the mechanisms involved in RIC-8 cellular functions it is essential to obtain some information about its structure. Therefore, the aim of this thesis was to study the relationship between structure and function on RIC-8, using as model RIC-8 from X. laevis. Analysis in its primary structure did not give us information about the function of xRIC-8 and RIC-8 proteins were showed as a single family without similarity with others. For this reason, to obtain a 3D model of xRIC-8, different bioinformatics approaches that include protein folding and structure prediction were used. The RIC-8 structural model is composed of 10 armadillo folding motifs, organized in a right-twisted alpha-alpha super helix. In order to validate the structural model, a His-tag fusion construct of RIC-8 was expressed in E. coli, purified by affinity and anion exchange chromatography and subjected to circular dichroism analysis (CD) and thermostability studies. This model together with the comparison among RIC-8 proteins that shows a high conservation in the carboxy region, deletion mutants that remove the last three armadillo domain were created in order to search a loss of the GEF function. The mutants could not be expressed in bacteria for in vitro assays, but their expression in HEK293T culture showed that all of them preserved the GEF activity. Furthermore, confocal microscopy showed that all the mutants could translocate to plasmatic membrane under stimulation with isoproterenol, and have the capacity to interact with Gs. The results of this thesis has allowed present the first 3D model for a RIC-8 protein, as well as classify RIC-8 as a new member of the protein family with armadillo repeats. Functionally, the carboxi terminal region, the most conserved among RIC-8, did not show has the GEF activity, and did not alter its behavior in HEK293T cell cultures while was stimulated with isoproterenol. [less ▲]

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See detailStudy of the Mechanism of the Coal Analysis by Laser-Induced Breakdown Spectroscopy
Li, Jie ULg

Doctoral thesis (2010)

The elemental composition of the coal is one of the necessary data for the thermal calculation and combustion adjustment of the boiler. The traditional coal analysis methods are usally off-line and ... [more ▼]

The elemental composition of the coal is one of the necessary data for the thermal calculation and combustion adjustment of the boiler. The traditional coal analysis methods are usally off-line and couldn’t offer the real-time data of the coal, so they couldn’t satisfy the needs of the combustion adjustment and accident analysis of the boiler and have a lot of limitations. Therefore, it is necessary to develop a new technology which can analyze the coal rapidly. Laser-induced breakdown spectroscopy (LIBS) is a new technology which has the advantages of the quick and multi-elemental analysis, thus it can be applied for the coal analysis. The theoretical analysis and experimental research are used in the thesis, and they will provide the experimental basis and theoretical foundation for the coal analysis by LIBS. The current researches both at home and abroad of the applications of the LIBS technique on the coal-fired field are analyzed in this thesis, and the key problems of the current researches are summarized. The mechanism of the production and evolution of the plasma of the coal is very important. The amounts of the main elements which need to be measured of the coal are more than ten, and it is hard to achieve the multi-elemental analysis. On the other hand, the C, H and O elements are hard to excite and ionize, but the canlibration and quantitative analysis of them are most important. However, these contents are closely related to the practical application of the LIBS technique on the coal analysis. According to these key problems, a series of researches will be carried on in this thesis: The LIBS set-up for the coal analysis is established, and the typical Shenhua bituminous coal is chosen as the object. The time evolution process of the continuous spectrum and the atomic emission line of C I 247.9nm are analyzed, and the formation mechanisms of the spectral lines in each stages from the production to the annihilation of the plasma of the coal are discussed. Moreover, the difference of the evolution processes between the plasmas from the coal and the copper is compared, and the influence of the volatile in the coal to the plasma is discussed. These researches provide the experimental platform and theoretical basis for designing the coal analysis instrumentation by LIBS. The influence of the excitation and ionization property of the elements on the plasma is analyzed. The suitable delay time and gate width are selected for the purpose of the multi-elemental analysis of the coal by means of a series of experimental researches on the time evolution processes of different emission lines. The experiments on the coal are performed by changing the parameters including the laser energy, the lens focal plane position and the number of averages, and the influence of the parameters on the intensity and repeatability of the emission lines are analyzed. On this basis, the optimum parameters are determined. Four bituminous coals from different mines in China are checked by using the optimum parameters, and the result shows that the line intensities are strong and the reproducibilities are high. These researches supply the experimental foundation and technical parameters for designing the coal analysis instrumentation by LIBS. The C, H and O elements in the coal are closely related to the combustion, but the sensitivities of their emission lines are low and the results of the calibration curves are not good. In view of these problems, the atomic line of Si I 288.2nm is chosen as the internal standard line, and the internal standard curves of C I 247.9nm, H I 656.3nm and O I 777.4nm are obtained and the calibration results are good. Moreover, in order to avoid the disturbtion of the analysis of the O element from the air, the method of blowing the argon is used in this thesis. The result shows that the interference to the O element is inexistence and the line intensities of the coal are stronger when using the argon. It is found that the calibration results of the C, H and O elements in argon are better than in air. These researches provide the proper calibration method for the quantitative analysis of the C, H and O elements in the coal. The quantitative analysis is the final purpose of the LIBS technique that applied to the coal-fired field. The conventional quantitative analysis methods are analyzed. The quantitative analysis of the minor elements in the coal is completed by using the calibration curve method, and the result shows the accuracies are high. The quantitative analysis of the C, H and O elements in coal is finished by using the internal standard curve method, and the result shows the accuracies are just passable. The quantitative analysis of the C elment in the coal ash is accomplished by using the internal standard curve method too, and the result shows that the LIBS technique has the applicability for the measurement of the C elment in the coal ashes which come from different coal samples. These researches supply the database for designing the coal analysis instrumentation by LIBS. Finally, the research works in this thesis are summaried and some advices are given for the further research works. [less ▲]

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See detailMieux comprendre le savoir-agir autonome - Développement et analyse d'usages d'un environnement d'apprentissage destiné aux élèves de 10 à 15 ans
Georges, François ULg

Doctoral thesis (2010)

Analyse du potentiel autonomisant d'un environnement d'apprentissage en ligne destiné aux élèves de 10 à 15 ans

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See detailLearning of Multi-Dimensional, Multi-Modal Features for Robotic Grasping
Detry, Renaud ULg

Doctoral thesis (2010)

While robots are extensively used in factories, our industry hasn't yet been able to prepare them for working in human environments - for instance in houses or in human-operated factories. The main ... [more ▼]

While robots are extensively used in factories, our industry hasn't yet been able to prepare them for working in human environments - for instance in houses or in human-operated factories. The main obstacle to these applications lies in the amplitude of the uncertainty inherent to the environments humans are used to work in, and in the difficulty in programming robots to cope with it. For instance, in robot-oriented environments, robots can expect to find specific tools and objects in specific places. In a human environment, obstacles may force one to find a new way of holding a tool, and new objects appear continuously and need to be dealt with. As it proves difficult to build into robots the knowledge necessary for coping with uncertain environments, the robotics community is turning to the development of agents that acquire this knowledge progressively and that adapt to unexpected events. This thesis studies the problem of vision-based robotic grasping in uncertain environments. We aim to create an autonomous agent that develops grasping skills from experience, by interacting with objects and with other agents. To this end, we present a 3D object model for autonomous, visuomotor interaction. The model represents grasping strategies along with visual features that predict their applicability. It provides a robot with the ability to compute grasp parameters from visual observations. The agent acquires models interactively by manipulating objects, possibly imitating a teacher. With time, it becomes increasingly efficient at inferring grasps from visual evidence. This behavior relies on (1) a grasp model representing relative object-gripper configurations and their feasibility, and (2) a model of visual object structure, which aligns the grasp model to arbitrary object poses (3D positions and orientations). The visual model represents object edges or object faces in 3D by probabilistically encoding the spatial distribution of small segments of object edges or the distribution of small patches of object surface. A model is learned from a few segmented 3D scans or stereo images of an object. Monte Carlo simulation provides robust estimates of the object's 3D position and orientation in cluttered scenes. The grasp model represents the likelihood of success of relative object-gripper configurations. Initial models are acquired from visual cues or by observing a teacher. Models are then refined autonomously by ``playing' with objects and observing the effects of exploratory grasps. After the robot has learned a few object models, learning becomes a combination of cross-object generalization and interactive experience: grasping strategies are generalized across objects that share similar visual substructures; they are then adapted to new objects through autonomous exploration. The applicability of our model is supported by numerous examples of pose estimates in cluttered scenes, and by a robot platform that shows increasing grasping capabilities as it explores its environment. [less ▲]

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See detailLE FONCTIONNEMENT EXECUTIF CHEZ L’ENFANT APPROCHE DEVELOPPEMENTALE ET NEUROPSYCHOLOGIQUE
Catale, Corinne ULg

Doctoral thesis (2010)

Dans la cadre de ce travail de thèse dont l’objectif principal est de contribuer à une meilleure compréhension du fonctionnement exécutif, nous avons adopté une perspective développementale et ... [more ▼]

Dans la cadre de ce travail de thèse dont l’objectif principal est de contribuer à une meilleure compréhension du fonctionnement exécutif, nous avons adopté une perspective développementale et neuropsychologique. Ce travail s’articule dès lors en deux parties. L’objectif principal de la première partie est de viser à une meilleure compréhension du développement de certaines fonctions exécutives chez des enfants d’âge préscolaire et scolaire (Etudes 1 et 2) et de déterminer la structure factorielle de ces fonctions dans le développement (Etude 2). La troisième étude vise quant à elle à mieux comprendre l’influence de l’environnement socio-culturel, et plus spécifiquement du niveau éducationnel parental, sur le développement de certaines fonctions cognitives (en ce compris les fonctions exécutives). L’objectif principal de la deuxième partie est, quant à lui, de déterminer le profil attentionnel et exécutif d’enfants victimes d’un traumatisme crânien ou qui présentent un trouble de l’attention avec/sans hyperactivité. Dans cette optique, nous évaluerons d’une part différentes fonctions attentionnelles et exécutives, et d’autre part les changements comportementaux chez des enfants victimes d’un traumatisme crânien léger (Etude 4). Enfin, et de façon plus spécifique, nous tenterons de mieux comprendre les difficultés d’inhibition présentées par des enfants qui ont été victimes d’un traumatisme crânien modéré à sévère (Etude 5) ou qui présentent un trouble de l’attention avec/sans hyperactivité (Etude 6). [less ▲]

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See detailIdentification d’une nouvelle molécule d’intérêt chez le cheval atteint d’obstruction récurrente des voies respiratoires: La Pentraxine 3
Ramery, Eve ULg

Doctoral thesis (2010)

L’ORVR ou obstruction récurrente des voies respiratoires (ORVR) est la cause la plus fréquente de maladie pulmonaire chronique chez le cheval adulte. La maladie se caractérise par une hyperréactivité ... [more ▼]

L’ORVR ou obstruction récurrente des voies respiratoires (ORVR) est la cause la plus fréquente de maladie pulmonaire chronique chez le cheval adulte. La maladie se caractérise par une hyperréactivité bronchique, une production excessive de mucus et une inflammation neutrophilique pulmonaire qui ont pour effet de réduire la compliance dynamique du poumon et d’augmenter la résistance des voies respiratoires au débit aérien. Alors que la maladie est une entité documentée dans la littérature depuis plus de 200 ans, les mécanismes moléculaires qui la sous-tendent restent incomplètement élucidés à ce jour. De précédentes études ont montré l'implication de variations d'expression génique, pour la plupart grâce à l'utilisation combinée de la transcription inverse et de la réaction en chaîne par polymérase (RT-PCR). Cette technique bien connue ne permet l'étude que d'un nombre limité de gènes en simultané. Les microdamiers apparaissent comme la technique de choix pour l'étude de l'expression génique à large échelle. A l’heure où cette étude a débuté, il n’existait pas de microdamier d’expression spécifiquement dédié au cheval sur le marché. Un microdamier hétérologue humain (Human Genome U133 Plus 2.0 GeneChip, Affymetrix®) a donc été utilisé pour tenter d’identifier de nouveaux gènes d’intérêt pour comprendre la pathogénie de l’ORVR chez le cheval. L'utilisation du microdamier a permis de détecter 46 gènes dont l’expression variait d'un facteur supérieur à 4 entre chevaux sains et atteints. Parmi les gènes mis en avant par le microdamier, trois gènes (CYBB, MARCKS et PTX3) présentaient un intérêt particulier au regard de la littérature et leur variation d’expression a été confirmée par RT-PCR quantitative (RT-qPCR). La pentraxine 3 (PTX3) notamment appartient à la composante humorale de la réponse immune innée. Elle agit comme un ancêtre fonctionnel des anticorps. En effet, elle reconnaît les microbes, active le complément et facilite la reconnaissance de certains pathogènes spécifiques, dont Aspergillus fumigatus (A. fumigatus), par les phagocytes. La suite du travail s’est donc focalisée sur PTX3. L’ADN complémentaire (ADNc) codant pour PTX3 et l’ADN codant pour le second exon de PTX3 ont été clonés et séquencés. L’ADN codant pour le second exon de PTX3 équin présentait une délétion de 120 paires de bases par rapport à la séquence humaine. Par ailleurs, un épissage alternatif du second exon de PTX3 a été mis en évidence, résultant en deux formes de la protéine, "épissée" (32 kilodaltons) et "complète" (42 kilodaltons). Afin d'étudier les effets de l’exposition à des poussières de foin sur l'expression de PTX3 dans les voies respiratoires, six chevaux sains et six chevaux atteints d’ORVR ont été soumis pendant dix jours à un challenge environnemental aux poussières de foin. Les chevaux ont été étudiés via des tests cliniques, fonctionnels et biochimiques. Les lavages broncho-alvéolaires (LBA) ont été récoltés lors de l'initiation du protocole et après les dix jours d'exposition aux poussières de foin. Par ailleurs, des sections bronchiques ont été réalisées chez deux chevaux atteints d'ORVR en crise et euthanasiés pour raisons éthiques et deux chevaux indemnes d'affections respiratoires provenant de l'abattoir. PTX3 était détectée dans les macrophages du LBA après exposition aux poussières de foin et dans les cellules épithéliales bronchiques. PTX3 était surexprimée dans les macrophages du LBA chez tous les chevaux après dix jours d'exposition aux poussières de foin. Cependant, le niveau de PTX3 était plus élevé dans le surnageant des cellules provenant des chevaux atteints d'ORVR que dans celui provenant des cellules des chevaux sains. Par ailleurs, il semble que PTX3 soit surexprimée dans les cellules épithéliales bronchiques chez le cheval atteint d'ORVR. Cette piste est intéressante sur le plan thérapeutique puisque l'activation de l'expression de PTX3 dans les cellules épithéliales bronchiques est sous le contrôle du facteur c-Jun N-terminal kinase (JNK), un facteur différent de celui qui contrôle l'expression de PTX3 dans les leucocytes, à savoir le facteur nucléaire kappa B (NF-κB). L'effet de différents stimuli sur la production et l’excrétion de PTX3 par les cellules du LBA a été étudié ex-vivo après mise en culture et stimulation à la poussière de foin, au lipopolysaccharide (LPS), à A. fumigatus et avec une solution saline tamponnée pour le phosphate (PBS), utilisée comme contrôle. La présence de PTX3 a été mesurée par Western Blot six heures et vingt-quatre heures après les différentes stimulations dans les cellules et dans les surnageants respectivement. PTX3 était détectée dans les cellules et dans les surnageants mais aucune différence significative d'expression n’a pu être mise en évidence que ce soit entre les différents stimuli, entre les différents temps ou avec le contrôle. Ces résultats suggèrent que la poussière de foin est un inducteur indirect de PTX3. [less ▲]

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See detailLes terres cuites architecturales des églises du haut Moyen Age dans le nord-ouest de la France et le sud-est de l'Angleterre : application de la datation par luminescence à l'archéologie du bâti
Blain, Sophie ULg

Doctoral thesis (2010)

Amongst the dating methods that can contribute to building archaeology, it is the technique of stimulated luminescence applied to ceramic building materials (CBM) that is the focus of this study. The ... [more ▼]

Amongst the dating methods that can contribute to building archaeology, it is the technique of stimulated luminescence applied to ceramic building materials (CBM) that is the focus of this study. The research reported in this thesis concerns the re-evaluation of an archaeological assumption surrounding the origin of CBM used in 9th, 10th and 11th century religious buildings of Normandy, Pays de Loire in France and Kent and Essex in England. Are the bricks used in the masonry structures Roman spolia or a novo productions? Dating techniques were scrutinized through a process of intercomparison work between two luminescence laboratories. This study highlighted the importance of knowing precise details of the sample's original environment and the need for close examination of the mineral species used in the dating process. Results from thermoluminescence (TL) and optically stimulated luminescence (OSL) dating performed on 53 CBM samples from 12 churches of north-west France and south-east England showed that the practice of reusing Roman brick was commonplace in small parish churches, but also that brick/tile-making was not a totally unknown skill of the early medieval craftsmen as has long been supposed. Most importantly, by identifying that the building material is contemporary to the church, a defined chronology emerges resulting in a new and extremely useful reference point in the history of early medieval architecture. [less ▲]

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See detailPortraits de dévots, pratiques religieuses et expérience spirituelle dans la peinture des anciens Pays-Bas (1400-1550)
Falque, Ingrid ULg

Doctoral thesis (2009)

Présent dès les premiers siècles du Moyen Âge et ce, jusqu'au XVIIe siècle au moins, le portrait de dévot (ou portrait dévotionnel) connaît à la fin du Moyen Âge un succès sans précédent et ce ... [more ▼]

Présent dès les premiers siècles du Moyen Âge et ce, jusqu'au XVIIe siècle au moins, le portrait de dévot (ou portrait dévotionnel) connaît à la fin du Moyen Âge un succès sans précédent et ce, particulièrement dans la peinture des anciens Pays-Bas. Alors qu'il était jusque-là essentiellement réservé aux princes et aux souverains, il connaît désormais une diffusion large. Nobles, bourgeois et membres du clergé désirent laisser une trace de leur piété et de leur passage sur terre. Par leur présence dans l’image, ils expriment leur dévotion, demandent la protection d'un saint et s'efforcent d'assurer leur salut dans l'au-delà. Ainsi s'expliquent la multiplication et la diversification des peintures religieuses comportant un ou plusieurs portraits de personnes agenouillées les mains jointes. D'un point de vue culturel, l'intérêt de cette production picturale réside également dans le fait que la représentation des dévots, qui lisaient et appliquaient les préceptes de la littérature dévotionnelle, peut être perçue comme une « mise en image » des pratiques religieuses et de l’expérience spirituelle telles qu’elles étaient vécues à l'époque. Composée de deux parties, la thèse envisage de manière systématique et exhaustive les modes de représentation du portrait dévotionnel dans la peinture religieuse des anciens Pays- Bas entre 1400 et 1550 et leurs significations dans le contexte spirituel de l'époque. Ce corpus d’œuvres forme un ensemble vaste et hétérogène, auquel il serait vain de vouloir appliquer une clé interprétative unique. C’est pourquoi, dans un premier temps, nous avons ouvert le champ de nos investigations de la manière la plus large possible, afin d’offrir une vue d’ensemble complète des modalités d’intégration des portraits dans la composition religieuse. Ensuite, le second temps de notre travail a requis une mise au point serrée sur une problématique précise. Il s’est alors agi d’étudier les dimensions spirituelles de ces tableaux. Préalablement à ces démarches analytiques et interprétatives, un catalogue des peintures religieuses comportant des portraits de dévots a été établi. Il comprend 663 œuvres, classées selon une typologie qui prend en compte la localisation des portraits dans la structure matérielle de l’oeuvre (sur l’avers ou le revers des volets, sur le même panneau que la scène religieuse ou dans des diptyques), le type de scène religieuse devant laquelle les portraits apparaissent (scène narrative ou scène hiératique) et la présence ou non de saints patrons. Basée sur cette typologie, la première partie de la thèse consiste en un panorama complet des différentes modalités d’intégration des portraits dans la composition religieuse. Cette étude typologique a non seulement permis de mettre en évidence la variété des formules d’intégration des dévots dans la composition, mais aussi la répartition déséquilibrée des oeuvres au sein des catégories d’analyse. Dans la seconde partie de la thèse, notre approche du portrait dévotionnel a consisté à déterminer comment les tableaux pouvaient être utilisés comme support et comme « mises en image » du processus spirituel des personnes représentées en prière. Pour ce faire, nous avons mis à profit les acquis des étapes préalables de notre travail et nous les avons enrichis en confrontant les images avec plusieurs concepts clés de la progression spirituelle tels qu’ils sont explicités dans littérature dévotionnelle et mystique contemporaine : le cheminement, l’ascension spirituelle, l’union à Dieu et la place des images dans les pratiques méditatives. Comme la thèse le montre, les implications spirituelles du portrait dévotionnel sont vastes : le tableau se présente comme un intermédiaire entre le dévot et les saints à qui il adresse ses prières. De la sorte, l’image matérialise, annonce – voire idéalise – la rencontre entre le fidèle et le Christ, entre le monde visible de l’ici-bas et le monde invisible de l’au-delà. Non seulement elle rend présents aux yeux du spectateur l’éternel et l’invisible, mais elle permet également au dévot d’entrer physiquement dans l’image, de manière à montrer picturalement la perfection spirituelle qu’il atteint. [less ▲]

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See detailEtude des propriétés hémato-supportives in vitro des cellules souches mésenchymateuses
Briquet, Alexandra ULg

Doctoral thesis (2009)

Bone marrow (BM) mesenchymal stem cells (MSC) support proliferation and differentiation of hematopoietic progenitor cells (HPC) in vitro. Since they represent a rare subset of BM cells, MSC preparations ... [more ▼]

Bone marrow (BM) mesenchymal stem cells (MSC) support proliferation and differentiation of hematopoietic progenitor cells (HPC) in vitro. Since they represent a rare subset of BM cells, MSC preparations for clinical purposes involves a preparative step of ex vivo multiplication. The aim of our study was to analyze the influence of culture duration on MSC supportive activity. MSC were expanded for up to 10 passages. MSC and CD34+ cells were seeded in cytokinefree co-cultures after which the phenotype, clonogenic capacity and in vivo repopulating activity of harvested hematopoietic cells were assessed. Early passage MSC supported HPC expansion and differentiation toward both B lymphoid and myeloid lineages. Late passage MSC did not support HPC and myeloid cell outgrowth but maintained B cell supportive ability. In vitro maintenance of NOD/SCID mouse repopulating cells cultured for one week in contact with MSC was effective until the fourth MSC passage and declined afterwards. CD34+ cells achieved higher levels of engraftment in NOD/SCID mice when co-injected with early passage MSC; however MSC expanded beyond 9 passages were ineffective in promoting CD34+ cell engraftment. Non-contact cultures indicated that MSC supportive activity involved diffusible factors. Among these, interleukin (IL)-6 and IL-8 contributed to the supportive activity of early passage MSC but not of late passage MSC. MSC phenotype as well as fat, bone and cartilage differentiation capacity did not change during MSC culture. Extended MSC culture alters their supportive ability toward HPC without concomitant changes in phenotype and differentiation capacity. [less ▲]

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See detailVariation linguistique et signification sociale chez les jeunes Bruxelloises issus de l’immigration maghrébine. Analyse socio-phonétique de trois variantes non standard.
Audrit, Stéphanie ULg

Doctoral thesis (2009)

The present PhD research concerns three non-standard phonetic variants, known as specific to the adolescents from Moroccan immigration, and the meso-social meanings linked to these variants. The meso ... [more ▼]

The present PhD research concerns three non-standard phonetic variants, known as specific to the adolescents from Moroccan immigration, and the meso-social meanings linked to these variants. The meso-social level is defined here as the profiles or social personae (Coupland 2001). My hypothesis is that macro-socially homogeneous speakers use non standard variants according to their belonging to contrasted meso-social profiles. This problem is tackled through the analysis of authentic data, collected during a one-year ethnographic survey inside of two Brussels schools. These schools had a mostly female and immigrated population. Among the two of them, a peer group constituting a community of practice (Eckert 2000, 2005) was chosen as the focus of the study. This ethnographic gathering of data has a double aim: (i) first, it has to allow to determine what the profiles specific to the investigated peer groups are; (ii) secondly, a long-term survey must allow to collect speech as close as possible of the speakers’ vernacular. The three non standard variants are the followings: (i) The reduced vowels: they are strongly reduced vowels that can completely disappear from the sound signal, in very atypical positions according to standard French. (ii) The back /A/: these realisations of /A/ are characterized by the backing of their articulation point, whose consequence is to move their timbre closer to this of /ɔ/ ; (iii) The marked variants of /r/: this large designation includes trill fricatives and fricatives produced with a large amount of noise. Analyzing the meso-social meaning of non standard variants requires a double methodology, both qualitative and quantitative. The qualitative part concerns the analysis of ethnographic data (interviews and fieldwork notes). It leads to the discovery of three contrasted speaker profiles, that is to say the messing-up girls, the provocatives and the modests. In the second part of the analysis, the existence of a link between the different speaker profiles and the use of each of the marked variants was investigated through statistical independence tests (chi square tests). These tests underline that the reduced vowels and the marked variants of /r/ are more used by the messing-up and the provocative girls, that is to say to speaker profiles which distance the traditional Moroccan and Muslim values. At the opposite, the back /A/ seem to have a double face, because they are linked with two very different profiles, the provocatives and the modests. This variant is also often mentioned as characteristic of the lower class language (Jamin 2005). It seems thus that the back /A/ have multiple meanings, whose point in common would be pejoration. If we come back to the initial hypothesis, the use of marked variants thus appears to be linked to the speakers’ belonging to contrasted profiles. However, these profiles are not the only factor to have an influence: the results of the tests show that, jointly to the profiles, the school has also an influence on the use of marked variants. This importance of school was furthermore underlined by several researches in sociology of education, where it is known as the school composition effect (Dumay & Dupriez 2005, 2008). [less ▲]

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See detailMicrobial diversity and activity in temperate forest and grassland ecosystems
Malchair, Sandrine ULg

Doctoral thesis (2009)

Ecosystems currently face widespread biodiversity losses and other environmental disturbances, such as climate warming, related to increased anthropogenic activities. Within this context, scientists ... [more ▼]

Ecosystems currently face widespread biodiversity losses and other environmental disturbances, such as climate warming, related to increased anthropogenic activities. Within this context, scientists consider the effects of such changes on the biodiversity, and hence on the activity, of soil microorganisms. Indeed, soil microorganisms mediate a wide range of soil processes. Currently, knowledge on soil microbial diversity is still limited, partially due to technical limitations. The advent of molecular-based analyses now allows studying the soil microbial diversity. These advances in the study of soil microbial communities have lead to a growing evidence of the critical role played by the microbial community in ecosystem functioning. This relationship is supposed to be relevant for narrow processes, regulated by a restricted group of microorganisms, such as the nitrification process. This PhD thesis aimed at studying ammonia oxidizing bacteria (AOB) community structure and richness as an integrated part of soil functioning. This research aimed at investigating the effect of aboveground plant diversity on ammonia oxidizing bacteria diversity and function in forest and grassland soils with focus on the influence of (a) functional group identity of grassland plants (legumes, grasses, forbs), (b) grassland plant species richness and (c) tree species, on AOB diversity and function. Another objective of this research was to study the effect of a 3°C increase in air temperature on AOB diversity and function. The link between AOB diversity and function (potential nitrification) is also investigated. For grassland ecosystems, a microcosm experiment was realized. An experimental platform containing 288 assembled grassland communities was established in Wilrijk (Belgium). Grassland species were grown in 12 sunlit, climate controlled chambers. Each chamber contained 24 communities of variable species richness (S) (9 S=1, 9 S=3 and 6 S=9).The grassland species belonged to three functional groups: three species of each grasses (Dactylis glomerata L., Festuca arundinacea SCHREB., Lolium perenne L.), forbs (non-N-fixing dicots; Bellis perennis L., Rumex acetosa L., Plantagolanceolata L.), and legumes (N-fixing dicots; Trifolium repens L., Medicago sativa L., Lotus corniculatus L.). Half of these chambers were exposed to ambient temperature and the other half were exposed to (ambient +3°C) temperature. One ambient and one (ambient+3°C) chambers were destructively harvested 4, 16 and 28 months after the start of the experiment. The influence of plant functional group identity on the nitrification process and on AOB community structure and richness (AOB diversity) was assessed in soils collected from the first two destructive amplings (chapter 2). The effect of plant species richness on AOB diversity and function was considered for soils sampled after 16 and 28 months (chapter 3). AOB function was determined by potential nitrification. AOB community structure and richness were assessed by polymerase chain reaction followed by denaturing gradient gel electrophoresis (DGGE) and sequencing of excised DGGE bands. I found that functional group identity can affect AOB community structure. In particular, the presence of legumes, both in monoculture or in mixture with forbs and grasses, lead to AOB community composition changes towards AOB clusters tolerating higher ammonium concentrations. This change in AOB community structure was only linked to increased potential nitrification under monocultures of legumes, when ammonium was supposed to be not limiting. This study revealed that physiological attributes of AOB and resource availability may be important factors in controlling the nitrification process. This research showed that the impact of plant species richness on the nitrification process could be mediated by the interactions between plants and AOB, through competition for substrate. A 3°C increase in air temperature did not affect AOB community structure, richness or function. In forest ecosystems, we studied the effect of tree species in forest sites located in Belgian and in the Grand-Duchy of Luxembourg covered each by several deciduous or coniferous tree species (Fagus sylvatica L., Quercus petraea (Mattuschka) Lieblein, Picea abies (L.) Karst, Pseudotsuga menziesii (Mirbel) Franco). We investigated the influence of these tree species on microbial processes (chapter 5) related to C and N cycling, particularly with emphasize on the nitrification process and on the diversity of AOB (chapter 6). The results showed that the effect of tree species on net N mineralization was likely to be mediated through their effect on soil microbial biomass, reflecting their influence on organic matter content and carbon availability. Influence of tree species on nitrification (potential and relative) might be related to the presence of ground vegetation through its influence on soil ammonium and labile C availability. AOB community structure was more site-specific than tree specific. However, within sites, AOB community structure under broadleaved trees differed from the one under coniferous trees. The effect on tree species on AOB was likely to be driven by the influence of tree species on net N mineralization, which regulates the substrate availability for AOB. The results also demonstrated that the relationship between AOB diversity and function might be related both to AOB abundance and AOB community structure and richness. This thesis showed no clear relationship between AOB community structure or richness and AOB function. However, we revealed that aboveground grassland plant richness, grassland plant functional groups and tree species influence AOB community structure and richness. [less ▲]

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See detailEvolution des traditions culturelles dans la vallée du moyen Euphrate de la fin du Bronze ancien au début du Bronze moyen
Colonna d'Istria, Laurent ULg

Doctoral thesis (2009)

The valley of the Middle Euphrates, hyphen between South Mesopotamia and Western Syria, was ruled by a šakkanakku lived in Mari (Tell Hariri, Syria) during the end of the third millennium and early second ... [more ▼]

The valley of the Middle Euphrates, hyphen between South Mesopotamia and Western Syria, was ruled by a šakkanakku lived in Mari (Tell Hariri, Syria) during the end of the third millennium and early second millennium. This time period named "šakkanakku-period" is particularly studied since twenty years An overview of archaeological and historical data from the Middle Euphrates valley during the time of šakkanakku suggest that the kingdom of Mari during that time has established itself as a power independent and prosperous until the 19th century (end of the time of šakkanakku) where data are less explicit historically. The new text data from Mari, and Terqa (north of Mari), of the most dated from the end of šakkanakku-period, shows continuance and ruptures between the end of šakkanakku-period and the next period ("Amorite-period"). This continuance and ruptures are examined in several areas such as language, "scribal tradition" or in the legal tradition. The dialect of this text (19th century) shows that linguistic tradition is deeply rooted in the universe Syria. After the advent of the Amorite Yahdun-Lim who ended the time of the šakkanakku the Syrian characteristics in the dialect remains present, but it is less important because a reform of writing modeled on southern Mesopotamia (Iraq current), probably due to the preponderance of political Ešnunna during the end of the 19th century. Finally, this new text has also allowed dealing the historical interaction of the last šakkanakku Mari with condottieri Amorite whose father Yahdun-Lim in the 19th century. [less ▲]

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See detailCaractère reconnaissable d'ensembles de polynômes à coefficients dans un corps fini
Waxweiler, Laurent ULg

Doctoral thesis (2009)

Nous nous plaçons dans le cadre de l'anneau des polynômes sur un corps fini. Si P est un polynôme de degré au moins 1, tout polynôme Q se décompose de manière unique sous la forme d'une combinaison ... [more ▼]

Nous nous plaçons dans le cadre de l'anneau des polynômes sur un corps fini. Si P est un polynôme de degré au moins 1, tout polynôme Q se décompose de manière unique sous la forme d'une combinaison linéaire de puissances de P, dont les coefficients sont des polynômes dont le degré est strictement inférieur à celui de P. À une telle décomposition, nous associons un mot que nous appelons la P-représentation du polynôme Q. Un ensemble de polynômes est alors qualifié de P-reconnaissable si il existe un automate fini déterministe qui accepte l'ensemble des P-représentations de ses éléments. Dans cette thèse, nous montrons que les ensembles P-reconnaissables sont exactement ceux qui sont définissables par une formule du premier ordre dans une certaine structure S(P) basée sur un prédicat dépendant du polynôme P. Nous donnons aussi une caractérisation des ensembles P-reconnaissables en terme de suites P-automatiques. Nous apportons également une réponse partielle à la question de savoir quels sont les ensembles reconnaissables simultanément dans toutes les bases de degré au moins 1. Finalement, nous montrons que si P et Q sont deux polynômes de degré au moins 1 et multiplicativement indépendants, alors la multiplication est définissable dans la réunion des structures S(P) et S(Q). [less ▲]

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See detailGravitationally lensed quasars: light curves, observational constraints, modeling and the Hubble constant.
Chantry, Virginie ULg

Doctoral thesis (2009)

The central topic of this thesis is gravitational lensing, a phenomenon that occurs when light rays from a background source pass near a massive object located on the line of sight and are deflected. It ... [more ▼]

The central topic of this thesis is gravitational lensing, a phenomenon that occurs when light rays from a background source pass near a massive object located on the line of sight and are deflected. It is one of the most wonderful observational fact in favour of the General Theory of Relativity (Einstein, 1916). This phenomenon constitutes a powerful tool to probe different areas in astrophysics, including cosmology, which is our main interest. In particular we study gravitationally lensed quasars. Refsdal (1964) was the first to state that time delays between different lensed images of the same object, if this one is intrisically variable, can lead to the measurement of the Hubble constant H0, which is related the actual expansion rate of the Universe. Up to now, only a few lensed quasars have led to H0 and the precision on it has never reached the one obtained with other methods as the ones based on the Cosmic Distance Ladder. That is why some scientists from around the globe decided to unite their force to measure H0 from about thirty lensed quasars. To reach that goal, these objects are being monitored with some mid-sized ground-based telescopes located in both hemispheres. This thesis is realised in the framework of this collaboration called COSMOGRAIL for COSmological MOnitoring of GRAvItational Lenses. This work focuses on image processing and on several steps mandatory to obtain a measurement of H0 from lensed quasars: the acquisiton of the light curves from which it is possible to extract the time delays and the acquisition of the observational constraints necessary to model the gravitational potential responsible for the observed configura- tion. The central technique of this work is the image deconvolution with the MCS algorithm (Magain, Courbin & Sohy, 1998). The main principle of this algorithm is the non-violation of the sampling theorem in trying to obtain a better resolution in the deconvolved frame instead of an infinite one. The final resolution in the deconvolved frame is chosen by the user and as it is known, every image is decomposed in a contri- bution from the point sources and another one from all the extended structures such as arcs, rings and galaxies. To obtain good light curves from data coming from several telescopes, good reduction procedures are needed. That is why Vuissoz (2008) developed a semi-automated reduc- tion pipeline including deconvolution with the MCS algorithm. In the framework of the i ii Abstract present thesis, we adapt it to one of the telescopes used by the collaboration whose data were never used before, i.e. the Mercator telescope. We also bring some modifications to this pipeline, e.g. concerning the estimation of the error on the magnitudes of the light curves. We apply this revised version of the reduction pipeline to HE 0435-1223, a quadruply imaged quasar with already measured time delays (Kochanek et al., 2006). Another object, the quad WFI J2026-4536, is then investigated: we obtain light curves for each of the four lensed images. Thanks to the CASTLES project (Cfa-Arizona Space Telescope LEns Survey1), many lensed quasars have been observed with the camera 2 of NICMOS (Near Infrared Camera and Multi-Object Spectrometer ) on board the Hubble Space Telescope. With these high resolution images, we can obtain very accurate constraints on the geometry of the lensed systems. But most of the time no star is available in the field of view to obtain a good Point Spread Function (PSF). That is why we develop an iterative strategy combined with the MCS algorithm: we call it ISMCS. This technique allows to use the lensed images themselves to improve the PSFs step by step while simultaneously deconvolving the frame to obtain better estimations of the extended structures in the image. We first test this strategy on a quadruply imaged quasar, the Cloverleaf gravitational lens (H1413+117), and obtain relative positions precise to 1 milliarcsecond (mas). We then apply ISMCS to the quadruply imaged quasar WFI J2033-4723 in order to con- tribute to the estimate of the Hubble constant, as this object was monitored by our team. We then study a sample of seven lensed systems currently monitored by COSMOGRAIL and for which time delays have never been obtained. Here again, we obtain positional constraints with an accuracy of around 1 to 2 mas thanks to the application of ISMCS. We then model these systems with simple mass profiles for the main lens galaxy and obtain an estimation of the values of the time delays. Finally we apply ISMCS to a sample of eleven lensed quasars which already have measured time delays. When the delays have been remeasured by our team, in four cases until now, we also model the potential of the lens with simple mass profiles to estimate H0. 1http://www.cfa.harvard.edu/castles [less ▲]

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See detailAbstract Numeration Systems : Recognizability, Decidability, Multidimensional S-Automatic Words, and Real Numbers
Charlier, Emilie ULg

Doctoral thesis (2009)

In this dissertation we study and we solve several questions regarding abstract numeration systems. Each particular problem is the focus of a chapter. The first problem concerns the study of the ... [more ▼]

In this dissertation we study and we solve several questions regarding abstract numeration systems. Each particular problem is the focus of a chapter. The first problem concerns the study of the preservation of recognizability under multiplication by a constant in abstract numeration systems built on polynomial regular languages. The second is a decidability problem, which has been already studied notably by J. Honkala and A. Muchnik and which is studied here for two new cases: the linear positional numeration systems and the abstract numeration systems. Next, we focus on the extension to the multidimensional setting of a result of A. Maes and M. Rigo regarding S-automatic infinite words. Finally, we propose a formalism to represent real numbers in the general framework of abstract numeration systems built on languages that are not necessarily regular. We end by a list of open questions in the continuation of the present work. [less ▲]

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See detailInter- and intraday variability of Flemish travel behavior
Cools, Mario ULg

Doctoral thesis (2009)

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See detailSpecies response to the fragmentation and restoration of wet heathlands and associated habitats in High Ardenne (Belgium) – A multi-taxonomic approach
Cristofoli, Sara ULg

Doctoral thesis (2009)

The impact of habitat fragmentation and the success of habitat restoration were studied through a multi-taxonomic approach. The response to landscape structure and/or habitat quality of three taxonomic ... [more ▼]

The impact of habitat fragmentation and the success of habitat restoration were studied through a multi-taxonomic approach. The response to landscape structure and/or habitat quality of three taxonomic groups was explored, in (semi-)natural habitats. The three taxonomic groups were complementary, both in terms of their specific life history traits and their place in the food chain. We considered autotrophic species (vascular plants), herbivores (butterflies) and predators (spiders). Life-history traits and species specialization for target habitat were used to refine the analysis. Target habitat was a complex of wet heathlands, poor fens and bogs. Patches of this complex of habitats were sampled on two high plateaus in the Belgian Ardenne, the Plateau de Saint-Hubert and the Plateau des Tailles. Over the last 250 years, two jointly acting habitat dynamics were observed in these areas: a loss of area (and connectivity) on the one hand but also the creation of new habitat patches. It is precisely this double dynamics that enabled us to analyze and develop concepts linked to the response of species faced with spatio-temporal modifications of their habitat. Specifically, in this work we focused on the comprehension of two unbalanced situations, affecting the relationships between species richness and patch characteristics. A first unbalanced situation, the extinction debt, was observed for vascular plant communities. On the opposite, a colonization credit, the second unbalanced situation, was noted for butterflies and seemed to mainly affect specialist species. Specialist species of the three taxonomic groups showed relatively contrasted responses compared to generalist species. However, the life-history traits we studied only slightly influenced the response of species at the community level, excepted for pioneer communities in habitat patches less than 5 years old. [less ▲]

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See detailMorphology and dynamics of the Io UV footprint
Bonfond, Bertrand ULg

Doctoral thesis (2009)

The Io UV footprint (IFP) is one of the most spectacular signatures of the Io-Jupiter interaction. It consists of several auroral spots and an extended tail which are located close to the feet of the ... [more ▼]

The Io UV footprint (IFP) is one of the most spectacular signatures of the Io-Jupiter interaction. It consists of several auroral spots and an extended tail which are located close to the feet of the magnetic field lines passing through Io in each hemisphere. The purpose of the present study is to demonstrate that a careful analysis of the Io UV footprint based on observations acquired with the STIS and ACS high resolution and high sensitivity FUV cameras on board the Hubble Space Telescope can provide us with essential information on the ongoing physical processes. The thesis is organized around basic questions: “What is the Io footprint?”, “Where is the Io footprint?”, “How high is the Io footprint?”, “How big is the Io footprint?” and finally: “How bright is the Io footprint?” The answers to these questions have profound implications for the understanding of the phenomenon. Among the most important results of this work is the unexpected finding of a faint auroral spot appearing upstream of the main Io spot in one hemisphere while only downstream spots are seen in the opposite hemisphere. The detailed study of the evolution of the inter-spot distances puts previous models describing the footprint morphology under question. We propose a new interpretation which involves that some spots are caused by electrons accelerated away from the planet along the field lines in one hemisphere, crossing the equatorial plane in the form of electron beams and precipitating in the opposite hemisphere, creating the so-called Trans-hemispheric Electron Beam (TEB) spots. The information provided by the position of the satellite footprints is not restricted to the interaction between the moon and the Jovian magnetosphere. The analysis of the footpaths of Io, Europa and Ganymede helped us to further constrain the magnetic field models, notably through the identification of a large magnetic anomaly in the northern hemisphere. Additionally, the study of the speed of the Io footprint along its reference contour suggests that a second anomaly regions may also exist in the North. In this work, we present a new and direct method to measure the altitude of the different footprint features. The main spot and the tail emissions have a peak altitude of 900 km while the peak altitude of the Trans-hemispheric Electron Beam spot is 700 km. These results suggest that the main spot and tail emissions are caused by the precipitation of electrons with a mean energy around 1 keV, far lower than the 55 keV value previously derived from spectral measurements. The vertical extent of these emissions is surprisingly broad (scale height ~400 km) and is best fitted with an incoming kappa electron energy distribution (spectral index ~2.3). This suggests that the electron acceleration is supplied by processes related to inertial Alfvén waves rather than by quasi-static potentials as proposed by some theoretical models. The size of the main footprint spot is carefully estimated on a much larger image sample than before: its length along the footpath is ~900 km while its width perpendicular to the footpath is <200 km. Larger lengths are sometimes observed but in that case, they are attributed to the mix of individual spots. The spot length is larger than the projected diameter of Io around the magnetic field lines but is consistent with recent simulations. As far as the Io footprint brightness is concerned, variations on two timescales have been studied. On timescales of minutes, systematic brightness fluctuation on the order of 30% (and going up to 50%) are observed. Additionally, cases of simultaneous variations of the main and the TEB spots are reported, which suggests that the process that triggers these fast variations is located close to the planet. Variations of the main spot brightness with the System III longitude of Io are also analyzed. Our new measurement method fully considering the multi-spot structure of the IFP and the real geometry of the observations provides more accurate estimates for the precipitating energy flux (between 100 and 500 mW/m for the main spot). The main spot brightness peaks at 110° and 290° longitude, which could be attributed either to an enhanced interaction strength when Io is near the dense torus center or to spots merging which is also observed to occur in these sector. Nevertheless, strong North-South asymmetries are also observed, which suggests that the surface magnetic field strength also influences the spots brightness. [less ▲]

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See detailPerturbations de la phosphorylation oxydative : réponses protéomiques et conséquences métaboliques
Mathy, Grégory ULg

Doctoral thesis (2009)

La phosphorylation oxydative et ses partenaires privilégiés, que sont les voies métaboliques énergétiques principales, sont finement régulés au niveau thermodynamique en vertu de la loi d’action des ... [more ▼]

La phosphorylation oxydative et ses partenaires privilégiés, que sont les voies métaboliques énergétiques principales, sont finement régulés au niveau thermodynamique en vertu de la loi d’action des masses. Ces processus de régulations enzymatiques s’accompagnent cependant de « soupapes » de sécurité qui permettent, le cas échéant, de maintenir de manière optimale la bonne opération de l’ensemble de ce système et donc d’assurer une balance metabolique adequate entre l’offre et la demande. Par une approche de protéomique comparée, nous avons étudiés les effets de ces différents types de stress tant au niveau mitochondrial que cellulaire afin de mettre en évidence d’éventuelles adaptations initiées par la cellule en réponse à ces perturbations Dans la première partie nous avons etudie les effets de l’oxydase alternative sur le protéome mitochondrial et cellulaire. La première etude consiste en une création de la fonction AOX au niveau mitochondrial dans un organisme modèle ne l’exprimant pas naturellement : Saccharomyces cerevisiae. Deux approches protéomiques ont été utilisees, à savoir le 2D DIGE et le SILAC. La seconde étude concernant AOX consiste en l’analyse des effets d’une perte de fonction de la protéine obtenue par ARN interférence chez l’algue unicellulaire Chlamydomonas reinhardtii. La seconde partie de notre travail sera consacrée à l’étude des modifications protéomiques accompagnant l’initiation de la thermogenèse non frissonnante ainsi que l’acclimatation au froid au niveau du tissu adipeux brun. Cette étude à été réalisée chez le rat et chez la souris. Les effets de l’acclimatation au froid chez des souris UCP-1 KO ont ete aussi étudiés et comparés aux effets chez des souris normales. [less ▲]

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See detailFilms minces mesoporeux d’oxydes mixtes de vanadium et de niobium comme électrode positive pour accumulateurs au lithium
Krins, Natacha ULg

Doctoral thesis (2009)

Mesoporous thin films are promising architectures for positive electrodes in Li-ion battery applications. A particular challenge in this field has been successful templating of vanadium-based oxides ... [more ▼]

Mesoporous thin films are promising architectures for positive electrodes in Li-ion battery applications. A particular challenge in this field has been successful templating of vanadium-based oxides, materials known for their ability to host lithium, since their thermal instability and complex vanadium chemistry hinder templating through traditional soft-chemistry approaches. To address these technical problems we develop the soft-templating of vanadium and niobium mixed oxides based on Evaporation Induced Micelles Packing using thermally stable polystyrene-b-polyethyleneoxide structuring agents. In-situ thermal monitoring via ellipsometry allows successful navigation of the thermal stability landscape. TEM and AFM analyses reveal homogeneous wormlike mesoporous structures whose pore and inorganic wall sizes can be tuned from 15 to 100 nm by changing the hydrophobic/hydrophilic surfactant chain lengths. Ellipsometric porosimetry shows that 100 nm thick films with a 15 nm pore size displays 30% electrolyte accessible porosity. The interconnected tridimensional mesoporous network has been highlighted by electronic tomography. Thicker films up to 1.3 µm are prepared by a multidipping process. The superiority of such nanoarchitectures compared to non porous materials in terms of electrochemical properties such as capacity are revealed using cyclic voltammetry. [less ▲]

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See detailDéveloppement d'une méthodologie pour l’appréciation quantitative des risques appliquée à Salmonella dans la viande de porc en Belgique
Delhalle, Laurent ULg

Doctoral thesis (2009)

Following the European legislation on control of Salmonella and other zoonotic agents, effective measures must be taken to detect and control these agents at all stages of the food chain. Therefore, the ... [more ▼]

Following the European legislation on control of Salmonella and other zoonotic agents, effective measures must be taken to detect and control these agents at all stages of the food chain. Therefore, the Belgian FPS Public Health, Food Chain Safety and Environment has decided to fund a research project involving institutions grouped under a consortium in order to develop a Quantitative Microbial Risk Assessment (QMRA) on human salmonellosis following consumption of minced pork meat. To achieve this goal, preliminary steps were necessary. The first task was a survey on available data at all stages of the production chain from public authorities and food business operators. A database was carried out summarizing the working practices in different companies and the microbiological results of the whole production chain. The aim was to study the sources of contamination of pork meat from the slaughterhouse to the preparation at consumer's home. Thanks to collected data, a QMRA model has been built taking into account the production flow. The objective of the model is to provide options to reduce the risk of human salmonellosis due to consumption of minced pork meat. The scenarios were developed on the international situation and the literature to simulate concrete and realistic opportunities to improve the microbiological quality of pork meat. The potential risk factors of contamination associated with production parameters, technical facilities and methods for cleaning/disinfection were evaluated in the 10 largest Belgian slaughterhouses. The results showed high variability concerning Salmonella contamination among these slaughterhouses, with prevalence ranging from 2.6 to 34.3%. The results of linear and logistic regressions revealed that some working practices such as scalding steam, second flaming after polishing and cleaning/disinfection of the splitter machine several times a day are beneficial to reduce contamination by Salmonella. These data were the basis for modelling the slaughter process of pigs in Belgium. Production stages after the slaughterhouse were also studied. The results of bacteriological analysis of seven cutting plants, four minced meat plants of the four largest retailers in Belgium were collected using data from official and self-monitoring. The Salmonella prevalence in cutting meat varies from 0% to 50%. The prevalence of Salmonella in minced meat at the retail level varies from 0.3% to 4.3%. Salmonella concentrations on the carcasses, the meat and minced meat were estimated from semi-quantitative data and were equal to -3.40 ± 2.04 log CFU/cm ², -2.64 ± 1.76 log CFU/g and -2.35 ± 1.09 log CFU/g, respectively. These data provided the basis to build the model for the cutting, mincing, distribution and storages stages of pork meat chain in Belgium. A QMRA model was then developed on the basis of collected data. After validation, scenarios of risk mitigation have been implemented. The number of human salmonellosis due to consumption of minced pork meat in Belgium was estimated at 15,376 cases per year. The results showed that the risk of human salmonellosis could be reduced significantly with efforts made by food business operators, but also by consumers. Following the model, 25% reduction of carcass prevalence at the slaughterhouse would decrease from 45.7% the number of human salmonellosis cases in Belgium. Consumers should also be aware of good hygiene practices during preparation of the meat in household’s kitchen to avoid cross contamination between foods. Following the model, cross-contamination with raw foods during the preparation of meals generates 14,693 cases of salmonellosis each year and the lack of cooking only 683 cases. The number of cases of human salmonellosis could be reduced by improving the food preparation habits in the kitchen to avoid cross contamination. The results of this research are useful for food business operators and public health officials involved in the production of pork. The QMRA presented in this thesis were used to obtain an overview of the Belgian food chain andalso to make recommendations along the production chain. However, these results must be taken with care because, at present time, the application of QMRA in the meat industry has a recurring problem of lack of data. States and companies should undertake studies and provide a better assessment of the situation of the food chain "from farm to fork". [less ▲]

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See detailContribution au traitement de l’incontinence urinaire chez la chienne par soutènement urétral prothétique trans-obturateur
Claeys, Stéphanie ULg

Doctoral thesis (2009)

L’incompétence du sphincter urétral (ISU) est la cause la plus fréquente d’incontinence urinaire chez la chienne adulte. Elle affecte typiquement les chiennes stérilisées, d’âge moyen et de grande race ... [more ▼]

L’incompétence du sphincter urétral (ISU) est la cause la plus fréquente d’incontinence urinaire chez la chienne adulte. Elle affecte typiquement les chiennes stérilisées, d’âge moyen et de grande race. Son traitement est initialement médical. La phénylpropanolamine (PPA) est le traitement médical de choix et son taux de succès varie de 85 à 97 % de continence. Des études expérimentales antérieures ont démontré l’avantage urodynamique d’une administration de PPA une fois par jour par rapport à l’administration 3 fois par jour recommandée habituellement. Aucune étude clinique n’a cependant été réalisée jusqu’à présent pour confirmer l’efficacité de ce protocole de traitement chez la chienne incontinente. Un traitement chirurgical est recommandé en cas de non réponse ou de réponse partielle au traitement médical, si la chienne devient réfractaire au traitement ou développe des effets secondaires, ou si les propriétaires ne souhaitent pas administrer un médicament à long terme. De nombreuses techniques chirurgicales ont été décrites pour traiter l’ISU chez la chienne mais aucune à l’heure actuelle ne permet de garantir un taux de continence complète élevé et ce, à long terme et avec un faible taux de complications. Le traitement de l’incontinence urinaire d’effort chez la femme est principalement chirurgical et implique le placement d’une bandelette sous-urétrale par voie vaginale. Parmi les techniques décrites, la TVT-O offre un très bon taux de succès et présente très peu de complications postopératoires. Les objectifs de ce travail étaient donc d’évaluer l’efficacité clinique d’un dosage quotidien unique de PPA et d’adapter la technique TVT-O à la chienne en passant par une étude préliminaire sur cadavres et chiennes Beagles saines pour ensuite l’utiliser chez des chiennes incontinentes atteintes d’ISU, afin d’en évaluer les effets cliniques, urodynamiques et morphologiques. Dans la première étude, l’efficacité clinique de la PPA administrée une seule fois par jour à un dosage de 1.5 mg/kg a été démontrée. En effet, le suivi à long terme (23.9 mois en moyenne) montre que 8 chiennes sur 9 étaient continentes après traitement. Une chienne n’a pas répondu à la PPA et a été traitée chirurgicalement. Aucun effet secondaire n’a été observé chez les animaux traités. D’un point de vue urodynamique, l’administration de PPA augmente significativement les valeurs de pression urétrale maximale de fermeture (MUCP). L’administration de PPA 2 à 3 fois par jour, telle que recommandée habituellement, n’est donc pas utile puisqu’une administration quotidienne unique, plus pratique et moins coûteuse pour les propriétaires, suffit à maintenir la continence chez 89 % des chiennes traitées. La faisabilité de la technique TVT-O a ensuite été évaluée chez la chienne. La dissection de 12 cadavres de chiennes après mise en place de la bandelette montre que la TVT-O est faisable chez la chienne moyennant certaines adaptations. Une épisiotomie est notamment nécessaire chez la chienne contrairement à la femme. Les résultats montrent que la bandelette est située à une distance raisonnable des structures neuro-vasculaires importantes, y compris les vaisseaux fémoraux et le nerf obturateur, minimisant le risque de les léser. Elle est également localisée de manière constante en arrière du muscle élévateur de l’anus, en région périnéale, rendant ainsi le risque de lésion vésicale quasi inexistant. La technique apparaît donc peu risquée et reproductible chez la chienne. L’application de la TVT-O chez 2 chiennes Beagles continentes nous a ensuite permis d’observer l’absence de complications intra- et postopératoires. D’un point de vue urodynamique, la pression intégrée (aire sous la courbe d’UPP représentant la résistance urétrale) est augmentée jusqu’à 4 mois après l’intervention. Les vagino-urétrographies postopératoires montrent un déplacement ventral et un rétrécissement de l’urètre distal juste en avant du méat urinaire. D’un point de vue histologique, les tissus entourant la bandelette montrent une réaction fibroblastique modérée accompagnée d’une réaction inflammatoire lympho-plasmocytaire légère à modérée. La bandelette semble donc relativement inerte et bien tolérée chez le chien. La tolérance de la bandelette est d’une importance majeure puisqu’une réaction inflammatoire excessive peut induire une érosion vaginale ou urétrale pouvant entraîner une infection. La TVT-O a ensuite été réalisée sur 8 chiennes incontinentes atteintes d’ISU. Après un suivi de 2 semaines à 12 mois (moyenne, 7.3 mois), 7 des 8 chiennes sont continentes. Une chienne a récidivé 2 mois après la chirurgie et a été traitée à la PPA. D’un point de vue urodynamique, MUCP et la pression intégrée sont augmentées significativement après l’intervention. L’augmentation de pression se situe principalement au niveau de l’urètre moyen. Il apparaît donc que la localisation du pic de pression urétrale postopératoire ne correspond pas à la localisation anatomique de la bandelette. Les vagino-urétrographies, pour la plupart non remarquables, montrent que la bandelette ne modifie pas la position du col vésical puisque les vessies en position pelvienne en préopératoire le restent en postopératoire. Une complication intra-opératoire s’est produite chez une chienne chez qui une lésion urétrale caudale a été créée pendant l’intervention. Aucune complication postopératoire n’a été observée. Les résultats cliniques à court et moyen terme de l’utilisation de la TVT-O dans le traitement de l’ISU chez la chienne sont donc très favorables. L’hypothèse d’un rétablissement d’un support urétral déficient, entraînant une restauration de la fonction urétrale, reste à démontrer. [less ▲]

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See detailOptimisation des paramètres du procédé de thixoforgeage des alliages d'aluminium 7075 à haute fraction solide
Vaneetveld, Grégory ULg

Doctoral thesis (2009)

Wrought 7075 aluminium alloy functional parts with complex geometry are mostly shaped by machining. For a mass production, the machining cost can be reduced by shaping a draft by forging. It is more ... [more ▼]

Wrought 7075 aluminium alloy functional parts with complex geometry are mostly shaped by machining. For a mass production, the machining cost can be reduced by shaping a draft by forging. It is more interesting to produce a near-net-shape draft to reduce machining. To shape a complex geometry part in one step, the viscosity of the material has to be sufficiently low. This low viscosity requires the generation of a liquid phase in the material but this phase introduces defects in the wrought alloy such as hot cracking, porosity, shrinkage porosity, large shrinkage, macrosegregation solid-liquid. These defects can be reduced by limiting the liquid fraction to 0.1 and thus using thixoforging process. 7075 alloy is particularly sensitive to hot cracking, a low shrinkage is a benefit. Recristallisation process is choosen to obtain a semi-solid globular material. This process uses recrystallisation to transform extruded material into a material that shows a shear thinning-thixotropic behaviour. Heating and extrusion tests help to study the influence of various process parameters on the forming load and the quality of thixoforged parts. We will adjust the parameters of heating and forming on a tool specially designed to thixoforge parts from simple to complex geometry. A study of the influence of parameters on the mechanical properties and the quality of the parts showed very good potential for the thixoforging of 7075 alloy. [less ▲]

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See detailQuantification de la robustesse du procédé de thixoformage des aciers
Pierret, Jean-Christophe ULg

Doctoral thesis (2009)

This work aims to assess the robustness of the steel thixoforming process by a qualitative and quantitative study of the influence of the parameters involved in the process. Thixoforming is the shaping of ... [more ▼]

This work aims to assess the robustness of the steel thixoforming process by a qualitative and quantitative study of the influence of the parameters involved in the process. Thixoforming is the shaping of metals in the semi-solid state and with a globular microstructure. In this case, one shows that consistency decreases when shear rate increases and that the process parameters leading the behaviour are time dependent. As a key-step of the technology, heating is studied as well as forming. Influences of heating strategy, inductor’s geometry and external conditions are determined by the help of modelling and heating experiments. Handling system between heating furnace and press is also tackled. To study the forming’s relability and sensitivity, three geometries are used : direct extrusion, a rheological study part and an industrial part. Again, practical experiments and modelling are used in a complementary way. Effects of slug’s temperature, forming speed, lubrication and tool’s temperature are analysed. Repeatability of heating and forming are highlighted. The defects and structures obtained in the parts are presented before discussing the thixoformability of steel grades. In particular, qualification of especially designed grades as well as non adapted grades is discussed. Finally, the tooling wear and lifetime issues are detailed as it is one of the mean locks of the technology industrialisation. [less ▲]

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See detailContribution à l'étude de l'Imagerie par Résonance Magnétique du pied équin: effets sur l'image de la conservation des membres isolés, du champ magnétique, des séquences et des plans de coupe
Bolen, Géraldine ULg

Doctoral thesis (2009)

RESUME Description du sujet de recherche abordé: Le pied du cheval est composé de nombreuses structures anatomiques renfermées dans une boîte cornée rendant l’investigation de celles-ci plus compliquée ... [more ▼]

RESUME Description du sujet de recherche abordé: Le pied du cheval est composé de nombreuses structures anatomiques renfermées dans une boîte cornée rendant l’investigation de celles-ci plus compliquée (Dyson, 2003). Les méthodes d’imagerie classiquement utilisées en médecine équine telle la radiographie et l’échographie montrent de nombreuses limites dans l’investigation de cette région. C’est pourquoi, l’imagerie par résonance magnétique (IRM) est de plus en plus souvent utilisée pour l’investigation des boiteries du pied chez le cheval, permettant à la fois une investigation des structures osseuses et des tissus mous (Dyson et Murray, 2007b ; c ; Werpy, 2009). De nombreuses études IRM ont été réalisées sur membres isolés afin de permettre un examen différé dans le temps et dans l’espace voire d’utiliser différentes techniques d’investigation (Denoix et al., 1993 ; Whitton et al., 1998 ; Widmer et al., 1999 ; Widmer et al., 2000 ; Busoni et al., 2005 ; Murray et al., 2006 ; Spriet et al., 2007). Le protocole de conservation varie d’une étude à l’autre, utilisant en général des membres congelés puis décongelés. Une étude décrit un protocole de conservation basé sur la congélation et la décongélation du membre (Widmer et al., 1999). Cependant, ce protocole est fastidieux. De plus, plusieurs limites sont présentes dans cette étude. Dans une étude précédente sur des membres isolés, certains membres avaient été évalués ante-mortem (Murray et al., 2006). Ceux-ci ont permis une comparaison qualitative des images ante-mortem et post-mortem d’un même pied sans mise en évidence de changement de signal. Cependant, aucune étude quantitative n’a été réalisée et il n’est pas précisé comment la comparaison a été réalisée et sur bases de quels critères. Différents systèmes sont maintenant disponibles pour l’IRM du pied équin dont notamment une machine permettant l’examen des membres sur chevaux debout, uniquement sous sédation (Mair et al., 2005) contrairement aux systèmes adaptés de la médecine humaine où l’anesthésie générale est toujours nécessaire. Cependant, aucune étude sur des chevaux, n’a comparé la qualité des images obtenues sur des machines avec une intensité de champ magnétique différente si ce n’est une étude sur le cartilage et l’os sous-chondral (Tapprest, et al., 2003). Cette étude a comparé un système de bas champ (low field - LF) pour chevaux couchés à un système de haut champ (high field –HF). Elle a démontré une différence entre les 2 machines uniquement pour la détection de lésion cartilagineuse de bas grade. La comparaison d’un système pour chevaux debout à un système de haut champ n’a jamais été réalisée si ce n’est par le biais de la littérature humaine. Aucune unanimité sur les séquences et plans de coupe à utiliser lors d’examen IRM du pied équin n’a été établie dans la littérature. La majorité des études utilisent 3 séquences différentes (T1, T2, séquence avec suppression de la graisse) dans les 3 plans de coupe (Whitton et al., 1998 ; Dyson et al., 2003 ; Murray et al., 2003 ; Dyson et al., 2004 ; Zubrod et al., 2004). Les objectifs suivants ont donc été établis : 1. évaluer le changement dans le temps du signal IRM du pied équin sain réfrigéré à 4°C (étude I : effets sur l’image de la conservation des membres isolés), 2. évaluer l’effet sur la qualité de l’image IRM du pied équin sain du cycle de congélation-décongélation et du type de procédé de décongélation (étude II : effets sur l’image de la conservation des membres isolés), 3. comparer qualitativement les images IRM de mêmes pieds sains isolés obtenues sur 3 systèmes avec une intensité de champ différente (0.27 Tesla (T), 1.5T et 3T) (étude III : effets sur l’image du champ magnétique), 4. établir un ou plusieurs protocoles courts d’examen IRM du pied équin en choisissant les séquences les plus appropriées dans un nombre limité de plans de coupes, permettant de visualiser les différentes structures anatomiques les plus souvent atteintes lors de pathologie du pied équin (étude IV : effets sur l’image des séquences et plans de coupe). Résultats: Les Etudes I et II ont permis de démontrer l’effet de la conservation des pieds isolés sur la qualité de l’image. Aucun changement de la qualité de l’image n’a été mis en évidence lors de la réfrigération (Etude I). Une légère diminution de la taille des récessus synoviaux a été observée subjectivement. Aucun changement de signal n’a été noté subjectivement si ce n’est pour la moelle osseuse, qui apparait légèrement plus hyperintense en séquence Short Tau Inversion Recovery (STIR) et légèrement plus hypointense en Turbo Spin Echo (TSE) pondérée en T2 après réfrigération comparé à T0. L’analyse quantitative a démontré un changement significatif du rapport signal sur bruit (SNR) dans la moelle osseuse des membres réfrigérés lorsqu’ils sont comparés à T0 en séquences STIR et en TSE pondérée en T2. Le réchauffement à température ambiante produit l’effet inverse sur le SNR avec une augmentation significative du SNR en TSE pondérée en T2. Après 14 jours de réfrigération, une diminution du SNR a été observée dans la moelle osseuse avec les séquences TSE pondérée en T2 et Double Echo in Steady State (DESS). Le signal du tendon fléchisseur profond du doigt n’a pas montré de changement significatif avec la réfrigération. Aucun changement de netteté d’images n’a été observé dans l’étude II, si ce n’est pour la partie dorsale et distale du sabot après congélation-décongélation. En effet, celle-ci apparaît hyperintense après congélation-décongélation dans toutes les séquences utilisées dans l’étude II mais de manière plus marquée en séquences TSE T2/PD et STIR. La liaison kéraphylle-podophylle est moins visible en séquences Gradient Echo (GE) T2* et TSE T2/PD après congélation-décongélation. A l’exception du tendon, de petits changements de signaux ont été observés subjectivement dans toutes les structures investiguées mais pas dans toutes les séquences après un cycle congélation/décongélation. L’analyse quantitative a démontré un changement de signal significatif dans la moelle osseuse en Spin Echo (SE) pondérée en T1 uniquement pour P3 lorsque les pieds sont décongelés à température ambiante avant l’examen. En ce qui concerne les pieds décongelés à 4°C, les changements de SNR de la moelle osseuse ont été observés dans toutes les structures osseuses et avec différentes séquences. Des changements de signal ont été significatifs dans le récessus synovial lorsque les extrémités digitées sont conservées à 4°C avant l’examen et ne sont pas retrouvés lorsque les pieds sont laissés à température ambiante pendant 24h. Les structures tissulaires telles le coussinet digital, la peau et le tissu sous-cutané, le DDFT ont montrés la plupart du temps une augmentation significative du SNR due à la congélation-décongélation et ceci avec les 2 types de décongélation (température ambiante vs. à 4°C). Ces changements étaient plus souvent présents avec les séquences GE qui semblent donc plus sensibles aux variations de signal induites par les conditions de conservation. En ce qui concerne l’effet de l’intensité du champ magnétique sur la qualité de l’image (Etude III), les images obtenues dans chaque examen avec chaque machine étaient de valeur diagnostique à l’exception des images de la boite cornée où des artéfacts considérables ont été observés avec le système de bas champ pour chevaux debout, créant une distorsion et une perte de signal dorsalement et/ou distalement. Ces artéfacts étaient plus important en GE pondérée en T2*. Les valeurs de scores qualitatifs obtenues pour les différentes structures anatomiques à 3T et 1.5T (systèmes HF) étaient significativement plus grandes que les scores obtenus à 0.27T (système LF pour chevaux debout). Les scores des images obtenues à 3T étaient significativement plus grands que les scores obtenus à 1.5T. La moyenne des scores de chaque structure anatomique évaluée était statistiquement inférieure pour les images acquises avec le système LF pour chevaux debout par rapport aux images obtenues avec les 2 systèmes HF. La différence de moyenne des scores entre les 2 systèmes HF était inférieure à la différence de moyenne des scores entre les systèmes HF et le système LF pour chevaux debout. Cependant, la différence de moyenne des scores entre les systèmes HF était significative. La phalange distale, les cartilages unguéaux, l’os sésamoïde distal, le tendon fléchisseur profond du doigt, le ligament annulaire digital distal, le ligament sésamoïdien distal impair, le coussinet digital, le sabot et la couronne ont obtenus la plus grande différence en moyenne de scores (>1 point de score) entre le système LF et les systèmes HF. Le cartilage et l’os sous-chondral de l’articulation interphalangienne distale (AIPD) sont les structures avec la moindre différence de moyenne de scores entre le système LF et les systèmes de HF (< 0.6 point de score entre le système de bas champ et 1 ou 2 des systèmes de haut champ). La différence de moyenne de scores entre les images obtenues à 1.5T et les images obtenues à 3T a été plus importante pour le cartilage de l’AIPD et les cartilages unguéaux (> 0.2 point de score). Trois protocoles courts ont été proposés par l’Etude IV. Le premier utilise principalement les séquences de SE, une séquence avec atténuation de la graisse et une séquence plus spécifique pour l’évaluation du cartilage. Ces séquences sont: SE pondérée en T1 dans le plan transversal 2 (perpendiculaire au cortex palmaire de l’os sésamoïde distal), TSE dual echo pondérée en T2 et en PD dans le plan sagittal, STIR dans le plan sagittal, DESS 3D sans excitation selective de l’eau (sans WE) dans le plan dorsal 1 (parallèle à l’axe de l’extrémité digitée). Le deuxième protocole utilise en plus les séquences GE intéressantes pour mettre en évidence les sites d’hémorragie et le cartilage articulaire. Les séquences utilisées sont : GE pondérée en T1 en 3D dans le plan dorsal 1, SE pondérée en T1 dans le plan transversal 2, GE 2D pondérée en T2* dans le plan transversal 2, TSE dual echo pondérée en T2 et en PD dans le plan sagittal, STIR dans le plan sagittal, DESS 3D sans WE dans le plan sagittal. Le troisième ajoute des plans de coupe particuliers : un perpendiculaire à l’insertion distale du tendon fléchisseur profond du doigt (dorsal 3) et l’autre perpendiculaire aux ligaments collatéraux de l’articulation interphalangienne distale (transversal 3) ainsi qu’une séquence supplémentaire alliant visualisation du cartilage et suppression de la graisse. Les séquences utilisées sont : GE pondérée en T1 en 3D dans le plan dorsal 1, SE pondérée en T1 dans le plan transversal 2, GE pondérée en T2* en 2D dans le plan transversal 2, TSE dual echo pondérée en T2 et en PD dans le plan sagittal, STIR dans le plan transversal 2, TSE dual echo dans le plan dorsal 3, TSE dual echo dans le plan transversal 3, DESS 3D avec WE dans le plan sagittal. Conclusions et Perspectives: Les Etudes I et II ont permis de démontrer l’effet de la conservation des pieds isolés sur la qualité de l’image. Les changements de SNR significatifs rencontrés dans les études I et II démontrent que la conservation influence l’image IRM et que lors des études ex vivo, les facteurs liés à la conservation et à la température du membre doivent être pris en considération pour interpréter tout résultat. Aussi bien sur les membres réfrigérés que sur ceux congelés, aucun changement de netteté d’images n’a été observé dans ce travail, si ce n’est pour la partie dorsale et distale du sabot après congélation-décongélation. Etant donné ces changements, il sera conseillé dans le futur de réaliser les études concernant le sabot sur pieds frais ou réfrigérés. La réfrigération est une méthode simple de conservation ne nécessitant aucune planification de l’examen. Ceci est particulièrement attrayant car de nombreux examens à des fins expérimentales doivent être insérés entre les patients cliniques, voire reportés en fin de journée. De plus, si le flux de patients de la journée est plus élevé que prévu, l’examen de ces extrémités digitées peut être reporté au lendemain. La congélation du membre quant à elle nécessite une planification car une décongélation préalable est indispensable. En effet, les protons des structures gelées ne sont pas mobiles et n’engendrent donc pas ou peu de signal (Widmer et al., 1999). Une légère diminution de la taille des récessus synoviaux a été observée subjectivement après réfrigération mais pas après congélation-décongélation. Ceci peut être dû à l’utilisation de gants pour recouvrir les pieds dans la seconde étude, or ceci n’avait pas été utilisé lors de la première étude. En effet, il a été démontré que la perte de poids de la viande par déshydratation à température basse lors du stockage est inférieur lorsque la viande est emballée (Bustabad, 1999). Aucun changement de signal n’a été noté subjectivement lors de réfrigération et ceci jusqu’à 14 jours, si ce n’est pour la moelle osseuse. L’analyse quantitative a démontré un changement significatif du SNR dans la moelle osseuse des membres réfrigérés lorsqu’ils sont comparés à T0 en séquences STIR et TSE pondérée en T2 et le réchauffement à température ambiante a produit l’effet inverse sur le SNR comparé à la réfrigération. Il faudra donc tenir compte des changements dus à la température du membre et si nécessaire ramener le spécimen à température ambiante si une étude ex vivo est entreprise sur des pieds réfrigérés. Le changement de signal en STIR avec la température démontré dans l’étude I ne semble pas avoir été décrit précédemment. Le TI optimal peut varier entre individus et entre différentes parties du corps (Shuman et al., 1989 ; Shuman et al., 1991). Comme le T1 de la moelle osseuse diminue légèrement à modérément avec une diminution de la température (Petrén-Mallmin et al., 1993), une suppression incomplète de la graisse en STIR sur des membres réfrigérés a eu lieu suite au changement de température. De ce fait, une suppression incomplète du signal de la graisse doit être attendue dans les examens post-mortem sur pieds réfrigérés. Une technique a été décrite pour obtenir le TI optimal (Shuman et al., 1991). Il peut donc être intéressant de faire varier le TI sur des membres réfrigérés afin d’obtenir une suppression complète du signal de la graisse et ainsi améliorer la détection de lésion discrète. Après 14 jours de réfrigération, une diminution du SNR à été observée dans la moelle osseuse avec les séquences TSE pondérée en T2 et DESS. Il est donc préférable de garder des pieds isolés dans un frigo au maximum pendant 7 jours afin d’éviter cette chute du SNR due à la dégradation des tissus, même si la qualité de l’image ne semble pas changé après 14 jours de réfrigération. Une congélation-décongélation sera préférée si une conservation des membres supérieure à 7 jours est nécessaire. Une décongélation à température ambiante semble aussi préférable car elle crée moins de changement de signal. Les résultats obtenus dans ce travail, en ce qui concerne le changement de signal en fonction de la conservation, sont très intéressants et il y a très peu de travaux publiés à ce sujet. Cependant, ces résultats entrainent de nombreuses autres questions. Ainsi, l’établissement d’une courbe en fonction de la température interne des tissus semble intéressant afin de mieux cerner à partir de quelle température les changements s’opèrent. De plus, les résultats de cette étude pourraient également servir à l’évaluation d’examen in vivo notamment pour les examens réalisés lors de température extérieure ou corporelle anormalement élevée ou basse qui pourrait avoir une influence sur le signal obtenu pour les différentes structures tel le phénomène de « cold-limb syndrome » retrouvé en scintigraphie (Dyson, 2007). Une évaluation du changement de signal du liquide synovial en fonction de la température et en fonction du temps semble également intéressante car celui-ci montre un comportement différent par rapport aux autres tissus. Comme les pieds examinés dans cette étude ne l’ont été que dans les 12h après la mort des animaux, une étude comparant le signal des différentes structures in vivo à ces mêmes structures ex vivo juste après la mort permettrait une évaluation des changements précoces obtenus après la mort. De même, il semble intéressant d’évaluer ces méthodes de conservation sur des pieds pathologiques afin de voir si ce type de conservation n’influence pas la qualité du diagnostic. En médecine humaine et vétérinaire, la préservation du sperme des ovocytes et d’autres tissus reporte différents résultats en fonction de la température de congélation ainsi que de la vitesse de celle-ci et de la température de décongélation (Cui et al., 2007 ; Luciano, et al., 2009). Une étude faisant varier ces paramètres permettrait l’obtention de protocoles idéaux pour la préservation des pieds entre les examens. De même, une étude histologique lors de ces différents protocoles permettrait l’établissement de protocole plus adapté à un examen histopathologique permettant une meilleure compréhension de la physiopathologie des lésions affectant le pied. L’Etude III a démontré l’effet de l’intensité du champ magnétique (0.27T, 1.5T, 3T) sur la qualité des images de pieds normaux. Les images obtenues dans chaque système étaient de valeur diagnostique à l’exception des images de la boite cornée où des artéfacts considérables ont été observés avec le système LF. Ces artéfacts sont dus aux inhomogénéités de champ et à des artéfacts métalliques. Ces artéfacts étaient plus important en GE pondérée en T2* car cette séquence est plus sensible aux inhomogénéités de champ (Kastler, 2003). Si une lésion est suspectée dans une région périphérique du pied, il est donc conseillé de placer cette région au centre de l’aimant dans le système LF pour chevaux debout. Ceci permettra d’avoir la région à investiguer dans la zone la plus homogène du champ magnétique et de réduire les artéfacts. L’étude III confirme que dans les séquences SE, moins d’artéfacts sont visibles dans le sabot. Une séquence SE est donc conseillée dans le système LF pour chevaux debout si une lésion périphérique du pied est suspectée. Avec les paramètres que nous avons utilisés pour l’Etude III, la qualité subjective de l’image et la visualisation des structures anatomiques du pied sain étaient meilleures sur les images obtenues avec les systèmes HF. Le système 3T offre la meilleure visualisation des structures anatomiques communément impliquées dans les boiteries du pied chez le cheval lorsque celle-ci est comparée aux systèmes 1.5T et 0.27T pour chevaux debout. Ce système 3T pourrait donc se révéler supérieur pour la détection de lésions plus discrètes telles des lésions cartilagineuses de bas grade, les lésions plus précoces ou la détection de lésion atteignant des structures anatomiques de petite taille telle le ligament annulaire digital distal, le ligament sésamoïdien distal impair. Les résultats obtenus lors de l’étude III sont en faveur des systèmes HF. Toutefois, en médecine humaine, même si les images avec les systèmes HF sont de meilleures qualités, plusieurs études montrent une efficacité diagnostique semblable avec un système LF (Barnett, 1993 ; Taouli et al., 2004). Or, en médecine vétérinaire, le système LF pour chevaux debout prend une place de plus en plus importante aussi bien dans le diagnostic, le pronostic, le choix du traitement et le suivi des boiteries chez le cheval (Mair et al., 2005). Ceci est dû au fait que de plus en plus de propriétaires acceptent de réaliser l’examen car aucune anesthésie du cheval n’est nécessaire. De plus, en présence d’un cheval de haute valeur, le choix d’un traitement optimal est important pour le retour à une carrière équivalente. C’est pourquoi, il est particulièrement important d’évaluer la qualité diagnostique de ce système LF, notamment en le comparant au système HF et ceci avec les mêmes pieds pathologiques. La plupart des pieds pathologiques ont souvent une combinaison de lésions atteignant plusieurs structures anatomiques sur un même pied (Busoni et al., 2005 ; Murray et al., 2006 ; Dyson et Murray, 2007a). C’est pourquoi le choix d’un protocole permettant la visualisation de la plupart des structures anatomiques du pied est important. L’optimisation de quelques protocoles réalisée dans l’étude IV répond à un besoin de standardisation et à une recherche de données objectives sur lesquelles baser le choix de plans et séquences. Trois protocoles courts d’examen IRM ont été établis lors de l’Etude IV. Les 2 premiers protocoles ont donné une priorité aux structures les plus souvent atteintes lors de douleurs du pied tel l’os sésamoïde distal et le tendon fléchisseur profond du doigt (Murray et al., 2006 ; Dyson et Murray, 2007a), tout en permettant une évaluation des autres structures. L’utilisation d’un plan de coupe transversal perpendiculaire au cortex palmaire de l’os sésamoïde distal sera préférée à un plan perpendiculaire à l’axe digité. En effet, en utilisant ce plan, une plus grande partie du cartilage entre l’os sésamoïde distal et la phalange moyenne est visualisée. De même, l’utilisation d’un plan dorsal parallèle à l’axe digité sera préférée à un axe parallèle au cortex palmaire de l’os sésamoïde distal permettant la visualisation d’une plus grande partie du cartilage articulaire de AIPD et ceci dans sa partie la plus centrale. L’utilisation de séquence en 3D permet le reformatage des images et ainsi d’obtenir des images dans un meilleur axe par rapport aux différentes structures telles les ligaments collatéraux de l’AIPD (Dyson et al., 2008 ; Gutierrez-Nibeyro et al., 2009). Le troisième protocole permet une meilleure visualisation de structures impliquées moins fréquemment dans les boiteries du pied tel les ligaments collatéraux de l’AIPD, le ligament sésamoïdien distal impair et les marges distales de la phalange distale (Murray et al., 2006 ; Dyson et al., 2008). Une séquence 3D réalisées dans le plan sagittal s’est révélée meilleure pour le reformatage du cartilage entre l’os sésamoïde distal et la phalange moyenne. Les trois protocoles utilisent des séquences en différentes pondérations et une séquence avec saturation de graisse comme recommander précédemment (Tucker et Sampson, 2007). Le choix des séquences et des plans de coupes semble allier temps d’examen réduit et visualisation correcte de toutes les structures. D’un point de vue pratique, le choix des bonnes séquences et des bons plans permet de réduire le temps d’anesthésie sur les animaux anesthésié et permet de réduire le risque de mouvement sur chevaux sédatés lors d’examens réalisés sur chevaux debout. Cependant, la comparaison de l’efficacité diagnostique entre un protocole court et un protocole long sur des pieds ou des chevaux pathologiques (contenant tous les plans pour chaque séquence) est nécessaire afin de confirmer l’efficacité de ceux-ci. Ce travail a permis de démontrer le rôle essentiel joué par la conservation des membres lors des études ex vivo (études I et II) et de part l’évaluation des différents systèmes, séquences et plans (études III et IV) permet une analyse critique de la littérature précédente et jette les bases nécessaires à une future standardisation des protocoles d’IRM du pied équin. [less ▲]

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See detailIN VITRO NUCLEAR AND CYTOPLASMIC MATURATION OF THE EQUINE OOCYTE: INFLUENCE OF CYSTEAMINE
Deleuze, Stefan ULg

Doctoral thesis (2009)

Research on in vitro embryo production (IVP) in the equine is impeded by the limited availability of mature oocytes as the mare is mono ovulating and superovulation is still difficult (Dippert and Squires ... [more ▼]

Research on in vitro embryo production (IVP) in the equine is impeded by the limited availability of mature oocytes as the mare is mono ovulating and superovulation is still difficult (Dippert and Squires, 1994; Bezard et al., 1995; Alvarenga et al., 2001b). Despite recent improvement in IVM of equine oocytes, success rates of IVM in that species remain low in all culture media tested compared to other species (Goudet et al., 2000b). However, most studies have focused on the percentage of oocytes reaching the metaphase II stage (nuclear maturation) but few concentrated on the final oocyte competence as measured by its ability to develop into a blastocyst and further establish a pregnancy. Blastocyst production rate is influenced not only by culture environment but also by oocyte maturation conditions. Under in vitro culture conditions, oxidative modifications of cell components via increased ROS represent a major culture induced stress (Johnson and Nasr-Esfahani, 1994). Anti-oxidant systems can attenuate the deleterious effects of oxidative stress by scavenging ROS (Del Corso et al., 1994). Glutathione, a tripeptide thiol, is the major non-protein sulfydryl compound in mammalian cells that plays an important role in protecting the cell from oxidative damage (Meister and Tate, 1976; Meister and Anderson, 1983). It has been suggested that GSH content in oocytes may serve as a reservoir protecting the zygote and the early embryos from oxidative damage before genomic activation and de novo GSH synthesis occur (Furnus et al., 1998; de Matos and Furnus, 2000). The addition of GSH synthesis precursors, such as cysteamine, a thiol compound, to IVM media has been shown to improve IVP in various species (Takahashi et al., 1993; de Matos et al., 1995; Grupen et al., 1995; de Matos et al., 2002a; de Matos et al., 2002b; de Matos et al., 2003; Gasparrini et al., 2003; Oyamada and Fukui, 2004; Balasubramanian and Rho, 2007; Anand et al., 2008; Singhal et al., 2008; Zhou et al., 2008). Very little information on the use of thiol compounds in the equine is available. Conventional in vitro fertilization (IVF) has not been successful in the mare, and a repeatable IVF technique has not yet been developed (Alm et al., 2001). To overcome the limitation of conventional IVF procedures, other methods to produce embryos from oocytes, either in vivo or in vitro, have been investigated. Among these, intra cytoplasmic sperm injection (ICSI) has permitted efficient equine in vitro blastocyst production (Galli et al., 2002; Lazzari et al., 2002; Choi et al., 2006a; Choi et al., 2006c). However, ICSI requires specific equipment and skills. Transfer of an immature oocyte into the preovulatory follicle of an inseminated recipient mare (Intra-Follicular Oocyte Transfer, IFOT) has produced embryos but the success rate was low (Hinrichs and Digiorgio, 1991). Similarly, oocyte transfer (OT) into the oviduct of an inseminated recipient mare was investigated (McKinnon et al., 1988; Carnevale, 1996; Hinrichs et al., 1997; Carnevale et al., 2001; Carnevale et al., 2003; Carnevale, 2004), and commercial programs using OT for mares with reproductive abnormalities are now available (Carnevale et al., 2001). Unfortunately, IFOT is poorly documented in the literature and reports of OT have been published by various laboratories and under various conditions, making comparisons between results and choosing among these as substitutive techniques to ICSI or embryo transfer difficult. The first aim of the present work was to investigate if there is an influence of supplementation with 100 µM of cysteamine on conventional IVF success rate. Cumulus oocytes complexes (COCs) retrieved by transvaginal ultrasound guided aspiration were matured in vitro with or without cysteamine supplementation and were then submitted to conventional IVF using either calcium ionophore or heparin as capacitation treatment for spermatozoa. A total of 131 oocytes were evaluated for evidence of sperm penetration. Both techniques (ionophore or heparin) yielded 6% of IVF and results were similar both for the cysteamine and the control group. This success rate of IVF is low compared to some published data (Palmer et al., 1991; Dell'Aquila et al., 1996; McPartlin et al., 2009) but similar to what others reported in the literature (Choi et al., 1994; Dell'Aquila et al., 1997a). Although, it seems likely that cysteamine did not significantly improve IVF rates under our conditions, our general success rates for IVF procedures may be too low for us to conclude definitely about the effect of cysteamine. As ICSI was not available to us, the second aim of this work was to determine what in vivo technique could best bypass the lack of an efficient conventional IVF procedure. We compared embryo production following transfer of in vivo recovered oocytes (1) into a recipient’s oviduct or (2) into her preovulatory follicle either immediately after ovum pick up or (3) after in vitro maturation. Recipients were inseminated with fresh semen of a stallion with a known normal fertility. Ten days after transfer, rates of embryos collected in excess to the number of ovulations were calculated and compared for each group. Embryo collection rates were 32.5% (13/40), 5.5% (3/55) and 12.8% (6/47) for OT, post-IVM and immediate IFOT respectively. OT significantly yielded more embryos than immediate and post-IVM IFOT did. These results show that, when ICSI is not an option, intra-oviductal oocyte transfer is to be preferred to IFOT, as an in vivo alternative, to bypass the inadequacy of conventional in vitro fertilization and to assess oocyte developmental competence. After it was established that in comparison to IFOT, OT is the most reliable in vivo alternative to in vitro fertilization where ICSI technology is not available, this technique was used to assess the effect of cysteamine supplementation on nuclear maturation and oocyte competence. The third aim of this work was to investigate the influence of supplementation with 100 µM of cysteamine on in vitro nuclear and cytoplasmic maturation by specific DNA staining and the ability of oocytes to undergo in vivo fertilization after OT. Oocytes were collected by transvaginal ultrasound guided aspiration and matured in vitro with (cysteamine group) or without (control group) cysteamine. The nuclear stage after DNA Hoechst staining and the embryo yield following OT were used as a criterion for assessing nuclear and cytoplasmic maturation, respectively. Overall maturation rate was 52%, which is rates reported in the literature ranging from 40 to 70% in the equine (Goudet et al., 1997a; Bogh et al., 2002; Hinrichs et al., 2005; Galli et al., 2007). Nuclear maturation was not statistically different (p>0.05) between oocytes cultured with or without cysteamine (55% and 47% respectively). From 57 oocytes transferred to the oviduct in each group, the number of embryos collected was 10 (17%) in the control group and 5 in the cysteamine group (9%). Those two percentages were not statistically different (p>0.05). Contrary to the data described in other domestic species, there was no effect of cysteamine on in vitro nuclear maturation, or in vivo embryonic development under our conditions. Under our conditions, the addition of 100 µM of cysteamine to a classic culture medium does not improve equine oocyte maturation or embryonic development after OT. The same dose failed to increase GSH content in the equine (Luciano et al., 2006). However, the effect of cysteamine supplementation is highly species and concentration dependant. The inadequacy of the chosen concentration may explain that equine embryo production has not been increased by the cysteamine under our conditions as opposed to what has been observed in many other species. Alternatively, we can hypothesize that some substances present in the IVM medium can interfere with GSH synthesis. This has been suggested for FSH and estradiol (Bing et al., 2001) and, although our maturation medium is not supplemented with gonadotropins or estradiol, factors contained in fetal calf serum or EGF might also have an effect on GSH synthesis. Considering its beneficial effects in many other species, supplementation with cysteamine to different IVM media should be further investigated in the equine. Ideally combining different concentrations and ICSI or OT in order to determine an optimal concentration and its effects on oocyte developmental competence. [less ▲]

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See detailMise au point d’un réacteur biphasique eau/huile de silicone destiné au traitement des composés organiques volatils hydrophobes au sein des effluents gazeux
Aldric, Jean-Marc ULg

Doctoral thesis (2009)

Recently, a lot of research has been devoted to the study of two-phase partitioning bioreactors (TPPB) as new technology for xenobiotic degradation in gaseous effluents. These reactors involve the use of ... [more ▼]

Recently, a lot of research has been devoted to the study of two-phase partitioning bioreactors (TPPB) as new technology for xenobiotic degradation in gaseous effluents. These reactors involve the use of a second non-aqueous phase to improve the solubility and transfer of hydrophobic compounds. In this work, we have developed a stirred two-phase partitioning bioreactor using silicone oil as second phase. Initially, Rhodococcus erythropolis T 902.1 was selected on the basis of its capacity to metabolize isopropyl-benzene (IPB), used as representative of the benzene-containing compounds. Secondly, the mass transfer of both IPB and oxygen has been considered with relation to their influence on the hydrodynamics of the reactor and the type of silicone oil used. The addition of 10% low viscosity silicone oil (10 cSt) in the reactor does not significantly affect the oxygen transfer rate. The very high solubility of IPB in the silicone oil leads to an enhancement of the driving force term, especially when high proportion of silicone oil are used. However, it is not necessary to use a volume fraction higher than 10% since KLaIPB and KLaO2 decrease sharply at above such proportion. In addition, an optimal concentration appeared to exist for both biotic components, respectively 0,5 g/L and 0,7 g/L for biomass (B) and surfactant extract (SE) when the global mass transfer coefficient (KLa) of oxygen was measured in the TPPB. More specifically, SE improved the interfacial area “a” by decreasing the bubble diameter, while B reduced it at concentrations up to 1 g/L. In contrast, the SE concentration acted negatively on KL, while it was favoured by the B concentration. In term of performances, it was clearly shown that the biodegradation rate is more directly related to the inlet flow of IPB than to the concentration of IPB in the inlet gas. The TPPB was monitored for 38 days to characterise its behaviour under several operational conditions. During an intermittent loading phase (10 h/day), the average elimination capacity remained above 240 g/m3.h for an average IPB inlet load of 390 g/m3. h. Finaly, an original approach was developed using a scale-down bioreactor allowing to reproduce the hydrodynamics encountered under full scale TPPB. It was clearly shown that the IPB affects negatively the scaling-up of the process by increasing the speed of phase partitioning. However, this negative impact was strongly compensated by the presence of biotic compounds stabilizing the two phase system and rendering the scaling-up process feasible. In conclusion, the use of a water-silicone oil TPPB to remove a high inlet load of IPB was successful. The proposed reactor retains a high potential for the biological treatment of gas effluents polluted by hydrophobic aromatic compounds. The suggested process might be applied in the range of concentration and flow where thermal oxidation is too expensive (between 1 and 7 g/Nm3) or when the biofilters are usually limited, i.e. to treat a polluted effluent concentrated with > 1 g/Nm3 at a flow of 90m3/m3.h. [less ▲]

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See detailetude de la diversité enzymatique des microorganismes du sol par l'approche métagénomique
Berlemont, Renaud ULg

Doctoral thesis (2009)

Functional metagenomic approach was performed using total environmental DNA extracted from a temperate forest soil sample and from an Antarctica soil sample. Searching for clones harbouring phenotypes ... [more ▼]

Functional metagenomic approach was performed using total environmental DNA extracted from a temperate forest soil sample and from an Antarctica soil sample. Searching for clones harbouring phenotypes related to the production of new hydrolytic enzyme allows the isolation of several new enzymes. Amongst them, an esterase and a cellulase, named RBest1 and RBcel1 respectively, were characterized. By accurate description of their catalytic proprieties these two new enzymes appear to present interesting features. The RBest1 esterase is an enzyme whose activity is stabilised or improved in presence of non water-miscible organic solvent. By sequence analysis, RBest1 is related to other organic solvent tolerant enzyme. Moreover, in aqueous buffer, RBest1 is highly specific for butyrate compound but surprisingly its specificity appears to be shifted in presence of organic solvent. The RBcel1 cellulase, was thoroughly characterized for its involvement both in cellulose degradation and production. Our data highlight the requirement for such enzyme in the bacterial cellulose synthesis process. According to our results, the mining of metagenomic libraries by functional screening associated to detailed description of the isolated enzymes gives hints for both ecological and microbiological questions. [less ▲]

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See detailDroplet manipulations
Gilet, Tristan ULg

Doctoral thesis (2009)

In this thesis, we discuss some physical phenomena related to the manipulation of droplets, and their possible use as alternatives for digital microfluidics. In a first part, the behavior of droplets in ... [more ▼]

In this thesis, we discuss some physical phenomena related to the manipulation of droplets, and their possible use as alternatives for digital microfluidics. In a first part, the behavior of droplets in the vicinity of another liquid interface is explored. We have shown that droplets can be kept bouncing onto a liquid interface, provided this latter is vertically vibrated. The bouncing mechanisms are investigated in several configurations. Bouncing droplets may also experience self-propulsion and partial coalescence. The second part of this thesis is dedicated to the study of droplets sliding down fibers. The basic microfluidic operations are advantageously implemented with simple fiber networks. [less ▲]

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See detailEtude de la diversité trophique des poissons demoiselles (Perciformes, Pomacentridae) par l'examen des variations du squelette céphalique à partir de leur vie récifale
Frederich, Bruno ULg

Doctoral thesis (2009)

Damselfishes (Pomacentridae) are among the most speciose coral reef fishes (>350 species). They are abundant, constituting a large proportion of the individuals at small spatial scale. Despite this ... [more ▼]

Damselfishes (Pomacentridae) are among the most speciose coral reef fishes (>350 species). They are abundant, constituting a large proportion of the individuals at small spatial scale. Despite this importance, few studies deal with their trophic and morphological diversity. As most coral reef fishes, damselfishes have a complex life-cycle with two distinct phases: (1) a potentially dispersive pelagic larval phase and (2) a sedentary adult phase associated to the coral reef environment. The larval phase ends at reef settlement. The pelagic environment offers a relatively homogeneous habitat for all pomacentrids larvae which exclusively feed on planktonic copepods. On the other hand, the variety of resources is higher in the coral reef. During ontogeny, damselfishes undergo a change in their lifestyle that involves an ontogenetic change in morphology, physiology and behavior in order to maximize survival in each environment. This thesis aims to test the hypothesis that a higher trophic diversity at the adult stage corresponds to a higher disparity level (measure of morphological diversity of a clade) than in larvae. To answer this question, the research has been divided into three main axis. Firstly, the stable isotope (δ15N and δ13C) and stomach content analyses in thirteen sympatric species of damselfishes have highlighted three main groups according to their foraging strategies: (1) the pelagic feeders which feed on planktonic copepods, (2) the benthic feeders which are mainly herbivorous grazing filamentous algae and (3) an intermediate group including species which pick up their prey in the pelagic and the benthic compartment in variable proportions (e.g. planktonic and benthic copepods, small vagile invertebrates and filamentous algae). Only two species are known to be exclusively coral polyp feeders. Secondly, an ecomorphological study has characterized the diversity of the adults head skeleton. Shape variations of four skeletal units (neurocranium, suspensorium and opercle, mandible and premaxilla) were explored in fourteen species using landmark-based geometric morphometrics. The results reveal a parallelism between the morphological diversity and the trophic variety at the adult stage. Generally speaking, the planktivorous damselfishes show skeletal shapes enhancing suction feeding (e.g. high suspensoria and opercles, a large supraoccipital crest, short mandibles forming a small mouth) The herbivorous species (grazers) have shapes improving the robustness of some skeletal parts (e.g. high and robust mandibles, broad hyomandibular). Among the planktivorous species, Chromis viridis and C. acares show divergent shapes from the species of the same trophic guild. Their skeletal characteristics suggest they could be considered as ram-suction feeders. The buccal dentition is not highly related to the diet. Thirdly, the post-settlement ontogeny and the variation of shape disparity were studied and compared among eight species having varied diets. The post-settlement growth is highly allometric in all species (40 – 87% of shape variations). For each skeletal unit, the morphological disparity is higher at the adult stage compared with the settlement stage. All studied developmental parameters were affected by evolutionary changes. At settlement, the larval shapes are already species-specific, probably due to differences in pelagic larval duration among species. The increasing of shape disparity during ontogeny is mainly related to the divergence of allometric patterns. The length of ontogenetic trajectories and the developmental rates appear as less variable parameters. Generally speaking, no correlation exist between the phylogenetic or ecological (diet, pelagic larval duration,..) data and the developmental parameters. Species of the genus Dascyllus were studied in a particular context: a study case of giantism. The geometric morphometric methods show that the small species and the giant ones share the same ontogenetic trajectories for the neurocranium and the mandible. A part of their diversification should result from heterochronic processes. The cephalic larval shapes suggest a mode of prey capture defined as ram-suction feeding. In all studied species, the morphological transformations reveal an optimization of the suction feeding system. During growth, the main shape changes include a heightening of the suspensoria and the opercles, an elevation of the supraoccipital crest, a shortening of the mandibles and a lengthening of the ascending process of the premaxilla. In the benthic feeders, other shape changes are related to an improved biting and grazing abilities (e.g. mandibles and suspensorium appear more robust at the adult stage). [less ▲]

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See detailAgreement between raters and groups of raters
Vanbelle, Sophie ULg

Doctoral thesis (2009)

Agreement between raters on a categorical scale is not only a subject of scientific research but also a problem frequently encountered in practice. Whenever a new scale is developed to assess individuals ... [more ▼]

Agreement between raters on a categorical scale is not only a subject of scientific research but also a problem frequently encountered in practice. Whenever a new scale is developed to assess individuals or items in a certain context, inter-rater agreement is a prerequisite for the scale to be actually implemented in routine use. Cohen's kappa coeffcient is a landmark in the developments of rater agreement theory. This coeffcient, which operated a radical change in previously proposed indexes, opened a new field of research in the domain. In the first part of this work, after a brief review of agreement on a quantitative scale, the kappa-like family of agreement indexes is described in various instances: two raters, several raters, an isolated rater and a group of raters and two groups of raters. To quantify the agreement between two individual raters, Cohen's kappa coefficient (Cohen, 1960) and the intraclass kappa coefficient (Kraemer, 1979) are widely used for binary and nominal scales, while the weighted kappa coefficient (Cohen, 1968) is recommended for ordinal scales. An interpretation of the quadratic (Schuster, 2004) and the linear (Vanbelle and Albert, 2009c) weighting schemes is given. Cohen's kappa (Fleiss, 1971) and intraclass kappa (Landis and Koch, 1977c) coefficients were extended to the case where agreement is searched between several raters. Next, the kappa-like family of agreement coefficients is extended to the case of an isolated rater and a group of raters (Vanbelle and Albert, 2009a) and to the case of two groups of raters (Vanbelle and Albert, 2009b). These agreement coefficients are derived on a population-based model and reduce to the well-known Cohen's kappa coefficient in the case of two single raters. The proposed agreement indexes are also compared to existing methods, the consensus method and Schouten's agreement index (Schouten, 1982). The superiority of the new approach over the latter is shown. In the second part of the work, methods for hypothesis testing and data modeling are discussed. Firstly, the method proposed by Fleiss (1981) for comparing several independent agreement indexes is presented. Then, a bootstrap method initially developed by McKenzie et al. (1996) to compare two dependent agreement indexes, is extended to several dependent agreement indexes (Vanbelle and Albert, 2008). All these methods equally apply to the kappa coefficients introduced in the first part of the work. Next, regression methods for testing the effect of continuous and categorical covariates on the agreement between two or several raters are reviewed. This includes the weighted least-squares method allowing only for categorical covariates (Barnhart and Williamson, 2002) and a regression method based on two sets of generalized estimating equations. The latter method was developed for the intraclass kappa coefficient (Klar et al., 2000), Cohen's kappa coefficient (Williamson et al., 2000) and the weighted kappa coefficient (Gonin et al., 2000). Finally, a heuristic method, restricted to the case of independent observations, is presented (Lipsitz et al., 2001, 2003) which turns out to be equivalent to the generalized estimating equations approach. These regression methods are compared to the bootstrap method extended by Vanbelle and Albert (2008) but they were not generalized to agreement between a single rater and a group of raters nor between two groups of raters. [less ▲]

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See detailMorphological and Mechanical Quantification of Porous Structures by Means of Micro-CT (Morfologische en mechanische kwantificatie van poreuze structuren met behulp van micro-CT)
Kerckhofs, Greet ULg

Doctoral thesis (2009)

Suitable characterization techniques for porous structures are required to (i) understand and to be able to simulate, via finite elements (FE), the structure-properties relationships and (ii) understand ... [more ▼]

Suitable characterization techniques for porous structures are required to (i) understand and to be able to simulate, via finite elements (FE), the structure-properties relationships and (ii) understand the relationship between the morphology and mechanical behaviour on one hand, and the failure mechanisms on the other hand. X-ray microfocus computed tomography (micro-CT) offers a solution as it provides a means to acquire a complete 3D set of images of the structure visualizing the internal architecture at the microscopic level in a non-destructive way. Additionally, the micro-CT images enable subsequent image analysis, resulting in an extensive 3D quantitative description of the morphology that cannot be obtained by other methods. But, one has to be aware of the fact that micro-CT images are inherently subjected to artefacts and that the image quality and accuracy depend on multiple factors. For example, the acquisition settings (target material, tube voltage and filter material) influence the X-ray spectra and hence also the image quality. The spatial resolution strongly influences the accuracy of the micro-CT images and as a result also the morphological analysis. Closely related to the latter, the material architecture has a significant influence on the micro-CT image accuracy, which is also affected by the material type. In a first part of this study, systematic, fast and user-independent protocols have been developed both for acquisition parameter optimization and for image accuracy validation, and the influence of the different factors mentioned above on the image accuracy has been investigated. As a result, when applying these protocols, the micro-CT user should know, for different material types and architectures, what the capabilities and limitations of micro-CT are for morphological assessment of porous structures. In a second part, this knowledge has been applied and the use of micro-CT has been expanded to the mechanical characterization of porous structures by combining micro-CT imaging and 3D image analysis with in-situ mechanical loading, FE analysis and local strain mapping as this combination allows to (i) provide in-situ and experimentally the mechanical properties, (ii) link the mechanical properties to the morphology, (iii) investigate the morphological changes under compressive loading, (iv) feed and validate a FE model which can be applied for the prediction of the mechanical properties that cannot readily be determined experimentally and (v) predict the failure modes by using experimental local strain mapping. [less ▲]

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See detailÉléments de toponymie générale. Du Grand-Bornand à Passamainty, terrain de longue durée et enquêtes contrastives en terrain varié dans les domaines roman, polynésien, basque et bantu
Delorme, Jérémie ULg

Doctoral thesis (2009)

Rechercher les bases d’une connaissance des toponymes renouvelée et renforcée se situe au fondement de cette thèse. Ce projet repose sur l’hypothèse selon laquelle les approches récentes et actuelles des ... [more ▼]

Rechercher les bases d’une connaissance des toponymes renouvelée et renforcée se situe au fondement de cette thèse. Ce projet repose sur l’hypothèse selon laquelle les approches récentes et actuelles des faits toponymiques peuvent être améliorées. Sa mise en œuvre invite à engager une réflexion sur les méthodes et les théories de la toponymie. Il s’agit, en s’efforçant de satisfaire aux conditions de cohérence et de rigueur d’une approche scientifique, de poursuivre un but de conceptualisation et de généralisation. Cette démarche répond à l’observation de principes essentiels : 1° aligner la toponymie sur les méthodes et les théories de la linguistique générale ; 2° privilégier l’oralité, les synchronies observables et le point de vue des locuteurs natifs, d’après un idéal d’adéquation de la toponymie, science sociale et science de terrain, à son objet, l’étude des phénomènes toponymiques ; à cette fin, 3°, tirer profit d’une longue expérience des informateurs et du terrain ; et, 4°, soumettre l’étude des toponymes à une analyse progressive, en abordant les faits toponymiques dans leur ordre logique, des plus simples au plus complexes, à travers trois thèmes de recherche majeurs – l’établissement de corpus toponymiques oraux, l’exploration approfondie des lieux désignés par des toponymes, et l’étude des formations toponymiques, menée à rebours de travaux de toponymie dont l’étymologisation constitue le thème directeur. Fondés sur la pratique d’un terrain privilégié – celui d’une toponymie francoprovençale –, les acquis de cette recherche font l’objet d’une évaluation : soumis au contrôle de toponymies-tests – futunienne, basque et comorienne –, ils ne sont tenus pour généralisables qu’après s’être vu corroborés ou amendés. [less ▲]

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See detailContribution à l’étude de l’activité antivirale et du mécanisme moléculaire de la MX1 bovine
Baise, Etienne ULg

Doctoral thesis (2009)

Summary Type I interferons (IFNs a/b) induce the synthesis of many factors belonging to the innate immune system which is known to play an essential role as the first defence line against the viral ... [more ▼]

Summary Type I interferons (IFNs a/b) induce the synthesis of many factors belonging to the innate immune system which is known to play an essential role as the first defence line against the viral infection. Among these contributors, the MX protein (a member of the large GTPase family) along with the double stranded (ds) RNA dependent protein kinase R (PKR) and the 2’5’ oligoadenylate synthetase/Rnase L system, has been shown to be one of the most efficient among the murine and the human species. The bovine counterpart of the MX system was, at the beginning of this work, described at the sole gene level (the CDS sequence) but its functional capacity was still totally unexplored. Accordingly, our first aim was to assess the ability of the bovine GTPase we called boMX1 to inhibit viruses infecting cattle. A Vero cell line (V103) conditionally expressing the boMX1 was established. To proof the concept, we firstly tested the inhibition of a canonical virus on this field, the vesicular stomatitis virus (VSV) which was confirmed to be as sensitive to boMX1 as previously shown to MXA (Homo sapiens). In a second step, we focused our investigation on the activity of boMX1 against two Paramyxoviridae viruses, the boRSV and the boPI3, both of these being sensitive to IFNs as reported in the literature and furthermore confirmed by our previous in vitro experiments. Although boMX1 was expected to be the most important factor of the type I interferon resistance recorded against boPI3 and boRSV, our study has shown that the bovine protein was not able to block these viruses belonging to the Respirovirus genus. Conversely, the famous Orthomyxoviridae virus member, Influenza A was shown to be almost completely inhibited in cells expressing boMX1. The inhibitory potential of boMX1 was so strong it could only be measured upon the replacement of the low pathogenic H1N1 strain used in the first assays by the hypervirulent H7N7 one. In this case, the protection rate was as high as 108. Typically, the value found for the human counterpart MXA is in the range of 103 – 104 and according to our knowledge, none of the MX proteins investigated so far have never been shown to be so effective against Influenza A. In the wave of these results, the well-known avian H5N1 Influenza A strain has been tested in vitro and in vivo. All the data reinforced the concept of a very high anti-Influenza A activity for BoMX1. A such important antiviral effect appeared as an opportunity to initiate an experimental approach of the largely unknown underlying mechanism(s) of the MX antiviral activity. Our first objective was to identify the “primum movens” of the inhibition mechanism. Therefore, we followed the kinetic of the infection in V103 expressing or not the boMX1 during one single cycle. The evidence of an important activity of the bovine GTPase in the first hours post-infection led us to identify at the RNA level which replication step was the first to be blocked. Following the collected results, we adapted a primer extension method to quantify the genomic viral RNA (vRNA) early entry in the induced and non induced cell cultures. Finally, we tested a first interaction hypothesis between the boMX1 and a potential interacting protein sister. [less ▲]

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See detailLa justice réparatrice en milieu carcéral : plasticité d’une fonction et malléabilité d’un concept criminologique
Dubois, Christophe ULg

Doctoral thesis (2009)

Although it is recognized as being inhuman by some people and inefficient by others, prison only seldomly serves as a gathering political objective. The ministerial circular of 4 October 2000, which is ... [more ▼]

Although it is recognized as being inhuman by some people and inefficient by others, prison only seldomly serves as a gathering political objective. The ministerial circular of 4 October 2000, which is implementing « restorative justice » in Belgian prisons, seems however to be an outstanding case in this matter as it includes prison in the political program. The new “restorative” discourse carried out by this circular creates a new role of “restorative justice consultant” and plans to assign one in each prison. The purpose of this book is to describe, analyze and account for the concrete practices through which this political discourse tends to take some social forms. Through an ethnographic work, the new “restorative” practices will be depicted and replaced in a policy and organizational analysis based on four case studies. [less ▲]

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See detailLa fonction récréative des massifs forestiers wallons : analyse et évaluation dans le cadre d'une politique forestière intégrée
Colson, Vincent ULg

Doctoral thesis (2009)

An analysis of forest recreation in Wallonia has been carried out. The originality of the approach resides mainly in the fact that a regional scale was used. The precise meaning of “forest recreation” was ... [more ▼]

An analysis of forest recreation in Wallonia has been carried out. The originality of the approach resides mainly in the fact that a regional scale was used. The precise meaning of “forest recreation” was clarified by limiting it to the non benefit services. The analysis of the public demand was performed by means of three main surveys: a phone survey based on a sample of the Walloon and Brussels population, a survey within 40 woodlands (during 6 periods) and, finally, a survey conducted among managers of Forest Service districts in order to map the visitation level of all Walloon woodlands. Data concerning the recreational supply of the Walloon forest have been gathered as well. These data concerning supply and demand were used to create a model capable of forecasting the number of visits for the whole Walloon forest according to local population, one day tourists and holidaymakers. An economic assessment of these visits and the whole recreational function of the Walloon forest was made by adapting two methods (travel costs and the contingent valuation method) to the Walloon regional context and to the available data. All these investigations provided the quantification of the importance of the recreational function at a regional level as well as highlighting local variations. Recommendations related to the taking into account of forest recreation in forest policy, both at the regional level and at the local level were therefore proposed. [less ▲]

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See detailGenotype by Environment Interaction for Production Traits of Holsteins Using Two Countries as Model: Luxembourg and Tunisia
Hammami, Hedi ULg

Doctoral thesis (2009)

Under globalization, breeding organizations are selecting animals and exchanging germplasm across various environments. Ignoring genotype by environment interaction (G x E) may affect the efficiency of ... [more ▼]

Under globalization, breeding organizations are selecting animals and exchanging germplasm across various environments. Ignoring genotype by environment interaction (G x E) may affect the efficiency of breeding strategies and limit outcomes from cooperation between breeding programs. Quantifying the effectiveness of indirect selection and effects of G x E for different breeds is therefore necessary. The objective of this thesis was to evaluate the magnitude of G x E for milk yield using Luxembourg and Tunisian Holstein populations. In fact, these two countries rely considerably on importation of superior genes from diverse origins for their breeding programs. This study needed records on both the genotype and the environment. In the first part of this thesis, genetic ties between the two populations were studied. Additive relationships and genetic similarity were important and genetic links have been strengthened with time which allowed the analysis of the phenotypic expression of daughters of common sires under each of these tow production environments. In the second part, genetic parameters for production traits of Tunisian Holsteins were estimated by a test-day random regression model (RRTD). Heritability estimates for 305-d milk, fat and protein yields were low to moderate (0.12 to 0.18) suspecting difficulties of high-producing cows to express their potential under limiting production conditions. In the third part, G x E for milk yield and persistency were investigated using character state models, where milk yield in each country was considered as a separate trait, and where the country border delimitation was designed as an environmental character state. A RRTD sire model was applied and was extended to a RRTD animal model. Significant G x E was detected for milk yield and persistency by both models. Large differences in genetic and permanent environmental variances between the two countries were observed. Genetic correlations for 305-d milk yield and persistency between Luxembourg and Tunisian Holsteins were 0.50 and 0.43 (sire model) and 0.60 and 0.36 (animal model). Moreover, low rank correlations obtained between estimated breeding values of common sires translate a significant re-ranking between the two environments. At the end of this thesis, a herd management (HM) parameter reflecting feeding and management intensity was defined. Three HM levels were identified in each country and G x E was investigated within- and across-environments. Significant G x E was detected between the Tunisian HM levels, whereas, only heterogeneous genetic variance for milk yield with limited re-ranking of sires across the three Luxembourg environments was observed. Overall, this thesis shows that under constraining environmental effects, selection for adaptive traits among economically valuable traits under their specific conditions is needed for low-input systems. When satisfactory feeding resources, management and husbandry practices are available, high degree environmental sensitivity is desired and the use of a high yielding breed may be encouraged. [less ▲]

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See detailLes stratégies e-commerce des entreprises face au cadre juridique: une analyse exploratoire de la prise de risque dans le contexte belge
Lisein, Olivier ULg

Doctoral thesis (2009)

Après le scepticisme engendré par l’éclatement de la bulle Internet et la brutale chute de certaines "dot com", on assiste ces dernières années à une réelle "e-volution" des relations d’affaires et à un ... [more ▼]

Après le scepticisme engendré par l’éclatement de la bulle Internet et la brutale chute de certaines "dot com", on assiste ces dernières années à une réelle "e-volution" des relations d’affaires et à un essor particulièrement marqué du commerce électronique, lesquels confèrent désormais à Internet un statut d’espace marchand incontournable. Cet enthousiasme se heurte cependant au manque de confiance exprimé par certains acteurs économiques envers les échanges de type e-business/e-commerce, soulevant de façon sous-jacente la problématique de la régulation des transactions électroniques ainsi que de ses effets sur le comportement des consommateurs et le succès des stratégies e-commerce des entreprises. Alors que de nombreuses études abordent ces enjeux relatifs au commerce électronique sous un angle monodisciplinaire, notre propos s’inscrit dans une optique davantage transversale, basée sur l’interconnexion de différents courants théoriques issus des sciences de gestion et du droit. Prenant appui sur une vingtaine d’études de cas, issues de quatre secteurs d’activités contrastés en matière d’utilisation des technologies numériques, notre démarche réflexive interroge le positionnement stratégique des dirigeants d’entreprises envers l’e-commerce ainsi que l’influence que revêt à cet égard un nombre déterminé de facteurs : la nature des transactions opérées, la stratégie d’affaires poursuivie et le cadre juridique qui régit les relations commerciales établies par voie électronique. Articulées autour de la question de la prise de risque, que nous appréhendons essentiellement au travers du prisme de l’opportunisme possible des partenaires d’affaires, ces différentes variables permettent de mettre en évidence et de justifier des approches contrastées du commerce électronique de la part des responsables d’entreprises, en ce qui concerne aussi bien l’étendue des services proposés en ligne, le degré de numérisation du processus transactionnel ou encore la posture privilégiée par rapport aux dispositions réglementaires et aux éventuels mécanismes de protection à mobiliser. [less ▲]

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See detailContribution à l’élaboration d’un espace commun de représentation pour l’analyse morpho-fonctionnelle du membre supérieur : application à l’articulation glénohumérale
Schwartz, Cédric ULg

Doctoral thesis (2009)

Locomotor disorders comprehension is limited by the absence of dynamic 3D imaging technology. 3D imagers give access to accurate but static information about bones morphology. On the other hand, motion ... [more ▼]

Locomotor disorders comprehension is limited by the absence of dynamic 3D imaging technology. 3D imagers give access to accurate but static information about bones morphology. On the other hand, motion analysis systems provide dynamic measures. However, these measures may be distorted by the presence of soft tissues between the bones and the skin surface. First, we study a new method for correcting soft tissues artifacts when using external markers for motion estimation. This method is based on a surfacic approach and aims to follow the deformation created by the scapula on the skin surface. A robust registration algorithm, called IMCP, is used. This algorithm, developed in previous works, has been modified and adapted to be more specific to the study context: motion analysis using external markers. The improvements concern post-processing so as to make the most of the information mutualization properties of the IMCP, a way to take into account the influence of the edges of the markers clusters, and finally the optimization of the processing time thanks to multi-threading developments. In a second time, a specific MRI protocol is developed in order to allow morpho-functional analysis. Moreover, articular coherence indicators are proposed for the glenohumeral joint. These indicators are adapted to the case of errors in motion estimation. The results show that the use of a markers cluster covering all the scapula do not allow to follow the scapula print at skin surface. Thanks to simulation studies, two hypotheses are proposed to explain these results: the noise created by the soft tissues is too significant, and / or the available skin resolution is not sufficient. The relevance of proposing markerless analysis is so emphasized. Our morpho-functional study on the glenohumeral joint shows the significant influence of the motion analysis protocol on joint coherence during bones animation. The placement of the markers on the scapula and on the humerus as well as the choice of the motion estimation algorithm have a large influence on the bony structures motion estimation. [less ▲]

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See detailEnvironmental Changes and Migration Flows. Normative Frameworks and Policy Responses.
Gemenne, François ULg

Doctoral thesis (2009)

Depuis quelques années, d’importants déplacements de populations sont régulièrement annoncés comme l’une des conséquences les plus dramatiques du changement climatique. Plusieurs dizaines de ... [more ▼]

Depuis quelques années, d’importants déplacements de populations sont régulièrement annoncés comme l’une des conséquences les plus dramatiques du changement climatique. Plusieurs dizaines de millions de personnes pourraient ainsi être contraintes à l’exil en raison des impacts du réchauffement global, selon les estimations les plus alarmistes. Ces prédictions, pourtant, relèvent d’une logique largement déterministe, qui simplifie souvent la relation entre dégradation environnementale et migrations à une causalité directe, et néglige l’importance des cadres normatifs. Cette thèse prend le contre-pied de l’approche déterministe dominante, et soutient que l’ampleur et la nature de ces flux migratoires ne dépendent pas uniquement des impacts du changement climatique, mais également – et surtout – des politiques qui seront mises en place pour limiter ces impacts et encadrer ces migrations. Elle adopte une posture constructiviste, et s’interroge sur la manière dont les réponses politiques apportées jusqu’ici aux mouvements de population provoqués par des dégradations environnementales influencent la conceptualisation du phénomène de ‘migrations environnementales’. Afin d’analyser le processus politique de mise en place de cadres normatifs et de réponses politiques en place au niveau international, la thèse utilise le modèle théorique de l’Advocacy Coalition Framework (ACF), mis au point par Sabatier et Jenkins-Smith. Dans un premier temps, la thèse analyse l’émergence du concept de ‘migrations environnementales’ dans la littérature et à l’agenda politique. La littérature sur le sujet est traversée par une opposition entre deux courants de pensée, que j’ai qualifiés respectivement de ‘sceptique’ et d’ ‘alarmiste’. Le courant sceptique, composé essentiellement de spécialistes des migrations, soutient que toute migration est multi-causale, et que l’environnement n’est pas un facteur migratoire plus déterminant qu’un autre. Ainsi, les sceptiques estiment que le concept de ‘migration environnementale’, considéré comme un type spécifique de migration, n’a guère de sens. A l’inverse, les alarmistes, qui sont essentiellement des spécialistes de l’environnement, affirment que les dégradations de l’environnement constituent un facteur croissant de migrations forcées, qui ont déjà commencé. Ces deux courants de pensée, qui trouvent leur origine dans un fossé disciplinaire, peuvent être analysés comme de véritables coalitions, qui pénètrent le processus politique. Le rôle des chercheurs dans la définition des politiques publiques est dès lors mis en avant, et la thèse émet l’hypothèse que cette opposition entre ‘alarmistes’ et ‘sceptiques’ a dépassé le champ académique pour traverser également le champ politique. La thèse entreprend alors de décrire et d’analyser le développement de normes et de politiques s’appliquant aux déplacements de populations liés à des dégradations de l’environnement dans deux sphères politiques distinctes : les politiques environnementales d’une part, et migratoires d’autre part. Dans les politiques environnementales, la thèse examine en particulier la gestion des catastrophes naturelles au niveau international, et les questions d’adaptation dans les négociations sur un nouveau traité international sur le changement climatique. Le domaine de la gestion des catastrophes naturelles s’est considérablement transformé au cours des dernières, et les personnes déplacées par les catastrophes sont au centre de plusieurs débats, ateliers et recommandations. Pour autant, ce sont négociations sur le changement climatique qui sont devenues, au fil des ans, le réceptacle premier des discussions et revendications sur les ‘migrations climatiques’. Les politiques migratoires, par contre, ont évolué dans un sens très différent. Le régime international de l’asile n’a guère évolué depuis la Convention de Genève de 1951 et son Protocole additionnel de 1967, et n’a guère pris en charge les nouvelles configurations des migrations forcées dans le monde, comme l’importance croissante aux dégradations de l’environnement. Les politiques d’asile et de mobilité n’ont pas non plus véritablement intégré la question, se cantonnant à des formes de protection complémentaires et/ou non contraignantes, dont pourraient se prévaloir ceux qui sont déplacés par une catastrophe naturelle. La thèse cherche à expliquer cette évolution différente par les différentes coalitions qui dominent ces sphères politique : les politiques migratoires sont dominées par les sceptiques, tandis que les politiques environnementales sont dominées par les alarmistes. Depuis le milieu des années 2000, les alarmistes dominent les débats sur les migrations environnementales, et ces débats se sont dès lors déplacés dans la sphère des politiques environnementales, et plus particulièrement dans celles des négociations sur le futur régime climatique. L’apparente réconciliation récente entre les deux coalitions marquent en réalité un glissement vers le terrain des politiques environnementales. Ce glissement révèle que le phénomène de ‘migrations environnementales’ reste largement conceptualisé de manière déterministe, et comme une migration forcée, inéluctable conséquence de l’échec de l’adaptation. Or, des illustrations empiriques, provenant de terrains effectués à La Nouvelle-Orléans après l’ouragan Katrina et à l’archipel de Tuvalu menacé par la montée des eaux, démontrent que cette conceptualisation ne correspond pas à la réalité des flux migratoires liés à des changements de l’environnement. La thèse souligne donc le caractère socialement construit des migrations environnementales, et l’importance du rôle joué par les politiques publiques. [less ▲]

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See detailBiogeochemical study of coccolithophorid blooms in the context of climate change
Harlay, Jérôme ULg

Doctoral thesis (2009)

Coccolithophores are unicellular microscopic algae (Haptophyta) surrounded by calcium carbonate plates that are produced during their life cycle. These species, whose contemporary contributor is Emiliania ... [more ▼]

Coccolithophores are unicellular microscopic algae (Haptophyta) surrounded by calcium carbonate plates that are produced during their life cycle. These species, whose contemporary contributor is Emiliania huxleyi, are mainly found in the sub-polar and temperate oceans, where they produce huge blooms visible from space. Coccolithophores are sensitive to ocean acidification that results from the ongoing accumulation of anthropogenic carbon dioxide (CO2) in the atmosphere. The response of these organisms to global change appears to be related to the reduction of their ability to produce calcium carbonate at the cellular level. At the community levels, one anticipates changes in the carbon fluxes associated to their blooms as calcification is reduced. However, the consequences of such environmental changes on this species are speculative and require improvements in the description of the mechanisms controlling the organic and inorganic carbon production and export. The first aspect of this work was to study the response of these organisms to artificially modified CO2 concentrations representative of the conditions occurring in the past (glacial) and those expected by the end of the century (2100). Two different levels were examined: the continuous monospecific cultures (chemostats) allowed us to work at the cellular level while the mesocosms gave light to the mechanisms taking place in an isolated fraction of the natural community. The second aspect of this work consisted of field studies carried out during four cruises (2002, 2003, 2004 and 2006) in the northern Bay of Biscay, where the occurrence of E. huxleyi blooms were observed in late spring. I describe the vertical profiles of biogeochemical variables (nutrients, chlorophyll-a, dissolved inorganic carbon chemistry, particulate carbon, transparent exopolymer particles (TEP)) and study processes such as primary production, calcification and bacterial production. The properties of these blooms are compared with those reported in the literature and enriched with original measurements such as the abundance and concentration of TEP that could play an important role in carbon export to the deep ocean, modifying the properties of the settling ballasted aggregates. [less ▲]

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See detailDépistage Néonatal de la Drépanocytose: Nouvelles Méthodologies
BOEMER, François ULg

Doctoral thesis (2009)

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See detailMéthode de Perturbation pour la Modélisation par Éléments Finis des Systèmes Électrostatiques en Mouvement - Application aux MEMS Électrostatiques
Boutaayamou, Mohamed ULg

Doctoral thesis (2009)

La modélisation par éléments finis des conducteurs en mouvement nécessite généralement des calculs successifs et le remalliage de certaines régions. Une modélisation 3D de géométries complexes par les ... [more ▼]

La modélisation par éléments finis des conducteurs en mouvement nécessite généralement des calculs successifs et le remalliage de certaines régions. Une modélisation 3D de géométries complexes par les techniques classiques nécessite dès lors de gros efforts en terme de temps de calcul. Dans cette thèse, une méthode originale basée sur une approche par sous-problèmes, appelée méthode de perturbation, a été développée. Utilisant la méthode des éléments finis, cette technique consiste à subdiviser un problème entier en sous-problèmes. La complexité du problème initial est par conséquent diminuée en ne se concentrant que sur les zones les plus pertinentes. Appliquée aux systèmes en mouvement, la méthode de perturbation permet d'exploiter les résolutions antérieures au lieu d'effectuer un nouveau calcul pour chaque position. L'analyse par la méthode de perturbation des microsystèmes électromécaniques (MEMS) électrostatiques comprenant des parties en déplacement ou en déformation est en outre considérée dans ce travail. Il est notamment question de démontrer l'implication naturelle de cette approche pour des simulations plus efficaces et plus précises des MEMS électrostatiques. [less ▲]

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See detailContribution à l'étude de la pathologie pleurale maligne.
DUYSINX, Bernard ULg

Doctoral thesis (2009)

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See detailEtude moléculaire des short-chain isoprényle diphosphate synthases chez les pucerons : Evaluation de leur potentiel d’utilisation comme cible de nouveaux bio-insecticides
Vandermoten, Sophie ULg

Doctoral thesis (2009)

Les pucerons sont considérés comme des ravageurs majeurs, d’une part en raison de leur action directe sur le végétal, mais également en tant que vecteurs de nombreux virus phytopathogènes. A l’heure ... [more ▼]

Les pucerons sont considérés comme des ravageurs majeurs, d’une part en raison de leur action directe sur le végétal, mais également en tant que vecteurs de nombreux virus phytopathogènes. A l’heure actuelle, la lutte contre certaines espèces de pucerons, au moyen d’insecticides de synthèse, devient extrêmement difficile en raison de l’apparition de populations résistantes. Le développement de nouveaux produits antiparasitaires, visant spécifiquement les pucerons, devient, par conséquent, hautement souhaitable. Dans ce contexte, nous avons choisi de nous intéresser aux enzymes de la famille des « short-chain » isoprényle diphosphate synthases (scIPPS). Ces enzymes constituent une classe de prényltransférases impliquées dans le métabolisme des isoprénoïdes. Cette classe comprend la géranyle diphosphate synthase, la farnésyle diphosphate synthase et la géranylgéranyle diphosphate synthase qui respectivement synthétise le géranyle diphosphate (GPP, C10), le farnésyle diphosphate (FPP, C15), et le géranylgéranyle diphosphate (GGPP, C20). Nous avons cloné chez le puceron un nouveau type de scIPPS. Contrairement à d'autres scIPPS connues, l’enzyme recombinante du puceron affiche une activité bifonctionnelle ; cette dernière étant capable de synthétiser à la fois le GPP, le précurseur commun des monoterpènes, mais également le FPP, le précurseur des sesquiterpènes. Chez les pucerons, ces deux précurseurs sont supposés jouer un rôle clé dans la biosynthèse de l'hormone juvénile et des phéromones d'alarme et sexuelle. Dans le but de fournir une explication structurelle à la bifonctionnalité observée chez la GPP/FPP synthase de puceron, nous avons entrepris de résoudre sa structure tridimensionnelle en se basant sur les structures cristallographiques du poulet. Plusieurs mutants ont été ensuite conçus et caractérisés. [less ▲]

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See detailModélisation et résolution du problème de contact mécanique et son application dans un contexte multiphysique
Bussetta, Philippe ULg

Doctoral thesis (2009)

The mechanical contact is the problem of solids mechanics that presents the most difficult nonlinearity. The good resolution of the frictional contact problem is disrupted by the noniineaxity and the non ... [more ▼]

The mechanical contact is the problem of solids mechanics that presents the most difficult nonlinearity. The good resolution of the frictional contact problem is disrupted by the noniineaxity and the non differentiability of the contact's equations (stick/unstick and the initiation of sliding). Until now, no method could be used to resolve all contact problems. This work is focused on the methods of calculation of the mechanical contact in a more general way. It could be separated in two parts. The first one concerns the creation of the systems of equations and the algorithm of resolution. The methods more used are the Penalty Method and Lagrangian Augmented Method. Although these methods are simple, they are very difficult to use because the choice of the value of penalty coefficients (normal and tangential). For this reason, a new method, the "Lagrangian Augmented Adapted Method" is proposed. This new method is based on the Lagrangian Augmented Method and on the adaptation of the penalty coefficients. With it, the user does not need to choose the value of penalty coefficients. In addition, this method has the speed of the Penalty Method and the reliability of the Lagrangian Augmented Method. The second part of this work deals with the calculation of the mechanical contact under a spatial disctretization. The method more used is the "Point-Surface" Method. The contact is calculated between every point of one surface and the other surface. This method has many limits, as the representativeness and the regularity of the solution when the boundaries are deformable and irregular. Many researches are done on another method, the "Surface-Surface" Method based on the Mortar Element Method. The mechanical contact is calculated on each node of one surface in function of the two surfaces. With this method the solution is more regular and reliable. But the calculation of the mechanical contact is more difficult, so it can not be used to the three dimensional problems. An adaptation of this method has been proposed to the two and three dimensional problems. All these methods are tested on some academics and industrials multi-physical problems. [less ▲]

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See detailSolute transport modelling at the groundwater body scale: Nitrate trends assessment in the Geer basin (Belgium)
Orban, Philippe ULg

Doctoral thesis (2009)

Water resources management is now recognized as a multidisciplinary task that has to be performed in an integrated way, within the natural boundaries of the hydrological basin or of the aquifers. Policy ... [more ▼]

Water resources management is now recognized as a multidisciplinary task that has to be performed in an integrated way, within the natural boundaries of the hydrological basin or of the aquifers. Policy makers and water managers express a need to have tools able at this regional scale to help in the management of the water resources. Until now, few methodologies and tools were available to assess and model the fate of diffuse contaminants in groundwater at the regional scale. In this context, the objective of this research was to develop a pragmatic tool to assess and to model groundwater flow and solute transport at the regional scale. A general methodology including the acquisition and the management of data and a new flexible numerical approach was developed. This numerical approach called Hybrid Finite Element Mixing Cell (HFEMC) was implemented in the SUFT3D simulator developed by the Hydrogeology Group of the University of Liège. A first application of this methodology was performed on the Geer basin. The chalk aquifer of the Geer basin is an important resource of groundwater for the city of Liège and its suburbs. The quality of this groundwater resource is threatened by diffuse nitrate contamination mostly resulting from agricultural practices. New field investigations were performed in the basin to better understand the spatial distribution of the nitrate contamination. Samples were taken for environmental tracers (tritium, CFC’s and SF6) analysis. The spatial distribution of environmental tracers concentrations is in concordance with the spatial distribution of nitrates. This allows proposing a coherent interpretative schema of the groundwater flow and solute transport at the regional scale. These new data and the results of a statistical nitrate trend analysis were used to calibrate the groundwater model developed with the HFEMC approach. This groundwater flow and solute transport model was used to forecast the evolution of nitrate concentrations in groundwater under a realistic scenario of nitrate input for the period 2008-2058. According to the modelling results, upward nitrate trends observed in the basin will not be reversed for 2015 as prescribed by the EU Water Framework Directive. The regional scale groundwater solute transport model was subsequently used to compute nitrate concentrations in groundwater under different scenarios of nitrate input to feed a socio-economic analysis performed by BRGM. These computed concentrations were used to assess the benefit, for the users, linked to the reduction of contamination resulting from the changes in nitrate input. These benefits were compared to the costs associated to the implementation of the considered agri-environmental schemes that allow reducing the nitrate input to groundwater. [less ▲]

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See detailGeometry and Symmetries in Coordination Control
Sarlette, Alain ULg

Doctoral thesis (2009)

The present dissertation studies specific issues related to the coordination of a set of “agents” evolving on a nonlinear manifold, more particularly a homogeneous manifold or a Lie group. The viewpoint is ... [more ▼]

The present dissertation studies specific issues related to the coordination of a set of “agents” evolving on a nonlinear manifold, more particularly a homogeneous manifold or a Lie group. The viewpoint is somewhere between control algorithm design and system analysis, as algorithms are derived from simple principles — often retrieving existing models — to highlight specific behaviors. With a fair amount of approximation, the objective of the dissertation can be summarized by the following question: Given a swarm of identical agents evolving on a nonlinear, nonconvex configuration space with high symmetry, how can you define specific collective behavior, and how can you design individual agent control laws to get a collective behavior, without introducing hierarchy nor external reference points that would break the symmetry of the configuration space? Maintaining the basic symmetries of the coordination problem lies at the heart of the contributions. The main focus is on the global geometric invariance of the configuration space. This contrasts with most existing work on coordination, where either the agents evolve on vector spaces — which, to some extent, can cover local behavior on manifolds — or coordination is coupled to external reference tracking such that the reference can serve as a beacon around which the geometry is distorted towards vector space-like properties. A second, more standard symmetry is to treat all agents identically. Another basic ingredient of the coordination problem that has important implications in this dissertation is the reduced agent interconnectivity: each agent only gets information from a limited set of other agents, which can be varying. In order to focus on issues related to geometry / symmetry and reduced interconnectivity, individual agent dynamics are drastically simplified to simple integrators. This is justified at a “planning” level. Making the step towards realistic dynamics is illustrated for the specific case of rigid body attitude synchronization. The main contributions of this dissertation are I. an extensive study of synchronization on the circle, (a) highlighting difficulties encountered for coordination and (b) proposing simple strategies to overcome these difficulties; II. (a) a geometric definition and related control law for “consensus” configurations on compact homogeneous manifolds, of which synchronization — all agents at the same point — is a special case, and (b) control laws to (almost) globally reach synchronization and “balancing”, its opposite, under general interconnectivity conditions; III. several propositions for rigid body attitude synchronization under mechanical dynamics; IV. a geometric framework for “coordinated motion” on Lie groups, (a) giving a geometric definition of coordinated motion and investigating its implications, and (b) providing systematic methods to design control laws for coordinated motion. Examples treated for illustration of the theoretical concepts are the circle S^1 (sometimes the sphere S^n ), the rotation group SO(n), the rigid-body motion groups SE(2) and SE(3) and the Grassmann manifolds Grass(p,n). The developments in this dissertation remain at a rather theoretical level; potential applications are briefly discussed. [less ▲]

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See detailSOURCES DE VARIATION PHÉNOTYPIQUE DES TRAITS D’HISTOIRE DE VIE D’UNE ESPÈCE INVASIVE, SENECIO INAEQUIDENS DC. (ASTERACEAE).
Monty, Arnaud ULg

Doctoral thesis (2009)

L’importance des différentes sources de variation phénotypique que sont l’adaptation, la plasticité phénotypique, les effets maternels environnementaux, le niveau de ploïdie et la dérive génétique, a été ... [more ▼]

L’importance des différentes sources de variation phénotypique que sont l’adaptation, la plasticité phénotypique, les effets maternels environnementaux, le niveau de ploïdie et la dérive génétique, a été analysée pour différents traits d’histoire de vie, au sein de l’aire colonisée par une espèce végétale invasive. A cette fin, plusieurs expériences en jardins communs ont été installées, dont deux en transplantations réciproques. Les populations considérées étaient localisées en Belgique, en France, ainsi que dans l’aire d’indigénat de l’espèce. Senecio inaequidens DC. (Asteraceae), l’espèce étudiée dans ce travail, est une plante d’origine africaine accidentellement introduite en Europe par le commerce lainier, vers la fin du 19ème siècle. Dans son aire d’indigénat, elle présente deux niveaux de ploïdie, diploïde et tétraploïde. Seuls des plants tétraploïdes sont recensés en Europe. L’espèce présente un historique de colonisation particulier, bien documenté, qui en fait un modèle idéal pour les études évolutives. Les traits d’histoire de vie considérés ont été scindés en deux groupes. Les premiers concernaient la germination, la croissance et la reproduction sexuée. Les sources de variation phénotypique dans ces traits ont été principalement analysées en relation avec les variations climatiques dans l’aire d’invasion, le long de gradients d’altitude, ainsi qu’en relation avec le niveau de ploïdie et l’aire d’origine (aire d’indigénat vs aire d’invasion). Le deuxième groupe de traits considérés concernaient les capacités de dispersion de l’espèce. Celles-ci ont été modélisées. La variabilité phénotypique dans ces traits a ensuite été analysée, parmi les populations françaises, en relation avec l’éloignement depuis le site de première introduction. Les résultats ont montré des différences entre les cytotypes de l’espèce, principalement dans les capacités de survie hivernale. Le long des gradients d’altitude, les populations de S. inaequidens présentaient des différenciations phénotypiques de type clinal, dans les traits de croissance. Ces différenciations étaient d’origine génétique, même si les effets maternels environnementaux sont apparus comme des sources non-négligeables de variation phénotypique dans les zones à climat rigoureux. Parmi les traits liés à la dispersion, le plume loading était le mieux corrélé aux capacités de dispersion par le vent. Des différenciations clinales ont été détectées dans les traits de dispersion, en jardin commun, mais n’ont pas été vérifiées en populations naturelles. [less ▲]

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See detailCrucial role of reversible phosphorylation in the mechanisms governing the biological functions of class IIa Histone Deacetylases
Martin, Maud ULg

Doctoral thesis (2009)

Regulation of class IIa histone deacetylases (HDACs) phosphorylation is crucial because it provides the opportunity to control important developmental processes associated with these key enzymes. Indeed ... [more ▼]

Regulation of class IIa histone deacetylases (HDACs) phosphorylation is crucial because it provides the opportunity to control important developmental processes associated with these key enzymes. Indeed, the transcriptional repressor activity of class IIa HDAC is controlled via their phosphorylation-dependent nucleo-cytoplasmic shuttling. While a lot of efforts have been directed towards the identification of the inactivating kinases that phosphorylate class IIa HDACs, the identity of the antagonist phosphatase remained an open question. During this work, we found that protein phosphatase 2A (PP2A) is responsible for dephosphorylating the class IIa HDACs member HDAC7, thereby regulating its subcellular localization and repressor activity. In order to validate our model, functional consequences of these findings was illustrated during the two main biological processes involving HDAC7, i.e. T-cells apoptosis during negative selection and endothelial cells angiogenic activities during vascular network formation. Cellular PP2A represents a large population of trimeric holoenzymes containing a variable regulatory subunit, whose identity has a crucial role in determining the specificity of PP2A catalytic activity. In an effort to characterize the regulation of HDAC7 dephopshorylation, we identified the relevant PP2A holoenzyme regulating HDAC7 function during vasculogenesis and we found that, among diverse regulatory subunit isoforms, PP2A-Bα uniquely regulates endothelial cell angiogenic properties. PP2A-Bα silencing using small interfering RNAs results in a significant inhibition of endothelial cell tube formation and migration. These results establish PP2A, and more precisely the Bα containg PP2A holoenzyme, as an essential element in the regulation of the class IIa HDACs HDAC7 and unravel a first developmental function for the PP2A regulatory subunit Bα in the genesis of blood vessels. [less ▲]

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See detailAgronomical and molecular factors influencing bananas (Musa acuminata, AAA, cv ‘Grande-Naine’) susceptibility to crown rot disease
Lassois, Ludivine ULg

Doctoral thesis (2009)

Crown rot affects export bananas in all producing countries and is considered to be one of the main export banana post-harvest disease. Variations are observed in the expression of crown rot symptoms. An ... [more ▼]

Crown rot affects export bananas in all producing countries and is considered to be one of the main export banana post-harvest disease. Variations are observed in the expression of crown rot symptoms. An original approach of the disease is proposed and consists on presenting the fruit quality potential at harvest as a key factor in crown rot development. This potential develops during growth of bananas in the field and depends on a physiological and a parasitical component. The physiological component refers here to the level of fruit susceptibility to crown rot and reflects the physiological state of the fruit. The aim of this study was to clarify the role of the fruit physiological component at harvest in the post-harvest crown rot development. It appears that the fruit physiological component at harvest greatly influence the postharvest disease development and thus the fruit susceptibility. Seasonal variations in disease severity were shown in two production area and are related to a variation of the fruit physiological component. In Guadeloupian conditions, the internal necrotic surface of the crown was nearly multiplied by 4 during 11 successive weeks. Two pre-harvest factors that could influence the fruit physiological component by modifying their susceptibility to crown rot, were identified: (i) hand position on the bunch and (ii) source-sink ratio of the banana plant (hand considered as sink and leaves as source). It was shown that within a bunch, there is a gradient of susceptibility to crown rot (r= -0.95), the hands initiated first (the upper ones) being more susceptible than those initiated last (the lower ones). These results also confirmed that source-sink ratio changes have a significant effect on fruit morphology and demonstrated that there is also an effect on fruit susceptibility to crown rot disease. When the sink is decreased by artificial removal of many hands, the level of fruit susceptibility to crown rot decreases. However, the molecular mechanisms underlying these quantitative host-pathogen relationships were still unknown. A study was designed to compare gene expression, by cDNA-AFLP, between crowns of bananas showing a high susceptibility (S+) and crowns of bananas showing a low susceptibility (S-) to Colletotrichum musae responsible for crown rot disease. This comparison was performed at two situation time: (i) between crowns (S+ and S-) collected one hour before infection and (ii) between crowns (S+ and S-) collected 13 days after infection. Genes implied in signaling pathway and proteolytic machinery were identified. It also appears that a cellulose synthase, a CAF1 gene, 2 glycolipid transfer protein and a dopamine-β-monooxygenase were differently expressed between bananas showing different levels of susceptibility. This is the first study of the characterization of the banana physiological component at harvest which influences the crown rot post-harvest disease development. In addition, to our knowledge, this work is the first to address both pre- and post-infection gene expression with the same host-pathogen combination and different susceptibility levels. [less ▲]

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See detailAlgebraic approach to modal extensions of Łukasiewicz logics
Teheux, Bruno ULg

Doctoral thesis (2009)

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See detailEtude du rôle des macrophages interstitiels dans l'allergie des voies respiratoires
Bedoret, Denis ULg

Doctoral thesis (2009)

Respiratory mucosal surfaces are constantly exposed to a broad range of non-pathogenic environmental antigens. In the absence of proinflammatory signals, inhalation of harmless antigens results in ... [more ▼]

Respiratory mucosal surfaces are constantly exposed to a broad range of non-pathogenic environmental antigens. In the absence of proinflammatory signals, inhalation of harmless antigens results in immunological tolerance. Indeed, lung dendritic cells stimulate the development of antigen-specific regulatory T cells. Nevertheless, epidemiological studies have shown that ambient air contains not only inert antigens but also immunostimulatory molecules of microbial origin. Of particular interest are endotoxins, a cell wall component of gram-negative bacteria that is ubiquitous in the environment. In spite of the fact that high levels of endotoxin exposure in early life protect against allergic sensitization, most evidence indicates that exposure to house-dust endotoxin is a significant risk factor for increased asthma prevalence and severity. When the respiratory tract is stimulated with airborne endotoxins, lung dendritic cells lose their tolerogenic properties and rather promote the development of an allergic response directed against concomitant aeroantigens. Although endotoxins are omnipresent in the environment and favour airway allergy, only a minority of people develops asthma. A unifying model reconciling these conflicting observations is still lacking. We report here that LPS-triggered airway allergy is tightly controlled by lung interstitial macrophages, a cell population that remains largely uncharacterized. Interstitial macrophages could be distinguished from alveolar macrophages by their unique capacity to inhibit lung dendritic cell maturation and migration upon LPS stimulation, thereby preventing sensitization to concomitant inhaled antigens. We furthermore demonstrated that functional paralysis of LPS-stimulated dendritic cells involves interleukin-10 production by interstitial macrophages. Finally, we demonstrate that specific in vivo elimination of interstitial macrophages leads to overt asthmatic reactions to innocuous airborne antigens inhaled along with low LPS doses. Our study thus reveals a crucial role for interstitial macrophages in maintaining immune homeostasis in the respiratory tract and provides an explanation for the paradox that airborne LPS has the ability to promote the induction of Th2 responses by lung dendritic cells but does not provoke airway allergy under normal conditions. In the presence of LPS, interstitial macrophages, but not alveolar macrophages, break the link between innate and adaptive immunity, allowing harmless inhaled antigens to escape from T cell-dependent responses. [less ▲]

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See detailLes matières colorantes au début du Paléolithique supérieur : sources, transformations et fonctions
Salomon, Hélène ULg

Doctoral thesis (2009)

Abstract : Despite an increasing number of studies, colouring materials are still poorly understood among excavation remains. Their attraction lies in their capacity to bring to light diverse and complex ... [more ▼]

Abstract : Despite an increasing number of studies, colouring materials are still poorly understood among excavation remains. Their attraction lies in their capacity to bring to light diverse and complex skills, but also in their intense colouring power and their contrasting colours : red and black, which still possess a symbolic value. These highly symbolic materials may, therefore, highlight the “conceptual” practices of prehistoric men and give access to their symbolic world and thought. In such a particular context as the transition between the Middle and the Upper Palaeolithic, these remains, which are very abundant in most excavations, offer the possibility, through analysis, to get an exceptional insight into the way of life of the last Neanderthals. The Châtelperronian site of the “Grotte du Renne”, in Arcy-sur-Cure (Yonne), is a landmark. It was excavated beween 1949 and 1963 by André Leroi-Gourhan : Numerous colouring materials were discovered there, and Leroi-Gourhan developed theories about their transformation and uses which so far have not been tested, and have remained unchallenged.Since their discovery, the assumption is that those minerals were heated in a controlled way, in order to modify their colour. It is indeed well-known that heat transforms yellow materials (iron hydroxides) in orange, red or purple materials (iron oxides). From this hypothesis originates the theory according to which Neanderthals exploited colouring materials as pigments for symbolic or even aesthetic purposes. But the theory has so far never been proved true. Our study combines several sets of data, obtained from different methods. Physico-chemical and petrological analyses were carried out on the colouring materials. These data were related to their location on the site, in association with exceptionally well preserved “hut” structures. Furthermore, a series of experimentations, aimed to characterize powders obtained via different methods (grinding and crushing on the one hand, abrasion on the other hand). The comparison of all these data enabled us to identify the various technical choices which informed the supply in colouring minerals in all the Châtelperronian levels of the Grotte du Renne. It was thus possible to demonstrate that none of these materials, either red or black, was heated before being used, contrary to what had been assumed so far. The supply in colouring materials was as carefully organised as for other materials (flint, for example) ; they were collected in geological formations occasionally showing on the surface, at more than 10 km from the cave. The exploitation of these geological sites did not vary during the whole Châtelperronian period, and privileged materials which can easily be ground into powder. Part of their supply was ground coarsely in order to cover large surface areas (soils or hides) as preservative or to clean them up. The remaining materials were destined to more meticulous activities, which required a fine, regular, and highly-colouring powder. In this latter case, the Neanderthals of the Grotte du Renne used those products when working on bone materials (bone or mammoth ivory), and used them also for their sheer colour. The set of colouring minerals from the Grotte du Renne reveals Neanderthals’ in-depth knowledge of materials ; they understood perfectly well their properties and qualities, and used them extensively, so that the Châtelperronian site must have been a literally dazzling sight, all red and black. The “chaîne opératoire” which transpires from our analysis shows very sophisticated techniques, and an advanced “technological” knowledge. They are witness to surprising capacities and a highly-evolved pattern of thought. [less ▲]

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See detailMapping Athletic Performance Related Genes in the Equine Genome and a Genome Scan for Superior Athletic Performance in the Thoroughbred
Durkin, Keith ULg

Doctoral thesis (2009)

The primary goal of the Thoroughbred industry is to breed and train superior equine athletes capable of excelling on the racetrack. To date, research into the genetic underpinnings of athletic ability has ... [more ▼]

The primary goal of the Thoroughbred industry is to breed and train superior equine athletes capable of excelling on the racetrack. To date, research into the genetic underpinnings of athletic ability has been limited in the horse. Advances in equine genomics and the genetics of athletic performance in humans have opened up the possibility of investigating this important trait in the Thoroughbred. Initially, 46 candidate genes associated with human athletic performance were mapped in the equine genome by radiation hybrid (RH) and fluorescent in situ hybridization (FISH) mapping. RH data and later the draft equine genomic sequence allowed us to identify microsatellites adjacent to these and other candidate genes (95 in total). Additional microsatellites were added to increase genome coverage, producing a final panel of 186 markers. All the potential markers were initially screened on a pool of DNA for 16 Thoroughbreds to ensure they were polymorphic. The panel was genotyped on 162 Thoroughbreds in total; Centimorgans (cM) between microsatellites were determined with CRI-MAP. The animal’s athletic ability was estimated using career winnings loge transformed to create a linear trait; unraced animals were treated as missing data. Linkage analysis was carried out using the MERLIN program, and association analysis was carried out using the QTDT program. Appropriate thresholds for statistical significance were determined by carrying out 1000 simulated genome scans based on the structure of the original data. LOD scores above 1.54 met the criteria of statistical significance (with a 5% chance of type I error). In the actual genome scan, the marker L12.2 had the highest observed LOD score of 1.16 and p-value of 0.01 and consequently was not significant; the association analysis also did not detect significant association with performance on the track. Given the complexity of the phenotype under investigation and the modest sample size, the lack of linkage/association was not unexpected. Nevertheless, this study has contributed to the RH and FISH maps of the equine genome. Additionally, the development of the genome scanning panel for this study has provided useful information on the most informative microsatellites for linkage or association studies in the Thoroughbred. [less ▲]

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See detailLES TRAITEMENTS ET LA PHARMACOGENETIQUE DES TRAITEMENTS ANTI-VIH-1
Cherrier, Thomas ULg

Doctoral thesis (2009)

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See detailÉtude de la modalité en néo-égyptien
Polis, Stéphane ULg

Doctoral thesis (2009)

Cette thèse constitue la première étude générale de la modalité en néo-égyptien. Le chapitre introductif (p. 5-43) est consacré [1] à la définition de ce premier état de langue de l’égyptien de la seconde ... [more ▼]

Cette thèse constitue la première étude générale de la modalité en néo-égyptien. Le chapitre introductif (p. 5-43) est consacré [1] à la définition de ce premier état de langue de l’égyptien de la seconde phase ; cette définition a permis la délimitation d’un corpus servant d’assise empirique à l’étude (la répartition du corpus en fonction de critères chronologiques et géographiques, de la nature du support et des "Textsorten" a donné la possibilité de pondérer et d’objectiver les analyses proposées pour chaque expression de la modalité). Ensuite, [2] un cadre théorique général pour l’étude de la langue est discuté. Le corps du travail se divise en trois parties consacrées respectivement : [1] à une définition générale de la notion de modalité (cela afin de déterminer les media expressifs qui relèvent de son étude en néo-égyptien) ainsi qu’à l’établissement d’un modèle sémantique à la fois économique, cohérent et correspondant aux données typologiques (p. 44-115) ; [2] à l’étude des modalités radicales (i.e. les modalités déontiques et bouliques en envisageant les relations qu’elles entretiennent avec le domaine axiologique ; p. 116-341) ; [3] à l’examen des modalités assertives (p. 342-446) : [a] analyse des formes de complémentation, en ce compris les liens entre intégration syntaxique, variation de l’assertivité et degré de manipulation, [b] étude de l’impact des auxiliaires d’énonciation sur le degré d’assertivité d’une proposition, [c] critique des théories existantes concernant les moyens expressifs du discours indirect en néo-égyptien. Les conclusions (p. 447-466) sont accompagnées de propositions prospectives devant permettre [1] de rendre le modèle défendu applicable à l’étude des complexes conditionnels, [2] d’intégrer la dimension énonciative dans l’analyse des relations interpersonnelles, [3] de proposer une approche globale des media expressifs de la causalité et de la finalité. [less ▲]

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See detailContribution to the Characterization of Scroll Machines in Compressor and Expander Modes
Lemort, Vincent ULg

Doctoral thesis (2008)

This thesis contributes to the knowledge and the characterization of scroll machines and their systems. It is based on experimental and modeling works carried out on: a) A hermetic scroll compressor used ... [more ▼]

This thesis contributes to the knowledge and the characterization of scroll machines and their systems. It is based on experimental and modeling works carried out on: a) A hermetic scroll compressor used inside an air-cooled water chiller. b) An oil-free open-drive scroll expander integrated into an Organic Rankine Cycle (ORC) power system. c) Open-drive scroll compressor and expander used in a Liquid Flooded Ericsson Cycle Cooler (LFEC). Such a system uses the liquid flooding of the compressor and of the expander to approach isothermal compression and expansion processes. New semi-empirical models of the scroll compressor and expander were proposed and existing models improved. A deterministic model of the scroll expander was established. The model associates a geometrical description of the machine with a thermodynamic description of the expansion process. This model was validated for the two expanders investigated experimentally. The model validation revealed that the performance of the expanders is mainly affected by the supply pressure drop and by the internal leakages. Using the validated model, parametric studies were carried out to investigate the variation of the performance of both expanders with modification of their design and with the operating parameters. The thesis also investigated the scroll machines from the point of view of their integration into thermal systems. A first experimental investigation was carried out on an air-cooled chiller. The scroll compressor semi-empirical model, with its parameters identified on the basis of published manufacturer data, was used as a refrigerant flow meter. The analysis of the experimental data allowed a better understanding of the chiller operation and a better identification of its model parameters (such as the fan and the hot gas bypass control models). A second experimental investigation was carried out on an ORC power system, working with R123. In order to select the most appropriate fluid, the performances achieved with four different fluids were compared by simulation. The experimental study confirmed that the scroll expander is a good candidate for an ORC system: the tested prototype presented a good performance (the maximum global isentropic effectiveness achieved was 68%). Using an ORC simulation model, parametric studies were carried out to investigate the effects of the expander characteristics and operating conditions on the cycle performance. The latter is mainly affected by the expander internal leakage and by the liquid subcooling at the condenser exhaust. A third experimental investigation was performed on a LFEC working with nitrogen as refrigerant and alkyl-benzene oil as flooding liquid. Experimental data was used to identify the parameters of the scroll compressor and expander semi-empirical models. Parametric studies were performed to identify the different factors affecting their performance. One of the undesirable features of the machines is the increase of the supply and exhaust pressure drops with the increase of oil quantity. [less ▲]

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See detailÉtude du vocabulaire de la vie familiale et sociale en Wallonie: approche géolinguistique et lexicologique
Baiwir, Esther ULg

Doctoral thesis (2008)

La thèse est concue comme un volume de l'Atlas Linguistique de la Wallonie (ALW), la plus grande et la plus ambitieuse œuvre de dialectologie en Wallonie. L'objet de la thèse est l'homme en tant qu'être ... [more ▼]

La thèse est concue comme un volume de l'Atlas Linguistique de la Wallonie (ALW), la plus grande et la plus ambitieuse œuvre de dialectologie en Wallonie. L'objet de la thèse est l'homme en tant qu'être social. C'est ainsi le vocabulaire de la famille et des interactions sociales qui est étudié. L'intérêt du sujet ne se limite donc pas uniquement au domaine linguistique, mais il a d'évidentes interactions avec l'ethnographie, l'histoire ou la sociologie. [less ▲]

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See detailBelgien im Nachkriegsdeutschland. Besatzung, Annäherung, Ausgleich (1944-1958)
Brüll, Christoph ULg

Doctoral thesis (2008)

Les relations belgo-allemandes ne constituent pas un champ de recherches souvent fréquenté par des chercheurs de part et d’autre de la frontière – à l’exception des deux occupations allemandes de la ... [more ▼]

Les relations belgo-allemandes ne constituent pas un champ de recherches souvent fréquenté par des chercheurs de part et d’autre de la frontière – à l’exception des deux occupations allemandes de la Belgique. Cette observation était encore plus nette pour la période après 1945. La thèse s’efforce de combiner une approche relativement classique de l’histoire diplomatique avec l’histoire sociale et celle des représentations et mentalités. En effet, l’analyse des plans belges pour l’après-guerre, des demandes de réparations territoriales et économiques et de l’occupation d’une partie de la zone d’occupation britannique par des troupes belges ne se fait pas seulement au niveau des ministères Affaires étrangères, mais également au niveau des principaux concernés : les soldats belges en Allemagne et la population frontalière. La présentation à différents niveaux de récit permet l’analyse des interactions entre la « grande politique » alliée et le quotidien des « concernés ». Les chapitres sur les années 1950 détaillent le rapprochement politique de la Belgique avec la jeune République Fédérale d’Allemagne devant un décor de guerre froide – rappelant la nécessité d’intégrer les Allemands dans le bloc de l’ « Ouest » – et des débuts de l’intégration européenne – discours dominant dans les justifications du rapprochement avec l’ancien ennemi. Dans ces pa-ges, c’est la représentation de l’ « autre » qui guide l’analyse. Le terminus ad quem était constitué par la ratification du traité bilatéral du 24 septembre 1956 par les deux parlements en 1958. Le travail évoque ici la question du prix de la rapide (comparée aux Pays-Bas ou à la France) réconciliation politique, notamment sur le plan de la société civile. Les relations belgo-allemandes après 1945 apparaissent ici surtout comme un processus d’apprentissage ayant pour objectif la volonté de ne plus commettre les mêmes erreurs que pen-dant l’entre-deux-guerres. [less ▲]

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See detailThérapie du mésothéliome pleural malin par l’utilisation du valproate, un inhibiteur de désacétylases
Vandermeers, Fabian ULg

Doctoral thesis (2008)

Le mésothéliome pleural est un cancer de la plèvre provoqué principalement par l’inhalation de fibres d’amiante. Nous avons émis l’hypothèse que la dérégulation de l’expression génique est un paramètre ... [more ▼]

Le mésothéliome pleural est un cancer de la plèvre provoqué principalement par l’inhalation de fibres d’amiante. Nous avons émis l’hypothèse que la dérégulation de l’expression génique est un paramètre important du développement de cette maladie. Or, les histones désacétylases (HDACs) peuvent jouer le rôle de répresseur transcriptionnel en modifiant la conformation de la chromatine. Dans ce contexte, nous avons étudié l’activité anticancéreuse du valproate, un inhibiteur d’HDAC, en combinaison avec différents types de traitements utilisés en chimiothérapie. Nous avons démontré l’effet synergique entre la chimiothérapie et le valproate dans des lignées cellulaires et dans des biopsies isolées à partir de patients. Nous avons étudié les processus impliqués dans l’apoptose et révélé l’implication des caspases, des espèces oxygéno-réactives et le rôle important de la protéine Bid. Nous avons ensuite réalisé une étude transcriptomique par microdamiers dans le but de mieux caractériser les mécanismes impliqués. Enfin, nous avons démontré l’efficacité du valproate dans un modèle préclinique murin. Ces recherches ont permis la mise en place d’un essai clinique de deuxième ligne sur des patients réfractaires à une première chimiothérapie. [less ▲]

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See detailStructure des communautés de plantes herbacées sur les Grands Causses : Stratégies fonctionnelles des espèces et interactions interspécifiques
Fayolle, Adeline ULg

Doctoral thesis (2008)

Plant community response to grazing management was studied on the INRA La Fage experimental station, Larzac Causse. Land use practices were considered as a disturbance and resource filter that remove ... [more ▼]

Plant community response to grazing management was studied on the INRA La Fage experimental station, Larzac Causse. Land use practices were considered as a disturbance and resource filter that remove species. The integrated approach of community structure used in this study was centred on plant functional traits. Continuous variations of plant traits associated with resource acquisition and early phenology indicated the replacement of stress tolerant species by ruderals along the gradient of land use intensity (grazing avoidance). Graminoids were particularly abundant in these communities. Changes in species identity and species functional identity were consistent with the grazing tolerance strategy. At the community scale, the strong functional convergence among dominant species confirmed the filtering effect of grazing management on these traits. Species richness reached its maximum at intermediate grazing. Maximal richness was associated with the coexistence of many growth forms and an important functional richness. These results are interpreted as an extension of the intermediate disturbance hypothesis to the traits of coexisting species. Finally, plant interaction dynamics experienced by five target species allowed us to identify the tendency of facilitated survival and intensely depressed biomass. The effect of communities was roughly similar although huge differences in specific and functional structure. The response to the least from competition and benefited the most from facilitation. [less ▲]

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See detailBehavior of Deep Reinforced Concrete Beams under Monotonic and Reversed Cyclic Load
Mihaylov, Boyan ULg

Doctoral thesis (2008)

Non-slender reinforced concrete beams find extensive application in cases where heavy loads need to be transferred over a given span. The safety of this kind of structural elements is often critical for ... [more ▼]

Non-slender reinforced concrete beams find extensive application in cases where heavy loads need to be transferred over a given span. The safety of this kind of structural elements is often critical for the safety of the structure as a whole. The research described in this thesis is devoted to studying the behaviour of lightly-reinforced non-slender beams under monotonic and reversed cyclic loads, as particular consideration is given to the load-bearing mechanisms which occur in moderately-deep beams. The choice of this topic was motivated in part by verification studies which show that the current code procedures for shear design of members without web reinforcement are least accurate in the range of transition from deep to slender beams. Furthermore, the issue of cyclic response of lightly-reinforced deep beams is of great importance for seismic assessment of existing structures, especially if the similarity between the load-bearing mechanisms in deep beams and those in other non-slender components such as coupling beams, squat shear walls, and frame joints is recognized. An experimental program consisting of ten tests of large non-slender reinforced concrete beams has been performed. All specimens failed in shear after transition from beam load-bearing mechanism to arch action (specimens without stirrups) or truss actions (specimens with stirrups). A suggested kinematic model was successfully used for interpretation of the various deformation measurements. The results showed that part of the ultimate shear was carried in the cracked concrete. It was concluded that load reversals had little effect on the overall response. A test of deep beam provided with single bar #18 demonstrated that anchorage by anchor heads is effective even when the biggest ASTM reinforcing bar is used. Comparison between experimentally-obtained and calculated shear strengths showed that the CSA code rendered reasonably conservative predictions compared to the mostly unconservative results of the ACI and EC2 codes. Theoretical work resulted in a derivation of an improved strut-and-tie model (ISTM) which is based on the CSA shear provisions but accounts for shear carried under the critical diagonal cracks of non-slender beams without web reinforcement. Verification against a large number of tests showed that the new model is consistent with physical observations and explains the transition from deep to slender beams. Furthermore, it was shown that the ISTM can be used in combination with the above-mentioned kinematic model for estimation of the ultimate displacement and deformed shape of non-slender beams. [less ▲]

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See detailProduction of alarm pheromone in aphids and perception by ants and natural enemies
Verheggen, François ULg

Doctoral thesis (2008)

Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm ... [more ▼]

Most Aphidinae species produce and use (E)-ß-farnesene (Eßf) as an alarm pheromone. This sesquiterpene is released by individuals under attack by a predator, and nearby aphids exhibit a variety of alarm behaviours. This PhD thesis aims to better understand how aphids manage their production and emission of alarm pheromone (Chapter IV). We also wanted, in a second step, to improve our knowledge on the roles that Eßf could play in the relationships that aphids have with their predators (Chapter V) and tending ants (Chapter VI), in order to better pinpoint the problem in this very tough context. The aphid predators have indeed a real advantage to be able to use the odorant cues emitted by their prey, to locate them and to select an adequate oviposition site. Ants establish with certain aphid species mutualistic relationships, which occurrence could be facilitated by the use of aphids’ odours. In Chapter IV, we have highlighted that aphid colonies non subjected to attack by predators release constantly small quantities of Eßf in their headspace, which means that this molecule could have additional roles than just acting as an alarm pheromone. In a second study, we demonstrated that the release of Eßf was not contagious, and therefore that a non stressed aphid receiving the alarm signal does not release additional Eßf. Since the production of alarm pheromone is likely to entail physiological cost, we tested and validated the hypothesis that aphids regulate their Eßf production according to their social environment. In Chapter V, we studied the ability of the hoverfly predator Episyrphus balteatus (Diptera, Syrphidae) to be used as biological control agent against aphids infesting tomato plants (Lycopersicon esculentum). After identifying the odours emitted by aphid infested plants, we have demonstrated that although this Diptera is able to perceive all the odours released by the system, it mainly uses Eßf to select its oviposition site. However, the E. balteatus larvae are not adapted to the architecture of tomato plants. We also showed that the Asian ladybeetle Harmonia axyridis (Coleoptera, Coccinellidae) olfaction was adapted to the perception of Eßf and that this beetle is also attracted by this sesquiterpene. Finally, in Chapter VI, we characterized the benefits accruing to aphid populations that have established mutualistic relationships with Lasius niger (Hymenoptera, Formicidae), and have demonstrated the role of Eßf and honeydew, respectively in locating aphid colonies and in the persistence of the mutualism. [less ▲]

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See detailNovel Strategies towards aminophosphonic derivatives by [4+2] cycloadditions
Monbaliu, Jean-Christophe ULg

Doctoral thesis (2008)

Aminophosphonic and related compounds were almost unknown 50 years ago, but today the literature data have considerably increased. Their negligible mammalian toxicity and their similarity with aminoacids ... [more ▼]

Aminophosphonic and related compounds were almost unknown 50 years ago, but today the literature data have considerably increased. Their negligible mammalian toxicity and their similarity with aminoacids confer on these compounds a top place as potential candidates for drugs. The discovery of numerous natural aminophosphonic derivatives endowed with biological properties useful to both medicinal and agricultural fields enhanced the infatuation for synthetic analogs and homologs. Intensive work has been performed towards alpha-aminophosphonic compounds, the direct analogs of natural alpha-aminoacids, disclosing versatile strategies, compatible both with molecular diversity and asymmetric synthesis. Less synthetic effort was devoted to the synthesis of higher homologs. Recent developments of the Diels-Alder reaction offer an asymmetric and convergent entry to various six-membered highly functionalizable key intermediates, compatible with molecular variety. As it is, the Diels-Alder (D-A) reaction should provide an original and versatile entry to beta-, gamma- and delta-aminophosphonic compounds, a challenging research area. As a direct consequence of the strategy, one of the two D-A partners (diene or dienophile) will act as vehicle for the phosphonate moiety. By contrast to its common use for the stabilization of alpha-negative charges, its implication in D-A reactions remains scarce. Indeed, the phosphonate moiety is not an efficient substituent susceptible to activate the D-A reaction; its use requires compensation by the activation of the other partner or by specific activation. Both synthetic organic and computational chemistry will furnish information to propose a fine understanding of the key D-A steps, in view to optimize the achievement of the corresponding cycloadducts. These cycloadducts will be considered as synth-/chirons for the synthesis of aminophosphonic compounds. [less ▲]

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See detailHagiographie et statistique linguistique : étude d’un corpus de traductions médiolatines d’origine grecque
Philippart de Foy, Caroline ULg

Doctoral thesis (2008)

The dissertation considers a corpus of 35 hagiographic texts translated from Greek into Latin in the Middle Ages. This corpus is representative of the different stages in the history of hagiographic ... [more ▼]

The dissertation considers a corpus of 35 hagiographic texts translated from Greek into Latin in the Middle Ages. This corpus is representative of the different stages in the history of hagiographic translations and of the various centres of translation in Italy. Those translations are to be presented in a new and original way by studying from a linguistic point of view the Latin language used by the translators to render their Greek models and the techniques that were implemented to achieve those translations, considering them not individually but in a global and comparative way. Quantitative linguistics was chosen as a method in order to go through a large corpus and to compare numerous texts, to enlighten their characteristics and their common or opposite features on a lexical as well as a syntactical basis. [less ▲]

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See detailMechanical properties, residual stresses and structural behavior of thin-walled stainless steel profiles
Rossi, Barbara ULg

Doctoral thesis (2008)

Although it offers a wide variety of interesting properties such as fire resistance or durability, stainless steel has been used in limited amount in structures. It is a known fact that the design rules ... [more ▼]

Although it offers a wide variety of interesting properties such as fire resistance or durability, stainless steel has been used in limited amount in structures. It is a known fact that the design rules don't properly account for the additional benefits of stainless steel properties and are largely based on the specifications for carbon steel. Indeed, a number of similarities exist between stainless steel and ordinary carbon steel but there is sufficient differences to afford a specific treatment in design standards. And since stainless steel is an expensive material, it is important to accurately predict the resistance of structural members. The present research work is dedicated to the study of cold-formed stainless steel profiles. It actually follows the life of a stainless steel construction element and falls on three fundamental topics: the material behavior, the through-thickness residual stress distribution and mechanical enhancement due to the cold-forming process and, last, the strength of concentrically compressed thin-walled columns. Firstly, several constitutive models are characterized such as Teodosiu-Hu's micro-structural based hardening model, capable of predicting the behavior of the studied stainless steel grade submitted to biaxial loading causing plastic strain. This model accounts for the nonlinear hardening behavior, the anisotropy, the Bauschinger effect and more complex behavior such as the observed work-hardening stagnation under reversed deformation at large strains. For this purpose, a collection of tests is carried out including multiaxial tests such as tensile-shear tests and successive simple shear tests and plane-strain tests. Secondly, the effects of the forming process on the mechanical properties are studied. To begin with, on the basis of the constitutive models developed previously, an analytical method that calculates the biaxial residual stress distribution in the walls and in the corners of cold-formed profiles is established. Based on the conclusions drawn from this theoretical analysis, a new formula for the evaluation of the actual mechanical properties is established. This formula is not restricted to a single alloy or type of cross-section. Current design standards are then used to calculate the strength of lipped-channel section columns failing by combined distortional and overall flexural-torsional buckling and the results are compared to tests. Indeed, full-scale tests on cold-formed stainless steel lipped channel section columns were achieved in the Structures Laboratory of the University of Liège. And, once verified against the test results, finite element models were used to generate additional results when necessary. The author then presents a new Direct Strength Method taking into account this phenomenon. Finally, a wide amount of reference results are gathered from the literature, without limiting oneself to any kind of cross-section or stainless steel grade. This database is used to propose an improved formulation for the design of stainless steel thin-walled section columns failing by distortion, local or combination of local and overall buckling in the low slenderness range. [less ▲]

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See detailImplantation d'acide hyaluronique estérifié lors de la microchirurgie des lésions cordales bénignes
FINCK, Camille ULg

Doctoral thesis (2008)

La microchirurgie des pathologies cordales bénignes est pratiquée afin d’améliorer les caractéristiques mécaniques du vibrateur laryngé. C’est en augmentant la souplesse tissulaire et la fermeture ... [more ▼]

La microchirurgie des pathologies cordales bénignes est pratiquée afin d’améliorer les caractéristiques mécaniques du vibrateur laryngé. C’est en augmentant la souplesse tissulaire et la fermeture glottique en phonation que le micro-chirurgien espère améliorer les caractéristiques du son laryngé émis. Les techniques microchirurgicales ont évolué de manière spectaculaire au cours des 20 dernières années grâce à la connaissance de plus en plus approfondie de la structure cordale normale et surtout de son tissu conjonctif : la lamina propria. C’est la partie la plus superficielle de la lamina propria, l’espace de Reinke, qui joue le rôle le plus important dans la production du son. C’est aussi l’espace de Reinke qui est occupé, détruit ou remanié en cas de pathologie cordale bénigne. La microchirurgie vise à le libérer du processus pathologique. L’originalité des techniques microchirurgicales exposées dans ce travail est de tenter, non seulement de libérer l’espace vibrant de la lésion cordale, mais aussi de modifier les processus cicatriciels post-opératoires par l’utilisation d’un implant résorbable d’acide hyaluronique estérifié. Les objectifs de ce travail sont : - de contribuer à la connaissance des résultats fonctionnels laryngés et vocaux observés après une microchirurgie cordale - d’évaluer l’impact fonctionnel, sur ces résultats, de l’utilisation d’un implant résorbable d’acide hyaluronique estérifié, en fin d’intervention chirurgicale. [less ▲]

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See detailSystematic Cooperation in P2P Grids
Briquet, Cyril ULg

Doctoral thesis (2008)

P2P Grid computing seeks the convergence of Grid and P2P technologies. Deploying a P2P Grid middleware on a set of computers enables an organization to automatically barter computing time with other ... [more ▼]

P2P Grid computing seeks the convergence of Grid and P2P technologies. Deploying a P2P Grid middleware on a set of computers enables an organization to automatically barter computing time with other Internet-connected organizations. Such P2P exchanges of computing time enable individual Peers, i.e. organizations, to transparently aggregate large amounts of computational power with minimal infrastructure requirements or administrative cost. Challenges arise from the requirement for scalability and robustness. Individual worker nodes are unreliable, as P2P Grids operate on unmanaged desktop computers. A specificity of P2P Grids is that each Peer can reclaim at any time the computational power of worker nodes supplied to other Peers, leading to bursts of execution preemption. These are the major contributions of our dissertation: * Firstly, we propose a new P2P Grid architecture, the Lightweight Bartering Grid (LBG). Through systematic cooperation between Grid nodes, the reliability of execution of computational requests is greater than the sum of the reliabilities of worker nodes. * Secondly, we propose a highly scalable data transfer architecture. It is based both on the BitTorrent P2P file sharing protocol and on the removal of the temporal cost of downloading redundant copies of input data files. * Thirdly, besides a middleware implementation of LBG, we also provide an implementation of a discrete-event simulator. Its originality resides in the weaving of the simulator code into the bartering code of the middleware, which is made possible through the virtualization of Grid nodes. This enables reproducible testing and accurate performance evaluation of the bartering policies because the Peers of a simulated Grid make the same bartering decisions as Peers deployed on real computers. The LBG architecture exhibits the following remarkable features: * The scheduling model supports the queueing of external requests and the architecture enables a flexible study of bartering policies. * The architecture is open, flexible, lightweight and facilitates software engineering. It enables the easy development, testing, evaluation and deployment of combinations of scheduling policies. * The architecture is fully P2P. [less ▲]

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See detailEtudes génétiques et immunomodulatoires de la ghréline sur les traits de production et de conformation en races bovines ainsi que sur la croissance chez le rat
Colinet, Frédéric ULg

Doctoral thesis (2008)

En production animale, notamment dans les filières bovines, il est d’un intérêt économique d’augmenter la quantité d’hormone de croissance dans la circulation sanguine. La ghréline est un peptide ... [more ▼]

En production animale, notamment dans les filières bovines, il est d’un intérêt économique d’augmenter la quantité d’hormone de croissance dans la circulation sanguine. La ghréline est un peptide principalement produit au niveau de la paroi stomacale. Ce ligand endogène au GHSR stimule la sécrétion hypophysaire de l’hormone de croissance. Peptide orexigène, la ghréline est impliquée dans les mécanismes relatifs au maintien de l’homéostasie énergétique. Dans l’optique d’améliorer les performances animales, deux approches de la ghréline ont été effectuées. La première approche consiste en l’étude des gènes bovins codant pour la ghréline (bGHRL) et son récepteur (bGHSR). Ces deux gènes ont été respectivement localisés sur BTA 22 et BTA 1. Quatorze polymorphismes ont été détectés sur ces deux gènes et trois d’entre eux affectent la structure primaire du GHSR bovin. Des associations, à différents niveaux de signification, entre certains de ces 14 sites polymorphiques et des traits de production et de conformation ont été mis en évidence au sein d’un groupe de 127 taureaux Holstein sur base de leurs descendances directes présentes en Région Wallonne. La seconde approche aborde les effets d’une immunisation passive contre la ghréline sur des rats mâles en croissance en comparaison à celles contre la leptine et la cholécystokinine. Lors d’une alimentation équilibrée, le traitement envers la ghréline sur ces rats n’a pas influencé la croissance et l’ingestion par rapport aux animaux témoins. Des effets ont été observés entre les différentes immunomodulations au niveau des paramètres de croissance, d’ingestion et endocrinologiques. Les présents résultats invitent à de nouvelles investigations des gènes bGHRL et bGHSR sur des données relatives à d’autres populations/races bovines et de l’immunomodulation de la ghréline lors de conditions d’expérimentation différentes (alimentation déséquilibrée, stade physiologique, espèce, etc.). Ces investigations pourraient être valorisées en sélection et production animale mais également en médecine tant humaine que vétérinaire. [less ▲]

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