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See detailEstimation of diet digestibility and intake by grazing ruminants through near infrared reflectance spectroscopy analysis of faeces. Application in various contexts of livestock production
Decruyenaere, Virginie ULg

Doctoral thesis (2015)

Grazing is the most economical feeding scheme for ruminants. Grazing management, however, is often difficult for breeders, particularly because of a lack of knowledge about grass availability and quality ... [more ▼]

Grazing is the most economical feeding scheme for ruminants. Grazing management, however, is often difficult for breeders, particularly because of a lack of knowledge about grass availability and quality. There are methods for assessing the quantitative and qualitative characteristics of grass, but they are difficult to apply in the case of grazing ruminants. Near infrared reflectance spectroscopy (NIRS) is based on the absorption of infrared light by organic matters to provide NIRS spectra. These NIRS spectra can be correlated with the chemical or biological composition of samples in order to develop calibrations that can be used as predictive models. The primary objective of this PhD thesis was to study the potential of NIRS applied to faeces (FNIRS) in order to predict the characteristics of the diets of grazing herbivores. The particular focus was on the in vivo organic matter digestibility, voluntary intake and botanical composition of ingested diets. The main results of the study show that FNIRS has great portential for estimating in vivo digestibility and voluntary intake by grazing ruminants and that faeces are a good indicator of ingested diets. Based on both large or small and varied databases, the results suggest that FNIRS spectral libraries could be developed for characterising ruminant feed intake. The accuracy of the FNIRS models in estimating in vivo digestibility and voluntary intake is similar to or better than that of other methods usually used to assess these parameters. FNIRS could also be used to predict ruminants’ diet composition in terms of plant species. These predictions should be used only for ranking, however, because of the current lack of accurate procedures for determining diet selection individually. NIRS applied to faeces can be used to predict the in vivo characteristics of forage with sufficient accuracy. The prediction error of NIRS calibrations depends on the accuracy and precision of the reference data. The prediction of in vivo digestibility and intake is sufficiently repeatable compared with the procedure using the reference method. Intake is more difficult to predict with sufficient precision and is more closely linked to animal variability and to uncertainty of the FNIRS models. The major difficulty in using this method lies in generating the diet-faecal pairs as reliably as possible. FNIRS calibrations for predicting in vivo diet characteristics are derivative calibrations. The sample analysed for reference values (diet samples) differs from the samples submitted to NIRS analyses (faeces). With regard to research on forages, in vivo trials with animals confined in pens or digestibility crates appears to be the best reference method for generating FNIRS calibrations. Future work will involve developing FNIRS calibrations for predicting independent datasets and using them to create decision-support tools for improving diverse grazing management schemes. The major focus should be to compare different feeding strategies rather than to obtain an exact estimate of feed intake values. As a low-cost and rapid prediction technique, FNIRS could contribute significantly to the development of a methodology that would help improve our knowledge of forage and animal variability. [less ▲]

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See detailTranscriptomic analysis of pancreatic cells in zebrafish
Tarifeño Saldivia, Estefanía ULg

Doctoral thesis (2015)

Pancreas is a mixed gland composed of endocrine and exocrine tissues and plays a crucial role in the metabolism of all vertebrates. The endocrine cells are mainly grouped into the islets of Langerhans and ... [more ▼]

Pancreas is a mixed gland composed of endocrine and exocrine tissues and plays a crucial role in the metabolism of all vertebrates. The endocrine cells are mainly grouped into the islets of Langerhans and secrete distinct hormones, such as glucagon (α-cell), insulin (β-cell), somatostatin (δ-cell) and ghrelin (ε-cell). Diabetes occurs when insulin production by the β-cells is unable to counteract increase of glycemia. The goal of the first part of my thesis was to determine the transcriptomic signatures of each pancreatic cell type in zebrafish in order to identify novel cell type-specific regulatory genes that might be crucial for their differentiation and/or physiology. Pancreatic acinar cells, ductal cells as well as the endocrine α-, β- and δ-cells were isolated from different transgenic adult zebrafish using FACS and RNA-seq was performed from these highly purified cell types. Comparison between the RNA-seq datasets allowed us to highlight all genes (protein coding and non-coding genes) with enriched expression in each cell type and to identify new markers of the mature pancreatic cells in zebrafish. In order to establish the expression blueprint of pancreatic endocrine and exocrine cells conserved from fish to mammals, we compared the pancreatic transcriptomes from zebrafish, mouse and human. Using pancreatic RNA-seq data available in databases, we determined the set of genes displaying enriched expression in endocrine and exocrine cells of human and mouse. Comparison of these data with the zebrafish pancreatic endocrine and exocrine data revealed the genes with conserved expression among vertebrates. Most of the transcription factors previously known to be important for pancreatic cell differentiation are included in this set of conserved genes. This interspecies comparative analysis highlighted genes with evolutionary conserved expression whose pancreatic function is still unknown, but also revealed striking differences in gene expression patterns between species. The goal of the second part of my thesis was to understand the global transcriptional change produced by the loss-of-function of pax6b in pancreatic endocrine cells during pancreas development in zebrafish. We performed RNA-seq from purified pancreatic endocrine cells from wild-type and mutant (pax6b sa0086 null allele) zebrafish embryos at 27 hpf. By comparing the transcriptome of wild-type and mutant endocrine cells, we identified thousands of genes differentially expressed. Notably, we observed that the expression level of the pancreatic hormones was affected as it was reported in murine models. These analyses have revealed the transcriptional network regulated by pax6b in endocrine cells during differentiation. These analyses highlighted many unknown pax6b targets and novel regulators possibly involved in pancreatic function. Future functional analyses will be needed to further investigate the function of the novel regulators identified by this study. [less ▲]

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See detailEcologie et connaissances ethnozoologiques de quelques espèces d'oiseaux gibiers menaces des ecosytèmes du Sud du Bénin
Lougbegnon, Olou Toussaint ULg

Doctoral thesis (2015)

The natural areas of the south of Benin under subequatorial climate are diversified in resident birds’ species as well as migratory one. Some of them are hunted for food and therapeutic purposes by ... [more ▼]

The natural areas of the south of Benin under subequatorial climate are diversified in resident birds’ species as well as migratory one. Some of them are hunted for food and therapeutic purposes by grassroots communities. The most used are Guttera pucherani, Dendrocygna viduata, Egretta alba, Egretta ardesiaca, Porphyrio alleni et Porphyrio porphyrio. In order to reduce pressure on biodiversity in this part of Benin and to implement the sustainable conservation of birds’ species, this study on ecology and ethno-zoological knowledge of hunted bird species was carried out in the forest areas and the Ramsar sites 1017 and 1018. Field prospections were conducted from 2009 to 2012. The birds’ inventory method used was based on listening point techniques of 15 minutes. Data analysis were analyzed through the computation of bird species abundances, the establishment of maps distribution of the species, the habitat description and the modeling of the climatic niche of these species under climatic models CCCMA (Canadian Centre for Climate Modeling and Analysis) and CSIRO (Commonwealth Scientific and Industrial Research Organization) using MAXENT3.3.2. The ethno-zoological knowledge of the birds species were assessed through individual and groups survey and allowed to calculate the use values of the different part of the birds’ species according to the socio-cultural groups, sex and age. Moreover a logistic binary regression was carried out to determine the socio-economic factors which affect bird species exploitation by the grassroots communities. Results of modeling showed that among the variables selected for the prediction of the climatic models, distance from river, altitude appeared as the environmental variable which more contributed to the prediction of the models (with an average of 74.32 % and 12.94%). Projection under CCCMA and CSIRO in 2050, showed a progression of the favorable areas to Dendrocygna viduata, Porphyrio alleni, Porphyrio alleni, Egretta ardesiaca while it showed a regression of the favorable areas to Egretta alba. The estimated uses values showed that the ethno-zoological knowledge on the bird species differed according to the ethnic groups. Birds are used for food, medicinal and magico-mystics purposes. The magico-mystics and food were the most frequent used categories. Homogeneity of knowledge was found among the informants regarding the ethnic group as well as for the sex with respectively 0.66 and 0.7 for the use diversity value (ID) and use equitability value (IE). No significant difference was found between the informant for the use diversity value (ID) and use equitability value (IE). This study helps to build a database on 6 birds’ species and can be used for bird game ranching and game farming in Benin. [less ▲]

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See detailScène d'énonciation et posture d'auteur: la mise en scène de soi dans la critique littéraire de Baudelaire
Mogollon Zapata, Juan Manuel ULg

Doctoral thesis (2015)

Il y aurait un Baudelaire réaliste, un décadent, un classique, un catholique, un révolutionnaire, un réactionnaire et même un postmoderne. Les images attribuées à l’auteur se superposent selon l’époque ... [more ▼]

Il y aurait un Baudelaire réaliste, un décadent, un classique, un catholique, un révolutionnaire, un réactionnaire et même un postmoderne. Les images attribuées à l’auteur se superposent selon l’époque, le lieu et les courants esthétiques et politiques dans lesquels il a été lu. Mais quelle image Baudelaire construit-il de lui-même dans ses textes critiques ? Comment s’y présente-t-il à son public ? Pour mieux cerner le visage littéraire de cette figure changeante et paradoxale, l’étude proposée ici cherche à démontrer qu’il existe bel et bien dans la critique littéraire de Baudelaire un travail de mise en scène de soi qui ne peut se comprendre qu’à partir des diverses scènes d’énonciation que le poète-critique a capitalisées tout au long de sa carrière. Cela soulève la question de la relation entre, d’un côté, la présentation de soi et la scène de parole dans laquelle elle s’inscrit et qu’elle aide à construire, et de l’autre, entre cette mise en scène discursive de soi et les stratégies de positionnement de l’auteur à l’intérieur du champ littéraire. Dans quelle mesure ce travail de présentation de soi est-il redevable de la "situation de discours" dans laquelle il s’énonce ? Et, corollairement, dans quelle mesure relève-t-il d’une stratégie de positionnement littéraire ? Dès que l’on constate que le choix d’une posture, ou de diverses postures au fil du temps, est à la fois lié à une scène d’énonciation, à une étape socioprofessionnelle et à un répertoire de rôles et de modèles prêts à être investis, on entre dans la logique de construction d’une œuvre, mais aussi d’une identité littéraire. [less ▲]

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See detailLe vécu des femmes magistrates en Belgique francophone. Analyse d'une profession sous l'angle des rapports sociaux de sexe. Représentativité, profils et pouvoir
Cornet, Adeline ULg

Doctoral thesis (2015)

Sachant qu’historiquement l’exercice de la Justice a été réservé aux hommes, et que les femmes n'ont accès, en Belgique, que depuis un peu moins de 70 ans à la magistrature ; la question centrale de cette ... [more ▼]

Sachant qu’historiquement l’exercice de la Justice a été réservé aux hommes, et que les femmes n'ont accès, en Belgique, que depuis un peu moins de 70 ans à la magistrature ; la question centrale de cette recherche doctorale s’attache à étudier l’impact de l’arrivée des femmes dans la magistrature et de leur exercice de cette fonction régalienne et de pouvoir, ainsi que de leur vécu personnel et professionnel. Choix a été fait d’aborder cette question centrale suivant une méthodologie qualitative et l’utilisation de récits de vie ; et les résultats obtenus y répondent à travers trois grands axes analytiques pouvant être résumés en trois questions : 1/ Combien sont ces magistrates et « où sont-elles » ? Quelle a été l'évolution numérique des femmes dans la magistrature au cours du temps ? Quels postes et quelles fonctions occupent-elles ? 2/ Qui sont les magistrates et comment se définissent-elles ? Quels sont leurs profils et leurs trajectoires professionnelles ? Quel sens, quelles significations donnent les magistrates à leur profession et à la place qu'elle tient dans leur vie ? Quel est leur vécu ? 3/ Quelle vision ont les magistrates du pouvoir ? Et comment se positionnent-elles face à cet attribut central de leur profession ? Ces analyses, réalisées à travers la comparaison des parcours et vécus des quarante-neuf magistrates interrogées, se veulent être une première étude de genre de cette profession visant à connaître qui sont ces magistrates, la place qu'elles occupent dans la profession, la manière dont elles l'envisagent et lui donnent sens. [less ▲]

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See detailLe financement de l’agriculture au Bénin : stratégies de gestion et d’adaptation des exploitations agricoles
Sossou, Comlan Hervé ULg

Doctoral thesis (2015)

Benin is highly dominated by agriculture: about 80 % of the population are rural and involved in farming activities. The challenge now is to create suitable conditions for the improvement and ... [more ▼]

Benin is highly dominated by agriculture: about 80 % of the population are rural and involved in farming activities. The challenge now is to create suitable conditions for the improvement and competitiveness of farming systems and the creation of small and medium enterprises along the different chains of agricultural value. One such challenge involves facilitating the access of farmers and other stakeholders, to input markets, products and especially financial services. This highlights the need to establish an optimal framework for financing agricultural activities based on lessons learned from current experiences and using the best recent institutional innovations in the field. This thesis focuses on the issue of funding for agriculture and strategies developed by producers and other stakeholders including the public sector. To understand agricultural activities financing problems in rural areas, a research was conducted from 2010 to 2014. The research targets are farms and their access to financial services. A survey of 475 farms was conducted in 2011. In 2014, a deepening phase was performed on 40 farms. Research results revealed that financial needs of farms are not totally satisfied. The loans granted are small amounts, mostly. Productive investments that constitute investments in medium and long term, which can lead to significant improvements in agricultural production, are almost unsatisfied. Moreover, analysis showed that income determines access to credit. This factor reflects to a certain level the ability of farmers to provide the financial guarantees required by microfinance institutions. Also, producer's ability to invest and to provide the required guarantees, his loyalty and compliance with the rules of microfinance institutions (MFIs) facilitate access to high loan amounts. Analysis also showed that credit rationing affects a large number of producers. The consequence of this rationing is the reduction in agricultural inputs use, in hired labour, in acreage, etc. And therefore, decrease in yields and producers incomes. In summary, current conditions offered by microfinance institutions is not conducive to agricultural development and livelihoods improvement of rural populations. It is therefore necessary to rethink agricultural activities funding and develop a sustainable financing mechanism for both producers and funding agencies. To this end, the initiative for the establishment of a National Fund for Agricultural Development (NFAD) should be accelerated to allow farmers easier access to credit and adequate. [less ▲]

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See detailEtude des principes supranationaux de prévention des conflits armés - Exemple du système éducatif primaire de Prishtina (Kosovo)
Pierre, Alexia ULg

Doctoral thesis (2015)

The Unmik, United Nations Mission in Kosovo, was launched in the aftermath of mass violations of War Law and of International Humanitarian Law, perpetrated by the Republika Srpska against the Albanian ... [more ▼]

The Unmik, United Nations Mission in Kosovo, was launched in the aftermath of mass violations of War Law and of International Humanitarian Law, perpetrated by the Republika Srpska against the Albanian civilian of Kosovo. The Unmik was mandated to prevent the interethnic violence and to neutralise the roots of conflict, and to let emerge a new society where intercommunity antagonisms do not exist anymore. The mass education appears to be a tool that leads to a sustainable development of society. Therefore, the International Community links education and conflict prevention due to the role of education in social integration and development, and through specific contents. The supranational principles of education to conflict prevention are framed by an international framework, mostly developed in the nineties. Finally, education was at stake and was instrumentalised by the nationalist propagandas during the conflict between Serbs and Albanian in Kosovo. The main object of this research is to explore the way these principles of education to conflict prevention are operationalized in the primary public education system in Kosovo, through the study case of the main city Prishtina. The premise is that the operationalization can carry some boundaries to the complete expression of these supranational principles. The first step was dedicated to the research of the supranational principles in a normative and legislative corpus of local texts. The second step was a study of the expression of the principles of prevention in the primary public schools of Prishtina and with some members of the education system of Kosovo. This work highlights the sustainability of the operationalized principles on the formal and structural stages, due to the integration in the local normative and legislative frame. However, the operationalization can lead to an incomplete or a limited expression of the principles of an education involved in the conflict prevention. The top down approach of the Unmik and its lack of practical application of the principles are important elements in the limited expression of these principles. The boundaries are linked to the failure in questioning the education model applied in Kosovo as well, and to the assumptions it carries. Finally, the inadequate support to the educational staff and the inadequacy of this education model to the specificities of Kosovo are equally major factors of the limited operationalization of the supranational principles of conflict prevention in the primary schools of Prishtina. [less ▲]

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See detailEtude des apports de l'épidémiologie participative à l'évaluation des systèmes de surveillance en santé animale
Calba, Clémentine ULg

Doctoral thesis (2015)

Les systèmes de surveillance en santé animale sont mis en place dans le but de répondre à des enjeux de santé publique et de santé animale, ils permettent également de limiter les pertes économiques et de ... [more ▼]

Les systèmes de surveillance en santé animale sont mis en place dans le but de répondre à des enjeux de santé publique et de santé animale, ils permettent également de limiter les pertes économiques et de préserver la biodiversité. Du fait de l’importance capitale de ces systèmes tant au niveau national qu’international, il est fondamental de mettre en place des évaluations régulières et pertinentes afin de s’assurer de leurs performances, mais également dans le but de déterminer si les ressources fournies sont utilisées de manière optimale. Différents guides ont été développés afin d’accompagner les évaluateurs dans cette démarche, en santé animale tout comme en santé humaine, décrivant avec plus ou moins de détails comment identifier et mesurer les différents attributs d’évaluation (e.g. sensibilité, représentativité). Les processus d’évaluation proposés et actuellement appliqués présentent cependant certaines limites, telles qu’un manque de flexibilité dans la prise en compte du contexte, et la faible prise en considération des aspects socio-économiques de la surveillance. Pour pallier ces manques, il a été proposé d’utiliser des approches participatives afin de déterminer les perceptions, attentes et besoins des différents acteurs impliqués dans la surveillance. L’objectif de ce travail de recherche était ainsi de déterminer l’apport de l’épidémiologie participative à l’évaluation des systèmes de surveillance en santé animale. Afin de déterminer les attributs d’évaluation pour lesquels la mise en place d’approches participatives peut apporter une valeur ajoutée, un travail de revue et d’analyse critique des méthodes actuellement utilisées pour leur mesure a été réalisé. Ce travail a permis d’identifier trois niveaux d’utilisation possibles de l’épidémiologie participative : (i) la mesure d’un attribut d’évaluation dans son ensemble, (ii) l’appui à la collecte de données nécessaires à l’estimation de l’attribut d’évaluation, et (iii) la collecte d’informations complémentaires permettant d’interpréter les résultats de l’évaluation. Pour ce travail, deux attributs ont été sélectionnés : l’acceptabilité, qui réfère à la volonté des acteurs de participer à la surveillance et pour lequel une méthodologie d’évaluation participative complète a été développée ; les bénéfices non-monétaires, qui réfèrent aux conséquences positives directes et indirectes produites par le système pour les utilisateurs et pour lequel une méthodologie de collecte de données nécessaires à son estimation a été développée. Ces méthodologies ont été appliquées dans deux études de cas : le système de surveillance de la peste porcine africaine en Corse (étude pilote), et le système de surveillance de la tuberculose bovine en Belgique. Ces travaux ont permis de mettre en avant la faisabilité d’utiliser des approches participatives dans des contextes développés, avec des acteurs variés tels que les éleveurs, les services vétérinaires ou encore les agents de laboratoires. Ils ont également permis d’aboutir à une méthodologie participative globale pour mesurer l’acceptabilité : « AccePT » (Acceptability Participatory Toolkit). Concernant les bénéfices non-monétaires, l’utilisation d’une méthode d’estimation contingente associée à un empilement proportionnel a permis d’identifier les informations sanitaires d’intérêt pour les éleveurs, et d’estimer la valeur économique de ces informations pour ces acteurs. Cependant, la méthode développée nécessite encore des ajustements. Faisant suite à ces différents travaux, les bénéfices liés à l’application de l’épidémiologie participative pour l’évaluation des systèmes de surveillance en santé animale ont pu être mis en avant. En effet, celle-ci permet de formuler des recommandations pour l’amélioration de la surveillance basées sur le contexte et prenant en considération les perceptions, attentes et besoins des différents acteurs impliqués. Par une implication directe des acteurs dans le processus d’évaluation au travers des entretiens ouverts, elle permet d’aboutir à une meilleure acceptabilité de celui-ci. Elle offre également l’opportunité de collecter des données complémentaires sur le contexte général dans lequel la surveillance est mise en place, sur le système ainsi que sur des attributs d’évaluation différents des attributs ciblés à l’origine, tels que l’offre de formation et la communication. Cette implication directe des acteurs aide également au renforcement du sentiment d’appartenance des parties prenantes au système de surveillance ciblé, ainsi qu’à une sensibilisation des acteurs vis-à-vis du fonctionnement de ce système et des maladies ciblées. Ces bénéfices sont malgré tout à contrebalancer avec les limites et biais de ces approches, tels que le temps nécessaire à la mise en place et à l’analyse des entretiens et la sélection des participants. L’application de méthodes et d’outils participatifs dans le cadre de la surveillance permet ainsi d’optimiser l’évaluation de ces systèmes. Cependant, leur intérêt dépendra fortement du contexte dans lequel les outils seront appliqués, ainsi que des contraintes liées au processus d’évaluation. [less ▲]

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See detailLaser cooling of iron atoms
Huet, Nicolas ULg

Doctoral thesis (2015)

The work presented in this thesis is dedicated to the development and implementation of a cold atom experiment which handles an atomic species that has not been cooled down so far: iron. The experiment ... [more ▼]

The work presented in this thesis is dedicated to the development and implementation of a cold atom experiment which handles an atomic species that has not been cooled down so far: iron. The experiment requires the use of two UV laser radiations (at 372 and 358 nm) that are frequency stabilized by means of saturation spectroscopy, an iron atomic beam, and a vacuum system, which we contributed to implement and characterize. In addition to this development, several spectroscopic studies were carried out in this thesis. By means of saturation spectroscopy, the hyperfine structure of the molecular-iodine R(90)3-10 transition at 716 nm was first studied following its involvement in the frequency stabilization of the 358-nm radiation. A spectroscopic study of the 358-nm Fe I cooling transition, which was totally unknown prior to this thesis, was also conducted using laser-induced fluorescence spectroscopy. With the same technique, a high accuracy measurement of the iron 358-nm transition frequency with respect to the molecular-iodine R(90)3-10 transition was performed. For this measurement, we implemented a particular configuration which allowed for the minimising of an important systematic error. The first laser cooling of iron is also reported. For this purpose, the Zeeman slowing technique was implemented following a particular two-laser scheme. To our knowledge, this Zeeman slower is the first of this kind. Furthermore, the complete characterization of the cold iron atomic beam produced at the output of the Zeeman slower was done, which allowed for an optimized loading of the magneto-optical trap. Finally, the creation of a cold cloud of iron atoms demonstrated the Zeeman slower ability to properly load an iron magneto-optical trap. [less ▲]

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See detailIndication géographique au Vietnam : Cas du thé vert Tan Cuong, Thai Nguyen
Dang, Thi Minh Luyen ULg

Doctoral thesis (2015)

The Tan Cuong green tea is highly-appreciated since a long time for its quality, according to the Vietnamese consumers. This tea has been recently certified "Geographical Indications (GI)" by the National ... [more ▼]

The Tan Cuong green tea is highly-appreciated since a long time for its quality, according to the Vietnamese consumers. This tea has been recently certified "Geographical Indications (GI)" by the National Office of Intellectual Property of Vietnam. Within the framework of PIC project "Development of the medium and small entrepreneurship in the Vietnam agricultural sector" - financed by the University Commission for Development (CUD), Belgium, Hanoi University of Science and Technology had led a multidisciplinary research on this certified tea product fora better understanding of pros and cons of GI and to identify the constraints of the producers. Pursuing these purposes, three researches related to Tan Cuong green tea were conducted on the commodity, the consumers and the characteristics of products. The commodity research aims to reveal the situation and the problems of tea production in Tan Cuong region. It es based on the survey of 90 households’ producers, combined with in-depth interviews with numerous traders and related suppliers in this area and Hanoi. The second research was a survey which focused on 150 consumers in Hanoi capital, the main market of Tan Cuong green tea to comprehend their perceptions, their opinions and their recommendations for the product. The last study has conducted to contribute to a better knowledge of the product quality. The sensory analysis and bibliographical research on the chemical components of Tan Cuong green tea have been applied to reach this purpose. The result shows that Tan Cuong green tea is a high quality and a high economic profit product. The consumers appreciate the quality of Tan Cuong green tea and expressed an expectation for a healthy and quality tea product. In short, based on the results of various researches, three main recommendations can be drawn: the first one highlights the importance of implementing the GI control system for Tan Cuong green tea, the second one underlines the interest for the Tan Cuong green tea production with an organic label and the third one aims at strengthening the cooperation of all the accors of this sector. [less ▲]

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See detailModelling of cooling and heat treatment of bimetallic rolling mill rolls
Neira Torres, Ingrid ULg

Doctoral thesis (2015)

This work is focused on the modelling of post casting cooling and heat treatment stages, using a coupled thermo-mechanical metallurgical model in order to understand the behavior of bimetallic rolling ... [more ▼]

This work is focused on the modelling of post casting cooling and heat treatment stages, using a coupled thermo-mechanical metallurgical model in order to understand the behavior of bimetallic rolling mill rolls. The case of interest is a bimetallic rolling mill roll which materials and geometry present a risk of failure in industrial manufacturing. The analysis of residual stress fields together with a rough damage approach allows the understanding of the failure event and predicting trends when industrial conditions are modified. Performed finite element modelling requires a complete set of materials parameters. Experimental and numerical methods are applied in order to obtain thermophysical, mechanical, metallurgical and coupled parameters. Sensitivity analysis is performed in order to evaluate the effect of numerical predictions to different input data, modeling eventual modifications of materials or geometries. Finally, conclusions and perspectives obtained from this research allow establishing some weakness of the implemented model, enhancing the importance of considering more advanced damage models. In addition, it is settled that the material characterization must be improved by considering materials pollution and complexity. However the work provides a convincing explanation of the observed phenomena of ruptures. [less ▲]

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See detailSynthesis and characterization of novel donor-acceptor isoindigo-based conjugated copolymers and small molecules and their integration in organic photovoltaics
Tomassetti, Mirco ULg

Doctoral thesis (2015)

The conversion of solar energy into electricity is an environmentally friendly, safe and low- cost way of renewable energy production. Among the different photovoltaic technologies, organic photovoltaics ... [more ▼]

The conversion of solar energy into electricity is an environmentally friendly, safe and low- cost way of renewable energy production. Among the different photovoltaic technologies, organic photovoltaics (OPV) have particular assets in terms of aesthetics, flexibility and low-cost large area coverage. Nevertheless, the moderate OPV efficiencies (˞11%) and lack of durability (< 10 years) strongly limit their large-scale exploitation in particular consumer goods. The main goal of this thesis is to deal with these two drawbacks by designing novel conjugated polymers and small molecules with broad absorption in the visible range (i.e. low band gap), and by setting up strategies to improve the (thermal) stability of the photovoltaic cells. To this extent, novel push-pull type organic semiconducting materials have been synthesized, with different architectures and composed of electron-poor isoindigo building blocks alternating with electron-rich moieties, presenting a favorable spectral overlap with the solar emission. The optical properties of the novel materials were generally investigated by UV-visible absorption spectroscopy, while cyclic voltammetry was implemented to estimate the frontier orbital (HOMO/LUMO) energy levels. Relationships between the chemical nature and architecture of the push-pull systems and their absorption spectra and HOMO-LUMO energy levels have been pursued. Finally, the photovoltaic performances of the new materials have been evaluated in conventional bulk heterojunction organic solar cells using methanofullerene acceptor materials. Correlations between the molecular and photovoltaic parameters have been established. Ultimately, cross-linkable diblock copolymers based on poly(3-hexylthiophene) (P3HT) have been synthesized to improve the long-term stability of P3HT/PC61BM photovoltaic cells. Bulk heterojunction polymer solar cells have been prepared and their stability has been evaluated by accelerated ageing experiments and compared with standard P3HT-based devices. [less ▲]

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See detailHeavy-chain antibody fragments as model proteins to investigate the molecular mechanism of formation of amyloid fibrils
Chavignon, Chloé ULg

Doctoral thesis (2015)

Amyloidoses are rather common and widespread debilitating and/or life-threatening diseases. They display structurally identical amyloid fibrils, and consequently appears to share a common, but still ... [more ▼]

Amyloidoses are rather common and widespread debilitating and/or life-threatening diseases. They display structurally identical amyloid fibrils, and consequently appears to share a common, but still poorly understood, mechanism of fibrillogenesis. Variable domains of camelid heavy-chain antibodies, referred to as VHHs or nanobodies, were chosen to investigate the factors that favour amyloid fibrillogenesis and to get a better understanding of the mechanism of Ig fibrillogenesis. Our study focused on the contribution of protein regions, i.e. the framework (FR) and the complementary determining regions (CDRs) of VHHs, to the formation of amyloid fibrils. Three VHHs were selected: cAb HuL6, cAb BcII10 and cAb BcII10 H H H, a chimera bearing the FR of cAb BcII10 and the CDRs of cAb HuL6. We first established experimental conditions suitable for fibrillogenesis: even the especially stable and soluble VHHs can form amyloid fibrils in denaturing conditions. This comforts the proposal that amyloid conformation is a generic structural form that all proteins can adopt in the appropriate conditions. Amyloid fibrils were characterised by transmission electron microscopy (TEM), circular dichroism (CD), thioflavin T (ThT) fluorescence and X-ray fibre diffraction. The kinetics of fibril formation were monitored by turbidity measurements. We then determined conditions suitable for characterising self-seeding and cross-seeding kinetics, and ascertained that the three VHHs convert into amyloid fibrils according to a nucleation-dependent process. Fibril elongation rates in self-seeding and cross-seeding experiments suggest that amyloid fibril elongation occurs through sequential addition of protein monomers to preformed fibrils. The kinetics of aggregation and self-seeding of cAb-HuL6 and cAb-BcII10 differ significantly, and a remarkable specificity for cross-seeding was observed, with cAb-BcII10 being unable to cross-seed the formation of fibrils by the two other VHHs, while cAb-HuL6 and cAb BcII10 H-H-H mutually cross-seed each other’s fibril formation. With the help of three prediction algorithms (AGGRESCAN, Zyggregator and 3D-profile), we showed that various peptides of the VHHs had the ability to form fibrils by themselves. Our results strongly suggest that the sequences of the regions forming the core of the fibrils essentially correspond to the CDRs. Concurrently, we set up experimental conditions for interrupting the fibril formation process and we characterised the multimer and fibril species formed in the early stages of fibrillogenesis by analytical ultracentrifugation (AUC) and small angle neutron scattering (SANS) ex situ. [less ▲]

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See detailLes carrières des cadres : le genre à l'épreuve des catégories d'âge
Grodent, Françoise ULg

Doctoral thesis (2015)

Le but de notre thèse est de savoir, si en termes de carrières et de conciliation avec la vie privée et/ou familiale des cadres, il existe un effet d'âge qui se superpose à celui du sexe. En effet, il ... [more ▼]

Le but de notre thèse est de savoir, si en termes de carrières et de conciliation avec la vie privée et/ou familiale des cadres, il existe un effet d'âge qui se superpose à celui du sexe. En effet, il existe peu de travaux sur les carrières des cadres qui ont intégré la thématique de l'équilibre entre les sphères privée et professionnelle ainsi qu'une approche intersectionnelle qui conjugue les rapports sociaux de sexe et d’âge. Pour analyser les carrières subjectives des cadres et la conciliation avec leur vie privée et/ou familiale, nous avons opté pour les lunettes d'analyse du genre permettant de dépasser la comparaison hommes-femmes et de tenir compte de l'évolution de la socialisation ainsi que des opportunités historiques des hommes et des femmes dans le travail et dans la famille. En effet, nous ne pouvons pas étudier la carrière des hommes et des femmes sans tenir compte de leur âge et du fait qu'ils ne disposent pas, notamment, des mêmes ressources et des mêmes attributions. Etant donné notre objet d'étude, nous avons opté pour une approche qualitative, exploratoire et inductive. Nos données empiriques ont été récoltées via des entretiens semi-directifs menés auprès de 104 cadres dans une optique de "storytelling". Elles ont été traitées par l'intermédiaire d'une analyse de contenu qualitative thématique et d'une analyse structurale du discours des cadres. Les préoccupations liées à l'évolution historique de la place des hommes et des femmes au travail et dans la famille transforment les relations entre les sexes tant aux niveaux professionnel que familial. L'intersectionnalité des rapports sociaux de sexe et d'âge génère donc des portraits de carrière et de conciliation avec la vie privée et/ou familiale différents pour chacun de nos six sous-groupes de cadres. Les orientations professionnelles et de conciliation ne sont pas uniquement le fruit de décisions ou de contraintes individuelles. En effet, d'autres niveaux d'influence (relationnel, groupal, organisationnel, institutionnel, etc.) interviennent que ce soit au point de vue du travail ou de la famille. [less ▲]

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See detailDesign of a single-species biofilm reactor based on metal structured packing for the production of high added value biomolecules
Zune, Quentin ULg

Doctoral thesis (2015)

Thesis summary In the last decade, numerous single-species biofilm reactors of various configurations have been implemented at lab and pilot scale for the production of chemicals and biological products ... [more ▼]

Thesis summary In the last decade, numerous single-species biofilm reactors of various configurations have been implemented at lab and pilot scale for the production of chemicals and biological products. Compared to their counterparts in submerged cultures, these processes benefit from the specific physiology of biofilms, i.e. high robustness of the microbial system, long-term activity, continuous implementation and low ratio size / productivity. However, the risks of biofouling and the lack of analytical tools for the control and the monitoring of biofilms are obstacles for scale-up strategies. Up to now, single-species biofilm reactors have been mainly confined to the production of metabolites ranging from low (bulk chemicals) to medium (fine chemicals) added values. In this way, there is a need to design efficient single-species biofilm reactors exhibiting good scalability potentials and intended for the production of high added value compounds. In this work, an experimental single-species biofilm reactor has been designed for the production of target molecules derived from metabolic pathways involved in biofilm physiology. On the basis of these criteria, three biological models having good abilities of biofilm formation and secretion performances were selected : - the gram positive bacterium Bacillus subtilis for the production of surfactin, a surface active metabolite involved in biofilm formation. - the filamentous fungus Trichoderma reesei for the production of hydrophobin (HFBII), a surface active protein (7kDa) involved in adhesion process of spores and mycelium on solid surface. - the filamentous fungus Aspergillus oryaze (engineered strain) for the production of a recombinant protein (Gla::GFP) under the control of the glaB promoter specifically activated in solid-state fermentation. The proposed experimental biofilm reactor has the configuration of a trickle-bed bioreactor. The agitation axis of a stirred tank reactor has been removed and replaced by a stainless steel structured packing filling the top of the vessel. The liquid medium, located in the bottom of the vessel is continuously recirculated on the packing element thanks to a peristaltic pump. An ascending air flow is performed above the liquid phase just under the packing element. This thesis reports the screening of the three biological models in the experimental biofilm reactor. The results include the characterization of process performances in terms of biofilm formation and secretion of the target molecule under different operating conditions. An original methodology based on high energy X-ray tomography has been developed to non-invasively visualize and quantify the biofilm colonization inside the packing element. This technique has highlighted that biofilm colonization and liquid phase distribution across the packing are strongly interrelated phenomena. The biofilm of B. subtilis occurring by cell aggregation preferentially developed on solid areas wetted by the liquid. Accordingly, optimal operating conditions improving liquid phase distribution have been defined for biofilm colonization. The fungal biofilm of A. oryzae and T. reesei occuring by cell filamentation equally colonize submerged and aerial surfaces of the packing element. Consequently, another configuration of biofilm reactor comprising a packing element totally immersed in the liquid medium has been investigated. The production yields of surfactin and hydrophobin in the experimental biofilm reactor are respectively 1.25 and 2.64 times greater than those of a submerged culture in a stirred tank reactor. This suggests that surface-active molecules involved in biofilm formation have a real interest for the design of single-species biofilm reactors. Although the Gla::GFP fusion protein is greater produced in the stirred tank culture, its integrity was preserved in the biofilm reactor despite the presence of proteases. This suggests that the quality and the stability of heterologous proteins produced in a fungal biofilm reactor are improved compared with a submerged culture. Finally, the implementation of the biofilm reactor has led to technological progresses including low energy consumption, no foam formation, continuous processing and simplification of downstream process operations. Further experiments should deepen the understanding of structured phenotypic heterogeneity impact on secretion performances in the biofilm reactor. These experiments should consider development of operating conditions allowing for the growth of a thin biofilm homogeneously distributed on the whole surface provided by the packing element in order to optimize nutrients and metabolites mass transfers. The scale-up and the continuous implementation of the process should be also investigated. [less ▲]

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See detailRoot-emitted volatile organic compounds in belowground plant-plant interactions
Delory, Benjamin ULg

Doctoral thesis (2015)

Plants are able to synthesise and release volatile organic compounds (VOCs) aboveground (leaves, stems, flowers and fruits) and belowground (roots). Once emitted, these molecules are key mediators in ... [more ▼]

Plants are able to synthesise and release volatile organic compounds (VOCs) aboveground (leaves, stems, flowers and fruits) and belowground (roots). Once emitted, these molecules are key mediators in biotic interactions as they can be perceived by plant neighbours (first trophic level) and are able to attract/repel organisms of the second (insect herbivores, plant parasitic nematodes) or the third trophic level (entomopathogenic nematodes, parasitoids, etc.). Although many laboratory and field experiments have focused on VOC-mediated plant-plant interactions aboveground, less is known regarding the roles played by root-emitted VOCs in between- and within-plant signalling. In this context, the main goals of this PhD thesis were to (1) identify and quantify the VOCs emitted by barley and chamomile roots and (2) study the influence of chamomile root volatiles on the growth (biomass production and allocation) and the root system architecture (RSA) of barley (interspecific model). Root-emitted VOCs were analysed without extracting the roots from the soil (in situ) using a three-step gas chromatography-mass spectrometry methodology. Plant-plant interaction bioassays were performed using an original experimental device allowing the controlled exposition of growing barley roots to the volatile compounds emitted by chamomile roots for 15 days. In order to speed up the RSA analysis of recipient barley plants, we developed an R package (archiDART) allowing (1) the batch processing of the raw data exported by Data Analysis of Root Tracings (DART) and root image analysis software tools supporting the Root System Markup Language (RSML) format, and (2) the automated computation of RSA traits. Our results showed that crushed barley roots produced mainly hexanal, (E)-hex-2-enal, (E)-non-2-enal and (E,Z)-nona-2,6-dienal. Three-day-old seminal roots were characterised by higher total and individual VOC concentrations compared with older phenological stages. Our experiments also showed that enzymatic activities were required for volatile production. For each developmental stage, the lipoxygenase (LOX) specificity was greater for linoleic acid than for α-linolenic acid. The greatest LOX activities using linoleic and α-linolenic acids as substrates were measured in 7- and 3-day-old roots, respectively. Although undamaged barley roots did not release detectable amounts of VOCs, the analysis of VOCs emitted by mechanically injured roots showed that (E)-non-2-enal (13.8 ± 4.9 ng/g dry wt/h) and (E,Z)-nona-2,6-dienal (4.7 ± 1.8 ng/g dry wt/h) were the only VOCs detected in the plant rhizosphere. Contrasting with these results, the undamaged roots of 61- to 78-day-old chamomile plantlets released mainly one trinorsesquiterpene (albene) and four tricyclic sesquiterpene hydrocarbons (silphinene, modheph-2-ene, α-isocomene and β-isocomene) associated with the Asteraceae family. For each sesquiterpene hydrocarbon, the emission rate was positively correlated with plant age. Based on these results, we performed plant-plant interaction bioassays to investigate the roles played by chamomile root volatiles on the growth and RSA of barley. After 15 days of exposure, plants exposed to the volatiles emitted by the soil and chamomile roots or by the soil alone (control) were morphologically similar. Although not statistically significant (P < 0.09), the leaf area and the total seminal root length were the only parameters that tended to be greater in plants that received the volatile compounds emitted by chamomile roots compared with control plantlets. All these results are discussed in the context of belowground chemical ecology. In addition, some improvements of the experimental devices developed in this research project are also suggested at the end of this PhD thesis. [less ▲]

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See detailIntegrating roots into a whole-plant map of flowering-time gene networks in Arabidopsis thaliana
Bouché, Frédéric ULg

Doctoral thesis (2015)

Flowering is a crucial step in plant development that needs to be carefully regulated to occur at the right time of the year, thus ensuring reproductive success. In Arabidopsis thaliana, several ... [more ▼]

Flowering is a crucial step in plant development that needs to be carefully regulated to occur at the right time of the year, thus ensuring reproductive success. In Arabidopsis thaliana, several interconnected molecular networks have been disclosed that mediate flowering response to environmental cues, such as photoperiod and temperature, or to endogenous factors, such as plant age or hormones. Many of these signalling pathways are systemic, i.e. involve regulatory mechanisms distant from the shoot apical meristem where floral transition eventually occurs. However, most investigations were focused on the aerial parts of the plant but ignored the roots. The aim of this Ph.D. thesis was to integrate the roots into a comprehensive overview of the genetic control of flowering in Arabidopsis. A prerequisite was to obtain a full list of known flowering-time genes. This step led to the creation of a database of flowering-time genes, which is accessible online and in which users can navigate through data tables or interactive schemes (www.flor-id.org). In the second part of the work, we studied the involvement of the roots in the differential developmental rates of plants grown in hydroponics and on soil. In the third part of the work, we used data mining analyses to show that about 200 flowering-time genes are expressed in the roots of Arabidopsis. Using a complementary approach, we analysed the root transcriptome to identify early changes occurring during the induction of flowering by a photoperiodic treatment. Collectively, the results presented in this work brought new insights in the regulation of flowering time at the whole-organism scale by integrating the “hidden part” of plants in the current landscape of the molecular processes controlling phase transitions in Arabidopsis thaliana. [less ▲]

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See detailEulerian Formulation of Spatially Constrained Elastic Rods
Huynen, Alexandre ULg

Doctoral thesis (2015)

Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is ... [more ▼]

Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is in contact with a stiff constraining surface. The research work presented in this doctoral dissertation formulates a computational model for the solution of elastic rods constrained inside or around frictionless tube-like surfaces. The segmentation strategy adopted to cope with this complex class of problems consists in sequencing the global problem into, comparatively simpler, elementary problems either in continuous contact with the constraint or contact-free between their extremities. Within the conventional Lagrangian formulation of elastic rods, this approach is however associated with two major drawbacks. First, the boundary conditions specifying the locations of the rod centerline at both extremities of each elementary problem lead to the establishment of isoperimetric constraints, i.e., integral constraints on the unknown length of the rod. Second, the assessment of the unilateral contact condition requires, in principle, the comparison of two curves parametrized by distinct curvilinear coordinates, viz. the rod centerline and the constraint axis. Both conspire to burden the computations associated with the method. To streamline the solution along the elementary problems and rationalize the assessment of the unilateral contact condition, the rod governing equations are reformulated within the Eulerian framework of the constraint. The methodical exploration of both types of elementary problems leads to specific formulations of the rod governing equations that stress the profound connection between the mechanics of the rod and the geometry of the constraint surface. The proposed Eulerian reformulation, which restates the rod local equilibrium in terms of the curvilinear coordinate associated with the constraint axis, describes the rod deformed configuration by means of either its relative position with respect to the constraint axis (contact-free segments) or its angular position on the constraint surface (continuous contacts.) This formulation circumvents both drawbacks that afflict the conventional Lagrangian approach associated with the segmentation strategy. As the a priori unknown domain, viz. the rod length, is substituted for the known constraint axis, the free boundary problem and the associated isoperimetric constraints are converted into a classical two-point boundary value problem. Additionally, the description of the rod deflection by means of its eccentricity with respect to the constraint axis trivializes the assessment of the unilateral contact condition. Along continuous contacts, this formulation expresses the strain variables, measuring the rod change of shape, in terms of the geometric invariants of the constraint surface, and emphasizes the influence of the constraint local geometry on the reaction pressure. Formalizing the segmentation strategy, a computational model that exploits the Eulerian formulation of the rod governing equations is devised. To solve the quasi-static deflection of elastic rods constrained inside or around a tube-like surface, this computational model identifies the number of contacts, their nature (either discrete or continuous), and the rod configuration at the connections that satisfies the unilateral contact condition and preserves the rod integrity along the sequence of elementary problems. [less ▲]

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See detailLong-term study of methane and two of its derivatives from solar observations recorded at the Jungfraujoch station
Bader, Whitney ULg

Doctoral thesis (2015)

A long-term study of methane and two of its derivatives, i.e. ethane and methanol from ground-based FTIR solar observations recorded at the high alpine International Scientific Station of the Jungfraujoch ... [more ▼]

A long-term study of methane and two of its derivatives, i.e. ethane and methanol from ground-based FTIR solar observations recorded at the high alpine International Scientific Station of the Jungfraujoch (3580 m a.s.l.) is reported. Those three gases act as tropospheric ozone precursors through their removal pathway and therefore have an impact on air quality. In the stratosphere, methane influences the content of ozone and in the production of water vapor. Moreover, both methane and ethane impact the greenhouse radiative forcing. While the latter is an indirect greenhouse gas because of its sinks, the former is the second most important anthropogenic greenhouse gas after CO2. The primary challenge of this work is the development and optimization of retrieval strategies for the three studied gases from FTIR spectra recorded at the Jungfraujoch station, in the framework of the Network for Detection of Atmospheric Composition Change (NDACC), in order to assess their concentrations in the atmosphere and to study their long-term trend and recent changes as well as their seasonal variations. The development and optimization of a retrieval strategy, based on the selection of the best combination of parameters, aims to limit interferences, minimize residuals, and maximize information content. To this end, the best retrieval strategy has been selected from a great number of available combinations thanks to a method for error analysis developed through this work. A 17-year time series of methanol is presented thanks to the combination of spectral windows for the first time for ground-based observations resulting in the improvement of the information content. We therefore present the first long-term time series of methanol total, lower tropospheric and upper tropospheric–lower stratospheric partial columns. We found no significant long-term trend of methanol but its seasonal cycle shows a high peak-to-peak amplitude of ̴103 % for total columns characterized by minimum values in winter and maximum values during summertime. The presented time series provides a valuable tool for model and satellite validation and complement the few NDACC measurements at northern mid-latitudes. Regarding ethane, we have for the first time included a combination of improved spectroscopic parameters as well as an improved a priori state that substantially reduce fitting residuals and enhance information content. Analysis of the long-term trend of ethane covering 20 years of observations revealed a strong positive trend of ethane from 2009 onwards of ̴5 %/year. We hypothesize that this recent ethane upturn may be the result of a large increase in fugitive emissions from the massive exploitation of shale gas and tight oil reservoirs on the North American continent. Finally, we quantified the changes of methane since 2005 from 10 ground-based NDACC sites, with a mean global increase of 0.30 %/year. Investigations into the source(s) responsible for this re-increase are performed with a GEOS-Chem tagged simulation that provides the contribution of each emission source and one sink to the total methane simulated. From the analysis of the GEOS-Chem tracers on both the local and global scales, we determined that the increasing anthropogenic emissions such as coal mining, gas and oil transport and exploitation, have played a major role in the increase of atmospheric methane observed since 2005 while they are secondary contributors to the total methane budget. [less ▲]

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See detailPolyphosphosphoesters for the design of organic and inorganic drug delivery systems
Ergül, Zeynep ULg

Doctoral thesis (2015)

Polymers with repeating phosphoester linkages in the backbone are biodegradable and emerged as a promising class of novel biomaterials, especially in the field of drug delivery systems. The pentavalency ... [more ▼]

Polymers with repeating phosphoester linkages in the backbone are biodegradable and emerged as a promising class of novel biomaterials, especially in the field of drug delivery systems. The pentavalency of the phosphorus atom offers a large diversity of structures and as a consequence a wide range of properties for these materials. The thesis focused on the synthesis of novel well-defined diblock copolymers made of one hydrophilic polyethylene oxide (PEO) block and one polyphosphotriester (PPE) block bearing unsaturations as side-group, as a platform for the design of advanced drug delivery systems. Firstly, novel alkenyl PEO-b-PPE amphiphilic copolymers were self-assembled in water, taking profit of the unsaturations to prepare core cross-linked micelles. Doxorubicin could be successfully loaded by impregnation in these micellar nanocarriers leading to improved stability and loading as compared to the corresponding non-cross-linked systems. Besides, the alkynyl and allyl unsaturations of PEO-b-PPE copolymers were used to prepare novel double hydrophilic block copolymers exhibiting calcium complexation capabilities. They were found quite efficient as template for the formation of calcium carbonate particles providing particles of unprecedented small size, and high size homogeneity. The use of a supercritical carbon dioxide process with carboxylic acid containing copolymers allows reaching CaCO3 particles about 1.5 µm. Finally, we demonstrate that adding lysozyme to the process allows encapsulation of this enzyme into the CaCO3 carriers, the protein activity being better preserved by using the PPE-b-PEO as compared to more conventional hyaluronic acid as a template. [less ▲]

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See detailLes portails occidentaux de la cathédrale d'Amiens
Lekane, Marie ULg

Doctoral thesis (2015)

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See detailMise au point d'un biomatériau à base de chitosan pour le traitement de l'arthrose
Oprenyeszk, Frédéric ULg

Doctoral thesis (2015)

L'arthrose est une pathologie dont la prévalence est élevée avec un retentissement socioéconomique important. À ce jour, les traitements de l’arthrose sont essentiellement symptomatiques. Le remplacement ... [more ▼]

L'arthrose est une pathologie dont la prévalence est élevée avec un retentissement socioéconomique important. À ce jour, les traitements de l’arthrose sont essentiellement symptomatiques. Le remplacement de l'articulation arthrosique par une prothèse est réservé aux formes les plus évoluées de la maladie. Dans ce contexte, il existe un réel besoin de nouveaux traitements bien tolérés et capables de prévenir ou de retarder la progression de la maladie. Dans ce but, nous avons développé des nouveaux biomatériaux sous la forme de billes ou d'hydrogel composés de chitosan d'origine non animale. Dans la première partie de ce travail, nous avons étudié in vitro le comportement des chondrocytes humains, provenant de cartilage arthrosique, incorporés dans des billes de chitosanalginate. Nous avons mesuré la quantité de médiateurs pro-infl ammatoires, cataboliques et anaboliques produite par les chondrocytes. Dans la deuxième partie, nous avons étudié les effets des billes de chitosan-alginate, injectées dans l’articulation, sur la progression de l’arthrose induite chez le lapin par section du ligament croisé antérieur. In vitro, nous avons mis en évidence les effets bénéfi ques et prometteurs des billes de chitosanalginate sur le métabolisme des chondrocytes humains arthrosiques. Dans ces conditions, ils produisaient moins de médiateurs infl ammatoires et cataboliques tout en maintenant la synthèse de composants spécifi ques de la matrice du cartilage. L'étude chez le lapin a montré que l’injection des billes de chitosan-alginate dispersées dans un hydrogel de chitosan prévenait le pincement de l’interligne articulaire - évalué sur une radiographie standard - et réduisait de façon signifi cative la gravité des lésions histologiques du cartilage ainsi que la synovite. En conclusion, la bille de chitosan-alginate est une matrice intéressante pour la thérapie cellulaire des lésions du cartilage et représente une alternative à l’acide hyaluronique pour la viscosupplémentation. [less ▲]

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See detailLa gouvernance environnementale au Sri Lanka. Discours, mise en oeuvre et appropriation locale des politiques de conservation de la nature dans le district d'Hambantota.
Rosillon, Caroline ULg

Doctoral thesis (2015)

L’approche développée dans cette thèse se situe dans le champ de l’anthropologie politique. Elle ambitionne de conjuguer une approche foucaldienne et les outils de la socioanthropologie du développement ... [more ▼]

L’approche développée dans cette thèse se situe dans le champ de l’anthropologie politique. Elle ambitionne de conjuguer une approche foucaldienne et les outils de la socioanthropologie du développement au sein d’une étude des politiques de développement et de conservation de la nature menées dans le district d’Hambantota, au sud du Sri Lanka. La première partie de la thèse se penche, dans une perspective historique et nationale, sur le cadre politique, discursif et idéologique dans lequel prennent place les programmes étatiques de développement. Il y est principalement question de l’émergence et de l’affirmation du nationalisme cinghalais bouddhiste qui s’est constitué au cours de l’histoire de la formation de l’État postcolonial. Le contenu de ce nationalisme repose sur une glorification du passé précolonial du pays et place la communauté paysanne au cœur de la nation. C’est dans ce cadre national que sont élaborés des programmes de développement à destination des populations rurales dont le contenu repose sur l’idée que la modernisation et le développement passent par la réactivation et la valorisation des traditions et du passé. Dans ce nationalisme cinghalais bouddhiste, la nature, dépositaire des traces de l’histoire nationale « légitime », occupe une place de premier plan et les aires protégées constituent des lieux d’expression, de matérialisation et de popularisation de l’idéologie nationaliste. La thèse met en avant la prégnance de cette idéologie dans la société sri lankaise, son caractère hégémonique et le rôle des espaces et de la nature comme supports de cette idéologie. La deuxième partie consiste en une approche ethnographique de deux études de cas illustrant les politiques de conservation mises en œuvre dans le district d’Hambantota. Il s’agit de deux programmes distincts dans leur nature, leur origine, leurs conséquences et la manière dont ils sont appropriés par les acteurs locaux. Le premier cas est un programme de conservation des tortues de mer conduit par une ONG locale dans un village de pêcheurs (Kandura). Le second cas est celui d’une aire protégée de l’État : le parc national de Bundala. La thèse essentielle développée dans cette partie est que les politiques de conservation ou de développement sont toujours influencées par un ensemble de contingences locales qui résultent d’une histoire et de dynamiques contemporaines et qui conditionnent les résultats des politiques implantées. Dans les deux exemples, il existe des formes de détournements, de dérives et de décalages décrits dans cette thèse à travers les processus d’« appropriation » dont font l’objet les deux programmes dans les localités dans lesquelles ils sont implantés. Ces interventions extérieures mettent en jeu un ensemble de rapports de force liés aux arènes locales dans lesquelles elles sont implantées qui sont elles-mêmes structurées en fonction de multiples réseaux de pouvoir et règles d’organisation. L’analyse comparative de ces deux études de cas révèle d’importants contrastes. Elle met en lumière des marges d’appropriation distinctes entre les deux programmes. Dans l’un, l’omniprésence de l’État ainsi que la verticalité du dispositif laisse peu de place aux formes de réappropriation collective ou individuelle tandis que la nature du projet, dans le second cas, permet aux individus des formes d’appropriation multiples et étendues. Ces contrastes sont liés à des types de pouvoir et de sociabilité distincts et témoignent de l’existence de multiples « faces » de la citoyenneté et de multiples registres de subjectivation dans lesquels les individus se construisent quotidiennement en fonction des situations dans lesquelles ils sont projetés. Cette thèse permet en définitive de saisir les processus locaux et tangibles de la gouvernance environnementale et offre une contribution singulière à l’étude des politiques néolibérales de la conservation de la nature. [less ▲]

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See detailBioremédiation du biphényle par Rhodococcus erythropolis T902.1 en présence de nanoparticules métalliques encapsulées dans une matrice de SiO2
Wannoussa, Wissal ULg

Doctoral thesis (2015)

La souche Rhodococcus erythropolis dégrade plusieurs types d’hydrocarbures (aliphatiques, cycliques et aromatiques). Ces derniers, notamment les hydrocarbures aromatiques, présentent des propriétés ... [more ▼]

La souche Rhodococcus erythropolis dégrade plusieurs types d’hydrocarbures (aliphatiques, cycliques et aromatiques). Ces derniers, notamment les hydrocarbures aromatiques, présentent des propriétés physico-chimiques particulières. En effet, ils sont très stables, peu volatils et hydrophobes. Ces propriétés les rendent relativement résistants à la bioremédiation. De ce fait, ils persistent dans l’environnement et causent des effets néfastes, comme les mutations génétiques, les cancers…., sur les êtres vivants. Dans ce travail, le biphényle a été choisi comme modèle en raison de son utilisation, à l’heure actuelle, comme matière de base pour la synthèse de composés polychlorobiphényles (PCB), comme additifs dans certaines formulations de pesticides etc. Cependant, la bioremédiation du biphényle est assez lente, ce qui nécessite encore de nombreuses investigations en vue d’améliorer les performances des microorganismes impliqués. De nombreux travaux mentionnés dans la littérature ont portés sur l’amélioration de la bioremédiation des polluants par l’utilisation d’éléments métalliques tel que le palladium, nickel, cobalt ou le fer à faible concentration. Leur utilisation pose cependant trois problèmes majeurs au niveau (i) de la séparation de ces adjuvants/catalyseurs des produits finaux (e.i. en traitement d’eau); (ii) du recyclage de ces composés et (iii) du pH du milieu réactionnel étant donné son impact majeur sur la solubilité des métaux. Pour limiter ces inconvénients, les catalyseurs métalliques peuvent être dispersés sur un support inerte et poreux de type Al2O3, SiO2, TiO2 offrant une surface spécifique suffisamment importante pour assurer une bonne dispersion des métaux sous forme de particules de taille nanométrique. Dans mes travaux, les nanoparticules métalliques (2 à 3 nm) encapsulées au sein d’une matrice de silice (10 à 20 nm) ont été réalisées. Ces dernières ont été synthétisées par le procédé sol-gel qui assure ainsi la stabilité de la réactivité du catalyseur (absence d’agglomération, relargage contrôlé…..). Les résultats expérimentaux ont montré que, les nanoparticules métalliques encapsulées (le fer, le cobalt et le palladium) activent la bioremédiation du biphényle. En outre, cet impact positif augmente avec la concentration des nanoparticules testées: le pourcentage de bioremédiation passe de 75 ±6.3 % en présence de 10-6M en nanoparticules de fer (Fe/SiO2) à 90 ±3.5 % en présence de 10-4 M après 18 jours d’incubation dans un milieu de culture relativement pauvre (milieu 284) contenant comme seul substrat carboné 500 ppm de biphényle. D’autre part, l’ajout à une concentration de 10-4 M en nanoparticules de fer (Fe/SiO2) ou cobalt (Co/SiO2) a stimulé l’activité des enzymes 1,2-catéchol dioxygénases susceptibles d’être impliquées dans la bioremédiation du biphényle. En outre, la présence de 10-4 M de nanoparticules en fer (Fe/SiO2) pourrait avoir un effet sur la production des biosurfactants notamment des glycolipides contenant du tréhalose. Ces derniers pourraient favoriser la solubilisation des hydrocarbures ou leur adhésion à la surface de la Rhodococcus erythropolis T902.1. En effet, la présence d’une concentration de 10 -4 Ce travail se termine par une discussion générale mettant en évidence les avantages d’utilisation des nanoparticules et une comparaison avec les études récemment publiées dans la littérature scientifique. Des perspectives de recherches sont soulevées afin de permettre une extrapolation de la bioremédiation d’autres polluants avec d’autres souches bactériennes en présence des nanoparticules. M des nanoparticules en fer (Fe/SiO2) induit une augmentation de 85 % en tréhalose. [less ▲]

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See detailUsing remote sensing (optical and radar) and modeling to support the irrigation management of cereals in a semi-arid region: a case study of the Tadla irrigated perimeter in Morocco
Benabdelouahab, Tarik ULg

Doctoral thesis (2015)

Summary Irrigated agriculture is an important strategic sector in Morocco, it accounts for about 45%, on average, of the agricultural Gross Domestic Product, contributing thus to food security and ... [more ▼]

Summary Irrigated agriculture is an important strategic sector in Morocco, it accounts for about 45%, on average, of the agricultural Gross Domestic Product, contributing thus to food security and employment. It occupies 15% (about 1.5 million ha) of the total cultivated area in the country. Irrigation scheme managers need to ensure that water is optimally used in the irrigated perimeters and that water shortages are avoided. For large areas under irrigation, this can be achieved through water monitoring at plot level using modeling and satellite-based methodologies. The main objective of this research was to assess the use of optical and radar remote sensing and of crop modeling in the irrigation monitoring and management of wheat in the irrigated perimeter of Tadla. The potential of spectral indices derived from SPOT-5 images was explored for comparing, quantifying and mapping surface water content changes at regional and local levels. Indices were computed using the reflectance in red, near infrared and shortwave infrared bands. Our findings show that the normalized difference water index (NDWIRog) could be used to estimate and map the surface water content of wheat plots, from bare soil to fully covered soil. Backscatter threshold values derived from SAR images were used to detect irrigation water supplies in wheat plots and the optimal acquisition frequency of SAR images was determined in order to ensure continuous monitoring. A field crop model (AquaCrop) was adjusted to simulate durum wheat yields and the temporal evolution of soil moisture status in order to manage and schedule irrigation water supplies and assess their impact on yield. Currently, the approaches described in this paper are being applied independently. This research was intended, therefore, to provide tools to help policy-makers and stakeholders improve irrigation monitoring and mitigate wheat water stress at the field and irrigation perimeter levels in semi-arid areas. Keywords: irrigation management, spectral index, wheat, backscattering, SAR, semi-arid, Morocco. [less ▲]

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See detailHydro-mechanical analysis of the fracturing induced by the excavation of nuclear waste repository galleries using shear banding
Pardoen, Benoît ULg

Doctoral thesis (2015)

The long-term management of high-level nuclear wastes is envisaged by deep geological repository. Due to the safety function of the host formation, the behaviour of the Excavation Damaged Zone (EDZ) that ... [more ▼]

The long-term management of high-level nuclear wastes is envisaged by deep geological repository. Due to the safety function of the host formation, the behaviour of the Excavation Damaged Zone (EDZ) that develops around underground galleries during their drilling is of paramount importance. The EDZ is dominated by fracturing process which engenders irreversible modifications of the hydro-mechanical properties of the porous rock. In this zone, a significant hydraulic permeability increase of several orders of magnitude is observed. It may alter the safety function of the host formation by creating preferential flow paths for the migration of radionuclides towards the biosphere. Consequently, the understanding and the prediction of the EDZ hydro-mechanical behaviour are crucial issues for the long-term management of nuclear wastes. Among the different low-permeability media that are envisaged for the deep repository, the Callovo-Oxfordian claystone is studied. The fracturing behaviour, the water transfers, and the coupled processes that occur around the underground galleries are most particularly addressed, especially in the EDZ. The fractures induced by the excavation process are reproduced with strain localisation in shear bands. An appropriate model allowing to properly reproduce the strain localisation in geomaterials with finite element methods is used. It is an enhanced model for microstructure media called the coupled local second gradient model and which involves a regularisation method. Its application is extended to unsaturated anisotropic rocks with compressible solid grains. The numerical modelling of the fractured zone with shear banding provides information about its shape, extent, fracturing structure, and behaviour that are in good agreement with in situ measurements. In particular, the shape of the EDZ in the Callovo-Oxfordian claystone is governed by its anisotropy and the gallery convergence strongly depends on the appearance of the shear bands. The fluid transfers and the coupled processes are investigated in the EDZ. The impact of the rock fracturing on its hydraulic properties is addressed by taking into account strain localisation effects at macroscale. The evolution of the intrinsic water permeability is expressed by a strain-dependent relation which engenders a more pronounced increase of the permeability inside the shear bands. In agreement with experimental measurements, an important increase is reproduced in the excavation damaged zone. After gallery excavation, the hydraulic transfers in the rock surrounding the galleries are investigated by considering the interaction between the rock and the gallery air. These transfers are studied at large-scale during the reproduction of gallery air ventilation. Depending on the air hygrometry, the gallery ventilation implies drainage and desaturation of the surrounding rock which affect the shear banding development. The hydraulic transfers in the rock which depend on the water exchanges at gallery wall are also studied. The proposed approach aims to highlight the important hydro-mechanical aspects to take into account for the reproduction of the EDZ behaviour in unsaturated biphasic media with shear banding. The focus is resolutely on the large-scale numerical modelling of the EDZ as well as on the reproduction of the mechanical and hydraulic experimental measurements performed around galleries. [less ▲]

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See detailRôle du gorille des plaines de l’Ouest (Gorilla gorilla gorilla) dans la régénération des forêts denses humides et interaction avec l’exploitation sélective de bois d’oeuvre
Haurez, Barbara ULg

Doctoral thesis (2015)

According to the IUCN, the western lowland gorilla (Gorilla gorilla gorilla Savage & Wyman) is a critically endangered species. This species would play an important role in tropical forest dynamics ... [more ▼]

According to the IUCN, the western lowland gorilla (Gorilla gorilla gorilla Savage & Wyman) is a critically endangered species. This species would play an important role in tropical forest dynamics. Indeed, its highly frugivorous diet and its large body mass would result in the implication of gorilla in the seed dispersal of many plant species. Moreover, by building its nest sites in open canopy forest, it would deposit the majority of seeds in habitats displaying potentially suitable light condition for their germination and for the subsequent seedling development. However, given the expansion of timber exploitation in Central Africa, ecological services dispensed by gorilla could be threatened. The objective of this thesis is to characterize the impacts of timber exploitation on gorilla populations and the role of these populations in forest regeneration after logging. The results demonstrate that a viable population of gorilla may be maintained in selectively logged forests (< 2 trees ha-1). Indeed, although gorillas tend to flee areas during timber exploitation activities, their density in logged forest reaches its initial value, or even a higher level, within one year after the end of logging. The preferential selection of open canopy forest areas for nesting was verified, before and after logging. The deposition of seeds in habitats providing favorable light conditions is therefore confirmed, even though the preference for tree fall gaps and forest skid trails was not observed in the course of the monitoring period (one year after logging). The seeds of 59 plant species were found in gorilla feces collected over a period of 20 months. A quarter of these species presented an economically value because of their use as timber or non-timber forest products. The analyzed fecal units contained between one and six different seed species, and on average 81.0 ± 107.8 intact seeds (0-566). Depending on the species considered, germination success varied from 0 to 100 %, with an average of 46 ± 36 %. The gorilla is the main disperser of a timber species, Dacryodes normandii. Over the fructification period, the gorilla consumed fruits of this species in 87.8 % of its visits (of an average length of 85 ± 89 min.). The impact of gut passage was evaluated for two tree species, Santiria trimera and Chrysophyllum lacourtianum. These species displayed higher germination successes after gorilla ingestion because of both pulp suppression and seed coat scarification. In addition, a positive effect of fecal matrix on seedling development was observed for three studied species, S. trimera, C. lacourtianum and Plagiostyles africana. Finally, the development of seedlings is favored in nesting sites, the most frequent seed deposition sites. Two studied species, S. trimera and Dacryodes normandii displayed a growth between two and ten times faster in nest sites than in closed canopy forest. Therefore, gorilla is implicated in directed seed dispersal. Consequently, when poaching is absent, western lowland gorilla populations seem to be resilient to selective logging and they play a critical role in the seed dispersal process, both quantitatively and qualitatively, in logged forests. Some recommendations to improve the management of logged forest that host gorilla populations were proposed in order to favor their preservation within logging concessions. In particular, the generalization of reduced impact logging practices is advisable. [less ▲]

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See detailIdentification of the bacterial symbionts of the banana aphid Pentalonia nigronervosa and characterization of their roles
De Clerck, Caroline ULg

Doctoral thesis (2015)

Les insectes sont caractérisés par une incroyable capacité d’adaptation à de nombreux environnements et modes d’alimentation, qui est liée au fait que la majorité des insectes (voire tous) hébergent des ... [more ▼]

Les insectes sont caractérisés par une incroyable capacité d’adaptation à de nombreux environnements et modes d’alimentation, qui est liée au fait que la majorité des insectes (voire tous) hébergent des symbiontes intra ou extracellulaires. Ces associations symbiotiques sont très diverses et peuvent aller d’un mutualisme obligatoire à un parasitisme facultatif. Les pucerons, en particulier, sont connus pour vivre en symbiose avec au moins une bactérie obligatoire qui leur fournit les nutriments essentiels absents du phloème dont ils se nourrissent : Buchnera aphidicola. La plupart des symbiontes d’insectes étant incultivables, les technologies moléculaires modernes se sont avérées des outils puissants dans la compréhension des interactions hôte-microorganisme et la caractérisation du rôle joués par ces symbiontes. Les études génomiques ont mené à la découverte des plus petits génomes bactériens jamais observés, et ont permis une étude plus poussée des symbiontes secondaires et de leur évolution. Pentalonia nigronervosa, le puceron noir du bananier, lest le vecteur principal du virus des sommets touffus du bananier, l’un des virus les plus dommageables en culture bananière. Très peu d’études sont néanmoins disponibles sur ce vecteur et rien n’était connu sur la population symbiotique hébergée par cet insecte jusqu’à cette étude. Dans cette thèse, nous avons découvert que le puceron du bananier contient deux symbiontes : B. aphidicola (BPn) et Wolbachia sp. (wPn); et cela dans tous les pucerons testés, quelle que soit leur origine géographique. La présence de Buchnera était attendue (99,9% de toutes les espèces de pucerons contiennent ce symbionte), mais la détection systématique de Wolbachia nous fait nous interroger sur le rôle que cette bactérie pourrait jouer pour l’insecte hôte, ainsi que sur la raison de sa présence. Wolbachia n’est en effet que rarement détectée chez les pucerons et est surtout connue pour être un parasite qui manipule le système reproducteur de ces hôtes. Malgré tout, des études ont montré que cette bactérie pouvait agir comme mutualiste pour certains insectes, ce qui pourrait expliquer sa présence dans le puceron du bananier. Le second objectif de cette étude a donc été de mieux comprendre le rôle joué par les deux symbiontes de P. nigronervosa. Pour ce faire, différentes techniques complémentaires ont été utilisées. La microinjection d’antibiotiques a été utilisée afin d’éliminer sélectivement wPn et de voir l’effet de cette élimination sur l’hôte. Nous avons observé que l’élimination de wPn donnait systématiquement lieu à la mort du puceron. Un séquençage haut débit de l’hémolymphe (contenant des bacteriocytes) d’un puceron a été réalisé et nous a permis d’identifier et d’annoter 587 et 250 gènes pour wPn et BPn respectivement. L’analyse de ces gènes nous permet d’émettre l’hypothèse que les deux bactéries collaborent pour la production de plusieurs nutriments essentiels pour l’hôte. La situation est surtout frappante dans le cas de la lysine et de la riboflavine, qui sont habituellement produits uniquement par Buchnera chez les autres espèces de pucerons. Dans le cas du puceron du bananier, les gènes impliqués dans les voies de production de ces métabolites sont répartis entre les génomes des deux bactéries, les rendant ainsi toutes les deux essentielles à la survie du puceron hôte. Enfin, une localisation par fluorescence in situ des deux symbiontes a montré qu’ils étaient tous deux localisés dans les bacteriocytes, rendant les échanges de précurseurs et métabolites possibles. En conclusion, nos résultats suggèrent que le puceron du bananier héberge une co-symbiose obligatoire entre B. aphidicola et Wolbachia, les deux bactéries agissant de concert dans l’approvisionnement de l’hôte en nutriments essentiels. [less ▲]

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See detailHistoire Evolutive de Rongeurs Holarctiques: Approche micro- & macroévolutive
Pisano, Julie ULg

Doctoral thesis (2015)

La biodiversité n’est pas stable dans le temps et l’espace. Elle évolue en réponse à différents facteurs. A l’échelle macroévolutive, les moteurs de diversité sont essentiellement les changements ... [more ▼]

La biodiversité n’est pas stable dans le temps et l’espace. Elle évolue en réponse à différents facteurs. A l’échelle macroévolutive, les moteurs de diversité sont essentiellement les changements tectoniques majeurs, climatiques globaux et environnementaux. Ils sont connus pour avoir façonné les patrons évolutifs de groupes d’espèces sur de grandes échelles spatiales et temporelles. A l’échelle microévolutive, les moteurs de diversité sont majoritairement liés à des forces évolutives telles que la mutation, la dérive génétique, la sélection ou la dispersion. Ils rythment l’évolution de la biodiversité populationnelle à une plus petite échelle spatiale et temporelle. Dans le cadre de cette thèse, le but a été de construire un cadre évolutif stable permettant de nous éclairer sur les processus évolutifs et/ou les facteurs qui ont rythmé l’histoire évolutive d’espèces et de populations de rongeurs. Pour étudier l’évolution de la biodiversité à l’échelle macroévolutive, nous avons pris comme modèle biologique la superfamille des Dipodoidea (Rongeurs : Myodonta). Groupe frère des Muroidea, la superfamille des Dipodoidea comprend trois grands groupes d’organismes : les sicistes (Sicistinae), les souris-sauteuses (Zapodinae) et les gerboises (Allactaginae, Cardiocraniinae, Dipodinae et Euchoreutinae). Dans la littérature, la superfamille des Dipodoidea comprend 51 espèces réparties dans 16 genres de six sousfamilles, toutes de la famille des Dipodidae mais cette classification basée essentiellement sur des données morphologiques est très controversée. Avant cette thèse, aucune phylogénie moléculaire des Dipodoidea n’avait été reconstruite. De plus, les Dipodoidea sont particulièrement intéressants pour tester divers scénarios biogéographiques étant donné certaines distributions disjointes dans l’Holarctique et les nombreuses espèces réparties dans les déserts d’Asie et d’Afrique. Il est donc intéressant de comprendre comment ces patrons de distribution disjoints sur l’Holarctique (e.g. Afrique du Nord, Amérique du Nord) ont été mis en place et ‘quand et où’ ces différents groupes sont apparus. Lors de cette thèse, pour la première fois, une phylogénie moléculaire comprenant 20 des 51 espèces de Dipodoidea a été reconstruite à partir de quatre gènes nucléaires (BRCA1, GHR, IRBP, RAG1). Cette phylogénie moléculaire a ensuite été comparée à une phylogénie morphologique reconstruite sur base des caractères de la dentition, de la bulle auditive, du gland du pénis et des glandes reproductives accessoires. Cela a permis de comprendre que les nombreuses controverses autour de la taxonomie et de la systématique des Dipodoidea étaient dues à des homologies qui brouillaient le signal phylogénétique. Ainsi, une nouvelle taxonomie des Dipodoidea a pu être proposée. La superfamille des Dipodoidea est dorénavant constituée de 3 familles (Sminthidae, Zapodidae, Dipodidae) et de 19 genres. Ensuite, pour étudier l’histoire évolutive biogéographique de la superfamille des Dipodoidea, l’échantillonnage taxonomique a été augmenté. La phylogénie moléculaire la plus complète à ce jour incluant 34 espèces de Dipodoidea a pu ainsi être reconstruite sur base du gène mitochondrial du cytochrome b et des mêmes gènes nucléaires utilisés précédemment. Lors de cette seconde étude, nous avons pu montrer que la radiation des Dipodoidea modernes a L eu lieu au Paléocène supérieur dans la région d’Asie Centrale et de l’Himalaya-Plateau Tibétain et que, de façon générale, leur histoire évolutive a été rythmée par les grands bouleversements climatiques et environnementaux engendrés par la surrection de l’Himalaya et du Plateau Tibétain. Pour étudier l’évolution de la biodiversité à l’échelle microévolutive, nous avons pris comme modèle biologique le campagnol roussâtre (Myodes glareolus). Les populations de campagnol roussâtre sont réparties en plusieurs lignées mitochondriales distribuées sur une large zone de la région Paléarctique. L’une d’elles, caractérisée par le génome mitochondrial du campagnol de la Taïga (Myodes rutilus), se distribue de la moitié supérieure de la Suède à travers la Finlande jusqu’au centre de la Russie. En Finlande, cette lignée introgressée (mitotype RUT) vient au contact d’une autre lignée du campagnol roussâtre (mitotype GLA). Il a été proposé que cette zone de contact en Finlande soit le résultat d’un contact secondaire. Cependant, étant donné qu’aucune différenciation nucléaire n’a été observée entre les mitotypes GLA et RUT, il n’est pas clair si cette zone de contact résulte bien d’un contact secondaire (deux évènements de recolonisation de la Finlande). Une autre hypothèse suggérant un seul événement de recolonisation de la Finlande pourrait également expliquer ce patron de discordance mito-nucléaire. Lors de cette thèse, nous avons étudié la zone de contact entre les mitotypes GLA et RUT située au centre de Finlande sur base de 17 marqueurs microsatellites et du cytochrome b. Notre but était d’estimer si la Finlande a connu un ou deux évènements de recolonisation postglaciaire et donc, de mieux comprendre si la zone de contact résulte ou non d’un contact secondaire entre les deux mitotypes. Les approches classiques de génétique des populations et de « clustering » ne nous ont pas permis de valider l’une ou l’autre des hypothèses du fait que la dispersion était limitée dans l’espace et que la différenciation génétique nucléaire entre les campagnols de Finlande était faible. Par conséquent, pour valider définitivement une des deux hypothèses, nous avons dû utiliser des analyses de clines de fréquences alléliques de marqueurs neutres. Celle-ci a montré que le cytb et 16 des 17 microsatellites présentaient des changements de fréquences alléliques entre les mitotypes GLA et RUT et que, par conséquent, la zone de contact entre les mitotypes GLA et RUT correspondait bien à une zone de contact secondaire résultant de deux évènements de recolonisation indépendants. En conclusion, cette thèse m’a permis de mieux comprendre comment la biodiversité évolue en réponse à différents facteurs. Etudier la biodiversité en utilisant des approches macroévolutives et microévolutives est très intéressant car cela permet d’avoir un regard large sur la manière avec laquelle les espèces, les populations et leurs génomes évoluent. [less ▲]

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See detailAssessment of Non-Lethal Projectile Head Impacts
Oukara, Amar ULg

Doctoral thesis (2015)

Anti-personnel Non-Lethal Weapons (NLW) are used to impart sufficient effect onto a person in order to deter uncivil, suspect or hazardous behaviour with a low prob- ability of permanent or fatal injury ... [more ▼]

Anti-personnel Non-Lethal Weapons (NLW) are used to impart sufficient effect onto a person in order to deter uncivil, suspect or hazardous behaviour with a low prob- ability of permanent or fatal injury. They appear to be suitable for many law enforcement missions and to a certain extent to the military forces. In fact, in many situations of conflict, where the army and civil police are involved, the use of such weapons can ensure a minimal risk of collateral damage. The most used NLW are Kinetic Energy Non-Lethal Weapons (KENLW) that involve the shooting of a de- formable or breakable projectile with masses between 5 g to 140 g at initial velocities between 70 m/s and 160 m/s. Practically, KENLW are not used without risk for the targeted persons. The head zone represents the most critical part of the human body regarding non-lethal projectile impacts. The inflicted injuries can be severe and sometimes lead to death. The experts in the field should identify the limits in which KENLW should be effective without causing permanent or fatal injuries. Therefore, assessment methods should be developed in order to predict the injury risk of non-lethal head impacts. The present thesis proposes the development of three different approaches allowing the assessment of the non-lethal head impacts. The first approach named FW (Force wall) method has been developed at DGA (Direction Générale de l’Armement) - France. For a benchmark projectile, this method links the maximum impact head force to the maximum impact force mea- sured on a supposedly infinitely rigid structure, equipped with a piezoelectric force sensor. Three lesional thresholds: unconsciousness, meningeal damage and bone damage with coma are used. The FW method proposes the extension of the bench- mark projectile results to other projectiles using the assumption: two different pro- jectiles producing the same force on a rigid structure, will have the same effects on the head. This method is applied in the present thesis for different projectiles using a specific experimental setup. Different improvements have been achieved regarding the frequency analysis of the rigid structure and the quantification of uncertainties of the FW method. These improvements represent some original contributions of the present thesis.The second approach concerns the use of a mechanical surrogate in order to predict the maximum impact head force. The mechanical surrogate involved in the present study is BLSH (Ballistics Load Sensing Headform). Different tests have been performed using no less than eight commercial projectiles. The third approach uses numerical simulations with a validated FEHM (Fi- nite Element Head Model). SUFEHM (Strasbourg University Finite Element Head Model) is considered in the present thesis. The model offers the possibility to pre- dict head injuries using other parameters than the maximum impact head force: the strain energy and the Von Mises stress. A specific method is proposed in order to develop the FE (Finite Element) models of non-lethal projectiles. Six FE models of projectiles are used for the numerical simulations. Results show a good agreement between the three methods for the benchmark projectile. The extension of the FW method for other projectiles can be performed with some limitations mentioned in the present document. Moreover, there is a good agreement between BLSH and SUFEHM for all studied projectiles. Different correlations between the maximum impact head force and other criteria are also proposed in order to include them in the non-lethal head impact injury prediction. Ultimately, the present work proposes assessment methods for non-lethal projec- tile head impacts. The different details of these methods are given in the present document. [less ▲]

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See detailStudy of the Direct Borohydride Fuel Cell anode
Olu, Pierre-Yves ULg

Doctoral thesis (2015)

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See detailMort Cellulaire et Développement chez Streptomyces coelicolor
Tenconi, Elodie ULg

Doctoral thesis (2015)

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See detailOptimalisation de la production d’énergie par des procédés biochimiques à partir de substrat d’origine tropicale : Application à la biomasse lignocellulosique du bananier représentée par le cultivar Williams Cavendish (Groupe Triploïde Musa AAA)
Kamdem, Irenée ULg

Doctoral thesis (2015)

In a context where the need to find sustainable alternatives to fossil energies are necessary, this thesis highlights the socio-economic, environmental and energy benefits that banana-producing countries ... [more ▼]

In a context where the need to find sustainable alternatives to fossil energies are necessary, this thesis highlights the socio-economic, environmental and energy benefits that banana-producing countries can draw from the energy conversion of the residual lignocellulosic biomass (BLC) of banana plant. It also highlights the molecular and elemental factors influencing the production of methane (CH4) through the anaerobic digestion (AD) of the banana lignocellulosic biomass (BLB). The experiments carried out for the thesis showed that this substrate of tropical origin requires pretreatment to improve its digestibility and to optimize the production of CH4. A developing country like Cameroon, that produces and exports dessert and cooking bananas, generates annually approximately 4.5 million tons of fresh untapped BLB. The potential biotransformation of this waste into bioethanol, biomethane and pellets, constitutes new opportunities that could provide an important source of income for both banana producers and the whole country. These benefits are related to theoretical studies which required experimental studies for its validation. By its chemical composition, BLB is energetically more adapted to the biochemical processes of transformation, and particularly to AD. Therefore AD was investigated on BLC of Williams Cavendish cultivar (WCLB), one of the most commercialized in Cameroon. The analysis of the cumulative production of biogas from each of the six morphological parts (MPs) that constitute this biomass (bulb, leaf sheaths, petioles–midribs, leaf blades, rachis stem, and floral stalk) showed that the leaf blades and the rachis stem achieved respectively the lowest and the highest production yields i.e. 98 and 162 mL CH4 g-1 dry matter (DM of MP). The biogas conversion efficiency of all the combined six MPs was 50% lower than the theoretical potential (based on the total carbon content).These results therefore justified the need to deconstruct this organic matter through pretreatment operation since the lignin appears as one of the main factors limiting the accession of enzymes to the fermentable substrates. Biochemical composition of the BLC from all the combined six MPs of WCLB were compared before and after two different physicochemical pretreatments selected for their socio-economical and techno-ecological advantages i.e. steam cracking (SC) and steam explosion (SE). These pretreatments were carried out at pilot-scale with different severity factors namely regarding temperature since SC was tested at 150 °C (SC150), 180 °C (SC180) and 210 °C (SC210), and SE was tested at 210 °C. The results suggest that SC180 and SC210 are the most lignin-destabilizing pretreatments. The enzymatic degradation of the solid fractions (SFs) and the liquid fractions (LFs) recovered after the pretreatments confirmed the presence of oligomers in the LFs and the improvement of the digestibility of SFs. This digestibility improvement was confirmed by a supplementary AD. Indeed the weighted cumulative production of methane from SF and LF during 135 days shows that the SC210 and SE improved the production of biomethane by 28% and 5% respectively. A simplified schematic model of mass distribution during AD of a complex fermentable organic matter such as WCLB was proposed. Along with the existing models, this schematic model will contribute to the predictive evolution of the initial biomass, the bacterial and archaebacterial biomass, the soluble organic metabolites (such as acetic acid), and the CH4 and CO2 biogas. Forecasts related to the installation and operation of a family sized anaerobic digester in Cameroon have a return on investment period of about 8.5 years (with an estimated life term of 25 years for the biodigester built in reinforced concrete). Moreover, the simulation of an integrated industrial production of biogas and bioethanol from 1 ton DM of WCLB subjected to SC210 showed that 284 L of ethanol would be produced from 800 kg DM of SF for a production cost of 85 €. This cost was calculated regardless of energy from the combustion of biogas produced during the AD of 200 kg DM of LF. Net income after tax for the integrated production was valued to 239 € t-1 DM WCLB. This study showed that BLB should now be taken into account within the energy recoverable BLC and that it is more adapted to the AD process. However, a better assessment of the energetic, socio-economical and environmental benefits that banana-producing countries can draw from the BLB, would require a pilot-scale investigation of the AD process where the bio-physico-chemical parameters prevailing in the industrial biodigesters can be reproduced. [less ▲]

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See detailFrom some obscurity to clarity in Boom clay behavior: Analysis of its coupled hydro-mechanical response in the presence of strain localization
Salehnia, Fatemeh ULg

Doctoral thesis (2015)

Deep disposal of the high-level and high-lived radioactive wastes in the potential geological formations is envisaged as a possible solution in the framework of long-term management of these wastes. The ... [more ▼]

Deep disposal of the high-level and high-lived radioactive wastes in the potential geological formations is envisaged as a possible solution in the framework of long-term management of these wastes. The argillaceous materials, namely Boom Clay, are potential to constitute the natural barrier aimed at confining the nuclear waste and protecting the biosphere from it. Around galleries excavated at depth in these media, the creation of a damaged zone with significant irreversible deformation is generally unavoidable. A considerable change in the host rock properties could be likely resulted in this zone, which may potentially be important with respect to the long-term evolution and the performance of the system. In this context, a paramount interest addresses characterization of the so-called Excavation Damaged Zone (EDZ), predicting its extent, and development of localized fracturing during and after the underground excavation in the host rock. This constitutes the foundation of this work, focusing on the Boom Clay formation as the reference potential host rock in Belgium. Dealing with this purpose, providing a state of knowledge on the hydro-mechanical behavior of Boom Clay, and validating a set of parameters which could realistically reproduce its response through the numerical modelings are firstly addressed as the requisites. Moreover, a special focus is made on the dilatation factor of the rock, commonly described through the dilatancy angle parameter. Correct estimation of the dilatant behavior of a rock has an essential role in a realistic simulation of its volumetric behavior, fracturing threshold during the rock deformation process and its post-failure response. Therefore, a new formula is developed for consideration of the variable dilatancy angle, incorporated into an internal frictional elasto-plastic hardening/softening model, within the LAGAMINE finite element code. This development overcomes the inconveniences associated to using a constant dilatancy angle, for instance encountered in our numerical simulations of some laboratory small-scale tests as well as a large-scale excavation. This study then focuses more particularly on simulation of EDZ extension at the large scale excavation, around the Connecting gallery (in the HADES URL, Mol, Belgium), through analyzing the evolution of strain localization in shear bands mode. The modeling takes into account of the initial anisotropic stresses, mechanical cross-anisotropy, anisotropic permeabilities, and gravity effects. As a result, an eye-shape extension of EDZ accompanied by an anisotropic convergence of the rock is predicted. A coupled analysis addresses the pore water pressure distribution during the excavation period and in long-term while no more evolution of the localized shear bands is predicted. To assess the reliability of the numerical results, some available in-situ measurements and observations, within the clay, during the gallery's construction and afterwards are precisely analyzed, and then compared with the corresponding numerical predictions. As a result, a good agreement is found between the in-situ data and simulated results. Moreover, the above study is integrated with a particular analysis of the contact mechanism on the interface between the clay and the gallery's lining. Thence, the coupled interface element is introduced to deal with the contact phenomenon. The obtained results reveal some interesting features regarding the development of contact pressure on the interface linked to the evolution pattern of strain localization within the clay around the gallery. Furthermore, with regard to the own lining behavior, a development of the modeling with the aim of consideration of a discontinuous lining (made of the segments as the real case) is performed. We propose an approach to realistically reproduce the response of the lining's segments and their contact phenomena in the course of a long-term simulation. Defining the interface elements between the neighboring segments, with respect to the real installation procedure of the lining during the gallery construction, this process is aimed to be simulated through some evolution of the contact pressure on the segments' interfaces. As a result, a considerable improvement is achieved in reproducing the in-situ measurements provided in the lining. The numerical and measured evolution of strain and displacement are in a good agreement. [less ▲]

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See detailAspects malacologiques du cycle de Fasciola hepatica en Belgique et en Equateur
Caron, Yannick ULg

Doctoral thesis (2015)

Fasciolosis is a zoonotic disease of ruminants and other herbivorous due to two parasite species of the genus Fasciola. If Fasciola gigantica is a tropical species, F. hepatica has a much wider geographic ... [more ▼]

Fasciolosis is a zoonotic disease of ruminants and other herbivorous due to two parasite species of the genus Fasciola. If Fasciola gigantica is a tropical species, F. hepatica has a much wider geographic distribution. Fasciola hepatica is responsible for important economic losses such as a marked reduction of milk yield and liver condemnation at the slaughterhouse. The life cycle of this platyhelminth involves an intermediate host, a gastropod mollusc belonging to the Lymnaeidae family. In temperate Europe, Galba truncatula acts as the main intermediate host of F. hepatica. A wide network project called MANSCAPE allowed the implementation of a sampling campaign conducted in more than 125 ponds throughout Belgium which revealed that other lymnaeid snails (belonging to the genus Radix) could act as secondary or alternative intermediate hosts. Some experimental infections of snails and rats permited to study the host-parasite relationships in some of these species (Radix balthica, R. labiata). Sibling species very similar to « R. peregra » seem to contain several potential candidates. Several techniques are available to detect the parasite in the snail: they are based either on microscopy or on molecular biology. A very sensitive (100 pg parasite DNA still detectable) and specific technique based on molecular biology (Multiplex PCR) was developed. This technique was used qualitatively and quantitatively to determine the intermediate host species involved in the life cycle of the liver fluke in Belgium. This study was performed in the frame of the PONDSCAPE project and prevalences of 1.31% (30/2747) and 0.16% (7/4629) were recorded for G. truncatula and R. balthica respectively. This technique was then used in Ecuador to bring some information on the intermediate host species involved in the life cycle of F. hepatica. Galba schirazensis, an invasive species in South America, was identified as a lymnaeid that could harbour a part of the life cycle of the parasite as 8.15% (86/1055) of the collected snail contained parasite DNA and 2.46% (26/1055) living larvae. These studies showed that R. balthica could have an impact on the epidemiology of F. hepatica in Belgium and that the role of G. schirazensis in Ecuador needs to be clarified. This will be discussed in this work and specially in term of co-evoultion and adpatation way. [less ▲]

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See detailEFFECTS OF AGRICULTURAL PRACTICES AND HEAVY METAL CONTAMINATION ON THE COMMUNITY DYNAMICS OF EARTHWORMS IN RELATION TO SOIL PHYSICAL AND CHEMICAL FACTORS IN AGRICULTURAL FIELDS (BELGIUM)
Lemtiri, Aboulkacem ULg

Doctoral thesis (2015)

We investigated the effect of different agricultural practices on the abundances, biomass, and species diversity of earthworms. Specifically, we aimed to identify the relationship between certain soil ... [more ▼]

We investigated the effect of different agricultural practices on the abundances, biomass, and species diversity of earthworms. Specifically, we aimed to identify the relationship between certain soil physico-chemical properties and earthworm communities in agricultural soils. Two tillage systems and crop residue management were investigated. After conducting the study over four years, we found that the abundance, biomass, and diversity of earthworms were negatively affected by tillage application and the removal of crop residues. All ecological groups were negatively affected by conventional tillage system and crop residues exportation. However, crop residues removal had a greater impact than the conventional tillage system. In this study area, the earthworm community was dominated by the endogeic species A. c. caliginosa (64%), while few epigeic and anecic species were observed (5%). Endogeic and epi-anecic (L. terrestris) species appeared to be highly influenced by tillage and of crop residues exportation. When crop residues were exported from the field, the concentrations of chemical elements were low, particularly P and K nutrients. Earthworm activity contributed to nutrient dynamics and soil structure after four years of incorporating of crop residues to the fields and reduced tillage application. No consistent relationship was detected between soil and earthworm variables, even though different soil properties responded differently with respect to the tillage systems, crop residues removal and the presence of certain earthworm species. The number of years that our field was managed might have also affected our results.On the basis of the primarily research focused on understanding how earthworms participate and contribute towards improving soil quality (structure, nutrient dynamics and fertility), we subsequently focused on investigating how two plants (Vicia faba and Zea mays) and the Eisenia fetida earthworm contribute to uptake of different metals: Cd, Zn, Pb and Cu from the land surrounding of a former Zn-Pb ore treatment plant. Specifically, we tested whether the earthworm Eisenia fetida could act as a catalyzor to enhance phytoremediation efficiency. After 42 days of exposure, our results showed that certain earthworm life-cycle traits are affected by metal contamination and by the addition of plants. Specifically, the concentrations of metals in earthworm tissues decreased in the presence of plants. Our findings demonstrate that earthworm activities modify the availability of metals in soils, enhancing metal uptake by plants. This innovative system offers new investigation possibilities by considering earthworm-plant-soil interaction. In conclusion, this work confirmed that earthworms are important catalyzor optimizing the phytoremediation processes of polluted soils. [less ▲]

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See detailPhotométrie de haute précision dans l'infrarouge d'exoplanètes en transit
Lanotte, Audrey ULg

Doctoral thesis (2015)

The exploration of new lands has always been and is still an appealing quest of the Mankind. Today, these new worlds we are talking about are several light years away from us, and are called exoplanets ... [more ▼]

The exploration of new lands has always been and is still an appealing quest of the Mankind. Today, these new worlds we are talking about are several light years away from us, and are called exoplanets. Recently discovered, it is possible to study their structures, as well as their atmospheric compositions and properties, without the need to resolve their light from their host star. This is indeed possible when a planet regularly pass in front (transit) or behind (occultation) its host star from our point of view. The study of exoplanets and of their atmosphere is of prime importance. It could inform us on present conditions during their formation and evolution, and thus help us to characterise planets in our own Solar system. The characterisation of the orbital and atmospheric properties of transiting exoplanets is among the main goal of this thesis. We use observations in the infrared band, wherein exoplanet spectra present many atmospheric molecular transition features. However several infrared instrument systematics, particularly those on-board the Spitzer telescope (3.6–24 μm), have already led to divergent conclusions on the nature of planetary atmospheres it targeted, depending on the way these systematics were treated. Hence this thesis focuses on the high-precision infrared data reduction and analysis of transiting exoplanets. Our goal is to obtain accurate and non-ambiguous measurements for the characterisation of exoplanets through the recombination of their emission and transmission spectra. Meanwhile, we attempt to better understand the behaviour of infrared detectors in preparation for future missions in this wavelength range, such as the James Webb Space Telescope. This work is organised around the characterisation of the GJ 436 planetary system based on the data reduction and reanalysis of Spitzer observations and of CoRoT-2 with the help of ground-based and Spitzer observations. We use and optimise the partial deconvolution photometry program DECPHOT, fully appropriate to separate the stellar flux contributions from each other and from that of the sky, which is particularly important in the infrared. Besides, we improve aperture photometry. Then we use the Markov chain Monte Carlo algorithm developed by the Liège team to analyse the light curves produced by these two measurement techniques, in addition to radial velocity measurements that were also available for these systems. We introduce new features, including a mo- delisation of one of the Spitzer systematics, and a phase curve model adapted to eccentric planetary orbit. Our GJ 436b analysis rules out the presence of the two planetary companion candidates proposed recently in the literature. Contrary to former studies that were in disagreement, we measure an occultation depth at 3.6 μm that is independent of the light curve reduction, thanks to our modelisation of the intrapixel effect. We point out a weak stellar activity of its host star and suggest a metal rich atmosphere. Our CoRoT-2 b study leads to a very high emission measurement at 2.09 μm, which highlights an atmosphere in chemical and/or local thermodynamical disequilibrium. It may indicate the emission of H+3 , which results from high extreme UV stellar radiation or planetary aurora emission. [less ▲]

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See detailHigh resolution present and future climate and surface mass balance of Svalbard modelled by the regional climate model MAR
Lang, Charlotte ULg

Doctoral thesis (2015)

This worked aimed to simulate the climate and surface mass balance of Svalbard at high spatial resolution with the regional climate model MAR. First, simulations of the present (1979 - 2013) climate and ... [more ▼]

This worked aimed to simulate the climate and surface mass balance of Svalbard at high spatial resolution with the regional climate model MAR. First, simulations of the present (1979 - 2013) climate and surface mass balance were performed at a spatial resolution of 10 km. MAR was evaluated over Svalbard by comparing its outputs to measurements of temperature and precipitation measurement and outputs of other modelling products fo the surface mass balance. The results of the MAR simulations were then analysed over 1979 - 2013 and shoed a stability of the (negative) SMB opposed to the recent melt records observed in Greenland. This stability was attributed to a recent change in summer atmospheric circulation damping the Arctic warming over Svalbard. A future projection over 1980 - 2100 was then performed with MAR forced by MIROC5 and the RCP8.5 scenario and showed that the future SMB decrease is projected to be mainly driven by the albedo decrease (related to the expansion of the ablation area) through the increase of the net shortwave radiation absorbed by the surface.Finally, an online downscaling technique has been implemented in MAR to allow the surface modeule SISVAT, computing the surface mass balance and its components, to run at a resolution twice as high as the atmospheric module. This method, based on near-surface temperature and humidity corrections on a subgrid, allows SMB outputs at a resolution twice as high with only 25% more computation time. [less ▲]

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See detailCoherence and many-body effects in the transport of Bose–Einstein condensates
Dujardin, Julien ULg

Doctoral thesis (2015)

This thesis presents investigations on the interplay of coherence and many-body effects in the quasi one-dimensional transport of Bose-Einstein condensates (BEC) through scattering potentials. Such ... [more ▼]

This thesis presents investigations on the interplay of coherence and many-body effects in the quasi one-dimensional transport of Bose-Einstein condensates (BEC) through scattering potentials. Such configurations can be realized with guided atom lasers that provide a coherent atomic beam. An exact theoretical description of the dynamics is out of reach due to the presence atom-atom interactions. Different levels of approximations are nevertheless possible with their strengths and weaknesses. The mean-field approximation, where the dynamics of the BEC is governed by the Gross-Pitaevskii equation, is most commonly used in the field of ultracold atoms. In this thesis the truncated Wigner method is used to go beyond the standard Gross-Pitaevskii description. This method is adapted in order to study the scattering of Bose-Einstein condensates in one-dimensional waveguides where atom-atom interactions and external potentials are nonvanishing only in a finite region of space. In this case, the truncated Wigner method is combined with the smooth exterior complex scaling method and incorporates quantum noise that originate from the vacuum fluctuations in the waveguide. Inelastic scattering is shown to play a major role in the resonant transport of BEC through a symmetric double potential barrier effectively forming an atomic quantum dot. Indeed, fully resonant transmission is prohibited and incoherent atoms as well as collective oscillations are detected in the transmitted beam. It is also shown that inelastic scattering destroys Anderson localization in the case of transport through disordered potentials. The classical (incoherent) ohmic transmission is recovered for finite atom-atom interactions. The validity of the truncated Wigner method is then assessed using the semiclassical van Vleck-Gutzwiller propagator in the Fock space of the many-body system. It is shown that the truncated Wigner method corresponds to the so-called diagonal approximation, and it is possible to identify the leading correction to the truncated Wigner results, which is provided by the so-called coherent backscattering (CBS) contribution. Coherent basckattering in Fock space is a genuine quantum many-body effect that lies beyond the reach of any mean-field approach. For the case of closed Bose-Hubbard models, the relevance of CBS is confirmed by numerically comparing the (classical) truncated Wigner evolution probabilities to the exact quantum probabilities in Bose-Hubbard models: While a CBS-induced enhancement of the return probability to the initial state is clearly seen in the exact quantum simulations of the bosonic many-body system, this enhancement is absent in the classical calculations. The magnitude and dependence of the CBS contribution on gauge fields, which break time-reversal invariance, is numerically confirmed. For the case of disordered open systems, it can be shown that this contribution as well as next-to leading order contributions vanish thereby confirming the validity of the truncated Wigner method. [less ▲]

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See detailEtude de la mise en place du cytosquelette dans les cellules de l'organe de l'audition au cours du développement chez le rat
Johnen, Nicolas ULg

Doctoral thesis (2015)

An increasing number of people are affected by auditory deficiency. Several genes associated with deafness encode for cytoskeleton proteins that are expressed in cells of the inner ear. However, our ... [more ▼]

An increasing number of people are affected by auditory deficiency. Several genes associated with deafness encode for cytoskeleton proteins that are expressed in cells of the inner ear. However, our knowledge of cytoskeleton dynamics inside the inner ear is still incomplete. Up to now, most studies have principally focused on cytoskeleton organization at adult stages and not on its arrangement during development. In this work, we studied the development of the dynamic cytoskeleton structure in various cells of the rat organ of Corti, from its appearance at the 18th embryonic day (E18), to its functional state at the 25th post-natal day (P25). We used an indirect immunofluorescence method, which involves specific antibodies directed against different proteins from the three main types of cellular filaments: intermediate filaments (cytokeratines, vimentine), microtubules (βI–V-tubulin) and microfilaments (βcytoplasmic- and γcytoplasmic-actin). The labelling was performed on cryosections and then visualized through a laser scanning confocal microscope. A complementary ultrastructural analysis using transmission electronic microscopy was performed on select developmental timepoints. Our results clearly show that the cytoskeleton of the supporting cells plays a greater role in the development of the organ of Corti than that of the sensory hair cells. We observed an increase in the cytoskeletal organization of the supporting cells up to P6. We have shown that the cytoskeleton of supporting cells is highly developed during the deep disruptions of the auditory organ morphology appearing between P8 and P12. During this short period, we observed a partial epithelial-to-mesenchymal transition, which is marked by the temporary appearance of vimentine and a partial loss of cellular adhesion on the lateral face. At the same time, we also found a correlation between the onset of βV-tubulin expression and the formation of non-centrosomal microtubules arrays. Finally, the morphologically mature organ of Corti is characterized by a decrease of the cytoskeleton in some key regions of the cells. These observations underline the essential importance of the cytoskeleton in the maturation of the organ of Corti. [less ▲]

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See detailEnergetic study of solar-like oscillations in red giants
Grosjean, Mathieu ULg

Doctoral thesis (2015)

Observations of solar-like oscillations by CoRoT and Kepler space-borne telescopes, have opened new opportunities for the energetic modelling of these oscillations. In particular, oscillations propagating ... [more ▼]

Observations of solar-like oscillations by CoRoT and Kepler space-borne telescopes, have opened new opportunities for the energetic modelling of these oscillations. In particular, oscillations propagating in both the convective envelope and the radiative core of evolved low-mass stars, called mixed-modes, have been detected, allowing us to investigate various physical processes acting on oscillations in these two regions. Theoretical predictions for the linewidths and the amplitudes of solar-like oscillations, as obtained and discussed in this thesis, strongly depend on the treatment of the interaction between convection and oscillations. Observed properties of solar-like oscillations thus gives us the opportunity to test and constrain this treatment. The comparisons between observed and theoretical linewidths of main-sequence stars allow us to constrain the parameters of the time-dependent treatment of convection and to produce more accurate results. The remaining discrepancies will give us new clues for the improvement of the treatment of the interaction between convection and oscillations. The modelling of the energetic aspects of solar-like oscillations in red giants allows us to derive a detectability limit for mixed-modes. These results are in overall good agreement with typical red-giant observed power spectra. A detailed comparison between an observed subgiant and the corresponding theoretical predic- tions confirms that the main aspects of the observed energetic properties of solar-like oscillations are well reproduced by the theoretical modelling. Discrepancies between observed and theoret- ical linewidths of quadrupole mixed-modes lead us to invoke the existence of a new damping mechanism in the core of this star. [less ▲]

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See detailStructural optimization of flexible components within a multibody dynamics approach
Tromme, Emmanuel ULg

Doctoral thesis (2015)

Structural optimization techniques rely on mathematical foundations in order to reach an optimized design in a rational manner. Nowadays, these techniques are commonly used for industrial applications ... [more ▼]

Structural optimization techniques rely on mathematical foundations in order to reach an optimized design in a rational manner. Nowadays, these techniques are commonly used for industrial applications with impressive results but are mostly limited to (quasi-) static or frequency domain loadings. The objective of this thesis is to extend structural optimization techniques to account for dynamic load cases encountered in multibody applications. The thesis relies on a nonlinear finite element formalism for the multibody system simulation, which needs to be coupled with structural optimization techniques to perform the optimization of flexible components in an integrated way. To tackle this challenging optimization problem, two methods, namely the fully and the weakly coupled methods, are investigated. The fully coupled method incorporates the time response coming directly from the MBS in the optimization. The formulation of the time-dependent constraints are carefully investigated as it turns out that it drastically affects the convergence of the optimization process. Also, since gradient-based algorithms are employed, a semi-analytical method for sensitivity analysis is proposed. The weakly coupled method mimics the dynamic loading by a series of equivalent static loads (ESL) whereupon all the standard techniques of static response optimization can be employed. The ESL evaluation strongly depends on the formalism adopted to describe the MBS dynamics. In this thesis, the ESL evaluation is proposed for two nonlinear finite element formalisms: a classical formalism and a Lie group formalism. An original combination of a level set description of the component geometry with a particular mapping is adopted to parameterize the optimization problem. The approach combines the advantages of both shape and topology optimizations, leading to a generalized shape optimization problem. The adopted system-based optimization framework supersedes the classical component-based approach as the interactions between the component and the system can be consistently accounted for. [less ▲]

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See detailNumerical modeling of the cardiac mechano-electric feedback within a thermo-electro-mechanical framework. Study of its consequences on arrhythmogenesis.
Collet, Arnaud ULg

Doctoral thesis (2015)

This doctoral study characterizes, for simple geometries, the cardiac autonomous electrical activity induced by the mechanical deformations of the myocardium via the mechano-electric feedback within a ... [more ▼]

This doctoral study characterizes, for simple geometries, the cardiac autonomous electrical activity induced by the mechanical deformations of the myocardium via the mechano-electric feedback within a thermo-electro-mechanical framework. The underlying fundamental mechanisms are highlighted and discussed in detail. In a healthy heart, the mechano-electric feedback acts as a regulator able to damp mechanical perturbations undergone by the heart, by appropriately modulating electrical activity shortly after these perturbations. In this way, a new healthy electromechanical situation is recovered. However, under certain conditions, this feedback can be a generator of dramatic cardiac arrhythmias by inducing local electrical depolarizations resulting from abnormal cardiac muscle tissue deformations. These local perturbations can then propagate in the whole heart and, thus, lead to global cardiac dysfunctions. The one- and two-dimensional models developed in this work to study the arrhythmogenic consequences of the mechano-electric feedback within a thermo-electro-mechanical framework account for three couplings: the excitation-contraction coupling, the mechano-electric feedback, and the thermo-electric coupling. The excitation-contraction coupling allows the mechanical contraction of cardiac muscle cells resulting from the electrical excitation of these cells, triggered by a propagating action potential initially generated by the sino-atrial node in a healthy heart. The mechano-electric feedback takes into account the influence of mechanical deformations on the electrical activity, both at the cell and the macroscopic level. The thermo-electric coupling then modulates certain electrical properties due to a temperature change. The excitation-contraction coupling is modeled in a phenomenological way by combining the Aliev-Panfilov model and the Rogers-McCulloch model. The propagation of the electrical excitation through cardiac muscle tissue is modeled by using the monodomain approach. The mechano-electric feedback is taken into account by considering two different contributions, namely the physiological contribution (physiological feedback) and the geometric contribution (geometric feedback). The physiological feedback consists in the onset of stretch-activated currents due to the deformations of the cardiac muscle tissue via specific mechanosensitive channels. Regarding the geometric feedback, it simply reflects that the propagation of the depolarization waves is altered by the deformations of the geometry. The thermo-electric coupling is modeled via a dependence with respect to the temperature which is exponential for the gating kinetics of ion channels, exponential for the kinetics of the active tension development in cardiomyocytes, and linear for the ionic conductances. This study shows that the mechano-electric feedback can be arrhythmogenic under specific conditions. In particular, this work clearly reveals that the size of the domain and the importance of stretch-activated currents are key factors in the behavior of the autonomous electrical activity induced by the mechano-electric feedback. This doctoral study also shows that temperature variations such as those undergone by the heart during therapeutic hypothermia or hyperthermia play a central role in the cardiac electromechanical behavior. Moreover, this work emphasizes the influence of the initial conditions on the electromechanical behavior of cardiac tissue. In the one-dimensional framework, an important result of this work is that the disappearance of the autonomous electrical activity induced by the deformations of the cardiac muscle can be associated with different types of bifurcation phenomena, depending on the values of the parameters. These bifurcations, which correspond in fact to different ways for the AEA to vanish, are emphasized and discussed in detail. [less ▲]

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See detailAccurate Non-Iterative Modelling and Inference of Longitudinal Neuroimaging Data
Guillaume, Bryan ULg

Doctoral thesis (2015)

Despite the growing importance of longitudinal data in neuroimaging, the standard analysis methods make restrictive or unrealistic assumptions. For example, the widely used SPM software package assumes ... [more ▼]

Despite the growing importance of longitudinal data in neuroimaging, the standard analysis methods make restrictive or unrealistic assumptions. For example, the widely used SPM software package assumes spatially homogeneous longitudinal correlations while the FSL software package assumes Compound Symmetry, the state of all equal variances and equal correlations. While some new methods have been recently pro- posed to more accurately account for such data, these methods can be difficult to specify and are based on iterative algorithms that are generally slow and failure- prone. In this thesis, we propose and investigate the use of the Sandwich Estimator method which first estimates the parameters of interest with a (non-iterative) Ordinary Least Square model and, second, estimates variances/covariances with the “so-called” Sandwich Estimator (SwE) which accounts for the within-subject covariance structure existing in longitudinal data. We introduce the SwE method in its classic form, and review existing and propose new adjustments to improve its behaviour, specifically in small samples. We compare the SwE method to other popular methods, isolating the combination of SwE adjustments that provides valid and powerful inferences. While this result provides p-values at each voxel, it does not provide spatial inferences, e.g. voxel- or cluster-wise family-wise error-corrected p-values. For this, we investigate the use of the non-parametric inference approach called Wild Bootstrap. We again identify the set of procedures and adjustments that provide valid inferences. Finally, in the third and fourth projects, we investigate two ideas to improve the statistical power of the SwE method, by using a shrinkage estimator or a covariance spatial smoothing, respectively. For all the projects, in order to assess the methods, we use intensive Monte Carlo simulations in settings important for longitudinal neuroimaging studies and, for the first two projects, we also illustrate the methods by analysing a highly unbalanced longitudinal dataset obtained from the Alzheimer’s Disease Neuroimaging Initiative. [less ▲]

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See detailHull Optimization of Medium-Speed Monohull Passenger Ferries
Hetharia, Wolter Roberth ULg

Doctoral thesis (2015)

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See detailEtude d’un concentrateur solaire basé sur une combinaison optique diffractive/réfractive pour applications spatiales
Michel, Céline ULg

Doctoral thesis (2015)

Continued demand for new applications from spacecrafts leads to larger power needs. For most of them, the primary energy sources are solar panels. However, these solar panels are heavy and expensive ... [more ▼]

Continued demand for new applications from spacecrafts leads to larger power needs. For most of them, the primary energy sources are solar panels. However, these solar panels are heavy and expensive, mainly due to solar cells and their coverglass. The power need increase requires thus new concepts of solar panels. Furthermore, space environment is highly constraining: the vacuum limits heat trans- fer since convection is not allowed, there is contamination modifying the light spectrum reaching cells, ultraviolet light induces a yellowing of silicone glue, radiations degrade pho- tovoltaic cells, etc. Usually, multi-junctions (MJ) cells are used, that are strongly sensitive to spectral modification in their incident spectrum due to their series connected structure (the worst cell defines the whole output performance). The power dimensioning of solar panels is then based on end of life (EOL) PV cells expected performance. Reducing the sensitivity to increase EOL output power is then another challenge for space applications. This thesis aims to answer to both problems, by the proposition and study of a new lightweight solar concentrator with spectral splitting. This conceptual concentrator is composed of a Fresnel lens for sunlight concentration, coupled to a surface relief diffraction grating to spectrally split incident light, forming a single optical element in silicone. The concentration behavior allows a reduction of solar cells area (including its coverglass), replaced by a lightweight silicone lens, reducing the global cost and mass. The lateral spectral separation will permit other types of cells than the usual MJ cells. To demonstrate the concept, two single junctions (SJ) solar cells are placed side by side, the first collecting visible light, the second collecting near IR light. Since cells are electrically independent, sensitivity is lower and EOL output power can surpass standard MJ cells systems. Moreover, cells combination is nearly free: all photovoltaic technology can be used and combined, opening the solar concentration field to other technologies than MJ. This work studies and evaluates the pros and cons of diffraction grating/Fresnel lens combinations as solar concentrator with spectral splitting. The analysis includes the choice of material, optical developments and optimizations (grating selection, freeform lenses, grating period optimization along the lens, etc.), electrical modeling and methods to find the best cells combination as well as the modeling of expected output power, a thermal simulation, weight and deployment considerations, and approaches of sensitivity with spectral modifications. Some experimental results complete the study. Two main configurations were developed: a first with a blazed grating, and a second with a symmetrical lamellar grating. Both configurations, after optimization, show similar performances: a global geometrical concentration ratio around 5-6× (ratio between lens width and the total width of the two cells), a tracking error tolerance up to 0.7◦, no drastic degradation with respect to deformations, fabrication errors, etc., an output power at begin of life (BOL) better than a classical concentrator focusing on a SJ cell or a planar solar panel composed of SJ cells. Both configurations present also a BOL specific mass [kg/W] lower than a classical planar solar panel covered by MJ cells, and a lower sensitivity to space environment, with theoretical larger EOL output power depending on chosen PV cells combinations. Existing deployment systems are proposed and discussed. Also, an experimental prototype of the optical element was realized, with optical results close to simulations. Some adaptations to terrestrial concentrators, other spectra, or using more than 2 different SJ cells are also introduced, highlighting the versatility of our concept. Results demonstrate thus the coherence of the concept, leading to experimentally feasible and quite tolerant concentrator, with interesting cost reduction thanks to concentration and specific weight reduction. However, optical losses due to the non-perfect spectral splitting of the grating is too high to be able to surpass MJ cells systems BOL up to now, and the lower sensitivity of our concentrator cannot completely compensate this lack of performance at EOL. To reach better performances than MJ systems, from cost, mass, radiation resistance, etc. point of view and to exploit the obvious gain in sensitivity, the concentrator needs thus further investigations mainly related to cells combinations. Especially as our concept opens a lot of opportunities thanks to the complete independence of cells: other technologies are allowed, specific coatings can improve performances, ... Applications for Earth or places with different/changing incident spectra is another plausible perspective. Our concentrator with spectral splitting can also be a major advantage for specific scientific space missions like deep space missions. [less ▲]

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See detailHormones, Simulated Microgravity and Hypergravity affect Bone and other Physiological Systems in Zebrafish Larvae
Aceto, Jessica ULg

Doctoral thesis (2015)

Zebrafish (Danio rerio) are increasingly used for physiological, genetic and developmental studies. Understanding the consequences of altered gravity on bone development and on general physiology in an ... [more ▼]

Zebrafish (Danio rerio) are increasingly used for physiological, genetic and developmental studies. Understanding the consequences of altered gravity on bone development and on general physiology in an entire organism remains to date incomplete. We used altered drug treatment and gravity experiments to evaluate their effects specifically on bone formation and more generally on whole genome gene expression. We started treatments at 5 days post-fertilization (dpf) and analyze early modifications in gene expression after 1 day using microarrays and the consequences on bone formation after 5 days using specific staining. We performed chemical treatments (Parathyroid Hormone, Vitamin D3), exposure to three different microgravity simulation devices (Clinostat, Random Positioning Machine and Rotating Wall Vessel) and finally exposure to hypergravity and "relative microgravity" in the Large Diameter Centrifuge. By combining morphometric tools with an objective scoring system for the state of development for each element in the head skeleton, and specific gene expression analysis, we confirmed and characterized in detail the decrease or increase of bone formation caused by a 5 day treatment (from 5dpf to 10dpf) with, respectively parathyroid hormone (PTH) or vitamin D3 (VitD3). Microarray transcriptome analysis after 24 hours treatment reveals a general effect on physiology upon VitD3 treatment, while PTH causes more specifically developmental effects. The microgravity simulators used were the 2D clinostat, random positioning machine and rotating wall vessel. Only clinorotation caused a significant decrease of bone formation when applied between 5 to 10dpf. This effect was not due to stress, as assessed by measuring cortisol levels in treated larvae. The two other devices caused no effect, or a slight acceleration of ossification. Gene expression results after one day in simulated microgravity indicate that musculo-skeletal, cardiavascular, and nuclear receptor systems are affected, however often in opposite directions in clinorotation compared to the two other devices. Based on the effects on bone formation and on the biological functions found to be affected, we conclude that clinorotation is the most appropriate method to simulate microgravity on ground when using free-swimming organisms such as zebrafish larvae. Hypergravity (3g from 5dpf to 9 dpf) exposure results in a significantly larger head and a significant increase in bone formation for a subset of the cranial bones. Gene expression analysis after 24hrs at 3g revealed differential expression of genes involved in the development and function of the skeletal, muscular, nervous, endocrine and cardiovascular systems. Finally, we propose a novel type of experimental approach, the "Reduced Gravity Paradigm", by keeping the developing larvae at 3g hypergravity for the first 5 days before returning them to 1g for one additional day. 5 days exposure to 3g during these early stages also caused increased bone formation, while gene expression analysis revealed a central network of regulatory genes (hes5, sox10, lgals3bp, egr1, edn1, fos, fosb, klf2, gadd45ba and socs3a) whose expression was consistently affected by the transition from hyper- to normal gravity. [less ▲]

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See detailChondrogenic Differentiation in the growth Plate: a Computational Modelling Approach
Kerkhofs, Johan ULg

Doctoral thesis (2015)

The specialization of cartilage cells, or chondrogenic differentiation, is an intricate and meticulously regulated process that plays a vital role in both bone formation and cartilage regeneration. This ... [more ▼]

The specialization of cartilage cells, or chondrogenic differentiation, is an intricate and meticulously regulated process that plays a vital role in both bone formation and cartilage regeneration. This PhD work centers on the development of computational models to study the molecular regulation of this process. First, we investigate how individual genes and their defects contribute to the overall change in functionality of the growth plate, where chondrogenic differentiation fuels bone growth. As each gene is influenced by a myriad of feedback mechanisms that keep its expression in a desirable range, predicting what will happen if one of these genes defaults is challenging. Therefore, we constructed a qualitative model, focusing on the process of bone formation, that simulates how the intricate interplay between the genes results in a functional growth plate morphology. This model allows the effect of gene knockouts or overexpression to be evaluated from a network perspective, and hence relates this genetic deficiency to the impairment of the gross bone formation on a tissue level. This knowledge can be of great assistance in the design and control of \textit{in vitro} bone tissue engineering processes. A framework with increased temporal and quantitative resolution is then used to study chondrocyte hypertrophy in an expanded network. Chondrocyte hypertrophy, a process in which cartilage cells enlarge and change their secretion profile to attract bone forming cells and blood vessels, is orchestrated on a molecular level by a switch between two ‘genetic programs’. In this switch, one set of transcription factors that represents chondrocyte proliferation competes with, and is ultimately replaced by, another set that represents hypertrophy. Since hypertrophy plays a vital role not only in the development the skeleton, but is also thought to be involved in several bone-related diseases, it has been studied extensively. We combine information of how individual factors that prevent or contribute to the hypertrophic switch interact in a computational model to develop a more global view of the regulatory network underlying hypertrophy. Through simulations of this regulatory network model we can perform an in silico screening for factors that greatly impact, positively or negatively, the decision to undergo hypertrophy. The results of this screening are checked for consistency using an ensemble approach. Specifically, a genetic algorithm is used to generate an ensemble of models, differing only in parameter values, whose qualitative dynamics match those observed in the growth plate. The range of behaviour exhibited by individual factors throughout this ensemble is mostly consistent. Additionally, a subset of the network topology is compared to that obtained by inference from growth plate expression profiles. Understanding how individual factors contribute to the hypertrophic switch in the context of the regulatory network has important repercussions in both cartilage and bone tissue engineering. Our approach further suggests several putative targets for intervention in disease processes where hypertrophy plays a role. In summary, this PhD offers and explores a series of tools that form a first step to a rigorous and systems-level understanding of chondrogenic differentiation. [less ▲]

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See detailDynamical modelling from resting-state brain imaging
Liegeois, Raphaël ULg

Doctoral thesis (2015)

The statistical dependencies among neuroimaging time courses observed in different brain regions are collectively named functional connectivity (FC). This quantity is widely used in order to characterize ... [more ▼]

The statistical dependencies among neuroimaging time courses observed in different brain regions are collectively named functional connectivity (FC). This quantity is widely used in order to characterize normal brain functioning or neurodegenerative diseases. It is classically measured in a static way, by averaging the dependencies over the whole imaging acquisition. However, there is increasing evidence that considering the temporal fluctuations of FC leads to a finer description of FC properties and corresponding brain function. This observation is the starting point of the work developed throughout this thesis. First, we study the role of cerebral anatomy in the FC fluctuations. We observe that it guides transitions of FC between different patterns supporting consciousness-related processes such as mind wandering. Following this new characterisation of the fluctuating nature of FC, we develop statistical tools capturing static and dynamic properties of FC. We first introduce three markers of FC, collectively named spatiotemporal connectivity (STC), and computed from the power spectral density of the neuroimaging time series. STC captures spatial properties of FC, as classically computed, but also dynamical properties. We show on real data that STC provides a finer characterisation of FC, as well as higher robustness against inherent flaws of the imaging modality considered in our study. Then, in order to identify dynamical patterns of FC at the whole-brain level, we recast the concept of component analysis in the context of dynamical models. The corresponding development is based on a particular representation of statistical interactions: dynamical graphical models. We first propose an algorithm providing a decomposition of these models in a sparse contribution, reflecting parsimony of the direct interactions between cerebral regions, and a low-rank contribution, modelling the presence of hidden variables spreading a common behaviour in many of these regions. Then, we propose to interpret the identified hidden variables as dynamical neuronal networks, as for component analysis, but with an additional spectral characterisation of the corresponding components. In conclusion, this thesis presents descriptive contributions from the analyses of several datasets, and methodological contributions inspired from the properties of these datasets. [less ▲]

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See detailThe role of feedback in maintaining robustness and modulation across scales: Insights from cellular and network neurophysiology
Dethier, Julie ULg

Doctoral thesis (2015)

The brain is a complex system made of many components acting at very dif- ferent resolution levels, from the microsecond and nanometer scales with ion channels to hours and brain-wide scale with proteins ... [more ▼]

The brain is a complex system made of many components acting at very dif- ferent resolution levels, from the microsecond and nanometer scales with ion channels to hours and brain-wide scale with proteins. The brain dynamics and functions emerge from the interactions between these resolution levels. Math- ematical modeling is a powerful ally to uncover some of the brain organizing principles and mechanisms. From this perspective, the question of which cel- lular details must be retained at the network level is largely open. Motifs simplify systems by approximating the wiring diagram and by taking advantage of the timescale separation between processes. Yet, motifs study each resolution level separately and neglect couplings between levels. This approach falls short of system-level questions and multiresolution intrinsic properties. The present dissertation aims at narrowing the gap by looking at the inter- play between resolution levels. We propose to extract essential elements, in the form of feedback loops, to be maintained from one resolution to the next in the hope of a better understanding of brain functions and diseases. The focus is on the spatiotemporal upscaling from the neuron to the network level and, in particular, on the maintenance of modulation and robustness properties across scales. This approach is used in a two-neuron network and is extended to a prospective multiresolution excitability framework. The main contributions of this dissertation are the following. We identify the key role of a cellular feedback loop for network oscillation robustness and modulation. Rhythms are crucial in the brain functioning but much awaits to be understood regarding their control, regulation, and function. In a mutually-inhibitory network, we isolate an essential cellular property—a positive feedback loop in the slow timescale—to be retained at the network level to ensure modulation and robustness of network oscillations. We highlight the peculiar role that a cellular feedback loop can play for the regulation of network switches. We identify that a cellular positive feedback loop brings localization properties, both temporally and spatially, to network oscillations. The emerging picture suggests a basal ganglia network model valid both in healthy movement-related oscillations and in parkinsonian conditions. Multiresolution excitability emerges due to localization properties of ex- citable systems: different excitability resolution windows can be superposed and interact, generating multiresolution systems. In each window, the system is characterized via its transfer properties and input-output behavior. Signal processing properties appear in these multiresolution systems and endow mul- tiresolution objects with gating and multiplex signaling capabilities. In conclusion, the present dissertation provides novel insights on the impor- tance of the interplay between cellular and network levels. This multiresolution motif perspective is thought to be general and not specific to neuroscience. Fi- nally, exploiting the concept in multiresolution technologies is suggested. [less ▲]

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See detailEtude et caractérisation de mousses aqueuses sous contrainte
Bronfort, Ariane ULg

Doctoral thesis (2015)

De nombreuses questions subsistent quant à la nature d’une interface entre une mousse et une solution. Ce travail concerne l’influence des conditions aux limites au niveau d’une telle interface sur le ... [more ▼]

De nombreuses questions subsistent quant à la nature d’une interface entre une mousse et une solution. Ce travail concerne l’influence des conditions aux limites au niveau d’une telle interface sur le volume de mousse lorsqu’elle est perturbée par une contrainte extérieure. Le lien entre mousse et interface a été étudié dans deux situations différentes : une contrainte normale et une contrainte tangentielle. L’instabilité de Faraday permet de soumettre l’interface à une contrainte normale périodique. L’influence de la géométrie du système a été investiguée pour une surface libre. La modification de la longueur d’onde a été expliquée en terme d’augmentation de l’énergie interfaciale. La perte d’énergie a également été modélisée à l’aide de trois sources : la viscosité de la solution, la présence de molécules de surfactants à la surface et la condition de non-glissement aux parois. L’interaction entre une mousse et l’instabilité de Faraday est ensuite étudiée. La dissipation visqueuse est augmentée par la présence de bulles et a pu être modélisée à l’aide de considérations énergétiques. Il a également été montré qu’un faible nombre de couches de bulles est suffisant pour amortir efficacement toute perturbation de l’interface. La contrainte tangentielle est appliquée à l’interface grâce à un dispositif inspiré des milieux granulaires permettant la rotation d’une cellule de Hele-Shaw autour de son centre. Dans un tel dispositif, les caractéristiques de la mousse et de l’interface varient. Deux modèles prédictifs permettent d’expliquer l’évolution temporelle de la fraction de liquide moyenne. Des outils statistiques ont permis de définir une relation entre les déformations des bulles et les caractéristiques macroscopiques de la mousse. Grâce à la modélisation de l’écoulement, un lien a été établi entre le gradient de pression interne de la mousse et la déformation de l’interface. Finalement, nos résultats sont comparés à ceux obtenus pour des ensembles granulaires dans un dispositif expérimental similaire. [less ▲]

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See detailEfficient and Precise Trajectory Planning for Nonholonomic Mobile Robots
Lens, Stéphane ULg

Doctoral thesis (2015)

Trajectory planning is one of the fundamental problems in mobile robotics. A wide variety of approaches have been proposed over the years to deal with the various issues of this problem. This thesis ... [more ▼]

Trajectory planning is one of the fundamental problems in mobile robotics. A wide variety of approaches have been proposed over the years to deal with the various issues of this problem. This thesis presents an original and complete solution to tackle the motion planning problem for nonholonomic mobile robots in two-dimensional space. Given a set of obstacles, an initial and a goal configuration, the problem consists in computing efficiently a physically feasible trajectory that reaches the specified target as fast as possible. One of the original aspects of this work lies in the decomposition of the general problem into several simpler subproblems, for which very efficient solutions are developed. Their combination provides a complete trajectory planning approach that is one of the most computationally effective method suited for the motion of cylindrically shaped wheeled mobile robots in the presence of polygonal obstacles. This complete solution consists of three main steps. The first one is aimed at finding a short path that avoids obstacles and manages to reach the destination, without taking into account nonholonomic constraints of the robot. Our path planning method relies on an original refinement procedure of a constrained Delaunay triangulation of the obstacles, that outperforms other existing planning techniques. The second step consists in interpolating paths into smooth curves that can be followed by a real robot without slowing down excessively. By joining only two arcs of clothoids for moving from one curvature to another, our approach is simpler and also computationally cheaper than other interpolation methods. Finally, thanks to the introduction of an original discretization scheme, an efficient algorithm for computing a time-optimal speed profile for arbitrary paths is presented. The speed profile that results from this procedure not only allows the robot to follow the synthesized path as fast as possible while taking into account a broad class of velocity and accelerations constraints, but also provides the accurate advance information necessary to implementing coordinated actions during the displacement of the robot (e.g., between the locomotion system and other actuators). [less ▲]

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See detailAnalyse du déterminisme génétique de l’inhibition de la synthèse du gossypol dans la graine chez la descendance de l’hybride [(Gossypium hirsutum L. x G. raimondii Ulb.)² x G. sturtianum Willis]
Diouf, Fatimata Bintou Hassédine ULg

Doctoral thesis (2015)

Several analyses were performed in advanced generations of HRS [(Gossypium hirsutum x G. raimondii) ² x G. sturtianum] hybrid. These were obtained by backcrossing and selfing HRS plants expressing the ... [more ▼]

Several analyses were performed in advanced generations of HRS [(Gossypium hirsutum x G. raimondii) ² x G. sturtianum] hybrid. These were obtained by backcrossing and selfing HRS plants expressing the glanded-plant and glandless-seed trait of G. sturtianum. The purpose is to understand why it is not possible to fix this target character in the HRS progeny. Thus, HRS BC2S5, BC2S6, BC2S7, BC3S4, ♂BC4S3, ♂BC4S4, ♀BC4S3 and ♀BC4S4 plant populations were studied. Agro-morphological observations carried out on the studied plant material showed in all analyzed progenies significant fertility problems as manifested by high rates of embryo abortion, poor germination of seeds and premature mortality of many seedlings. Moreover, major phenotypic differences were observed between the HRS plants and upland cotton. Genomic in situ hybridization analysis (GISH) demonstrated that the magnitude of these problems is related to the importance of the presence of genetic material of the Australian species in HRS hybrids. The analysis of the plant material with the 10 SSRs markers, mapped on c2-c14, c3-c17, and c6-c25 linkage groups of G. hirsutum, points out very important segregation distortions (SD). Genotypic profiles were almost always heterozygous. These SD are caused by gametic and/or zygotic selections that occur respectively before and/or after fertilization. GISH showed the presence of one (1) to four (4) whole G. sturtianum chromosomes and one to two large fragments of G. sturtianum chromosomes. This structural heterozygosity is implicated in the SD observed. However, the massive presence of alien genetic material hardly affected the chromosome pairing and pollen fertility of the analyzed hybrid plants. This is contradictory to the observed SD and suggests a certain genetic balance in the analysed hybrids. It thus indicates no, or very weak interaction between the chromosomes of G. sturtianum and those of G. hirsutum into the genome of HRS derivatives. The expression of the desired character is very complex, but it is certain that: (i) the factors responsible for the desired trait are better transmitted through the ovule than the pollen, (ii) the alleles involved in the expression of the target trait operate both according to the additive and epistatic models, (iii) the increase of the G. hirsutum genetics background in the most advanced generations of the HRS hybrid is accompanied by a decrease of the expression of the desired trait, (iv) seeds viability problems affect both seeds with or without gossypol glands, whether they are well formed or malformed, showing the independence between at least a part of the imbalance factors and those related to the expression of researched character. Several G. sturtianum genes appear to be involved in the control of the target trait. However, the strong SD that characterizes the analyzed plants questions the reliability of this result obtained through single-marker analysis. A resumption of the breeding program using agro-morphological characterization tools, SSR and GISH, in the early generations of backcrossing, should help to better guide the selection program towards obtaining stable plants that express the character. [less ▲]

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See detailIdentification et caractérisation des progéniteurs pancréatiques et des précurseurs endocrines durant l'embryogenèse chez le poisson-zèbre
Ghaye, Aurélie ULg

Doctoral thesis (2015)

Le diabète survient lorsque le nombre ou la fonction des cellules β, productrices d’insuline est affecté. Le nombre de personnes atteintes par cette maladie croît de manière impressionnante d’année en ... [more ▼]

Le diabète survient lorsque le nombre ou la fonction des cellules β, productrices d’insuline est affecté. Le nombre de personnes atteintes par cette maladie croît de manière impressionnante d’année en année. Bien qu’il puisse être contrôlé par des injections régulières d’insuline, ce traitement est contraignant, coûteux et ne permet pas d’éliminer toute une série d’effets secondaires chez le patient diabétique. Un des challenges à l’heure actuelle est de développer des stratégies qui permettraient de remplacer ces cellules. La régénération in vivo constitue une approche thérapeutique attrayante. Cependant, cette régénération est peu efficace chez les mammifères et un défi majeur consisterait à la stimuler. Contrairement aux mammifères, le poisson-zèbre (Danio rerio), est un modèle de choix pour étudier la régénération puisqu’il possède le remarquable pouvoir de régénérer les cellules β rapidement et efficacement après leur ablation ciblée. Néanmoins, il est important d’identifier et de caractériser les cellules pancréatiques qui donnent naissance aux cellules β afin de connaître l'ensemble des facteurs et voies de signalisation contrôlant leur formation. Le but de mon doctorat s’est inscrit dans cette démarche d’identification et de caractérisation des cellules progénitrices. Pour ce faire, nous avons généré deux lignées transgéniques qui nous ont permis de suivre le destin des cellules exprimant le facteur de transcription Nkx6.1 et Ascl1b. Par des expériences de traçage de lignée, nous avons montré que les cellules Nkx6.1+ marquent des progéniteurs pancréatiques qui donnent naissance à toutes les lignées pancréatiques alors que les cellules Ascl1b marquent des précurseurs endocrines qui ne donnent naissance qu’à la lignée endocrine. Nous avons aussi montré qu’au début du développement pancréatique, les deux facteurs sont exprimés dans les mêmes cellules pancréatiques puis se séparent rapidement. Cette ségrégation n’est pas la conséquence d’une répression mutuelle entre Ascl1b et Nkx6.1 mais est due à un effet opposé de la voie de signalisation Notch qui maintient l’expression de nkx6.1 et réprime l’expression d’ascl1b. [less ▲]

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See detailSedimentary development and correlation of long-term off-reef to shallow-water Devonian carbonate records in Europe
Pas, Damien ULg

Doctoral thesis (2015)

The Devonian Period was characterized by extensive shallow-marine regions, with the largest carbonate platform development of the Phanerozoic Eon. The research carried out in this thesis integrates field ... [more ▼]

The Devonian Period was characterized by extensive shallow-marine regions, with the largest carbonate platform development of the Phanerozoic Eon. The research carried out in this thesis integrates field work, petrographic analysis, conodont biostratigraphy, elemental and carbon isotope geochemistry, magnetic susceptibility and magnetic hysteresis measurement. The aim, to better understand and characterize the environmental conditions that led to the development of three of the largest European Devonian carbonate platforms. This multi-disciplinary study also proposes to validate the use of magnetic susceptibility as a reliable tool for palaeoenvironmental reconstruction and long-distance correlation in marine carbonate. Fieldwork was conducted on four key sections of the European Pre-Mesozoic massifs: the Ardennes (La Thure and Fromelennes-Flohimont), the Rheinisches Schiefergebirge (Burgberg) and the Carnic Alps (Freikofel). The large quantity and in-depth analysis of rock samples and thin-sections has demonstrated the fascinating environmental diversity that shaped the carbonate platforms in the Rhenohecynian and Paleotethys oceans towards the mid-late Devonian times. The aforementioned analysis has enabled the development of reconstructed sedimentary models and large-scale shallowing-deepening histories for each section. New and published biostratigraphic data provided reliable age constraints for the foremost environmental changes evident in each of the sections. δ13C results from the Frasnian – Famennian boundary in the Burgberg and Freikofel sections have revealed Kellwasser events in limestone lithologies. Based on the analysis of ±1800 samples, a high-resolution magnetic susceptibility (MS) curve for each section has been developed, highlighting the strong link between the MS signatures and the syn-sedimentary parameters, such as carbonate productivity/sedimentation rate, water agitation and siliciclastic input. The comparison between MS and elemental geochemistry datasets has demonstrated the inherent-parallel link existing between the siliciclastic input proxies and the variation in MS signature in each of the sections. Magnetic hysteresis measurements have shown that ferromagnetic minerals such as magnetite control the MS signal. By comparing our data sets with published data we could confirm that our MS signal is remagnetized. However links between siliciclastic input proxies and MS, and between MS and environmental parameters have proven a relatively good preservation of the primary depositionally-induced MS signal. Finally, by integrating complete data and establishing a correlation chart including the four long-term MS curves, it is apparent that on a regional scale long-term MS trends can be correlated, as long as the evolution of the main depositional setting in the sections studied remains comparable. The significant impact of syn-sedimentary parameters on the final MS signature seems to obscure the imprint of parameters driving variations in continental erosion (e.g., climate, sea-level and tectonic variations) and therefore limiting the inter-regional correlations. This collaborative project on time-series analysis of long-term high-resolution MS records in the Dinant Syncline has revealed the imprint of astronomical parameters, giving rise to a more accurate estimate of the Givetian Stage’s duration. [less ▲]

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See detailComposite dark matter and direct-search experiments
Wallemacq, Quentin ULg

Doctoral thesis (2015)

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See detailL'agame-papillon géant, Leiolepis guttata (Cuvier, 1829), dans la province de Binh Thuan, Vietnam : biologie, écologie, alimentation, enjeux économiques et gestion d'élevage
Tran, Tinh ULg

Doctoral thesis (2015)

Nous avons d'abord considéré la viande et les oeufs de lézard pour la consommation humaine à travers le monde. Nous démontrons l'importance de cette ressource comme source de nourriture humaine de bonne ... [more ▼]

Nous avons d'abord considéré la viande et les oeufs de lézard pour la consommation humaine à travers le monde. Nous démontrons l'importance de cette ressource comme source de nourriture humaine de bonne qualité. Suite à l’apparition en 2004 des premiers élevages de Leiolepis gutatta, l’agame-papillon géant, dans la province côtière de Binh Thuan, aux succès qui s’ensuivirent et à leur importance pour les petits paysans de cette région semi-désertique où les productions agricoles sont extrêmement limitées à cause du climat et du sol, cette espèce a été choisie pour nos recherches. Notre étude vise à disposer de meilleures connaissances de Leiolepis guttata concernant sa biologie, son écologie, son alimentation et ses enjeux économiques, le tout débouchant sur une meilleure gestion de l’élevage. Nous envisageons en premier lieu sa distribution, son milieu de vie naturel, les types de formations végétales et les écosystèmes où il s’observe. Le climatope, l’édaphotope et les phytocénoses concernées ont été étudiés et définis. Un herbier de référence (MRT) a été constitué et un CD réalisé. L’alimentation constitue le thème suivant. Il s’appuie sur des observations préliminaires concernant le tractus digestif de l’agame-papillon ; les fractions végétales, animales et minérales observées dans les estomacs sont étudiées ; des enquêtes auprès des éleveurs ont été menées afin de recueillir des informations sur les aliments (essentiellement les végétaux) consommés par ce lézard. Au cours de ce travail, nous avons montré que Leiolepis guttata était un lézard essentiellement herbivore à même de consommer et de digérer un très grand nombre de végétaux en fonction des opportunités et disponibilités alimentaires. Nous avons approché la diversité alimentaire tant en milieu naturel qu’en élevage (116 produits différents, dont 91 relèvent du règne végétal et 22 du règne animal). La composition chimique de 71 plantes et 4 insectes a été déterminée. Nos observations ont également mis en évidence la présence importante de vers parasites (Oxyuridae notamment). Le nombre d’élevages de Leiolepis guttata dans la province de Binh Thuan a considérablement augmenté entre 2007 et 2013 afin de satisfaire une demande forte de ces reptiles soit pour la consommation de viande très prisée dans cette région touristique, soit comme reproducteurs ; par contre après avoir atteint des valeurs très élevées, les prix de vente sont en diminution depuis ces toutes dernières années : l’offre dépassant la demande. Si l’élevage s’est développé, c’est de façon anarchique, sans connaissances techniques de la part des éleveurs, mais surtout par échange d’expériences entre eux. Les enclos d’élevage, leur aménagement et l’achat des reproducteurs constituent un point important pour la réussite de ce type d’élevage. Notre travail apporte donc des informations sur les principaux avantages et inconvénients des types d'enclos actuels. Ensuite, nous formulons des recommandations pour la construction et l'aménagement d'enclos d'élevage adaptés aux conditions locales en ce compris une étude des coûts et revenus. Parallèlement au développement des élevages, on constate également une très forte régression de l’espèce dans le milieu naturel de plus en plus dégradé suite au développement des infrastructures routières et touristiques de la région. En conclusion, si l’élevage en captivité de Leiolepis guttata peut contribuer au maintien de l’espèce dans cette région, la durabilité de la production pour les éleveurs nécessite qu’ils acquièrent de meilleurs connaissances techniques quant à la biologie, l’écologie, l’alimentation et la gestion de l’élevage sans nécessairement rechercher des solutions techniquement optimales souvent coûteuses et non rentables pour ce genre de production. A l’avenir, une attention particulière devrait être apportée aux besoins nutritionnels en fonction des stades physiologiques, aux aspects génétiques (consanguinité) et aux risques de maladies liées à ces élevages en forte densité. Enfin, une régulation entre l’offre et la demande doit impérativement être recherchée. [less ▲]

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See detailAb-initio study of thermoelectricity of layered tellurium compounds
Ibarra Hernández, Wilfredo ULg

Doctoral thesis (2015)

In this thesis, we explore the electronic, dynamic and thermoelectric properties of different tellurium-based compounds. We perform ab-initio calculations within the Vienna Ab-initio Simulation Package ... [more ▼]

In this thesis, we explore the electronic, dynamic and thermoelectric properties of different tellurium-based compounds. We perform ab-initio calculations within the Vienna Ab-initio Simulation Package (VASP) that works in the framework of Density Functional Theory (DFT). For the thermoelectric properties, we use the Boltztrap code that solves the Boltzmann Transport Equations (BTE) for electrons within the Constant Relaxation Time Approximation (CRTA). This computational package allows us to obtain accurate values of the Seebeck coefficient as a function of temperature and carrier concentration (this last with the help of the rigid band approximation). While for the calculation of the lattice contribution to the thermal conductivity, we use the ShengBTE code that solves the BTE for phonons iteratively. The first tellurium-based compound that we study is the best room temperature thermoelectric material, Bi2Te3. We obtain results comparable with experimental data for the Seebeck coefficient at room temperature and pressure. Afterwards, we proceed to explore the evolution of the electronic properties and the thermoelectric performance under pressures up to 5 GPa. We reproduce the overall trend of the Seebeck coefficient as a function of pressure for two different values of doping, however, our results do not reproduce the small improvement found in experiments close to 1 GPa. Nevertheless, we support the experimental evidence of an Electronic Topological Transition (ETT) around 2 GPa and we explain this particular behavior. We also perform calculations on the tellurium-based phase-change materials (GeTe)x(Sb2Te3)1 (with x = 1, 2, 3). We show results for different stacking configurations since for some compositions, the stacking arrangement of the atoms in the primitive cell is still unsettled. We find that the change of the atomic arrangement leads to the systems to go from semiconductors to metals. We find that the semiconductor arrangements systematically overestimate the experimental values for the Seebeck coefficient, whereas the metallic stacking sequences are in very good agreement with the experimental data for the Seebeck coefficient and for the lattice contribution to the thermal conductivity. We show that (GeTe)x(Sb2Te3)1 materials could reach values of ZT=0.5 around 600 K with a proper optimization of S with respect to the carrier concentration. We also report that in the case of x=3, the most accepted stacking configuration is dynamically unstable, therefore we proposed another sequence. Finally, we discuss the discrepancies between our work and recent theoretical reports that claim the existence of a Dirac-cone like band structure for (GeTe)2(Sb2Te3)1. We explain the conditions necessary to obtain such electronic topology. [less ▲]

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See detailImportance des résidus lysine 70 et tryptophane 154 sur la structure, la stabilité, la carbonatation et l'activité de la béta-lactamase OXA-10 de Pseudomonas aeruginosa
Baurin, Stéphane ULg

Doctoral thesis (2015)

SUMMARY : This thesis was conducted to highlight the biochemical and structures impact of conserved residues of the beta-lactamase OXA-10 isolated from P. aeruginosa. The beta-lactamase OXA-10 production ... [more ▼]

SUMMARY : This thesis was conducted to highlight the biochemical and structures impact of conserved residues of the beta-lactamase OXA-10 isolated from P. aeruginosa. The beta-lactamase OXA-10 production is one of the main responsible to the beta-lactam antibiotics resistance of Pseudomonas strains. This work is subdivided in five chapters. The first is focused on the organization of class D beta-lactamase in sub classes. We have created by identity analysis, 21 sub classes that reflect an easy discrimination between proteins variability and mutants. This methodology is able to organize the enzymes as function of a parental enzyme but also based on the substrate profiles. The second chapter regroups the studies that target the importance of the residue tryptophan 154 carried by the Omega loop. The substitution of the residue tryptophan 154 by an alanine, a glycine or an phenylalanine leads to a large decrease of i) the catalytic activity, ii) of the affinity toward to CO2 and iii) on the enzyme stability. The structural data show an absence of lysine 70 modification and a large modification of the hydrogen network throughout the mutants structures. The various complexes resolved by R-x diffraction of the W154A mutant indicate that the deacylation rate is the most impacted. The third chapter makes an analogy between the available structural informations of others proteins characterized by a carboxylation modification. Others serine enzymes known to be not modified were also integrated in the analysis. The data reveal that the presence of a tryptophan residue seems to be necessary. We notice the presence of a large hydrophobic area with various shape near of the modified lysines. The calculation of the theoretical pKa values of the lysines seems to indicate a large decrease of the values that lead to an unprotonated form at physiological pH. The fourth chapter describes, the role of the lysine 70. The substitution of the lysine by a cysteine or a glutamate leads to a large decrease of the catalytic activity and an absence of carboxylation. At the opposite, the protein stability is not impacted, and an increase of stability is observed for the K70C mutant. The structural data show that the overall fold and structures localization are conserved. The complex obtained with the nitrocefin proves that the mutant is always able to react with the beta-lactams compounds and show that the deacylation step is rate limiting. Finally, the last chapter regroups the effect of pH on the structure, the dimerization, the stability and the catalytic activity. The data show that in the tested conditions the OXA-10 beta-lactamase is in a dimeric form at physiological pH. The addition of CO2, leads the formation of a more compact enzyme form. At high pH (10), the monomer is observed, while a fast equilibrium between the monomer and the dimer is observed between the pH 7.5 and 10. The enzyme is characterized with similar stability as function of pH. The addition of CO2 leads an increase of the stabilities. In tested conditions, the OXA-10 beta-lactamase is characterized by two optimum pH in presence or not of CO2. The CO2 addition leads to a large increase of the catalytic constant. The biophysics' studies reveal that in absence of CO2, subtle modifications are observed as function of pH, but that the addition of CO2 leads theirs disappearance. [less ▲]

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See detailFirst-Principles Study on the Lattice Dynamics and Thermoelectric Properties of Materials
Miao, Naihua ULg

Doctoral thesis (2015)

Thermoelectricity has been regarded as one of the most promising strategies for clean, low-cost and environmental friendly sustainable energy for several decades. Perovskite oxides, like SrRuO3, are ... [more ▼]

Thermoelectricity has been regarded as one of the most promising strategies for clean, low-cost and environmental friendly sustainable energy for several decades. Perovskite oxides, like SrRuO3, are considered as a potential thermoelectric material for low-cost and large-scale thermoelectric applications due to their good thermal and chemical stability in a wide temperature range, great flexibility for structural and compositional manipulating, and environmental friendliness. This thesis is devoted to a theoretical study of the lattice dynamics and thermoelectric properties of materials, like SrRuO3 perovskite and MgAgSb-based materials. Firstly, to obtain insight into the lattice dynamics of the SrRuO3, the phonon-related properties are presented and contributes to rationalize better why many ABO3 perovskites, including metallic compounds, exhibit an orthorhombic ground state. Then the thermoelectric properties of SrRuO3 are investigated by combining first-principles calculations and Boltzmann transport theory, revealing the relationship between the exchange-correlation functionals and the thermoelectric quantities. Furthermore, based on the first-principles calculations, effective model potentials for SrRuO3 are constructed providing access to the finite-temperature properties and phase-transitions. Additionally, the electronic structure and thermoelectric properties of a class of new emerging MgAgSb-based materials, which are promising for room-temperature thermoelectric applications, are also studied and the optimization strategies are proposed for the improvement of thermoelectric performance. [less ▲]

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See detailApproche contingente du design du système d’information comptable dans les PMI tunisiennes : une étude fondée sur les équations structurelles
Ghorbel, Jihene ULg

Doctoral thesis (2015)

Malgré les recherches sur le système d’information comptable dans les PME, les résultats trouvés sont mitigés et contradictoires. Ainsi, nous essayons à travers ce travail de contribuer au débat relatif ... [more ▼]

Malgré les recherches sur le système d’information comptable dans les PME, les résultats trouvés sont mitigés et contradictoires. Ainsi, nous essayons à travers ce travail de contribuer au débat relatif au design du système d’information comptable dans les PMI des pays en voie de développement comme la Tunisie. En effet, le système d'information comptable, considéré comme un facteur de compétitivité des entreprises, fournit aux gestionnaires l'information comptable pertinente pour les aider dans leur prise de décision. Nous nous intéressons à une série de facteurs structurels et comportementaux susceptibles de mieux cerner le design du système d’information comptable. Une étude empirique menée par l'adoption de la technique du questionnaire auprès de 221 entreprises tunisiennes opérant exclusivement dans le secteur industriel montre que le design du système d'information comptable est influencé par plusieurs facteurs contextuels, en utilisant les méthodes des équations structurelles. [less ▲]

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See detailFrom mucosal resistance of larvae to behavioral fever of fingerlings: a journey in the innate immune defenses of common carp against cyprinid herpesvirus 3
Ronsmans, Maygane ULg

Doctoral thesis (2015)

Cyprinid herpesvirus 3 (CyHV-3) is a highly pathogenic virus responsible for a lethal disease in both common and koi carp (Cyprinus carpio). The common carp is one of the most important freshwater species ... [more ▼]

Cyprinid herpesvirus 3 (CyHV-3) is a highly pathogenic virus responsible for a lethal disease in both common and koi carp (Cyprinus carpio). The common carp is one of the most important freshwater species cultivated for human consumption. Its colourful subspecies koi is grown for personal pleasure and exhibitions. Both common and koi carp are economically important and since its description in the late 1990s, the CyHV-3 has caused severe financial losses in these two carp industries worldwide. Because of its economic importance and its numerous original biological properties, CyHV 3 became rapidly an attractive subject for both applied and fundamental research. The objectives of this thesis were to investigate the role of two unrelated innate immune mechanisms of carp in anti-CyHV-3 immunity. The first objective was to determine the role of epidermal mucus as an innate immune barrier against CyHV-3 entry during the early developmental stages of carp. To test this hypothesis, we investigated the sensitivity and the permissivity of carp to CyHV-3 during the early stages of its development. This hypothesis was tested using a recombinant CyHV-3 strain expressing luciferase as a constitutive reporter gene and in vivo bioluminescence imaging system. We demonstrated that carp are sensitive and permissive to CyHV 3 infection since hatching, but that their sensitivity remains relatively low in the two early developmental stages. Similarly to adults, we confirmed that the skin is the main portal of entry for the virus at early stages, and our results stress out the role of epidermal mucus as an innate immune defense of carp against pathogens even and especially at the early stages of development. The results of this study have been published in Veterinary research. The second objective of this thesis consisted to investigate whether carp express behavioral fever when infected by CyHV-3; and if so, what could be the effect of this innate immune reaction on the development of CyHV 3 disease. When infected by pathogens, both endotherms and ectotherms can express a salutary reaction by increasing their body temperature. While in endotherms this reaction is called fever and depends on intrinsic thermogenesis, ectotherms like teleosts can only upregulate their body temperature by moving to warmer places, hence the term behavioral fever. When studying the pathogenesis of CyHV-3, we observed that carp infected at 24°C (the thermal preference of healthy carp) tended to concentrate around the tank heater when it was running. This observation led us to postulate that infected subjects could express behavioral fever in natural environments where temperature gradients exist. Using multi-chamber tanks encompassing a gradient from 24°C to 32°C, we observed that carp infected by CyHV-3 express a salutary behavioral fever that completely suppresses virus induced mortalities. The relatively late onset of behavioral fever with respect to clinical signs, viral replication and cytokine upregulation led us to postulate that this phenomenon could be delayed by the virus to retain its host at a permissive temperature thereby favoring its replication and spreading. As some herpesviruses have been shown to express soluble decoy cytokine receptors, we hypothesized that CyHV-3 could express such receptor(s) able to neutralize putative pyrogenic cytokines produced by the fish. We found that CyHV-3 ORF12 encodes a soluble decoy receptor for carp Tnfα and that this viral protein makes the virus capable of delaying the migration of infected fish to warmer environments. Remarkably, the study of the molecular mechanism through which the virus alters its host’s behavior led to the discovery of the first pyrogenic cytokine in ectotherms (Tnfα). This study is the first to report the ability of a vertebrate virus to alter the behavior of its host through the expression of a single gene. This second study was submitted for publication when this thesis was printed. In conclusion, we investigated two innate immune mechanisms expressed by carp against CyHV 3 infection. The results generated in this thesis bring findings related to several scientific fields such as virology, immunology, animal behavior, evolution, ecology and even animal welfare. [less ▲]

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See detailGestion du risque associé au cycle de vie des méthodes analytiques : Applications aux molécules de faibles poids moléculaires analysées par Spectrométrie de Masse
Hubert, Cédric ULg

Doctoral thesis (2015)

Analytical method lifecycle is composed of several steps, but always starts with a question defining the problem. Analytical method performances are consequently specified by the analyst trough the ... [more ▼]

Analytical method lifecycle is composed of several steps, but always starts with a question defining the problem. Analytical method performances are consequently specified by the analyst trough the definition of the “Analytical Target Profile (ATP)”, as proposed by the regulatory bodies. Subsequent steps (namely the development and validation steps) then take place, followed by routine use of the analytical procedure. In the specific context of the pharmaceutical industry, regulatory authorities have recently imposed the assessment and management of risk throughout the entire product lifecycle. This includes the analytical procedure and consequently its own lifecycle. Working in this context, our concerns were initially focused on the validation step of the method lifecycle. Indeed, the objective of analytical method validation is to demonstrate that this method is suited for quantifying the target analytes with an established and suitable level of accuracy, as defined by the “ATP”. This is sometimes called the “fit-for-future-purpose” concept. In the course of this study we have experimentally confirmed that a decision regarding the validity of a method based on prediction can be achieved by using the “β-expectation tolerance interval” (accuracy profile) as a decision tool. Indeed, it seemed essential to demonstrate the capability of this approach to manage a part of the analytical risk before addressing the development step. Typically this step of the analytical procedure lifecycle is addressed using a “Changing One Separate Factor a Time (COST)” approach (also known as the “Quality-by-Testing (QbT)” approach). By means of a complex case study, and considering validation of the method through the accuracy profile, we have shown that this strategy can lead to a suitable method for assessing the risk of routine use, even where the experimental domain is not examined. In order to consider an experimental domain rather than a set of specific experimental conditions during the development phase, we have evaluated a multivariate approach: the “Quality-by-Design (QbD)” strategy. This strategy allows the definition of a “Design Space (DS)” by means of design of experiments (DoE). This DS, computed considering critical method parameters, allows the analyst to focus on the main objective of an analytical method: obtaining reliable results using a robust method. A comparative study of the QbT versus QbD approach was performed. In the course of this study, the benefits of the QbD strategy in terms of managing the qualitative part of the analytical risk were highlighted. Finally, we have focused our research on the development of a global strategy allowing the unification of the development and validation phases in a single step. With this innovative approach, we are the first to propose a strategy allowing the management of global analytical risk (i.e., both qualitative and quantitative risk). Indeed, we have demonstrated that it is possible to validate an experimental domain by means of the accuracy profile. With this innovative strategy, the DS is no longer simply the place where qualitative performances are obtained, but also the space where quantitative performances of the analytical procedure are assessed and managed. In conclusion, during this thesis, we have confirmed the predictive capabilities of the accuracy profile. Moreover, we have highlighted the benefits of a QbD strategy in terms of risk management. We have also demonstrated that this methodology can be used as a learning tool, facilitating the continuous improvement of the analytical procedure. Furthermore, with the innovative strategy presented during the latter part of this work, we have demonstrated that qualitative and quantitative risk can be assessed and managed throughout the entire analytical method lifecycle. [less ▲]

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See detailEtude de la biodégradation anaérobie des feuilles de Mangifera indica (manguier) et de Manihot utilissima (manioc)
Mambanzulua Ngoma, Philippe ULg

Doctoral thesis (2015)

The population growth of these last two decades leaded to an increase of waste in the City Province of Kinshasa (VPK), capital of the Democratic Republic of Congo. Deprived by an effective management ... [more ▼]

The population growth of these last two decades leaded to an increase of waste in the City Province of Kinshasa (VPK), capital of the Democratic Republic of Congo. Deprived by an effective management system, the VPK produces essentially vegetal wastes that are constituted for the greater part of dead leaves. These wastes bother and pollute the environment. On another point of view, the Kinshasa households meet enormous difficulties for soil fertilization and to collect wood for energy. Its overexploitation of the wood entails the deterioration of the ecosystems and the public health. Therefore in order to contribute to the reduction of all these difficulties simultaneously, the aim of this thesis was to investigate the methanization of these wastes since this technique is relatively simple, fast and non expensive. So, the methanation was performed at 30°C on the leaves of Mangifera indica (MU, mango) and of Manihot utilissima (MI, cassava) that are the most accessible of the VPK. The biochemical methane potentials of the MU and MI leaves demonstrated that the MU leaves were favorable to the methanation due to their low content in bioactive substance (secondary metabolites) and their low C/N ratio. In addition, their digestates would be an effective fertilizing. By contrast, the MI leaves were unfavorable to the methanation since the methanogenesis was inhibited, probably because of their composition rich in carbon and secondary metabolites (lignine, polyphenols, saponines and anthraquinones). However, these metabolites would be beneficial for the methanation in lower contents than 0.3 g/l in the culture medium. The anaerobic co-digestion improved the daily methane yields of these two leaves. The biogas produced with this process would represent about 28 % of the wooden annual domestic consumption and its digestate would cover annually the all agricultural and forest degraded areas. So, the domestic methanation or on site or near the site of waste generation would be favored to avoid the cost of their transport and their industrial treatment. A promising pilot essay has been achieved. [less ▲]

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See detailA Feasibility Study of Direct Injection Spraying Technology for Small Scale Farms: Modeling and Design of A Process Control System
El Aissaoui, Abdellah ULg

Doctoral thesis (2015)

El Aissaoui Abdellah (2015). A feasibility study of direct injection spraying technology for Small Scale Farming: Modeling and design of a process control system. University of Liege-Gembloux Agro-Bio ... [more ▼]

El Aissaoui Abdellah (2015). A feasibility study of direct injection spraying technology for Small Scale Farming: Modeling and design of a process control system. University of Liege-Gembloux Agro-Bio Tech. Belgium. 175p., 11 tabl., 75 fig. The study aims to develop a process controller of direct injection spraying system (DIS) that can fit to carry out precise chemical application using variable rate application based on speed sensing in the context of small scale farming. It has the specific objectives of studying the feasibility of DIS by optimizing the hydraulic system and the process control designs as the main requirements for the best system reactivity and performance. The final design of DIS assessed to implement hydraulic system (hardware) and process controller (software) of a sprayer framework mounted on a rolling chariot propelled by walker operator. A logical approach is used of reviewing the state of art and formulating a specification book to develop a cost effective prototype to eventually adapt DIS expertise to the context of small scale farming. The demarche consists on giving low cost solution of variable rate technology to solve the technical problems related to usage and inefficiency of pesticide application mainly done by portable sprayers. The state of art gives a light on the development process of direct injection spraying technology (DIS) within the scope of precision agriculture progress. It also deals with technical options, advantages and problems related to DIS and control engineering solutions developed for improving spraying application efficiency and safety measures for human and environment. After that we have specified requirements of the researched DIS prototype by referring to existing art of DIS technologies and by diagnosing problems of chemical application in the context of small scale farming. It concerns specifically the technical requirements, setting values and performance of DIS process controller according to the working conditions of intensive cropping in small farming. The materials and methods consist on presenting the approach used for modeling the DIS prototype (splitting the problematic to the two main design aspects of hydraulic system and process control system) and evaluating it in laboratory conditions using simulated velocity data input. The data acquisition system is implemented for assessing the performance of DIS hydraulic and process controller performances. After that, the process controller is implemented in a cost effective electronic kit (box) to be mounted on a small sprayer framework propelled by worker. The hydraulic modeling of DIS served for optimizing the lag transport task as main problem of system reactivity performance and concentration process change. An algorithm is implemented in VB program to assess effect of hydraulic serial boom design (diameter and number of mounted nozzles in serial scheme) on flow dynamic to find compromise between lag transport, mixing ability (turbulence) and friction loss tasks that yield lateral and longitudinal uniformities application of standard boom layout. The modeling results showed lag transport and uniformity of respectively 2 s and 96 % for optimal conventional boom of 6 mm inner diameter having ten tip nozzles (ISO11003, 1.2 L/min~3bars). To solve systematic problem of lateral miss uniformity of serial boom layout (standard scheme), improved parallel boom layout (equidistant tubing lines of 4 mm diameter) is adopted for obtaining an even lag transport between nozzles. The test of parallel boom layout showed even lag transport approximating 1.5 s for ten mounted nozzles. The total response time of DIS is optimally improved to be within 2.5 s by installing electrical pumps close to boom and injecting chemical in suction side to the carrier pump assumed to perform online mixing without use of static mixer. The PID feedback controller is modeled in MATLABTM software. The process is considered as a first order process having a time constant of 0.2 s and a delay transport less than 2 s. Two control strategies of constant carrier flow control (CCFC) and total flow control (TFC) are modeled and implemented for test in laboratory conditions. Both strategies were tested and evaluated on the basis of different solicitations of variable speed input within the range of 0 - 2 m/s as a field working condition of walker operating a rolling sprayer chariot. Finally, on the basis of the results of modeling and experimental assessment, an affordable kit of PLC process controller and PWM modules for actuating carrier pump and metering pump is performed in compact electronic box for potential usage on small sprayer framework to be propelled by walker operator in agricultural field. The controller is based on a PLC microcontroller implemented for carrying out a constant carrier flow rate and a variable chemical injection rate proportionally to the operating speed. The prototype is tested for applying variable rate application using simulated step solicitations within the range of the operator working conditions of 0 - 2 m/s. The study showed the feasibility of implementing a cost effective process controller design for applying variable rate chemical in small farming context. The controller is adaptable for sprayer mounted on wheeled chariot to be propelled by worker assumed to walk at variable velocity. [less ▲]

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See detailStudies of nebulae ejected from massive stars based on observations with the Herschel space observatory
Vamvatira-Nakou, Chloi ULg

Doctoral thesis (2015)

This PhD thesis is devoted to the study of the nebulae ejected by the luminous blue variable (LBV) stars WRAY 15-751 and AG Car as well as by the Wolf-Rayet star WR 124. It is based on new infrared data ... [more ▼]

This PhD thesis is devoted to the study of the nebulae ejected by the luminous blue variable (LBV) stars WRAY 15-751 and AG Car as well as by the Wolf-Rayet star WR 124. It is based on new infrared data taken by the Herschel Space Observatory. These data were complemented by optical data as well as by archived infrared observations. In the first chapter, a general introduction to the subject is given along with a description of the methods used for the data analysis. The three following chapters contain the study of each one of the three nebulae separately. This led to the determination of the physical parameters of the dust and gas components, with the aim to shed a new light on the mass-loss history of the central stars. In particular, the new Herschel infrared images provide a detailed mapping of the nebular dust distribution and of the circumstellar environment at different scales, revealing multiple shells and cavities linked to previous mass-loss events. Moreover, the combination of Herschel photometric results along with archival data was used to model dust with the help of a two-dimensional publicly available radiative transfer code. This model provided us with the dust mass, temperature and composition. The Herschel infrared spectra of all nebulae revealed forbidden nebular emission lines coming not only from an ionized gas region but also from a region where the gas is neutral. Based on the emission line flux measurements, the gas mass and the abundance ratios were estimated. These results, combined with the theoretical models of stellar evolution, were then used to constrain the evolutionary stage of the star at which each nebula was ejected. This study underlines the importance of the Herschel infrared observations for these nebulae. Thanks to them, a better understanding of these objects has been achieved. In particular, a second bigger and fainter dust shell was discovered around WRAY 15-751. In addition, all nebulae were found lying in empty cavities, probably formed during a previous evolutionary phase of their central star. The dust models indicated the necessity to include large grains in all nebulae to reproduce the data. This study showed that for the LBV WRAY 15- 751, with an initial mass of 40 M sun, the nebular ejection took place during a red supergiant phase, while for the LBV AG Car, with an initial stellar mass of 55 M sun, the ejection happened during a cool LBV phase. For the nebula M1-67 around the star WR 124, with an initial mass of 60 M sun, the ejection also took place during a LBV phase. These results are in agreement with the current evolutionary models with little stellar rotation. [less ▲]

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See detailAdvanced numerical framework to simulate Incremental Forming Processes
Velosa De Sena, José ULg

Doctoral thesis (2015)

The framework of the present work supports the numerical analysis of the Single Point Incremental Forming (SPIF) process resorting to a numerical tool based on adaptive remeshing procedure based on the ... [more ▼]

The framework of the present work supports the numerical analysis of the Single Point Incremental Forming (SPIF) process resorting to a numerical tool based on adaptive remeshing procedure based on the FEM. Mainly, this analysis concerns the computation time reduction from the implicit scheme and the adaptation of a solid-shell finite element type chosen, in particular the Reduced Enhanced Solid Shell (RESS). The main focus of its choice was given to the element formulation due to its distinct feature based on arbitrary number of integration points through the thickness direction. As well as the use of only one Enhanced Assumed Strain (EAS) mode. Additionally, the advantages include the use of full constitutive laws and automatic consideration of double-sided contact, once it contains eighth physical nodes. Initially, a comprehensive literature review of the Incremental Sheet Forming (ISF) processes was performed. This review is focused on original contributions regarding recent developments, explanations for the increased formability and on the state of the art in finite elements simulations of SPIF. Following, a description of the numerical formulation behind the numerical tools used throughout this research is presented, summarizing non-linear mechanics topics related with finite element in-house code named LAGAMINE, the elements formulation and constitutive laws. The main purpose of the present work is given to the application of an adaptive remeshing method combined with a solid-shell finite element type in order to improve the computational efficiency using the implicit scheme. The adaptive remeshing strategy is based on the dynamic refinement of the mesh locally in the tool vicinity and following its motion. This request is needed due to the necessity of very refined meshes to simulate accurately the SPIF simulations. An initially mesh refinement solution requires huge computation time and coarse mesh leads to an inconsistent results due to contact issues. Doing so, the adaptive remeshing avoids the initially refinement and subsequently the CPU time can be reduced. The numerical tests carried out are based on benchmark proposals and experiments purposely performed in University of Aveiro, Department of Mechanical engineering, resorting to an innovative prototype SPIF machine. As well, all simulations performed were validated resorting to experimental measurements in order to assess the level of accuracy between the numerical prediction and the experimental measurements. In general, the accuracy and computational efficiency of the results are achieved. [less ▲]

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See detailMultiscale modelling of the hydromechanical behaviour of argillaceous rocks
van den Eijnden, Abraham Pieter ULg

Doctoral thesis (2015)

Feasibility studies for deep geological radioactive waste disposal facilities have led to an increased interest in the geomechanical modelling of its host rock. In France, a potential host rock is the ... [more ▼]

Feasibility studies for deep geological radioactive waste disposal facilities have led to an increased interest in the geomechanical modelling of its host rock. In France, a potential host rock is the Callovo-Oxfordian claystone. The low permeability of this material is of key importance, as the principle of deep geological disposal strongly relies on the sealing capacity of the host formation. The permeability being coupled to the mechanical material state, hydromechanical coupled behaviour of the claystone becomes important when mechanical alterations are induced by gallery excavation in the so-called excavation damaged zone (EDZ). In materials with microstructure such as the Callovo-Oxfordian claystone [Robinet et al., 2012], the macroscopic behaviour has its origin in the interaction of its micromechanical constituents. In addition to the coupling between hydraulic and mechanical behaviour, a coupling between the micro (material microstructure) and macro scale will be made. By means of the development of a framework of computational homogenization for hydromechanical coupling, a doublescale modelling approach is formulated, for which the macroscale constitutive relations are derived from the microscale by homogenization. An existing model for the modelling of hydromechanical coupling based on the distinct de nition of grains and intergranular pore space [Frey, 2010] is adopted and modi ed to enable the application of rst order computational homogenization for obtaining macroscale stress and uid transport responses. This model is used to constitute a periodic representative elementary volume (REV) that allows the representation of the local macroscopic behaviour of the claystone. As a response to deformation loading, the behaviour of the REV represents the numerical equivalent of a constitutive relation at the macroscale. For the required consistent tangent operators, the framework of computational homogenization by static condensation [Kouznetsova et al., 2001] is extended to hydromechanical coupling. The theoretical developments of this extension are implemented in the nite element code Lagamine (Li ege) as an independent constitutive relation. For the modelling of localization of deformation, which in classical FE methods su ers from the well-known mesh dependency, the doublescale approach of hydromechanical coupling is combined with a local second gradient model [Collin et al., 2006] to control the internal length scale of localized deformation. By accepting the periodic boundary conditions as a regularization of the microscale deformation, the use of the multiscale model in combination with the local second gradient model can be used for modelling localization phenomena in HM-coupled settings with material softening. The modelling capacities of the approach are demonstrated by means of simulations of oedometer tests and biaxial compression tests. The approach is demonstrated to be a powerful way to model anisotropy in the mechanical as well as the hydraulic behaviour of the material both in the initial material state and as an e ect of hydromechanical alterations. For the application to the modelling of Callovo-Oxfordian claystone, microstructural REVs are calibrated to geometrical characteristics of the inclusion that form the microstructure under consideration and to macroscale experimental results of the mechanical behaviour. The calibrated constitutive relation is used in the simulation of gallery excavation processes. These computations give a proof of concept of the doublescale assessment of the hydromechanical behaviour of the excavation damaged zones around galleries in the context of nuclear waste disposal. [less ▲]

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See detailGénétique et biologie de la conservation du desman des Pyrénées (Galemys pyrenaicus) en France
Gillet, François ULg

Doctoral thesis (2015)

The Pyrenean desman (Galemys pyrenaicus) is a semi-aquatic mammal endemic to the Iberian Peninsula and the Pyrenees and classified as “vulnerable” by the IUCN. The aims of this PhD thesis, part of a ... [more ▼]

The Pyrenean desman (Galemys pyrenaicus) is a semi-aquatic mammal endemic to the Iberian Peninsula and the Pyrenees and classified as “vulnerable” by the IUCN. The aims of this PhD thesis, part of a National Action Plan, were to improve the knowledge on this species by the development of molecular tools (species identification by sequencing of a fragment of the cytochrome b gene and by RFLP, creation and amplification of polymorphic microsatellites). A genetic structure of three populations associated with low levels of genetic diversity has been evidenced in the French Pyrenees. In addition, the molecular analysis of its diet (COI gene) has allowed to identify its foraging areas and an individual survey on a stretch of river has revealed long distance movements unsuspected before. These results may direct conservation measures for this species. [less ▲]

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See detailEvaluation of the promethazine and acepromazine sedative and hemodynamic effects and norepinephrine reversal of acepromazine induced hemodynamic alterations in the standing horse
De Araujo Pequito, Manuel ULg

Doctoral thesis (2015)

Some phenothiazine derivates, such as acepromazine (ACP), have beneficial properties that could be interesting in equine patients with systemic inflammatory diseases where neutrophil activation and ROS ... [more ▼]

Some phenothiazine derivates, such as acepromazine (ACP), have beneficial properties that could be interesting in equine patients with systemic inflammatory diseases where neutrophil activation and ROS production are implicated. Besides, ACP’s vasodilatatory properties can also be of clinical importance in conditions such as acute laminitis or in anaesthetic protocols. However, the vasodilation induced by ACP is contraindicated in horses suffering from hypotension, a typical complication of systemic inflammatory diseases in horses. The sedative effect of ACP can also have an impact on the correct evaluation of the mental state of a horse in intensive care. Hence, it could be important either to select another phenothiazine derivate with the same beneficial effects as ACP, but with fewer undesirable effects, or to create a medication protocol, in which ACP is associated to another molecule, with the purpose of diminishing its undesired effects. Therefore, this work focused on the comparison of the sedative and peripheral hemodynamic effects of ACP and promethazine (PTZ) as well as on the evaluation of the hemodynamic effects of the administration of ACP followed by a norepinephrine (NOR) infusion in the standing healthy horse. To achieve this objective, 3 different studies were designed. The first one focused on the comparison between ACP and PTZ and the two other ones focused on the study of the association between ACP and NOR. In the first experimental protocol, 9 healthy Warmblood horses randomly received either intravenous ACP at 0.1 mg/kg or PTZ at 0.1, 0.2 or 0.3 mg/kg. A sedation score based on clinical examination was recorded, and systolic arterial blood pressure (SAP) was noninvasively evaluated using a Doppler flow detector at the tail, just before and every 15 minutes until 60 minutes after drug injection. Hemodynamics of the median artery of the left forelimb was studied using Doppler ultrasonography just before and 45 minutes after injection of the drug, which allowed calculation of surface (SURF), diameter (DIAM), and circumference (CIRC) of the vessel, as well as peak systolic velocity (PSV), end diastolic velocity (EDV), mean velocity (MV), volumetric flow (VF), and resistivity index (RI) of the blood flow. In the second experimental protocol, an infusion of NOR at a constant rate of 1 μg/kg/minute for 15 minutes was administered to 5 standing healthy horses 45 minutes (TACP+45) after intravenous injection of ACP at 0.1 mg/kg. Non-invasive SAP and the same hemodynamic parameters than in study 1 were evaluated on the median artery. The SAP was evaluated before, 15, 30, 45 and every 5 minutes during the NOR infusion (TNORa, TNORb, TNORc) from TACP+45 to 60 minutes (TACP+60) after ACP administration and at 5 (TACP+65), 15 (TACP+75), 30 (TACP+90) and 45 (TACP+105) minutes after stopingt the NOR infusion. In the third experimental protocol, 45 minutes after ACP intravenous injection at 0.1 mg/kg, a continuous NOR infusion was performed during 10 minutes at 0.3 μg/kg/min, then 10 minutes at 0.5 μg/kg/min, and finally 10 minutes at 1 μg/kg/min in 5 standing healthy horses. Cardiac output (CO), stroke volume (SV) and systemic vascular resistance (SVR) were measured using lithium dilution (LiDCO). The mean (MAP), systolic and diastolic (DAP) systemic arterial pressures were measured invasively using an anesthesic monitoring system, that also automatically calculated the heart rate (HR). All parameters were measured immediately before ACP administration, 45 minutes after, at the end of each incremental 10 minutes NOR continuous infusion rate (TNOR0.3, TNOR0.5 and TNOR1) and ten minutes after terminating the NOR infusion. Regardless of the used dose, PTZ had lesser sedative and hypotensive effects than ACP at 0.1 mg/kg and did not induce significant variations in SURF, DIAM, CIRC, PSV, EDV, MV, VF, and RI of the studied standing horses. Conversely, the vasodilatory and hypotensive properties of ACP were illustrated by a significant increase in SURF, DIAM, CIRC, PSV, EDV, MV, and VF and a significant reduction of the RI and SAP. Unlike ACP, PTZ did not induce alterations on the morphology of the Doppler waveform. All the ACP-induced hemodynamic alterations, with the exception of PSV and MV were significantly counteracted by the NOR infusion at a constant 1 μg/kg/minute rate, from TNORa to TNORc for EDV, VF, MV and RI, and to TACP+65 for SAP, from TNORb to TACP+90 for CIRC and SURF and to TNORc for DIAM. Besides, although the ACP induced hypotension, no significant changes were observed in the CO, SV, SVR and HR. NOR infusion at incremental doses counteracted the decrease of SAP, from TNOR0.3 to TNOR1, of MAP at TNOR0.3 and TNOR1 and of DAP at TNOR1. After the ending of the infusion, the arterial pressure again dropped significantly, the CO and HR increased non significantly, and the SVR decreased non significantly. PTZ appears to have less sedative and peripheral vasodilator effects than ACP, thus it could be safer than ACP in patients suffering from hypotension. The results also demonstrate that a NOR infusion can reverse ACP’s vasodilatory effects, restoring hemodynamic parameters and blood pressure in horses. The studied NOR infusion proved hence to be useful in horses suffering from vasodilation and hypotension, as it reverted the hemodynamic alterations induced by ACP. [less ▲]

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See detailLa Musique silencieuse de José Muñoz et Carlos Sampayo : déconstruction des normes et lecture émotionnelle
Dejasse, Erwin ULg

Doctoral thesis (2015)

Cette thèse met en lumièredans l'oeuvre de José Muñoz et Carlos Sampayo les mécanismes de déconstruction des normes issues de la bande dessinée de genre fondée sur le principe de l’illusion référentielle ... [more ▼]

Cette thèse met en lumièredans l'oeuvre de José Muñoz et Carlos Sampayo les mécanismes de déconstruction des normes issues de la bande dessinée de genre fondée sur le principe de l’illusion référentielle. Cette entreprise de dislocation des standards graphiques et narratifs vise à substituer à la lecture traditionnelle fondée sur la consommation du récit, une lecture émotionnelle. [less ▲]

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See detailIntégration de la continuité spatiale dans la structure multidimensionnelle d’un entrepôt de données - SOLAP raster
Kasprzyk, Jean-Paul ULg

Doctoral thesis (2015)

Technological advances in recent decades have created a massive acquisition of digital data whose volume grows exponentially. To efficiently extract the information they contain, powerful tools have been ... [more ▼]

Technological advances in recent decades have created a massive acquisition of digital data whose volume grows exponentially. To efficiently extract the information they contain, powerful tools have been developed to collect, store and analyze these data. These tools are gathered in a discipline called “business intelligence”. Among them, data warehouses are responsible for archiving data by structuring them in a multidimensional way (time, space or others). They are called data hypercubes or data cubes when they are limited to three dimensions. Hypercubes can supply OLAP (On Line Analytical Processing) systems that aim at quickly synthesizing information in interactive tables and charts for decision-makers from various fields: marketing, environment, criminology, etc. Thus, users can navigate into hypercubes using OLAP operations such as slicing on dimension members (e.g. data aggregation for the month of January in the time dimension), or drilling into hierarchies (e.g. switching from the “year” level to the “month” level in the time dimension). When OLAP is coupled with spatial analysis techniques supplied by geographic information systems (GIS), a map interface then improves the exploration of data: OLAP operations can be applied to dimensions defined in the geographical space (spatial drilling or spatial slicing). This kind of tool is called SOLAP (Spatial OLAP). SOLAP tools currently available on the market all suffer from the same deficiency: they are unable to represent spatial dimensions (X, Y) in a continuous way. This representation is nevertheless essential for the management of spatially continuous phenomena (temperature, pollution, etc.) but also for visualizing spatially discrete events (product sales, crimes, etc.) while minimizing the Modifiable Areal Unit Problem (MAUP). This kind of visualization is used especially by the police to predict the location of future crimes through hotspot maps which are generated by the Kernel Density Estimation (KDE) method. In the field of GIS, raster data (as opposed to vector data) enable effective representation of spatial continuity through digital georeferenced grids. Whereas current SOLAP tools only consider vector data, our research uses the raster model to integrate spatial continuity into the multidimensional structure of a data warehouse feeding a SOLAP ("raster SOLAP"). Despite its underutilization in the SOLAP literature, the raster model has many similarities with a particular kind of data cube: the MOLAP cube (Multidimensional OLAP). Like a satellite image (raster) representing the two planimetric spatial dimensions and one "spectral band" dimension, a MOLAP cube is a three dimensional array whose cells’ coordinates (similar to raster pixels) enable an efficient indexation of dimensions’ members (describing the analyzed facts). In a first original model that we call "raster cube" we define the bases for a three-dimensional raster SOLAP, starting from the definition of a MOLAP cube. Unlike vector SOLAP - where spatiality is attached to a semantic dimension through pointers to geometries - our model directly integrates spatial dimensions (X, Y) in the multidimensional structure of the data warehouse. With this original feature, any geographical entity (country, building, road, etc.) can be imported on the fly as a member in the analysis of the user, which is hardly possible with conventional vector SOLAP tools. An extension of this SOLAP model, called "raster hypercube", is then developed by entrusting the management of extra non-spatial dimensions to a relational database management system (Relational OLAP or ROLAP). The raster hypercube is then populated by KDE raster fields representing crime densities, which are defined in a continuous space (raster dimensions) through time and crime types (ROLAP dimensions). Our model is able to combine the production of hotspot maps at different scales of analysis with SOLAP navigation operations: slicing on spatial or non-spatial members, and drilling into the hierarchy of spatial or non-spatial dimensions. Our raster hypercube model is validated by an operating prototype which is based on open source tools only. Several datasets are integrated through KDE fields, including crime data from London and Seattle. At the end of our work, the results of a comparative study between raster SOLAP and vector SOLAP demonstrate that hybrid vector/raster SOLAP architectures present the same interest for spatial data as hybrid ROLAP/MOLAP architectures do for purely semantic data (management of detailed hypercubes [less ▲]

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See detailExploiting Interspecific Genetic Variability for Improving Common bean for higher productivity on soils presenting biotic and abiotic stresses
Butare, Louis ULg

Doctoral thesis (2015)

Biotic and abiotic stresses often occur in the same field of rural poor farmer households in tropical countries resulting in heavy losses of common bean yields. To improve resistance of common beans ... [more ▼]

Biotic and abiotic stresses often occur in the same field of rural poor farmer households in tropical countries resulting in heavy losses of common bean yields. To improve resistance of common beans, sensitive Phaseolus vulgaris (SER16) was crossed to resistant P. coccineus (G35346-3Q) to create 94 F5:6 recombinant inbred lines (RILs) of the pedigree SER16♀ x (SER16♀ x G35346-3Q♂). The objectives of this study were to (i) identify potential parents for resistance to Al, drought and Fusarium root rot among 11 bean genotypes, (ii) to evaluate 94 F5:6 Recombinant Inbred Lines (RILs) of the cross SER 16♀ x (SER 16♀ x G35346-3Q♂) both for their resistance to Al and /or drought, (iii) to evaluate RILs for resistance to Fusarium root rot, and (iv) to identify QTL for resistance to these stresses. RILs were characterized in greenhouse for resistance to Al using a hydroponic screening employing a nutrient solution with or without 20 μM Al , to Al-toxic acid soil with high Al (HAl) and low Al (LAl) saturation, to terminal drought simulation with and without progressive soil drying, to combined stresses of Al and terminal drought in 80 cm long soil cylinder system, and to Fusarium root rot using inoculated perlite soil and sand (2:1). Two field studies were also carried on in Colombia under rainfed and irrigated conditions in Palmira, and high Al saturated acid soil in Santander of Quilichao. Our studies confirmed the superiority in Al response of Andean common beans in greenhouse trials compared to Middle American type for several root traits. Each screening method of our Al greenhouse experiments permitted an evaluation of different aspects of root traits. The two parents were virtually equal for tap root elongation rate at 24 h in the 20 μM Al treatment at about 1.4 mm h-1 while progenies ranged from less than 1-1.75 mm h-1. The correlation between leaf area and total root length was highly significant under high Al saturation (r = 0.70***) for HAl-acid soil. Two genotypes (ALB88 and ALB 91) emerged as strong multiple trait lines for the two abiotic stresses. Fusarium root rot induced root growth inhibition as high as 80.8% for the susceptible ALB 5, while resistant RILs (ALB45, ALB41, ALB126, ALB84, ALB49, ALB34, ALB88 and ALB85) didn`t show any inhibition . Seed yield under drought stress conditions was positively associated to 100-seed weight both under irrigated field (r = 0.28**) and rainfed field (r = 0.36***), and negatively associated to days to maturity (DTM) (r = - 0.36***) in field evaluation in Al-toxic acid soil in Quilichao (Colombia). QTLs for important traits including root characteristics under high Al , grain yield and yield components for drought and high Al saturation soil were identified. The use of both soil and hydroponic system, and field could contribute to evaluation of breeding materials to identify genotypes that combine Al resistance with acid soil tolerance, drought and root rot tolerance. [less ▲]

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See detailPerturbations de l'épissage des ARN pré-messagers par les agents chimiothérapeutiques: mécanismes d'action du cisplatine et impact sur la mortalité des cellules cancéreuses
Gabriel, Maude ULg

Doctoral thesis (2015)

L’épissage alternatif est un processus qui concerne plus de 90% des pré-ARN messagers et qui contribue largement à la diversité protéique. Il est régulé par une série de facteurs d’épissage qui se lient ... [more ▼]

L’épissage alternatif est un processus qui concerne plus de 90% des pré-ARN messagers et qui contribue largement à la diversité protéique. Il est régulé par une série de facteurs d’épissage qui se lient sur des séquences situées sur les transcrits primaires. L’activité de ces facteurs d’épissage est régulée, entre autres, par divers signaux externes et voies de signalisation.  Les agents chimiothérapeutiques peuvent altérer la régulation de l’épissage et, ainsi, modifier la séquence d’un grand nombre d’ARN messagers et, éventuellement, la fonction des protéines qui en résultent. Cependant, l’implication de ces mécanismes dans la thérapie anticancéreuse demeure mal connue en termes d’efficacité thérapeutique, de diagnostic, de pronostic, de développement de résistances aux traitements et d’induction d’effets secondaires. L’objectif principal de cette étude est d’évaluer si la régulation de l’épissage par le cisplatine est critique pour son activité anticancéreuse. L’analyse du transcriptome de cellules mammaires cancéreuses traitées avec du cisplatine a permis d’identifier de nombreuses altérations d’épissage induites par la chimiothérapie. Parmi les 700 évènements observés, un grand nombre touche des transcrits impliqués dans le cycle cellulaire et dans la régulation de l’épissage lui-même.   Bien que le cisplatine induise des dommages au niveau de l’ADN, nous avons exclu la participation des membres de la voie des dommages à l’ADN, tels que ATM, ATR, DNA-PK et p53, dans les altérations d’épissage induites par le cisplatine. Les PI3K de class I (p110) et la voie MEK/ERK sont , en revanche, requises.  L’utilisation d’une banque de plus de 50 siRNA ciblant des protéines se liant à l’ARN, en particulier des facteurs d’épissage, nous a permis d’évaluer l’implication de ces facteurs dans les modifications d’épissage observées après le traitement au cisplatine. Il est apparu que la réduction de l’expression de certains facteurs dont SF3A1, RBM39, U2AF1 et snRNP70 mime les effets du cisplatine. A l’inverse, l’inhibition de SRSF4 réprime ces effets.  Par co-immunoprécipitation, nous avons observé un lien physique entre le facteur de transcription c-Jun et les facteurs d’épissage SF3A1 et RBM39. Alors que cette liaison ne semble pas être affectée par le cisplatine, des modifications du statut de phosphorylation de c-Jun ont été observées après traitement au cisplatine. La déplétion de c-Jun et l’inhibition d’AP-1 corrigent en partie l’effet du cisplatine sur l’épissage, suggérant leur implication dans le processus.   Finalement, nous avons montré que la déplétion en SRSF4 réduit la mortalité cellulaire induite par le cisplatine, alors que la déplétion en SF3A1 et RBM39 l’augmente. Ces résultats montrent une corrélation entre épissage et mort cellulaire et suggèrent que la modulation de l’épissage pourrait être utilisée comme thérapie adjuvante afin d’augmenter l’efficacité de la chimiothérapie.   [less ▲]

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See detailWild boar movement ecology across scales: Insights from a population expanding into agroecosystems of Southern Belgium
Morelle, Kevin ULg

Doctoral thesis (2015)

Over the time, ungulates have seen their populations continuously changing under the e ect of direct, i.e. hunting pressure, and indirect, i.e. land-use changes, human activities. Under control until ... [more ▼]

Over the time, ungulates have seen their populations continuously changing under the e ect of direct, i.e. hunting pressure, and indirect, i.e. land-use changes, human activities. Under control until recently, ungulates have progressively adapted to these modi cations and are now able to cope with human-shaped environments, consequently their number and range have greatly and worryingly increased. More particularly, among ungulates species, the wild boar Sus scrofa raises important concerns due to its environmental, economic and social impacts on modern societies. Understanding the ecology of ungulates species and their ability to survive within highly dynamic and seasonal ecosystems, such as agricultural environment, is thus necessary to better mitigate their negative impacts and to sustainably manage growing and expanding populations. Although only recently studied, movement ecology of animal is an important species trait that allows animal to adapt to rapid environmental changes. Considering movement as the resulting interaction of the animal’s internal state, navigation and motion capacity as well as of the e ect of the surrounding environment (“external factors”), provides a clear conceptual framework enabling to study patterns, mechanisms and processes, such as coping with land-use changes. In this thesis, we study the case of an expanding wild boar population in Southern Belgium and consider the movement ecology of the species to understand how wild boar colonize and ourish in agroecosystems. More speci cally, the thesis aims at i) reviewing quantitatively and qualitatively the scienti c literature about wild boar movement ecology, and ii) analyzing the spatial response of wild boar to agroecosystems in terms of movement and habitat selection across three spatial and temporal scales. The literature review highlights that wild boar is the least studied ungulates species in terms of movement ecology.We suggest that this is likely due i) to the relative complexity of tting tracking devices to this species, and ii) to its generalist diet making the species not suitable to test foraging hypotheses. Among existing studies, a large part focuses on the role of external factors (e.g. hunting, landscape features) on movement while others components of the movement ecology framework (internal state, navigation and motion capacity) remain poorly studied. However, when assuming behavioral similarity between wild and domestic boars, experimental studies on captive animals show how wild boar can develop complex movement strategies by using their highly developed cognitive and sensory abilities, and spatial memory. The spatio-temporal analysis suggests a scale-speci c response of wild boar to agricultural habitat. At the intermediate scale (landscape, seasonal), wild boar uses seasonal habitat shift strategies towards agricultural areas, while at broader scale (regional, decades), wild boar avoids this habitat, preferring the forest habitat to spread and extend its occupancy range. This results in a contradiction with our preliminary hypothesis that increased area of cultivations providing cover (maize, rapeseed, cereals) facilitates wild boar population expansion. Furthermore, we show that besides the use of forest habitat, high population density is a major driving factor of the colonization of agroecosystems by wild boar. The ne-scale analysis (home range, daily), highlights the large variety of spatial behaviors (area restricted search, central place foraging, nomadism, dispersing) wild boar is able to use to cope with heterogeneous environments. In terms of management of the species, the results of this thesis suggest that it is required to lower the population density in order to limit the population spread into agroecosystems, not only at the margin of expansion but all over the species’ range. Furthermore, we recommend developing more exible control strategies taking into account both the spatial abilities of the species and the complexity and dynamics of the environment. For example, the creation of a seasonal landscape of fear could be promoted, i.e. reducing attractivity of agricultural lands by increasing risk sensation (e.g. hunting with dogs all along the growing season). However, in our opinion, the success of any management strategy requires rst to tackle the issue of the decreasing number of hunters observed in large part of Europe and to improve communication among the di erent stakeholders (hunting associations, farmers, public administration). Indeed, while ungulates have progressively adapted to human-induced changes, the capacity of humans to adapt to this new human-ungulate relation is questionable. [less ▲]

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See detailBilan bactériologique des mammites dans les troupeaux Zébu Azawak à la station expérimentale sahélienne de Toukounous (Niger) et épidémiologie moléculaire des Staphylococcus aureus isolés entre 2009 et 2012
Issa Ibrahim, Abdoulkarim ULg

Doctoral thesis (2015)

L’élevage est la seconde activité principale après l’agriculture au Niger. Cependant, ce secteur est confronté à d’énormes problèmes, notamment la faible productivité des animaux, le faible investissement ... [more ▼]

L’élevage est la seconde activité principale après l’agriculture au Niger. Cependant, ce secteur est confronté à d’énormes problèmes, notamment la faible productivité des animaux, le faible investissement, des problèmes d’alimentation et d’accès aux points d’eau, et divers problèmes sanitaires récurrents. Depuis l’indépendance du pays en 1960, plusieurs politiques ont été mises en œuvre pour améliorer la productivité des espèces et races domestiques locales. C’est ainsi que, la station expérimentale sahélienne de Toukounous a vu le jour, avec comme objectifs la sélection et la diffusion de la race Zébu Azawak auprès des producteurs ruraux. Les efforts de sélection ont abouti à l’obtention d’un animal standard bien adapté au contexte sahélien avec un niveau de production en lait acceptable. Le bétail laitier à travers le monde souffre énormément des problèmes sanitaires liés aux infections de la glande mammaire. La situation est la même à Toukounous malgré la proximité de services vétérinaires et para-vétérinaires. Cependant, au Niger de manière générale, les données sur les mammites sont rares et très peu de publications scientifiques sont disponibles. Une des possibles explications est la prévalence élevée de mammites sub-cliniques, mais faible de mammites cliniques. La présente étude est dès lors centrée sur les problèmes de mammites au sein de la station sahélienne expérimentale de Toukounous afin d’identifier : (i) les vaches souffrant de mammites cliniques et/ou subcliniques ; (ii) les principales bactéries pathogènes responsables ; et (iii) les virulotypes et profils de résistance aux antibiotiques des souches de Staphylococcus (S.) aureus isolées ; et afin de démontrer l’impact positif de l’application de mesures simples d’hygiène lors de la traite manuelle sur la prévalence de vaches avec mammite. De 2009 à 2012, l’ensemble des vaches en lactation des trois troupeaux de la station, à savoir « élites », « non-élites » et « primipares » ont été testées avec le « California Mastitis Test » (CMT). Ensuite, le lait de tous les quartiers des vaches ayant réagi positivement au test CMT a été prélevé pour réaliser des analyses bactériologiques au Niger. Les espèces bactériennes pré-identifiées au Niger ont ensuite été importées en Belgique (ULg-FMV) afin de procéder à une identification complète par des galeries API®. Les souches confirmées de S. aureus ont par la suite été étudiées pour leurs virulotypes (i) phénotypiquement pour la production de biofilm par mesure de la densité optique après croissance en milieu liquide en plaque de microtitration et pour la synthèse d’une capsule par un test ELISA ; et (ii) génétiquement par PCR ciblant des gènes codant pour différentes propriétés de virulence (adhésines, leucotoxines, entérotoxines, biofilm, et capsule) ; ainsi que pour leurs profils de résistance aux antibiotiques par le test de diffusion en gélose, ou antibiogramme. Ces mêmes souches ont été comparées par leurs empreintes génétiques après « Pulsed Field Gel Electrophoresis » (PFGE), ou pulsotypes, pour en étudier la clonalité au cours des 4 années de l’enquête et dans les 3 troupeaux. Enfin, l’impact de mesures d’hygiène (lavage et désinfection du pis, des trayons et des mains des trayeurs avant et/ou après chaque traite) a été évalué en 2011 et en 2012, en comparant la prévalence de vaches positives au test CMT et l’identité des bactéries isolées en présence ou en absence de ces mesures. Au cours de la première étude en 2009 sur la prévalence des vaches positives au test CMT et l’identité des bactéries mammopathogènes, 104 des 265 vaches (39%) testées dans l’ensemble des 3 troupeaux étaient positives au test CMT, bien qu’aucune mammite clinique n’ait été diagnostiquée. Les analyses bactériologiques ont identifié 55 souches bactériennes: la moitié (51%) appartient au genre Staphylococcus, essentiellement à l’espèce S. aureus (42%). Les autres bactéries identifiées appartiennent à la famille des Enterobacteriaceae (26%) et aux genres Enterococcus (13%), Bacillus (9%) et Acinetobacter (2%). Des résultats similaires ont été obtenus en 2010, 2011 et 2012, bien que les pourcentages respectifs puissent varier selon l’année et le troupeau. Les résultats des tests phénotypiques et génétiques du virulotypage (études 1 et 3) des 122 souches de S. aureus isolées de 2009 à 2012 dans les trois troupeaux n’ont permis d’effectuer aucun regroupement. Par contre, les résultats des empreintes génétiques par PFGE sur ces mêmes souches ont montré qu’elles appartiennent à 16 pulsotypes différents, dont trois sont plus fréquents, A (33%), D (23%) et B (21%). Ces différents pulsotypes se distinguent, dans une certaine mesure, par la présence plus fréquentes des gènes icaA, spa et cap5H dans les souches des pulsotypes A et B ; des gènes cap8H, seg, sei et seb dans celles du pulsotype D ; et du gène luks-PV dans celles des pulsotypes B et D. Pour ce qui concerne les antibiogrammes des mêmes 122 souches (études 1 et 2 + résultats non publiés), des pourcentages élevés de souches résistantes de S. aureus, particulièrement aux -lactamines, ont été relevés. Ainsi, 41% des souches testées étaient résistantes à la pénicilline et 7%, à l’oxacilline. Mais, aucune souche résistante à la méticilline (SARM) ne possède le gène mecA. Les pourcentages de souches résistantes atteignaient 11% pour la tétracycline et la gentamicine, mais restaient inférieurs à 5% pour la clindamycine, l’association trimétoprime-sulfaméthoxazole et l’enrofloxacine. Pour la 4ème étude en 2011 et 2012, les mesures d’hygiène ont été appliquées pendant 6 mois : lavage du pis avant la traite, trempage des trayons avec de la chlorhexidine après la traite, et lavage et désinfection des mains des trayeurs avec une solution antiseptique à base d’hypochlorite de sodium. L’application de ces mesures a diminué de manière statistiquement significative les pourcentages de vaches positives au test CMT en comparaison avec les résultats dans les troupeaux et au cours des années sans application de ces mêmes mesures d’hygiène. En 2012, par exemple, les pourcentages de vaches positives au CMT dans les troupeaux « élite » et « non-élite » ont diminué de 65% et 62%, à 44% et 41% après trois mois d’application, puis à 20% et 24% après 6 mois d’application, respectivement. Par contre, ces mesures d’hygiène n’ont eu aucun effet statistiquement significatif sur les pourcentages relatifs des différents pathogènes identifiés. En conclusion, les mammites bovines sévissent essentiellement sous forme sub-clinique à la station sahélienne de Toukounous. Le genre Staphylococcus et l’espèce S. aureus sont les bactéries mammopathogènes les plus fréquemment identifiées. Les souches de S. aureus appartiennent à différents virulotypes et pulsotypes, bien que trois de ces derniers soient plus fréquents dans les trois troupeaux et au cours des quatre années de l’étude. Ces mêmes souches présentent différents profils de résistance aux antibiotiques, avec près de la moitié d’entre elles résistantes à des membres de la famille de -lactames. Enfin, l’application de mesures d’hygiène (lavage et désinfection du pis, des trayons et des mains des trayeurs) avant et/ou après la traite manuelle permet de réduire la prévalence des vaches positives au test CMT de manière statistiquement significative, mais n’a pas d’influence sur les fréquences relatives des bactéries pathogènes identifiées dans les laits. [less ▲]

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See detailTime-domain simulation of large electric power systems using domain-decomposition and parallel processing methods
Aristidou, Petros ULg

Doctoral thesis (2015)

Dynamic simulation studies are used to analyze the behavior of power systems after a disturbance has occurred. Over the last decades, they have become indispensable to anyone involved in power system ... [more ▼]

Dynamic simulation studies are used to analyze the behavior of power systems after a disturbance has occurred. Over the last decades, they have become indispensable to anyone involved in power system planning, control, operation, and security. Transmission system operators depend on fast and accurate dynamic simulations to train their personnel, analyze large sets of scenarios, assess the security of the network in real-time, and schedule the day ahead operation. In addition, those designing future power systems depend on dynamic simulations to evaluate proposed reinforcements, whether these involve adding new transmission lines, increasing renewable energy sources, or implementing new control schemes. Even though almost all computers are now parallel, power system dynamic simulators are still based on monolithic, circuit-based, single-process algorithms. This is mainly due to legacy code, written in the 80's, that is still today in the core of the most important commercial tools and does not allow them to fully exploit the parallel computational resources of modern computers. In this thesis, two parallel algorithms belonging to the family of Domain Decomposition Methods are developed to tackle the computational complexity of power system dynamic simulations. The first proposed algorithm is focused on accelerating the dynamic simulation of large interconnected systems; while, the second algorithm aims at accelerating dynamic simulations of large combined transmission and distribution systems. Both proposed algorithms employ non-overlapping decomposition schemes to partition the power system model and expose parallelism. Then, “divide-and-conquer” techniques are utilized and adapted to exploit this parallelism. These algorithms allow the full usage of parallel processing resources available in modern, inexpensive, multi-core machines to accelerate the dynamic simulations. In addition, some numerical acceleration techniques are proposed to further speed-up the parallel simulations with little or no impact on accuracy. All the techniques proposed and developed in this thesis have been thoroughly tested on academic systems, a large real-life system, and a realistic system representative of the continental European synchronous grid. The investigations were performed on a large multi-core machine, set up for the needs of this work, as well as on two multi-core laptops computers. [less ▲]

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See detailHölder Continuity and Wavelets
Simons, Laurent ULg

Doctoral thesis (2015)

There exist a lot of continuous nowhere differentiable functions, but these functions do not have the same irregularity. Hölder continuity, and more precisely Hölder exponent, allow to quantify this ... [more ▼]

There exist a lot of continuous nowhere differentiable functions, but these functions do not have the same irregularity. Hölder continuity, and more precisely Hölder exponent, allow to quantify this irregularity. If the Hölder exponent of a function takes several values, the function is said multifractal. In the first part of this thesis, we study in details the regularity and the multifractality of some functions: the Darboux function, the Cantor bijection and a generalization of the Riemann function. The theory of wavelets notably provides a tool to investigate the Hölder continuity of a function. Wavelets also take part in other contexts. In the second part of this thesis, we consider a nonstationary version of the classical theory of wavelets. More precisely, we study the nonstationary orthonormal bases of wavelets and their construction from a nonstationary multiresolution analysis. We also present the nonstationary continuous wavelet transform. For some irregular functions, it is difficult to determine its Hölder exponent at each point. In order to get some information about this one, new function spaces based on wavelet leaders have been introduced. In the third and last part of this thesis, we present these new spaces and their first properties. We also define a natural topology on them and we study some properties. [less ▲]

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