References of "Doctoral thesis"
     in
Bookmark and Share    
Full Text
See detailValorisation du savoir local pour une cogestion conservatoire de l'arganeraie marocaine
Aziz, Larbi ULg

Doctoral thesis (2012)

L’arganeraie est un écosystème particulier disposant d’une biodiversité animale et végétale spécifique dont l’élément central est l’arganier. C’est un arbre multifonctionnel du fait des usages multiples ... [more ▼]

L’arganeraie est un écosystème particulier disposant d’une biodiversité animale et végétale spécifique dont l’élément central est l’arganier. C’est un arbre multifonctionnel du fait des usages multiples qu’en font les populations locales. Il constitue l’élément central du système agraire local car il a configuré et rythmé la vie et les activités des populations. Celles-ci, disposant de nombreux droits de jouissance au niveau de la forêt d’arganier, ont mis au point une gestion communautaire régulant l’accès et le contrôle aux ressources. Cette gestion et le fonctionnement du système agraire témoignent de la possession par ces populations de savoirs et savoirs faire locaux qui perdurent de génération en génération. Toutefois, ces savoirs n’ont pas été assez étudiés pour pouvoir les valoriser. Or, depuis des décennies, les savoirs locaux font l’objet d’intérêt croissant à l’échelle internationale, tant au sein de la communauté scientifique que des ONG internationales. C’est ainsi que cette recherche vise à identifier et à valoriser ces savoirs dans le cadre d’une stratégie de cogestion conservatoire, intégrée et participative de l’arganeraie. Comme outils d’investigation, nous avons eu recours à l’observation et à l’entretien semi directif. Ainsi, nous avons interrogé une centaine de personnes (hommes et femmes) relevant des communes rurales d’Aguerd et de Tidzi (région d’Essaouira). Nous avons aussi interrogé des acteurs institutionnels (agriculture, eaux et forêts, agences, recherche et ONG) en vue de dégager leurs points de vue. Pour l’analyse des données, nous avons utilisé trois méthodes complémentaires: l’analyse descriptive, l’analyse du contenu et l’analyse comparative. Les savoirs locaux identifiés ont été analysés notamment au regard du savoir scientifique. Les résultats ont été comparés entre les deux communes, et au sein de chaque commune ces savoirs sont différenciés selon le genre. Par ailleurs, nous nous sommes basés sur le cadre analytique de Berkes (1999) et sur le modèle IAD Framework d’Orstom (1994) pour pouvoir comprendre la problématique traitée dans toutes ses facettes. Ainsi, nous avons identifié des savoirs relatifs aux trois éléments du système agraire local et à leurs interactions ainsi que ceux relatifs au mode de gestion de la forêt d’arganier et la vie culturelle de la population enquêtée (rites, recettes cosmétiques et de la pharmacopée traditionnelle,..). Il en ressort que l’ensemble de ces savoirs renvoie à une meilleure adaptation de la population à son milieu, à une fine connaissance de l’écosystème et de son fonctionnement. D’autre part, ces savoirs, différenciés selon le genre, montrent que les paysans ne raisonnent pas l’écosystème de manière sectorielle mais dans sa globalité. Par ailleurs, les modes de transmission de ces savoirs sont l’observation, la participation et l’imitation. Cependant, certains de ces savoirs sont en train de disparaître suite aux changements que connaît la zone. Ils doivent donc être requalifiés comme patrimoine culturel à respecter, à conserver, à en contrôler l’accès et à valoriser. D’un autre côté, nos résultats ont montré que l’engouement pour les produits de l’arganier et la flambée de leurs prix à partir de la fin des années 1990, ont entrainé des conséquence socio-économiques au niveau de la zone : changements au niveau des représentations et des comportements des locaux vis-à-vis de l’arbre, apparition de nouveaux acteurs s’enroulant dans des collectifs qui ont beaucoup évolué, mis en place d’un marché peu structuré et pas assez profitable aux locaux, érosion du savoir local, apparition de nouveaux modes d’alimentation, disparition de coutumes et de traditions, etc. ce qui nous a poussé à plaider pour la conception d’une stratégie de conservation de l’arganeraie. Or, de nombreuses actions ont été menées par certains acteurs dans ce sens. Malheureusement, ces efforts sont restés sectoriels, éparpillés, non intégrés et ne prenant pas en compte les nouvelles dynamiques en place. C’est ainsi que nous avons élaboré une proposition de stratégie de cogestion conservatoire de l’arganeraie faisant participer l’ensemble des acteurs, particulièrement les populations locales en valorisant leurs savoirs. Elle se veut cohérente, intégrée et reposant sur les axes suivants : la participation et la concertation entre les différents acteurs, l’assurance d’une bonne gouvernance locale (au sein des structures et entre les partenaires), l’appropriation de l’aménagement de l’arganeraie en valorisant les savoirs locaux identifiés et en appuyant la structure de l’agdal, la structuration du marché et la relocalisation de la plus-value (IGP argane), la promotion du tourisme rural, la réalisation d’actions d’accompagnement. Par ailleurs, cette stratégie doit s’inscrire dans le cadre d’un développement local plus global pour pouvoir prendre en compte l’aspect temporel dans les évolutions des dynamiques en cours. [less ▲]

Detailed reference viewed: 110 (12 ULg)
Full Text
See detailOptimisation de l'utilisation des ressources en eau du bassin du Kou pour des usages agricoles
Traore, Farid ULg

Doctoral thesis (2012)

Water is a priceless natural resource very sensitive to external factors and environmental degradation. It becomes more valuable as competing uses multiply. Therefore, integrated and cooperative water ... [more ▼]

Water is a priceless natural resource very sensitive to external factors and environmental degradation. It becomes more valuable as competing uses multiply. Therefore, integrated and cooperative water resources management is essential within a watershed. The Kou watershed (Burkina Faso) has significant water resources which are divided between domestic (water supply, etc.), agricultural (irrigation) and industrial uses. The hydro-agricultural context of the Kou watershed is marked by a perennial river, along which are located several agricultural areas. Over time, once satisfying water needs degraded to irrigation water deficits, mainly due to a reduction in water supply and an increase in irrigated farmland. Irrigation water deficits are mostly encountered in the more downstream agricultural areas. The socio-economic context is characterized by a growing trend for highly profitable and water consuming crops (e.g. banana). This further increases the irrigation water deficits, as well as the upstream-downstream water-sharing inequalities. In the context of the study area, the main factor that may influence the agricultural water withdrawals is the farmers' production system. The main hypothesis of the study was to verify whether these agricultural production systems could be the lever to optimize irrigation water use. The methodology of the study was to provide a sufficiently accurate knowledge of the water management system, so that improvements could be proposed. A decision support tool based on the ‘multi-agent systems’ approach (MAS) was developed in order to provide an answer to the problems of the study area’s water management by simulating management scenarios. The findings of the study showed (using the MAS tool) that through actions on agricultural production systems it is possible to optimize irrigation water withdrawals. Within the production systems, it is mainly changes in irrigation practices that have led to an optimization of the water management. Finally, the study showed that the use of MAS in resolving agricultural water management issues in the Kou watershed could be the starting point for a new approach in water management. This approach allows the effective integration of the consequences of farmers' decisions regarding water management. More generally MAS-based natural resources management tools provide a common representation of the environment within a model that can help raise awareness concerning a better management of these natural resources. [less ▲]

Detailed reference viewed: 309 (39 ULg)
Full Text
See detailLong-term study of biogenic volatile organic compound exchanges in a forest ecosystem
Laffineur, Quentin ULg

Doctoral thesis (2012)

The terrestrial biosphere, especially forest ecosystems, emits large quantities of volatile organic compounds (VOCs) which have a significant impact on the atmosphere’s chemical and physical ... [more ▼]

The terrestrial biosphere, especially forest ecosystems, emits large quantities of volatile organic compounds (VOCs) which have a significant impact on the atmosphere’s chemical and physical characteristics. In particular, VOCs are precursors in the formation of ozone and sec-ondary organic aerosols. Isoprene and monoterpenes dominate the total VOC emissions, and methanol is one of the most abundant atmospheric VOCs due to its longer half-life than the other two. The main objective of this thesis was to investigate (using the eddy covariance technique and a proton-transfer-reaction mass spectrometer) the mechanisms of VOC (isoprene, monoterpene and methanol) emission and/or deposition at the scale of a temperate climate forest ecosystem (Vielsalm, Belgium) comprising several species (Fagus sylvatica, Abies alba, Picea Abies and Pseudotsuga menziessi). The eddy covariance technique is very suitable for studying VOC emission/deposition mechanisms at ecosystem level as it does not interfere with the functioning of the ecosystem and it has very good temporal resolution (half an hour). It was used for several months at the Vielsalm site without any major interruption to the measurements. The first measurement period ran from early July to late November 2009 and the second from late March to late November 2010. As well as measuring the VOC exchanges by eddy covari-ance, the climate parameters controlling the exchange mechanisms were also measured. During both these periods the methanol, acetaldehyde, acetone, isoprene, methyl vinyl ke-tone/methacrolein, monoterpene, acetic acid (2010) and formic acid (2010) fluxes were meas-ured. The highest emission levels observed were isoprene and monoterpenes along with methanol, which unlike the first two also showed depositions. The thesis therefore naturally focused on studying these three fluxes, in view of the important role played by these three compounds in atmospheric chemistry and hence the scientific community’s interest in refining the parametrisation of these compounds’ ecosystem/atmosphere exchange models. The study of the isoprene, monoterpene and methanol fluxes has been written up in three original articles which form the main body of this thesis. Because of the heterogeneity of the ecosystem studied, the first essential study concerned the identification of VOC-emitting species. This was done with the aid of a flux footprint model combined with a map of the species occurring on the site. This analysis showed that the main monoterpene emitter was Fagus sylvatica followed, to a lesser extent, by Abies alba, Picea Abies and Pseudotsuga menziessi. In contrast to the literature, the analysis showed Abies alba to be a probable isoprene emitter but the presence of Picea Abies, a known isoprene emitter, ruled out absolute certainty on that point. The isoprene fluxes were observed by day only, unlike the monoterpene fluxes which were observed both day and night. Diurnal flux analysis clearly showed temperature and light to be the two main variables controlling emissions. Combining this analysis with a study of the close relationship between isoprene/monoterpene emissions and photosynthesis revealed the plants’ de novo biosynthetic production mechanisms, an original aspect at ecosystem scale. From the occurrence of nocturnal monoterpene emissions it was possible to determine that de novo monoterpene production emitted directly into the atmosphere (as in the case of isoprene) was not the only source of the emissions observed. Withdrawals from monoterpene sinks located in plant organs or in the soil can also be monoterpene sources. Studying the relationship between isoprene/monoterpene fluxes and light, distinguishing between cloudy and sunny conditions, showed that for the same light intensity the emissions were higher in cloudy con-ditions than in sunshine. Similarly, a study of the relationship between isoprene fluxes and photosynthesis in cloudy/sunny conditions suggested that de novo isoprene production is greater in leaves above the canopy than in leaves within the canopy. Long-term measurement of isoprene and monoterpene emissions enabled seasonal changes in the mechanisms observed to be studied and more fully understood. As well as providing an understanding of the mechanisms, this research also resulted in quantification of the seasonal changes in the key parameters for modelling isoprene/monoterpene emissions. Methanol exchanges were generally positive (emissions) by day and negative (depositions) at night. Overall, methanol depositions were predominant in summer and autumn but in the mi-nority in spring. On average, the Vielsalm site behaved like a methanol sink, which contradicts all the other research published to date. An original model was developed for identifying the mechanisms responsible for short-term and long-term methanol emissions/depositions. The consistency between the measurements and the model simulations suggested that the main processes controlling methanol exchanges in summer could be attributed, in the short term, to (water-soluble) methanol adsorption/desorption occurring in the films of water on leaf surfaces and/or on the soil surface and, in the long term, to methanol destruction by a biological and/or chemical degradation process also occurring on the surface of leaves and/or the soil. A study of the difference between the measurements and the model, in spring, indicated the possibility of biosynthetic methanol production by the plants. This production was apparently controlled mainly by temperature, but it could not be shown in summer when methanol adsorption/desorption processes dominated. The literature on ecosystem-atmosphere exchanges of isoprene, monoterpenes and, to a lesser extent, methanol is extensive. Nevertheless, what makes this research original is the spatio-temporal scale used. We are in fact working at ecosystem scale, and not at leaf or branch scale as in most other cases. Moreover, our measurements cover a timescale from half an hour to a full growing season, which is rarely found in the literature. This has resulted in a better under-standing of these compounds’ production and exchange mechanisms. To be precise, the methanol flux study is currently unique in its description and understanding of the deposition mechanisms. [less ▲]

Detailed reference viewed: 64 (11 ULg)
See detailAlternative possible à la production traditionnelle du coton en Afrique dans une perspective de développement durable? Le cas du système de production biologique et équitable au Mali
Dembele, Kouloumegue ULg

Doctoral thesis (2012)

SUMMARY The general objective of this work is to analyze the viability of the culture of organic fair trade cotton in comparison with that of conventional cotton. The study was conducted with a sample of ... [more ▼]

SUMMARY The general objective of this work is to analyze the viability of the culture of organic fair trade cotton in comparison with that of conventional cotton. The study was conducted with a sample of 45 farms with 15 farms per system, and following a systemic approach at three levels: the land of cotton cropping systems based on cotton and across the operation. At the cotton, whatever the socio-economic producer, cotton compared to conventional cotton has lower average yields, work time higher and smaller plots (0.85 ha production organic fair against 2.35 and 1.76 ha respectively in conventional production calendar and thresholds. organic fair trade cotton generates less revenue because of smaller plots. Nevertheless, the cotton is organic fair identified two broad categories of farms: farms with high levels of resources have an important livestock farms and poor with little means of production, for which the organic fair trade cotton is one of the few alternatives for income money. It should be noted that the level of these poor farms, it is often women and dependent operations manager who practice organic cultivation of cotton. Only farms with high level of resources that have a herd can derive significant profits from the cultivation of organic fair trade cotton. The alternative organic fair this effect allows access to land and access to the culture of cotton formerly marginalized groups, including women, unlike conventional cotton where only the manager manages the cultivation of cotton. There is thus improving the status of women. However, the lack of sustained management of soil fertility and nutrient compromises obtaining better yields - which is a key success factor to be and remain competitive. Level of cropping systems, comparative analysis of the performance of cropping systems confirms that productivity and valuation levels of the working day cultures and cultivation systems based on organic fair trade cotton are lower than obtained by conventional production. At the farm level, conventional production systems produce between 29% (SPCca) and 43% (SPCs) more grain from the organic production system. Reflecting the fragility of food security in the region in case of massive conversion to organic production. Regarding environmental sustainability, it appears that the most important contribution of organic cotton is safe for human health and the environment of the inputs used. [less ▲]

Detailed reference viewed: 58 (29 ULg)
Full Text
See detailFirst-principles and experimental studies of hexagonal YMnO3 single crystals and epitaxial films
Prikockyte, Alina ULg

Doctoral thesis (2012)

Multiferroic materials have attracted much interest during the recent years. Our study is devoted to a prototypic system: yttrium manganite. In particular, we focus on the ferroelectric properties in bulk ... [more ▼]

Multiferroic materials have attracted much interest during the recent years. Our study is devoted to a prototypic system: yttrium manganite. In particular, we focus on the ferroelectric properties in bulk and in thin film forms. Yttrium manganite belongs to the class of ABO3 compounds. Most theoretical studies of ferroelectricity to date were concentrated on cubic perovskite ABO3. Yttrium manganite is hexagonal and is an improper ferroelectric. We were interested to study theoretically and experimentally how these two features behave in thin film form. Our study is organized as follows. [less ▲]

Detailed reference viewed: 85 (16 ULg)
Full Text
See detailDevelopment of a transmission model of Murid herpesvirus 4
François, Sylvie ULg

Doctoral thesis (2012)

Gammaherpesviruses are the archetype of persistent viruses that have been identified in a series of animals ranging from mice to man. To date the study of transmission of these viruses in natural ... [more ▼]

Gammaherpesviruses are the archetype of persistent viruses that have been identified in a series of animals ranging from mice to man. To date the study of transmission of these viruses in natural condition has been limited by the fact that no experimental transmission model exists. Establishment and characterization of a model of transmission are therefore critical points to evaluate strategies of interference with the epidemiological cycle of gammaherpesviruses. We are studying Murid herpesvirus 4 (MuHV-4) which has originally been isolated from naturally infected bank voles (Myodes glareolus). Although serological data indicate that closely related strains are present in wood mice (Apodemus sylvaticus) and domestic mice (Mus musculus), no experimental transmission of MuHV-4 has been demonstrated in laboratory mice, the classically used in vivo model. The objective of this work was therefore to fill this gap. In a first study, we performed a comparative characterization of the infection by MuHV-4 in mice and bank voles. Our results showed that the infectious process, the pathology and the latency establishment are similar in the two species, even if replication is quantitatively lower in bank voles than in mice. It therefore appeared that, Mus musculus represents a suitable host for studying gammaherpesvirus pathogenesis with MuHV-4. These results have been published in Journal of General Virology (J Gen Virol. 2010 Oct;91(Pt 10):2553-63). In a second study, thanks to in vivo imaging, we have been able to observe, for the first time, transmission of MuHV-4 in mice. We firstly showed that MuHV-4 reexcretion occurs in the genital tract of female mice at a period by which latency is considered as established. Ex vivo imaging, histology and PCR allowed us to demonstrate the presence of viral genomes in vaginal tissues and to localize viral replication at the external border of the vagina. We also demonstrated the transient and repetitive presence of infectious viruses in the vaginal cavity. Secondly, we demonstrated the implication of sexual steroid hormones in this re-excretion process. Indeed, we analyzed the infection of untreated mice, ovariectomized mice and ovariectomized mice complemented with estrogens and/or progesterone. These analyses revealed a positive role of estrogens in the observed re-excretion. Finally, based on these results, we tested MuHV-4 transmission in mice by creating different epidemiological conditions. In the conditions tested, vertical transmission did not occur, nor did horizontal transmission between individuals of the same gender. In contrast, we were able to observe sexual transmission to naïve males by serology, in vivo imaging and quantitative PCR. In conclusion, this work has on one hand demonstrated the quality of mice as an in vivo model for MuHV-4 studies and, on the other, it has shown for the first time the existence of re-excretion and sexual transmission of MuHV-4 amongst laboratory mice. The results of this work should therefore have implications for the study of gammaherpesviruses, but also more generally for the study of sexually transmissible infections. [less ▲]

Detailed reference viewed: 51 (15 ULg)
Full Text
See detailLe nationalisme algérien et ses diverses expressions dans l'immigration en France métropolitaine entre 1945 et 1965
Abssi, Marion ULg

Doctoral thesis (2012)

L'auteur traitre du combat des immigrés algériens pour l'indépendance de leur pays d'origine depuis le sol métropolitain entre 1945 et 1965, de l'implantation, de l'évolution et des méthodes d'action des ... [more ▼]

L'auteur traitre du combat des immigrés algériens pour l'indépendance de leur pays d'origine depuis le sol métropolitain entre 1945 et 1965, de l'implantation, de l'évolution et des méthodes d'action des différentes organisations nationalistes algériennes représentées en métropole, et des conflits ayant opposés les Algériens aux Européens mais aussi et surtout les Algériens entre eux durant toute la période considérée. [less ▲]

Detailed reference viewed: 101 (11 ULg)
Full Text
See detailIonosphere Modelling for Galileo Single Frequency Users
Bidaine, Benoit ULg

Doctoral thesis (2012)

Nowadays the ionosphere constitutes one of the most often modelled natural media. Indeed each GPS receiver among nearly two million units sold daily throughout the world runs a model to mitigate the ... [more ▼]

Nowadays the ionosphere constitutes one of the most often modelled natural media. Indeed each GPS receiver among nearly two million units sold daily throughout the world runs a model to mitigate the ionospheric effect affecting the signal propagation from the satellites. This propagation is delayed by the free electrons in the atmosphere so that the navigation signals appear to travel distances larger than actual ones by 7 m on average. Hence this delayed propagation deteriorates the positioning accuracy deemed on a 10−m level for mass-market applications mainly involving single frequency users. Tomorrow the European navigation system Galileo will offer a new mitigation strategy to single frequency users. This strategy will rely on the NeQuick ionospheric model and associated broadcast information. To be properly implemented, it must be extensively described to future Galileo users. These users will also wonder about its effectiveness in accounting for the ionospheric delay. The PhD research covered by the present thesis has built on Belgian expertise in ionosphere monitoring to investigate the NeQuick model and its use for Galileo. It began with the collection and handling of ionosphere measurements including GPS data. It analysed various situations at different places in the world encompassing a whole year (2002). This PhD thesis provides the ins and outs of the Galileo Single Frequency Ionospheric Correction Algorithm. It gathers an algorithm description, a performance evaluation and a variant investigation. In the shape of a paper collection, it discloses many figures as visual entry-points into the juxtaposed text and includes many references allowing to dig into the details. The algorithm performances are usefully characterised both in terms of delay mitigation and positioning accuracy. On the one hand, the residual ionospheric delay reaches 31% for the chosen sites and year. On the other hand, the positioning accuracy amounts to 6 m horizontally and 9.3 m vertically. The performance evaluation allowed to emphasise several aspects of the Galileo ionospheric correction. This correction depends largely on the modelling of the topside, the upper part of the ionosphere, which hosts more complex physical processes. It owes its good performances to data ingestion, the model adaptation technique to actual measurements underlying the Galileo algorithm. It does not necessarily provide highly correlated correction levels in terms of delay on the one hand and positioning on the other. It enables the definition of alternative regional procedures following a compatible design but coping with its weaknesses. The present thesis paves the way for future work related to ionosphere modelling for Galileo single frequency users. It supplies comparative information for the algorithm assessment in the framework of successive phases of Galileo deployment. It establishes a conceptual basis for an Assisted Ionospheric Correction Algorithm (A-ICA) disseminating more flexible ionospheric information thanks to the integration of Global Navigation Satellite Systems and telecommunications. [less ▲]

Detailed reference viewed: 437 (38 ULg)
See detailEtude hydrogéologique du système aquifère du horst de Diass en condition d’exploitation intensive (bassin sédimentaire sénégalais) : apport des techniques de télédétection, modélisation, géochimie et isotopie
Madioune, Diakher Hélène ULg

Doctoral thesis (2012)

Le système aquifère du horst de Diass situé à 50 km à l’Est de Dakar (Sénégal) est soumis à des pompages intensifs depuis plus de 50 ans pour assurer en continu une demande en eau sans cesse croissante ... [more ▼]

Le système aquifère du horst de Diass situé à 50 km à l’Est de Dakar (Sénégal) est soumis à des pompages intensifs depuis plus de 50 ans pour assurer en continu une demande en eau sans cesse croissante destinée à l’Approvisionnement en Eau Potable (AEP) de la ville de Dakar et des localités de Sébikotane, Pout, Mbour ainsi que leurs besoins industriels et agricoles. La configuration géométrique du système est caractérisée par quatre failles majeures délimitant un horst où affleure la nappe du Maastrichtien gréso-calcaire et sablo-gréseux du compartiment de Diass encadrée par les compartiments calcaires affaissés de Sébikotane et de Pout qui hébergent la nappe captive à libre du Paléocène. L’exploitation de ce système a progressivement évoluée pour atteindre actuellement plus de 109000 m3/j environ avec cinq principaux centres de captage. Cette exploitation intensive a provoquée une baisse continue du niveau des nappes, un changement dans le régime des flux et une salinisation dans les zones de Sébikotane et de Mbour. Ainsi donc, il est nécessaire d’étudier les caractéristiques des aquifères notamment, leurs relations hydrauliques verticales et latérales. Cependant, cette étude reste difficile en raison de la complexité de la configuration géométrique du système et des pompages intensifs. La présente étude vise à contribuer à une meilleure compréhension du fonctionnement hydrodynamique du système pour une bonne gestion durable des ressources en eau. Plus précisément, il vise à déterminer : (1) le comportement spatio-temporel de l’hydrodynamisme et de l’hydrochimisme du système en rapport avec les pompages, (2) la recharge actuelle des eaux souterraines, (3) les zones potentielles de recharge nécessaires au calcul du bilan. Pour atteindre ces objectifs, une approche multidisciplinaire comportant une étude piézométrique, hydrogéochimique, d’estimation de la recharge spatialement distribuée et de modélisation a été utilisée. Les variations spatio-temporelles de la piézométrie depuis les années 1960 en rapport avec la configuration hydrogéologique combinées aux données chimiques et isotopiques ont été considérées pour fournir une meilleure compréhension du fonctionnement hydrodynamique du système et établir le modèle conceptuel de circulation des eaux. Les méthodes de Thornthwaite et Penman sont utilisées pour estimer la recharge qui a été spatialement distribuée sur les zones potentielles de recharge. Les enseignements clés tirés de ces différentes approches sont utilisés comme paramètre d’entrée du modèle hydrogéologique 3D développé et calibré en régime permanent et transitoire pour les périodes 1960-1971 et 1971-2009 respectivement. Les résultats montrent l’influence prépondérante des pompages sur le niveau piézométrique favorisant ainsi la drainance verticale et latérale vers les captages. Les données chimiques et isotopiques reflètent la dynamique du système. Les faibles teneurs en tritium et en 14C montrent une absence de recharge actuelle et une prédominance d’eaux anciennes dans le système. Cependant, la présence d’eau tritiée au droit de quelques forages indique un mélange avec des eaux récentes par drainance verticale descendante et/ou par écoulement latéral. Le fonctionnement hydrodynamique dérivé de ces résultats montre que le réservoir fonctionne comme un système aquifère multicouche avec des compartiments interconnectés par des failles qui favorisent des échanges de flux. L’aquifère du Quaternaire est alimentée par l’infiltration des eaux de pluie particulièrement dans la zone de Mbour (1) ; cette aquifère est drainé par les nappes profondes du Paléocène et du Maastrichtien (2) ; ce dernier draine le Paléocène (3), les écoulements latéraux se font du Maastrichtien de Diass vers le compartiment de Pout Sud et à partir du compartiment de Thiès vers le compartiment de Pout à travers les failles de Pout et de Thiès respectivement (4). [less ▲]

Detailed reference viewed: 376 (51 ULg)
Full Text
See detailAdaptations structurales et fonctionnelles aux températures extrêmes au sein de la famille des alpha-amylases chlorure-dépendantes
Cipolla, Alexandre ULg

Doctoral thesis (2012)

L’adaptation thermique des protéines extremophiles a été étudiée de manière à approfondir notre compréhension des mécanismes moléculaires qui en sont responsables. Dans ce but, deux études ont été ... [more ▼]

L’adaptation thermique des protéines extremophiles a été étudiée de manière à approfondir notre compréhension des mécanismes moléculaires qui en sont responsables. Dans ce but, deux études ont été initiées et publiées. La première est basée sur la "mésophilisation" de l’α-amylase psychrophile AHA, issue de la bactérie Antarctique Pseudoalteromonas haloplanktis. L’ajout d’interactions faibles et d’un pont disulfure présents chez son homologue mésophile PPA de Sus scrofa et absents chez AHA ont permis de construire deux mutants multiples stabilisés, Mut5 et Mut5CC. Ces quatre enzymes ont été étudiées sur base de leur stabilité, de leur activité et de la perméabilité de leur structure protéique. L’étude des cinétiques de renaturation/dénaturation d’AHA, Mut5 et Mut5CC a permis de déterminer l’origine cinétique du gain de stabilité liée à l’ajout d’interactions faibles et du pont disulfure chez AHA. Il en résulte que Mut5 et Mut5CC ont effectivement été stabilisés mais en contrepartie ils ont perdu l’optimalisation de l’activité à basse température observée chez AHA. De plus, la perméabilité de leur structure protéique s’est réduite, se rapprochant de celle de PPA. L’origine du gain de stabilité est liée à une diminution des cinétiques de dépliement sans modification des cinétiques de repliement. Non seulement ces résultats démontrent l’importance du rôle des interactions faibles dans l’adaptation thermique des protéines mais de plus, ils démontrent la synergie entre celles-ci. La seconde étude a pu être développée par la découverte d’une α-amylase chlorure-dépendante thermophile TFA issue de l’actinomycète Thermobifida fusca et par la production de l’α-amylase chlorure-dépendante mésophile ectotherme DMA de Drosophila melanogaster. Ainsi avec AHA et PPA respectivement comme représentants psychrophile et mésophile homéotherme, nous pouvions couvrir l’ensemble des températures physiologiques/environnementales connues. Nous avons pu mettre en évidence le continuum des propriétés physico-chimiques observées (activité, stabilité, affinité pour le substrat…) mais aussi que l’énergie thermique de l’environnement influence grandement l’activité enzymatique qui ne serait pas contrebalancée par les mécanismes adaptatifs. L’influence de la température sur l’activité a mis en évidence la plus faible dépendance d’AHA par rapport à TFA. Ces travaux ont permis d’améliorer notre compréhension des mécanismes moléculaires liés à l’adaptation thermique des protéines et du rôle joué par les interactions faibles dans cette adaptation. Ils ouvrent aussi la voie à de futures recherches visant à analyser par d’autres méthodes la flexibilité de la structure protéique et à cristalliser TFA pour étudier d’un point de vue structural le continuum des propriétés physico-chimiques mis en évidence au cours de ce travail. [less ▲]

Detailed reference viewed: 55 (5 ULg)
Full Text
See detailPresent and future Greenland ice sheet surface energy balances with the help of the regional climate MAR model
Franco, Bruno ULg

Doctoral thesis (2012)

See enclosed abstract-and-contents.pdf

Detailed reference viewed: 39 (14 ULg)
Full Text
See detailStructure and Lattice Dynamics of Thermoelectric Complex Chalcogenides
Bauer Pereira, Paula Beatriz Lee ULg

Doctoral thesis (2012)

The goal of this work is to characterize the structure and lattice dynamics of complex chalcogenide alloys. Particular interest is paid to the system AgPbmSbTem+2 (LAST-m), AgSbTe2 and the binaries PbTe ... [more ▼]

The goal of this work is to characterize the structure and lattice dynamics of complex chalcogenide alloys. Particular interest is paid to the system AgPbmSbTem+2 (LAST-m), AgSbTe2 and the binaries PbTe, SnTe and GeTe. Synchrotron radiation studies including high energy X-ray di raction and nuclear inelastic scattering, and macroscopic measurements of heat capacity and elastic constants were performed. A new resonant ultrasound spectroscopy setup with capable of performing measurements from room temperature to 1073K was built for mechanical characterization of the thermoelectric alloys at their working temperatures. The rst chapter presents a brief review of relevant information on thermoelectricity and on the materials under study. The characterization methods including heat capacity, resonant ultrasound spectroscopy, X-ray di raction and nuclear inelastic scattering are introduced. Not as an exhaustive review, but rather in order to give the reader a basic level of understanding and a sense of the acessible information. The introduction is followed by three chapters which address the experimental studies of lattice dynamics in chalcogenide alloys. Chapter 2 describes the lattice dynamics in the compounds GeTe, SnTe and PbTe studied by 119Sn and 125Te nuclear inelastic scattering. The obtained partial density of phonon states were compared with published theoretical calculations, and the resulting vibrational properties were found to be in good agreement with these reports. Additionally, the phase purity and structure were characterized by high energy X-ray di raction. The atomic arrangement, rhombohedral for GeTe and cubic for SnTe and PbTe, is seem to a ect the density of phonon states, with the NaCl-type structure having a softer character in comparison with the rhombohedral structure. In Chapter 3, the lattice dynamics of a polycrystalline AgSbTe2 sample was investigated by 121Sb and 125Te nuclear inelastic scattering, at low temperatures. For this compound, the phonon modes have energies below 25meV and a sound velocity of vs =1490(30) m/s was determined. A simple temperature independent estimation of the lattice thermal conductivity of AgSbTe2 yielded L =0.50 0.05Wm􀀀1K􀀀1. The low Debye temperature, D =150(15)K combined with the short phonon lifetime and the low sound velocity are found to be key factors for the low thermal conductivity in AgSbTe2 and are related to the good thermoelectric performance in AgSbTe2 and AgSbTe2containing systems. Chapter 4 is dedicated to the study of the average and local structure in bulk AgPb18SbTe20 alloy, by a combined Rietveld and Pair Distribution Function analysis. The strong in uence of the synthesis conditions on the lattice parameters and on the composition and the concentration of nanoclusters in LAST-18 is con- rmed. Moreover, the 121Sb and 125Te partial density of phonons states were obtained by nuclear inelastic scattering in order to separately characterize the lattice dynamics from the matrix and the nanoinclusions. Additional characterization of the elastic properties and lattice governed properties were performed by resonance ultrasound spectroscopy, heat capacity and thermal expansion measurements. The nal chapter is dedicated to the resonant ultrasound spectroscopy technique, and the process of building up this bu er-rods high-temperature measurement system are presented. Advantages and disadvantages, as well as limitations and di culties are discussed. Using the \mode-tracking" method, the mechanical behavior of a PbTe and a Niobium sample, from room temperature to 523K and from room temperature to 973 K, respectively, were investigated. [less ▲]

Detailed reference viewed: 363 (10 ULg)
Full Text
See detailA multiaxial constitutive model for concrete in the fire situation including transient creep and cooling down phases
Gernay, Thomas ULg

Doctoral thesis (2012)

Purpose - The present thesis aims to develop an efficient and reliable multiaxial concrete model for implementation in finite elements softwares dedicated to the analysis of structures in fire. The need ... [more ▼]

Purpose - The present thesis aims to develop an efficient and reliable multiaxial concrete model for implementation in finite elements softwares dedicated to the analysis of structures in fire. The need for proper concrete model remains a very challenging task in structural (fire) engineering because of the complexity of the concrete mechanical behavior characterization and the severe requirements for the material models raised by the development of performance-based design. Methodology - The thesis opted for a phenomenological approach for modeling the thermo-mechanical behavior of concrete. The specifications of the model are based on the study of published experimental data of concrete samples tests and on the specific needs related to the applications in structural fire engineering. With these specifications in mind, a state of the art review of concrete models is conducted in order to choose the general theoretical framework that best fits the criteria for the development of the new model. The thesis presents the theoretical development of the model and its numerical implementation in a finite elements software. Numerical simulations of experimental tests are then performed to verify that the model satisfy the specifications. Findings - The combination of elastoplasticity theory and damage theory allows to develop a phenomenological model suitable for concrete behavior modeling within the pragmatic and robust theoretical framework of continuum constitutive models based on smeared crack approach. The state of damage in concrete, assumed isotropic, is modeled by means of a fourth order damage tensor to capture the unilateral effect. When complex performance-based situations are considered, the effect of transient creep strain at high temperature must be taken into account by an explicit term in the strain decomposition. A generic transient creep model is therefore developed based on experimental data and the model is calibrated to yield the same results as the Eurocode implicit model in simple prescriptive situations. The concrete model comprises a limited number of parameters that can be identified by three simple tests; besides, a standard set of values to be used in predictive calculations is clearly defined for these parameters. Numerical simulations can deal with all stress states as the model is developed as fully three-dimensional. A large number of examples highlight the capabilities of the model that range from the modeling of sample tests to the modeling of large scale composite structures developing membrane action. Limitations – Due to the assumption that damage and plasticity are driven by the same internal variables in the model, a limitation appears for capturing the concrete post-peak behavior in highly confined stress states. This assumption allows for reducing the number of parameter but it restrains the domain of applicability of the model; it is suggested to adopt a different approach if the behavior in multiaxial compression at high confinement level has to be accurately captured. Another limitation of the model is related to the localization issue, which is only partly addressed in this work by means of the regularization of the crack energy. Further works should bring a more elaborated response while considering the case of reinforced concrete structures, in which numerous cracks develop. Finally, several simplifying assumptions have been adopted to restrain the scope of the research; for instance, the phenomenon of spalling has not been considered. Practical implications - The thesis includes implications for the development of advanced numerical tools for the simulation of concrete structures at ambient temperature and at high temperature. The use of such advanced tools in the design may lead to significant reduction in the building costs and to improved robustness of the structures. Value – The thesis contributes to fulfil an identified need to make available proper constitutive concrete model for implementation in finite elements softwares dedicated to the analysis of structures in fire. Special care is given to the numerical robustness of the model and to the clear definition of the material parameters as the model is intended to be used by structural (fire) engineers in real applications. [less ▲]

Detailed reference viewed: 172 (49 ULg)
Full Text
See detailThe Unharnessed World: Janet Frame and Buddhist Thought
Gabrielle, Cindy ULg

Doctoral thesis (2012)

Though New Zealand author Janet Frame (1924-2004) lived at a time of growing dissatisfaction with purely Western (i.e. European) cultural models, her work has so far never been examined from the vantage ... [more ▼]

Though New Zealand author Janet Frame (1924-2004) lived at a time of growing dissatisfaction with purely Western (i.e. European) cultural models, her work has so far never been examined from the vantage point of its indebtedness to Eastern epistemologies, and to Buddhism in particular. Even though it is possible to establish links between an author and a given system of thought (Heidegger’s for instance) without necessarily buttressing the comparison from a factual perspective, in this case, the author’s (auto-)biography, her fiction and letters, as well as the circles of Buddhists or Buddhist-sympathizers in which she evolved at a given time, all testify to the fact that a direct encounter between Janet Frame and Buddhism did occur. It can thus be affirmed that, just like W.B. Yeats, C.G. Jung, Heidegger and many others before her, one of the most striking personalities of the 20th century was drawn eastward. The relevance of this study to Janet Frame scholarship resides not only in its politicized angle of approach but also, more importantly, in the fresh light it sheds on entire segments of the Framean corpus which have tended to remain obdurately mysterious; this includes passages centering on e.g. the existence of a non-dual world, a reality un-harnessed by the partial categories of empirical thinking, on a character’s sudden embrace of a non-ego-like self, or on the jolting back of distracted individuals into an awareness of their physical reality in ‘this’ profane world. On the whole, and despite this apparent profusion of themes, my concern is to show that these obscure passages, as well as many other key moments in the narratives, all coalesce into a systematic deconstruction of empirical thinking and its point of anchorage in a discriminating kind of consciousness, both notions forming excellent points of entry into virtually all the texts produced by Frame. Through a careful mapping of the impact of discriminating habits of thought on the self’s place of being in the world and perception thereof, this work clarifies, or rather reconstructs, the narratological architecture of the studied texts – especially the novels – quite apart from the somewhat restrictive view, held in some circles of literary criticism, that they are mazes of random turnabouts and dead-ends where narrotological playfulness is valorized for its own sake. To provide just one example of how a study of Janet Frame via Buddhist thought facilitates the navigation of the author’s intricate novels, the idea in Buddhism that the artist is the bow that shoots the arrows, but then s/he is the target also, is a useful starting point for analyzing the seminal “Jan Godrey” (one of Frame’s best known short stories) in which a terrified author-figure finally allows her creature of words, described as an alien inside, to take full control of the speaking position. A contrario, Thora Pattern’s willingness in The Edge of the Alphabet to trap her creation within neat academic cages of words (as she calls them) spawns images of a hellish self-scape of containment which translate in an endless regression of framed frames since her attitude is paralleled by some of her own creatures of words and by the Christian God Himself – each at his or her level of being and of influence. But that is not all for, in a last turn of the screw, and pace the critics who diminish their roles in the narrative, Thora’s characters rebel against their creator, and they succeed in jamming her creative incarcerating mechanisms so that, by the end of the novel, the author-figure is no longer able to exist without the not-self. This dialectics of un/framing, in which a discriminating consciousness battles against the invading otherness of the non-dual, unharnessed world in all its manifestations, is one which typically informs the Framean corpus although, of course, the architecture of enactments it gives birth to is as varied as it is unpredictable. The idea, which Frame shares with Buddhism or with Nietzsche (who, incidentally, owes an intellectual debt to Buddhism), that most of the human existence is characterized by the “will to power,” i.e. by the drive to take full possession of one’s chosen place of being, is rather unflattering for her fellow human beings. In another sense, the author’s conception of our (in-)humanity as being made up of an accretion of egotistic habits that can be unlearned certainly explains why, in her oeuvre, a liberation from totalizing structures demands an encounter with the negative of place, of identity, of vision, of sound, of fullness, of shape, of well-worn mind-routes and, as we saw in the last chapter, with the negation of negation. Often, it takes no less than a rebellion of the supposedly harnessed reality to disorient a protagonist’s dualistic bearings or to jam an artist’s incarcerating mechanisms; and this, in part, accounts for the extreme physicality encoded in a fiction replete with moments of thumping or bashing – indeed with the promise of a cut finger. Still pondering the centrality of ‘unframed’ or ‘ego-less’ modes of being, each of the nine chapters that constitute this work aims at countering the oft-recurring claim that Frame’s oeuvre is studded with traces of a ‘beyond’ which no character can ever approach because ‘one cannot explore beyond’. By this definition, each of the questing selves that clutters the author’s haunting universe is condemned to failure beforehand, as it were, while concomitantly the Framean text itself is deemed to be bleak, defeatist, even nihilistic. Therefore, it is of the utmost significance that a Buddhist navigation of Frame’s texts should lead one to the conclusion that this unharnessed world which human beings are often unable to apprehend and embrace has always been right under their nose so that, between ‘this’ world of limited perceptions and ‘that’ world of the beyond, the boundary is as thick or as thin as the walls of a self-made conceptual prison. Indeed, whenever the aspect of the intellect that filters perceptions into mutually excluding categories fails to function, or is willingly jettisoned by a protagonist, s/he finds a place of subjective arrival in, and sees, this supposedly unknowable ‘beyond’. Thus, possibly against the grain of mainstream criticism, this study argues that Janet Frame constantly seeks ways through which the infinite and the Other can be approached, though not corrupted, by the perceiving self, and that she found in the Buddhist epistemology a pathway towards grasping such alterity. [less ▲]

Detailed reference viewed: 76 (13 ULg)
See detailSubstrats cérébraux des processus moteurs automatiques et inconscients
D'Ostilio, Kevin ULg

Doctoral thesis (2012)

Detailed reference viewed: 25 (4 ULg)
See detailLe terrorisme à motif religieux en Turquie : Recrutement, profils et motivations des membres du Hizbullah turc
Gülver, Murat ULg

Doctoral thesis (2012)

Depuis plus de cinquante ans, la Turquie a été la victime permanente d’actes terroristes aux multiples motivations. Ces dernières années, le terrorisme à motif religieux y a connu une montée en puissance ... [more ▼]

Depuis plus de cinquante ans, la Turquie a été la victime permanente d’actes terroristes aux multiples motivations. Ces dernières années, le terrorisme à motif religieux y a connu une montée en puissance. Plus de dix organisations terroristes, se basant sur une idéologie religieuse, ce sont organisées sur le territoire turc dans le but de changer le système politique et pour fonder un État islamique. Dans cette recherche, nous avons examiné le cas du Hizbullah turc, en tant que la plus grande et la plus violente organisation terroriste à motif religieux en Turquie. Cette étude a exploré d’abord les méthodes de recrutement du Hizbullah, ensuite les profils de ses militants et enfin les motivations individuelles et les facteurs, qui se trouvent à la base de la radicalisation religieuse en Turquie. Pour ce faire, l’examen quantitatif et qualitatif de données originales comble les principales lacunes dans la recherche sur le terrorisme à motif religieux et donne des indications pour de futures recherches criminologiques et de politiques de sécurité préventives. Dans cette étude, pour examiner et comprendre le recrutement, les profils et les motivations des membres du Hizbullah, nous avons utilisé essentiellement deux sources : les autobiographies des militants eux-mêmes et les entretiens semi-structurés avec des policiers spécialistes du terrorisme à motif religieuse, ainsi que des desservants du culte islamique, qui ont une expérience dans les régions où le Hizbullah était actif. Cette recherche entend apporter une contribution significative à la compréhension des motivations individuelles des militants du Hizbullah, à l’identification des caractéristiques des membres, et à la définition des méthodes de recrutement de l’organisation. Elle propose en outre de nombreuses informations aux organisations de sécurité pour la lutte antiterroriste. [less ▲]

Detailed reference viewed: 89 (17 ULg)
Full Text
See detailLa protéine JNKBP1 agit comme un régulateur négatif de la signalisation de NOD2 en inhibant son processus d’oligomérisation
Lecat, Aurore ULg

Doctoral thesis (2012)

Le récepteur cytoplasmique NOD2 est l'un des membres les mieux caractérisés de la famille des NLRs. NOD2 est capable de détecter le muramyldipeptide (MDP), un composant de la paroi bactérienne, ce qui ... [more ▼]

Le récepteur cytoplasmique NOD2 est l'un des membres les mieux caractérisés de la famille des NLRs. NOD2 est capable de détecter le muramyldipeptide (MDP), un composant de la paroi bactérienne, ce qui induit les différentes cascades de signalisation conduisant à l'activation de NF-κB, des MAPKs et de l'autophagie. Ces voies contribuent à une réponse immunitaire innée et adaptative efficace. La perte de fonction des mutants NOD2 a été associée à une plus grande susceptibilité à la maladie de Crohn, ce qui souligne l'importance physiologique de la régulation de l'activité de NOD2. Nous avons effectué une étude par une approche protéomique pour rechercher de nouveaux régulateurs de NOD2. Nous avons généré un modèle cellulaire pour cette étude, les cellules HEK293GNV. Nous avons identifié plusieurs nouveaux partenaires de NOD2, dont la protéine JNKBP1 (c-Jun N-terminal kinase binding protein 1), une protéine scaffold caractérisée par un domaine WD40 en amino-terminal. Nous avons aussi débuté la caractérisation d’autres protéines appartenant aux complexes NOD2 purifiés comme ROCK2 (Rho activated kinase 2) et HDAC5 (Histone deacetylase 5). Au vu de nos premiers résultats, les protéines ROCKs sembleraient être des activateurs de la voie NOD2. Nous nous sommes principalement consacrés à l’étude de JNKBP1 qui a été identifiée, en 1999, comme un partenaire et un régulateur positif de JNK. Nous avons montré que JNKBP1 via son domaine WD40, se lie à NOD2 suite à l’activation par le MDP. Cette interaction atténuait l'activation de NF-κB dépendante de NOD2, la synthèse de l'IL-8 et l’activité antibactérienne de NOD2. JNKBP1 exerçait son effet répresseur en perturbant l’oligomérisation NOD2 et la phosphorylation de la tyrosine de RIP2 : deux étapes nécessaires à la signalisation en aval. En outre, nous avons montré que JNKBP1 et NOD2 étaient exprimées dans l'épithélium intestinal humain et dans les cellules immunitaires recrutées dans la lamina propria, ce qui suggère que JNKBP1 contribuerait au maintien de l'homéostasie intestinale dépendante de NOD2. [less ▲]

Detailed reference viewed: 23 (11 ULg)
Full Text
See detailStructure and Lattice Dynamics of Bismuth Telluride Nanostructures
Bessas, Dimitrios ULg

Doctoral thesis (2012)

A brief outline of experimental lattice dynamics related to thermal transport in solids introduces this thesis. The introduction is followed by three chapters dedicated to structure and lattice dynamics ... [more ▼]

A brief outline of experimental lattice dynamics related to thermal transport in solids introduces this thesis. The introduction is followed by three chapters dedicated to structure and lattice dynamics of bulk and nanostructured bismuth telluride, a chapter on lattice instabilities observed in bulk EuTiO3 around room temperature, and a chapter on the development of a resonant ultrasound spectrometer for small samples. First, the lattice dynamics in bulk Bi2Te3 and Sb2Te3 were investigated by nuclear inelastic scattering, diffraction of high energy synchrotron radiation and calorimetry. In combination with earlier inelastic neutron scattering data, the element specific density of phonon states was extracted not only for Te and Sb but also for Bi. The Bi-Te bonding in Bi2Te3 is fundamentally different than the Sb-Te bonding in Sb2Te3. It appears that the Te specific density of phonon states is mostly unaffected upon substitution of Sb with Bi. Phonon polarization analysis was conducted in a Bi2Te3 single crystal. The observed low lattice thermal conductivity in bulk Bi2Te3 and Sb2Te3 results essentially from the small acoustic cut off energy. Second, the lattice dynamics in elemental modulated Sb2Te3 films were studied by nuclear inelastic scattering and diffraction of high energy synchrotron radiation. These studies reveal that the main features in the Sb specific density of phonon states arise from the layered structure. The extracted average speed of sound is practically the same as in bulk Sb2Te3. The impact of the acoustic cut off energy is further highlighted. Third, the phonon confinement in a Bi2Te3 nanowire array was studied by nuclear inelastic scattering, diffraction of high energy synchrotron radiation, scanning as well as transmission electron microscopy. For the first time the element specific density of phonon states was measured on nanowires in two perpendicular orientations. The much lower than in bulk average speed of sound measured in 56 nm diameter nanowires is directly related to the confined dimensions. The related 50 % decrease in macroscopic thermal conductivity is in line with macroscopic measurements on similar nanowires. Fourth, a detailed structural and lattice dynamical investigations of the bulk cubic perovskite EuTiO3 revealed a lattice instability close to room temperature. The low temperature phase is associated with anharmonic europium displacement and has a significant impact in the lattice dynamics. Last, a resonant ultrasound spectrometer for measurements on small samples and thin films was developed. Successful measurements versus temperature of the elastic constants were carried out with sub-percentage accuracy on oriented single crystals smaller than 1 mm3. [less ▲]

Detailed reference viewed: 116 (11 ULg)
Full Text
See detailBiologie et Ecologie du Martin- pêcheur huppé (Alcedinidae : Alcedo cristata, PALLAS 1764) de la région de Kinshasa: habitat, tactique alimentaire et reproduction.
Kisasa Kafutshi, Robert ULg

Doctoral thesis (2012)

Pour expliquer la rareté de sites de nidification du Martin-pêcheur huppé dans la région de Kinshasa, trois hypothèses ont été successivement testées au cours de ce travail. Une première hypothèse ... [more ▼]

Pour expliquer la rareté de sites de nidification du Martin-pêcheur huppé dans la région de Kinshasa, trois hypothèses ont été successivement testées au cours de ce travail. Une première hypothèse suggérait que le choix de son habitat de reproduction résulterait d’un compromis entre le taux de survie de ses nids, de son succès reproducteur et de la qualité des sols utilisés pour la construction des nids. Le résultat obtenu a révélé qu’un sol propice à l’excavation est constitué de 10,8 ± 6,1% de limon, 7,5 ± 6,6% d’argile et de 81,4 ± 11,4% de sable. Par contre les falaises dont les sols sont constitués en moyenne de 8,5±5,6% de limon ; 11,6±6,5% d’argile et de 78,9±13% de sable, étaient soit abandonnées, soit non occupées. Il semble que la teneur en argile pour un sol favorable chez la plupart des oiseaux nichant dans le terrier est généralement inférieure à 10%. Une différence d’environ 1% de teneur en argile, en comparaison avec les falaises abandonnées ou sans nids dans la région, nous a paru inconcevable pour relier l’absence des nids dans certains habitats naturels avec la dureté des sols. La seconde hypothèse confirme le rôle de la relation structure fonction à partir des suivis réguliers de 138 poussins de l’éclosion à la sortie des nids. Le résultat obtenu montre que la croissance et le développement des organes expliquent le patron de consommation de l’espèce et les paramètres plus ou moins importants à la survie de l’espèce en milieux urbanisés (Kisasa Kafutshi sous presse). Et enfin, la troisième hypothèse suggère que le choix de proies à capturer par les adultes dépendrait des exigences des poussins et leur disponibilité dans le site. Pour toute la durée d’élevage, la consommation d’une nichée a été estimée à environ 17 proies. Il s’agissait des insectes, des grenouilles et de poissons de tailles variant de 2-6,5cm. Nous avons montré que le Martin-pêcheur huppé module le choix de son habitat de reproduction non seulement en fonction de la texture du sol des falaises (Kisasa Kafutshi & Aloni Kumanda 2011), de la disponibilité des proies (Kisasa Kafutshi 2012a), mais surtout de la chance de survie de ses nids d’une année à l’autre (Kisasa Kafutshi 2012b). [less ▲]

Detailed reference viewed: 90 (5 ULg)
Full Text
See detailLes iguanodons de Bernissart: leur évolution diagénétique et les processus de dégradation
Leduc, Thierry ULg

Doctoral thesis (2012)

About thirty complete articulated skeletons of iguanodons have been excavated from Bernissart. This unique collection is conserved at the RBINS. The bones excavated were the object of diverse physical and ... [more ▼]

About thirty complete articulated skeletons of iguanodons have been excavated from Bernissart. This unique collection is conserved at the RBINS. The bones excavated were the object of diverse physical and chemical treatments to protect them from their degradation. These bones were not the object of detailed mineralogical analyses allowing to understand either diagenetic mechanisms involved or to understand the specific mechanisms of their change. This work thus aims at filling this lack. It integrates petrographic (POM, SEM), mineralogical (DRX, Raman Spectroscopy) and chemical (EDS, X-ray fluorescence, microprobe) techniques. By these methods, 30 different minerals were identified. The diagenesis of Iguanodon bones is the result of cumulative physical, chemical and biological processes that will modify the original chemical and/or structural properties of this organic object. Bone diagenesis is a complex process that includes the degradation of organic matter, the dissolution and recrystallization of bone apatite, the enrichment in trace elements, the precipitation of new minerals in the bone cavities (permineralisation), the fracturation process. A plan is proposed positioning in a relative timescale minerals formed during 3 diagenetic stages and the degradation processes engaged following the bones exhumation. During burial variable recrystallisation took place: the slightly crystallized carbonated hydroxylapatite (the mineral phase of fresh bone tissue) was replaced by well crystallized carbonated fluorapatite currently present in the Iguanodon bones. Whereas some minerals infiltrated in the bone during cavity filling by the sediment (“mainly” quartz, “argillaceous” phyllosilicates), others are authigenic and precipitated in the cavities during burial (pyrite, barite, sphalerite, celestine, iron oxi-hydroxides, authigenic apatite, calcium sulfate and to a lesser extent vivianite). Pyrite is the most abundant authigenic mineral in the Iguanodon fossil bones. It occurs in different morphologies (crystals, framboids, sticks, fibroradial structure, thin coating…). Four kind of pyrite were determined according to the diagenesis phase during which they were formed and the source of iron and sulfur. Besides pyrite barite is the second most abundant phase. When both minerals are present pyrite has been formed first. The distribution of these minerals within bones is more controlled by micro-environments than by particular structure of the bone. Since their discovery the Iguanodon fossil bones were treated for conservation in several ways. This however did not prevent the alteration of pyrite into an assemblage of 16 different secondary minerals. The ferrous sulfates (szomolnokite and rozenite) are the most abundant of these minerals and can be found in nearly all samples sulfatized. Other sulfates were formed as the result of alteration of the wealdian shale by acid produced by pyrite oxidation: e.g. tschermigite, natrojarosite and halotrichite. Gypsum, anhydrite, iron phosphate and diadochite are the result of dissolution of bone apatite. The variations of relative humidity in collections and in showrooms are responsible for the pursuit of the bones degradation (sulfatation of the residual sulfides ; fracturing by dilation / contraction). The relative humidity, conjugated to the temperature variations are the parameters to be controlled for a better preservation of these invaluable fossils. Techniques implementing some chemicals products proposed in the literature are applicable only to certain objects of limited size. [less ▲]

Detailed reference viewed: 84 (13 ULg)
Full Text
See detailAux origines de la métaphysique : l'interprétation par Alexandre d'Aphrodise de la "Métaphysique" d'Aristote
Guyomarc'h, Gweltaz ULg

Doctoral thesis (2012)

Le terme de « métaphysique » ne se lit pas chez Aristote. Les livres rassemblés sous ce titre ne cessent d'interroger leurs lecteurs quant à leur unité. La science ainsi désignée, enfin, semble ... [more ▼]

Le terme de « métaphysique » ne se lit pas chez Aristote. Les livres rassemblés sous ce titre ne cessent d'interroger leurs lecteurs quant à leur unité. La science ainsi désignée, enfin, semble contrevenir aux règles communes de la scientificité aristotélicienne. Désigner Aristote comme le « fondateur de la métaphysique » fait dès lors problème. L'hypothèse du présent travail est que cette fondation engage l'œuvre des commentateurs d'Aristote, au premier chef desquels se situe Alexandre d'Aphrodise. L'Exégète par excellence ouvre la possibilité de « faire de la métaphysique » sans que cela signifie seulement commenter Aristote. Alexandre travaille en effet à faire de la Métaphysique un livre et à instituer la métaphysique une science une. Selon l'Aphrodisien, la métaphysique est cette science à la fois universelle et première, à la fois science modèle et fondatrice des autres sciences. Elle s'articule en trois programmes principaux : l'étude générale de l'étant en tant qu'étant, celle de la substance et celle enfin de la cause première. Ces trois programmes sont distincts, mais coordonnés et suffisamment proches pour ne pas pouvoir être étudiés par une autre science, ni éclatés entre diverses sciences. Ils progressent à chaque fois par un passage d'une généralité à son maximum et sa cause. Ainsi la substance est-elle cause de l'être des autres étants et étant au maximum. Ainsi la cause première est-elle intelligible au plus haut point et cause de l'intelligibilité du monde. L'Exégète offre une interprétation forte de l'unité de la Métaphysique et de celle de la science correspondante. C'est dans et par cette reprise que les écrits du Stagirite sont devenus proprement fondateurs. [less ▲]

Detailed reference viewed: 53 (5 ULg)
Full Text
See detailDownmodulator role of SHIP-1 in NOD2 signaling
Condé, Claude ULg

Doctoral thesis (2012)

Detailed reference viewed: 29 (13 ULg)
Full Text
See detailCatchment modelling and sensitivity analysis to spatial interpolation methods of daily rainfall
Ly, Sarann ULg

Doctoral thesis (2012)

Spatial interpolation of precipitation data is of great importance for hydrological modelling. Geostatistical methods (kriging) are widely applied in spatial interpolation from point measurement to ... [more ▼]

Spatial interpolation of precipitation data is of great importance for hydrological modelling. Geostatistical methods (kriging) are widely applied in spatial interpolation from point measurement to continuous surfaces. The objective of this dissertation is to confront the performances of the several spatial interpolation methods, in particular the geostatistics for daily rainfall data in the nested catchments to realize a sensitivity analysis on discharges modelled at the outlets to the daily rainfall input in the modelling. The previous studies in the literature emphasized a requirement of novel investigation on the essential means to recover the rainfall data and eventually, the quality of the hydrological modelling. This study leaned on 30-year daily rainfall data of 70 raingages in the hilly landscape of the Ourthe and Ambleve catchments in Belgium (2908 km²). Two common deterministic methods are employed here. The Thiessen Polygon (THI) assigns the value from the nearest observation to a certain grid cell. The Inverse Distance Weighting (IDW) is an advanced nearest neighbour approach that allows including more observations than only the nearest points. The value at a certain grid cell is obtained from a linear combination of the surrounding locations. In the geostatistical algorithms, the spatial variation may be better described by a stochastic function. Four versions of kriging are used. The Ordinary Kriging (ORK) is the basic form of Kriging that the prediction is also a linear combination of the measured values. But the spatial correlation between the data, as described by the variogram, determines the weights, assuming that the mean is constant but unknown. The Universal Kriging (UNK) is based on the hypothesis that this mean is a polynomial function of spatial coordinates. So, this type of kriging is not stationary with regard to the mean. The Kriging with External Drift (KED) supposes that the mean of the interest variable depends on auxiliary variables; the theory of this kriging is in fact the same as the theory of UNK, which also contains a non-constant mean. The drift is defined externally through some auxiliary variables. The Ordinary Cokriging (OCK) suggests estimating the variable of interest by weighted linear combination of its observations and the observations of the auxiliary variables. This technique requires the study of the spatial dependence between variables besides the study of the simple spatial dependences. All types of kriging use a variogram model to characterise spatial correlation. A variogram describes in terms of variances how spatial variability changes as a function of distance. Seven semi-variogram models (logarithmic, power, exponential, Gaussian, rational quadratic, spherical and penta-spherical) were fitted to daily sample semi-variogram on a daily basis. These seven variogram models were also adopted to avoid negative interpolated rainfall. The elevation, extracted from a digital elevation model, was incorporated into multivariate geostatistics. Seven validation raingages and cross validation were used to compare the interpolation performance of these algorithms applied to different densities of raingages. The areal rainfalls are calculated for the catchment area and used for analysis of extreme rainfall. The effects of the interpolation methods on the extreme rainfall are analysed. The interpolated rainfalls are also used as rainfall input of the physically-based and distributed EPIC-GRID model. The long series of model results are analysed by comparison with the observed discharges at the different outlets of the catchments. Then, the extreme discharges at the outlets are computed. All of these investigations always take into account of the raingage density and the raingage position for very sparse raingage cases. The main results show that among the methods based on the only rainfall data, the geostatistics and IDW are the best ones. The performances change according to the density of the raingages. For the extreme rainfall and long term modelling results, no big difference is found for a high density of raingage but large difference are found for the case of the scattered raingage. For the latter case, UNK and KED are very sensitive to the position of the raingages. IDW, ORK and OCK are found to be the best performance. However for the extreme flow, KED and OCK is the best whereas IDW is not better for the high density of the raingages. For the case of the scattered raingages, the difference in extreme discharge between the interpolation methods is very large and larger than shown in the extreme rainfall and the long term modelling results. IDW, ORK and OCK always perform better. UNK and KED still are sensitive to the positions of raingages. The index of position is used to describe the form of polygon defined by the four raingages. This index is defined as the relation between the polygon perimeter and a circle perimeter having an area equivalent to that of the polygon. The best raingage position for all interpolation methods used in this research should be arround the catchment area, its index should be close to one. [less ▲]

Detailed reference viewed: 87 (13 ULg)
Full Text
See detailLorsque les limites des sciences et les sentiers de chasse s’entrecroisent: Une ethnographie des laboratoires scientifiques amazoniens en partenariat avec les communautés autochtones locales
Escobar Jimenez, Kelly ULg

Doctoral thesis (2012)

Currently, protected areas and protected natural species are in a state of proliferation all over the world. Landscapes, flagship species, peoples in voluntary isolation, ecosystems, and “biological ... [more ▼]

Currently, protected areas and protected natural species are in a state of proliferation all over the world. Landscapes, flagship species, peoples in voluntary isolation, ecosystems, and “biological corridors” are all protected. In order to achieve this, categories of protection at different geographical levels have been mobilized. The processes that allow any one of these categories to become operational within a precise territory are more or less well standardized and have in common, amongst others things, two components that have caught my attention: Firstly, the central role of previous scientific and technical studies, and secondly, the desire to ensure the participation of the populations concerned. How are relations between scientists and the non-scientific public in participatory environmental management? This thesis seeks to answer this question, from the starting point of an analysis of the cognitive dimension of participatory environmental management, i.e. how the production of knowledge affects the modes of existence within protected areas (and consequently their human and nonhuman inhabitants). Building upon the study of daily activities that bring scientists and indigenous peoples into contact in and around the scientific field stations “Yasuní” and “Juri Juri Kawsay” (in the Ecuadorian Amazon), this research describes the relationship between ways of knowing a conflicting object (for example a natural species, a territorial boundary, an isolated people) and the consequences in terms of configuration of that object (in terms of identity, value, and fragility) and its management (administration, use, protection, recovery or abandonment). By mobilizing the approach of Actor-Network theory, this dissertation attempts to outline how mediation between humans and nonhumans, non-scientific and scientific, occurs. It also offers a reflection on how the Agency of an entity (the competence to make make distributed in the humans and nonhumans actors) comes to influence the joint actions. This research can capture the ambiguity, instability, resistance and complexity that still exist in the Amazon, with some unexpected findings along the way, by showing the changes among things and people throughout development projects, land management initiatives, and conservation and science programs. After describing the trajectory of four entities (laboratories, species conservation, territories and subjects), which meet at the Amazonian interfaces where science, conservation and development are in competition, the findings of this dissertation have met two ambitions: to consider the importance of taking into account the complexity and historicity of scientific data and to answer a broader question: What are the relevant factors to take into account when considering the possibilities for joint action between scientists and indigenous populations? [less ▲]

Detailed reference viewed: 58 (20 ULg)
Full Text
See detailApprentissages automatiques supervisés pour le monitoring environnemental et énergétique d'une chaudière de régénération
Sainlez, Matthieu ULg

Doctoral thesis (2012)

The broad objective of this thesis is to apply and compare supervised learning techniques for prediction of nitrogen oxide pollutant emission from the recovery boiler of a Kraft pulp mill. In this task ... [more ▼]

The broad objective of this thesis is to apply and compare supervised learning techniques for prediction of nitrogen oxide pollutant emission from the recovery boiler of a Kraft pulp mill. In this task, we want to highlight a technique that is most suited and self-adapted to boiler transient operating conditions. The Kraft process is an alkaline process to produce chemical pulp; cellulose fibers are dissociated from lignin by cooking the chips in a solution of sodium hydroxide (NaOH) and sodium sulfide (Na2S), called white liquor. The residual black liquor is concentrated and burned in a recovery furnace to yield an inorganic smelt of sodium carbonate (Na2CO3) and Na2S. The recovery boiler both regenerates the cooking chemicals and produces high pressure steam to the pulp mill, but the boiler is a major source of atmospheric pollutants in the mill. In particular nitrogen oxide formation is very complex because of several chemicals and dynamic mechanisms: thermal NOx, prompt NOx and fuel NOx. Nowadays, there is an increasing demand in such industries for efficient data analysis tools, especially for pollutant monitoring and/or energy management. Literature reviews refer mainly on numerical solutions where a complete description of the process is needed and where stationary condition is often a working hypothesis. This is the case with the advanced data validation and reconciliation techniques that we evaluate. This technique is based on thermodynamic models, chemical and physical relationships within process parameters and equipment. This is helpful to highlight some lack of information about the process, but this approach failed to model accurately steam and fumes utilities operating points. Indeed, in a Kraft recovery boiler, the total nitrogen oxide emission is dependent on several operating factors and heterogeneous conditions, e.g. operating fuels (black liquor or heavy fuel), furnace load, droplet size, air system operation, retention time, biomass characteristics,... For such a complex problem, machine learning techniques may be used as alternative methods in engineering analysis and predictions. They involve algorithms that improve automatically through experience collected in historical databases. Among supervised learning techniques, we focus mainly on neural networks methods (static and dynamic architectures) and additionally on tree-based (regression tree and random forests) and linear ones. For each method, we evaluate its ability to predict NOx pollutant emission in varying conditions. A random forest is a collection of uncorrelated regression trees, induced from bootstrap samples of the training data. Its internal estimates are also used to measure variable importance and allow us to classify relevant variables for a model inputs selection task. Note that we need some additional a priori knowledge to select the final inputs set. Among static neural network structures, the multilayer perceptron is the most widely used, particularly the two-layer structure in which the input units and the output layer are interconnected with an intermediate hidden layer. The model of each neuron in the network includes a nonlinear activation function that is differentiable; this network can perform static mapping between an input space and an output space. Within dynamic architectures, we distinguish those that have only feed-forward connections and those that have feedback (recurrent) connections. In this work, we focus mainly on NARX network (Nonlinear AutoRegressive model with eXogenous inputs) and additionally on Elman recurrent neural network. This last one incorporates an additional layer, called context layer, the nodes of which are the one-step delay elements embedded into the local feedback paths. Nevertheless, Elman's approach has some drawbacks associated with learning parameters scheme and temporal gradient approximation. Particularly, the NARX network is used for input-output modeling of nonlinear dynamical systems. It is a recurrent model: model inputs are applied to a tapped-delay-line memory of n units and outputs are fed back to the input layer through another line of m units. The total model order s=n+m is therefore a key parameter and the method of Lipschitz numbers is a tool for estimating it. An advantage of NARX is that we can use standard backpropagation algorithm for neural network learning scheme. Furthermore, to increase model robustness, we average neural predictions over a set of individual neural predictors, this is helpful for reducing variance prediction across trials. Despite the fact that generalization is done on the worst case configuration possible, we see that ensemble of NARX networks perform well on predicting NOx emissions during transient operations and Lipschitz numbers are very helpful for system orders estimations. We illustrate the potential of a dynamic neural approach compared to the others in the nitrogen oxide prediction task. It is more suited to practical modeling needs and offers a modeling of time and memory. It allows us to monitor NOx pollution and possibly adjusting control variables and performing diagnostics. The thesis is divided into seven chapters covering several publications. Chapter 1 is about the Kraft process and its recovery boiler. We start with a short description of the Kraft pulp mill. Then we describe the Kraft recovery boiler, some chemical reactions in the furnace, the steam production equipments and the atmospheric pollutants. Finally we discuss about nitrogen oxide formation in the furnace, the effects of several operating conditions on its production. Chapter 2 is about data mining, on what it is, on what it is used for and which are the main modeling cultures. This chapter deals with system identification, modeling approaches (white box, grey box, black box), some definitions about learning and modeling, and finally some links between modeling and optimization techniques. Chapter 3 starts with a state-of-the-art about numerical simulation of a Kraft recovery boiler, then we apply and evaluate a data validation scheme for steam and fumes utilities modeling. Finally we discuss the application of artificial intelligence techniques within the framework of a recovery boiler. Chapter 4 aims at selecting model inputs, starting with a supervised selection approach based on random forests. We introduce some methodological insights about tree-based methods, from a simple regression tree to random forests. Random forests internal estimates are used to measure the relative importance of each input variable in predicting a response, i.e. nitrogen oxide emission or high pressure steam production. Finally we discuss about some useful extra knowledge to take in account for the selection of final inputs. Chapter 5 is about neural networks modeling, we introduce the perceptron, the multilayer perceptron, and the associated backpropagation algorithm. We discuss about static and dynamic architectures, especially the Elman recurrent neural network. Finally, we apply a multilayer perceptron and an Elman recurrent neural network for predicting the high pressure steam flow rate from the Kraft recovery boiler. Chapter 6 presents some insights about input-output modeling of nonlinear dynamical systems, especially with NARX network. At the end, we explain the Lipschitz method that is applied for system orders estimation. Chapter 7 summarizes some comparison results about supervised learning techniques applied to predict nitrogen oxide pollutant emission from the recovery boiler. This comparison involves neural network techniques, tree-based methods and multiple linear regression. Finally, some research perspectives are presented and some conclusions are drawn. [less ▲]

Detailed reference viewed: 45 (7 ULg)
Full Text
See detailElectrografting on nanoparticles: A new way toward polymer stabilized nanoparticle suspensions
Serwas, Harry ULg

Doctoral thesis (2012)

Abstract: Nowadays, nanomaterials keep sparking interest tremendously because of the unique properties materials exhibit at the nanoscale. However, the stabilization of nanoparticles against aggregation ... [more ▼]

Abstract: Nowadays, nanomaterials keep sparking interest tremendously because of the unique properties materials exhibit at the nanoscale. However, the stabilization of nanoparticles against aggregation is a prerequisite to exploit their remarkable properties, since they are very prone to aggregation. Moreover, even if many synthetic methods have been reported to prepare nanoparticles, achieving an efficient and convenient stabilization, without an alteration of the properties nanoparticles remains a challenge up to now. Therefore, a novel approach toward polymer stabilized metal based nanoparticles was developed using sonoelectrochemistry combined to electrografting to form a protective polymer layer in-situ directly on the generated particles. Nanopaticles prepared using this new approach were characterized. The influence of major experimental parameters on the characteristics of the produced polymer coated particles was also studied. [less ▲]

Detailed reference viewed: 49 (12 ULg)
Full Text
See detailEvénements de santé et transition à la retraite des seniors en Belgique. Une approche biographique
Banturiki, Yannick Védaste ULg

Doctoral thesis (2012)

La thèse de Mr. Banturiki porte sur une analyse socio-démographique réalisée dans une perspective biographique mettant en relation des événements vécus dans le parcours de vie et la transition à la ... [more ▼]

La thèse de Mr. Banturiki porte sur une analyse socio-démographique réalisée dans une perspective biographique mettant en relation des événements vécus dans le parcours de vie et la transition à la retraite des seniors en Belgique. L’une des approches novatrices de ce travail est la conceptualisation d’un événement de santé en vue de sa collecte dans les biographies individuelles. S’appuyant sur le paradigme des parcours de vie, ce travail se veut une contribution dans la compréhension de l’incidence que peuvent avoir des événements vécus tout au long de la vie sur le risque de connaître une sortie d’une activité salariée chez les seniors. [less ▲]

Detailed reference viewed: 45 (6 ULg)
Full Text
See detailLe sommeil chez les patients en état de conscience altéré
Cologan, Victor ULg

Doctoral thesis (2012)

Cet ouvrage décrit les études réalisées sur le sommeil des patients cérébro-lésés en état de conscience altérés et présente nos travaux effectués chez les patient en état végétatif et en état de ... [more ▼]

Cet ouvrage décrit les études réalisées sur le sommeil des patients cérébro-lésés en état de conscience altérés et présente nos travaux effectués chez les patient en état végétatif et en état de conscience minimale. Les conclusions supportent l'intérêt neurophysiologique mais aussi diagnostique et pronostique de l'examen du sommeil chez ces patients. [less ▲]

Detailed reference viewed: 106 (17 ULg)
Full Text
See detailUse of intercropping and infochemical releasers to control aphids in wheat
Zhou, Haibo ULg

Doctoral thesis (2012)

Detailed reference viewed: 48 (12 ULg)
Full Text
See detailSymmetries of the scalar sector of multi-Higgs-doublet models
Keus, Venus ULg

Doctoral thesis (2012)

In pursuit of the origin of the masses of particles in the Standard Model, the Brout- Englert-Higgs Mechanism predicts the existence of a scalar boson, whose discovery has been the main goal of the Large ... [more ▼]

In pursuit of the origin of the masses of particles in the Standard Model, the Brout- Englert-Higgs Mechanism predicts the existence of a scalar boson, whose discovery has been the main goal of the Large Hadron Collider. However, introducing this scalar boson does not provide the answer to all inadequacies of the Standard Model. Many different Beyond Standard Model theories have been proposed in order to explain these anomalies. Multi-Higgs-doublet models are among these models. We restrict ourselves to the scalar sector of multi-Higgs-doublet-models. The huge number of free parameters in the scalar potential in these models, makes it impossible to study the most general case for any N. In order to reduce the number of free parameters, one could impose symmetries on the scalar potential. Therefore, it is important to explore which symmetries can be implemented in the scalar sector, how these symmetries are broken, how they could be encoded in the Yukawa sector and what the resulting properties of the fermions are. Classifying these symmetries in the scalar sector is the main focus of this thesis. We have found certain symmetries that are always broken in models with more than two doublets, which we name ”frustrated symmetries”. Examples of such symmetries are presented in 3HDM, and one particular symmetry, the octahedral symmetry, is studied further. This symmetry seems to be the largest realizable discrete symmetry that can be imposed on the scalar sector in 3HDM, and interestingly results in a 2HDM-like mass spectrum. In the attempt towards the classification of possible symmetries in the scalar sector of the NHDM, we find that these symmetry groups are either subgroups of the maximal torus, or certain finite Abelian groups which are not subgroups of maximal tori. For the subgroups of the maximal torus, we present an algorithmic strategy that gives the full list of possible realizable Abelian symmetries for any given N . We extend this strategy to include Abelian antiunitary symmetries (with generalized CP transformations) in NHDM. We also show that multi-Higgs-doublet models can naturally accommodate scalar dark matter candidates protected by the group Zp , since these groups are realizable in NHDM. These models do not require any significant fine-tuning and can lead to a variety of forms of microscopic dynamics among the dark matter candidates. [less ▲]

Detailed reference viewed: 67 (15 ULg)
See detailApprocher la médiation par ses usages professionnels. Le cas de l'art-thérapie
Vandeninden, Elise ULg

Doctoral thesis (2012)

La médiation est une notion aujourd’hui centrale dans de nombreuses recherches en SIC : elle est mobilisée en tant que concept permettant de décrire la spécificité de dispositifs communicationnels ... [more ▼]

La médiation est une notion aujourd’hui centrale dans de nombreuses recherches en SIC : elle est mobilisée en tant que concept permettant de décrire la spécificité de dispositifs communicationnels tripartites mais aussi comme problématique susceptible d’interroger autrement certains objets. Les domaines d’étude privilégiés par les chercheurs relèvent traditionnellement des champs de la culture ou des médias et techniques. Dans le premier, la notion de médiation désigne le réseau d’intermédiaires reliant l’œuvre au public ; le travail des analystes consiste alors à faire apparaître « les médiations » auparavant invisibles. Dans le second, le terme renvoie à un « objet intermédiaire » qui s’insère dans les relations humaines et substitue le rapport objectal au rapport intersubjectif. Dans ces deux domaines, il est question d’un contact différé, espacé. Les usages professionnels de la médiation - ceux qui renvoient, par exemple, aux divers métiers de « médiateurs » - sont, en revanche, très peu interrogés par les chercheurs en SIC. Ils se caractérisent par un recours au terme de médiation comme stratégie de communication. Son processus renvoie à l’insertion d’un « tiers humain » dans des relations intersubjectives souvent décrites comme conflictuelles. Ce qui distingue ces derniers usages de ceux traditionnellement investigués en SIC, c’est donc ce tiers « incarné » et la confrontation directe des sujets. Cette recherche s’attache à comprendre d’une part les raisons de ce désintérêt des chercheurs en SIC pour des pratiques professionnelles pourtant reconnues socialement, d’autre part la spécificité de l’activité du « tiers humain ». Afin d’explorer le fonctionnement de cette dernière, nous avons opté non pour l’étude d’un médiateur « nommé » tels que ceux qui exercent dans les domaines juridique, familial, entrepreneurial ou encore scolaire mais pour le « cas » des psychothérapies médiatisées dont « l’art-thérapie » fait partie. Si cet objet d’étude nous a semblé intéressant, c’est que son articulation avec la notion de médiation « fait problème ». C’est à un texte de Jean-Claude Passeron et de Jacques Revel (2005) qu’il faut se référer pour décrire la particularité de notre travail : « Penser par cas. Raisonner à partir de singularités ». Ils y décrivent cette démarche qui consiste à s’appuyer sur la richesse d’un objet pour mettre des outils théoriques à l’épreuve, non pas pour illustrer la théorie (cela reviendrait alors à mobiliser le « cas » comme « exemple ») mais pour l’interroger : « c’est, à dire vrai, l’ensemble des questions dont on l’investit – et dont il est susceptible d’être investi – qui fait le cas » (p. 11). Ainsi, nous envisageons la façon dont le « cas » de l’art- thérapie interroge la définition de la médiation : comment les visions des professionnels mettent en cause les conceptions des chercheurs en SIC mais aussi de quelle façon les différents modes d’appréhension possibles (approche à partir des discours ou des situations) appellent l’instauration d’un cadre de perception nouveau, apte à mettre en relation les éléments disjoints révélés par l'étude du cas. [less ▲]

Detailed reference viewed: 98 (28 ULg)
Full Text
See detailTrace elements and stable isotopes during lactation and post-weaning fast in phocids
Habran, Sarah ULg

Doctoral thesis (2012)

Haul-out periods in most phocids are particularly intense from a physiological point of view since they involve extended fasting periods associated with behaviours or processes resulting in considerable ... [more ▼]

Haul-out periods in most phocids are particularly intense from a physiological point of view since they involve extended fasting periods associated with behaviours or processes resulting in considerable energy expenditure (e.g., combat, mating, lactation, moulting). The substantial tissue reorganization during these key periods can entail the mobilization of potentially associated contaminants, such as trace elements and persistent organic pollutants. The main objectives of this study were firstly to investigate the effects of fasting, lactational, and developmental phases on trace element concentrations (Cd, Cr, Cu, Fe, Hg, Ni, Pb, Se, V, and Zn) in the northern elephant seal (Mirounga angustirostris) and the grey seal (Halichoerus grypus), and on the other hand, to assess the maternal transfer of trace elements to the offspring. Changes in the diet indicators – the carbon and nitrogen stable isotopes (δ13C and δ15N) – were also investigated throughout lactation and post-weaning fast, and their implications were developed. Different tissue samples (blood, blubber, hair, and milk) were collected repeatedly in mother-pup pairs and weaned pups in northern elephant seals and grey seals during three longitudinal fieldworks in the breeding season. Related to the remobilization of resources during lactation and pup development, short-term variations in blood concentrations of trace elements were highlighted in this study. The results imply a careful consideration of the physiological status of marine mammals when using blood in the framework of biomonitoring of trace element contamination. Although the total body burdens of trace elements decreased over lactation in adult females, circulating concentrations of some metals, like Hg, increased significantly, drawing attention to the potential adverse effects on the immune, endocrine or nervous systems in adults. Northern elephant seals and grey seals are exposed to trace elements from the first stages of development through the placenta and through the milk. Indeed, concentrations in pup hair of both species revealed a large accumulation of all assayed trace elements during the foetal development. The maternal transfer of trace elements adds to lactational transfer of others chemicals such PCBs, PBDEs, and OCPs reported in recent studies. Immunotoxic and endocrine risks related to chemical mixtures remain unclear until now and may therefore affect phocids at a crucial period of their immune development. [less ▲]

Detailed reference viewed: 85 (29 ULg)
See detailUn milieu graphico-cinématique pour l’apprentissage des dérivées dans une praxéologie "modélisation" : potentialités et limites
Gantois, Jean-Yves ULg

Doctoral thesis (2012)

Ce travail concerne l’apprentissage du calcul des dérivées tel qu’étudié chez des élèves de 16-17 ans aux prises avec des questions mobilisant des mouvements rectilignes, leurs vitesses variables ou non ... [more ▼]

Ce travail concerne l’apprentissage du calcul des dérivées tel qu’étudié chez des élèves de 16-17 ans aux prises avec des questions mobilisant des mouvements rectilignes, leurs vitesses variables ou non et les graphiques de leurs lois de position.
On y analyse ces questions comme composantes d’un milieu et les formes embryonnaires que prend le savoir construit dans ce contexte. Cette recherche illustre en outre en quoi consiste une praxéologie de type « modélisation » et le type particulier de discours technologique susceptible de justifier les techniques mises au point à ce stade. [less ▲]

Detailed reference viewed: 35 (7 ULg)
Full Text
See detailTailor-made degradable copolymers for the design of advanced drug delivery systems
Cajot, Sébastien ULg

Doctoral thesis (2012)

Over the last decades, polymer micelles have attracted an increasing interest in drug pharmaceutical research because they could be used as efficient drug delivery systems. The goal of this thesis was ... [more ▼]

Over the last decades, polymer micelles have attracted an increasing interest in drug pharmaceutical research because they could be used as efficient drug delivery systems. The goal of this thesis was centered on the design of new smart nanocarriers and more particularly on the basis of reversibly redox-cross-linked polymer micelles. The first part of that work was dedicated to the synthesis of new macromolecular architectures associating biodegradable hydrophobic polymers such as polyester (e.g. PCL), polycarbonate (e.g. PTMC) or also polyphosphate (e.g. PBODOP) and the water soluble poly(ethylene oxide) (PEO) frequently used due to its biocompatible properties. Well-defined block copolymers have been synthesized by ring-opening polymerization. The second part of that work focused on the cross-linking of the hydrophobic block in order to obtain well stabilized micelles. The copolymerization of α-chloro-ε-caprolactone (αClεCL) allows to easy functionalize the hydrophobic block in order to reversibly cross-link the future micelle core by the addition of a disulfide bearing cross-linker. The self assembly of theses copolymers and redox-dependent micellization behaviours have been studied by diffusion light scattering and transmission electronic microscopy. Finally, the potential of these redox-sensitive micelles as active drug delivery system has been analysed by investigating their stealthy behaviours using the complement activation (CH50) test, their cytotoxicity, their cellular internalization and also the redox-sensitive profile of a hydrophobic dye. [less ▲]

Detailed reference viewed: 40 (17 ULg)
Full Text
See detailEtude longitudinale de la motivation d'étudiants universitaires de 1ère année
Mignon, Jacques ULg

Doctoral thesis (2012)

This research is supported by socio-cognitive theories such as the self-determination theory (Deci & Ryan, 1985, 1991). It aims to study the relationship between gender, performance and academic ... [more ▼]

This research is supported by socio-cognitive theories such as the self-determination theory (Deci & Ryan, 1985, 1991). It aims to study the relationship between gender, performance and academic motivation of university students. The first part presents concepts and theories of motivation. Then, it looks at sex inequalities in motivation, especially at the university level. The second part begins with a presentation of the different types of motivation and the tool to measure them: the Motivation Scale in Education - University Studies (Vallerand et al. 1989). This section proposes four different surveys in the framework of the longitudinal study of the academic motivation, which was carried out on three successive cohorts in first year at university. The first exploration is devoted to the evolution of different types of motivatio n during the year. It confirms the existence of variations in the types of motivation and the influence of gender on these fluctuations. The second exploration uses correlation analysis to investigate reciprocal relationships between academic motivation and academic performances. The relationship between motivation and final performances are clearly established from December. Gender differences have been observed but significant variations between cohorts restrict the scope of the results. The third exploration consists of a group-based semiparametric method to estimate academic motivation trajectories. This original approach has confirmed some assumptions made by the self-determination theory of Deci and Ryan (1985). The final exploration of our collected data is based on the possibility to conduct multilevel analyses on repeated measurements. Surprisingly, neither the gender nor the performance of the students can explain the interindividual variance of motivation. Results are discussed with reference to the four different statistical devices used and to the strong cohort effect. [less ▲]

Detailed reference viewed: 146 (23 ULg)
See detailTerrestrialization and evolutionary radiation of basal embryophytes on the Gondwana
Gonez, Paul ULg

Doctoral thesis (2012)

The conquest of land is one of the most important evolutionary steps in embryophyte evolution. It allowed plants to reach an outstanding level of diversity, conquer a variety of new ecological niches and ... [more ▼]

The conquest of land is one of the most important evolutionary steps in embryophyte evolution. It allowed plants to reach an outstanding level of diversity, conquer a variety of new ecological niches and dominate almost all terrestrial ecosystems. The early floras of Laurussia are well studied. Numerous localities have been known and studied for about two centuries; the scientific literature about those is abundant. On the contrary, the early floras from Gondwana are poorly known, even though this continent gathers the two thirds of the emerged lands in the Pridoli-Lochkovian ages. This work attempts to demonstrate the relevance of the study of Gondwanan early floras for understanding the terrestrialization processes and adaptive radiation of the embryophytes during the Pridoli-Lochkovian. Firstly, we describe two assemblages from South Africa and Brazil. These localities are located on the western margin of Gondwana during the Pridoli-Lochkovian. Six new taxa are described from the Brazilian locality. The latter assemblage demonstrates a diversity equivalent to that of the most diverse assemblage from the Lochkovian of Wales, which was part of Laurussia. Some of the morphological characters described from the latter assemblages allow inferring phylogenetical hypotheses. All these hypotheses are confirmed by a cladistic analysis. Hence the study of Gondwanan early floras also permits to decipher the affinities of some plants of rhyniophytoid architectures The Gondwanan floras also allow drawing some hypothesis about the ecology of rhyniophytoid polysporangiophytes. On the basis of architectural characters (long proximal axes and non-isotomous branchings), we postulate that the early land plants of rhyniophytoid architecture were in competition with each other for sunlight collection and spore dispersal. This implies that the rhyniophytoid communities formed rather dense vegetal mats. It is therefore likely that they were structured as a minute canopy: the long proximal axes are analogous to the tree trunk stratum and the branching crowns are analogous to the canopy. Finally, the study of the oldest South China block plant assemblage demonstrates that the flora from the equatorial belt of Gondwana is radically different from that of its western edge. Contrarily, the study of the Brazilian locality confirms the floral similarities between western Gondwanan and South Laurussian floras. This suggests… [less ▲]

Detailed reference viewed: 63 (11 ULg)
Full Text
See detailOn the development of an integrated bone remodeling law for orthodontic tooth movements models using the Finite Element Method.
Mengoni, Marlène ULg

Doctoral thesis (2012)

One of the guiding principles in orthodontics is to gradually impose progressive and irreversible bone deformations due to remodeling using specific force systems on the teeth. Bone remodeling leads the ... [more ▼]

One of the guiding principles in orthodontics is to gradually impose progressive and irreversible bone deformations due to remodeling using specific force systems on the teeth. Bone remodeling leads the teeth into new positions with two tissues having a major influence: the periodontal ligament and the alveolar bone. Their mechanical and biological/physiological reactions to orthodontic forces are tightly linked. This mechanical biological coupling can be treated in biomechanical models, focusing on the mechanics and considering the phenomenological aspects of the biology/physiology. The development of such a model for bone tissue within a Finite Element framework is the core of this work. We propose to reconcile two approaches of bone modeling (small strains linear elasticity for remodeling problems and complex constitutive models for other applications) by writing a constitutive model for trabecular bone at macroscopic level, built on morphological parameters to describe the anisotropy, and accounting for effects such as plasticity of the trabeculae. The continuum parameters such as the stiffness can evolve with morphology as remodeling occurs in the tissue. For this, we extend and enhance Doblaré and Garcia's remodeling phenomenological model. The remodeling process corresponds to an evolution of a damage tensor representing the bone morphology. To do so, we propose an integration method for an anisotropic Continuum Damage model coupled to plasticity. Adapting Doblaré and Garcia's remodeling law to our constitutive model, we extend it so that it can be used in the specific case of orthodontic tooth movement, still following Frost's mechanostat theory. We propose to include the hydrostatic pressure dependency of remodeling, due to the presence of the periodontal ligament, within the bone remodeling law. We finally present a validation method for the mechanical representation of the bone matrix through the knowledge of its morphology, both on engineered cellular solids with bone-like morphology (aluminum and polymeric foams) and on bone (Deer antler) samples. Applying the model on the benchmark problem of the proximal femur remodeling, leads to results that are comparable to other models of the literature. We can therefore assume the way the remodeling model is built is valid. We finally apply the developed model to orthodontic tooth movement simulations. First we propose a model accounting for the non-linear mechanical response of the PdL through either bilateral contact conditions or spring models. We then present applications of orthodontic tooth movement, either displacement driven or force driven, both 2D and 3D. We thus show we can qualitatively represent the tooth movement, however outlining some of the drawbacks of the models (an unphysiological density distribution can arise due to the poor representation of the actual loads and a strong dependence on the boundary conditions is pointed out). However, we can represent the formation and resorption of hyaline areas, the non-linearity of the force/displacement relationship, and that applying a stepwise increasing force leads to higher displacements than a high initial force as there is no hyaline zone to resorb. [less ▲]

Detailed reference viewed: 149 (33 ULg)
Full Text
See detailGeneralized Shape Optimization using XFEM and Level Set Description
Van Miegroet, Laurent ULg

Doctoral thesis (2012)

CAD based shape optimization aims at finding the shapes of internal and external boundaries of a structural components. The method is able to improve the design of structures against var- ious criteria ... [more ▼]

CAD based shape optimization aims at finding the shapes of internal and external boundaries of a structural components. The method is able to improve the design of structures against var- ious criteria such as restricted displacements, stress criteria, eigenfrequencies, etc. However, this technique has been quite unsuccessful in industrial applications because of the mesh management problems coming from the large shape modifications. The main technical problems stems from the sensitivity analysis requiring the calculation of the so-called velocity field related to mesh modifications. If 2D problems are quite well mastered, 3D solid and shell problems are difficult to handle in the most general way. It turns out that shape optimization remains generally quite fragile and delicate to use in industrial context. To circumvent the technical difficulties of the moving mesh problems, a couple of methods have been proposed such as the fictitious domain approach, the fixed grid finite elements and the projection methods. The present work relies on the application of the extended finite element method (X-FEM) to handle parametric shape optimization. The X-FEM method is naturally associated with the Level Set description of the geometry to provide an efficient and flexible treatment of problems involving moving boundaries or discontinuities. On the one hand, the method proposed benefits from the fixed mesh approach using X-FEM to prevent from mesh management difficulties. On the other hand, the Level Set description provides a smooth curves representation while being able to treat topology modifications naturally. In this thesis, we focus on the material-void and bi-material X-FEM elements for mechanical structures. The representation of the geometry is realized with a Level Set description. Basic shapes can be modeled from simple Level Set such as plane, circle, ... NURBS curves and surfaces that can be combined together using a Constructive Solid Geometry approach to represent com- plex geometries. The design variables of the optimization problem are the parameters of basic Level Set features or the NURBS control points. Classical global (compliance, eigenfrequencies, volume) and local responses (such as stress constraint) can be considered in the optimization problem that is solved using a mathematical programming approach with the CONLIN optimizer. The problem of the computation of the shape sensitivity analysis with X-FEM is carefully ad- dressed and investigated using several original methods based on semi-analytical and analytical approaches that are developed. Academic examples are first considered to illustrate that the proposed method is able to tackle accurately shape optimization problems. Then, real life struc- tures including 2D and 3D complex geometries illustrate the advantages and the drawbacks of using X-FEM and Level Set description for generalized shape optimization. [less ▲]

Detailed reference viewed: 140 (15 ULg)
Full Text
See detailRôle des gènes pax4 et arx au cours de la différenciation endocrine pancréatique chez le poisson zèbre
Djiotsa, Joachim ULg

Doctoral thesis (2012)

Genetic studies in mouse have demonstrated the crucial function of PAX4 in pancreatic cell differentiation. This transcription factor specifies β- and δ-cell fate at the expense of α-cell identity by ... [more ▼]

Genetic studies in mouse have demonstrated the crucial function of PAX4 in pancreatic cell differentiation. This transcription factor specifies β- and δ-cell fate at the expense of α-cell identity by repressing Arx gene expression and ectopic expression of PAX4 in α-cells is sufficient to convert them into β-cells. Surprisingly, no Pax4 orthologous gene can be found in chicken and xenopus tropicalis raising the question of the function of Pax4 gene in lower vertebrates such as in fish. In the present study, we have analysed the expression and the function of the orthologous pax4 gene in zebrafish. In zebrafish, pax4 is not required for the generation of pancreatic β- and δ-cells, unlike its crucial role in the differentiation of these cell types in mouse. On the other hand, the mutual repression between Arx and Pax4 is observed in both mouse and zebrafish. These data suggests that the main original function of Pax4 during vertebrate evolution was to modulate the number of pancreatic α-cells and its role in β-cells differentiation appeared later in vertebrate evolution. [less ▲]

Detailed reference viewed: 23 (5 ULg)
Full Text
See detailAPPLICATION OF GEOMATICS FOR THE ASSESSMENT OF PASTORAL RESOURCES IN MOROCCO
Mahyou, Hamid ULg

Doctoral thesis (2012)

Rangeland or natural arid pastures of Morocco are defined as ecosystems where there is a natural or semi-natural vegetation composed of steppes, shrubs and grassland used mainly for livestock production ... [more ▼]

Rangeland or natural arid pastures of Morocco are defined as ecosystems where there is a natural or semi-natural vegetation composed of steppes, shrubs and grassland used mainly for livestock production as climate and soil are unsuitable to agriculture. The arid rangelands of Morocco occupy an area of over 33 million hectares between the isohyets of 100 and 400 mm. These areas represent livelihoods for thousands of people and protect the country from desertification. The main objective of this study is to provide scientific community and decision-makers methodological tools for assessing arid rangelands, based on geomatics and biophysics data. This study is divided in four parts: 1. The first part presents an overview of the threat of the desertification, emphasizes on the causes and consequences of rangeland degradation in Morocco, from literature sources, statistics, climate data and maps. Morocco rangelands are located in ten different pastoral zones that differ from each other by their floristic composition, soil and climatic conditions. According to Globcover map these rangelands are mainly composed by bare soil, herbaceous vegetation, shrubs and deciduous savanna mosaic / shrub or forest. The largest pastoral zones are: the Saharan zone, Pre-Saharan, the Oriental plateaus and the Valley of Moulouya. These zones are the most degraded with respectively 97, 89 and 69% of their total area. Available information on several pilot areas shows that the Moroccan rangelands are degraded due to many factors, which include overgrazing, cultivation, population increase and climate variation. 2. The second part of the study demonstrates the usefulness of remote sensing for assessing drought in arid rangelands of Morocco. Bi-weekly TERRA Moderate Resolution Imaging Spectroradiometer (MODIS 250 meters) data were used for this purpose. A Preliminary mapping by using Landsat TM5 of major land cover types was carried out to extract the pasture area. A comparison of annual and seasonal Normalised Difference Vegetation Indices (NDVI), Vegetation Condition Index (VCI) and rainfall during the time period of 2000–2008 were carried out. Results show significant correlations of either NDVI (r= 0.72**) or VCI (r=0.42*) with past season (3 months) rainfall. NDVI variation is a good indicator of vegetation changes and consequently can give a reliable indication on drought conditions in the study area. NDVI values lower than 0.2 are indicative of drought occurrence. NDVI values between 0.20 and 0.28 indicate average weather conditions and values higher than 0.28 correspond to humid conditions. 3. The third part presents an original knowledge-based approach for mapping the degradation of rangelands in North Africa. The study area is located in the high plateaus of eastern Morocco which include 3.5 million hectares of arid rangeland steppes. The approach consists in using datasets derived from Landsat TM satellite imagery, lithology, phytogeographic data and field indicators. The field indicators are: the steppes composition, perennial vegetation cover, annual perennial production, grazing level and the prevalence of rangeland cultivation. Results show that the knowledge-based approach is a valid method for evaluating rangeland degradation. The proposed knowledge-based approach discriminated between rangeland categories that would not have been discernible using only remote sensing. Overall classification accuracy of rangeland degradation obtained using this approach was 93%. This approach revealed that 11, 36 and 30% of the study area have shown very severe, severe and moderate degradation level, respectively. 4. The fourth part concerns the assessment of Alfa grass (Stipa tenacissima) tussocks at various degradation levels of Alfa grass steppes in the high plateaus of eastern Morocco, based on field hyperspectral data (350 – 2500 nm) and digital images during fall and spring seasons. Digital images of Alfa grass tussocks were taken using a digital camera to classify of the tussocks according to their proportion in green leaves (green, mixed and dry tussock). Assess software (Image Analysis Software for Plant Disease Quantification, APS 2002) was used to obtain the proportion of greenness in each tussock. Hyperspectral data of three states of tussocks (Green, Mixed and Dry tussock leaves) were collected within three degradation levels of Alfa grass steppes (Slight, Moderate and Severe degradation) with the ASD FieldSpec® 3 spectroradiometer. Paired t-test, Normalized difference spectral reflectance (NDSR) and Stepwise Discriminate Analysis were used to discriminate between various tussock status and different Alfa grass steppes. The results indicate that Alfa grass had shown an intraspecific variability in reflectance spectra. The proportion of green leaves in Alfa grass tussock strongly influences the spectral response. The discrimination of different Alfa grass tussock status was better during fall than spring. The spectral behavior of Alfa grass tussock is problematic for the mapping and the assessment of Alfa grass steppes by conventional remote sensing techniques. [less ▲]

Detailed reference viewed: 63 (11 ULg)
Full Text
See detailRESEARCHES REGARDING COLLOIDAL AND OXIDATIVE STABILITY OF CONFECTIONERY PRODUCTS (HALVA) OBTAINED FROM SUNFLOWER
Muresan, Vlad ULg

Doctoral thesis (2012)

Prior to the experimental part of this work, a literature review related to the aim of this thesis was realized. Firstly, it describes the balanced nutritional composition of sunflower seeds and their ... [more ▼]

Prior to the experimental part of this work, a literature review related to the aim of this thesis was realized. Firstly, it describes the balanced nutritional composition of sunflower seeds and their applications as food industry raw materials. It follows the state of the art of sunflower halva manufacturing with emphasis on the main issues encountered during processing. Consequently, as the researches concerning sunflower halva type products are very limited, it was decided to consolidate the identified quality problems (i.e., oil separation problem and rancidity during storage) background by given basic principles concerning foods physical properties (e.g., rheology, particle size distribution), as well as food products colloidal and oxidative stability basics. Moreover, fundamentals of NIR spectroscopy and chemometrics give the background for a proposal of an alternative nondestructive and rapid method to assess lipid oxidation in sunflower halva type products. Firstly, the experimental part of this thesis focuses on comparing the physico-chemical properties of different particle size tahini prototypes including also the industrial reference in order to understand tahini behavior and structure. Studying the physico-chemical properties of different granulometries tahini samples allows, for the first time, the prediction of a schematic sunflower tahini structure – knowledge needed to understand physical and oxidative instability for this type of products. Moreover, the experimental work aimed to assess the influence of particle size distribution, storage time and temperature on sunflower tahini colloidal and oxidative stability. Furthermore, during this work there were developed two new methodologies, a laser diffraction method to determine particle size distribution of sunflower tahini, as well as a near infrared rapid method coupled with chemometrics to assess in situ sunflower tahini oxidative status. [less ▲]

Detailed reference viewed: 96 (9 ULg)
Full Text
See detailEtude de l'hydrodynamique au sein d'un bioréacteur à cuve agitée utilisé pour la culture de cellules animales adhérentes sur microporteurs: Caractérisation expérimentale et théorique des écoulements via des outils eulériens et lagrangiens
Collignon, Marie-Laure ULg

Doctoral thesis (2012)

Cette thèse a été financée par le FNRS (Fonds National de Recherche Scientifique belge) via un mandat d’aspirant (1.1.2002.10.F, 78014). Elle a été réalisée au Laboratoire de Génie Chimique de ... [more ▼]

Cette thèse a été financée par le FNRS (Fonds National de Recherche Scientifique belge) via un mandat d’aspirant (1.1.2002.10.F, 78014). Elle a été réalisée au Laboratoire de Génie Chimique de l’Université de Liège sous la supervision des Professeurs Dominique Toye et Michel Crine. La thématique de recherche s’inscrit dans le cadre d’une collaboration scientifique entretenue depuis de nombreuses années entre le Laboratoire de Génie Chimique et la société pharmaceutique GlaxoSmithKline Biologicals. Elle concerne la culture de cellules animales adhérentes sur microporteurs en bioréacteur de type cuve agitée. Ce type de procédé est, en effet, largement utilisé dans l’industrie pharmaceutique pour produire des composés protéinés tels que des vaccins, des glycoprotéines et des anticorps monoclonaux. Le choix du design et des conditions d’agitation de ce type de bioréacteur est complexe car il doit répondre à deux objectifs antagonistes : maximiser le mélange du milieu de culture tout en minimisant les contraintes mécaniques qui peuvent agir sur les cellules animales, ces dernières étant réputées comme particulièrement sensibles à ces contraintes lorsqu’elles sont fixées à la surface de microporteurs. Pour aider à réaliser ce choix, nous avons développé dans cette thèse une méthodologie qui tente de décrire l’influence des conditions d’agitation sur l’environnement hydrodynamique local perçu par un élément de fluide en mouvement via une description combinée eulérienne et lagrangienne de l’écoulement turbulent au sein du bioréacteur. Le Chapitre I a pour but de présenter l’état de l’art relatif à la culture de cellules animales adhérentes dans des bioréacteurs à cuve agitée, ainsi que d’introduire l’essentiel des notions théoriques qui seront utilisées dans la suite de la thèse. Il est divisé en quatre parties. La première partie présente les spécificités de la culture de cellules animales de mammifères et les défis technologiques associés. La deuxième partie introduit, en se basant sur diverses études antérieures, le problème central de cette thèse. La troisième partie présente l’approche adoptée dans cette thèse pour répondre au problème posé. L’originalité de l’approche adoptée est également mise en évidence. Dans la quatrième partie, les hypothèses nécessaires à ce travail sont présentées et validées sur base de résultats issus d’autres études publiées dans la littérature. Le Chapitre II a pour but de sélectionner deux mobiles axiaux auxquels sera appliquée la méthodologie développée dans cette thèse. Pour ce faire, sept mobiles axiaux sont comparés sur base des contraintes mécaniques qu’ils génèrent, estimées à partir de la mesure de la puissance globale dissipée, lorsqu’ils tournent respectivement à leur vitesse minimale de maintien des microporteurs en suspension complète Njs. Cette comparaison permet de sélectionner les mobiles TTP 125 (d/T=0.4, Mixel) et EE 150 (d/T=0.5, Applikon). Le Chapitre III est consacré à l’étude eulérienne détaillée de l’écoulement turbulent généré par les deux mobiles sélectionnés au chapitre précédent. Sur base de mesures 3D P.I.V., les champs moyens de vitesse dans cinq plans axiaux sont établis et analysés. Ce même exercice est réalisé pour les grandeurs caractéristiques de la composante turbulente de l’écoulement que sont l’énergie cinétique turbulente et son taux de dissipation. Grâce à ces données, la répartition spatiale des contraintes mécaniques au sein de l’écoulement turbulent est établie ; ce qui permet d’identifier au sein de la cuve des zones labélisées comme potentiellement problématiques pour le développement des cellules cultivées sur les microporteurs. Dans le Chapitre IV, l’impact de gradients de concentration présents au sein de la cuve, suite à une injection de soude par exemple, est évalué. Dans ce but, le mélange au sein du bioréacteur a été étudié de manière globale par la mesure de temps de mélange et de manière locale par la mesure de l’évolution avec le temps de champs de concentration par la technique P.L.I.F. Ces mesures ont montré que le temps d’ « existence » des gradients de concentration est nettement inférieur aux temps caractéristiques relatifs à une modification du métabolisme cellulaire. Il en résulte que, dans la suite du travail, les champs de concentration seront supposés comme constants et uniformes au sein de la cuve agitée. Les hétérogénéités ponctuellement présentes après l’ajout de soude ne seront donc pas prises en compte dans la caractérisation Euler-Lagrange de l’écoulement. La première partie du Chapitre V présente le principe et les outils de modélisation nécessaires à la mise au point et au fonctionnement du dispositif de trajectographie optique conçu et développé dans le cadre de cette thèse. Cette installation, tout à fait originale et unique, permet de suivre la trajectoire d’une particule au sein de la cuve agitée pendant des temps très longs et permet donc d’accéder à l’étude lagrangienne de l’écoulement. La seconde partie du chapitre est consacrée à la caractérisation des trajectoires mesurées. L’isoprobabilité de présence de la particule dans tout volume élémentaire de la cuve agitée a pu être confirmée. La validité et la convergence des résultats obtenus par trajectographie ont pu être vérifiées par comparaison des champs de vitesse calculés à partir des trajectoires avec ceux mesurés par 3D P.I.V. Au Chapitre VI, les données eulériennes sont combinées aux données lagrangiennes afin de caractériser le lien entre la succession d’environnements hydrodynamiques perçus par des cellules fixées sur des microporteurs et les conditions d’agitation du bioréacteur. Cette caractérisation repose principalement sur l’analyse de la distribution de temps de séjour de la particule dans la zone labélisée comme problématique pour le développement cellulaire DTSzone , de la distribution de temps de séjour de la particule dans la zone non problématique DTShors zone ainsi que sur l’analyse des distributions de temps mis par la particule pour réaliser un cycle « visite de zone problématique-visite de zone non problématique » DTcycle. La taille des zones problématiques et non problématiques dépend de la valeur choisie pour le critère λK/dp, du type de mobile, ainsi que de sa vitesse de rotation. L’impact de ces trois grandeurs sur les distributions de temps a donc été analysé. Cette thèse se clôture bien naturellement par un chapitre de conclusion résumant les informations acquises et proposant diverses perspectives [less ▲]

Detailed reference viewed: 156 (33 ULg)
Full Text
See detailLes manuscrits de la recension égyptienne des Mille et une Nuits. Étude codicologique, avec édition critique, traduction et analyse linguistique et littéraire du conte de Jānšāh
Franssen, Elise ULg

Doctoral thesis (2012)

The Thousand and One Nights have fascinated millions of readers and have spawned a variety of scholarly literature. Analyses of the tales are based on existing editions of the Arabic text, almost all ... [more ▼]

The Thousand and One Nights have fascinated millions of readers and have spawned a variety of scholarly literature. Analyses of the tales are based on existing editions of the Arabic text, almost all dating back to the 19th century, and none of them completely reliable. However, since Zotenberg’s classification of the manuscripts of the Nights in the 19th century, research on the manuscripts has not really progressed. One of the groups Zotenberg described, called now the ZER, “Zotenberg's Egyptian Recension”, gathers together the manuscripts containing exactly 1001 nights, copied in Egypt at the end of the 18th or at the beginning of the 19th century. All the manuscripts of the ZER are in four volumes and present the same distribution of nights; they also share many common codicological features. A precise codicological analysis of each of those manuscripts was carried out. The collected information was compared with the conclusions of the literary and philological study of each manuscript’s text in a complete approach to the manuscripts, seen as objects as well as texts. The Nights were written for the bourgeoisie, in their own language, Middle-Arabic. This level of language was deliberately used for certain literary productions, such as literature intended for entertainement. A close study of the language of the manuscripts provides information on this level of language still little known. The study was carried out on Jānšāh tale, and a synoptic critical edition —confronting the manuscripts to the ancient editions of Būlāq and Calcutta II, collated for the occasion— and French translation of the latter were prepared. In brief, codicological analyses provide useful information for the research in codicology and for the classification of the manuscripts, a prerequisite for the critical edition. The analysis of the text’s language makes an important contribution to a neglected field. The text of the critical edition constitutes a solid basis for the investigations into the contents of the story. [less ▲]

Detailed reference viewed: 192 (29 ULg)
See detailIdentification des sirtuines en tant que nouvelles cibles thérapeutiques pour l'asthme allergique
Legutko, Agnieszka ULg

Doctoral thesis (2012)

Sirtuins comprise a unique class of NAD+-dependent deacetylases that regulate diverse biological functions including ageing, metabolism and stress resistance. Recently, it has been shown that sirtuins may ... [more ▼]

Sirtuins comprise a unique class of NAD+-dependent deacetylases that regulate diverse biological functions including ageing, metabolism and stress resistance. Recently, it has been shown that sirtuins may dampen the inflammatory response in vitro by inhibiting pro-inflammatory transcription factors such as NF-κB. We therefore sought to determine whether sirtuins play a role in allergic airway inflammation. To address this issue, we have assessed in OVA-sensitized mice the effects of selectively antagonizing sirtuins during OVA challenge. Sirtuin inhibition was achieved by treating mice with either cambinol or sirtinol, two selective pharmacological inhibitors. Surprisingly, sirtuin inhibition was associated with strong attenuation of allergic lung inflammation, airway hyperreactivity, production of mucus and Th2 cytokines. We furthermore showed that sirtuin inhibition altered maturation and migration of lung dendritic cells, thereby preventing dendritic cell-driven Th2 priming in the draining lymph nodes. In an attempt to elucidate the mechanisms responsible for these effects we used peroxisome proliferator-activated receptor-γ deficient cells to demonstrate that the effects of cambinol and sirtinol in dendritic cells were dependent on an increase in the activity of this anti-inflammatory transcription factor. Finally, using genetic engineering, we demonstrate that sirtuin 1 is the sirtuin responsible for repression of the activity of PPAR-γ- in dendritic cells, thereby favoring their maturation toward a pro-Th2 phenotype. This study reveals a previously unappreciated function of sirtuin 1 in the regulation of dendritic cell function and Th2 responses, thus shedding new light on our current knowledge on the regulation of inflammatory processes by sirtuins. [less ▲]

Detailed reference viewed: 35 (7 ULg)
Full Text
See detailDecomposition, Localization and Time-Averaging Approaches in Large-Scale Power System Dynamic Simulation
Fabozzi, Davide ULg

Doctoral thesis (2012)

Present-day interconnected electric power systems are the largest machines in the world. Guaranteeing a stable supply of electric power is vital for modern societies: power systems must be able to ... [more ▼]

Present-day interconnected electric power systems are the largest machines in the world. Guaranteeing a stable supply of electric power is vital for modern societies: power systems must be able to withstand plausible disturbances. A certain number of simulations of the post-disturbance behavior are routinely executed by some transmission system operators to assess that the system is operated in a secure way. Usually this assessment has to be performed within a predefined time frame, using the available computing resources. Improving the simulation speed allows the operators to perform a wider assessment, thus making better use of the available computational power. A large part of this research took place in the context of the PEGASE project, supported by European Commission (Seventh Framework Programme) and has resulted in some novel algorithms for faster dynamic simulations, one of the PEGASE project main goals. First, this thesis revisits the Newton method used to solve the differential-algebraic model. Then, three original algorithmic improvements are presented, namely (i) decomposition, (ii) localization and (iii) time-averaging of the system response. Finally, the combination of these approaches is shown to provide a fast and reliable tool for dynamic security assessment. All the presented techniques have been thoroughly tested on an academic system, a large real-life system and a realistic system of unprecedented size, representative of the whole continental European synchronous grid. [less ▲]

Detailed reference viewed: 253 (28 ULg)
Full Text
See detailAmélioration du tri de semences de chicorée industrielle (Cichorium intybus L.) sur base d’attributs mesurés par vision artificielle
Ooms, David ULg

Doctoral thesis (2012)

The commercial production of industrial chicory seeds (cypselae) includes the postharvest elimination of nonviable seeds by non-destructive tools. For this purpose, two machine vision methods were set up ... [more ▼]

The commercial production of industrial chicory seeds (cypselae) includes the postharvest elimination of nonviable seeds by non-destructive tools. For this purpose, two machine vision methods were set up for the detection of nonviable seeds: color vision and fluorescence imaging. In addition, the appropriate criteria to estimate the efficiency of seed sorting were defined using a sorting optimization curve which describe the trade-off between the quality improvement of a seed lot and the loss of material. The analysis of color images of 1,500 seeds of the ‘Nausica’ variety allows only the recognition of desiccated and undeveloped seeds. This is caused by the large natural variability of seed color, shape and texture. Fluorescence imaging was set up in order to analyze the repartition of chlorophyll fluorescence (CF), a marker of seed maturity, on different areas of the seed (pericarp and pappus). It comprised a monochromatic light source, a highpass filter and a monochromatic CCD camera sensitive to red and infrared. With this device, blue light reflected by the seeds was blocked whilst red fluorescence was measured by the camera. A segmentation algorithm was designed to estimate separately the fluorescence intensities of the pappus, a crown of scales, and the main body of the pericarp. Experiments were carried out on five clones of cross-pollinated chicory plants used for seed production and four series of 30 plants from 2 common varieties grown in different weather conditions. The flower heads were labelled at flowering and harvested at different times during the maturation process expressed in "days after flowering" (DAF). Germination tests were performed according to the recommendations of the International Seed Testing Association to measure the germination percentage (GP) and the germination rate (GR), an indicator of seed vigour. The dry weight (DW), water content (WC), maturation duration, germination percentage (GP), and germination rate (GR) were measured to estimate seed quality. For all experiments, the chlorophyll fluorescence diminished mainly between 16 and 33 DAF during the filling phase of seed development. The correlations between CF and maturity parameters (DW, WC) were comprised between 0.25 and 0.75 in absolute value for seeds that matured 16 to 44 days on the stalk. Sorting simulations were made on the basis of CF alone or in combination with the achene area density (AD) (mg/mm²). The CF was efficient to select seeds produced outdoor or in the greenhouse with the aim of increasing GP or GR but AD was an even better sorting feature. In the greenhouse, where developing seeds were submitted to temperatures higher than 25 °C, the use of CF in combination with AD improved the sorting efficiency. [less ▲]

Detailed reference viewed: 77 (19 ULg)
Full Text
See detailStudy of the effect of waxes on the biological activity of essential oils against Penicillium italicum Wehmer and P. digitatum Sacc, two postharvest pathogens of citrus fruits
Kouassi, Kouadio Hugues Sosthène ULg

Doctoral thesis (2012)

Control measures of postharvest fungal diseases of plants are principally based on the use of conventional chemical fungicides. However, in view of the problems associated with the use of these ones, as ... [more ▼]

Control measures of postharvest fungal diseases of plants are principally based on the use of conventional chemical fungicides. However, in view of the problems associated with the use of these ones, as well as the increasing demand for organically produced food, there is a need to replace chemical fungicides by alternative safer products, such as biological fungicides called "natural" or biofungicides. Among natural fungicides, essential oils (EOs) have been studied. EOs and their compounds present, among other things, antifungal properties and can be an interesting alternative to chemical fungicides. For this purpose, a screening of EOs according to intrinsic (yield in aromatic plant, toxicity) and extrinsic (availability, cost) criteria was carried out. Thirty EOs were selected and their inhibitory activity was tested on the in vitro growth of Penicillium italicum Wehmer, P. digitatum Sacc (pathogens of citrus fruits) and Colletotrichum musae (Berk. & M.A. Curtis) (pathogen of banana). Cinnamomum zeylanicum, C. verum and Eugenia caryophyllata proved to be the most effective at 100 ppm against the three pathogens. The biological activity of these three EOs against P. digitatum and P. italicum was evaluated on artificial infected orange fruits. EOs diluted in ethanol were able to either partially (at a concentration < 5%) or totally (at a concentration ≥ 5%) control disease incidence due to infections of both pathogens. Among the three EOs, C. zeylanicum was the most effective. In order to improve the efficiency of C. zeylanicum EO, a development of formulations consisting of this EO and Simulgel (thickening and emulsifying polymer) or waxes (shellac and / or carnauba, paraffin or polyethylene) were performed. The in vivo biological activity of the formulations was also evaluated against P. digitatum and P. italicum. In general, fungal disease control was improved in the case of fruits treated with C. zeylanicum EO supplemented with Simulgel or waxes compared to that supplemented with ethanol. The improvement was much higher with formulation consisting of C. zeylanicum-shellac (and / or carnauba) compared to the others. A SPME/GC-MS analysis of the headspace of EOs (C. zeylanicum, C. verum and E. caryophyllata) supplemented with shellac and / or carnauba (in vitro) or of oranges treated with such formulations (in vivo) highlighted the lack of some specific volatile compounds of EOs (oxygenated cyclic ones with a specific gravity superior to 0.934), in the vapor phase of the in vitro and in vivo tests, even after 7 days. While when these EOs were supplemented with ethanol, Simulgel, paraffin or polyethylene, all EO compounds were detected in the analyzed headspaces from 4 hours up to 7 days. Analysis of formulations by Fourier transform infrared spectroscopy (FTIR) revealed the formation of hydrogen bonds between such specific EO compounds and waxes (shellac and / or carnauba) This hydrogen bonds formation seems to be responsible of the non-volatilization of EO compounds and their maintaining on the fruit epidermis, thus improving citrus fruit protection. These hydrogen bonds are not observed between non-oxygenated or non-cyclic oxygenated EO compounds and none of the waxes. The present study may therefore allow a careful selection of appropriate EOs and waxes for the elaboration of effective biofungicide formulations. This application could be integrated into the packline procedure without significant modification. [less ▲]

Detailed reference viewed: 190 (25 ULg)
Full Text
See detailImproving Overlay Routing scalability using an Internet Coordinate System
Cantin, François ULg

Doctoral thesis (2012)

Nowadays lots of real time applications are used over the Internet: voice over IP, online video games, etc. For these applications the performance of the path between two communicating nodes is critical ... [more ▼]

Nowadays lots of real time applications are used over the Internet: voice over IP, online video games, etc. For these applications the performance of the path between two communicating nodes is critical. Particularly, most of these applications require small delays between communicating nodes. For these applications, the problem is that the choice of the routes in the Internet is generally not very much guided by performance concerns. It is well known that for lots of node pairs the default Internet path is suboptimal and there exists an alternative path providing a smaller delay between these nodes. In this thesis, we mainly address the problem of finding these alternative paths. Replacing Internet's routing philosophy in order to obtain default paths providing the best performance possible should be a good theoretical solution. However, replacing Internet's routing philosophy by a brand new one is very difficult or even impossible in practice. Another solution is to leave the default routes as they are and to perform indirect routing. Consider a path AB between two nodes A and B. If a path ACB has a smaller delay than AB, then, instead of sending data directly to B, A can send them to C and C can relay them to B. This is called overlay routing because we manage the routing in an overlay network built on top of the Internet (i.e. at the application level). Overlay routing is a promising way to improve the quality of service in the Internet but its main drawback is its poor scalability: measuring the characteristics of the paths, exchanging the measurement results between the nodes and computing the best routes in the full mesh overlay network generally implies a high consumption of resources. In this thesis, our main contribution is the design of a lightweight one-hop overlay routing mechanism improving the latencies: we define criteria that rely on the information provided by an Internet Coordinate System (ICS) in order to provide a small set of potential one-hop shortcuts for any given path in the network with small costs. Our best criterion does not guarantee to find the best shortcut for any given path in a network but, even in networks with hundreds or thousands of nodes, it will restrict the search for potential shortcuts to about one or two percent of the total number of nodes. Even if the estimation-based approach of overlay routing is our main contribution, this thesis also presents general results about routing shortcuts and Internet Coordinate Systems. For an ICS, a routing shortcut is a Triangle Inequality Violation (TIV) and it is often a big problem. Indeed, a TIV will cause estimation errors since, in this particular case, nodes cannot be embedded into any metric space. In this thesis, we study TIVs existing in the Internet and their impact on the Vivaldi ICS. This analysis leads to two contributions. Firstly, we propose criteria to establish, with a high probability of success, if there exists a shortcut or not for a given path AB. Secondly, we propose a Two-Tier architecture for ICSes that mitigates the effect of TIVs on the estimations. Finally, this thesis also discusses the efficiency of two solutions proposed in the literature in order to obtain an ICS that can deal with TIVs. The first one consists in applying non-linear transformations to delays before trying to embed them in a metric space. The second one consists in modelling the estimation problem as a matrix completion problem in order to completely avoid the embedding in a metric space. [less ▲]

Detailed reference viewed: 147 (22 ULg)
Full Text
See detailClimate-driven growth of croplands and grasslands: analysis and modeling at regional scale
Horion, Stéphanie ULg

Doctoral thesis (2012)

Comprehensive understanding of the interactions between climate and vegetation is a key issue in environmental sciences, and especially for researchers studying climate change impacts on terrestrial ... [more ▼]

Comprehensive understanding of the interactions between climate and vegetation is a key issue in environmental sciences, and especially for researchers studying climate change impacts on terrestrial ecosystems. Indeed in order to better predict changes in ecosystems productivity, scientists are investing time and e ort in assessing how environmental changes are influencing - and are going to influence in the near future - the vegetation distribution and dynamics. Temperature, precipitation and atmospheric CO2 are the key determinants of the distribution of vegetation on Earth. Over the last 150 years, it has been reported that the global surface temperature has increased on average by around 0:8 C. Several studies mentioned that this rapid warming has resulted in reduction of climatic constraints to biological activity and shift in growing season. However changes in vegetation dynamics are not uniform spatially. From a methodological point of view, annual and seasonal metrics were commonly used to assess the impact of climate variability on vegetation at global and continental scales. The studies therefore neglected that intra-annual variability in the response of terrestrial ecosystems to such changes may exist. This intra-annual variability can be seen as the difference in vegetation response to a given environmental change according to its phenological development. In this research we investigated the intra-annual variation of the climatic constraints over croplands and grasslands in 25 regions located in Europe and Africa. The central question was: how best can we identify the climate footprint on vegetation development during the growing season, using global datasets of Normalized Difference Vegetation Index (NDVI) and the JRC-MARS meteorological indicators? The structure of this study is as follows. First we provide an overview of major studies linking climate variability and vegetation dynamic at global, continental and regional scales. Then we describe the NDVI and meteorological datasets used in this research, as well as the methodology developed to select optimal regions of interest for the study of 'climate-vegetation' interactions at regional scale. Indeed external factors - such as land cover changes, landscape fragmentation, etc. - need to be minimized to ensure that the variations in the NDVI signal can be attributed to climate variability. Preliminary time series analyses are then performed to characterize the long-term climate and vegetation conditions in each region of interest. We further present the approach developed in this research to decompose and to analyse jointly time series of remote sensing derived observation and climate dataset. We focus specifically on the adjustment of the 'climate-vegetation' relationships for specific periods within the growing season. Indeed we demonstrate that the relationship between NDVI and the meteorological parameters is highly complex and vary significantly trough the phenological cycle of the plants. Hence, interactions between vegetation dynamics and climate variability need to be studied at a smaller time scale than the year or the growing season, in order to identify properly the limiting factors to vegetation growth. Our analysis revealed that, in most of the cases, the best correlations are obtained when we considered the vegetative phase (from green-up to maximum of NDVI) and the reproductive phase (from maximum of NDVI to maturity) separately. We also show that climatic constraints identified using yearly proxies of climate and vegetation do not depict correctly, or completely, the climate control on vegetation development. Finally we evaluate the performance of climate-driven growth models in two sites of croplands and two sites of grasslands. The models were adjusted per phenological phases and set to provide 1-month forecast of NDVI. Pure climatic models (CLIM) were compared to auto-regressive climatic model (CLIM-AR). Apart in the Irish grasslands, the CLIM-AR models were performing better than CLIM models during the vegetative phase. On the other hand, during the reproductive phase, the introduction of the auto-regressive term did not improve significantly the performance of the CLIM model. Moreover the autoregressive term did never appear as first predictor, demonstrating that, in the selected sites, short to medium atmospheric conditions were explaining most of the variance in the 1-month forecast NDVI. [less ▲]

Detailed reference viewed: 44 (17 ULg)
Full Text
See detailLe consommateur mineur. Analyse juridique de la protection d'une personne doublement vulnérable
Nottet, Aurélie ULg

Doctoral thesis (2012)

La dissertation porte sur le statut juridique du consommateur mineur en Belgique, dans une vision intégrée mêlant droit des incapacités et droit de la consommation. Le mineur, personne vulnérable en ... [more ▼]

La dissertation porte sur le statut juridique du consommateur mineur en Belgique, dans une vision intégrée mêlant droit des incapacités et droit de la consommation. Le mineur, personne vulnérable en raison de son âge, est protégé par le droit. Notamment, il est soumis à un statut civil d’incapacité qui l’empêche de contracter valablement seul (art. 1124 C. civ.). Le consommateur, « personne physique qui acquiert ou utilise à des fins excluant tout caractère professionnel des produits mis sur le marché », est également protégé par le droit (règles consuméristes) en tant que partie faible au contrat conclu avec une entreprise. Le mineur consommateur s’impose comme une réalité (notamment avec l’avènement d’Internet). Destinataire de nombreux produits, cible privilégiée des annonceurs publicitaires, il devient un acteur économique à part entière. Comment le droit encadre cette réalité ? Quel statut réserve-t-il au consommateur mineur ? Ce statut est-il satisfaisant ? La thèse tend à répondre à ces questions. Elle brosse donc un portrait juridique précis du consommateur mineur, et propose quelques améliorations de lege ferenda. Elle comporte du reste une dimension de droit comparé: sur les points centraux, des solutions de droit français, néerlandais et allemand enrichissent l’analyse du droit belge. Elles en permettent une critique plus objective et/ou inspirent des solutions originales. [less ▲]

Detailed reference viewed: 264 (40 ULg)
Full Text
See detailSimulacres et Futurs antérieurs: Contributions à une approche narrative du politique
Claisse, Frédéric ULg

Doctoral thesis (2012)

The thesis assembles five publications dealing with the role played by fiction in our experience and apprehension of the world. Can fiction convey contents of knowledge or even constitute a source of ... [more ▼]

The thesis assembles five publications dealing with the role played by fiction in our experience and apprehension of the world. Can fiction convey contents of knowledge or even constitute a source of knowledge in itself? This question is broken down into a series of studies about the implicit sociology of American writer William S. Burroughs; industrial music as a critical device; the configuration power of Nineteen Eighty-Four in the denunciation of new technologies of surveillance and social control; the deep homology between power and narrativity; as well as counter-fiction within “societies of control”. The general introduction preceding these publications aims at building two examples of “fictional forms of intelligibility” conceived as cognitive and pragmatic resources used by members of society: “simulacrum”, which consists in criticising a target, in a systematically ironical mode, so as to turn its language and mode of functioning against it; “future perfect”, which proposes the anticipation of a threat described as having already occurred, in order to demonstrate the urgency in taking action to thwart it. The thesis defends a minimalist and holist conception of fictional knowledge: it is as a means at the service of the mimetic modelling of social and political processes that fiction activates a sense of possibilities and exerts a cognitive function. In this way, these collected works intend to give the first elements of a research programme in social and political sciences around power of and as a narrative. Narrative appears not only as an object, but especially as a tool for analyzing politics. [less ▲]

Detailed reference viewed: 153 (57 ULg)
Full Text
See detailEvidence-Based Model Calibration for Efficient Building Energy Services
Bertagnolio, Stéphane ULg

Doctoral thesis (2012)

Energy services play a growing role in the control of energy consumption and the improvement of energy efficiency in non-residential buildings. Most of the energy use analyses involved in the energy ... [more ▼]

Energy services play a growing role in the control of energy consumption and the improvement of energy efficiency in non-residential buildings. Most of the energy use analyses involved in the energy efficiency service process require on-field measurements and energy use analysis. Today, while detailed on-field measurements and energy counting stay generally expensive and time-consuming, energy simulations are increasingly cheaper due to the continuous improvement of computer speed. This work consists in the development of a simulation-based approach dedicated to whole-building energy use analysis for use in the frame of an energy efficiency service process. Focus is given to the development of a new simplified dynamic hourly building energy simulation tool adapted to energy use analysis of existing buildings, its calibration by means of available energy use data and to the integration of the calibration process into the Energy Service Process. The proposed evidence-based calibration methodology is deeply related to on-field inspection and data collection issues and is developed to fit with the audit/inspection process. After calibration, the model can be used to support the other steps of the Energy Services Process, such as ECOs selection and evaluation and continuous performance verification. The new systematic calibration methodology gives priority to the physical identification of the model’s parameters (i.e. to the direct measurement) and relies on the notion of hierarchy among the source of information (as a function of their reliability) used to identify the value of the parameters. The improved Morris’ sensitivity analysis method is used for “factor fixing” (i.e. distinction between non-influential model’s parameters) and “parameters screening” (i.e. classification of influential parameters by order of importance) in order to orient the data collection work and guide the parameters adjustment process. At the end of the calibration process, the Latin Hypercube Monte Carlo sampling is used to quantify the uncertainty on the final outputs of the calibrated model. The developed simulation tool and the associated calibration method are applied to a synthetic case (“Virtual Calibration Test Bed”) and to real case study building located in Brussels, Belgium. Both applications (real and synthetic cases) allow highlighting the complexity and the limits of calibration as it is used today. Calibration remains a highly underdetermined problem and a compromise has to be found between data collection and modeling efforts and model’s requirements in order to proceed to efficient energy use analysis. At the end of these applications, it is believed that partially manual methods remain more efficient and the best quality assurance when proceeding to calibration of a building energy simulation model. The use of an evidence-based method ensures sticking to reality and avoids bad representation and hazardous adjustment of the parameters. Moreover, it is shown that the intensive use of a sensitivity analysis method is of a great help to orient data collection and parameters adjustment processes. Defining confidence/uncertainty ranges for each parameter, in addition to a “best-guess” value, also allowed quantifying the uncertainty on the final outputs of the model and helped the user in evaluating the quality of the calibrated model. [less ▲]

Detailed reference viewed: 98 (28 ULg)
See detailInvestigation on placental lactogen in bovine foetus
Alvarez Oxiley, Andrea Vivian ULg

Doctoral thesis (2012)

Detailed reference viewed: 128 (6 ULg)
Full Text
See detailCaractérisation et valorisation des matériaux argileux de la Province de Kinshasa (RD Congo)
Wetshondo Osomba, Dominique ULg

Doctoral thesis (2012)

A la suite de la promulgation du Code Minier en juillet 2002, la quasi-totalité des investissements des sociétés minières nationales ou multinationales œuvrant en RD Congo est orientée vers les métaux de ... [more ▼]

A la suite de la promulgation du Code Minier en juillet 2002, la quasi-totalité des investissements des sociétés minières nationales ou multinationales œuvrant en RD Congo est orientée vers les métaux de base (Cu, Co, Sn, Mn,…) et les substances minérales précieuses (or, diamant, ...). La filière de la céramique pourtant très prometteuse et qui utilise, comme matières premières, les substances minérales industrielles compte parmi les secteurs les moins développés et/ou inexistants dans la majeure partie du pays. Dans une perspective de développement local durable, la présente étude a l’avantage de contribuer à la promotion des matériaux locaux de construction tout en améliorant la qualité des briques artisanales produites et à inciter la création des PME dans la filière de la céramique en RD Congo. Elle constitue donc un apport scientifique important dans la connaissance et la caractérisation des substances minérales industrielles de la RD Congo et plus particulièrement les matériaux argileux de Kinshasa et environs. Les connaissances scientifiques acquises sur les matériaux naturels et sur les produits fabriqués permettent de justifier l’emploi des matériaux du site pilote de Kasangulu dans la filière grossière de la céramique ou céramique de construction ; ceux du deuxième site pilote, Kingabwa, dans le secteur des réfractaires silico-alumineux et dans la branche de la céramique fine, traditionnelle et industrielle. En effet, les matériaux de Kasangulu et plus particulièrement les lithofaciès des couches 2 et 3 sont des produits silico-argileux plastiques qui constituent des ressources minérales industrielles de bonne qualité pour la fabrication des produits variés dont les briques stabilisées ou cuites (creuses, perforées, pleines et de parement), les hourdis et les tuiles. La présence de la goethite associée à l’oxyde de titane dans ces produits naturels apporte une plus-value considérable dans la teinture rougeâtre et/ou jaunâtre des produits finis. Les argiles de Kingabwa, que nous qualifions « d’argiles nobles », sont utilisables dans la fabrication des produits à plus haute valeur ajoutée comme les porcelaines. Néanmoins, les produits cuits de Kingabwa ont présenté un retrait à la cuisson de 9 à 12% pour de températures allant de 1100 à 1150°C et une perte en poids à la cuisson de l’ordre de 14% en moyenne. Pour une bonne rentabilité industrielle, ces retraits peuvent être minimisés par l’ajout d’une quantité optimale de dégraissant ou en revoyant à la hausse la température du séchage pendant l’élaboration des produits. Il a été montré que l’évolution de la résistance mécanique à la compression dans les briquettes cuites n’est pas totalement fonction de la porosité ou des retraits à la cuisson ni de la simple quantité de mullite formée. La fissuration de la pâte et le développement des fissures linéaires, surtout celles en cercles concentriques autour des cristaux influencent beaucoup cette propriété. Les ressources minérales étudiées présentent un avantage environnemental de taille pour leur emploi comme matières premières dans l’industrie céramique. En effet, ces substances sont très pauvres en matières organiques et ne contiennent pas des éléments tels que le soufre, la pyrite ou les carbonates. [less ▲]

Detailed reference viewed: 282 (31 ULg)
Full Text
See detailContribution à la modélisation du séchage du maïs en lit-fixe
Janas, Sébastien ULg

Doctoral thesis (2012)

Detailed reference viewed: 63 (25 ULg)
Full Text
See detailAnalyse moléculaire d'encres d'impression à des fins forensiques
Heudt, Laetitia ULg

Doctoral thesis (2012)

Document examination is a forensics field focused on the analysis of a disputed document. One way to analyze a document is to focus on the composition of the ink used or the materials from which documents ... [more ▼]

Document examination is a forensics field focused on the analysis of a disputed document. One way to analyze a document is to focus on the composition of the ink used or the materials from which documents are produced. Nowadays, three major classes of inks are studied: pen inks, inkjet printer inks, and toner. If the analysis of pen inks is already well developed in the literature and in the forensic lab, the analysis of inkjet printer inks is reported only to a limited degree and is principally focused on color inks. Fraudulent-minded people use more and more inkjet printer technology to produce falsified documents. So, it is a necessity to develop an analytical method for inkjet-printed document examination. Due to the particular chemical composition of these inks, different or more complicated analytical methods could and must be reviewed. Four analytical methods are evaluated in this thesis as possible tools for the analysis of inkjet-printed documents in terms of discriminating power, chemical information quality, and nondestructive capability: Raman spectroscopy and mass spectrometry coupled with Laser Desorption Ionization (LDI), Matrix Assisted Laser Desorption Ionization (MALDI), and Desorption ElectroSpray Ionization (DESI). The results obtained from two color inkjet printer cartridges (either fresh or printed) show that Raman spectroscopy and MALDI (9-aminoacridin as matrix) are the two most powerful methods for the analysis of color inkjet inks. Both methods have the advantage to perform analysis of inks directly on paper. The complementarity of the Raman spectroscopy and the MALDI-MS techniques is demonstrated based on the analysis of 10 different inkjet cartridges. The Raman method is a nondestructive approach while MALDI mass spectrometry has a better discrimination power and can also lead to information about some ink additives and paper composition. If it is necessary to determine the spatial distribution of one compound, then molecular imaging can be performed using Raman and (MA)LDI mass spectrometry. These techniques have been used successfully on a banknote or a stamp. Black inks are also under investigation in this work. The discrimination of black inkjet-printed documents is more difficult because of the common use of carbon black as the principal black pigment. LDI mass spectra recorded on black-printed inks give polyethylene glycol (PEG) peaks that are characteristics of a particular brand. Moreover, unknown characteristic peaks are detected in the low mass range of these spectra, giving additional information for discrimination of black inks. A software has been developed for a rapid and objective comparison of the low mass range of these positive mode LDI spectra. [less ▲]

Detailed reference viewed: 110 (29 ULg)
Full Text
See detailBayesian Design Space applied to Pharmaceutical Development
Lebrun, Pierre ULg

Doctoral thesis (2012)

Given the guidelines such as the Q8 document published by the International Conference on Harmonization (ICH), that describe the “Quality by Design” paradigm for the Pharmaceutical Development, the aim of ... [more ▼]

Given the guidelines such as the Q8 document published by the International Conference on Harmonization (ICH), that describe the “Quality by Design” paradigm for the Pharmaceutical Development, the aim of this work is to provide a complete methodology addressing this problematic. As a result, various Design Spaces were obtained for different analytical methods and a manufacturing process. In Q8, Design Space has been defined as the “the multidimensional combination and interaction of input variables (e.g., material attributes) and process parameters that have been demonstrated to provide assurance of quality” for the analytical outputs or processes involved in Pharmaceutical Development. Q8 is thus clearly devoted to optimization strategies and robustness studies. In the beginning of this work, it was noted that existing statistical methodolo- gies in optimization context were limited as the predictive framework is based on mean response predictions. In such situations, the data and model uncertainties are generally completely ignored. This often leads to increase the risks of taking wrong decision or obtaining unreliable manufactured product. The reasons why it happens are also unidentified. The “assurance of quality” is clearly not addressed in this case. To improve the predictive nature of statistical models, the Bayesian statistical framework was used to facilitate the identification of the predictive distribution of new outputs, using numerical simulations or mathematical derivations when possi- ble. By use of the improved models in a risk-based environment, separation analytical methods such as the high performance liquid chromatography were studied. First, optimal solutions of separation of several compounds in mixtures were identified. Second, the robustness of the methods was simultaneously assessed thanks to the risk-based Design Space identification. The usefulness of the methodology was also demonstrated in the optimization of the separation of subsets of relevant compounds, without additional experiments. The high guarantee of quality of the optimized methods allowed easing their use for their very purpose, i.e., the tracing of compounds and their quantification. Transfer of robust methods to high-end equipments was also simplified. In parallel, one sub-objective was the total automation of analytical method de- velopment and validation. Some data treatments including the Independent Com- ponent Analysis and clustering methodologies were found more than promising to provide accurate automated results. Next, the Design Space methodology was applied to a small-scale spray-dryer manufacturing process. It also allowed the expression of guarantees about the quality of the obtained powder. Finally, other predictive models including mixed-effects models were used for the validation of analytical and bio-analytical quantitative methods. [less ▲]

Detailed reference viewed: 72 (12 ULg)
Full Text
See detailCreation of model proteins to investigate the mechanism of aggregation of expanded-polyglutamine proteins. Insertion of polyglutamine tracts into the ß-lactamase BlaP
Scarafone, Natacha ULg

Doctoral thesis (2012)

Polyglutamine (polyQ) diseases are characterized by the formation of intranuclear amyloid-like aggregates by proteins containing an expansion of a polyQ tract above a threshold length. These insoluble ... [more ▼]

Polyglutamine (polyQ) diseases are characterized by the formation of intranuclear amyloid-like aggregates by proteins containing an expansion of a polyQ tract above a threshold length. These insoluble aggregates and/or some of their soluble precursors are thought to play a role in the pathogenesis of the diseases. The only known common point between the causative proteins is the expanded polyQ tract, suggesting that their aggregation critically depends on the expansion of the polyQ tract above a threshold length. Several studies have however shown that the non-polyQ regions can also influence the aggregation behavior of polyQ proteins. In this work, polyQ chimeras were created by inserting different polyQ lengths in two positions (197-198 and 216-217) of the β-lactamase BlaP from Bacillus licheniformis 749/C. The structural and thermodynamic properties of the polyQ chimeras as well as their aggregating properties under native and denaturing conditions were investigated using a range of biophysical techniques including fluorescence, circular dichroism, absorbance, x-ray fiber diffraction and transmission electron microscopy. We have first created and characterized chimeras with 23, 30, 55 and 79Q inserted in position 197-198 (chimeras 197-198). None of these insertions modifies the structure of BlaP; they do, however, significantly destabilize the enzyme by 7.6-8.8 kJ/mol independently of the polyQ length. Similarly to the proteins associated with diseases, there is a threshold number of glutamines above which the BlaP chimeras aggregate into amyloid-like fibrils. It is comprised between 55 and 79Q and between 30 and 55Q under native and denaturing conditions, respectively. This threshold value therefore depends on the structural integrity of BlaP and thus on the steric and/or conformational constraints applied by BlaP to the polyQ tract. We have then compared the properties of these chimeras with those of the chimeras containing polyQ of the same lengths in position 216-217 (chimeras 216-217). The tertiary structure of BlaP is slightly perturbed in the chimeras 216-217 and these chimeras are less stable than the chimeras 197-198. However, the urea-induced equilibrium unfolding experiments suggest that chimeras 216-217 populate a series of discrete intermediate states between the native and unfolded states or that their unfolded state significantly differs from that of chimeras 197-198. Finally, the aggregating properties of the polyQ chimeras 216-217 differ from those of chimeras 197-198. First, the threshold number of glutamines above which chimeras 216-217 readily form fibrils under native conditions (between 30 and 55Q) is lower than that observed for chimeras 197-198 (between 55 and 79Q) suggesting that the steric and/or conformational constraints imposed on the polyQ tract are lower when it is inserted in position 216-217. Secondly, the results obtained under both native and denaturing conditions indicate that the BlaP moiety could assist fibril formation by chimeras 216-217 while it has an inhibiting effect and no effect on fibril formation by the chimeras 197-198 with 55 and 79 glutamines, respectively. Taken together, these results show that the aggregating properties of BlaP chimeras result from a very complex interplay between the propensity of the polyQ tract to mediate fibril formation and the modulating effect of the BlaP moiety. BlaP chimeras present therefore valuable models to investigate in details how the properties of the host protein influence the aggregation behavior of expanded polyQ proteins. [less ▲]

Detailed reference viewed: 51 (21 ULg)
Full Text
See detailÉvolution du bilan de masse de surface Antarctique par régionalisation physique et conséquences sur les variations du niveau des mers
Agosta, Cécile ULg

Doctoral thesis (2012)

The Antarctic surface mass balance (SMB, i.e. the snow accumulation from which we sub- tract ablation by sublimation, run-off or erosion) is a major yet poorly known contribution to changes in the present ... [more ▼]

The Antarctic surface mass balance (SMB, i.e. the snow accumulation from which we sub- tract ablation by sublimation, run-off or erosion) is a major yet poorly known contribution to changes in the present-day sea level. Water storage by snow accumulation at the top of the ice- sheet is expected to increase during the 21st century, which would moderate the rise in sea level. Three-quarters of the Antarctic SMB are concentrated below 2000 m above sea level whereas this area represents only 40% of the grounded ice sheet area. Orographic precipitation is a major contributor to snow accumulation in this region, which is why a better estimation of this term is important. The representation of this process by models depends to a great extent on the resolu- tion of the model, since precipitation amounts depend on the ice sheet slopes. Sublimation and snowmelt also depend on elevation. Global and regional atmospheric climate models are unable to achieve a 40-km resolution over Antarctica at a century time scale, due to their computing cost. At this resolution, ice-sheet margins are still badly resolved. <br />That is why we developed the downscaling model SMHiL (surface mass balance high-resolution downscaling), which estimates the Antarctic SMB components at a high resolution (∼15 km) from large-scale atmospheric forcings. We compute the impact of the high-resolution topography on orographic precipitation amounts and on the boundary-layer processes that lead to sublima- tion, melting and refreezing. To validate SMHiL, we compare our results with more than 2700 field data recently updated and quality-controlled. However, we exhibit that field data below 2000 m above sea level are too scarce to settle SMHiL efficiency. In light of this, we show that the GLACIOCLIM-SAMBA stake lines located on the ice sheet coast-to-plateau area is an ap- propriate reference to evaluate model performance. Finally, we downscale the atmospheric global climate model LMDZ4 to estimate the SMB changes during the 21st and 22nd centuries. The high-resolution SMB is significantly different from the SMB given by LMDZ4. Our results sug- gest that running LMDZ4 at a finer resolution may give a future increase in SMB in Antarctica between 15% to 30% higher than at its standard resolution. Future changes in the Antarctic SMB at low elevations will result from the conflict between higher snow accumulation and ru- noff. The downscaling model is a powerful tool that can be applied to climate models for a better assessment of a future rise in sea level. [less ▲]

Detailed reference viewed: 14 (2 ULg)
Full Text
See detailAnalyse palynologique de divers sondages du secteur haute altitude du Parc National de Kahuzi-Biega: Paleoenvironnements et paleoclimats au Pleistocène supérieur et à l'Holocène
Kabonyi Nzabandora, Chantal ULg

Doctoral thesis (2012)

Palynological studies of sedimentary sequences issued from swamps located in the highlands of the KBNP (Kahuzi-Biega National Park) on the western divide of Kivu in Eastern Congo D.R., revealed important ... [more ▼]

Palynological studies of sedimentary sequences issued from swamps located in the highlands of the KBNP (Kahuzi-Biega National Park) on the western divide of Kivu in Eastern Congo D.R., revealed important environmental events that occurred during the last 35000 years. In the Upper Pleistocene, during the “Kalambo Interstadial” period (32000-26000 years BP), a mixed forest spread out under a moderately warm-wet climate. In the course of the “Mount Kenya Hypothermal” regressive phase (25000-15000 years BP), in the “Last Glacial Maximum” (20000-18000 years BP) takes place an exceptional expansion of open grasslands that evidenced an important drought. After that, the revival of an afro-montane forest growing under cold-wet climatic conditions is recorded, but that one is temporarily interrupted by theYoung Dryas dry pulse. At the Humid Holocene Period (10000-7000 years BP), with the increase of rainfall, the Kivu Lake level is raising when the swamps in the highlands are transformed in lakes. Around 6500 yrs BP, the afro-montane rainforest invaded by afro-subalpine taxa turns into a secondary mixed forest as the result of a climatic deterioration. At 4000 yrs BP, an important spreading of grasslands in the highlands and of savannas in the lowlands testifies that an aridity peak occurs at the time. The changes that occurs from 3000 years BP to 2000 years BP in the afro-montane forest suggests a climatic instability that moreover speeds up erosion processes. In the course of the first millennium AD, rainforest grows again; that event being shortly interrupted by a drought around 500 years AD. At the beginning of the second millennium AD, the lower belt of the forest is yet deteriorated by anthropic action while middle and upper belts are stable but marked by a fresh climate resulting of the “Mount Kenya Neoglacial” influence. From 17th – 18th centuries, human impact increases progressively in the highlands. On the eastern divide of Kivu, where seasons are more contrasted, the environmental events of the first part of Holocene are registered in the peaty sedimentary sequences. A heterogeneous forest evolved from 10000 years BP till 6000 years BP into an afro-montane rainforest by warming of a humid climate. Then, from the arid climatic phase of 4000 years BP till today, the various environmental events follow each other in the eastern as in the western side of the rift. [less ▲]

Detailed reference viewed: 46 (6 ULg)
Full Text
See detailBiohydrogen Production by the Citrobacter and Clostridium Genera : a Metabolic and Biomolecular Perspective
Hamilton, Christopher ULg

Doctoral thesis (2012)

The research activities described in this Thesis were carried out in the Walloon Centre of Industrial Biology at the University of Liege. Laboratory experiments were performed with Citrobacter freundii ... [more ▼]

The research activities described in this Thesis were carried out in the Walloon Centre of Industrial Biology at the University of Liege. Laboratory experiments were performed with Citrobacter freundii CWBI952, a facultative anaerobe of the Enterobacteriaceae family, and Clostridium butyricum CWBI1009, a strict anaerobe of the Clostridium genus, to produce hydrogen by dark fermentation of glucose in flasks and in bench-scale bioreactors maintained at 30°C. The aim of the research activities was not only to optimise the key determinants of H2 production, namely pH, nitrogen and iron concentrations, and the dilution rate, but also to gain a better understanding of the relatively unknown hydrogen production metabolism. This was done by monitoring the H2 production activity and tracking the net carbon and electron equivalent balances. The results for C. freundii CWBI952 (Chapter II) indicated that maximum hydrogen production activity, formate biosynthesis and glucose uptake rates were obtained at pH 5.9. Optimal overall performance (33.2 mLH2/L.h and 0.83 molH2/molglucose) was obtained in a semicontinuous culture with a dilution rate of 0.012 h-1. The best performance for C. butyricum CWBI1009 (Chapter V), i.e. 1.44 LH2/h and a yield of 2.02 molH2/molglucose, was associated with butyrate fermentation and obtained in a 20 L batch bioreactor at the optimal pH value of 5.2. For both of these strains we demonstrated that it should be possible to radically reduce nitrogen feedstock costs by replacing casein peptone with (NH4)2SO4, an ammoniacal substance closely related to the mineral nitrogen content of livestock manure. Additionally for C. butyricum CWBI1009 (Chapter III) we showed that a certain range of nitrogen content (0.56-0.062 gN/L) favours H2 production activity. This was confirmed by an analysis of the gene expression pattern, which suggested that the HydB2 gene was responsible for the H2 yield increase observed at 0.062 gN/L. Our investigations provided a better understanding of the highly diversified H2-production metabolism of C. butyricum CWBI1009 by mapping the distribution pattern for its carbon and electron fluxes (Chapters IV and V). This was done using three complementary approaches to study the metabolome (HPLC RID-UV), transcriptome (RT-qPCR and RNAseq) and the proteome (2D-DIGE). Tests under various different pH conditions showed that the role played by the different hydrogenases and the nitrogenase in H2 production varied substantially depending on the particular environmental conditions. At the end of the Thesis the discussion (Chapter VI) provides a general overview of the results obtained for the optimisation of the dark fermentation process parameters and an analysis of how these investigations have advanced our understanding of the metabolic processes involved. Potential industrial applications are reviewed and suggestions for further research are made. [less ▲]

Detailed reference viewed: 63 (20 ULg)
Full Text
See detailUsage de l’agriculture dans le social : Dispositifs, pratiques et formes d’engagement
Muramatsu, Kenjiro ULg

Doctoral thesis (2012)

This thesis deals with the ethnographical and sociological analyses of the modes of use of agriculture “in the social sphere”. Two Japanese and Belgian municipal actions are treated in parallel: The ... [more ▼]

This thesis deals with the ethnographical and sociological analyses of the modes of use of agriculture “in the social sphere”. Two Japanese and Belgian municipal actions are treated in parallel: The Centre for the Creation of Agri-rural Life (Nô-Life Sôsei Center in Japanese) launched in 2004 in Toyota City, which aims at the reinvigoration of fallow land and the promotion of the ikigai (“Life worth living”) for an aging population of permanent residents. In Belgium, the Work Training Initiative at Ferme Delsamme (Entreprise de Formation par le Travail Ferme Delsamme in French) launched in 2002 in La Louvière City, which aims at the socio-professional integration of at-risk adults through organic agriculture. Based on the analysis of forms of engagement of operators and users in their relationships of interaction and their efforts at adjustment of the tension, this thesis proposes the idea of “ethical” regimes of action that consist of a minimum number of principles for reflection and practice available to be used by actors. This thesis identified in particular the importance of two characteristic forms of these regimes: compassion (taking an infinite responsibility to address individuals in distress) amongst operators; social autonomy (the balance between individual autonomy and relational dependency based on the recognition of vulnerability and fragility) amongst users. Agricultural activity is defined here as the intermediate space supporting the combination and the performance of these regimes that are not very visible and formalized, and difficult to objectify and justify. [less ▲]

Detailed reference viewed: 134 (12 ULg)
Full Text
See detailPerspectives on parameters influencing entrepreneurial intentions
Heuer, Annamaria ULg

Doctoral thesis (2012)

Detailed reference viewed: 33 (3 ULg)
Full Text
See detailEtude des facteurs écologiques influençant la croissance et le développement des Pectobacterium spp. infectant les tubercules de pomme de terre.
Moh, Ahoussi Augustin ULg

Doctoral thesis (2012)

Pectobacterium atrosepticum (Pba) and Pectobacterium carotovorum subsp. carotovorum (Pcc) are the main cause of potato tuber decay (soft rot) in storage and stem rot in the field (blackleg). It has been ... [more ▼]

Pectobacterium atrosepticum (Pba) and Pectobacterium carotovorum subsp. carotovorum (Pcc) are the main cause of potato tuber decay (soft rot) in storage and stem rot in the field (blackleg). It has been reported that ecological parameters such as humidity and temperature, greatly influence the disease development. The objective of the present study was to evaluate and model the growth of two phytopathogens bacteria (Pba and Pcc) under various ecological conditions at the level of wounded potatoes tubers. To this purpose, we adopted two experimental approaches named in vitro approach and in vivo approach. We determined in vitro the effect of water activity (0.960, 0.980 and 0.997) and temperature (10, 15 and 20°C) and their interactions on the growth parameters and pectate lyases (PEL) specific activity of Pba and Pcc using optical density (OD) measurement. Statistical analysis showed a significant effect of aw and temperature on µmax. Our result showed an increase of PEL specific activity with the temperature whatever the bacterial strains. But contrary to the bacterial growth, this research did not show an increase of PEL specific activity with aw except the treatment at 15 and 20°C for the two bacteria strains. According to our results on growth and PEL production, we concluded that Pba and Pcc had the same behaviour in the range of the values of the two factors (aw and temperature) investigated here. The studies made in vivo were consisted to evaluate and model the influence of temperature (10, 15 and 20°C), relative humidity (86, 96 and 100%) and initial concentration of bacterial inoculum (105, 107 and 109 CFU/ml) on the population density of Pba and Pcc, and on the development of soft rot symptoms caused by these bacteria at the surface of wounded potatoes tubers. With both bacterial species, statistical analysis showed a significant effect of temperature, relative humidity and initially applied bacterial concentration on population dynamics and soft rot development at the surface of wounded potato tubers. Multiple regression analyses and the contour plots showed that the temperature is the most important factor, followed by the initially applied bacteria concentration and relative humidity. More than 64% of the variability of the soft rot symptoms observed could be explained by the presence of Pba and Pcc at the level of wounded potato tubers under the combined effect of tested factors. The quadratic polynomial models developed (in vitro and in vivo) in our research, by means of the response surface methodology, should integrate in further research the large genetic variation (which was not evaluated in this investigation) within Pectobacterium genus (Pba and Pcc) and Dickeya spp. [less ▲]

Detailed reference viewed: 132 (16 ULg)
Full Text
See detailProduction de biohydrogène par fermentation anaérobie chimiotrophe de substrats carbohydratés
Hiligsmann, Serge ULg

Doctoral thesis (2012)

Hydrogen (H2) is being considered as an ideal and clean energy carrier since the utilization of hydrogen, either via combustion or via fuel cells, results in pure water. The recent advances to produce ... [more ▼]

Hydrogen (H2) is being considered as an ideal and clean energy carrier since the utilization of hydrogen, either via combustion or via fuel cells, results in pure water. The recent advances to produce biohydrogen from renewable sources such as biomass and particularly by fermentation of carbohydrate-rich substrates from agriculture and agro-industries appear promising. Such a process called “dark fermentation” enables both organic waste treatment and renewable energy production to be coupled. In the thesis different hydrogen-producing microorganisms were studied and some environmental parameters and bioreactors have been investigated in order to improve the hydrogen production yields and rates. The experimental results compared the hydrogen production yield of 19 different pure strains and sludges : facultative and strict anaerobic H2-producing strains along with anaerobic digester sludges thermally pre-treated (to enrich the microflora in high H2-producers) or not. Significant yields variations were recorded even between different strains of the same species (up to 20% of variation). The pure Clostridium butyricum (C. but.) strains achieved the highest yields i.e. up to 172 L H2 produced per kilogram of glucose consumed (1.38 mol H2 / mol glucose). Two efficient H2-producing strains (C. but. CWBI1009 and Citrobacter freundii CWBI952) were further studied in order to determine the optimum culture conditions for the production of hydrogen. A 2.3 L bioreactor was operated at 30 °C in batch and sequenced-batch mode using glucose and starch as substrates. For glucose the maximum yield (211 L H2 / kg or 1.7 mol H2 / mol glucose) was measured with the C. but. strain when the pH was maintained at 5.2. In sequenced-batch reactor a 35% increase in H2 yield was obtained with removal–addition of 40% of the culture medium at the beginning of each sequence. For operation in continuous mode, original bioreactors such as an anaerobic biodisc reactor (AnBDR) were designed to both fix biomass and enable rapid liquid to gas transfer of hydrogen produced since H2 partial pressure and H2 supersaturation are known as hardly affecting hydrogen production performances. The highest and stable H2 production rate (703 L H2 per hour and per m³ of liquid volume inside the bioreactor) and yield (302 L / kg glucose consumed i.e. 2.4 mol/mol) with the pure culture of C. but. CWBI1009 were recorded in the AnBDR with 300 mL culture medium (total volume 2.3 L) at pH 5.2 and a glucose loading rate of 2.87 kg / m³.h. These results achieved with pure strains are relevant compared to the highest H2 yields and rates reported in the literature with mixed cultures and achieved in reactors, such as trickle bed bioreactors, with high gas transfer performances. Moreover, the soluble metabolites, mainly acetate and butyrate, contained in the spent medium of the dark fermentation bioreactor were efficiently converted to methane in a second anaerobic digester (20 L continuously stirred tank) with a methane yield of about 170 L/kg COD initially fed in the first stage. These results demonstrate that a two-step anaerobic digestion process may be carried out in two successive bioreactors, both with specific and optimized parameters, in order to generate separated biogas flows containing either H2 or CH4. In addition to the advantages related to both gaseous molecule properties, many technological improvements would be achieved by this way : better hydrolysis, higher process stability, etc. The general discussion highlights the central and relevant position of the 2-stage anaerobic digestion process in the panorama of technologies able to both treat raw or residual organic matter and to produce energy or energy vectors for stationary or mobile end-use. The technical, economical and environmental aspects have been considered. [less ▲]

Detailed reference viewed: 263 (36 ULg)
Full Text
See detailRobustness analysis of clustering and classification techniques
Ruwet, Christel ULg

Doctoral thesis (2012)

As mentioned in the title, the framework of this doctoral dissertation encompasses two different subjects: robust statistics on the one hand and classification and clustering techniques on the other hand ... [more ▼]

As mentioned in the title, the framework of this doctoral dissertation encompasses two different subjects: robust statistics on the one hand and classification and clustering techniques on the other hand. Robust procedures try at the same time to emulate classical procedures and to produce results that are not unduly affected by contaminated observations or deviations from model assumptions. Classification and clustering techniques try to find groups among observations. Grouping is one of the most basic abilities of living creatures; the simple fact of naming objects is already grouping. The main interest lies in the fact that the characteristics of a group as well as its differences from other groups can be used as a summary of the dataset. [less ▲]

Detailed reference viewed: 85 (40 ULg)
Full Text
See detailLectures, réécritures et peintures à partir de Pline l’Ancien. La réception de l’Histoire naturelle en Italie, de Pétrarque à Vasari
Bert, Mathilde ULg

Doctoral thesis (2012)

This study examines the way in which the information given by Pliny the Elder in his Natural History concerning classical painting were perceived and exploited in Renaissance Italy, from Petrarch (c. 1350 ... [more ▼]

This study examines the way in which the information given by Pliny the Elder in his Natural History concerning classical painting were perceived and exploited in Renaissance Italy, from Petrarch (c. 1350) until the second edition of Vasari’s Lives (1568). It shows that references to Pliny that are discernible in various texts and works of art are means for us to understand some of the artistic, theoretical, and social issues inherent in pictorial practice at the time. Many different types of sources have been exploited in carrying out this research. In the first instance, information concerning the editorial transmission of the Natural History has been examined. Reception of Book XXXV, dedicated to classical painting, has been given special attention, particularly through the analysis of Renaissance copies of Pliny’s so-called Encyclopaedia, and the annotations, translations, derivations and commentaries to which this work gave rise at the time. Recourse to Pliny in artistic literature and in pictorial practice is then examined. Finally, the emulation of Apelles in artistic practise is considered through a study of the signature in the imperfect. This is, in fact, a way of signing paintings that Pliny attributes to the Greek painter and which artists in the Renaissance would adopt from the end of the fifteenth century. In addition to the substantial consideration given to Petrarch, Alberti, Ghiberti, Castiglione, Pino, Dolce and Vasari, this study also analyses references to Pliny in many other artists and humanists, such as Boccaccio, Guglielmo da Pastrengo, Villani, Guarino, Leonardo Giustiniani, Decembrio, Fazio, Landino, Perotti, Santi, Leonardo, Jacopo de’ Barbari, Bellini, Costa, Macrino d’Alba, Palmezzano, Raphael, Titian, Sebastiano del Piombo, Andrea del Sarto, Giovio, Damiano Zambelli, Aretino, Varchi, Giovio, l’Anonimo Magliabechiano and Giovanni Battista Adriani. Thus, via a series of individual and comparative readings that draw out the many links between art and humanism, this study highlights the various different forms that borrowings from Pliny could take, and the functions they had, as well as emphasising the main themes for which those borrowings were exploited, such as commentary on the cultural and social development of painting, and reflection on genres and pictorial styles (portrait, landscape, female nude, the debate about disegno and colorito, and the paragone of the arts). [less ▲]

Detailed reference viewed: 138 (13 ULg)
Full Text
See detailLe corps du détenu : Études psychopathologiques de l’homme en situation
Englebert, Jérôme ULg

Doctoral thesis (2012)

Cette thèse de doctorat a pour premier objet d’étude la psychopathologie. Et nous estimons qu’une telle entreprise ne peut se concevoir qu’en situation (voici son second objet). Une prise en considération ... [more ▼]

Cette thèse de doctorat a pour premier objet d’étude la psychopathologie. Et nous estimons qu’une telle entreprise ne peut se concevoir qu’en situation (voici son second objet). Une prise en considération rigoureuse des « phénomènes psychiques anormaux » (Jaspers, 1913) implique une conception de l’homme en tant qu’être incarné, inscrit dans un espace et un temps, au risque, sinon, de se limiter à une simple nosographie ou à une clinique sans dimension pratique. Notre propos ne se limite pas à penser que l’environnement du sujet influence son trouble – cet élément est déjà, nous semble-t-il, bien acquis – ; nous estimons plutôt, d’un certain point de vue, que « La » psychopathologie, hypothétique science transcendantale, n’existe tout simplement pas. Le phénomène psychopathologique, par nature multiple et polymorphe, nécessite une réflexion épistémique approfondie et réclame l’émergence d’autres alternatives au paradigme empiriste afin de rompre « avec l'idolâtrie du sujet épistémologique anonyme sans situation » (Ricœur, 1957, p. 10). Faire nôtre cette proposition d’études psychopathologiques de l’homme en situation nous permet de pouvoir écrire cette thèse et de l’inscrire dans une généalogie relative. Le « gage de sûreté » que représente le paradigme situationnel nous permet de ne pas nous « perdre » en tentant de répondre à ces questions de façon générale. Il s’agirait d’ailleurs d’une entreprise impossible que de définir la subjectivité, de lui donner une acception commune. Par contre, appréhender la subjectivité incarnée d’un sujet et la considérer comme objet d’étude à part entière, semblent constituer des objectifs dotés d’un intérêt majeur. La situation permet de « mettre au travail » la psychopathologie, véritable moment où elle prend forme et existe réellement. Le situationnel et l’événementiel sont également la possibilité qui s’offre à nous de ne pas répéter des choses que d’autres auraient mieux dites ; ce sont les garanties de l’intérêt à poursuivre la recherche en psychopathologie. Théoriser à la suite de ces nombreuses références n’aurait de sens s’il n’y avait ce prétexte de la situation, tant un sentiment de « déjà dit » pourrait anesthésier et rendre vaine toute tentative. Notre situation, c’est notre alibi. Pour réaliser ce projet, nous avons séparé notre étude en deux livres. Le premier est consacré à différentes situations cliniques en milieu carcéral. Il contient huit chapitres. Tous sont la mise en application autant que la création d’une méthode, que nous qualifions de phénoménologique, appropriée à l’analyse de situations rencontrées dans notre pratique de psychologue clinicien en milieu carcéral. Le second livre est fait de deux chapitres construits chacun en trois parties. Cette seconde partie consiste en une formalisation anthropologique de ce qu’est un homme en prison. Nous avons étudié, entre autres, les dimensions de l’espace, du temps, du corps, de l’imaginaire pour parvenir à un essai de définition de ce que nous appelons l’univers carcéral et discuter du statut de l’identité carcérale. Ces différents points de repère nous ont permis d’aborder la question de la subjectivité et de la sensation qui sont des contrées d’une complexité fondamentale que le psychologue se refuse souvent d’affronter dans le domaine de la recherche, mais auxquelles il est pourtant confronté quotidiennement dans sa pratique clinique. C’est avec l’esthétique, à travers les peintures de Bacon, les photographies de Nollet et Huis clos de Sartre que nous avons refermé cette thèse. Cet achèvement ouvre la réflexion vers la pratique clinique centrée sur le champ inépuisable, même en prison, de la liberté. Nous avons pu, à cet effet, constater le surgissement de la résistance, de l’agencement, et considérer le principe d’adaptation sous un jour nouveau. Enfin, nos dernières lignes ont permis l’émergence du concept oxymore de « liberté carcérale » qui caractérise l’homme en situation d’enfermement. [less ▲]

Detailed reference viewed: 224 (33 ULg)
Full Text
See detailVariations on the Kalman filter for enhanced performance monitoring of gas turbine engines
Borguet, Sébastien ULg

Doctoral thesis (2012)

Since their advent in the 1940's, gas turbines have been used in a wide range of land, sea and air applications due to their high power density and reliability. In today's competitive market, gas turbine ... [more ▼]

Since their advent in the 1940's, gas turbines have been used in a wide range of land, sea and air applications due to their high power density and reliability. In today's competitive market, gas turbine operators need to optimise the dispatch availability (it i.e., minimise operational issues such as aborted take-offs or in-flight shutdowns) as well as the direct operating costs of their assets. Besides improvements in the design and manufacture processes, proactive maintenance practices, based on the actual condition of the turbine, enable the achievement of these objectives. Generating dependable information about the health condition of the gas turbine is a requisite for a successful implementation of condition-based maintenance. In this thesis, we focus on the assessment of the performance of the thermodynamic cycle, also known as Module Performance Analysis. The purpose of module performance analysis is to detect, isolate and quantify changes in engine module performance, described by so-called health parameters, on the basis of measurements collected along the gas-path of the engine. Generally, the health parameters are correcting factors on the efficiency and the flow capacity of the modules while the measurements are inter-component temperatures, pressures, shaft speeds and fuel flow. Module performance analysis can be cast as an estimation problem that is characterised by a number of difficulties such as non-linearity of the system and noise and bias in the measurements. Moreover the number of health parameters usually exceeds the number of gas-path measurements, making the estimation problem underdetermined. This thesis starts with a survey of the state-of-the-art in module performance analysis. We then propose enhancements to a monitoring tool for steady-state data developed by Dr. P. Dewallef during his thesis at the Turbomachinery Group. Specifically, the improvements concern the fault detection and isolation tasks, respectively handled by a hypothesis testing and a sparse estimator. As a complement, we define metrics for the selection and analysis of sensor--health parameter suites based on the Information Theory. In a second step, we investigate the feasibility and the benefit that could be expected from the processing of data collected during transient operation of a gas turbine. We also discuss the impact of modelling errors on the estimation procedure and propose a solution that makes the health assessment robust with respect to modelling errors. The theoretical developments are evaluated on the basis of simulated test-cases through a series of metrics that gauge the estimation accuracy and the performance of the fault detection and isolation modules. [less ▲]

Detailed reference viewed: 104 (22 ULg)
Full Text
See detailApplication d’un modèle d’analyse de l’interaction ventriculo-artérielle à la défaillance hémodynamique
MORIMONT, Philippe ULg

Doctoral thesis (2012)

L’utilisation du modèle hémodynamique d’interaction ventriculo-artérielle au lit du malade, à la place des approches intuitives dépourvues de signification physiologique réelle, est un défi. La nécessité ... [more ▼]

L’utilisation du modèle hémodynamique d’interaction ventriculo-artérielle au lit du malade, à la place des approches intuitives dépourvues de signification physiologique réelle, est un défi. La nécessité de recourir à des mesures hautement invasives et à des variations de pré-charge reste une contrainte difficile chez des patients instables. Les recherches présentées dans cette thèse montrent que les indices nécessaires à l’application du modèle peuvent aussi être obtenus à partir de mesures ou de signaux utilisés usuellement en soins intensifs à condition de respecter des conditions précises. [less ▲]

Detailed reference viewed: 17 (2 ULg)
Full Text
See detailContribution à la désinfection de l'eau par photosensibilisation avec des extraits de plantes
Sunda Makuba, Teddy ULg

Doctoral thesis (2012)

La problématique de l’accès à l’eau par les populations des pays en développement constitue toujours de nos jours un défi important à relever pour contribuer à un développement durable tout en ... [more ▼]

La problématique de l’accès à l’eau par les populations des pays en développement constitue toujours de nos jours un défi important à relever pour contribuer à un développement durable tout en garantissant des conditions sanitaires satisfaisantes. Malgré les Objectifs du Millénaire pour le Développement (OMD), de nombreux pays souffrent encore actuellement d’un manque d’accès à l’eau. En République Démocratique du Congo, seuls 26% de la population a accès à l’eau. Au-delà de la satisfaction des besoins humains assurés par la fourniture de la quantité d’eau nécessaire, il s’agit aussi de veiller à garantir sa bonne qualité, particulièrement la qualité microbiologique. Parmi les divers procédés de désinfection de l’eau au niveau familial, la présente contribution a pour objectif l’amélioration de la méthode de désinfection solaire par application du processus de photosensibilisation. En présence de lumière, un photosensibilisateur génère dans l’eau l’oxygène singulet très réactif conduisant à la destruction des microorganismes. Certaines plantes utilisées dans la pharmacopée traditionnelle pour soigner les infections microbiennes et parasitaires sont capables d’initier cette réaction de photosensibilisation. Dans un premier temps, parmi une dizaine de plantes analysées, nous avons mis en évidence l’activité photosensibilisante d’extraits non alcaloïdiques de Cassia alata, Cassia occidentalis, Carica papaya, Phyllanthus niruri et Coleus kilimandschari. L’inactivation des coliformes fécaux a été remarquée après trois heures d’ensoleillement, celle-ci se manifestant après une heure d’exposition lorsque le milieu est saturé en oxygène. Tout en étant libéré de la contrainte liée à la saturation du milieu en oxygène, l’étude des huiles essentielles extraites de plantes de la famille des Rutacées a montré une inhibition complète des coliformes fécaux présents dans l’eau après deux heures d’ensoleillement pour Citrus reticulata et Citrus limonum et une heure d’ensoleillement pour Citrus bergamia. L’examen de cette dernière huile en spectrométrie de masse a mis en évidence la présence de méthoxy-5 psoralène (MOP-5), responsable de l’activité photosensibilisatrice. Utilisé en solution dans l’eau, le MOP-5 a confirmé son rôle de photosensibilisateur et son efficacité désinfectante avec un abattement de 4 unités logarithmiques pour les Coliformes fécaux après une heure d’exposition et de 3 unités logarithmiques pour les Entérocoques fécaux après seulement 5 minutes d’exposition. La fixation du MOP-5 sur un support solide a permis de récupérer le photosensibilisateur après usage tout en conservant son pouvoir désinfectant supérieur à la forme libre. Le dispositif MOP-5/polystyrène a permis d’observer une inhibition complète des Coliformes fécaux après seulement 6 minutes d’exposition et deux minutes pour les Entérocoques fécaux. Cette recherche constitue un premier travail exploratoire qui ouvre la voie vers un nouveau processus de désinfection de l’eau par photosensibilisation à partir d’extraits de plantes. Mais il conviendra de préciser les modalités pratiques d’application afin de rendre ce processus opérationnel. [less ▲]

Detailed reference viewed: 112 (11 ULg)
Full Text
See detailÉtude de la structure et des propriétés de gels à base d’oxyde de titane en relation avec leurs mécanismes de formation
Bodson, Céline ULg

Doctoral thesis (2012)

Dans le contexte général du développement, au Laboratoire de Génie Chimique, de nouveaux photocatalyseurs à base de TiO2 présentant une activité sous lumière UV-Vis améliorée, l’objectif de ce travail ... [more ▼]

Dans le contexte général du développement, au Laboratoire de Génie Chimique, de nouveaux photocatalyseurs à base de TiO2 présentant une activité sous lumière UV-Vis améliorée, l’objectif de ce travail consiste à étudier les mécanismes de formation mis en jeu lors de leur synthèse et de leur dopage par la méthode sol-gel de cogélification. Plusieurs dopants, contenant du silicium, du phosphore ou de l’argent, ont été utilisés. L’influence des variables opératoires de synthèse sur les propriétés physicochimiques, et de là sur les propriétés photocatalytiques des xérogels obtenus, a été examinée en détail. La compréhension de cette relation a permis d’ouvrir la voie à la synthèse de photocatalyseurs à base de TiO2 combinant différents dopages et présentant des activités élevées. Le développement de nouveaux dopants à base de porphyrines fonctionnalisées par des groupements phosphonatés a également été réalisé en vue de leur incorporation ultérieure dans les gels de TiO2. L’obtention d’un gel ou d’un précipité dépend des cinétiques des réactions d’hydrolyse et de condensation du tétraisopropoxyde de titane (TIPT). Le recours à un solvant chélatant a permis de ralentir la cinétique des ces réactions et donc d’obtenir un gel. Ces xérogels sont cependant non poreux après séchage. L’insertion, lors d’une synthèse par cogélification, d’un additif silylé ou phosphonaté contenant une éthylènediamine ralenti également la cinétique des réactions via un mécanisme de complexation du TIPT. Dans ce cas, il est possible d’obtenir un gel poreux dans un solvant non chélatant, et non un précipité. Ce résultat est très intéressant car il a été prouvé que lors du dopage du TiO2 avec du phosphore par cogélification, la formation du gel est importante car elle s’accompagne d’un degré élevé d’hétérocondensation (liaisons P-O-Ti), contrairement à la formation des précipités. Afin d’éliminer les résidus organiques encore présents à l’issue du séchage et de cristalliser le TiO2 en anatase, les échantillons doivent être calcinés. L’influence de la température de calcination sur les propriétés des photocatalyseurs a été examinée en détail. Dans les échantillons calcinés, des propriétés telles que la taille des cristallites d’anatase, la surface spécifique et le spectre d’absorption UV-Vis sont principalement influencés par la teneur en phosphore. Pour maîtriser cette dernière, il est important de maximiser le degré d’hétérocondensation entre le TIPT et l’additif phosphonaté (EDAP). En effet, lors de la calcination, l’EDAP non intégré au réseau de TiO2 via des liaisons Ti-O-P, se décompose en dessous de 350 °C et du phosphore est perdu par sublimation de P2O5. Parmi les dopages étudiés, seul celui au P permet de déplacer le spectre d’absorption du TiO2 vers les plus grandes longueurs d’onde. Lors du test de dégradation du p-nitrophénol sous lampe halogène, les xérogels de TiO2 dopé au P calcinés donnent de meilleurs résultats que le xérogel de TiO2 pur ou encore que ceux dopés à l’Ag uniquement. L’influence intrinsèque du phosphore sur l’activité photocatalytique a été confirmée par une étude statistique. Cette étude montre également que l’activité dépend de la teneur en phosphore via son influence sur la taille des cristallites d’anatase et sur la surface spécifique des xérogels. Cette activité est d’autant plus élevée que la taille des cristallites est petite et que la surface spécifique est élevée. Afin de maximiser les performances photocatalytiques du TiO2 sous lampe halogène, un co-dopage à l’Ag et au P a été réalisé pour essayer de combiner l’effet bénéfique du P sur l’activité sous lumière visible et celui de l’Ag sur la vitesse de recombinaison des paires électron-trou. L’utilisation d’une molécule comme l’EDAP, capable de complexer l’ion Ag+, permet d’obtenir dans le matériau final des nanoparticules d’Ag finement dispersées dans les particules de TiO2. Le co-dopage à l’Ag et au P permet d’augmenter de manière très significative l’activité des xérogels de TiO2 pour la dégradation du p-nitrophénol sous lampe halogène. Cette augmentation résulte d’un effet synergique entre les deux additifs. Le dernier chapitre de ce travail est une étude préliminaire pour ouvrir la voie au dopage du TiO2 avec des porphyrines fonctionnalisées par des groupements phosphonatés ou silylés via la méthode de cogélification. Cette étude a permis de mettre au point des protocoles de synthèse de porphyrines phosphonatées et de porphyrines aminées. Ces porphyrines aminées serviront de précurseurs pour l’obtention de porphyrines silylées. [less ▲]

Detailed reference viewed: 64 (13 ULg)
See detailSois belle et tais-toi: la bienveillance sexiste comme outil de discrimination
Sarlet, Marie ULg

Doctoral thesis (2012)

Doit-on encore, en 2012, s'inquiéter des préjugés et de la discrimination basés sur le genre? Si oui, ceux-ci doivent-ils nécessairement revêtir une forme hostile pour engendrer des conséquences négatives ... [more ▼]

Doit-on encore, en 2012, s'inquiéter des préjugés et de la discrimination basés sur le genre? Si oui, ceux-ci doivent-ils nécessairement revêtir une forme hostile pour engendrer des conséquences négatives pour les femmes qui en sont les cibles? Dans cette thèse, nous allons nous intéresser à ces préjugés et, plus particulièrement, à une forme particulière de sexisme, le sexisme bienveillant, qui renvoie à des attitudes sexistes subjectivement positives, teintées de galanterie et de condescendance (Glick & Fiske, 1996). Au travers des différents chapitres, nous allons nous demander si cette forme de sexisme, bien qu’elle puisse sembler anodine, peut être considérée comme un outil susceptible de contribuer au maintien des inégalités entre les genres. Le Chapitre 1 nous permettra de justifier l’importance qu’il y a encore de nos jours d’accéder à une meilleure compréhension du sexisme. Un aperçu de la situation respective des femmes et des hommes en Belgique soulignera la persistance, au sein des différentes sphères de vie, des inégalités entre les genres, se marquant très souvent en défaveur des femmes. La contribution du sexisme dans l’explication de ces inégalités sera illustrée par différentes études empiriques. De façon plus générale, nous nous intéresserons au processus de stigmatisation et à ses conséquences pour les personnes qui en sont les cibles. Dans le Chapitre 2, nous nous focaliserons sur la théorie du Sexisme Ambivalent (Glick & Fiske, 1996) qui suggère que le sexisme est bidimensionnel, comprenant une composante de bienveillance, le sexisme bienveillant, et une composante d’hostilité, le sexisme hostile. Ce chapitre dressera les définitions conceptuelle et opérationnelle de ces deux formes de sexisme ainsi que leurs origines. Ensuite, une revue de la littérature soutiendra la définition du sexisme bienveillant en tant que préjugé malgré une apparence qui peut sembler anodine, voire avantageuse pour les femmes. Nous définirons le sexisme bienveillant en tant qu’idéologie traditionnelle décrivant les femmes comme sociables et incompétentes (Fiske, Cuddy, Glick, & Xu, 2002), idée reflétée dans le titre de cette thèse : sois belle et tais-toi. Le sexisme bienveillant sera donc présenté comme un véritable processus de maintien des inégalités sociales entre les genres se basant sur un paradoxe : il semble valoriser les femmes, mais les défavorise pourtant dans leur position sociale. Dans les chapitres suivants, nous investiguerons deux grandes questions. Premièrement, nous étudierons les mécanismes par lesquels le sexisme bienveillant est susceptible de contribuer au maintien de la subordination des femmes dans le milieu professionnel (Chapitres 3 à 6). Dans un second temps, nous nous demanderons par quels processus le sexisme bienveillant est maintenu au sein des relations entre les genres (Chapitre 7). Pour répondre à notre première question, nous testerons l’hypothèse selon laquelle le sexisme bienveillant, en milieu professionnel, induirait chez les femmes une internalisation mais aussi une confirmation comportementale des croyances stéréotypiques les décrivant comme sociables et incompétentes. Le Chapitre 3 s’intéressera à l’impact du sexisme bienveillant sur la dimension stéréotypique de sociabilité. Dans un premier temps, nous observerons, au travers d’une tâche de mémoire autobiographique, l’impact de l’activation du sexisme bienveillant sur le concept de soi des femmes en termes de traits positifs liés à la sociabilité (Etude 1). Ensuite, nous testerons l'idée que l’adhésion personnelle des femmes au sexisme bienveillant les conduirait à privilégier des stratégies de promotion de soi mettant en évidence des traits positifs liés à la dimension de sociabilité et nous en observerons les conséquences sur leur orientation professionnelle (Etude 2). Dans le Chapitre 4, nous considérerons l’impact du sexisme bienveillant sur la dimension stéréotypique de compétence. Nous verrons si l’exposition au sexisme bienveillant en milieu professionnel déplace le concept de soi des femmes vers l’incompétence, ce que nous opérationnaliserons par une mesure de pensées intrusives et par une tâche de mémoire autobiographique. Nous nous intéresserons, par ailleurs, à l’impact du sexisme bienveillant sur la suppression de pensées intrusives et sur les performances cognitives des femmes grâce au Reading Span Test (Daneman et Carpenter, 1980). Dans les Chapitres 5-6, nous utiliserons des mesures plus implicites pour évaluer les conséquences engendrées par l’exposition au sexisme bienveillant en milieu professionnel. Dans le Chapitre 5, nous utiliserons une tâche de Stroop (MacLeod, 1991) nous permettant d’étudier les fonctions exécutives des femmes soumises au sexisme bienveillant. Par ailleurs, l’utilisation d’une tâche de Stroop modifiée approfondira l’étude du contenu des pensées intrusives induites par l’exposition au sexisme bienveillant. Nous observerons notamment si le sexisme bienveillant active simultanément, dans l’esprit des femmes, des pensées intrusives liées à la sociabilité et à l’incompétence, regroupant ainsi les hypothèses de nos chapitres 3 et 4. Dans le Chapitre 6, nous utiliserons le dispositif de l’Imagerie par Résonance Magnétique fonctionnelle (IRMf) afin d’étudier les substrats neuronaux impliqués par l’exposition au sexisme bienveillant en milieu professionnel. Plus exactement, nous nous focaliserons sur les aires cérébrales associées au contrôle mental (i.e., cortex préfrontal dorsolateral et cortex cingulaire antérieur). Le Chapitre 7 nous permettra d’investiguer notre seconde question : comment le sexisme bienveillant est-il maintenu au sein des relations entre les genres ? Au travers de cinq études, nous envisagerons un mécanisme susceptible de participer à ce maintien: la prescription de comportements paternalistes faite aux hommes (ex. les hommes doivent se montrer protecteurs envers les femmes). Nous considérerons également la prescription de comportements égalitaristes faite aux hommes (Etudes 1 à 3). Au travers de ce chapitre, nous prendrons en compte une variable contextuelle qui est la sphère (romantique ou professionnelle) dans laquelle s’expriment les comportements des hommes (Etudes 1 à 5). Par ailleurs, nous nous intéresserons à la façon dont ces comportements sont interprétés en fonction du contexte considéré (Etude 4) et le rôle que joue le niveau personnel d’adhésion des femmes aux idéologies sexistes bienveillantes sur leur prescription (Etude 5). Le Chapitre 8 consistera en un chapitre de discussion générale et de conclusions. Nous y présenterons des données supplémentaires récoltées au cours de cette thèse, mettrons en évidence les forces et faiblesses de notre travail ainsi que certaines explications alternatives. Nous envisagerons également différentes pistes de recherche pour les explorations futures. [less ▲]

Detailed reference viewed: 55 (8 ULg)
Full Text
See detailNumerical simulations of brittle and elasto-plastic fracture for thin structures subjected to dynamic loadings
Becker, Gauthier ULg

Doctoral thesis (2012)

The main purpose of this thesis is the development of a framework to model fracture initiation and propagation in thin bodies. This is achieved by the combination of two original models. On one hand ... [more ▼]

The main purpose of this thesis is the development of a framework to model fracture initiation and propagation in thin bodies. This is achieved by the combination of two original models. On one hand, (full) discontinuous Galerkin formulations of Euler-Bernoulli beams as well as Kirchhoff-Love shells are established. These formulations allow modeling a thin structure with discontinuous elements, the continuity being ensured weakly by addition of interface terms. The first advantage of the recourse to a discontinuous method is an easy insertion of cohesive elements during the simulation without a modification of the mesh topology. In fact with a continuous method, the insertion of the cohesive elements at the beginning of the simulation leads to numerical issues and their insertion at onset of fracture requires a complex implementation to duplicate the nodes. By contrast, as interface elements are naturally present in a discontinuous formulation their substitution at fracture initiation is straightforward. The second advantage of the discontinuous Galerkin formulation is a simple parallel implementation obtained in this work by exploiting, the discontinuity of the mesh in an original manner. Finally, last advantage of the recourse to a discontinuous Galerkin method for thin bodies is to obtain a one field formulation. In fact, the C1 continuity is ensured weakly by interface terms without considering rotational degrees of freedom. On the other hand, the through-the-thickness crack propagation is complicated by the implicit thickness model inherent to thin bodies formulations. Therefore we suggest an original cohesive model based on reduced tresses. Our model combines the different reduced stresses in such a way that the expected amount of energy is released during the crack process leading to a model which respects the energetic balance whatever the applied loadings. The efficiency of the obtained framework is demonstrated through the simulation of several benchmarks whose results are in agreement with numerical and experimental data coming from the literature. Furthermore, the versatility of our framework is shown by simulating 2 very different fracture phenomena: the crack propagation for elastic as well as for elasto-plastic behavior and the fragmentation of brittle materials. This demonstrates that our framework is a powerful tool to study dynamics crack phenomena in thin structure problems involving a large number of degrees of freedom. [less ▲]

Detailed reference viewed: 229 (54 ULg)
Full Text
See detailModélisation des tensions circonférentielles en simulation méridienne d'écoulements en turbomachines
Thomas, Jean-Philippe ULg

Doctoral thesis (2012)

The systematic use of three-dimensional Navier-Stokes simulations being too demanding in turbomachinery design phase, throughflow simulation, two-dimensional, simpler and faster, is used extensively on an ... [more ▼]

The systematic use of three-dimensional Navier-Stokes simulations being too demanding in turbomachinery design phase, throughflow simulation, two-dimensional, simpler and faster, is used extensively on an industrial scale. However, its limitation is its need for empirical information to reproduce the action of the blades and the effect of three-dimensional components of the flow, higher-order elements compared to the classical throughflow. We propose to lead to a decrease of empiricism needed by the classical throughflow by obtaining this information autonomously. Obtaining information of a circumferential order may be considered in resolving all the components of the flow with a purely three-dimensional code or by accommodating an approximate solution with a reduced numerical cost, the way chosen in this contribution. To do this, we propose to extend to the circumferential case the He's "nonlinear harmonic method", of proved efficiency in the case of approximate reproduction of unsteadiness. Adapting this technique to the throughflow model passes through a reformulation of the presence of blades. Indeed, the use of Fourier series requires a continuous circumferential evolution of flow, prohibiting the existence of local impermeability condition. To work around this feature of the circumferential case, the effect of the blades is modeled by a force field sufficiently continuous and formalized by the Peskin's "immersed boundary method". The validation of the new technique, resulting from an innovative combination of the harmonic and immersed boundary methods inside a throughflow code, is performed on the case of inviscid flow around a cylinder. It illustrates the capabilities of the harmonic throughflow to access higher order information, that enrich the mean flow but also make available the circumferential view of the flow from the Fourier modes resolved. Finally, the harmonic throughflow is applied to a stator airfoil and a single-stage compressor. It is shown that after adjusting the model to the specific geometry of thin profiles, it is possible to access information of higher order. In particular, the model captures the potential characteristics of circumferential non-uniformities on the entire vein and the viscous characteristics near meridional walls. [less ▲]

Detailed reference viewed: 57 (5 ULg)
Full Text
See detailEtude de la glycoprotéine L de l'herpèsvirus bovin 4 et de sa protection vis-à-vis des anticorps neutralisants
Lété, Céline ULg

Doctoral thesis (2012)

L’herpèsvirus bovin 4 (BoHV-4) appartient à la famille des Herpesviridae qui comprend un nombre important de pathogènes classés en trois sous-familles (alpha-, beta, et gamma-herpesvirinae) (Ackermann ... [more ▼]

L’herpèsvirus bovin 4 (BoHV-4) appartient à la famille des Herpesviridae qui comprend un nombre important de pathogènes classés en trois sous-familles (alpha-, beta, et gamma-herpesvirinae) (Ackermann, 2004). Parmi les gammaherpèsvirus, l’Epstein Barr virus (EBV) et l’herpèsvirus associé au sarcome de Kaposi (KSHV) sont responsables de pathologies humaines importantes. Etant donné que ces deux virus se multiplient mal in vitro et n’ont pas de modèle in vivo, le BoHV-4 représente un modèle plus accessible pour l’étude de ces pathogènes humains. Etant donné que les herpèsvirus sont réexcrétés après qu’une réponse immune spécifique se soit mise en place, ces virus ont dû développer un cycle d’infection élaboré leur permettant d’échapper à la neutralisation par les anticorps spécifiques de l’hôte. Comme les anticorps neutralisants agissent principalement en bloquant l’entrée des virions au sein des cellules cibles, il est nécessaire, afin d’améliorer le contrôle de ces infections, de connaître avec précision les mécanismes d’entrée de ces virus au sein des cellules cibles. Contrairement à la plupart des virus enveloppés qui n’utilisent qu’une seule protéine de fusion pour l’entrée, les herpèsvirus utilisent un complexe de fusion conservé composé des glycoprotéines gB, gH et gL (Connolly et al., 2011). La glycoprotéine gB, essentielle à l’infection chez les herpèsvirus, est une protéine de fusion de classe III(Roche et al., 2007). Cependant, gB seule ne peut opérer la fusion et requiert la présence des glycoprotéines gH et gL associées en hétérodimère. Ce complexe est une cible majeure de neutralisation chez plusieurs herpèsvirus (Gill et al., 2006) indiquant son implication dans l’entrée du virus. Plusieurs études rapportent que gH pourrait avoir un rôle effecteur dans la fusion et agir comme une glycoprotéine de fusion de classe I(Gianni et al., 2005). Cependant, la récente cristallisation du complexe gH/gL chez l’HSV-2 et l’EBV (Chowdary et al., 2010; Matsuura et al., 2010) suggère que celui-ci n’agit vraisemblablement pas comme co-fusogène mais intervient plutôt pour réguler la fusion de gB. Quant à la glycoprotéine gL, son rôle propre est controversé. Certains auteurs soutiennent que gL n’agit qu’en tant que protéine chaperon pour gH (Hutchinson et al., 1992), d’autres affirment qu’elle est également impliquée dans l’attachement (Gillet et al., 2008b). Considérée comme essentielle jusqu’à présent, une étude a récemment montré que la gL de l’herpèsvirus murin 4 (MuHV-4) est non essentielle pour l’infection (Gillet et al., 2007b). Afin de mieux comprendre les mécanismes d’entrée des gammaherpèsvirus au sein de leurs cellules cibles et dès lors pouvoir mieux combattre ces infections, ce travail a été consacré à l’étude de la glycoprotéine L du BoHV-4. Il s’articule en 3 volets. Le premier volet étudie l’implication de gL dans l’entrée virale. La seconde partie étudie gL en tant que cible potentielle de neutralisation. Enfin, dans le dernier volet de ce travail, nous nous sommes intéressés plus spécifiquement à la protection de la glycoprotéine L vis-à-vis des anticorps neutralisants.   1. La glycoprotéine L de l’herpèsvirus bovin 4 est non essentielle pour l’infectivité mais déclenche l’endocytose des virions pendant l’entrée. Afin d’étudier les conséquences fonctionnelles de l’absence de gL sur l’infection par le BoHV-4, nous avons généré un virus recombinant déficient pour la glycoprotéine gL. Les virions dépourvus de gL présentent une altération de la glycosylation de gH et une incorporation moindre de gH au sein des virions, bien que ceux-ci restent infectieux. L’absence de gL s’accompagne d’un important retard de croissance virale associé à un déficit d’entrée. Ce déficit d’entrée survient à une étape postérieure à l’attachement mais antérieure à la fusion. Enfin, grâce à la réalisation de marquages immunofluorescents de virions lors de l’entrée dans la cellule cible, nous avons pu montrer que ce déficit d’entrée associé à l’absence de gL est lié à un retard d’endocytose et à un défaut de migration vers les endosomes tardifs de la cellule. En conclusion, la glycoprotéine L du BoHV-4 est non essentielle mais intervient dans l’endocytose des virions attachés en surface cellulaire. 2. Etude de la glycoprotéine gL en tant que cible de la neutralisation. Au cours de la deuxième étude, nous avons voulu déterminer l’implication de gL dans le cycle naturel du virus et dans la neutralisation de celui-ci. Une expérience in vivo réalisée chez le lapin a mis en évidence que l’absence de gL n’avait pas d’impact significatif sur l’établissement et le maintien de la latence du BoHV-4. Nous avons également montré que l’absence de gL n’affectait pas quantitativement la réponse humorale à l’encontre du BoHV-4. Par contre, des expériences de neutralisation menées avec des séra provenant de lapins infectés avec la souche sauvage ou avec la souche n’exprimant plus la glycoprotéine L ont montré l’importance de la glycoprotéine L dans la ,neutralisation virale. En effet, l’absence d’anticorps dirigés contre la gL ou contre des épitopes dépendant de sa présence réduisait de manière importante le pouvoir neutralisant des séra. Nous avons donc pu conclure que la glycoprotéine L, ou des épitopes dépendants de sa présence, sont des cibles majeures de neutralisation. 3. Etude de la protection de la glycoprotéine L vis-à-vis des anticorps neutralisants. Parmi les mécanismes de résistance des virus à la neutralisation, plusieurs études ont mis en évidence l’utilisation de boucliers de glycans (« Glycan shield ») par différents virus(Lee et al., 2008a; Wei et al., 2003b). Nous nous sommes donc intéressés au rôle des glycans dans l’évasion par le BoHV-4 des anticorps neutralisants. Nous avons dans un premier temps montré que les glycans protègent de la neutralisation. Nous avons ensuite identifié, grâce à la réalisation du protéome structural du BoHV-4 en collaboration avec l’équipe du Professeur Wattiez, 4 protéines massivement glycosylées au sein du virion à savoir gB, gL, gH et gp 180. Nous nous sommes d’abord intéressés à gp 180, celle-ci étant la protéine potentiellement la plus glycosylée. Nous avons montré que gp 180 est massivement O-glycosylée et que les virus n’exprimant plus gp 180 sont plus neutralisés par le sérum que les virus sauvage et révertant. De plus, l’absence de gp180 augmente l’accessibilité des glycoprotéines gB, gH et gL à leur anticorps spécifiques. Gp180 et ses glycans semble donc jouer le rôle de « glycan shield » à la surface du BoHV-4. En parallèle, nous avons investigué le rôle de la glycosyltransférase encodée par le gène Bo17 du BoHV-4. Nous avons montré que la glycoprotéine gp 180 est une des cibles de cette glycosyltransférase. Etant donné que le gène Bo17 subit un phénomène d’épissage alternatif qui génère soit une protéine entière enzymatiquement active soit une protéine plus courte dont l’activité enzymatique est supprimée, nous avons généré et caractérisé des virus recombinants n’exprimant que la forme longue ou que la forme courte de Bo17. Grâce à ces virus, nous avons pu montrer que le BoHV-4, via le splicing alternatif du gène Bo17, est capable de moduler la glycosylation de gp180. Dans le futur, nous voulons étudier les conséquences de ces observations sur la neutralisation du BoHV-4. Ce travail devrait nous permettre de comprendre le rôle potentiel de Bo17 et de son épissage dans la biologie de l’infection par le BoHV-4. En conclusion, ce travail a permis de mettre en évidence la complexité du mécanisme d’entrée des gammaherpèsvirus nécessaire à la protection des épitopes vulnérables de la neutralisation par les anticorps. Ce travail a aussi démontré l’importance de la O-glycosylation dans ce processus. Les données générées ont illustré la complexité des interactions glycans-virus-cellules hôtes et ont constitué une première base pour des perspectives tant fondamentales qu’appliquées. [less ▲]

Detailed reference viewed: 80 (18 ULg)
Full Text
See detail« Abandonner le contrôle sans perdre le contrôle ». Une investigation du rôle de la confiance des subordonnés envers leur manager comme levier potentiel du contrôle organisationnel
De Zanet, Fabrice ULg

Doctoral thesis (2012)

Toute organisation souhaite que ses salariés remplissent au mieux leurs missions. Les moyens mis en œuvre pour s’en assurer sont étudiés dans un champ disciplinaire appelé le contrôle organisationnel dont ... [more ▼]

Toute organisation souhaite que ses salariés remplissent au mieux leurs missions. Les moyens mis en œuvre pour s’en assurer sont étudiés dans un champ disciplinaire appelé le contrôle organisationnel dont la finalité est d’inciter les salariés à agir dans l’intérêt de leur organisation. Par ailleurs, parce que les organisations évoluent dans un contexte se caractérisant par davantage d’incertitude et d’interdépendance, elles ne peuvent plus se contenter d’attendre que leurs salariés se conforment à des procédures ou comportements précisément définis. Dès lors, elles confient à leurs managers la délicate mission de contrôler leurs subordonnés tout en les incitant à aller au-delà de ce qui est attendu d’eux et à contribuer activement aux objectifs de l’organisation. Ces managers sont alors confrontés à un dilemme : comment « abandonner le contrôle sans perdre le contrôle » ? Dans le cadre de cette thèse, nous abordons la question du contrôle organisationnel à travers le rôle clé des managers. Nous postulons que les managers capables de gagner la confiance de leurs subordonnés peuvent accomplir plus facilement leur mission de contrôle organisationnel. A travers trois études empiriques, nous examinons comment les managers contribuent au développement de la confiance et comment la confiance des subordonnés envers leur manager les incite à agir dans l’intérêt de leur organisation. L’originalité de notre travail est de se situer à la croisée de différentes disciplines, à savoir la théorie des organisations, le contrôle de gestion et le comportement organisationnel. [less ▲]

Detailed reference viewed: 124 (36 ULg)
Full Text
See detailA Tool for Design Decision Making Zero Energy Residential Buildings in Hot Humid Climates
Attia, Shady ULg

Doctoral thesis (2012)

Informed decision-making is the basis for the design of Net Zero Energy Buildings (NZEBs). This thesis investigates the use of building performance simulation tools as a method of informing the design ... [more ▼]

Informed decision-making is the basis for the design of Net Zero Energy Buildings (NZEBs). This thesis investigates the use of building performance simulation tools as a method of informing the design decision of NZEBs. The aim of this study was to develop a design decision making tool, ZEBO, for zero energy residential buildings in hot climates and to evaluate the effect of a simulation-based decision aid, on informed decision-making using sensitivity analysis. An assessment of the role of the BPS tools used in informing the decision-making was ascertained through cases studies, usability testing and several self-reported metrics. The thesis provides results that shed light on the effectiveness of sensitivity analysis as an approach for informing the design decisions of NZEBs. [less ▲]

Detailed reference viewed: 542 (2 ULg)
Full Text
See detailExperimental Investigation of the Aerodynamics and Aeroelasticity of Flapping, Plunging and Pitching Wings
Norizham, Abdul Razak ULg

Doctoral thesis (2012)

This thesis concerns the experimental analysis of the aerodynamics and aeroelasticity of oscillating wings. It is divided into two sections, an inves- tigation of wings undergoing imposed root flapping ... [more ▼]

This thesis concerns the experimental analysis of the aerodynamics and aeroelasticity of oscillating wings. It is divided into two sections, an inves- tigation of wings undergoing imposed root flapping and pitching motion, such as seen in avian flight and an experimental investigation of the self- excited stall flutter oscillations of a wing undergoing plunging and pitching motion. The objective of the flapping wing investigation is to improve the under- standing of the unsteady aerodynamics of flapping flight. The work con- sists of designing and building a flapping and pitching bird-like mechanical model and testing it in a low speed wind tunnel. The model’s size is sim- ilar to that of a goose. The wind tunnel tests involved the measurement of forces, power, kinematics and local flow velocities using Particle Im- age Velocimetry (PIV). The mechanical model was tested at four different frequencies and three airspeeds. In addition, three different wing profiles were tested. The kinematic modes included pure flapping and combined flapping and pitching. It was shown that pure flapping and pitch-lagging combined motion can lead to interesting aerodynamic phenomena, such as flow separation and dynamic stall. Dynamic stall can cause significant increases in instantaneous lift production, although it also generates a lot of drag. On the contrary, pitch leading combined motion can generate a net propulsive force over the entire cycle. In the stall flutter study, a 6 degree of freedom NACA 0018 wing was sus- pended by springs in the wind tunnel. The wing was then exposed to an airflow at a number of airspeeds and wind-off angles of attack. The wing was instrumented with pressure sensors and accelerometers. In addition, PIV flow measurements were carried out on the wing’s upper surface. The work demonstrates that stall flutter is the result of a combination of dy- namic stall with the elastic properties of the system. The dynamic stall mechanism was studied using the PIV measurements and was found to be different to the classical stall mechanisms that are reported in the litera- ture. The sensitivity of the stall flutter phenomenon to parameters such as airspeed and wind-off angle of attack is demonstrated by means of a two-parameter bifurcation diagram. [less ▲]

Detailed reference viewed: 83 (8 ULg)
Full Text
See detailCorpus et catégorisation. Perspective linguistique sur les genres en néo-égyptien
Gohy, Stéphanie ULg

Doctoral thesis (2012)

Le corpus néo-égyptien a suscité - et suscite encore – un large intérêt, sans toutefois attacher suffisamment d’attention à la définition du corpus. Dans bon nombre d’études, l’appellation « néo-égyptien ... [more ▼]

Le corpus néo-égyptien a suscité - et suscite encore – un large intérêt, sans toutefois attacher suffisamment d’attention à la définition du corpus. Dans bon nombre d’études, l’appellation « néo-égyptien » a longtemps été réservée aux textes de la pratique censés refléter au mieux la langue parlée. À vrai dire, si l’étude du néo-égyptien a suscité un certain engouement dans le milieu égyptologique, deux perspectives ont généralement été envisagées :  une vision englobante : l’étude du néo-égyptien se fait à partir d’un corpus étendu, sans aucune restriction particulière et sans prêter attention aux genres des textes, à la diachronie ou à l’état de langue employé ;  une vision restrictive : l’étude du néo-égyptien s’appuie sur un corpus réduit, en tenant compte de critères préalablement définis comme la diachronie, le lieu géographique ou le genre (littéraire >< non littéraire). Quelques études ont également été consacrées à un genre de texte particulier. Une étude manquait donc encore ; aucun travail de recherche n’avait envisagé l’étude du corpus néo-égyptien selon une perspective diachronique large, sans restriction entre textes littéraires et non littéraires, et en tenant compte des genres. Dans ma thèse, j’ai donc proposé de définir le corpus néo-égyptien comme suit : il s’agit d’un ensemble de textes s’inscrivant dans différents genres dans lesquels s’actualisent différents registres d’expression. Dès lors, la définition du corpus néo-égyptien passait nécessairement par la définition des genres et des registres d’expression employés au sein de ce corpus. On le sait, chaque texte s’inscrit dans un genre qui va imposer des règles/normes codifiant ce genre. Ce sont ces normes, ces règles qu’il s’agissait de mettre en avant. Je me suis donc attelée à définir ces genres, c’est-à-dire mettre en évidence les critères qui les définissent, spécifier les fonctionnements propres aux différents genres afin d’établir leur « carte d’identité ». C’est la base de données Ramsès qui a servi de corpus de référence à mon étude. À chacun des textes a été attribué un genre a priori. Il est vite apparu que dans l’examen des normes imposées par le genre, de nombreux critères pouvaient être mobilisés, toutefois, j’ai décidé de concentrer mes recherches sur quatre critères de définition : la phraséologie, la diplomatique (particulièrement, les formules d’incipit et d’explicit), le répertoire, l’emploi de l’encre rouge. L’examen de ces 4 critères a donc permis de mettre en évidence quelques-unes des normes codifiant les différents genres et, par la même occasion, d’assurer la pertinence de la classification proposée. [less ▲]

Detailed reference viewed: 168 (17 ULg)