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See detailA Frequency-domain Approach to Subspace Identification of Nonlinear Systems, Application to Aerospace Structures
Noël, Jean-Philippe ULg

Doctoral thesis (2014)

The construction of mathematical models from experimental data is an essential step in the design process of engineering systems. The different tasks involved in this activity, from the measurement and ... [more ▼]

The construction of mathematical models from experimental data is an essential step in the design process of engineering systems. The different tasks involved in this activity, from the measurement and processing of data to the validation of the model, fall into the general field of system identification. In structural dynamics, the theoretical and experimental aspects of linear system identification have been successfully addressed since the early seventies, and mature analytical, computational and testing tools have emerged. Nonlinear system identification of vibrating structures has also enjoyed significant advances during the past few years. However, the common practice in industry is to ignore nonlinearities, arguably because their analysis is still regarded as impractical. The objective of this doctoral thesis is precisely to progress towards the development of a practical system identification methodology dedicated to real-life nonlinear structures. The first facet of the thesis is to introduce a nonlinear generalisation in the frequency domain of the so-called subspace identification methods. The proposed frequency-domain nonlinear subspace identification (FNSI) approach yields accurate models of large-scale systems comprising strong nonlinearities, closely-spaced modes and high damping. Because it can also estimate a large number of parameters while maintaining an acceptable computational burden, the second facet of this research is to investigate the utilisation of cubic splines as a very flexible means to model complex nonlinearities. Finally, the third facet of the present work is to derive nonlinear models with optimal statistical properties in the presence of measurement noise. This is achieved by embedding the FNSI method into the maximum likelihood identification framework. The scope of the identification and modelling tools developed in this thesis encompasses nonlinear structural systems originating from the various areas of vibration engineering, including the aerospace, mechanical or civil fields, amongst others. Throughout the dissertation, these tools are illustrated using numerical and experimental structures of increasing complexity, mainly related to aerospace applications. [less ▲]

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See detailLe rôle du commerce frontalier des produits alimentaires avec le Rwanda dans l'approvisionnement des ménages de la ville de Bukavu (Province du Sud-Kivu)
Vwima Ngezirabona, Stany ULg

Doctoral thesis (2014)

This thesis aims at highlighting the importance of food supply from the Rusizi District (Rwanda) in the food security of the city Bukavu (Democratic Republic of Congo). Due to the informal nature of this ... [more ▼]

This thesis aims at highlighting the importance of food supply from the Rusizi District (Rwanda) in the food security of the city Bukavu (Democratic Republic of Congo). Due to the informal nature of this supply, it was necessary to characterize its magnitude, drivers, and consequences as well as to develop policies that are likely to improve this supply and facilitate regional integration. The fieldwork consisted of two series of investigations. The first series of data collection included scoring the flow of food supply from Rusizi District during three months and for each of the food supply axes of Bukavu city. Secondly, a questionnaire was administered to a sample of 233 households, wherein 76 consuming households and 157 reselling households. Results from the scoring exercise show that 2,021 households on average cross both borders (Rusizi 1 and Ruzizi 2) for their food supply daily. A total of 661 of these households (about 32.7%) are direct food consumers and 1,360 households (about 67.3%) are food resellers. Excepted for cassava (which is a traditional staple of South Kivu), plantains (because of conservation problem, much more coming from within the province), and beans (much more from North Kivu), other major food products are imported from Ruzizi district in Rwanda. In this regard, the dependency ratios towards Rwanda remain much higher for products such as maize (66%), potatoes (82%), sorghum (73%), groundnut (69%), sweet potato (98%), rice (70%), and beef and pork meat (85%). With such dependency ratios, Bukavu is a major food market of the Rusizi District (Rwanda) food products. This is however far from being confirmed by official import statistics of the Congolese Control Office (CC0) which, except for rice, underestimates the border trade for a large portion of food commodities flows. The commodities analyzed provide the population of the city of Bukavu 1027 kcal per person per day from which 593.5 kcal, 338.9 kcal and 92.4 kcal are provided by products respectively from Rwanda, North-Kivu and South-Kivu. The calories consumed in the city of Bukavu are mainly of vegetable origin dominated by maize (563.1 kcal), cassava (120 kcal) and beans (167.1 kcal), which play a strategic role given their importance in the food habits of Bukavu. The significant flows of food supplies from Rusizi district are a major contribution to the livelihood of thousands of families in the city of Bukavu. It emerges that all products supplied from Rusizi district by reselling households generate positive return per month demonstrating a positive remuneration not only for the invested capital, but also for the time and effort invested in the activity (average 5.67 hours). More than 68 % of reselling households claim are satisfied with the result of this activity and allocate the generated income mainly to cover subsistence needs. In this sense, the economic impact of border trade on incomes of reselling households is a reality. The analysis of budgets of consuming households shows that 69.1% of food expenditure and 48.8% of total expenditure of consuming households cross the border. The significant impact of food supplies from the Rusizi district on reducing households’ income poverty, reflects the interests of border trade which only reinforces the structural and relative decline of the agricultural sector in South Kivu already confronted to various problems. The free trade policy advocated by a large number of sub-regional and regional communities such as CEPGL and COMESA will make the Rusizi originating food supply of Bukavu more efficient, but it remains a short-term solution of food security of the city and the province in general. In the long term, it would be better to stimulate the production and promote local food trade. To achieve this, investments need to be channeled to the agricultural sector. It is at this price that the agricultural sector in South-Kivu can be revived and reach the threshold of self-sufficiency, and even create a surplus for export. Admittedly, this solution then poses the problem of reconversion of consuming households and sellers-households that we should rethink from the outset. [less ▲]

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See detailIncertitudes liées à la modélisation agro-environnementale en vue de développer des outils d'aide à la décision
Dumont, Benjamin ULg

Doctoral thesis (2014)

The European Nitrates Directive 91/6/76/EEC aims to ensure water quality by preventing pollution of surface and groundwater induced by nitrates originating from agricultural sources and by promoting ... [more ▼]

The European Nitrates Directive 91/6/76/EEC aims to ensure water quality by preventing pollution of surface and groundwater induced by nitrates originating from agricultural sources and by promoting agronomical good practices. While the implementation of this Directive seems effective, it appears however that the use of nitrogen has still increased by 6% over the last four years in 27 European countries. Furthermore, agricultural sources would be still at the origin of 50% of the total amount of nitrogen discharged into surface waters (http://ec.europa.eu/environment/water/water-nitrates/index_en.html). In Wallonia (Belgium), the Nitrates Directive has been transposed under the Sustainable Nitrogen Management in Agriculture Program (PGDA). Launched in 2002, it involves different sets of actions, like rules definitions concerning fertilizers application, specific and appropriate crop management in vulnerable areas, the control of potentially leachable nitrogen (APL) levels in soils, etc. This is the global context in which lies the present thesis. The main aim is to optimise the nitrogen fertiliser practices to ensure that the needs of a winter wheat culture (Triticum aestivum L.) could be met while reducing the environmental pressure. It relies on the use of crop models, which describe the growth and the development of a culture interacting with its environment, namely the soil and the atmosphere. The major difficulty while working with crop models and model-based decision support tools lies in the fact that different sources of uncertainties have an impact on the modelled phenomena. Indeed, crop models are constituted by a consequent number of differential non-linear equations, involving a lot of parameters which need to be determined as accurately as possible in order to match as close as possible observed sequences of measurements. The first source of uncertainty is thus constituted by the parameters definition. Once the model has been correctly and robustly calibrated it can be used to perform predictions. However, in an agronomical context, the time-delay between sowing and harvest is consequent. As the end-season yield is often the expected output, the uncertainty linked to the non-knowledge of the future implies for the modeller to refer to different hypothesis concerning upcoming climatic scenarios. Finally, moving from models to decision systems dealing with N management involves a last source of uncertainty. Indeed the main problem is that the impact of a given practice is delayed in time from its realisation. In addition to the uncertainty linked to climatic projections themselves, it is highly important to consider the interactions between the practices and the climate. Furthermore, in a decision-making process, it could be highly relevant to know the uncertainty's estimation that could be tolerated on the decision.. Therefore, the present thesis aims to study these different sources of uncertainty in order to design an efficient decision support system. It is divided into five parts. In the first part, a Bayesian sampling algorithm, known as DREAM (DiffeRential Evolution Adaptative Metropolis) will be presented. It was successfully coupled with the STICS soil-crop model used in this study. The a posteriori probability density function of many parameters was sampled in order to improve the simulations of the growth of a winter wheat culture (Triticum aestivum L.). The DREAM algorithm offers different advantages in comparison to usual methods. Among these, it is possible to study i) the most probable a posteriori parameters distributions, ii) the parameters correlations, and iii) the uncertainties impacted on model outputs. Furthermore, a new version of the likelihood function was proposed, making an explicit use of the coefficient of variation. Results showed that it allowed the noise existing on measurements to be considered, but also the heteroscedasticity phenomenon usually encountered in biological growth processes. In parallel, assimilation data is another way to improve models simulations. These techniques allow considering measurements performed in real-time (e.g. remote measures of LAI or soil water content) in order to correct and adjust the possible drift of model simulations. In particular, a recently developed algorithm, known as variational filter, was evaluated. Its superiority, both in term of state variables simulations improvement and parameter resampling, was demonstrated. The third part of the research focuses on the real-time end season yield prediction. It involves building climate matrix ensembles, combining different time ranges of projected mean data and real measured weather originating from the historical records. As the crop growing season progresses, the effects of real monitored data plays a greater role and the prediction reliability increases. Our results demonstrated that a reliable predictive delay of 3-4 weeks before harvest could be obtained. Finally, using real-time data acquired with a micrometeorological station enabled to (i) predict, daily, potential yield at the local level, (ii) detect stress occurrence, and (iii) quantify yield losses (or gains). Being based on projected seasonal norms, this methodology is in opposition to another technique that consists to offer a panel of solution for what concerns the future. Such probabilistic technique relies on the use of stochastic weather generator (LARS-WG in this case). However, in the fourth part of this thesis, on the basis of the convergence in law theorem, it was demonstrated that in 90% of the climatic situations, both approaches were equivalent, exhibiting RRMSE and normalised deviation criteria inferior to 10%. Furthermore the two approaches offered similar predictive delay-time. The main difference between techniques lies in the finality. The first allows to quickly simulate the remaining yield potential, while the second aims to quantify the uncertainty level associated to the predictions. In the fifth and last part of this thesis, in order to quantify the uncertainty level associated to different modalities of N applications, the STICS model answers were studied under stochastic climatic realisations. It was demonstrated that, if no N was applied, under our temperate climatic conditions, the yield distribution could be considered as normal. However, with increasing N practices, the asymmetry level was found itself increasing. As soon as N was applied, not only were the yields higher, but also was the probability to achieve yields that were at least superior to the mean of the distribution. This undoubtedly reduced the risk for the farmer to achieve low yields levels. To summary all the researches conducted in this thesis, a N strategic decision support system was developed. In a general way, for what concerns the Hesbaye Region, the superiority of three fractions N protocols was demonstrated. In addition, the three rates fertilisation management based on the systematic applications of 60 kgN.ha-1 at tillering and stem extension stages and offering the possibility to adapt the flag-leaf fraction in real-time appeared as an optimal strategy. Within this tool, the uncertainty associated to climatic variability could be finely characterised, and the risk encountered by the farmer was quantified for different investigated practices. But far more important, it was demonstrated that N management could be optimised in real-time. In a general way, the research should be pursued by studying more fundamentally and systematically a wide range of different agro-environmental situations. In particular, it would be interesting to study of the Genotype × Environment × Cultural practices interactions to ensure food security in a climatic changing world. [less ▲]

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See detailLa relation partenariale sous l'angle de la confiance : de l'autonomisation à la capacitation
Remy, Céline ULg

Doctoral thesis (2014)

La thèse a pour objet d’étude les partenariats publics-privés (PPP) dans le champ de l’emploi et, plus précisément, la relation partenariale entre les services publics de l’emploi (SPE) et les opérateurs ... [more ▼]

La thèse a pour objet d’étude les partenariats publics-privés (PPP) dans le champ de l’emploi et, plus précisément, la relation partenariale entre les services publics de l’emploi (SPE) et les opérateurs privés d’insertion socioprofessionnelle (marchands et non-marchands). Trois questions de recherche nous intéressent tout particulièrement : 1) comment la relation partenariale se construit-elle ? 2) comment est-elle vécue par les partenaires ? et, 3) que produit-elle comme effet(s) en termes d’autonomisation et de capacitation pour les parties-prenantes ? L’objectif de la thèse consiste à comprendre les processus d’autonomisation et de capacitation d’un partenariat pour voir dans quelle mesure un lien existe entre ceux-ci. Pour ce faire, trois terrains de recherche ont été réalisés au sein de SPE, dont deux en Belgique (Actiris et le Forem) et un en Suisse (Office Cantonal pour l’Emploi). Les données empiriques sont récoltées à partir d’un travail intense d’observation des pratiques des acteurs et la réalisation d’entretiens semi-directifs, de type compréhensif, avec les agents des SPE et les opérateurs privés (N= 83). Les données sont analysées à l’aune des théories de la justification, d’une sociologie de la confiance et d’une sociologie de la capacitation. Nos analyses révèlent la cartographie cognitive des agents des SPE lors du processus de sélection des opérateurs privés pour l’établissement de PPP. Par l’étude approfondie de la relation partenariale, nous observons un impact de la dynamique interne du partenariat sur l’autonomisation de celui-ci. Par ailleurs, nous remarquons que les variables de contexte – à travers les techniques de génération et de gestion du PPP – ont, par des combinaisons spécifiques, une influence sur l’autonomisation et la capacitation du partenariat. Contrairement à notre hypothèse initiale - selon laquelle les processus d'autonomisation et de capacitation se développent de façon parallèle - il apparaît dans notre analyse que ceux-ci ne sont pas liés de façon automatique. En effet, ils peuvent être inversément proportionnels au sens où un partenariat autonomisé peut être peu capacitant ou, à l’inverse, peu autonomisé et fortement capacitant pour les membres qui le composent. [less ▲]

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See detailEtude du mécanisme d’activation du zymogène proDer p 6 de l’acarien Dermatophagoides pteronyssinus et du rôle de son propeptide dans l’inhibition, le repliement et l’immunogénicité de l’allergène
Herman, Julie ULg

Doctoral thesis (2014)

L’allergie aux acariens touche 20 à 30% de la population occidentale. L’allergène Der p 6 de l’acarien Dermatophagoides pteronyssinus est une protéase à sérine active de la famille de la chymotrypsine ... [more ▼]

L’allergie aux acariens touche 20 à 30% de la population occidentale. L’allergène Der p 6 de l’acarien Dermatophagoides pteronyssinus est une protéase à sérine active de la famille de la chymotrypsine. Son activité protéase pourrait être impliquée dans l’augmentation de la réponse allergique chez les patients atopiques. Der p 6 est synthétisée chez l’acarien sous la forme d’une pré-pro-protéine constituée d’un peptide signal (17 résidus) et d’un zymogène présentant un propeptide de 34 résidus en amont du domaine protéase de 231 résidus. Après avoir produit en Pichia pastoris et purifié le zymogène proDer p 6, son mécanisme d’activation a été élucidé dans la première partie de ce travail. Il s’agit d’un mécanisme tout à fait particulier, propre à l’acarien lors duquel la protéase à cystéine active Der p 1 mature proDer p 6. Un mécanisme similaire avait pu être montré pour le trypsinogène proDer p 3. Pour la première fois, la forme recombinante de Der p 6 a pu être produite. Celle-ci présente la même activité que la protéase naturelle présente dans les extraits d’acariens. Dans la seconde partie de ce travail, Der p 6 ainsi que Der p 1 ont pu être mis en évidence au niveau du tube digestif de l’acarien D. pteronyssinus, ce qui confirme que ces protéases sont impliquées dans la digestion de l’acarien. La protéase Der p 1 est présente au niveau de l’intestin moyen, tandis que Der p 6 est présente dans le gros intestin. Dans cette dernière partie de l’intestin, les protéases sont co-localisées, ce qui indique que le procédé de maturation observé in vitro pourrait se dérouler in vivo. Dans la troisième partie de ce travail, nous avons montré que le propeptide de proDer p 6 est un inhibiteur spécifique de la protéase Der p 6. Le propeptide est donc impliqué dans le contrôle spatio-temporel de l’activation de la protéase. Lors de ce processus, les quatre résidus en amont du site de clivage (résidus P4 à P1) sont nécessaires et suffisants pour la reconnaissance et le clivage du propeptide par Der p 1. Comme cela a été montré pour Der p 3, aucun rôle du propeptide dans le repliement de la protéase Der p 6 n’a pu être mis en évidence. Dans la dernière partie, une étude préliminaire de l’allergénicité de Der p 6 a été réalisée. Der p 6 serait un allergène mineur avec une prévalence d’environ 30 %. Les études par ELISA et activation des basophiles, réalisées avec les formes naturelles, recombinantes ou inactives de Der p 6 indiquent que ces différentes formes pourraient être utilisées en diagnostic. Des prédictions bioinformatiques ont également été réalisées afin de déterminer les épitopes B de Der p 6. [less ▲]

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See detailChimie Intégrative dédiée aux morphosynthèses de matériaux composites multi-échelles et étude de leurs applications en photoluminescence, photocatalyse et photovoltaïque
Kinadjian, Natacha ULg

Doctoral thesis (2014)

The shaping of functional materials and the control of their texture at all length scales are sine qua non conditions for the improvement of current systems. This PhD project consists in creating complex ... [more ▼]

The shaping of functional materials and the control of their texture at all length scales are sine qua non conditions for the improvement of current systems. This PhD project consists in creating complex solid architectures using interdisciplinary methods such as sol-gel chemistry or complex fluids physics. Therefore, it is possible to synthesize Titanium Dioxide macroscopic fibers or films which possess a hierarchical porosity. This organization allows the optimization of the matter transport (liquid/gaz) for air depollution application (photocatalysis) or dye-sensitized solar cells. In another project, we were able to control the alignment of zinc oxide nanorods within a macroscopic fiber. This alignment provides to the fiber an anisotropic photoluminescence behavior which can be useful for switching devices application. Finally, we synthesized anisotropic particles and nano-sheets of polypyrrole (conducting polymer) in order to obtain smooth thin films presenting interesting electrical properties. The objective was to use them as electrolyte and/or electrode in dye-sensitized solar cells. [less ▲]

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See detailL'ordinaire du contentieux administratif : Analyse du processus décisionnel au Conseil d'Etat belge francophone
Colemans, Julie ULg

Doctoral thesis (2014)

La thèse porte sur le processus décisionnel au Conseil d’Etat belge. Le raisonnement juridique pratique a été étudié à travers les activités concrètes que les auditeurs et conseillers accomplissent tout ... [more ▼]

La thèse porte sur le processus décisionnel au Conseil d’Etat belge. Le raisonnement juridique pratique a été étudié à travers les activités concrètes que les auditeurs et conseillers accomplissent tout au long du parcours du dossier. De cette manière, le raisonnement juridique n’est pas appréhendé comme une opération logique de la pensée mais comme un accomplissement pratique qui se déploient dans un horizon de sens partagé incarné par le concept de « raisonnable ». [less ▲]

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See detailDynamique et composition des atmosphères supérieures de Mars et Vénus observées par les spectrographes ultraviolets à bord de Mars Express et Vénus Express
Stiepen, Arnaud ULg

Doctoral thesis (2014)

Venus has a dense CO2-dominated atmosphere. Above 50 km, the atmospheric circulation is composed of two dominants patterns: the Retrograde Superrotating Zonal (RSZ) circulation up to 65 km and the ... [more ▼]

Venus has a dense CO2-dominated atmosphere. Above 50 km, the atmospheric circulation is composed of two dominants patterns: the Retrograde Superrotating Zonal (RSZ) circulation up to 65 km and the subsolar to antisolar (SSAS) circulation beyond 120 km. The SSAS is caused by the temperature gradient between the day and the night hemispheres and it generates a global flow from the dayside to the nightside. Between 65 and 120 km, the circulation is complex as it is the superposition of the two main components. I have used the nightglow emitted by the NO* molecule (180-300 nm) produced by recombination of N(4S) and O(3P) atoms. These atoms are created by photodissociation of N2 and CO2 molecules on the dayside and carried to the nightside by the SSAS circulation. I analyze the full set of measurements of the NO δ and γ bands measured by the SPICAV instrument on board the ESA Venus Express spacecraft. I discuss the altitude and brightness of the emission peak (60 kR at 115 km) and show that the emission profile exhibits a secondary peak in ~10% of the cases. This additional peak is probably caused by upward-moving gravity waves propagating from below. I have developed an inversion method of the observed limb profiles to compare the results with a chemical-diffusive model of the atmosphere of Venus and constrain the vertical fluxes of N and O. On the basis of an extended statistical analysis, I characterize the presence of a bright spot of the nightglow of NO shifted from the antisolar point and located around 0230LT, 10°S. I use the vast SPICAV airglow database to statistically demonstrate that the NO nightglow is highly variable, both temporally and spatially. Mars experiences seasons as its rotation axis is inclined from its spin axis. Its upper atmospheric dynamics is dominated by summer-to-winter global transport. I study the upper atmosphere of Mars using nightglow observations performed by the SPICAM instrument on board ESA’s Mars Express spacecraft. I analyze the δ and γ bands of molecule NO in the nightside mesosphere to confirm, on statistical basis, the peak brightness and altitude of the NO UV emission (5 kR at 72 km). I show that the NO nightglow is located following the relation Latitude = -80xsin(Solar Longitude), in agreement with results based on stellar occultations and from the LMD model, which simulates the photochemistry and dynamics of the Mars atmosphere. I have performed a detailed study of the CO Cameron band (170 to 270 nm) and CO2+ doublet (290 nm) dayglow. I have developed a method to deduce the temperature profile around 150 km, an important study as the distribution of the temperature in the Mars atmosphere is poorly known. I showed that the temperature at high altitude is only weakly correlated with the solar EUV flux. This result suggests that the variability of the upper atmosphere may include internal processes. Comparisons with the Mars Global Ionosphere Thermosphere Model show that the model can reproduce the observation for high solar conditions but predicts lower temperature for low to moderate solar conditions. Further study will therefore be necessary to identify and understand the mechanisms that govern the temperature variability. [less ▲]

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See detailMigration, mémoire, patrimonialisation. Étude empirique de la mémoire collective de l'exil et de l'immigration espagnols en Belgique
Molina Marmol, Maïté ULg

Doctoral thesis (2014)

Dans le prolongement de premiers travaux de recherche, la thèse de doctorat a été consacrée à l’exploration du croisement, présenté comme heuristiquement enrichissant, entre mémoire et migration, en ... [more ▼]

Dans le prolongement de premiers travaux de recherche, la thèse de doctorat a été consacrée à l’exploration du croisement, présenté comme heuristiquement enrichissant, entre mémoire et migration, en partant de l’étude empirique de la présence espagnole en Belgique. Se proposant de comparer la mémoire collective de la vague migratoire de l’exil (centré autour de l’expérience des Niños de la Guerra qui en ont composé les effectifs principaux en Belgique) et de l’immigration dite « économique » (soit d’après-guerre), la recherche s’est basée sur des terrains réalisés à Bruxelles et Liège, en tant que deux plus importants points de concentration de la population espagnole en Belgique ayant vu se sédimenter sur leur territoire les trois premières vagues migratoires. En dehors de l’évidence de logiques migratoires différentes, l’intuition d’une reconnaissance sociale inégale – au profit de l’exil –, malgré certains référents symboliques communs – dont la guerre d’Espagne –, a motivé le choix d’une approche comparative. Au niveau théorique, après avoir mêlé les apports de la sociologie de la mémoire à la perspective historienne sur ce phénomène, il s’agissait de s’émanciper du cadre des groupes politiques, se prêtant particulièrement bien à une analyse en terme de mémoire collective dans une perspective halbwachsienne et de compléter cette dernière d’une vision anthropologique davantage attentive et sensible au caractère volatile des phénomènes mémoriels et à leur imprégnation au sein de certaines pratiques quotidiennes – ce que Joël Candau a conceptualisé sous la notion de « protomémoire » . Construite autour de trois grandes parties dont l’intersection constituerait le lieu de déploiement d’une mémoire collective, la thèse envisage tour à tour la « mémoire sur les migrants » (soit le contexte des états d’origine et d’accueil et les initiatives publiques de différents ordres), « par les migrants » (à savoir les actions des associations et des entrepreneurs de mémoire) et « des migrants » (la mémoire vive). D’emblée il s’est agi d’inscrire pleinement dans l’analyse l’invention du terrain et d’une perspective théorique, la recherche se basant sur un mouvement de déconstruction/reconstruction dès la définition de ses « objets ». Par ailleurs, la réflexion méthodologique a constitué l’occasion de revenir sur les spécificités de la place et du rôle du chercheur dans la situation d’une « ethnographie indigène ». Si l’analyse a permis de conclure à l’existence d’une mémoire collective de l’exil des Niños en Belgique, elle a ouvert la question non seulement du contenu mais de l’existence, et plus particulièrement des conditions de possibilité d’une mémoire collective de l’immigration. L’analyse des discours publics, des initiatives communautaires et des entretiens individuels a conduit à poser l’hypothèse de sa localisation au croisement des mémoires militantes, ouvrières et ethniques. Le cas espagnol a bien constitué dans ce cadre un terrain d’élection, de par l’ambiguïté structurelle entre « exil politique » et « immigration économique » qui a d’emblée été posée et qui ne s’est pas avéré sans répercussions en termes mémoriels – notamment en termes d’établissement d’un « espace du dicible ». Mais si tant les dimensions ethnique et militante de l’expérience migratoire et de sa mémoire peuvent être qualifiées de « collectives », il reste que situer à leur intersection une mémoire collective de l’immigration constituerait une opération de réduction, évacuant toute une part de cette mémoire, celle la plus difficilement appréhendable, notamment portée par les femmes et se jouant dans la labilité des gestes quotidiens et des espaces de vie. [less ▲]

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See detailModélisation 2D par éléments finis du contact : effet de l’utilisation de méthodes de représentation des surfaces présentant un ordre de continuité élevé et méthodes permettant de passer le patch test
Nguyen, Duc Tue ULg

Doctoral thesis (2014)

Ce travail de thèse concerne la mécanique numérique du contact entre les solides déformables. La simulation numérique des problèmes de contact comporte de nombreuses difficultés notamment dans un contexte ... [more ▼]

Ce travail de thèse concerne la mécanique numérique du contact entre les solides déformables. La simulation numérique des problèmes de contact comporte de nombreuses difficultés notamment dans un contexte de grands déplacements et de grandes déformations. Le but de ce travail est d’analyser l’influence de l’ordre de continuité élevé de la représentation de surface et de développer une méthode pour passer le patch test, à savoir qu’un élément passe le patch test si il transmet correctement des pressions de contact entre deux surfaces. Pour la discrétisation des éléments finis, l'interface de contact est représentée par une série de lignes et de courbes à continuité C0. Par conséquent, lors du passage du nœud esclave entre deux segments maîtres adjacents, il peut arriver avoir une discontinuité de la direction du vecteur normal. Cette situation peut mener à des problèmes de convergence de l'algorithme de résolution. Pour éviter ce problème, l’approche proposée consiste à développer les représentations de surface maître à ordre de continuité C1 ou C2 pour les éléments nœud-surface linéaires et quadratiques. Les éléments nœud-surface ne passent pas le patch test. Plus récemment, un élément linéaire utilisant la méthode des nœuds esclaves virtuels pour Passer le Patch Test (PPT) a été proposée dans la littérature. Cependant, cet élément est à ordre de continuité C0 et peut donner des grandes oscillations de la pression de contact à cause des pénétrations initiales des nœuds esclaves virtuels qui sont les pénétrations des nœuds esclaves virtuels dans la surface maître à l’état initial. Pour tenter de surmonter cette difficulté, une nouvelle approche repose sur un élément linéaire utilisant la méthode PPT et la représentation de surface à ordre de continuité C1 pour la surface maître et pour la surface esclave. L’élément quadratique nœud-surface donne des oscillations de pression de contact à cause de la distribution non-uniforme des forces nodales. Afin de résoudre ce problème, la méthode PPT est développée pour l’élément quadratique. [less ▲]

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See detailDétermination de la broyabilité des plaquettes et des pellets de bois
Temmerman, Michaël ULg

Doctoral thesis (2014)

The literature about energy requirements for product milling in mining industry shows the subject has been, and still is, considered by numerous authors. Several milling theories have been proposed for ... [more ▼]

The literature about energy requirements for product milling in mining industry shows the subject has been, and still is, considered by numerous authors. Several milling theories have been proposed for these industries, especially concerning ores milling. Biomass milling, prior to its use as biofuel, has been, by far, less studied. Nevertheless, few measurements are available about energy needed for milling of particular biomass, in particular systems. But studies taking into account enough characteristic of the milled material (origin, moisture content, particle size distribution) are scarce. Moreover, the methods used to measure these properties are generally different. In consequence, nearly none biomass milling model has been proposed. Concerning wood densified product (pellets & briquettes) apparently no data are available yet. . This study draws upon the milling theories developed for the ore processing industry (Von Rittinger, Kick and Bond theories which have been merged by Charles and Hukki) in order to define a method for characterizing wood chip and pellet energy consumption during milling. Thus it proposes parameters and measurement methods that have to be taken into account when milling modelling comes to an end for biomass or densified biomass Energy consumption during wood milling depends on three main factors: the material moisture content, the particle size difference between the feed and the milled product, and the material itself. The latter may be characterized by a single grindability parameter based on an adaptation of Von Rittinger’s constant. A relation characterizing wood pellet energy consumption as a function of the particle size distribution of the pellet ingredients and the milled pellets is proposed as well. This is characteristic of each type of pellet for each moisture content value considered [less ▲]

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See detailIntegration of near-surface geophysical, geological and hydrogeological data with multiple-point geostatistics in alluvial aquifers
Hermans, Thomas ULg

Doctoral thesis (2014)

Alluvial plains constitute essential geological bodies for environmental studies such as contaminated sites remediation, low-enthalpy geothermal energy or groundwater resources. The heterogeneity of these ... [more ▼]

Alluvial plains constitute essential geological bodies for environmental studies such as contaminated sites remediation, low-enthalpy geothermal energy or groundwater resources. The heterogeneity of these deposits governs flow processes and needs to be quantified. A proper description of such complex deposits requires an integrated approach combining geological, geophysical and hydrogeological data. Solving such spatial inverse problems in the Earth Sciences remains a considerable challenge given the large number of parameters to invert for, the non-linearity of forward models and, as a result, the ill-posedness of the problem. Geostatistics is therefore needed to specify prior models, more particularly, information to control the spatial features of the inverse solutions. Two-point geostatistical approaches have been developed to describe the heterogeneity of one geological formation but fail to reproduce the heterogeneity of fluvial deposits with multiple facies. Multiple-point statistics (MPS) introduced the training image (TI) concept to replace the variogram within an extended sequential simulation framework. The use of geophysics to constrain such simulations has been studied in the petroleum industry with wave-based methods (seismic reflection), but little research has been done to assess the use of near-surface potential methods to condition MPS in environmental studies. In this work, we propose to integrate geological (borehole logs), geophysical (electrical resistivity tomography (ERT) profiles) and hydrogeological (hydraulic heads) data within MPS models on the alluvial plain of the Meuse River, Belgium. Potential-based geophysical methods being integrative, they suffer from a relatively poor resolution. We first study how we can improve the informative content of geophysical inversion by including prior information in the ERT inverse problem. Three methods are tested and compared in several field cases, namely the reference model inversion, the structural inversion and the regularized geostatistical inversion. If every method has advantages and drawbacks, the best suited method for the considered problem is the regularized geostatistical method. Electromagnetic borehole logs enable to derive the vertical correlation length of electrical resistivity in the deposits and to subsequently use it to constrain the inversion. In addition to the knowledge of the bedrock position, it enables to retrieve an electrical resistivity distribution of the deposits close to direct observations. This ensures that geophysical models will be informative to constrain MPS simulations. Given the lack of geological and sedimentological data to build accurate TIs, a data base of TIs is built using several different parameters and scenarios. They are all based on a three facies description: clay/loam, sand and gravel corresponding to low, intermediate and high hydraulic conductivity. Then, we develop a methodology to verify the consistency of independently-built TIs with geophysical data. Our methodology starts by creating subsurface models with each TI. From these models we create synthetic geophysical data and from this synthetic data, synthetic inverted models. These models are now compared with a single inverted model obtained from the field survey, allowing for our definition of what is ``consistent''. To that extent, we calculate the Euclidean distance between any two inverted models as well as field data and visualize the results in a 2D or 3D space using multidimensional scaling (MDS). With this technique, it is possible to verify if field cases fall in the distribution represented by synthetic cases, and thus are consistent with them. In a second step, we present a cluster analysis on the MDS-map to highlight which parameters are the most sensitive for the construction of TI. Based on this analysis, a probability of each geological scenario is computed through kernel smoothing of the densities in reduced projected metric space. The integration of hydrogeological data is made through a stochastic inversion method: the probability perturbation method (PPM), using MPS constrained with geophysical data to generate models. The PPM algorithm automatically seeks solutions fitting both hydrogeological data and training-image based geostatistical constraints. Only geometrical features of the model are affected by the perturbation, i.e. we do not attempt to directly find the optimal value of hydrogeological parameters (chosen a priori), but the optimal spatial distribution of facies whose prior distribution is quantified in a training image. Tracing experiments may be used to further constrain hydrogeological models. ERT has proven its ability to monitor salt tracer tests, but few studies have investigated its performances in thermal tracing experiments. In this study, we demonstrate the ability of surface and crosshole ERT to image quantitatively temperature changes during heat injection experiments. Such resistivity data provides important information to improve hydrogeological models. Our study proves that ERT, especially crosshole ERT, is a reliable tool to follow thermal tracing experiments. It also confirms that ERT should be included to in situ techniques to characterize heat transfer in the subsurface and to monitor geothermal resources exploitation. [less ▲]

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See detailL’antonymie. Définition de l’antonymie en langue et description des fonctions sémantico-référentielles de la co-présence antonymique en discours
Steffens, Marie ULg

Doctoral thesis (2014)

Grâce à un examen critique des travaux consacrés à l’antonymie, nous avons pu définir l’antonymie comme une relation multiforme qui touche des unités très différentes sur les plans sémantique et morpho ... [more ▼]

Grâce à un examen critique des travaux consacrés à l’antonymie, nous avons pu définir l’antonymie comme une relation multiforme qui touche des unités très différentes sur les plans sémantique et morpho-syntaxique mais dont l’unicité réside dans une opposition binaire fondamentale enracinée lexicalement. Nous avons ainsi dépassé la simple distinction entre contraires et contradictoires pour entrer dans la fascinante diversité de l’opposition et montrer comme les notions de graduation, de graduabilité, de scalarité, de borne et de seuil se combinent pour forger l’identité sémantique de chaque paire d’antonymes, la rapprocher ou la distinguer des autres. Grâce à l’analyse empirique d’énoncés extraits du journal Le Monde, nous avons montré que la co-présence antonymique en contexte s’appuie pour faire sens sur les relations antonymiques inscrites dans la mémoire linguistique des locuteurs, où sont fortement associées la forme et le sens des antonymes. Nous avons également montré comment la plongée de deux antonymes dans un contexte d’emploi peut moduler leur opposition et la définition du lexème neutre ou intermédiaire, lorsqu’il existe. Les antonymes co-présents, grâce aux rôles sémantico-syntaxiques qu’ils peuvent jouer, contribuent à la structuration des énoncés dans lesquels ils sont employés parce qu’ils organisent les unités qui les entourent sur le plan sémantico-référentiel. [less ▲]

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See detailUtilisation de biocapteurs microbiens GFP pour la caractérisation des performances des bioréacteurs
Brognaux, Alison ULg

Doctoral thesis (2014)

The scale-up of bioprocesses is a critical step during bioproducts development. Actually, the mixing operation’s efficiency drops when the reactor volume increases: gradients of glucose and oxygen appear ... [more ▼]

The scale-up of bioprocesses is a critical step during bioproducts development. Actually, the mixing operation’s efficiency drops when the reactor volume increases: gradients of glucose and oxygen appear when operating in fed-batch mode, causing losses of production. The aim of this project is the scale-up and sizing of bioreactors based on the direct physiological parameters to consider this heterogeneity. Concretely, it consists in obtaining an on-line signal of the physiological status of micro-organisms. The coding sequence of the Green Fluorescent Protein (GFP) has been inserted after gene promoters of interest in Escherichia coli to built biosensors. A particular focus has been paid on promoters responding to general stress or specifically to lack of glucose and on those responding to cell growth rate. The GFP biosensors of interest have been tested in scale-down bioreactors, allowing to reproduce industrial hydrodynamic conditions at a laboratory scale. A mini-bioreactor platform has also been developed to enable a high throughput screening of biosensors. The intracellular accumulation of GFP has been measured by flow cytometry and GFP release has been monitored by western blot analyses. For biosensors sensitive to stress general response or glucose limitation, GFP has been induced during a glucose limitation and repressed by comparison when glucose heterogeneities appear. The use of a destabilized GFP has been considered in this project for ribosomal biosensors to approach more instantaneous physiological responses of microorganisms. For these ones, the response is proportional to growth rate during the batch phase, but more complex mechanisms take part during a prolonged glucose limitation. Membrane permeability has also been studied and has been noticed more important in homogeneous fed-batch bioreactors than in scale-down reactors. As GFP leakage has been noted in the extracellular medium, a study has also been carry out about proteins released in the extracellular medium (leakage), and correlated with the cell permeability. Finally, an on-line flow cytometer has been developed for the characterization of physiological status of micro-organisms during the bioprocess, and a 3D-ORM probe allowed to measure their viability on-line [less ▲]

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See detailTheoretical studies of gravitational lensing phenomena: the case of multiply imaged quasars
Wertz, Olivier ULg

Doctoral thesis (2014)

In the early 1960s, gravitational lensing has received a special attention when S. Liebes and S. Refsdal have derived in detail some of the basic equations of the theory. While Liebes (1964) discussed the ... [more ▼]

In the early 1960s, gravitational lensing has received a special attention when S. Liebes and S. Refsdal have derived in detail some of the basic equations of the theory. While Liebes (1964) discussed the probability of detecting these effects and considered several astrophysical applications, Refsdal (1964) derived, inter alia, his famous relation which links the Hubble parameter (H0) to the expected time delays between pairs of lensed images. From that moment, the scientific community fully realized that gravitational lensing effects offer a new way of probing cosmology. However, an important fact has been to accept that the determination of H0 seems to be model dependent, not only on the universe model, but also on the mass distribution of the deflector. The main topic of the present thesis constitutes a straight continuation of this inquiry. We have been sounding parts of the mathematical lensing framework on two fronts. First, considering to first order a very small misalignment between the source, the lens and the observer, we have derived the expressions of the lensed image positions along with their amplification ratios, for the case of power-law axially symmetric mass distributions, the so-called ε-γ family of models (Wertz, Pelgrims & Surdej, 2012). After combining these results, it has allowed us to derive an expression for H0 independently of the model parameters. We have extended this study to the ε-γ family of models with external shear, as well as to the singular isothermal ellipsoid (SIE) models. For both these types of models, we have obtained an expression of H0 which is once again independent, to first order, of the model parameters. Furthermore, even though these families of models remain rigorously distinct, except for the singular isothermal sphere (SIS) and the perfect alignment, the expression of H0 in terms of observable quantities and of the source position takes surprisingly the same simple form. In addition, we have demonstrated the feasibility of analytically constraining to first order the model parameters by only using the astrometric positions of the lensed images. Therefore, for the case of a small misalignment between the source, the deflector and the observer, it is straightforward to determine whether the ε-γ or SIE family of models constitutes a judicious representation of the mass distribution of the deflector. It is conceivable that similar results can be deduced for other families of models. Secondly, we have developed a new analytical approach in order to determine the expression of the deflection angle, hereafter α. Since the latter depends on the deflector mass distribution, there exists no global explicit expression but only an implicit definition of α. Therefore, the analytical methods used to obtain the explicit expression differ for different types of mass distribution. However, using the Fourier transform theory, one may basically express α in terms of the Fourier transform of the surface mass density. Such a method allows us to approach any mass distribution in a unique way. As a first application, we have separately derived the expression of the two components of α for the case of homoeoidal symmetric lenses (Wertz & Surdej, 2013). This original result constitutes a first proof that the Fourier approach constitutes a promising alternative to the complex formalism introduced by Bourassa & Kantowski (1975, corrected by Bray 1984). A particular case of homoeoidal symmetric lenses lies in the non-singular isothermal ellipsoid (NSIE) family of models for which the analytical treatment has been somewhat limited (Kormann & al. 1994). The use of the Fourier approach has made possible to derive a complete analytical treatment of the NSIE, i.e. the expressions of the deflection angle, the deflection potential, and the critical and caustic curves even off the axis (Wertz & Surdej, submitted to MNRAS in february 2014). This original result has allowed us to investigate and better understand this family of models. Furthermore, it is of great interest for mass distribution modeling and to rigorously determine the expected time delays between pairs of lensed images. The previous analytical treatments mainly consisted of parametrical models for the deflector. An alternative way to grasp lenses consists in modeling their mass distribution using non-parametric models. With this aim in mind, we have proceeded as follows: we tessellate the lens plane with squared pixels, and associate to each of them a constant surface mass density. Making use of the Fourier approach, we have derived the expression of the deflection angle for the whole grid. This result contains the main advantage of the non-parametric models, i.e. to model any type of mass distribution without any preconception, and the usefulness of handling quantities which can be described with analytical functions. [less ▲]

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See detailWhen Firms Cross-List, do Investors care?
Mouchette, Xavier ULg

Doctoral thesis (2014)

Over the past three decades, financial markets have experienced a tremendous increase in global linkages. Cross-Listing is one prominent example of these trends. By cross-listing firms can proactively ... [more ▼]

Over the past three decades, financial markets have experienced a tremendous increase in global linkages. Cross-Listing is one prominent example of these trends. By cross-listing firms can proactively broaden their shareholder basis, overcome limitations of their domestic markets, and link their securities to multiple capital markets at a time. Its far-reaching financial effects are associated with this internationalization of the firm’s capital structure. This thesis focuses on the valuation implications of cross-listing towards major international exchanges. Early attempts to explain these valuation effects called upon international capital market segmentation. This view has since then been highly challenged. Nevertheless, the magnitude of segmentation and its relationship with cross-listing has received much less attention. Our empirical investigations first establish that firms that are about-to-cross-list are not entirely integrated with global capital markets. Furthermore, previous cross-listings which originate from the same home country and country funds both have significant importance to assess the degree of this integration. We next disentangle between the validity of segmentation and informational improvement arguments in explaining the magnitude of cross-listing price effects. Our results suggest that firms that cross-list towards the US markets obtain benefits through the resolution of informational barriers only, while firms from emerging markets derive benefits as a function of their pre-cross-listing segmentation. Crucially, both channels appear conditional on the preceding cross-listing activity. Finally, reactions to cross-listing prove to be not as immediate as assumed by the classical event study literature. Substantial investors' anticipation of the cross-listing decision is demonstrated, as well as the variation regarding the speed and length of the reactions. Size, destination exchange, and the extent to which the firm is integrated into international capital markets appear to be the most influential factors. [less ▲]

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See detailCharacterization of thin layers into concrete with Ground Penetrating Radar
Van der Wielen, Audrey ULg

Doctoral thesis (2014)

The Ground Penetrating Radar (GPR) is a non-destructive method used for roads and buildings inspection: it is well adapted to detect the different layers constituting the structures. The objective of this ... [more ▼]

The Ground Penetrating Radar (GPR) is a non-destructive method used for roads and buildings inspection: it is well adapted to detect the different layers constituting the structures. The objective of this thesis is to develop a method for a fast determination of the properties of a buried layer on the basis of surface GPR measurements. The observation of the GPR waves propagation in numerical simulations led to develop an analytical model, which could be applied to the experimental determination of laboratory layered structures. [less ▲]

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See detailNonlinear Modal Analysis of Conservative and Nonconservative Aerospace Structures
Renson, Ludovic ULg

Doctoral thesis (2014)

The concept of nonlinear normal modes (NNMs) provides a solid and rigorous theoretical framework for the analysis of the nonlinear oscillations of mechanical systems. If NNMs have been studied since more ... [more ▼]

The concept of nonlinear normal modes (NNMs) provides a solid and rigorous theoretical framework for the analysis of the nonlinear oscillations of mechanical systems. If NNMs have been studied since more than fifty years, it is only very recently that contributions dealing with their numerical calculation have been reported in the literature. Although these methods pave the way for the application of NNMs to more complex systems, they have not yet reached the necessary maturity. In this context, the purpose of this research is (i) to further investigate the performance of an existing method for computing the NNMs of conservative systems and (ii) to propose two new methods for the computation of NNMs of nonconservative systems. The first contribution of this thesis is to calculate the NNMs of a real-life aerospace structure, the SmallSat spacecraft developed by EADS Astrium. An algorithm that combines an advanced shooting method with the pseudo-arclength continuation technique is utilized. We show that the NNMs provide a very useful interpretation of the strongly nonlinear dynamics of the spacecraft. One specific contribution is to numerically reproduce with great fidelity several interactions between modes with noncommensurate linear frequencies that were observed experimentally. The second original contribution of this thesis is to develop two new methods for computing the NNMs of damped systems. The first method solves the partial differential equations (PDEs) governing the geometry of the NNM. The PDEs are recognized as hyperbolic, and it is shown that they require appropriate numerical treatments including specific boundary conditions. The proposed method combines a streamline upwind Petrov-Galerkin finite-element formulation with a resolution strategy based on annular domains to grow sequentially the manifold. The algorithm is demonstrated using a wide variety of systems ranging from two-degree-of-freedom to multi-degree-of-freedom nonlinear systems with linear and nonlinear damping. The applicability of the algorithm to complex real-life structures is demonstrated using a full-scale aircraft. The second method presented in this work computes a NNM as a collection of trajectories defined with boundary value problems (BVPs). The method has the distinctive advantage that it does not rely on a parameterization of the NNM. It is demonstrated on two-degree-of-freedom examples featuring linear and nonlinear damping. [less ▲]

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See detailDroit électoral et principe d'égalité. L'élection des assemblées législatives nationales en droit allemand, belge et britannique
Bouhon, Frédéric ULg

Doctoral thesis (2014)

The study concerns the election law and the equality principle in three European legal systems, i.e. the Federal Republic of Germany, the Kingdom of Belgium and the United Kingdom. In this framework, the ... [more ▼]

The study concerns the election law and the equality principle in three European legal systems, i.e. the Federal Republic of Germany, the Kingdom of Belgium and the United Kingdom. In this framework, the research is structured into two principal questions. I firstly wonder whether the election law guarantees equality among the governed people. Should the answer to that question be negative, I secondly check if the inequality can be legally justified in democratic systems. My thesis is a nuanced answer to these questions. The work shows that election law, considered under the scope of the equality principle, includes two categories of legislations which effect is opposed: some legal rules tend to distribute equally the faculty to influence the composition of the elected assemblies, while others tend to distribute unequally that faculty. Among the rules of the second category, I argue that the tendency to inequality can be partly legally justified by the purposes of these rules, but is also a mean – hardly justifiable in a democratic system – that helps persons and parties in government to remain in power. [less ▲]

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See detailSynthèse et étude du composé Li4Ti5O12 comme électrode négative dans les accumulateurs Li-ion
Jamin, Claire ULg

Doctoral thesis (2014)

Electrical energy consumption has increased dramatically and its mode of consumption has diversified over the years, with the development of mobile energy storage devices such as lithium batteries. The ... [more ▼]

Electrical energy consumption has increased dramatically and its mode of consumption has diversified over the years, with the development of mobile energy storage devices such as lithium batteries. The present thesis is dedicated to the synthesis and study of the compound Li4Ti5O12 as negative electrode in Li-ion batteries. The main objective is the development of innovative synthesis techniques based on soft chemistry in order to control and study the effect of structural and microstructural parameters on the electrochemical properties of the compound. Because of its ability to intercalate/deintercalate Li+ ions in its structure without stress-generating volume changes of the structure, Li4Ti5O12 is considered as a so-called "zero-strain" electrode, favouring excellent cycling performance. Therefore, this compound appeared to us a most interesting candidate in this study. The first part of this work investigates a method involving the freeze-drying of a gel precursor followed by self-ignition. Hydroxypropylmethylcellulose is used as an additive and the synthesis of Li4Ti5O12 takes place in four steps : Gelling – Freeze-drying – self-ignition – Calcination. Ammonium nitrate was also added to the reactants to determine the impact on the self-ignition process and the consequences on the structure, microstructure and electrochemical properties of the compound. Indeed, a major issue usually encountered in self-ignition is controlling the amount of heat released, and therefore the temperature during self-ignition. These factors greatly influence the structural and microstructural properties of the compound. The results show that addition of ammonium nitrate leads to an excessive crystal growth which is unfavorable to electrochemical properties of the compound. In the second part of the thesis, the spray-drying method has been investigated using both a lab-scale and a pilot-scale equipment, to take into account possible developments on an industrial scale. For both devices, the influence of concentration on particle morphology was observed. The lab spray-dryer allowed us to obtain a convex to mushroom morphology. For the pilot spray-dryer, the morphologies vary from cauliflower to smooth hollow spheres, and can be further modified by addition of a carbonate source which decomposes during calcination. Depending on the particle morphology and its surface for intercalation of Li+ ions, the electrochemical performances have been improved, sometimes considerably. The drying temperature also affects the performance of the compound through the agglomeration rate of the particles. In conclusion, a wide panel of microstructures has been obtained by investigating two synthesis methods with various sets of experimental conditions. Although all these powders are Li4Ti5O12, there is a significant variation of their electrochemical performance and we have attempted to correlate these with particle morphology. Some prominsing results have been obtained and suggest that performance can be further improved through future work, on both fundamental and applied aspects. [less ▲]

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See detailAcoustic communication in Ophidiiformes: a case study using Ophidion rochei
Kever, Loïc ULg

Doctoral thesis (2014)

A ce jour, la biologie des Ophidiiformes reste peu connue car la majorité des espèces de ce groupe est inféodée aux eaux profondes. Celles qui ne le sont pas ont adopté un mode de vie nocturne, passant la ... [more ▼]

A ce jour, la biologie des Ophidiiformes reste peu connue car la majorité des espèces de ce groupe est inféodée aux eaux profondes. Celles qui ne le sont pas ont adopté un mode de vie nocturne, passant la journée cachées dans le sable, les anfractuosités d’un récif, ou un hôte invertébré en fonction de l’espèce considérée. Des études antérieures ont montré que les appareils de production de sons des Ophidioidei (Ophidiidae et Carapidae) sont complexes et présentent des différences interspécifiques marquées. De plus, l’oreille interne est généralement bien développée. Ces poissons étant actifs dans le noir, la communication acoustique devrait tenir un rôle important dans leur biologie. Ce travail de recherches s’attèle, par différentes approches, à étudier cette thématique en utilisant Ophidion rochei comme cas d’étude. Cet Ophidiidae psammobionte, présente un dimorphisme sexuel marqué au niveau de l’appareil de production de sons avec notamment la présence chez les mâles d’une structure minéralisée à l’avant de la vessie natatoire : le « rocker bone ». Pour mieux cerner la fonction des différentes structures intervenant dans la production et la réception de sons, des comparaisons ont été réalisées avec deux Carapidae : Onuxodon fowleri pour la production de sons et Carapus acus pour la réception de sons. L’étude établit que les espèces O. rochei et C. acus peuvent entendre les sons de leurs conspécifiques. Cependant, l’apport principal de cette partie est la démonstration que la grande taille des otolithes (en valeur absolue ou relative) n’est pas liée à de meilleures capacités auditives. De gros otolithes seraient principalement associés à une plus grande acuité de l’appareil stato-acoustique pour des espèces vivant dans des milieux accidentés. Les mâles et les femelles O. rochei produisent des sons uniquement après le coucher du soleil, durant la période de reproduction qui se déroule de juin à octobre. Ces sons apparaissent courts et tonaux chez les femelles, longs et pulsés chez les mâles. Ces différences dans les signatures acoustiques sont clairement liées au dimorphisme sexuel marqué bien qu’un patron moteur commun soit conservé chez les deux sexes. Brièvement, le muscle sonique dorsal servirait à mettre la vessie natatoire sous tension et le muscle sonique ventral serait à l’origine de l’émission de chaque pulse. De plus, les mâles présentent dans les caractéristiques sonores des différences individuelles marquées qui doivent refléter leur statut reproducteur et/ou leur taille. Chez O. fowleri, les deux sexes possèdent des « rocker bones » de taille et de forme différentes. Les sons enregistrés sont uniquement pulsés, mais ces poissons se distinguent de nombreux téléostéens par leur capacité à moduler le taux de pulsation. La comparaison des morphologies et mécanismes permet de soutenir l’hypothèse selon laquelle les « rocker bones » des deux taxa sont le résultat de convergences évolutives. Chez beaucoup de téléostéens, les sons sont utilisés pour supporter des stimuli d’ordre visuel. Les Ophidioidei étant actifs dans le noir, les contraintes évolutives ont principalement dû se marquer au niveau de l’appareil producteur de sons. En conclusion, la morphologie des appareils de production de sons, le dimorphisme sexuel, les caractéristiques uniques des sons produits, leur moment d’émission dans l’année et dans la journée soulignent la place importante de la communication acoustique au sein des Ophidioidei. [less ▲]

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See detailProduction, transformation artisanale et commercialisation locale des produits alimentaires traditionnels au Vietnam: le cas du vermicelle de tolomane à Hung Yen
Le, Thi Long Vy ULg

Doctoral thesis (2014)

In Vietnam, the vermicelli of Canna edulis Ker Gawl. (C. indica L.) is an artisanal and traditional product, regularly consumed in the festive occasions. From Canna edulis Ker Gawl cultivation to trading ... [more ▼]

In Vietnam, the vermicelli of Canna edulis Ker Gawl. (C. indica L.) is an artisanal and traditional product, regularly consumed in the festive occasions. From Canna edulis Ker Gawl cultivation to trading of vermicelli of Canna edulis at the local level, the vermicelli commodity chain belongs to peasant economy with many actors involved. This research aims at a better understanding of how the actors of vermicelli commodity chain adapt to current socio-economic and environmental conditions of the villages which belong to two communes (Tu Dan and Yen Phu) located in Hung Yen Province. The surveys among 90 farmers and discussions with a group of producers who cultivate the canna and practice flour processing, and a group of vermicelli processors have been carried out from 2010 to 2012. According to our research results, vermicelli commodity chain has created a considerable additional quantity of jobs for local people within the villages of vermicelli processing and the neighboring ones. Thanks to these activities, the rural households income and production investment have been increased. Net income estimated per hectare of canna is about 22.2 million VND (about 822 €), and nearly 4.5 million VND (167 €) per ton of flour produced, and up to 1.7 million VND per ton of vermicelli product (about 63 €). In addition, these activities allow to diversify the sources of family incomes in the countryside. These activities also contribute to stabilize and increase the living standard of farmers (in 2010, the net family income (NFI) due to canna production accounted for 8% to 34 % of farming income; the NFI of vermicelli processing represented between 35% and 86 % of total processing family income). The value-added generated from this vermicelli commodity chain is important, up to 186 million VND (about 7,900 €) per hectare of canna, in which 38 % for flour processing; 20% for vermicelli processing and 20 % for canna cultivators. Thus, the vermicelli commodity chain contributes to meet a specific demand for traditional food in Vietnam. This chain contributes to the rural economy of traditional villages through improving the sources of familial income. However, it is necessary to increase the product quality and to improve the vertical and horizontal linkages between the actors in order to guarantee the sustainable development of this vermicelli chain. [less ▲]

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See detailMénages ruraux et lutte contre la pauvreté : cas des communes de Tu Ly et de Xuang Phong dans la province de Hao Binh Viet Nam
Mai, Lan Phuong ULg

Doctoral thesis (2014)

Since 1998, Viet Nam developed many poverty reduction strategies with the assistance of the WB and the IMF. However, although the national rate of poverty decreased in absolute terms, it does not reflect ... [more ▼]

Since 1998, Viet Nam developed many poverty reduction strategies with the assistance of the WB and the IMF. However, although the national rate of poverty decreased in absolute terms, it does not reflect a real reduction in poverty and does not take into account the nature of poverty. Income and opportunities inequality increased between urban and rural areas, between different social classes and between the Kinh (majority group in Viet Nam) and ethnic minorities. Poverty of ethnic minorities has become an ongoing challenge. In 2010, there were 66.3% of the poor among ethnic minorities against only 12.9% for the Kinh population. This thesis illustrates a reflection on the issue of poverty in Viet Nam and in particular mountainous northern regions where the poverty rate is the highest, reaching 39.4 % in 2012. The historical approach, the capacity approach, the descriptive statistical analysis and case analysis are used to conduct this research. The first difficulty is the identification of poor households and beneficiaries of poverty reduction strategies. Other difficulties are disclosed by the analysis of strategies against poverty: information confusion, budget limitation, insufficient participation of local people in program planning and monitoring, limited autonomy at the local level. Finally it appears that strategies against poverty are not efficient. In addition, land resource privatization, particularly forest resources, limits minority farmers’ ability to cope with unexpected risks Faced with this situation, a possible solution could be to strengthen the role of farmers' associations. Taking into account the ideas and initiatives of local actor, driven by farmers' associations, would have a positive impact on the poverty reduction strategy. Donations and subsidies to individuals should no longer be practiced. In the present threatening world, solidarity among small farmers is necessary to enable them to find their place in the production system and keep the justified profits. In the long run, it is better to give financial support to assist groups and support initiatives by associations of small farmers to facilitate their participation in the market economy while improving their well-being. [less ▲]

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See detailEtude des possibilités de culture de Jatropha curcas L. dans la région de Kinshasa en République Démocratique du Congo (RDC)
Minengu Mayulu, Jean de Dieu ULg

Doctoral thesis (2014)

Au cours de ces dernières années, des plantations de Jatropha curcas L. ont été mises en place dans de nombreuses régions d’Afrique subsaharienne pour la production d’agrocarburants sans connaissances ... [more ▼]

Au cours de ces dernières années, des plantations de Jatropha curcas L. ont été mises en place dans de nombreuses régions d’Afrique subsaharienne pour la production d’agrocarburants sans connaissances préalables des conditions de rentabilité et des techniques de production les mieux adaptées aux contextes locaux. L’objectif du présent travail est de lever cette lacune pour la région de Kinshasa en apportant des réponses aux principales questions qui conditionnent la mise au point d’un agrosystème durable basé sur la culture de J. curcas. Pour atteindre cet objectif, les performances d’une plantation pilote installée à proximité de la cité de Mbankana en décembre 2007 ont été évaluées et quatre essais ont été réalisés à partir de juillet 2009 à janvier 2013 dans deux sites représentatifs des conditions du Plateau des Batéké (Mbankana et Mongata) et à proximité de la rivière N’sele dans la banlieue de Kinshasa. Les résultats obtenus montrent que les facteurs de l’environnement et les pratiques culturales ont une influence sur le rendement en graines et en huile de J. curcas. Les faibles rendements obtenus, le coût très élevé des intrants (engrais et insecticides) et les faibles quantités de graines récoltées par journée de travail sont les principales causes de l’absence de rentabilité de la culture pure de J. curcas dans les premières plantations mises en place avec du matériel végétal local subspontané. Les principaux insectes ravageurs de J. curcas dans la zone d’étude sont les grillons Brachytrupes membranaceus Drury (Orthoptera, Grillidae) qui s’attaquent aux jeunes plantes lors de leur mise en place en saison pluvieuse (octobre à décembre), les chenilles mineuses de feuilles Stomphastis thraustica Meyrick (Lepidoptera, Gracillariidae), les chrysomèles Aphthona sp. (Coleoptera, Chrysomelidae) qui consomment le limbe des feuilles et les bourgeons, ainsi que les punaises à bouclier Calidea sp. (Heteroptera, Scutelleridae) qui causent des dégâts aux fleurs et aux capsules. Parmi ceux-ci, la chrysomèle est pour l’instant le ravageur le plus dommageable. En l’absence de traitements insecticides, le niveau des pertes de rendement occasionnées par ces insectes ravageurs atteignent 90% en culture pure sur le Plateau des Batéké. La gravité des dégâts des insectes ravageurs sur J. curcas est plus élevée en culture pure (>60%) que quand il est associé à d’autres cultures annuelles (<45%). La mise au point de méthodes durables de contrôle des ravageurs est une des conditions indispensables à l’installation de plantations de J. curcas dans la région de Kinshasa. L’application de la taille, de la fertilisation minérale et de la couverture du sol avec Stylosanthes guianensis (Aublet) Swartz, permet d’améliorer significativement le rendement en graines de J. curcas Onze écotypes de J. curcas, collectés dans les différentes régions de la RDC et mis en culture au Plateau des Batéké, ont montré des différences significatives en termes du développement végétatif et des rendements en graines et en huile. Le rendement moyen obtenu en 3eme année de production par l’écotype le plus productif (Panu : 473,1±3,6 kg de graines sèches ha-1) était près de 7 fois plus élevé que le rendement de l’écotype qui a produit le moins (Ilebo : 68,6±3,6 kg ha-1). Contrairement à ce qui était annoncé dans la littérature, le temps nécessaire pour l’entrée en pleine production de J. curcas en conditions tropicales humides est supérieur à 5 ans. Il n'est pas possible de déterminer sur base de nos résultats, le niveau exact de rendement qui sera obtenu quand les plantes entreront en pleine production. Quel que soit celui-ci, le coût très élevé de la main d’œuvre nécessaire à la collecte des graines de J. curcas et au désherbage limite fortement les perspectives de rentabilité de la culture pure dans la région de Kinshasa. Dans les zones enclavées du pays, où le coût de la main d’œuvre est moindre et où le prix du diesel est plus élevé, la production de J. curcas peut constituer l’une des solutions pour résoudre les problèmes d’accès à l’énergie. [less ▲]

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See detailLa résilience chez les plus vulnérables au Rwanda
Militery Ngamata, Olivier ULg

Doctoral thesis (2014)

After the tragedy of the genocide against Tutsi in 1994, the Rwandan Government has developed and implemented different programmes and interventions in the sector of social protection in order to reduce ... [more ▼]

After the tragedy of the genocide against Tutsi in 1994, the Rwandan Government has developed and implemented different programmes and interventions in the sector of social protection in order to reduce the poverty of the vulnerable populations and so reach the Millennium Development Goals (MDGs). The different interventions done in the context of social security of the poor people are considered as means of increasing the economy, integrating people in employment market, improving human development thanks to a better access to health and education, and reducing poverty. After the context and justification of the research as well as the methods for data collection, this study focuses primarily on the conceptualization of resilience and connected concepts. Secondly, it scrutinizes the impact of the three programmes of social protection that were developed to reduce poverty of the beneficiaries. The first programme is FARG that supports the survivors of the 1994 genocide against the Tutsi in the domain of education, access to accommodation, medical health and income generating activities. The second programme is Ubudehe-VUP-2020. This one helps very poor households via direct financial transfers, creation of jobs and access to financial services. Girinka is the third programme; it contributes to food improvement, subsistence means and land fertility by supplying a dairy cow to poor families. In third position, this research assesses the achievements of the association of the widows survivors of genocide called - Agahozo (AVEGA) as well as the successes so far reached by the widows beneficiaries. The widows consider AVEGA as an important ‘tutor for resilience’ because it not only deals with their psychological aspects related to the tragedies they experienced but also the promotion and development of economic activities that can supply them with an income for their social reintegration at both economic and social levels. Thus, AVEGA involves a diversity of actors in order to help the widows and implement various income generating activities. Research conducted on the field has targeted, in last position, the most resilient widows. These widows have got support from social protection programmes and AVEGA, in order to involve in income generating activities among which the most developed are agriculture, animal rearing and commerce. All in all, the widows of genocide who were surveyed positively commented the support they get from SPP and AVEGA regarding the reinforcement of their economic resilience. [less ▲]

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See detailAudiovisual spatial congruence, and applications to 3D sound and stereoscopic video
André, Cédric ULg

Doctoral thesis (2014)

While 3D cinema is becoming increasingly established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D ... [more ▼]

While 3D cinema is becoming increasingly established, little effort has focused on the general problem of producing a 3D sound scene spatially coherent with the visual content of a stereoscopic-3D (s-3D) movie. The perceptual relevance of such spatial audiovisual coherence is of significant interest. In this thesis, we investigate the possibility of adding spatially accurate sound rendering to regular s-3D cinema. Our goal is to provide a perceptually matched sound source at the position of every object producing sound in the visual scene. We examine and contribute to the understanding of the usefulness and the feasibility of this combination. By usefulness, we mean that the technology should positively contribute to the experience, and in particular to the storytelling. In order to carry out experiments proving the usefulness, it is necessary to have an appropriate s-3D movie and its corresponding 3D audio soundtrack. We first present the procedure followed to obtain this joint 3D video and audio content from an existing animated s-3D movie, problems encountered, and some of the solutions employed. Second, as s-3D cinema aims at providing the spectator with a strong impression of being part of the movie (sense of presence), we investigate the impact of the spatial rendering quality of the soundtrack on the reported sense of presence. The short 3D audiovisual content is presented with three different soundtracks. These soundtracks differ by their spatial rendering quality, from stereo (low spatial coherence) to Wave Field Synthesis (WFS, high spatial coherence). The original stereo version serves as a reference. Results show that the sound condition does not impact on the sense of presence of all participants. However, participants can be classified according to three different levels of presence sensitivity with the sound condition impacting only on the highest level (12 out of 33 participants). Within this group, the spatially coherent soundtrack provides a lower reported sense of presence than the other custom soundtrack. The analysis of the participants' heart rate variability (HRV) shows that the frequency-domain parameters correlate to the reported presence scores. By feasibility, we mean that a large portion of the spectators in the audience should benefit from this new technology. In this thesis, we explain why the combination of accurate sound positioning and stereoscopic-3D images can lead to an incongruence between the sound and the image for multiple spectators. Then, we adapt to s-3D viewing a method originally proposed for 2D images in the literature to reduce this error. Finally, a subjective experiment is carried out to prove the efficiency of the method. In this experiment, an angular error between an s-3D video and a spatially accurate sound reproduced through WFS is simulated. The psychometric curve is measured with the method of constant stimuli, and the threshold for bimodal integration is estimated. The impact of the presence of background noise is also investigated. A comparison is made between the case without any background noise and the case with an SNR of 4 dBA. Estimates of the thresholds and the slopes, as well as their confidence intervals, are obtained for each level of background noise. When background noise is present, the point of subjective equality (PSE) is higher (19.4° instead of 18.3°) and the slope is steeper (-0.077 instead of -0.062 per degree). Because of the overlap between the confidence intervals, however, it is not possible to statistically differentiate between the two levels of noise. The implications for the sound reproduction in a cinema theater are discussed. [less ▲]

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See detailDistributed control of electromechanical oscillations in very large-scale electric power systems
Wang, Da ULg

Doctoral thesis (2014)

Electromechanical oscillations threaten the secure operation of power systems and if not controlled efficiently can lead to generator outages, line tripping and even large-scale blackouts. Different ... [more ▼]

Electromechanical oscillations threaten the secure operation of power systems and if not controlled efficiently can lead to generator outages, line tripping and even large-scale blackouts. Different damping devices, like Power System Stabilizers (PSSs), Thyristor Controlled Series Compensators (TCSCs), and so on, are installed to damp these oscillations. This thesis proposes a trajectory-based supplementary control to improve damping effects of existing controllers, which treats damping control as a multi-step optimization control problem with discrete dynamics and costs. At each control time, it collects current system states, solves the optimal control problem and superimposes the calculated supplementary inputs on the outputs of existing damping controllers, in order to enhance the damping. These supplementary signals are continuously updated, which allows to adaptively adjust and coordinate a subset of existing damping controllers, and eventually all of them. Two kinds of methods, Model Predictive Control (MPC) and Reinforcement Learning (RL), are used to embody the proposed supplementary damping control. Firstly, a fully centralized MPC scheme is designed based on a linearized, discrete, complete state space model. Its performances are evaluated both in ideal conditions and considering realistic state estimation errors, and computation and communication delays. The effects of the number and type of available damping controllers are also studied. This scheme is further extended into a distributed scheme with the aim of making it more viable for very large-scale or multi-area systems. Different ways of decoupling and coordinating between subsystems are analyzed. Finally, a robust hierarchical multi-area MPC scheme is proposed, introducing a second layer of MPC based controllers at the level of individual power plants and transmission lines. Secondly, a tree-based batch mode RL algorithm is applied to carry on the proposed supplementary damping control. Using a set of dynamic and reward four-tuples, it constructs an approximation of the optimal $Q$-function over a given temporal horizon. The actions greediest with respect to the $Q$-function are applied as supplementary signals to existing damping controllers. The scheme is firstly tested on a single generator, and then on multiple generators. Different reward signals and damping levels are also considered. Finally, the combined control effects of MPC and RL are investigated. [less ▲]

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See detailLe développement du raisonnement biomédical et clinique au cours du cursus médical
Collard, Anne ULg

Doctoral thesis (2014)

La Faculté de Médecine de l'Université de Liège a fait le choix, au début des années 2000, de proposer dès la deuxième année de son cursus, un enseignement de type PBL dont un des objectifs principaux ... [more ▼]

La Faculté de Médecine de l'Université de Liège a fait le choix, au début des années 2000, de proposer dès la deuxième année de son cursus, un enseignement de type PBL dont un des objectifs principaux était le développement précoce du raisonnement clinique, essentiel à l'exercice de la médecine. Dans ce cadre, nous avons analysé le processus de raisonnement dans différents contextes et les facteurs qui impactent son développement. Ce développement du raisonnement en lien avec la base de connaissances ainsi que l'utilisation et l'évaluation de cette base de connaissances ont été explorés. Nos travaux démontrent qu'une capacité de raisonnement est manifeste dès la 2ème année du cursus et se développe avec l'expérience. Ils suggèrent que les capacités de raisonnement peuvent être évaluées très tôt dans le cursus médical et que le transfert du raisonnement dans différents contextes est opérationnel. La progression des performances en raisonnement n'évolue pas parallèlement aux performances en connaissances bien que ces deux capacités soient fortement liées. L'importance d'une base de connaissances structurée et hiérarchisée pour favoriser les performances en raisonnement est largement discutée. Un des apports majeurs de nos travaux est la mise en évidence d'une relation étroite entre les capacités de raisonnement et la capacité à auto-évaluer ses propres connaissances. L'évolution de cette capacité avec l'expérience, chez un même étudiant, a pu être démontrée ainsi que son lien avec la réussite. Ces résultats démontrent l'importance de travailler cette capacité dans le cadre des séminaires PBL afin de promouvoir le développement et la validation du processus de raisonnement. Notre réflexion a abouti à la proposition d'un modèle permettant de mettre en perspective les différents facteurs impliqués dans le processus d'apprentissage du raisonnement en lien avec la base de connaissances et son utilisation. [less ▲]

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See detailAbondance et variabilité des méduses en Baie de Calvi (Corse)
Collignon, Amandine ULg

Doctoral thesis (2014)

L’importance et la variabilité temporelle des méduses calycophores et de la méduse schyphozoaire, Pelagia noctiluca en Baie de Calvi (Corse) ont été étudiées en utilisant une série temporelle planctonique ... [more ▼]

L’importance et la variabilité temporelle des méduses calycophores et de la méduse schyphozoaire, Pelagia noctiluca en Baie de Calvi (Corse) ont été étudiées en utilisant une série temporelle planctonique hebdomadaire de 2003 à 2013. Cette variabilité a été comparée à celles des variables biotiques et abiotiques grâce à la technique du calcul des anomalies saisonnières et interannuelles. La diversité des méduses siphonophores calycophores a été décrite et les critères taxonomiques permettant d’identifier les espèces dominantes (Chelophyes appendiculata, Lensia subtilis, Abylopsis tetragona et Muggiaea atlantica) et de leurs stades de développement ont été précisés. Le cycle de développement de Chelophyes appendiculata a été établi sur base de la variation saisonnière climatique des différents stades moyennée sur les 10 années. Cette espèce est rencontrée toute l’année et présente deux générations, par an. Ce cycle est en phase avec les périodes d’abondance du zooplancton et en particulier des copépodes. Il s’inscrit dans la séquence des événements planctoniques liés à stratification de la colone d’eau. La variation interannuelle se marque par la succession des différentes espèces dont l’abondance augmente sur une période de quatre ans environ. Ainsi au cours des 10 ans, Chelophyes est progressivement remplacé par Lensia. La corrélation entre la moyenne annuelle de l’abondance des eudoxies et celle de la température de surface est très significative et suggère le contrôle de la reproduction par la température. Une relation inverse de l’abondance des stades polygastriques et l’abondance du zooplancton suggère un contrôle de ces méduses sur ce dernier. La distribution spatiale des calycophores a été étudiée au large de la Corse en relation avec les différentes masses d’eau et structures hydrologiques associées au front Liguro-provençal. Les plus fortes abondances sont situées au niveau du plateau continental. Dans 90% des échantillons de surface de fortes abondances de microplastiques étaient associées au zooplancton et aux méduses en particulier. L’étude de la variabilité de la méduse Pelagia noctiluca en Baie de Calvi a confirmé que les invasions obéissent à un cycle pluriannuel indépendamment de la pollution. La distribution en essaims a été étudiée en relation avec les contraintes du milieu. [less ▲]

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See detailComputational homogenization of cellular materials capturing micro-buckling, macro-localization and size effects
Nguyen, Van Dung ULg

Doctoral thesis (2014)

The objective of this thesis is to develop an efficient multi-scale finite element framework to capture the macroscopic localization due to the micro-buckling of cell walls and the size effect phenomena ... [more ▼]

The objective of this thesis is to develop an efficient multi-scale finite element framework to capture the macroscopic localization due to the micro-buckling of cell walls and the size effect phenomena arising in structures made of cellular materials. Under the compression loading, the buckling phenomenon (so--called micro--buckling) of the slender components (cell walls, cell faces) of cellular solids can occur. Even if the tangent operator of the material of which the micro--structure is made, is still elliptic, the presence of the micro--buckling can lead to the loss of ellipticity of the resulting homogenized tangent operator. In that case, localization bands are formed and propagate in the macroscopic structure. Moreover, when considering a cellular structure whose dimensions are close to the cell size, the size effect phenomenon cannot be neglected since deformations are characterized by a strain gradient. On the one hand, a classical multi-scale computational homogenization scheme (so-called first-order scheme) looses accuracy with the apparition of the macroscopic localization or the high strain gradient arising in cellular materials because the underlying assumption of the local action principle, in which the stress state on a macroscopic material point depends only on the strain state at that point, is no--longer suitable. On the other hand, the second-order multi-scale computational homogenization scheme proposed by Kouznetsova exhibits a good ability to capture such phenomena. Thus this second--order scheme is improved in this thesis with the following novelties so that it can be used for cellular materials. First, at the microscopic scale, the periodic boundary condition is used because of its efficiency. As the meshes generated from cellular materials exhibit a large void part on the boundaries and are not conforming in general, the classical enforcement based on the matching nodes cannot be applied. A new method based on the polynomial interpolation without the requirement of the matching mesh condition on opposite boundaries of the representative volume element (RVE) is developed. Next, in order to solve the underlying macroscopic Mindlin strain gradient continuum of this second-order scheme by the displacement-based finite element framework, the presence of high order terms (related to the higher stress and strain) leads to many complications in the numerical treatment. Indeed, the resolution requires the continuities not only of the displacement field but also of its first derivatives. This work uses the discontinuous Galerkin (DG) method to weakly impose these continuities. This proposed second--order DG--based FE2 scheme appears to be easily integrated into conventional parallel finite element codes. Finally, the proposed second-order DG-based FE2 scheme is used to model cellular materials. As the instability phenomena are considered at both scales, the path following technique is adopted to solve both the macroscopic and microscopic problems. The micro--buckling leading to the macroscopic localization and the size effect phenomena can be captured within the proposed framework. [less ▲]

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See detailA framework for using decision-support tools at various spatial scales for the management of irrigated agriculture in semi-arid West-Africa
Wellens, Joost ULg

Doctoral thesis (2014)

The Kou watershed, situated in the Southwestern part of Burkina Faso, has succumbed since a couple of decades to a typical theater play of anarchistic water management. With its 1.800 km², this small ... [more ▼]

The Kou watershed, situated in the Southwestern part of Burkina Faso, has succumbed since a couple of decades to a typical theater play of anarchistic water management. With its 1.800 km², this small watershed includes the second largest city of Burkina Faso (Bobo-Dioulasso), a former state run irrigated rice scheme and several informal agricultural zones. Despite the abundance of water resources, most water users find themselves regularly faced with shortages due to an increase in population and low irrigation efficiencies. Local stakeholders are hence in need of easy to use and low-cost decision support tools for the monitoring and exploitation of the water resources at different spatial and user levels. A top-to-bottom string of adapted water management tools has successfully been installed to tackle the problems: from watershed (top) to field level (bottom), not to mention the 1200 ha irrigation scheme. Land use maps have been derived from satellite and aerial images. Combined with data from a network of hydrologic gauging stations, regional water use maps were established. Hot spots in inefficient water use could be geographically identified and more detailed actions undertaken. Scheme Information Management Information System (SIMIS) was put in place for the management of the regions irrigated rice scheme. A more equitable distribution for the ever diminishing available water resources could be elaborated. A public-private partnership was installed to guarantee its sustainability. Day to day water use on irrigated plots was monitored by soil humidity and crop canopy measurements. A simple field-crop-water balance model AquaCrop was calibrated and validated, and is used by extension workers to draft optimal irrigation charts. Each tool is applied independently, requiring only limited data; but their combined results contribute to an improved integrated water management. [less ▲]

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See detailUn cadre pour l'utisation des outils d'aide à la décision à diverses échelles spatiales pour la gestion de l'agriculture irriguée en Afrique de l'Ouest
Wellens, Joost ULg

Doctoral thesis (2014)

Le bassin du Kou, situé dans le sud-ouest du Burkina Faso, est depuis quelques décennies le théâtre de différentes formes de conflits liés à toute une série de problèmes que l’on rencontre généralement ... [more ▼]

Le bassin du Kou, situé dans le sud-ouest du Burkina Faso, est depuis quelques décennies le théâtre de différentes formes de conflits liés à toute une série de problèmes que l’on rencontre généralement dans des zones irriguées. Dans le bassin du Kou, les aménagements hydro-agricoles couvrent une superficie totale de près de 2.000 ha; il s’agit de périmètres privés maraîchers et horticoles, et d’un grand périmètre de 1.200 ha réalisé par l’Etat. Malgré l’abondance en eau liée à la présence de sources importantes, d’une nappe phréatique facilement exploitable et d’un cours d’eau pérenne, la plupart des utilisateurs se retrouvent régulièrement en pénurie d’eau à cause d’une augmentation des utilisateurs et des mauvaises efficiences en irrigation. A la demande des parties prenantes publiques et privées actives dans la région, des outils d’aide à la décision ont été développés afin de garantir le suivi-évaluation des ressources en eau et leur exploitation agricole. Il a également été souhaité que les procédures soient réalisables à moindre coût avec les moyens techniques et financiers localement disponibles. Toute une chaine d’outils d’aide à la décision pour différents niveaux spatiaux a été mise en place : du niveau du bassin versant, à la parcelle en passant par les 1.200 ha du périmètre irrigué. Pour le suivi régional, des cartes d’occupations de sol ont été établies à partir des images satellites et aériennes. Combinées avec des données du réseau hydrométrique, des cartes de consommation en eau régionale ont été dessinées. Des régions présentant de mauvaises efficiences en irrigation ont pu être identifiées et des actions plus détaillées et spécifiques entreprises. Quant au périmètre irrigué, après avoir élaboré un diagnostic des efficiences en irrigation, le logiciel Scheme Irrigation Management Information System a été mis en place afin de proposer des scénarii d’irrigation fiables et équitables, et d’améliorer le rendement du périmètre malgré les ressources en eau en diminution. Un partenariat public-privé a été instauré garantissant la durabilité de la gestion hydro-agricole du périmètre. Au niveau de la parcelle, un modèle robuste de productivité de rendement de culture AquaCrop a été calibré et validé. Ce logiciel permet aux agents de terrain d’évaluer les efficiences en irrigation ainsi que l’élaboration de calendriers d’irrigation plus productifs et efficaces. Chaque outil est appliqué de manière indépendante à son niveau, nécessitant un nombre limité de données d’entrée; mais les résultats combinés contribuent à une gestion intégrée des ressources en eau pour l’agriculture irriguée. [less ▲]

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See detailImplication de la clusterine dans la survie des cellules prostatiques lors de l'apoptose
Ammar, Hayet ULg

Doctoral thesis (2014)

Prostate cancer is the second leading cause of cancer death in men. Although androgen ablation remains the most effective management option, most patients with advanced disease progress to castration ... [more ▼]

Prostate cancer is the second leading cause of cancer death in men. Although androgen ablation remains the most effective management option, most patients with advanced disease progress to castration resistant prostate cancer (CRPC), within two years of treatment. This results, in part, from the increase in the anti-apoptotic molecules expression following androgen withdrawal. Among the proteins involved in this phenomenon, clusterin, also known as testosterone repressed message-2 (TRPM- 2), which exists in two forms: a pro-apoptotic nuclear form (nClU) and a secreted survival factor (sClU). In our study we investigated the role of the secreted form of clusterin in preventing cells from TNFα-induced apoptosis. For this, we first generated a sCLU inducible stable prostatic cancer MLL rat cell line by using the Tet-On gene expression system. With this model we revealed a new mechanism by which sCLU promotes survival in androgenindependent prostate cancer cells, implicating its receptor megalin and the Akt survival pathway. By applying a comparative proteomic analysis in the androgen-independent epithelial cell line MLLTet-sClu induced to overexpress sClu or non induced control-cells, we identified five proteins known to play a role in cancer. These proteins candidates are heat shock proteins Hsp90 and Hsp70, osteopontin (bone sialoprotein, OPN), proliferating cell nuclear antigen (PCNA) and ADP-ribosylation factor 1 (Arf1). Altogether, our data provide new mechanistic insight in sCLU dependent activation of the major survival pathway upregulated in refractory prostate cancer. The identification of the new sCLU protein targets open new avenues for more research to elucidate the significance of clusterin in prostate cancer progression and resistance to therapy. [less ▲]

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See detailL'utilisation de la spectrométrie (NIR) et l’imagerie hyperspectrale (NIR-HIS) proche infrarouge pour étudier la composition chimique et botanique de des fourrages
Dale, Laura-Monica ULg

Doctoral thesis (2014)

Forage quality or nutritive value is related to chemical composition, which can be determinated by laboratory methods. The NIR technique in comparison with classical methods is non-destructive, non ... [more ▼]

Forage quality or nutritive value is related to chemical composition, which can be determinated by laboratory methods. The NIR technique in comparison with classical methods is non-destructive, non-polluting, fast and relatively inexpensive per analysis. Investigations on nutritional quality of Carpathians Apuseni Mountains (Romania) grasslands are rarely performed with NIR technique. Therefore, the objective of the thesis was to develop non-destructive methods for evaluating the quality of feed originating from the Gârda area of the Carpathians Apuseni Mountains (Romania) potentially and to similar grassland arround the world. The first task was to study the potential of NIR spectroscopy for building a spectral database for forage quality based on a large collection of semi-natural grassland samples, using a ‘local’ calibration model built by the Walloon Agricultural Research Centre (CRA-W), in Belgium, to determine various parameters (e.g., protein, dry matter, ash, fibre, fat, aNDFom, ADF, lignin, digestibility, crude energy) from samples collected worldwide, outside Romania. The second task was to develop calibration models for an NIR-HSI system, which involved larger spectral data registration as an image. Until now, analyses to determine plant species were based on botanical composition evaluation, including visual observation, which is a subjective method involving identifying plants directly in the field. Distinguishing samples of pure grassland species can be time consuming, and it was therefore decided to build a spectral database of pure samples and then discriminate these samples into binary and ternary artificial sample mixtures. The main objective of these tasks was to identify the botanical families to which the samples belonged (Poaceae, Fabaceae and Other Botanical Families [OBF]). The focus was not on quantity monitoring, but rather on determining forage quality from stationary experiments in the grasslands. To conclude, this research has shown that it is possible to develop calibration models not only for quality assessment, but also for sample discrimination in dry powder samples. It was intended, that the mathematical models constructed and the database obtained, would be used for future research. [less ▲]

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See detailLa nozione di "partecipazione" nella Glossematica di Louis Hjelmslev
Cigana, Lorenzo ULg

Doctoral thesis (2014)

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See detailStudy of the multi-decadal evolution of the Black Sea hydrodynamics and biogeochemistry using mathematical modelling
Capet, Arthur ULg

Doctoral thesis (2014)

This thesis addresses the biogeochemical cycles in the Black Sea (BS) during the shifting environmental context that affected the BS during the last decades of the 20th century. The study is based on ... [more ▼]

This thesis addresses the biogeochemical cycles in the Black Sea (BS) during the shifting environmental context that affected the BS during the last decades of the 20th century. The study is based on sophisticated data analysis tools and on the development and implementation of a coupled 3D biogeochemical model on the BS domain. The long term variability of the BS hydrodynamical structure was first examined on the basis of in-situ profiles (1950-2012), satellite imagery (1985-2000) and 3D modelling (1960-2000). Profiles of temperature and salinity were used to derive vertical characteristics of the BS structure: the mixed layer depth and the cold content of the Cold Intermediate Layer. To untangle the spatial and temporal trends from this heterogeneous dataset, a general methodology was proposed and embedded in the data analysis software DIVA. The detrended climatologies and long-term time series provided by this approach were used to assess statistical relationships with local atmospheric conditions. Satellite data (sea surface temperature and altimetry) and model results were then analyzed to relate observable surface dynamics to internal hydrodynamic properties. The main multivariate modes of variability of the BS hydrodynamic structure were highlighted on the basis of Empirical Orthogonal Function analysis. Their temporal evolution was explained by the occurrences of specific atmospheric patterns, identified on the basis of neural algorithm analysis and related to the phases of well known teleconnection systems (i.e. the North Atlantic and East Asia/West Russia oscillations). To study the dynamics of eutrophication in the shallow Black Sea NorthWestern Shelf (BS-NWS), a benthic model component was developed that considers the environmental control on diagenetic processes and the bottom shear stress restriction on organic matter deposition. The model accurately reproduced the seasonal and spatial variability depicted by in-situ estimates of benthic nutrients and oxygen fluxes in the BS-NWS. Outputs were used to review the role of the benthic component in BS biogeochemical cycles. The multi-decadal simulations, enabled by the low computational requirements of the benthic-pelagic coupling approach, revealed an inertial component in the dynamics of eutrophication resulting from the accumulation of organic matter during the years of important nutrient loads. This refined resolution of the BS-NWS biogeochemistry allowed us to study the phenomenon of seasonal hypoxia, which is believed to have played a part in the sudden collapse of the fisheries stocks in the late 80s. An index H, combining the spatial and temporal extension of the seasonal hypoxic event, was proposed to quantify the annual intensity of hypoxia as a pressure on benthic communities. We have shown that hypoxia was first triggered in the late 70s by high nitrogen loads, and sustained by sedimentary organic matter accumulation after a rapid reduction of these loads in the 90s. After 2000, warmer summers again led to a increase of the H-index, by entraining hypoxic events of smaller spatial extension but increased duration. A practical relationship distinguishing the impacts of eutrophication and climatic drivers was proposed to assess the effect of their projected values on the future intensity of hypoxia. [less ▲]

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See detailÉtude de l’entomofaune au sein d’associations culturales comprenant le Safoutier (Dacryodes edulis) dans le Haut-Ogooué (Gabon).
Poligui, René Noël ULg

Doctoral thesis (2014)

Le safoutier Dacryodes edulis (Burseraceae) est un important arbre fruitier originaire du Golfe de Guinée. Ses fruits (safou) sont nutritionnels, beaucoup consommés et commercialisés sur les marchés ... [more ▼]

Le safoutier Dacryodes edulis (Burseraceae) est un important arbre fruitier originaire du Golfe de Guinée. Ses fruits (safou) sont nutritionnels, beaucoup consommés et commercialisés sur les marchés urbains d’Afrique centrale et sur les marchés africains d’Europe, générant des revenus substantiels aux producteurs et aux commerçants. Le safoutier est susceptible d’apporter des revenus considérables aux économies des pays d’Afrique centrale. Cependant, malgré cette importance alimentaire et économique, il existe très peu d’études sur le safoutier au Gabon, et ses ravageurs sont peu connus dans toute son aire de culture. La présente étude a donc été entreprise pendant les saisons de floraison et de fructification de cet arbre, d’Août à Décembre 2009 à 2011. Le principal objectif était d’évaluer l’entomofaune fréquentant le safoutier au sein des agroécosystèmes du Gabon. Des techniques complémentaires de surveillances entomologiques ont été utilisées, à savoir les pièges jaunes et les observations visuelles, en zones rurales et urbaines. L’étude révèle l’existence une typologie culturale constituée de jardins de case à dominance fruitière, et des jardins de cultures mixtes. Dans les deux systèmes culturaux, D. edulis est l’arbre fruitier majeur. Les abondances et la diversité entomologique ont été déterminées, et les ravageurs et insectes utiles les plus importants ont été identifiés suivant les associations culturales. L’exploitation des diagrammes de relations trophiques (food webs) a permis de caractériser les liens entre les espèces entomologiques et le type de cultures. Les abondances d’insectes sont plus élevées en milieu rural où D. edulis a une densité plus forte qu’en milieu urbain. La diversité d’insectes est similaire entre les deux milieux. L’intérêt et les caractéristiques phénologiques des ravageurs majeurs ont été décrits, et des mesures de lutte biologique ont été préconisées pour leur contrôle. Les ravageurs prédominants de l’agroécosystème rural sont Oligotrophus sp (Diptera: Cecidomyiidae), Pseudophacopteron serrifer Malenovsky (Phacopteronidae) et Selenothrips rubrocinctus Giard (Thysanopera: Thripidae), tandis que Pseudonoorda edulis Maes & Poligui (Lepidoptera: Crambidae), Bactrocera invadens Drew Tsuruta & White (Diptera: Tephritidae) et Physophoropterella bendroiti Poppius (Hemiptera: Miridae) sévissent prépondéremment dans l’agroécosystème urbain. Apis mellifera andansoni Latreille (Apidae) est la principale espèce pollinisatrice, en milieu urbain. Pseudonoorda edulis a été le ravageur le plus dommageable des fruits du safoutier, et des informations de base sur sa prévalence, sa biologie et ses caractéristiques morphométriques ont été fournies dans ce travail. Ces résultats apportent une meilleure connaissance des ravageurs et pollinisateurs de D. edulis au Gabon. Des études ultérieures devraient être conduites sur un environnement plus large de la culture, mais surtout cibler la recherche des mesures de contrôle biologique de P. edulis. [less ▲]

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See detailEtude du recyclage de l'eau résiduaire dans la flottation des minerais oxydés cuprocobaltifères du gisement de Luiswishi
Shengo Lutandula, Michel ULg

Doctoral thesis (2014)

The present work aims at improving practices in the management of wastewater from flotation of ores in the Katanga province and suggests the recycling considering its advantages on the environment ... [more ▼]

The present work aims at improving practices in the management of wastewater from flotation of ores in the Katanga province and suggests the recycling considering its advantages on the environment safeguarding, the sustainable management of hydric resources and the economy of flotation reagents standpoint. It focuses on the determination of the best process water-recycling rate in flotation of copper - cobalt oxidised ores from the Luiswishi deposit and on the explanation of phenomena implicated in the depression of malachite and heterogenite in the recycled water presence. The studied ores have been sulphidised (NaSH) prior to flotation with KAX using the process water recovered from the industrial effluents and a Lab scale replication of the New Concentrator in Kipushi (NCK) flow sheet to simulate the full-size plant operations. The following methodological approach has been adopted: • The lab flotation tests of the pulps originating from the NCK grinding circuit while varying the proportion of the recycled process water added to the feed water in view to determine the proportion which gives a concentrate grading at least 2% Co at the recovery of 80% and at least 7% Co at the recovery of 60% respectively at the rougher and cleaner stages; • The study of the effects from the recycled water chemical components on flotation of malachite and heterogenite through flotation of the studied ores in the presence of S2O32-, SO42-, HCO3-, Ca2+ and Mg2+ introduced in the feed water (demineralised water) through dissolution of their analytical graded-salts and based on the follow-up of the Cu-Co recovery and the roughing flotation concentrates mineralogical analysis by the polarised light microscopy, the X- rays diffraction and the scanning electron microscopy; • The study of the behaviour of malachite and heterogenite based firstly on electrochemical investigations of the pulp (pH, Eh, Es and DO), the leaching tests and sulphidisation of malachite and heterogenite with NaSH in presence of S2O32-, SO42- and HCO3. Secondly, based on thermodynamical calculations for the establishment of the Pourbaix diagrams of the systems Cu(Co-Cu) – Chemical species – Water at 25 °C and the Drift spectroscopic analysis (4000 à 400 cm-1) of malachite after sulphidisation with NaSH and agitation with KAX in the presence of S2O32-, SO42- and HCO3-. The obtained results have shown that the process water recycling is successful when 20% of the recycled water is added to the feed water since one obtains a concentrate grading 2% Co at the recovery of 80% at the rougher stage. However, considering the significant drops in the grade and the recovery of cobalt in the concentrate observed at the cleaner stage, a proportion of 10% has been suggested as optimal for the overall flotation circuit because 82% cobalt were recovered at rougher stage bringing at the cleaner stage a concentrate grading 9.5% Co at the recovery of 63%. Beyond 10%, the process water recycling has proved detrimental to flotation efficiency owing to the build-up of chemical species (S2O32-, SO42-, HCO3-, Ca2+, Mg2+ and Cl-) in the feed water, which becomes corrosive and scaling leading to depression of malachite and heterogenite. This depression results from an increase in the valuable minerals hydrophilicity boosted-up by their strong dissolution in water in the presence of S2O32-, SO42 and HCO3- leading to alterations in their surface properties and the exaggerated liberation of copper and cobalt ions in solution responsible for the overconsumption of NaSH and KAX. [less ▲]

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See detailVariabilité morphologique, génétique et chimique de Cananga odorata [Lam.] Hook.f. & Thoms. en vue de l'amélioration qualitative de la production de l'huile essentielle d'ylang-ylang dans les îles de l'Océan Indien
Benini, Céline ULg

Doctoral thesis (2014)

Summary: Cananga odorata (Lam.) Hook f. & Thomson forma genuina (Annonaceae) commonly called ylang-ylang is an essential oil tree used in the preparation of cosmetics. Despite this plant is an ... [more ▼]

Summary: Cananga odorata (Lam.) Hook f. & Thomson forma genuina (Annonaceae) commonly called ylang-ylang is an essential oil tree used in the preparation of cosmetics. Despite this plant is an indispensable source of incomes for the producing islands, and despite its essential oil is valued by the cosmetic industry, only few studies have been conducted. Ylang-ylang essential oil sector is dying and conservation and valorization strategies are urgently needed to preserve it. During this thesis, we tried to gather the necessary data to achieve this goal. We thus characterized the variability of ylang-ylang at morphological, genetic and chemical levels. This study revealed an important variability in the chemical composition of ylang-ylang essential oil in the study area. In order to suggest valorization and conservation strategies tailored to the current context, we needed to know the causes responsible for the chemical polymorphism. These causes are to be found probably in the environmental variability. Indeed, the genetic structure only revealed few consistencies with the chemical polymorphism. It would be though wiser to further investigate these two potential causes of the chemical variability of ylang-ylang as our study is pioneer in this field. On the basis of the data collected, we then proposed a market-oriented valorization of the genetic and chemical diversity (uniformity of the quality and the composition of ylang-ylang essential oils, raw material sources and quality labels). In terms of genetic and chemical conservation, we propose a conservation strategy mainly based on an on-farm conservation in plantation. We also propose integrated valorization strategies of the on-farm conservation (direct sales and tourism). [less ▲]

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See detailDetermination of the relationship between foam morphology and electrical conductivity of polymer/carbon nanotube nanocomposite foams
Tran, Minh Phuong ULg

Doctoral thesis (2014)

The lightweight of porous nanocomposites makes them attractive materials for various applications such as thermal and sound barriers, shock absorbers, insulation, packaging, and their porous structure is ... [more ▼]

The lightweight of porous nanocomposites makes them attractive materials for various applications such as thermal and sound barriers, shock absorbers, insulation, packaging, and their porous structure is very interesting in bone tissue engineering. Moreover, the incorporation of appropriate carbonaceous nanoparticles into polymeric foams contributes to the reinforcement of their mechanical performances but also renders them electrically conductive, consequently extending their potential interest in electromagnetic shielding (EMI) and electrostatic discharge (ESD) applications for instance. In this PhD thesis, we aim at designing various polymeric foams containing a conductive nanofiller (carbon nanotubes) and to identify the main morphological parameters (pore size, cell density, cell wall thickness,…) that affect and govern the final properties of the foams. In this work, the electrical conductivity of the foams is the main property investigated because it is governing their performances as materials for EMI absorbers, the main application targeted in this work. These important morphology/electrical conductivity relationships would indeed be very useful to guide the foam development towards the material with the best performances for the targeted applications. Two different foaming methods are used in this work: (i) the supercritical CO2 (scCO2) foaming technology and (ii) the freeze-drying process. The first technique enables to produce isotropic foams with spherical closed cells structures and the second one, oriented anisotropic foams with cylindrical open cells. The variation of the foaming parameters allows preparing foams with a large panel of morphologies required for the establishment of the structure/properties relationships. In parallel to this main objective, an improvement of the overall conductive performances of the nanocomposites foams is also investigated through the optimization of the foam morphology and the content in conductive nanofillers. [less ▲]

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See detailDe l'écologie d'un discours heuristique d'acculturation à l'algèbre linéaire
DUNIA MWATI, Adrien

Doctoral thesis (2014)

ABSTRACT : Our research examines the sustainability of an acculturation heuristic discourse to Linear Algebra, prototypical gradual development of this discipline in a dialectical process with elementary ... [more ▼]

ABSTRACT : Our research examines the sustainability of an acculturation heuristic discourse to Linear Algebra, prototypical gradual development of this discipline in a dialectical process with elementary geometry. Our theoretical frameworks are borrowed from mathematics Didactic : mainly, Theory of Didactic Situations by Brousseau and Anthropological Theory of Didactics by Chevallard. These theories have enabled us to problematize the studied issue and make it a teaching "phenomenon" by giving intelligibility to the observations in a way that they are interpreted in a falsifiable hypothesis ( in Popper's sense ) which may integrate them all . In this context, the strict meaning given by Lakatos to heuristic speech has been broadly extended in terms of fundamental situation and praxeologies “modeling” according to Job and Schneider. A rational reading of historical and epistemological development of linear algebra then allowed us to build a "reference epistemological model" not only allowing us to answer to the question: "what is it to do linear algebra ?", but also to legitimize the referent heuristic discourse that served us as “phénoménotechnique”. Considering that our study is well marked, we have experimented in "secondary" and "university" institutions a heuristic device based on some selected aspects of the referent heuristic discourse. The analysis of observable that empirical work has identified has led us to identify several factors that combine to determine the ecological fragility of this speech and are at different levels of scale didactic codetermination (by Chevallard) : - The institutional variation of the curriculum of secondary education part in relation to linear systems. Including an emphasis on a resolution systems contract at the expense of their discussion, with a focus placed on the substitution method ; little technological discourse on the principles of equivalence systems and no intelligibility in terms of beams ; little work on equations as constraints with an impact on the lack of connection between the solution space of a system and the number of "independent" constraints, and finally, no ecological niche for the study of systems due to fragmentation of knowledge involved in multiple chapters. - The constraints inherent in the process of didactic transposition in terms of depersonalization and “désyncrétisation” of the knowledge but also in terms of progress in teaching time or chronogenesis. - Constraints related to teaching : a teacher accommodation to a socio-constructivist paradigm which appears as disguised exposition (ostension) and some ineffective activities ; a university pedagogy marked by “applicationnisme”, protectionism and a timing organization that puts theory on a pedestal where it is no longer in question. - An allegiance to the "mathematical" institution that is manifested, for instance, by some emblematic gestures linked to the mathematic rigor and which do not have great functionality. - Finally, an influence of the work of mathematicians on the didactic transposition, in the era of modern mathematics, which still inspires today didactic way, impeding (or being an obstacle for) linear algebra construction in dialectic with the geometry. The selected scenario for the role of interpretive hypothesis articulating these factors questions, in turn, all our education system which is too inspired by deductive theories in their completed text application. [less ▲]

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See detailLa discipline scolaire "français" : du questionnement identitaire à la conscience disciplinaire. Panorama sur les zones avancées de la francophonie et gros plan sur le cas particulier de l'enseignement du français au secondaire supérieur en Fédération Wallonie-Bruxelles
Van Beveren, Julien ULg

Doctoral thesis (2014)

Après avoir envisagé l'introduction de l'approche par compétences et l'élargissement du corpus des supports d'apprentissage du cours de français comme deux des causes possibles de la crise identitaire que ... [more ▼]

Après avoir envisagé l'introduction de l'approche par compétences et l'élargissement du corpus des supports d'apprentissage du cours de français comme deux des causes possibles de la crise identitaire que nous semble traverser cette discipline scolaire, nous nous sommes livré à l'analyse d'un grand nombre de livraisons de la revue de l'Association internationale des chercheurs en didactique du français, afin de nous interroger sur la rareté des publications ayant trait à la discipline scolaire "français" dans son ensemble. Dans la troisième partie de notre thèse, nous nous sommes penché sur la notion de discipline scolaire et sur quelques syntagmes qui y sont liés, avant de nous focaliser sur l'enseignement-apprentissage du français, au secondaire supérieur, en Fédération Wallonie-Bruxelles. Ajoutons que c'est surtout selon la perspective du didacticien-formateur que nous avons analysé cet enseignement-apprentissage. [less ▲]

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See detailSpace-variant optical phase retarders in liquid crystal polymers and their applications
Piron, Pierre ULg

Doctoral thesis (2014)

During the last decade, extensive investigations were performed to achieve optical phase retarders with a space-variant orientation of their fast axis. These retarders present unique behaviors and they ... [more ▼]

During the last decade, extensive investigations were performed to achieve optical phase retarders with a space-variant orientation of their fast axis. These retarders present unique behaviors and they can be used for several applications such as polarization analysis, beam splitting, phase mask coronagraphy, optical tweezers … The present thesis is dedicated to the development of space-variant retarders made out of liquid crystal polymers recorded by polarization holography. The liquid crystals define the fast axis orientation of the retarder. Polarization holography is based on the superimposition of differently polarized beams to achieve the electric field required to properly align the liquid crystals without mechanical action. In the present work, we start with an introduction about the space-variant retarders, their characteristics and current recording methods, which usually require mechanical action. In the second chapter, polarization holography and several simple examples are presented as well as the liquid crystal polymers, their generic recording process and the first prototypes. In chapter three, the first application that we developed is exposed. It consists in a polarization analysis method based on a retarder characterized by a variation in one dimension of its fast axis orientation. The principle of the method, numerical simulations and the first results are exposed. Chapter four cares about the second application based on a separator of polarization state. The mathematical model and its application to shearography are exposed. In chapter five, another kind of retarders is introduced. These retarders are characterized by a rotation of their fast axis along the center of the retarder. Their properties, the recording systems and the first prototypes are detailed and analyzed. In the last chapter, the application of our retarder to coronagraphy is presented and their performances are computed for different configurations based on experimental constrains. Finally, we conclude with the improvements of our applications and future uses of these retarders. [less ▲]

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See detailContribution à l’amélioration de l’épidémiosurveillance des maladies animales en Afrique francophone de l’Ouest et du Centre
Ouagal, Mahamat ULg

Doctoral thesis (2014)

Livestock is an important source of income in most developing countries. In Africa, it often makes up 10% to 20% of the gross national product at level. One of the major constraints to the development of ... [more ▼]

Livestock is an important source of income in most developing countries. In Africa, it often makes up 10% to 20% of the gross national product at level. One of the major constraints to the development of this sector is animal diseases, which sometimes generate significant economic losses with social consequences that are often very burdensome for farmers. They restrict trade between countries. Reducing the impact of these constraints necessarily involves the prevention and the control of diseases. For this purpose, an adequate knowledge of the epidemiology of the diseases is a prerequisite to define a strategy for their prevention and/or the design of appropriate monitoring measures. One of the essential tools of production remains the epidemiological information network for the surveillance of animal diseases. It is also a tool for decision in international trade involving livestock products. For this purpose, its effectiveness is a guarantee for its credibility. An effective network system must be well organized, meet scientific standards and satisfy the efficiency characteristics which are sensitivity, specificity, acceptability, responsiveness and cost. In west and central Africa, epidemiological surveillance networks of animal diseases are mostly created in the 1990s through the Pan African Program for the Control of Epizootics. A 2004 assessment carried out by this program revealed that these networks are at different stages and found weaknesses in their efficiency. To contribute to the improvement of these systems, an analysis of some performance parameters of these networks has been conducted and suggestions for improvement were made. To achieve this overall objective, the following specific objectives were listed: (i) analyze the technical and functional organization of epidemiological surveillance networks in West and Central Africa; (ii) compare the effectiveness of active surveillance and passive surveillance, the two main monitoring methods used by the networks in West and Central Africa using the case study of the epidemiological surveillance network, in Chad, namely REPIMAT; (iii) assess the sensitivity of an epidemiological surveillance network from an approach based on prevalence of a disease such as Foot and Mouth Disease; (iv) develop performance indicators for regular monitoring of the epidemiological surveillance network for animal diseases in West and Central Africa, again by taking the case of REPIMAT; and finally, (v) estimate the cost incurred by an epidemiological surveillance network in West and Central Africa, for example the REPIMAT. Each of these specific objectives leads to a specific study of which results are presented below: Organization of epidemiological surveillance networks in West and Central Africa The survey on technical and institutional organizations networks in west and central Africa was organised on the basis of a written questionnaire. It involved nine networks of which five were in West Africa (Senegal, Burkina Faso, Ivory Coast, Togo, Guinea) and four in Central Africa (Cameroon, Central African Republic, Democratic Republic of Congo and Chad). The results of this survey showed that the oldest epidemiological surveillance network is that of Chad, REPIMAT. There are more similarities than differences between these networks. In general, network monitoring of animal diseases in west and central Africa are technically and institutionally well formalized. The establishment and operation of the networks surveyed are mainly financed by foreign aid. In general, these are epidemiological surveillance networks that monitor several diseases. All countries surveyed have a central national laboratory for the analysis of samples collected. However, only four countries (Cameroon, Côte d'Ivoire, Guinea and Senegal) can make a diagnosis of all diseases selected for monitoring. The laboratories are considered as partners with surveillance networks in most of the countries surveyed. All networks use the PID/ARIS for data management. In addition to the latter, countries such as Guinea, DRC, Senegal and Chad use a national database developed with Access®. On average, 26% of veterinary stations on the total networks surveyed are involved in the monitoring. This proportion varies from 7% to 91%. However, insufficient diagnostic capacity of laboratories and inadequate operational steering committees are the two main weaknesses of the networks concerned with this survey. Comparison between active and passive surveillance within the network of epidemiological surveillance of animal diseases in Chad The comparison between active and passive surveillance involved 106 REPIMAT surveillance stations randomly divided into 52 active surveillance stations and 54 passive surveillance stations. Vaccination status of nine diseases and their respective prevalence levels are monitored by the network. A work plan was developed for each station. The stations of active surveillance make monthly visits to four herds (villages) to look for monitored diseases and also organise four information meetings with farmers how to react in case of suspicion of the monitored diseases. Passive surveillance stations only organise, monthly, four information meetings with farmers. Suspicions in each station are recorded on a specific form developed for each disease. The agent mentions if the suspicion is performed following a breeder call, a visit from herds or a sensitization meeting. Monitoring lasted 24 months. The results of this study showed that regardless of the type of surveillance, diseases monitored with the exception of rare diseases (Rinderpest, and Rift Valley fever) are reported by the monitoring agents. However, we note that the number of calls recorded following suspicions of farmers (41%) was significantly higher (p <0.05) than suspicions made during visits to herds (30%) or in meetings (29%). For moderately prevalent diseases, the suspicions are mainly calls farmers (77%) and regardless of the type of monitoring (73% for active surveillance and 84% for passive surveillance). On the other hand, for FMD, a disease with high prevalence, 37% of suspicions are recorded by visiting farms. Overall, no significant difference was observed between the types of surveillance because of a low rate of disease onset during sensitization meetings by the active surveillance stations. Passive surveillance stimulated by awareness meetings appears to be a mode for surveillance in the conditions of Chad and cheaper. However, for rare diseases, the specific methods of active surveillance (such as, for example, sentinel flocks) seems preferable. Evaluation of the sensitivity of the animal disease epidemiological surveillance network for Foot and Mouth Disease in Chad Evaluation of the sensitivity of the animal disease epidemiological surveillance network for Foot and Mouth Disease in Chad The study on the network sensitivity was carried out in REPIMAT by taking the surveillance of FMD as an example. FMD is the disease most frequently suspected by REPIMAT. However, the reporting of cases is limited to clinical suspicion. The samples for the purpose of laboratory diagnostic for confirmation of these suspicions are not made. In order to assess the sensitivity of REPIMAT for this disease, a serological survey was conducted in eight of the nine regional delegations with the highest cattle population of the country. The samples were analyzed by the National Reference Laboratory for FMD in Brescia (Italy) with the support of the European Commission action against FMD. The 3ABC and SP-ELISA tests were used for the detection of antibodies and the serotype of the virus. The number of FMD suspicions reported within the network was compared with the seroprevalence. Epidemiological information on the disease, including the circulating serotypes in Chad, was also provided. A total of 796 cattle sera were collected. The seroprevalence rate at individual level was 35.6% (95% CI: 32.2 to 39.0) and that at the herd level was 61.9% (95% CI: 51.9 to 71.2). A strong correlation was observed between the estimated prevalence and number of clinical suspicions reported within REPIMAT. The disease is present in all livestock regional delegations surveyed with a high prevalence in the delegations located in the south, the wettest area, and where cross-border movements are the most important. Serotypes A, O, SAT1and SAT2 were identified. Development of operating performance indicators of Chad epidemiological surveillance network for animal diseases: REPIMAT The maintenance and effectiveness of a disease monitoring system requires regular evaluation to identify timely deficiencies that may occur. For this purpose, the performance indicators are essential tools. One approach for developing performance indicators as well as their application in the operation of 43 monitoring stations REPIMAT was carried out. An analysis of the objectives and operation mechanism of REPIMAT allowed retaining three main components, namely the field workers, the animation cell and the laboratory. The activities of each of these components were listed. The analysis of the outcomes of these activities resulted in the development of the performance indicators that can be used in the operation of REPIMAT. The application of these indicators has highlighted the weaknesses of each component. Estimated cost of a network for animal diseases epidemiological surveillance in Central Africa: the case of Chad network In sub-Saharan Africa, most of the networks for epidemiological surveillance of animal diseases were temporarily financed by external aid. The sustainability of such decision support tools should have been insured by national public funds. The objective of this study was to estimate the costs involved in running an animal disease epidemiological surveillance network by taking the example of such network in Chad (REPIMAT) and its weight in the state budget. These costs were then compared to those of other epidemiological surveillance in West Africa networks. The results of this study showed that the total annual operating and implementing cost of REPIMAT is estimated at € 666 349 (437 096 291 FCFA) for the entire system comprising 106 monitoring stations constituting the local level, 26 livestock sectors, nine regional livestock delegations representing the intermediate level and an animation cell constituting the central level. This cost represents only 3% (2% of fixed costs and 1% of variable costs) of the budget allocated by the Chadian Ministry of Livestock. Fixed costs (72%) weighed more than variable costs (28%) regardless of the levels of intervention. This estimate is similar to the estimated costs of epidemiological surveillance networks in Benin, Ghana, Mauritania and Senegal. Considering only the variable costs (operation), the annual cost of operating a surveillance station, the most important entity in the system was only 932 € or 611 352 FCFA. The surveillance cost is mainly related at the local level (surveillance stations) and intermediate level (livestock sectors and regional livestock delegations) to the cost involved in health surveillance as well as the equipment it requires. This thesis allowed to analyze some parameters of effectiveness of a surveillance network for animal diseases including general organization, type of surveillance, sensitivity, cost and to develop a tool for continuous monitoring of operating a network. It is difficult to meet all the efficiency criteria of an animal disease surveillance network, however, the few parameters studied which are interrelated will help if they are used properly to improve the efficiency of an epidemiological surveillance system of animal diseases in sub-Saharan Africa. [less ▲]

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See detailMathematical modeling od the mitral valve. From local to global hemodynamics
Paeme, Sabine ULg

Doctoral thesis (2014)

Mitral valve dysfunction is a relatively common heart disease which typically requires mechanical valve replacement, with consequent high social and economic costs. More specifically, ischemic mitral ... [more ▼]

Mitral valve dysfunction is a relatively common heart disease which typically requires mechanical valve replacement, with consequent high social and economic costs. More specifically, ischemic mitral insufficiency following myocardial infarction has a dynamic behavior that can lead to failure in its detection in certain patients, creating a situation with increased risk of morbidity and mortality. Improving the tracking and the control of valvular pathologies is therefore crucial, as it offers significant opportunities to improve care, costs and prognosis for patients with this disease. To study heart and cardiac valve dysfunction, cardiologists need information about detailed pressure and flow dynamics around and through the valves, atria and ventricles. However, non-invasive information about pressure is currently limited to indices at specific times and invasive catheterization data, which is more traumatic for the patient, is not usually routinely available. One alternative to this involves mathematical modeling of the cardiovascular system which offers a non-invasive and inexpensive way of studying cardiac and circulatory dynamics. This is particularly beneficial where detailed, continuous measurements may not be practicable. This study consisted of the development of a multi-scale closed-loop model of the cardiovascular system that accounted for progressive mitral valve aperture area over the entire cardiac cycle. This multi-scale model, which included detailed mitral valve and left atrium models, was tested over a range of physiological situations and clinical data. The goal was to validate the model’s ability to reproduce clinically measured physiological and pathophysiological behavior in a manner that would enable a model to be made patient-specific using available data. The resulting model was designed to be made patient-specific, and thus capture and reproduce the patient’s unique hemodynamic state on both global and local scales. In particular, it was shown to provide significant information about the patient’s mitral valve dynamics and the detailed flow dynamics and pressure around it. These data are not currently available without extensive, invasive measurements, and this therefore represents a significant step forward in model-based sensing and diagnosis. It is hoped that the model and methods developed in this study will be a powerful tool in assisting medical teams in investigating, tracking, diagnosing and controlling the cardiovascular system. More specifically, the mitral valve, as well as other similar valves, could be directly monitored to improve the diagnosis, costs and prognosis of valvular dysfunction. Furthermore, the overall results justify detailed in vivo animal experiments to thoroughly validate these models and methods in advance of clinical trials. [less ▲]

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See detailProtein Structural Annotation: Multi-Task Learning and Feature Selection
Becker, Julien ULg

Doctoral thesis (2014)

Experimentally determining the three-dimensional structure of a protein is a slow and expensive process. Nowadays, supervised machine learning techniques are widely used to predict protein structures, and ... [more ▼]

Experimentally determining the three-dimensional structure of a protein is a slow and expensive process. Nowadays, supervised machine learning techniques are widely used to predict protein structures, and in particular to predict surrogate annotations, which are much less complex than 3D structures. This dissertation presents, on the one hand, methodological contributions for learning multiple tasks simultaneously and for selecting relevant feature representations, and on the other hand, biological contributions issued from the application of these techniques on several protein annotation problems. Our first methodological contribution introduces a multi-task formulation for learning various protein structural annotation tasks. Unlike the traditional methods proposed in the bioinformatics literature, which mostly treated these tasks independently, our framework exploits the natural idea that multiple related prediction tasks should be designed simultaneously. Our empirical experiments on a set of five sequence labeling tasks clearly highlight the benefit of our multi-task approach against single-task approaches in terms of correctly predicted labels. Our second methodological contribution focuses on the best way to identify a minimal subset of feature functions, {\em i.e.}, functions that encode properties of complex objects, such as sequences or graphs, into appropriate forms (typically, vectors of features) for learning algorithms. Our empirical experiments on disulfide connectivity pattern prediction and disordered regions prediction show that using carefully selected feature functions combined with ensembles of extremely randomized trees lead to very accurate models. Our biological contributions are mainly issued from the results obtained by the application of our feature function selection algorithm on the problems of predicting disulfide connectivity patterns and of predicting disordered regions. In both cases, our approach identified a relevant representation of the data that should play a role in the prediction of disulfide bonds (respectively, disordered regions) and, consequently, in protein structure-function relationships. For example, the major biological contribution made by our method is the discovery of a novel feature function, which has - to our best knowledge - never been highlighted in the context of predicting disordered regions. These representations were carefully assessed against several baselines such as the 10th Critical Assessment of Techniques for Protein Structure Prediction (CASP) competition. [less ▲]

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See detailNanobodies as tools to investigate the mechanism of aggregation of chimeric proteins made by the insertion of polyglutamine stretches into the beta-lactamase BlaP
Pain, Coralie ULg

Doctoral thesis (2014)

Among the neurodegenerative amyloidoses, ten disorders, referred to as polyglutamine (polyQ) diseases and including Huntington's disease and several spinocerebellar ataxias, are associated with ten ... [more ▼]

Among the neurodegenerative amyloidoses, ten disorders, referred to as polyglutamine (polyQ) diseases and including Huntington's disease and several spinocerebellar ataxias, are associated with ten proteins within which a polyQ tract is expanded above a threshold of typically 35-45 glutamine residues. Such expanded polyQ tracts lead to the aggregation of the host protein into amyloid fibrils that accumulate in the nucleus of some populations of neurons; these aggregates or some of their precursors are thought to contribute to neuronal death. So far, no preventive or curative treatment exists for these devastating pathologies. While the expansion of the polyQ tract above the threshold is the determinant factor for aggregation, recent studies suggest that non-polyQ regions of these proteins can play a significant role, either preventative or facilitative, in the aggregation process. The general principles governing the complex interplay between the role of the expanded polyQ tract and the role of the non-polyQ regions in the aggregation process are not well understood yet. In order to develop therapeutic strategies, it is important to better understand this complex interplay. To contribute to this aim, we have engineered chimeric proteins via the insertion of polyQ repeats of various lengths (23, 30, 55 and 79Q) into two sites (197 and 216) of the BlaP beta-lactamase from Bacillus licheniformis 749/C. The properties of these chimeric proteins recapitulate the characteristic features of the disease-associated polyQ proteins, i.e. (i) there is a minimum number of inserted glutamines (threshold) required to trigger the aggregation of the chimeras into amyloid fibrils, and (ii) above the threshold, the longer the polyQ tract, the faster the aggregation. Interestingly, for the same polyQ length, the chimeras with insertions in position 216 have an increased propensity to form amyloid fibrils compared to their counterparts with insertions in position 197. These findings highlight the strong influence of the overall protein context on aggregation triggered by expanded polyQ tracts. This thesis addresses the use of the variable domains of camelid heavy-chain antibodies, referred to as nanobodies or VHHs, as structural and mechanistic probes to better understand the different aggregating properties of the two sets of BlaP-polyQ chimeras (197 and 216). We have also performed limited proteolysis experiments and transglutaminase-mediated reactions on the monomeric form of the BlaP-polyQ chimeras to further investigate the effects of the polyQ insertions on the structure and dynamics of the BlaP moiety, as well as the structure of the polyQ tract itself. From the blood of a llama immunised with BlaP197(Gln)55, we isolated more than 60 VHHs specific to the BlaP-polyQ chimeras. Twenty eight of them were produced, purified and characterised. These VHHs were found to be all specific to the BlaP moiety and could be classified into four different groups recognising distinct epitopes on the surface of BlaP. One representative VHH of each group (i.e. cAb-A3S, cAb-H7S, cAb-F11N and cAb-G10S) was selected as probe to investigate the mechanism of aggregation of the BlaP-polyQ chimeras. The epitope of three of them was determined by X-ray diffraction and/or by NMR spectroscopy. Although they recognise distinct epitopes and exhibit different affinities for BlaP, the binding of the four VHHs significantly slows down the aggregation of all the BlaP-polyQ chimeras investigated (i.e. BlaP197(Gln)55, BlaP197(Gln)79 and BlaP216(Gln)79). The extent of inhibition depends however on the chimera and on the experimental conditions. We show that the inhibition of the aggregation of BlaP197(Gln)55 and BlaP197(Gln)79 upon binding of the four VHHs is correlated with the stabilisation of their native state. In the case of BlaP216(Gln)79, the extent of inhibition could not be only correlated to the stabilisation of its native state; the location of the epitope of the VHH is instead also determinant. This observation demonstrates that the lower thermodynamic stability of BlaP216(Gln)79 is not the unique factor responsible for its increased aggregation propensity. It also further highlights the complexity of the aggregation mechanism of polyQ proteins and the strong influence of the non-polyQ regions on the amyloid fibril formation triggered by the expanded polyQ tract. All together our results suggest that antibodies or antibody fragments raised against the non-polyQ regions of polyQ proteins associated with diseases could constitute a relevant therapeutic strategy. They also further demonstrate the power of nanobodies as probes to get a deeper knowledge of the underlying mechanisms of amyloid fibril formation. The preliminary limited proteolysis and transglutamination experiments obtained suggest that the polyQ tracts are all flexible, except that of 23 glutamines inserted in position 197 of BlaP, which seems to be more rigid than the others. The results obtained confirm that, globally, the structure of BlaP is not significantly modified by the insertions while the 216 chimeras seem more dynamic than the 197 chimeras. [less ▲]

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See detailContribution à l'étude de la réponse immune au cours d'une infection à Microsporum canis et établissement d'un modèle murin de dermatophytose
Cambier, Ludivine ULg

Doctoral thesis (2014)

Les dermatophytoses (ou « teignes ») sont des mycoses cutanées superficielles provoquées par des champignons filamenteux, appelés dermatophytes, affectant les animaux et l’homme. Microsporum canis est un ... [more ▼]

Les dermatophytoses (ou « teignes ») sont des mycoses cutanées superficielles provoquées par des champignons filamenteux, appelés dermatophytes, affectant les animaux et l’homme. Microsporum canis est un dermatophyte zoophile dont l’hôte naturel est le chat. Il touche principalement les carnivores domestiques et est un agent fréquent de zoonose. Les dermatophytes envahissant les structures kératinisées de l’épiderme, de nombreuses études ont porté sur la caractérisation des protéases sécrétées comme facteurs de virulence potentiels. Cependant, peu de recherches ont été consacrées aux mécanismes impliqués dans la mise en place de la réponse immune anti-dermatophytes. Il est couramment admis que la réponse immune protectrice lors d’une dermatophytose est une réponse à médiation cellulaire impliquant les lymphocytes de type Th1 et caractérisée par une réaction cutanée d’hypersensibilité de type retardé (Delayed Type Hypersentivity, DTH). Un constituant sécrété de M. canis correspondant au surnageant de culture du champignon cultivé sur milieu de Sabouraud liquide, appelé surnageant non induit (SNI), provoque des DTH chez le cobaye immunisé après une primo-infection, ce qui suggère que le SNI contient des antigènes potentiellement intéressants pour le développement d’un vaccin. Le cobaye est le modèle animal le plus utilisé pour étudier l’immunologie des dermatophytoses. Cependant, la quasi absence d’outils génétiques et immunologiques dans cette espèce ne permet pas d’étudier la réponse immune induite lors de dermatophytoses de manière satisfaisante. La mise au point d’un modèle murin de dermatophytose permettrait de pallier tous ces inconvénients. Au cours d’une dermatophytose à M. canis, les premières cellules rencontrées par le champignon lors de l’infection sont les kératinocytes qui, suite à l’activation par des composants fongiques, peuvent attirer les polymorphonucléaires neutrophiles (PMN) sur le site d’infection. Ces leucocytes sont, avec les macrophages, responsables in fine de l’élimination du dermatophyte. Cependant, le rôle des PMN dans les mécanismes liés à l’établissement de l’immunité anti-dermatophytes demeure inconnu. L’objectif général de ce travail était de contribuer à l’étude de la réponse immune au cours d’une dermatophytose à M. canis et de mettre au point un nouveau modèle animal de dermatophytose. Pour l’atteindre, trois études ont été réalisées : (1) l’évaluation du rôle des PMN félins dans la mise en place d’une réponse immune protectrice au cours d’une dermatophytose à M. canis, (2) l’évaluation des propriétés protectrices du SNI de M. canis dans un essai vaccinal en utilisant le cobaye comme modèle expérimental et (3) la mise au point d’un modèle murin de dermatophytose pour l’étude de l’immunité anti-dermatophytes. Résumé 2 Les résultats obtenus dans la première étude montrent que les PMN félins produisent des cytokines pro-inflammatoires telles le tumor necrosis factor (TNF)-α, l’interleukin (IL)-1β et l’IL-8 lorsqu’ils sont stimulés par les arthrospores vivantes du champignon ainsi que par des constituants structuraux, représentés par des arthrospores tuées par la chaleur, et sécrétés comme le SNI. De plus, après stimulation pendant 2 ou 4 heures par les arthrospores vivantes et tuées ainsi que par les protéases sécrétées Sub3 et Sub6, disponibles sous forme recombinante dans notre laboratoire, les taux d’ARNm du toll like receptor (TLR)-2 et du TLR-4 étaient augmentés dans les PMN. Ces résultats suggèrent que les PMN félins jouent un rôle dans l’établissement de la réponse immune anti-M. canis en produisant des cytokines pro-inflammatoires et que les mécanismes responsables de cette activation feraient intervenir les récepteurs TLR-2 et TLR-4. Dans la deuxième étude, les résultats indiquent que l’adjuvant monophosphoryl lipid-A (MPLA), dérivé non toxique du lipopolysaccharide et agoniste du TLR-4 a, à lui seul, un effet protecteur partiel chez les cobayes soumis à une épreuve d’infection par M. canis. En effet, les symptômes cutanés observés chez les cobayes ayant préalablement reçu l’adjuvant, étaient moins importants que ceux développés par les cobayes infectés n’ayant pas reçu l’adjuvant. En revanche, le SNI ne semble pas protéger les cobayes d’une infection expérimentale dans cet essai vaccinal. Les résultats obtenus dans la troisième étude démontrent que notre modèle murin de dermatophytose est valide et reproductible, en utilisant Arthroderma benhamiae et Arthroderma vanbreuseghemii. Ce n’est pas le cas avec M. canis. En effet, 100 % et 80 % des souris infectées respectivement par A. vanbreuseghemii et A. benhamiae ont développé des symptômes cutanés typiques de dermatophytose, à savoir de l’érythème, des squames, des croûtes et de l’alopécie alors que seulement 40 % des souris infectées par M. canis ont développé des signes cliniques, par ailleurs très discrets. Le recrutement important de PMN dans la peau des souris infectées par A. benhamiae et A. vanbreuseghemii et le profil cytokinique (transforming growth factor (TGF)-β, l’IL-1β, l’IL-6 et l’IL-22) généré par l’infection suggèrent l’implication de la voie Th17 dans la mise en place de la réponse immune anti-dermatophytes. En conclusion, l’ensemble de ce travail a contribué à élargir nos connaissances sur la réponse immune au cours d’une dermatophytose à M. canis. De plus, un nouveau modèle murin de dermatophytose à A. benhamiae et A. vanbreuseghemii a été mis au point et est approprié pour l’étude de la réponse immune anti-dermatophytes. [less ▲]

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See detailContribution à la compréhension de l'immunopathogénie de l'aspergillose nasosinusale chez le chien
Vanherberghen, Morgane ULg

Doctoral thesis (2014)

Sinonasal aspergillosis is a sever fungal rhinosinusitis mainly affecting large breed dogs in their mid ages. Its most common causal agent is A. fumigatus, a fungus that is largely spread in the ... [more ▼]

Sinonasal aspergillosis is a sever fungal rhinosinusitis mainly affecting large breed dogs in their mid ages. Its most common causal agent is A. fumigatus, a fungus that is largely spread in the atmosphere. As of today, the diagnostic and treatment for this disease remain a challenge for the practicing veterinary doctor. Very little data is available to explain why such a ubiquitous fungus induces a sever rhinosinusitis in otherwise healthy dogs, while other dogs do not present any sign of fungal infection. The authors of a study analysing the expression of mRNA encoding for certain cytokines and chimiokines in the nasal mucosa of SNA affected dogs, propose the assumption that dogs develop a protective immunity (Th1) against A. fumigatus, but that it could be blocked by an excessively intense regulating immunity (massive production of IL-10). Indeed, it is commonly described that in humans affected by invasive aspergillosis, as well as in mice-based models, the production of immunoregulating cytokines (IL-10) should be considered as a sign of the escalation of the sickness and an absence of its remission. The objective of this thesis was to investigate the adaptive immunity reaction of SNA affected dogs based on the assumption that sick subjects develop a protective immunity that is antagonised by a disproportional regulating immunity. Three axes of analysis have been considered to answer this objective. The first looked into the difference of expression and/or production of cytokines and transcriptor factors prototypics of the different adaptative and regulatory immunological paths: Th1 (IFN-γ and Tbet) – Th2 (IL-4 and GATA3) – Th17 (IL-17A and RORc) and Treg (IL-10 and FoxP3) in PBMC of affected and healthy dogs after A. fumigatus stimulation. Secondly, an analysis of genes by microarray has been carried on nasal mucosa biopsies of affected and healthy dogs. Thirdly, the promotor zone of the gene encoding IL-10 in dogs has been analysed by sequencing. This study has been done within three cohortes of dogs: Rottweiler-Labrador and Golden containing affected and healthy dogs. The objective was to investigate, as it is the case in human medicine, the possibility of a genetic modification as a factor susceptible of leading to SNA development. The results of the first study revealed that: (1) the PBMC of half the controls dogs and every affected dogs expressed a relevant overexpression of IFN-γ. This increase was significantly more important within PBMC of affected dogs. The analysis of IFN-γ production in culture supernatants was in accordance with these last observations. A significant increase in the expression of mRNA coding for Tbet was also observed in half of the PBMC of affected dogs. (2) a significant increase in expression of mRNA encoding IL-4 was observed in the PBMC of most of the affected and healthy dogs. This increase was significantly higher in the PBMC of affected dogs than in the healthy dogs. (3) the PBMC of most control and affected dogs also revealed an increase in expression of mRNA encoding IL-17A. This increase was statistically more important in the PBMC of affected dogs than in the healthy dogs. (4) a relevant decrease in mRNA expression encoding IL-10 was observed in the PBMC of more than half of the affected dogs. The expression of the mRNA encoding IL-10 was significantly smaller in the PBMC of affected dogs than in the healthy dogs. The microarray analysis showed that: (1) amongst the 49 overexpressed biological groups, 13 were associated to the immunological or inflammatory process; (2) the nasal mucosa of affected dogs presented an increase in the expression of genes encoding for molecules involved directly (IFN-γ and STAT4) and indirectly (IL-16, CCL3, CCL4, and CXCL10) in the development of protective Th1 immunity, as well as molecules involved in the regulatory branch of the immune response (IL-16 and Ikaros). The sequencing analysis of the promotor region of the gene encoding IL-10 revealed the presence of polymorphisms. Three polymorphisms were observed more frequently in clones belonging to the three studied cohorts, excepted for the clones belonging to SNA affected Rottweiler. The polymorphisms observed in dogs were not similar to those described in humans. The first study showed an increase in the expression of mRNa encoding IFN-γ - Tbet – IL-4 and IL-17A in most of the PBMC of the affected dogs, and a decrease in the expression of IL-10 in comparison with the PBMC of healthy dogs. Similar results were observed in mice repeatedly affected by A. fumigatus. The suggested hypothesis was that an intense Th17 immunity resulted in a massive inflammatory reaction leading to a favourable environment were A. fumigatus was able to proliferate as hyphae. In return, hyphae would lead to the development of a non-protective Th2 immunity. It is tempting to suggest that the same hypothesis could be made for dogs affected by SNA. In order to reinforce this hypothesis, we should compare the expression of the different molecules involved in the Th17 immunity inside the nasal mucosa of affected and healthy dogs. Additionally, we should be running a kinetic study based on the expression of prototypical cytokines in parallel with the analysis of the production of these cytokines in culture supernatants. Ideally these studies should use DC and lymphocytes isolated from the nasal mucosa of affected and healthy dogs. In conclusion, an new hypothesis could be formulated: the possibility that not the overstimulation of the regulatory branch of the immunity response but an overstimulation of the Th17 branch of the immune response could be the cornerstone of the incapacity of dogs to clear from their SNA. The results of the microarray study were partially in accordance to the starting hypothesis. Indeed, the results showed an overexpression of genes involved in in the development of the protective Th1 (IFN-γ, STAT4, IL-16, CCL3, CCL4, and CXCL10) as well as genes involved in the regulatory path of the adaptive immunity (IL-16 and Ikaros). But the results of this study did not show an increase in IL-10. No conclusion could be drawn from these results; indeed, they were only the reflection of a fixed image at a given moment and we cannot consider qPCR results as the exact replica of the production of cytokines in the microenvironment. Nevertheless this study pointed out new possible areas of research. The results obtained after the sequencing of the promotor zone of the gene encoding IL-10 did not show any clear difference between affected and healthy dogs. However, this study was undertaken with a very limited number of dogs. In order to further assess the possibility of a genetic modification as the cornerstone of the development of SNA, more dogs should be analysed and the sequencing analysis should be run in parallel with an ELISA analysis. [less ▲]

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See detailHISTOLOGICAL RESPONSES OF THE SEA ANEMONE A. PALLIDA TO BLEACHING INDUCING STRESSES
Fransolet, David ULg

Doctoral thesis (2014)

Tropical Coral reefs are among the richest and most important ecosystem on Earth. This success would not be possible without the symbiosis established between corals and unicellular algae of the genus ... [more ▼]

Tropical Coral reefs are among the richest and most important ecosystem on Earth. This success would not be possible without the symbiosis established between corals and unicellular algae of the genus Symbiodinium that provide them with photosynthesis-derived carbon. Unfortunately, with the climatic upheaval that we witness today, the long-term survival of coral reefs could be in jeopardy. Massive loss of symbiotic algae, a phenomenon known as coral bleaching, becomes indeed more and more frequent throughout the globe and already urged scientists to study its mechanisms for more than a decade. Their research highlighted the central role of reactive oxygen species in the collapse of symbiosis. They also established that the expulsion of Symbiodinium from its host is mainly operated through the death of the host cell. The ensuing events, although determining the eventual survival of the energetically compromised coral, are however much less detailed. In this work, we decided to investigate these “post-bleaching” events and focused our efforts on the evaluation of cell proliferation and mucocyte number, for the role they may respectively play in regenerative processes and heterotrophic feeding. For this purpose, we worked with the sea anemone model A. pallida in which we analyzed the incorporation of a thymidine analogue (EdU). After preliminary experiments assessing the general repartition and the circadian variations of cellular proliferation in healthy specimens, we conducted a series of bleaching experiments using a variety of stresses. Every treatment, namely cold and darkness, heat and light or exposition to a photosynthesis inhibitor, drastically reduced the Symbiodinium density. This reduction was always accompanied by important histological modifications. In every case, we highlighted an increase in cellular proliferation in both the ectodermis and the gastrodermis as well as an increase in ectodermal mucocyte density. These values returned then to normal as algae that survived the stress progressively repopulated anemones. Further experiments showed that, following bleaching, a small fraction of the newly produced ectodermal cells migrate to the gastrodermis. Along with new gastrodermal cells, they most probably operate a regeneration of the wounded tissue, differentiating into host cells in order to harbor new algae. Another experiment also indicated that a small but significant part of ectodermal newly produced cells might differentiate into mucocytes, therefore explaining their increased density in bleached individuals. We hypothesize that the higher amount of mucus produced, in addition to providing protection against various aggravating stresses, would be a way to efficiently increase the feeding capacity of the bleached cnidarians. This heterotrophic shift would therefore allow a sufficient energy income until full restoration of the symbiosis. This work emphasizes the need to focus more attention on the post-bleaching period, a critical time in which some modifications might be decisive for coral and coral reef survival. [less ▲]

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See detailComplémentation précoce en colostrum de vache Azawak chez la chèvre rousse de Maradi au Niger: effets sur les performances de croissance et de reproduction, et sur la survie au cours de la première année de vie.
Abdou, Harouna ULg

Doctoral thesis (2014)

L’élevage  des  petits  ruminants  représente  au  Niger,  la  ressource  principale  pour  plus  de  6  millions  de   paysans pauvres, vivant avec moins de 1 dollar US par jour. C'est un trésor ... [more ▼]

L’élevage  des  petits  ruminants  représente  au  Niger,  la  ressource  principale  pour  plus  de  6  millions  de   paysans pauvres, vivant avec moins de 1 dollar US par jour. C'est un trésor important qui contribue à la renommée des familles. Selon le recensement général  de  l’agriculture  et  de  l’élevage  (2007),  le   cheptel Nigérien se chiffre à 31 millions toutes espèces confondues dont 11 millions de caprins (36,21 %)  et  9  millions  d’ovins  (30  %). Bien  qu'il  occupe  une  place  de  choix,  l’élevage  des  petits  ruminants  reste confronté à des contraintes dont les principales sont: les sécheresses chroniques et répétitives ayant pour conséquence un déficit alimentaire constant, la pression démographique entrainant une concurrence entre les cultures et les animaux   pour   l’occupation de la terre et enfin les pathologies récurrentes (parasitoses gastro- intestinales, affections digestives) accompagnées le plus souvent par des diarrhées. Par ailleurs, la naissance et le sevrage sont deux périodes critiques pour les jeunes animaux. Si à la naissance, le système immunitaire reste en chantier et par conséquent déficient, au sevrage c'est le changement alimentaire qui peut handicaper la croissance des jeunes. Malheureusement, ils ne reçoivent pas toujours   toute   l’attention   et   la   vigilance nécessaire pour optimaliser leur développement. Dans ce contexte,   il   serait   intéressant   d’étudier   les   solutions   possibles   à   ces   problèmes.   L’utilisation   du   colostrum bovin semble être exploitable dans la mesure où il renferme des éléments nutritifs et antimicrobiens  nécessaires  pour  le  bovin,  mais  également  pour  d’autres  espèces  (caprins,  ovins,  porcs,   homme). Pour cette étude, le choix du colostrum bovin a été guidé aussi par sa disponibilité à la station sahélienne expérimentale de Toukounous au Niger. À priori, l’objectif de cette thèse est de vérifier l'hypothèse d'un effet bénéfique de l'administration du colostrum bovin sur la santé et les performances zootechniques des cabris. Le   premier   chapitre   présente   d’abord   le   milieu   physique   du   Niger,   puis   s’intéresse à quelques caractéristiques  des  animaux  de  l’étude  à  savoir  la  race  bovine  Azawak  et  la  race  caprine  dénommée   chèvre rousse de Maradi. En effet, le zébu Azawak est un animal de taille moyenne (1,3 m au garrot), Dans des très bonnes conditions et en élevage intensif, la vache zébu Azawak peut produire en moyenne  12  litres  par  jour.  Le  rendement  à  l’abattage  va  de  50  à  60%.  Quant  à  la  chèvre  rousse,  elle   est de taille moyenne ou petite (0,55-0,65 m). La durée de lactation est de 3 à 4 mois après la mise bas selon   les   conditions   d’élevage   et   la   production   laitière   annuelle   est   de   150   kg   en   200   jours.   Le   rendement  à  l’abattage  (poids  carcasse)  varie  de  50  à  55%  pour  le  sujet  castré. Le deuxième chapitre est une synthèse bibliographique sur la physiologie de la production et composition chimique du colostrum. Cette revue fait la compilation des informations les plus récentes sur le mécanisme de synthèse du colostrum, son aspect physico-chimique, son importance et enfin les facteurs de variation des composants chimiques de cette première sécrétion mammaire après la mise bas. Le colostrum renferme tous les éléments nécessaires permettant non seulement une protection contre les agressions d ́agents pathogènes, mais également une croissance rapide des jeunes animaux. Le chapitre trois est relatif à la comparaison par méta-analyse de la composition chimique du colostrum de la race bovine Azawak à des données synthétisées de la littérature. Cette étude a guidé le choix  de  l’espèce  dont  le  colostrum  doit  être administré au cours des expériences sur le terrain. Les concentrations  moyennes  d’IgG, IgM, MS, protéines et matières grasses pour la vache Azawak ont présenté des  valeurs  plus  faibles  (P  ˂  0,001) que celles obtenus chez d'autres races, mais il convient de noter des niveaux élevés d'IgA (P > 0,05), de  lactose  et  de  cendre  brute  (P  ˂  0,001). En ce qui concerne les minéraux solubles, les concentrations moyennes de Ca, P, Na et Mg dans le colostrum de bovin Azawak étaient  significativement  plus  élevées  (P  ˂  0,001) que celles de moyennes obtenues à partir des données de synthèse. En conclusion, comparé aux données de littérature, le colostrum de vache Azawak semble être plus pauvre en immunoglobuline, en lipides et en protéines, mais plus riche en lactose et en minéraux.  Il  se  pourrait  qu’il  s’agisse  d’une  adaptation  de  la  race  au  milieu  sahélien. Le  chapitre  quatre  est  intitulé  "l'Effet  de  l’administration  du  colostrum  de  bovin  Azawak  sur  le  profil   plasmatique, la croissance et la survie chez les chevreaux roux". Cette  étude  visait  à  évaluer  l’impact   de  l’administration  de  colostrum  hétérologue  Azawak  sur  le  profil  protéique  plasmatique,  la  croissance   et le taux de survie des chevreaux roux au Niger. Après la naissance et ce, jusqu'à la fin de l'essai, les poids vifs ont augmenté avec le temps dans les deux groupes, mais les valeurs ont été plus élevées dans le groupe colostrum que dans le groupe témoin (+ 1,4 kg à j29, P < 0,001). Dans l'ensemble, le groupe colostrum a présenté un gain moyen quotidien largement supérieur à celui du groupe témoin (P < 0,001). Les concentrations moyennes de fractions plasmatiques obtenues à l'âge de 10 et 30 jours ont atteint des valeurs plus élevées dans le lot colostrum que dans le lot contrôle. A 10 jours, le groupe colostrum a tendu à montrer des teneurs supérieures pour l'ɑ-globuline  et  la  β1-globuline (P < 0,06). A 30   jours,   les   protéines   totales   et   les   β2-globulines ont été supérieures dans le groupe colostrum. L’administration  du  colostrum  hétérologue  chez  le  chevreau  semble donc avoir des effets positifs sur certains paramètres plasmatiques et même les performances pondérales. Le  cinquième  chapitre  traite  de  "Effet  de  l’apport  en  colostrum  de  bovin  Azawak  sur  les  performances,   les paramètres de reproduction et la survie chez les chevreaux roux". Cette étude a permis de comparer les performances de croissance pondérale ainsi que le gain moyen quotidien de deux lots de cabris élevés selon les deux modes c'est-à-dire la supplémentation (n = 20) et son absence non (n = 20). Le poids vif moyen du groupe colostrum a atteint une valeur significativement plus élevée que celle obtenu chez les animaux non supplémenté (P < 0,001) et les effets du traitement sur ADG ont été observés jusqu'à 150 jours après la fin de la supplémentation. Une tendance similaire de longue durée a également été observée en relation avec le taux de mortalité (25% pour ColG vs 55% pour ConG, (P = 0,05). L'âge à la première mise bas tendait à être plus faible dans le groupe traité (13,8 ± 0,7 vs 14,1 ± 0,8 mois, p ˂ 0,1). Dans l'ensemble, l'analyse statistique a révélé des différences très significatives en faveur du groupe de colostrum. Globalement,   l’analyse   statistique   des   données   a   révélé   des   différences hautement significatives en faveur du lot colostrum. Le  sixième  chapitre  porte  sur  l’Effet  de  l’administration  post-partum de colostrum bovin Azawak sur les paramètres zootechniques de cabris roux. Un dispositif quasi-similaire à celui du premier essai (chapitre IV) a été appliqué. La différence se situait au niveau de la dose du colostrum administré. En effet, la quantité de colostrum administrée (15 ml) lors du premier essai a été majorée de 66,7 % au cours de cette expérimentation soit une quantité de 25ml/jour/chevreau. Comme le premier essai a été probant,   l’objectif   de   ce   travail   était   de   voir   si   l’augmentation   de   la   dose   du   colostrum   à   administrer   peut améliorer davantage les paramètres zootechniques et réduire considérablement le taux de mortalité. Les résultats indiquent que la supplémentation avec du colostrum bovin augmente la croissance  des  chevreaux  principalement  jusqu’au  sevrage  (P < 0,001),  améliore  l’état  sanitaire  et   diminue le taux de mortalité (P < 0,05), modifie quelques paramètres zootechniques. Cette étude suggère de prodiguer un allaitement  artificiel  chez  d’autres  espèces  animales  dont  les  mères  peinent  à   couvrir les besoins en colostrum et en lait de leur progéniture. A   notre   connaissance,   dans   l’environnement   étudié,   ce   travail   est   original et semble apporter de nouvelles connaissances qui auront probablement des applications pratiques dans les régions présentant  des  conditions  d’élevage  assez  difficiles. [less ▲]

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See detailEtude de la matière sombre par effet de mirage gravitationnel
Biernaux, Judith ULg

Master's dissertation (2014)

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See detailAnalyse multicouche des flux de CO2 et de leur signature isotopique sur un sol forestier
Goffin, Stéphanie ULg

Doctoral thesis (2014)

Dans cette thèse, nous avons étudié le flux de dioxyde de carbone (CO2) provenant d’un sol forestier (Fs) à des échelles de temps relativement courtes allant de la seconde à quelques jours avec l’objectif ... [more ▼]

Dans cette thèse, nous avons étudié le flux de dioxyde de carbone (CO2) provenant d’un sol forestier (Fs) à des échelles de temps relativement courtes allant de la seconde à quelques jours avec l’objectif général de mieux en comprendre les mécanismes. Le flux de CO2 résulte de deux composantes principales, à savoir la production du CO2 au sein du sol et son transport jusqu’à la surface. Ces deux composantes ont systématiquement été distinguées et analysées afin de mettre en évidence les variables qui les régissent. Cette manière de procéder nous a permis d’investiguer, en plus de leur dynamique, la distribution verticale des sources de CO2. En outre, nous avons étudié la signature isotopique en carbone (C) de ces sources afin d’apporter des éléments nouveaux dans la compréhension du processus de production de CO2, notamment nous avons estimé le temps de transfert d’une molécule fraichement photoassimilée de la canopée vers la rhizosphère. Dans une étude effectuée sur un sol forestier (Haplic Regosol; FAO, 2006) à Hartheim (Allemagne), nous avons montré que les sources de CO2 étaient clairement stratifiées dans le sol et nous avons évalué à 11.5%, 64.7%, 15.8% et 8% la contribution respective des horizons OL, Ah, AhC et C à la production totale de CO2. Cette répartition coïncide avec la distribution des racines et du carbone organique sur ce site. Par contre, nous n’avons pas mis en évidence de différence significative dans la composition isotopique des sources associée aux différents horizons en raison de la large incertitude imputée à ces termes. Pour le processus de production, nous avons mis en évidence des variabilités inter et intra-journalières significatives. Toutes ces variabilités sont correctement expliquées par les variations de température à l’exception de la variabilité intra-journalière des sources dans Ah. Pour expliquer celle-ci, l’hypothèse de l’influence d’une onde de pression à travers le phloème qui présenterait un cycle intra-journalier a été avancée. Cette hypothèse, récemment avancée dans la littérature, suppose un lien étroit entre l’assimilation photosynthétique et l’approvisionnement en substrat de la rhizosphère, laquelle est très importante dans l’horizon Ah. Enfin, nous avons rapporté des variations inter-journalières significatives de la composition isotopique des sources dans l’horizon Ah. Plus précisément, un enrichissement en 13C des termes de production est mis en évidence lors de l’assèchement du sol. En outre, ces variations nous ont permis d’estimer à 3 jours le temps de transfert des photoassimilats dans la rhizosphère de Ah. Pour le processus de transport, nous avons souligné que la diffusion convenait à la description du transport dans toutes les couches de sol à l’exception de la litière. Dans cette dernière, il y a lieu d’inclure un mode de transport induit par la turbulence se produisant à la surface du sol. Parmi les transports résultant de la turbulence, on retrouve l’advection et la dispersion. Nous montrons que l’advection n’est à considérer que sur des échelles de temps extrêmement courtes (< seconde) alors que la dispersion, menant à une augmentation des quantités de C transférées par diffusion, devrait faire l’objet d’une attention particulière sur des échelles de temps moins courtes (heures). [less ▲]

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See detailÉléments optiques biréfringents pour interféromètre à chemins optiques quasi-communs
Blain, Pascal ULg

Doctoral thesis (2014)

Notre étude porte sur l’utilisation de composants optiques biréfringents en tant qu’élément séparateur dans un interféromètre à chemins optiques communs ou quasi-communs. Pour ce type d’interféromètre, la ... [more ▼]

Notre étude porte sur l’utilisation de composants optiques biréfringents en tant qu’élément séparateur dans un interféromètre à chemins optiques communs ou quasi-communs. Pour ce type d’interféromètre, la seule différence introduite dans les chemins optiques des faisceaux objet et de référence est celle résultant du relief de la surface testée. Utiliser un élément biréfringent permet de n’avoir qu’un seul élément pour créer les faisceaux référence et objet. On parle d’auto-référencement. Cette propriété désensibilise l’interféromètre vis-à-vis de certaines perturbations extérieures car les faisceaux sont identiquement affectés par celles-ci. La biréfringence des cristaux étant bien souvent faible mais l’interféromètre à construire devant être le plus compact possible, le cisaillement entre les deux faisceaux s’en retrouve faible comparé à la taille de l’objet observé. Une séparation totale des faisceaux émergents n’est possible qu’avec un faisceau « ponctuel » collimaté. La configuration des interféromètres que nous étudierons sera donc différentielle. Deux types d’éléments biréfringents sont étudiés. Le premier est un assemblage de deux cristaux uniaxes taillés à 45° et dont l’orientation de l’axe de l’un des cristaux est tournée à 90° par rapport à celle de l’autre. Il s’agit de la lame de Savart. Les propriétés de cette lame sont détaillées pour justifier l’intérêt de son utilisation dans l’interféromètre. Ce dernier a été utilisé en shearographie et en profilométrie par projection de franges interférométriques. Une installation originale permet l’association des deux méthodes dans un unique montage compact. Dans la configuration proposée, seule l’orientation du cisaillement par l’interféromètre est possible. Pour faire varier la taille du cisaillement, nous avons décidé d’évoluer vers un autre type d’élément biréfringent. L’essor des éléments optiques à biréfringence spatialement variable nous a incités à investiguer cette voie. Ces éléments ont la particularité de permettre une variation spatiale de l’orientation de l’axe optique. Les réseaux de polarisation font partie de cette famille. Après avoir décrit et simulé leur comportement, nous proposons notre propre méthode d’enregistrement de tels réseaux par holographie de polarisation à l’aide d’une lame de Savart. Nous prouvons par la suite que deux réseaux de polarisation circulaire de même orientation et disposés l’un à la suite de l’autre créent un élément séparateur à taille et orientation de cisaillement variables pour un interféromètre à chemins optiques quasi-communs. Nous proposons une application en shearographie. [less ▲]

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See detailFers et bois dans les combles médiévaux et modernes du sud de la Belgique. Contribution à l'histoire de la construction en Europe occidentale
Maggi, Christophe ULg

Doctoral thesis (2014)

After four years of doctoral research on the topic of iron in the roof framing, a detailed typologic timeline could be established. It covers the period between the thirteenth and eighteenth century. The ... [more ▼]

After four years of doctoral research on the topic of iron in the roof framing, a detailed typologic timeline could be established. It covers the period between the thirteenth and eighteenth century. The development of such an inventory was possible by the development of an interdisciplinary methodology combining dendrochronology, archaeometallurgy and techniques of building archeology. Reflections and comparisons crossed with nearly 750 armatures from the investigation of 68 roof or attic parts, mainly located in Wallonia, helped to inventory 89 differents frames iron models. [less ▲]

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See detailFrom censored to cross-sectional data: non and semiparametric new developments
Laurent, Géraldine ULg

Doctoral thesis (2014)

In many statistical studies, an observation is evident: the available data are regularly right-censored. A censorship arises when, for different reasons, the data time of interest can not be observed. A ... [more ▼]

In many statistical studies, an observation is evident: the available data are regularly right-censored. A censorship arises when, for different reasons, the data time of interest can not be observed. A data is so right-censored if, instead of observing its time of interest, a lower bound of this time is considered for this data. For example, the study duration can be shorter than the time of interest leading then to a correspondence between the observed times and the study end time. Moreover, these data can be obtained from cross-sectional process. Cross-sectional process selects only data in progress at a fixed time to constitute the studied sample, determining the data followed for the study. Therefore, cross-sectional process introduces left truncation. A data is described as left-truncated if its time of interest is larger or equal to a fixed time. It is in this context this thesis has been elaborated. The considered estimation problems for such data will be studied with a nonparametric or semiparametric approach. An approach is nonparametric or semiparametric if none assumption is supposed about the belonging to parametric family for the time of interest distribution function, solely based on qualitative hypotheses. These estimation methods have thus the advantage to be based on weaker assumptions in comparison with the parametric approaches. The aim of the different researches developed in this thesis is to improve the current estimation techniques. This thesis is organised in four parts. The first part (first chapter) determines the context of our researches through practical examples and a significant but not exhaustive literature overview as well as our motivation about the different researches presented in this thesis. To conclude this first part, our contributions in these researches are briefly explained. The second part (second chapter) presents a new estimation procedure for the parameters of the parametric conditional variance in the heteroscedastic regression situation applied to right-censored data. This procedure constructs artificial data to replace censored data exploiting a heteroscedastic regression model and then defines the optimal parameters from the least squares method. The interest of this research is to fill a gap in the current literature. The third part (third and fourth chapters) studies, in a regression context, the cross-sectional data, i.e. left-truncated and right-censored data, where the conditional truncation distribution function is supposed to be known. The innovation of the method proposed here consists in the use of information contained in the conditional truncation distribution function for the nonparametric estimation methods. Finally, the fourth part (fifth chapter) is devoted to the cross-sectional data examination but this time for nonparametric estimation of the time of interest distribution function. In this chapter, the truncation distribution function is supposed to belong to a parametric family and not known anymore. The relevance of this approach is due to this weaker assumption than one in the above part. This information about the truncation distribution function is also introduced in the nonparametric estimation. This thesis concludes with a set of suggestions related to possible future researches in these statistical fields. [less ▲]

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See detailDjango Unchained, Structure d'une polémique
Wintgens, Caroline ULg

Master's dissertation (2014)

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See detailTraitement des infections à entérobactéries productrices de béta-lactamase à spectre élargi: quelles alternatives aux carbapénèmes?
DESCY, Julie ULg

Master of advanced studies dissertation (2014)

Introduction : Les entérobactéries productrices de β-lactamases à spectre élargi (BLSE) sont responsables d’un nombre important d’infections liées aux soins, mais aussi communautaires. Des alternatives ... [more ▼]

Introduction : Les entérobactéries productrices de β-lactamases à spectre élargi (BLSE) sont responsables d’un nombre important d’infections liées aux soins, mais aussi communautaires. Des alternatives thérapeutiques aux carbapénèmes devraient être utilisées, notamment à cause de l’émergence des bactéries productrices de carbapénèmase. Méthodes : Une étude prospective a été menée au CHU de Liège afin de déterminer le profil, clinique et microbiologique, de 30 patients infectés par une bactérie productrice de BLSE. Ces patients ont été divisés en 2 groupes (ceux traités par méropénème versus alternatives thérapeutiques) et différentes variables ont été analysées dont une évaluation de leur évolution clinique 14 et 28 jours après la date du prélèvement index de leur inclusion dans l’étude. Résultats : Sur les 30 patients inclus, 10 patients ont été traités empiriquement par méropénème : sur les 8 patients qui auraient pu bénéficier d’une antibiothérapie alternative, 4 traitements ont été changés une fois l’antibiogramme disponible. L’évolution clinique des 10 patients ayant bénéficié d’un traitement définitif par méropénème n’était pas statistiquement différente des 20 patients ayant reçu une antibiothérapie alternative. Lorsque les traitements empiriques par méropénème et pipéracilline-tazobactam sont pris en compte, l’intervention d’un infectiologue est associée à un taux plus élevé de réduction du spectre de l’antibiothérapie : 50% de réduction chez les patients ayant bénéficié de l’avis d’un infectiologue contre 29% chez les patients n’en ayant pas bénéficié. Conclusion : Une collaboration entre les microbiologistes, les infectiologues et les cliniciens permet aux patients, infectés par une entérobactérie productrice de BLSE, de bénéficier dans de nombreux cas d’une alternative thérapeutique aux carbapénèmes. [less ▲]

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See detailSynthesis and Biological Studies of Lanthionine Derivatives
Denoël, Thibaut ULg

Doctoral thesis (2014)

The widespread use of antibiotics has caused bacteria to become drug resistant. Efforts have been done by many research groups to identify new molecules as inhibitors or inactivators of resistant proteins ... [more ▼]

The widespread use of antibiotics has caused bacteria to become drug resistant. Efforts have been done by many research groups to identify new molecules as inhibitors or inactivators of resistant proteins like Penicillin Binding Proteins (PBPs) or to find new targets which allow putting peptidoglycan (PG) biosynthesis under control. The aim of this work is to develop a new labeling method for PG allowing to identify novel antibiotics and worthy target for inhibition. In Escherichia coli, meso-diaminopimelic acid (A2pm) is a key molecule for reticulation of PG. During this work, we synthesized meso-lanthionine, the monosulfur analogue of meso A2pm, and some of its derivatives. As these compounds are susceptible to enter PG biosynthesis via MurE enzymatic addition onto UDP (S) Ala γ (R) Glu, their use in a new labeling method has been investigated. Another approach was the introduction of labeled lanthionines in PG via the recycling pathway by replacement of the natural tripeptide (S) Ala γ (R)-Glu-meso-A2pm with tripeptide analogues containing modified lanthionines. We have developed a new stereoselective synthesis of the three lanthionine diastereomers (meso-Lan, (R,R)-Lan and (S,S)-Lan) and of an α-benzylated analogue. Good yields at the gram scale and excellent diastereomeric excesses (>99%), without any enrichment step, were obtained in aqueous solution. Biological experiments showed the incorporation of meso-Lan and (R,R)-Lan into PG. Upon this results, [35S]lanthionine diastereomers could be used to study the biosynthesis of PG and its turnover in relation to cell growth and division. Unfortunately, the α-benzylated lanthionine was not incorporated. This result indicates that the introduction of lanthionines with a substituted aromatic group at this position is not feasible via the reaction catalysed by MurE. We have also developed a synthesis of protected lanthionines bearing an α-alkyl group useful for the preparation of PG building block analogues. An enantiomeric excess of 97% was obtained for the alkylation of an oxazoline precursor. An SN2 reaction with a cysteine on the β carbon of cyclic sulfamidate precursors was highly successful, despite the sterically crowded α-carbon. In this way, we have obtained several protected α-alkyl lanthionines. These products are promising building blocks for peptide synthesis. In this report, we also describe a diastereoselective synthesis of α-substituted tripeptides. These compounds, containing a fluorescent tag or a photoactivatable group situated on an α carbon, could potentially be used to study PG biosynthesis. We have obtained chiral α alkyl sulfamidates with enantiomeric excess of 89 97%. Those sulfamidates are excellent electrophiles with cysteine to provide lanthionines. The lanthionines were then readily converted into tripeptides (S)-Ala-γ-(R)-Glu-(R,S/R,R)-α-benzyl-lanthionine and phenylazido analogues in a one pot reaction. Those tripeptides were substrates of Mpl in vitro. We did not observe any incorporation of these tripeptides in the PG of E. coli. [less ▲]

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See detailIntegrated dynamical models of down-the-hole percussive drilling
Depouhon, Alexandre ULg

Doctoral thesis (2014)

Due to the overall process complexity, studies about percussive drilling usually focus on a limited set of the subprocesses underlying it, e.g., the hammer thermodynamics or the interaction between the ... [more ▼]

Due to the overall process complexity, studies about percussive drilling usually focus on a limited set of the subprocesses underlying it, e.g., the hammer thermodynamics or the interaction between the bit and the rock. Following this paradigm, the assessment of the process performance is typically performed by considering a single percussive activation and a single interaction cycle between the bit and the rock, from arbitrary initial conditions. The need for an integrated approach to evaluate drilling performance, based on the dynamical interaction of the subprocesses underlying drilling, is evident. Such an approach requires simplified models, however, as the computational cost associated with full scale models is simply unbearable. In this thesis, three dynamical integrated models are proposed and a preliminary analysis is conducted for a reference configuration and around it. The models couple three modules that represent: (i) the dynamics of the mechanical system, (ii) the interaction between the bit and the rock, and (iii) the activation of the mechanical system. For each module, simple representations are considered; of particular importance is the bit/rock interaction model which is a generalization to repeated interactions of experimental evidence observed for a single interaction. In the first model, the dynamics of a rigid bit is cast into a drifting oscillator and the activation modeled as a periodic impulsive force. The second and third models account for the dynamics of the piston and the activation results from the impact of the piston on the bit. They are respectively based on elastic and rigid representations of the two bodies. In the rigid model, analytical results of wave propagation in thin rods are used to represent the contact interaction between the piston and the bit. In the elastic model, wave propagation is resolved. Their preliminary analysis has revealed the occurrence of complex dynamical responses in the space of parameters. Expected trends are recovered around a reference configuration corresponding to a low-size hammer, with an increase of the rate of penetration with the feed force and the percussive frequency. The latter is seen to have a strong influence on the rate of penetration. Interestingly, our analyses show that when the activation period has the same order of magnitude as the timescale associated with the bit/rock interaction, a lower power consumption is observed, indicating a possible resonance phenomenon in the drilling system. Also, the predictions of the rigid model are shown to be in good agreement with the ones of the elastic model, in the explored range of parameters. Given the piecewise linear nature of the proposed models, dedicated numerical tools have been developed to conduct their analysis. As such, the thesis proposes a high-order time integration scheme for structural dynamics as well as a novel framework to evaluate the accuracy of such schemes, and a root-solving module to perform event-detection for coupling with event-driven integration strategies. Specific to the framework is the account for both structural damping and external forcing in the evaluation of the scheme order of accuracy. Specific to the root-solving module is the forcing of event occurrence in the localization procedure. [less ▲]

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See detailLa croissance de l'emploi salarié marchand en Belgique entre 2006 et 2007
Reginster, Alexandre ULg

Master's dissertation (2014)

The goal of the current study, over the growth of salaried employment in the market economy in Belgium between 2006 and 2007, is twofold: It first aims at identifying categories of firm which are highly ... [more ▼]

The goal of the current study, over the growth of salaried employment in the market economy in Belgium between 2006 and 2007, is twofold: It first aims at identifying categories of firm which are highly job-creating whether because of their great performance or because of their heavy weight in the national or regional employment. Thereafter, the study aims at identifying features of the salaried job market dynamics, and the way those dynamics contribute to the growth rates of geographical and sectorial entities. [less ▲]

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See detailLes étudiants futurs enseignants face à la pratique du redoublement : Quelles sont leurs croyances ? Comment se structurent-elles ? Comment évoluent-elles en formation initiale ?
Boraita, Fanny ULg

Doctoral thesis (2014)

Cette recherche étudie l'évolution des croyances d’étudiants futurs enseignants concernant le redoublement et explore les liens qu’elles entretiennent avec la connaissance des recherches scientifiques ... [more ▼]

Cette recherche étudie l'évolution des croyances d’étudiants futurs enseignants concernant le redoublement et explore les liens qu’elles entretiennent avec la connaissance des recherches scientifiques dans le domaine et avec d'autres conceptions psychopédagogiques. Trois questionnements guident le travail : l'identification des croyances des étudiants concernant le redoublement ; leur structuration et la façon dont elles interagissent avec les autres conceptions ; leur évolution au cours de la formation initiale. Pour y apporter des éléments de réponses, l’utilisation de questionnaires et la réalisation d’entretiens ont été combinées auprès d’étudiants en formation en Suisse, Belgique et France. Les résultats suggèrent qu’à l’entrée en formation initiale, leurs croyances sur le redoublement sont empreintes du contexte éducatif culturel dans lequel ils ont grandi et ont été scolarisés. Il ressort par la suite qu’elles évoluent et changent en cours de formation principalement grâce à l’acquisition de la connaissance des recherches menées sur les effets du redoublement. [less ▲]

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See detailRécupération de métaux stratégiques issus de diodes électroluminescentes (DELs)
Aatach, Mohamed ULg

Master's dissertation (2014)

While Light-Emitting Diodes (LEDs) are becoming increasingly widespread, recycling of LEDs is not yet commonplace. And yet, they contain a number of strategic metals as defined by the European Commission ... [more ▼]

While Light-Emitting Diodes (LEDs) are becoming increasingly widespread, recycling of LEDs is not yet commonplace. And yet, they contain a number of strategic metals as defined by the European Commission. However, their composition and design in the broad sense are not always known. LEDs for General Lighting and LED Backlights will soon form a significant stream of waste which will be to be dealt with more effectively need if we do not want to lose strategic resources. This thesis provides an overview of technologies with relevance to LEDs and examines the recovery of strategic metals from end-of-life LEDs. The main material of the study focuses on a batch of SMD RGB LEDs. An elemental characterization consisting of a qualitative analysis by X-ray fluorescence spectrometry and a quantitative analysis by inductively-coupled plasma spectrometry was carried out. Once the composition of the study material was known, several tests of leaching in sulphuric acid were been made to assess the influences of the mode of release of the material, the addition of an ferric oxidant and the pH. Subsequently, it was determined that the prior crushing of the material, the presence of a ferric oxidant and the maintenance of a low pH offered the best conditions among those investigated for the solubilization of three elements of interest - copper, silver and gallium - while concentrating the gold in the filter cake. Some silver cementation tests by iron, copper or zinc powder were also undertaken. Finally, on basis of the carried out investigations, this work offers two methods for recovering of copper, silver, gallium and gold present in SMD RGB LEDs by an hydrometallurgical processes. [less ▲]

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See detailSur la mise en place d’un module d’initiation à la Pleine Conscience destiné aux étudiants en Médecine Vétérinaire
Busoni, Valeria ULg

Master's dissertation (2014)

Ce mémoire de Certificat Universitaire (formation continue) reprend les données relatives à la mise en place d'un module d'initiation à la pleine conscience à destination des étudiants en médecine ... [more ▼]

Ce mémoire de Certificat Universitaire (formation continue) reprend les données relatives à la mise en place d'un module d'initiation à la pleine conscience à destination des étudiants en médecine vétérinaire. [less ▲]

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See detailLes réécritures en prose de "Barlaam et Josaphat" au XIIIe siècle
Lambert, Adelaïde ULg

Master's dissertation (2014)

Notre mémoire de master portait sur Les réécritures en prose de Barlaam et Josaphat au XIIIe siècle et proposait l’étude de deux versions de ce récit hagiographique qui donne à lire une vie de Bouddha ... [more ▼]

Notre mémoire de master portait sur Les réécritures en prose de Barlaam et Josaphat au XIIIe siècle et proposait l’étude de deux versions de ce récit hagiographique qui donne à lire une vie de Bouddha christianisée : d’une part, la version dite « champenoise » qui résulte d’une translation de la Vulgate latine relatant la légende et, d’autre part, la mise en prose d’une version francienne versifiée étant elle-même une traduction de la Vulgate. L’intérêt de ces deux textes réside tout d’abord dans leur époque de rédaction puisqu’ils sont parmi les premiers de la littérature d’oïl en prose qui, née à l’extrême fin du XIIe siècle, s’épanouit d’abord à travers la réécriture d’œuvres préexistantes. Ainsi, après avoir évalué la fidélité de chacun des remanieurs à la trame narrative, nous avons fourni une réflexion sur les notions de translations interlinguale et intralinguale. L’étude des aspects formels et stylistiques a entre autres révélé que la translation interlinguale, c’est-à-dire du latin vers l’ancien français, parvenait avec une certaine aisance à se détacher de sa source, tandis que la translation intralinguale, soit le dérimage, restait très proche de la version en vers de Barlaam et Josaphat. Mais si la traduction de textes latins est alors très répandue – car elle permet de mettre la littérature religieuse à la portée des illiterati –, la pratique de la mise en prose est rarissime à cette date, notamment parce qu’une source vernaculaire ne possède pas le prestige d’un antécédent latin. Deux hypothèses ont alors été envisagées à propos de la dépendance formelle à une source versifiée : elle serait liée soit à la composante sacrée des œuvres translatées que l’on ne remanierait qu’avec circonspection, soit à la proximité chronologique du texte-source et du texte-cible. Si notre étude a pu modestement aider à une meilleure connaissance du développement de la prose française, elle a également jeté certaines bases pour une enquête sur les techniques de dérimage à l’œuvre dans le corpus que constituent les six mises en prose hagiographiques produites au XIIIe siècle. Longtemps considérées comme des outils heuristiques, les vies de saints n’intéressent la critique littéraire que depuis quelques années. Adoptant à notre tour une approche littéraire relayée par une perspective sociologique, nous nous sommes focalisée sur la fonction occupée par chacun des textes dans la société médiévale du XIIIe siècle à partir de l’analyse de la figure de Josaphat. Le héros de l’œuvre hagiographique, en tant que trait d’union entre Dieu et les hommes, exerce une fonction médiatrice qui peut être annihilée lorsque la perfection ascétique du personnage l’éloigne trop fortement de la réalité du public des vies vernaculaires, qui ne peut plus s’identifier au saint. L’examen des aspects « admirables » et « imitables » de Josaphat, respectivement liés au rôle de vénération ou d’émulation visé par les œuvres, nous a permis d’opposer les deux translations et de formuler quelques hypothèses quant à l’horizon d’attente de leur public et à leur succès divergent. Par notre analyse, nous souhaitions également apporter une contribution à la réflexion sur le public, la fonction et le mode de réception des premières traductions françaises et des mises en prose « précoces ». La méthodologie que nous avons appliquée et qui consistait à mettre en regard deux proses, l’une « vernacularisée », l’autre « déversifiée », a permis la confrontation intéressante d’objets liés à deux projets de recherche différents : d’abord, le projet Transmédie, initié en 2004 par Claudio Galderisi, qui avait pour objectif d’établir un répertoire des traductions vernaculaires françaises de textes latins ; ensuite, le projet international du Nouveau Répertoire dont l’initiative revient à Maria Colombo Timelli. [less ▲]

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See detailNature et architecture : De la morphogenèse du vivant à la création numérique
Stals, Adeline ULg

Master's dissertation (2014)

A l'heure où la révolution numérique s'est opérée, la place occupée par l'informatique dans les bureaux d'architecture a eu un impact important sur la conception et sur la forme en général. La production ... [more ▼]

A l'heure où la révolution numérique s'est opérée, la place occupée par l'informatique dans les bureaux d'architecture a eu un impact important sur la conception et sur la forme en général. La production architecturale est en parallèle influencée par l'avancée des connaissances biologiques voire biomimétiques, pour concevoir à la croisée des mathématiques, de l'informatique et de la biologie. Le numérique, supplantant les instruments traditionnels, engendre une rupture entre forme et structure, renforcée par la multidisciplinarité des processus de création. L'apparition de formes complexes pour répondre aux changements sociétaux, notamment observables dans l’œuvre de Frank Gehry, accentue la transmission d'informations de la conception à la réalisation. Marine Bagneris, au travers de sa thèse sur les morphologies non-standards, propose quant à elle, les pFormes comme outil et la morphologie structurale comme nouveau processus de formation architectural. L'architecte conçoit des protocoles plutôt que des formes. Est-ce une solution d'avenir? [less ▲]

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See detailImage monstrueuse, image transgressive. Contribution à l’étude d’une monstruosité cinématographique
Jousten, Lison ULg

Master's dissertation (2014)

L’enjeu principal du travail de fin d’études consiste à poser la monstruosité en termes de formes davantage qu’en termes de représentations . La monstruosité de l’image cinématographique serait finalement ... [more ▼]

L’enjeu principal du travail de fin d’études consiste à poser la monstruosité en termes de formes davantage qu’en termes de représentations . La monstruosité de l’image cinématographique serait finalement moins liée aux monstres qu’elle peut mettre en scène qu’à une violence toute transgressive et inhérente à sa nature. [less ▲]

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See detailFrontière(s), jeu d'acteurs et espace du contrôle: le cas de Ceuta
Bernes, Laure-Anne ULg

Doctoral thesis (2013)

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See detailMarchés boursiers africains : problématique de l’efficience, dynamique de la volatilité, rendement et volume des transactions
Woroucoubou, Habibou ULg

Doctoral thesis (2013)

With the exception of the Johannesburg Stock Exchange, African stock markets are characterized, in their vast majority, by a marginal number of listed companies, low capitalization, low trading volume and ... [more ▼]

With the exception of the Johannesburg Stock Exchange, African stock markets are characterized, in their vast majority, by a marginal number of listed companies, low capitalization, low trading volume and low liquidity. These characteristics raise questions about the volatility, efficiency, optimal compensation risks to investors and, more generally, to the price adjustment speed to the information conveyed by the volume of transactions. The objective of this doctoral work is to study the behavior of African stock markets through volatility, price, return and volume of transactions in connection with the performance and volatility. Compared to the volatility modeling, the study shows that the EGARCH model is the most suitable process may be applied to the data of African stock markets for estimating and forecasting volatility. For efficiency, the study shows that only the market of South Africa seems to be informationally efficient in the weak form. The analysis of the risk-return relationship reveals that only less developed markets (except Botswana) show a positive and significant premium risk. Such a result means that the least developed African stock markets in the sample reach rewarded accordingly risks for investors. For asymmetry, the study shows that there is presence of leverage for all emerging markets, indicating that in these markets, the bad news has a greater impact on volatility than good news of the same magnitude. In contrast, for less developed markets, there is no leverage. With respect to the relationship between the volume of transactions, performance and volatility, the study shows that emerging African stock markets showed a more or less close to the behavior of other emerging and developed markets of the world in terms of leverage, contemporary positive relationship and causality between trading volume and performance on the one hand, and between trading volume and volatility, on the other hand. In contrast, for other less developed stock markets, the impact of volume on return and volatility is less noticeable. [less ▲]

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See detailInsight into the mechanisms underlying the oncogenic potential of BCL-3 through transcriptomic studies
Zhang, Xin ULg

Doctoral thesis (2013)

The abstract will be available after the corresponding papers are published. For more information, please contact Dr. Alain Chariot.

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See detailMéthodes d'accélération du tir de rayons sonores pour la simulation en acoustique des salles
Lesoinne, Stephane ULg

Doctoral thesis (2013)

This thesis provides methods to speed up the acoustical ray tracing for room acoustics. These methods uses 3 complementary axes that have been implemented, tested and analyzed: CPU vectorization, a ... [more ▼]

This thesis provides methods to speed up the acoustical ray tracing for room acoustics. These methods uses 3 complementary axes that have been implemented, tested and analyzed: CPU vectorization, a geometry preprocessing based on visibility and a decrease in the number of traced rays by using variable size receivers. This results in a overall gain that ranges from 120 to 150 on a 8core CPU. [less ▲]

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See detailStudies on Calcium Phosphate Powder as Protein Carrier for Oral Vaccination and Biocompatible Coatings for Bone Implants
Ozhukil Kollath, Vinayaraj ULg

Doctoral thesis (2013)

Depuis quelques années, la recherche portant sur l’administration ciblée de nouvelles formes galéniques solides a trouvé un nouvel essor et ne cesse de progresser. Dans ces formulations, très souvent, le ... [more ▼]

Depuis quelques années, la recherche portant sur l’administration ciblée de nouvelles formes galéniques solides a trouvé un nouvel essor et ne cesse de progresser. Dans ces formulations, très souvent, le principe actif est associé à un agent de transport : l’excipient. Cette approche est notamment employée dans le cas de l’insuline, de bon nombre d’antibiotiques, de facteurs de croissance développés sur des ciments utilisés en ingénierie tissulaire osseuse, d’acide nucléique ou de médicaments encapsulés dans des nanoparticules utilisés pour le traitement des cancers. Les avantages de tels systèmes sont une meilleure biocompatibilité, une plus grande biodisponibilité et une résorption plus importante. La recherche d’un agent de délivrance optimal a ainsi conduit à développer de nouvelles voies de synthèse reposant essentiellement sur l’optimisation des propriétés architecturales et de surface du matériau. La première partie de ce travail consiste à développer un nouvel agent de transport de protéines destiné à la vaccination orale. Cet agent est construit à partir de phosphate de calcium (hydroxyapatite). L’albumine bovine est employée comme protéine de référence. Elle permet de mesurer la capacité de charge des particules de phosphate de calcium. Le chapitre 2 donne un aperçu général des principes de vaccination orale et du type de matériaux transporteurs utilisés. Les chapitres 3 à 6 présentent les résultats des quatre stratégies utilisées dans cette étude pour préparer le phosphate de calcium. Une caractérisation complète de la surface des poudres sera réalisée de manière à mieux comprendre le mécanisme d’adsorption qui prend naissance entre la protéine et le phosphate de calcium. Le chapitre 3 montre le potentiel d’une méthode de préparation classique de poudres (traitement ultrasonique des suspensions et/ou broyage mécanique des poudres). Elle a pour objet de modifier les caractéristiques de surface des poudres commerciales. Une augmentation de l’intensité du broyage permet de diminuer la taille des particules en dessous du micron. L’augmentation de la surface spécifique des poudres qui en résulte conduit à une augmentation de la quantité de protéine adsorbée par unité de surface. Des tests préliminaires in vitro ont démontré la possibilité d’intégrer des microparticules de phosphate de calcium chargées en protéine dans des cellules dendritiques sans observer d’effet toxique notoire. L’importance que revêt la chimie de surface de l’agent de transport dans le mécanisme d’adsorption des protéines est prouvée au travers de la fonctionnalisation de la surface des particules. Le chapitre 4 présente l’utilisation d’acides aminés (ou de dérivés) comme molécules attractives dans l’optique d’améliorer l’adsorption des protéines à la surface des particules d'hydroxyapatite. Intensifier les interactions électrostatiques entre la protéine et la surface des poudres en les fonctionnalisant avec de la lysine ou de l’arginine conduit à une augmentation de la quantité de protéines adsorbées (jusqu'à 66% en plus par rapport à la poudre d’hydroxyapatite non fonctionnalisée). Le type d’interaction observé entre la molécule attractive et la surface des poudres a été déterminé par RMN. Un processus d’échange rapide se produit à la surface des poudres d’hydroxyapatite. Les mêmes expériences ont été réalisées avec de la dihydroxyphényl alanine et de la dopamine. Cette dernière conduit à une augmentation significative de la quantité de protéine adsorbée en raison de la formation d’un lien covalent.Les poudres ont également été traitées par Plasma Atmosphérique. Les résultats obtenus sont présentés au chapitre 5. L’influence du design du réacteur et de la nature de l’atmosphère gazeuse sur la chimie de surface des poudres d’hydroxyapatite a été étudiée. Bien que l’identification des groupes fonctionnels de surface suite au traitement par Plasma Atmosphérique n'a pas été possible, on constate néanmoins une augmentation jusqu’à 39% de la quantité de protéines adsorbées en surface des particules traitées. Une optimisation du procédé est néanmoins à envisager et des analyses plus poussées complémentaires devront être réalisées afin d'identifier la nature de la surface des poudres traitées. Au chapitre 6, la stratégie envisagée consiste à synthétiser les poudres d’hydroxyapatite par co-précipitation. Les poudres obtenues sont de dimensions nanométriques et présentent les quantités de protéines adsorbées les plus élevées reportées jusqu’à présent dans ce travail. La co-précipitation permet de contrôler la taille des particules, leur degré de pureté et le taux de cristallinité. La deuxième partie de la thèse envisage la formation d'un dépôt électrophorétique de particules d’hydroxyapatite sur des implants métalliques utilisés en réparation osseuse. La présence d’hydroxyapatite en surface de l’implant permet une meilleure et plus rapide ostéointégration et offre également la possibilité de délivrer des substances biologiquement actives telles que des antibiotiques ou des facteurs de croissance. Le chapitre 7 décrit l’influence du solvant, de la durée du dépôt électrophorétique ainsi que la nature et l’intensité du champ électrique appliqué sur la microstructure du dépôt. L’éthanol et le butanol ont été utilisés comme solvant de manière à accroître, d’une part, la stabilité de la suspension et, d’autre part, afin d’éviter la formation de pores dans le film déposé suite à l’éventuelle électrolyse de l’eau. Les films obtenus présentent, pour la plupart, des fractures. Le film le moins "craquelé" a été obtenu par déposition électrophorétique dans du butanol en courant alternatif. Le chapitre 8 évalue enfin le taux de pénétration et l’épaisseur du revêtement d’hydroxyapatite à l’intérieur d’un implant tridimensionnel d’architecture poreuse. On remarque une diminution de l’épaisseur du revêtement d’hydroxyapatite au fur et à mesure que l’on pénètre dans la structure 3D de l’implant. En fonction de la taille des pores de l’implant, le dépôt peut atteindre 400 microns (pour des pores de l’ordre de 0,4mm) jusqu’à 1400 microns (pour des pores atteignant 0,9mm). Des études comparatives ont été réalisées avec de l’hydroxyapatite recouverte d’alginine. [less ▲]

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See detailStructural and biochemical study of the proteins AmiC, NlpD and FtsW involved in the bacterial cell division
Rocaboy, Mathieu ULg

Doctoral thesis (2013)

Cell division in the Gram negative bacterium Escherichia coli is a highly coordinated mechanism involving various physiological functions such as chromosome segregation, cell envelope invagination ... [more ▼]

Cell division in the Gram negative bacterium Escherichia coli is a highly coordinated mechanism involving various physiological functions such as chromosome segregation, cell envelope invagination, peptidoglycan synthesis at the division site and separation of the daughter cells. All these functions require a high level of spatio-temporal regulation in order to preserve the physical integrity of the cell. At least 20 proteins required for a proper cell division are recruited to the division site to form a supramolecular complex called the divisome. This thesis work focused on three major components of the E. coli division machinery: the N-acetylmuramyl L-alanine amidase AmiC, the LytM factor NlpD and the lipid II flippase FtsW. These proteins are recruited at midcell at a late stage of cell division. FtsW is an integral membrane protein crucial for the translocation of the peptidoglycan precursor from the cytoplasm to the periplasm where it will be processed to produce septal peptidoglycan. AmiC acts as a septal peptidoglycan hydrolase that allow the separation of the daughter cells. This enzyme has been shown to be activated by the LytM factor NlpD. The crystal structure of AmiC from E. coli presented in this work confirms the presence of an inhibitory helix in the active site. The AmiC variant lacking this helix exhibits by itself an activity comparable to that of the wild type AmiC activated by NlpD. Furthermore, the direct interaction between AmiC and NlpD has been detected by microscale thermophoresis with an apparent Kd of about 13 µM. The crystal structure of AmiC also reveals the β-sandwich fold of the AMIN domain, responsible for the septal targeting of AmiC to the division site. The two symmetrical four-stranded β-sheets exhibit highly conserved motifs on the two outer faces. Along with the peptidoglycan binding capacity of the AMIN domain, results obtained so far suggest that the AMIN domain could be involved in the recognition of a specific peptidoglycan architecture or a composition different than the lateral peptidoglycan. Production screenings of FtsW from different strains were realized and FstW from E. coli was purified. This challenging project will require additional efforts to obtain sufficient amount of protein for structural investigation. Information gathered in this work confirms the high level of regulation of the hydrolytic activity at the septum and gives a structural basis for a more precise molecular characterization of the division site targeting. Disruption or over-activation of these regulation mechanisms could represent a new strategy in the development of antibacterial compounds. [less ▲]

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See detailDéfinition de propriétés acido-basiques dans les liquides ioniques de seconde génération
Robert, Thierry ULg

Doctoral thesis (2013)

The ionic liquids are salts having the particularity of being molten at temperatures lower than 100 °C. Consequently, these new solvents mainly made up of ions have original physicochemical properties ... [more ▼]

The ionic liquids are salts having the particularity of being molten at temperatures lower than 100 °C. Consequently, these new solvents mainly made up of ions have original physicochemical properties. Within a few years, the ionic liquids passed from a laboratory curiosity to a true field of research impossible to circumvent, currently in full rise. Indeed, the replacement of usual organic solvents in catalytic and/or separation processes by these neoteric solvents offers many advantages but also new opportunities for the “Green Chemistry”. However, the systematic exploitation of the ionic liquids as reactional media rests in particular on the understanding of their chemical properties, which for some of them are still scarcely known, such as the acidity for example. This thesis thus aims to undertake a study of the acido-basic properties of (and in) these solvents, and more particularly to determine the accessible levels of acidity for acid solutions (with added HOTf or HNTf2) in second generation ionic liquids such as [HNEt3][NTf2], [BMIm][NTf2], [BHIm][NTf2], [BMIm][BF4], [BMIm][OTf], [BMIm][PF6] and [BMIm][SbF6]. In order to evaluate these acidity levels, we propose two different methods, each one resting on an extra-thermodynamic assumption. The first, the Hammett acidity function H0, is based on the protonation equilibrium of indicators whose pKa's are proposed as solvent independent. The second, the Strehlow potentiometric function R0(H+), consists in measuring, in a given solvent, the electrochemical potential of the proton compared to the ferricinium/ferrocene redox couple whose potential is supposed to be independent of the solvent, and then to refer it versus the Normal Hydrogen Electrode (NHE) in water. The two methods lead to the same conclusions. Firstly, the ionic liquids are generally contaminated by residual basic impurities (from solvents needed for the synthesis…) which need to be neutralized before reaching the acidity characteristic of the medium. The levels of acidity then obtained are very high and can reach values as high as R00(H+) = -10 in the case of [BMIm][BF4]. Then, the accessible level of acidity in an ionic liquid depends mainly on the nature of its anion, and not of that of its cation. We thus obtain the following classification, by decreasing acidity: [PF6-] > [BF4-] > [NTf2-] > [OTf-], indicating that the triflate is the more solvating anion It was found however that the Hammett acidity function led, for the same concentration in acid, to different levels of acidity, depending on the indicator used. The ionic liquids would consequently be media less dissociating than estimated in the literature and the Hammett function would then be related to an apparent acidity (H0)app, underestimating the real acidity. Finally, a difference in acidity between HNTf2 and HOTf is observed in [BMIm][NTf2] and [BMIm][OTf], HNTf2 showing an acidic character stronger than HOTf. On the other hand, in [BMIm][OTf] these two acids show the same acidity since that of HNTf2 has been leveled by solvent. [less ▲]

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See detailEntomofaune associée à Jatropha curcas (Euphorbiaceae) au Niger et évaluation de l'activité insecticide de son huile
Abdoul Habou, Zakari ULg

Doctoral thesis (2013)

Résumé Jatropha curcas L. est un arbuste de la famille des Euphorbiacées originaire d’Amérique centrale. Cette plante est cultivée pour son huile, valorisée dans la production de biocarburant. Cette huile ... [more ▼]

Résumé Jatropha curcas L. est un arbuste de la famille des Euphorbiacées originaire d’Amérique centrale. Cette plante est cultivée pour son huile, valorisée dans la production de biocarburant. Cette huile possède également une activité insecticide qui constitue un second volet de valorisation de la plante. Malgré la toxicité de la plante, de nombreux insectes causent des dégâts non négligeables au niveau des inflorescences, fruits et/ou des feuilles, réduisant considérablement le rendement en graine et la qualité de l’huile. La première partie de ce travail a consisté en la réalisation d’inventaires de ces insectes au Niger durant la période de juin à octobre, en 2010 et en 2011. Les principaux insectes ravageurs de J. curcas au Niger incluent les familles des Acrididae (Oedaleus senegalensis, O. nigeriensis, Heteracris leani, Parga cyanoptera, Catantops stramineus et Acanthacris ruficornis citrina), Cetoniidae (Pachnoda interrupta, P. marginata, P. sinuata et Rhabdotis sobrina), Coreidae (Leptoglossus membranaceus et Cletus trigonus), Pentatomidae (Agonoscelis versicoloratus, Nezara viridula et Antestia sp.) et Scutelleridae (Calidea panaethiopica). La seconde partie de ce travail a porté sur les possibilités d’utilisation de l’huile de J. curcas dans la lutte contre les ravageurs du niébé et le puceron noir de la fève. Des essais d’efficacité de terrain et de laboratoire ont été menés avec différentes formulations d’huile de Jatropha. Nous avons pu mettre en évidence un effet biocide croissant avec la concentration en huile. Les concentrations de 5% et 7,5% d’huile de J. curcas permettent de réduire le niveau d’attaque des pucerons (Aphis craccivora) de 10 et 50% respectivement par rapport au témoin. Une diminution du nombre des thrips (Megalurothrips sjöstedti) et de punaises (Anoplocnemis curvipes) respectivement de 50 et 75% est observée dans les mêmes conditions. Ces traitements ont conduit à une augmentation significative du rendement [less ▲]

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See detailFilms minces mésoporeux d'oxydes de métaux de transition et de lithium : Influence du cation alcalin et de l'agent structurant sur la synthèse par soft templating
Caes, Sébastien ULg

Doctoral thesis (2013)

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

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

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See detailRôle des récepteurs Fgfs dans la formation des cartilages crâniens du zebrafish
Larbuisson, Arnaud ULg

Doctoral thesis (2013)

Les récepteurs des « fibroblast growth factor » (Fgfrs) sont des récepteurs membranaires à domaine tyrosine kinase. On en dénombre 5 jusqu’à présent. C’est l’interaction ligand-récepteur qui permet le ... [more ▼]

Les récepteurs des « fibroblast growth factor » (Fgfrs) sont des récepteurs membranaires à domaine tyrosine kinase. On en dénombre 5 jusqu’à présent. C’est l’interaction ligand-récepteur qui permet le passage de l’information et, entre autres, l’activation de facteurs de transcription impliqués dans le développement cellulaire et/ou dans la morphogenèse. Notre étude concerne la fonction des Fgfrs dans le développement des cartilages crâniens chez le zebrafish. Le profil d’expression de 4 récepteurs a été étudié à différents stades du développement par hybridation in situ. Ces résultats suggèrent que, au niveau de la région pharyngienne, les Fgfr1a et Fgfr2 sont exprimés dans l’endoderme de 24 hpf à 3 dpf. Le Fgfr3 est également exprimé dans l’endoderme pharyngien aux mêmes stades mais dans le cartilage à 3 dpf. La fonction des récepteurs 1a, 2 et 3 a été étudiée par l’injection de morpholinos dirigés contre leur ARNm. Le marquage des cartilages par l’Alcian Blue montre qu’à 4 dpf, l’absence de chacun des récepteurs engendre des modifications dans la structure et la morphologie des cartilages pharyngiens. L’utilisation d’un transgénique dominant négatif pour les récepteurs nous a permis de déterminer que la signalisation Fgf est cruciale aux alentours de 30 hpf pour la chondrogenèse pharyngienne. Nous avons mis en évidence que les Fgfr1a et Fgfr2 participent à la chondrogenèse pharyngienne via le contrôle d’une cascade génétique endodermique Runx3-Egr1-Sox9b-Fsta sans affecter la différenciation et migration des CCNc/chondrocytes. De plus, notre étude préliminaire portant sur le Fgfr3 nous permet d’émettre l’hypothèse que ce récepteur est impliqué dans le processus de chondrogenèse et que celui-ci joue son rôle avant la migration des CCNc à 24 hpf. [less ▲]

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See detailContribution de la télémétrie à l'investigation urodynamique de la fonction vésico-urétrale chez la chienne.
Noël, Stéphanie ULg

Doctoral thesis (2013)

Micturition disorders are common in veterinary medicine and can occur already in puppies. The congenital urethral sphincter mechanism incompetence represents the second cause of urinary incontinence in ... [more ▼]

Micturition disorders are common in veterinary medicine and can occur already in puppies. The congenital urethral sphincter mechanism incompetence represents the second cause of urinary incontinence in puppies but data on the development and the evolution of the continence mechanism are lacking in veterinary medicine. This study could be the first step in the understanding of the pathophysiology of congenital urethral sphincter mechanism incompetence which resolves spontaneously in half of the affected dogs after the first of the second oestral cycle. The lower urinary tract has been widely investigated in adult female dogs, particularly by urodynamics. Urodynamics is a useful technique providing informations on the vesico-urethral function but some limitations are described. The major limitation is the need for sedation or anaesthesia as it is not feasable to obtain interpretable data from an awake animal. A second limitation is associated with the technique of retrograde cystometry because the technique of bladder filling and the filling rate are not physiological. Therefore, techniques have been developed such as diuresis cystometry or ambulatory urodynamics to decrease the impact of these limitations. In urological research, telemetry allows the investigation of different urodynamic parameters without the need for physical or chemical restraint and during several micturition cycles. The objectives of this work were to study the development and the evolution of the continence mechanism during the prepubertal period and during the two first oestral cycles and to study the vesico-urethral function with telemetry. This technique will be standardized and afterwards will be used to study different current urological drugs commonly used in veterinary medicine. In the first study, we showed that the values of the urodynamic and morphometric parameters of the lower urogenital tract varied in function of the growth of the bitches and also in function of the different phases of the œstrus cycle. The end of the prepubertal period was characterized by an increase of the urethral pressures (maximal urethral pressure, MUP ; maximal urethral closure pressure, MUCP ; integrated pressure, IP) and functional urethral length (FPL) but also by an increase of the urethral (UL) and vaginal lengths (VL) measured by vagino-urethrography compared with values at earlier times. The bladder function was characterized by a non-linear increase of the bladder capacity, which was reached at 6 months of age and by an increase of the bladder threshold pressure observed from 7 months of age. During the oestrus cycle, the urethral pressures significantly decreased during the oestrus and the early dioestrus which are characterized by a decrease in oestrogen plasmatic concentration and by an increase in progesterone plasmatic concentration. The highest values of FPL were observed during the follicular phase (œstrus, prooestrus). Values of UL could not be determined during œstrus of the first cycle because urethras were not identifiable on vaginourethrograms obtained at that time. During the second œstrus cycle, UL was significantly higher during œstrus and early dioestrus compared to anoestrus. No significant variation in Pth was observed during the first cycle ; however during the second cycle, the lowest Pth values were observed during late anoestrus. Pth values were also lower during œstrus compared to proestrus. The luteal phase was associated with an increase in bladder capacity that reached the highest value during the dioestrus. The VL decreased progressively during the second cycle to reach the lowest value during anoestrus. The MUCP and UL were significantly higher during the anoestrus of both cycles compared to the values obtained when the dogs were 9 months old. The same observation was made for IP at the first anoestrus. The increase in values of these parameters during periods with low hormonal influence could suggest an impact of the growth but also a constant improvement of bladder function all along the study. It was interesting to observe that the position of the bladder was variable during the prepubertal period as she was either in an intrapelvic or in an intra-abdominal position. After the prepubertal period, the bladder was always in an intra-abdominal position. In the second study, we showed that a single administration of ephedrine or phenylpropanolamine (PPA) was able to significantly modify the urodynamic and the morphometric parameters. Using conventional urodynamics, both ephedrine or PPA increased the urethral pressures during 4 hours and the FPL during 2 hours. The integrated pressure was elevated during 6 hours with PPA and its value was higher than the value obtained with ephedrine. On the other hand, the FPL remained elevated during 18 hours with ephedrine. Using telemetry, ephedrine, and to a lesser extent PPA, modified bladder function. The administration of ephedrine was associated with an increase in bladder threshold volume and a decrease of the detrusor threshold pressure. An increase in bladder volume was observed after PPA administration. Both drugs modified significantly the hemodynamic parameters. Arterial pressures were significantly increased during 4 to 6 hours after the administration of both drugs and were associated with a decrease in heart rate during 12 hours. These results were in agreement with previous studies and confirmed the fact that sympathetic drugs must be used with caution in incontinent dogs suspected of cardio-vascular diseases. In the third study, we showed that interpretable values of urodynamic parameters were obtained with telemetry. Physiological data were obtained from telemetric recordings because no sedative or analgesic drugs were used during the recording and bladder filling was natural. The location of the implant inside a subcutaneous cavity in the left flank did not disturb the dogs and the quality of the signals were good when the receiver was placed on the lateral wall of the metabolic cage. Telemetry allows continuous recording of values of urodynamic parameters (abdominal pressure, bladder pressure, detrusor pressure and bladder threshold volume) and values of smooth muscle electrical activity parameters. In the first step of the study, conventional urodynamics was compared to telemetry. The values of bladder threshold volume obtained by telemetry was significantly lower than the values obtained by conventional urodynamics. No difference in values of threshold bladder pressure was observed between the two techniques. In the second step of the study, the repeatability of telemetric recordings was assessed between day and night. A good repeatability was obtained with the night recordings. Comparing day and night recordings, higher bladder threshold volumes and lower detrusor threshold pressures were obtained during the night. No variation of the urodynamic parameters was observed during the bladder filling phase. The smooth muscle urethral electrical activity did not vary during the bladder filling phase. The frequency of micturition was not different between day and night but the frequency of involuntary detrusor contractions was higher during the day. In the third step of the study, the effect of drugs currently used to treat different micturition disorders were studied. Oestriol and duloxetine increased the electrical activity at day 8 compared to days 0, 1 and 15. No significant effect of PPA, oestriol, oxybutynin, bethanechol and duloxetine was observed on the values of urodynamic parameters or on the frequency of involuntary detrusor contractions. The results obtained in this study suggest that circadian variations may influence urodynamic measurements and that long-term telemetric studies of the lower urinary tract should be conducted during the night to obtain repeatable recordings. Further pharmacokinetic and pharmacodynamics studies are needed to confirm the effects of the different drugs on vesico-urethral function. [less ▲]

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See detailLa limite Paléocène-Eocène dans le Bassin de Douala Biostratigraphie et essai de reconstitution des paléoenvironnements
Mbesse, Cecile Olive ULg

Doctoral thesis (2013)

ABSTRACT This work consists of the analysis of the palynoflora (dinoflagellates and sporomorphs) identified from four petroleum exploration wells drilled through the Nkapa Formation (Douala Basin ... [more ▼]

ABSTRACT This work consists of the analysis of the palynoflora (dinoflagellates and sporomorphs) identified from four petroleum exploration wells drilled through the Nkapa Formation (Douala Basin, Cameroon). The vertical distribution of index taxa in the Moulongo, Ngata, Mamiwater and North Matanda wells allowed establishing a biostratigraphic frame of the first half of the Paleogene of the Douala Basin and identifying the Paleocene/Eocene boundary in each well through a comparison with surrounding sedimentary basins. Seventy dinoflagellate species have been identified, among which 30 are stratigraphically informative. Four biozones have been established, three for the Paleocene and one for the Early Eocene. The biozone 1 is characterized by Cretaceous species such as Cerodinium diebelii, Lejeunecysta hyalina, Andalusiella gabonensis, Palaeocystodinium australinum and Palaeocystodinium golzowense. The biozone 2 is defined by the acme of Areoligera coronata, Adnatosphaeridium multispinosum and Glaphyrocysta ordinata. The biozone 3 is defined by the acme of several Apectodinium species (A. hyperacanthum, A. homomorphum, A. paniculatum, A. parvum, A. quinquelatum). The biozone 4 is defined by the occurrence of Eocene taxa such as Deflandrea cf. oebisfeldensis, Hystrichosphaeridium tubiferum and Wetzeliella sp. Based on the position of the Paleocene/Eocene boundary in the Moulongo well, correlations have been established with the others sedimentary sequences analysed. Our study shows that, as previously demonstrated for Nigeria in an other study, the acme of Apectodinium in the Douala Basin can be attributed a Late Paleocene age and hence occurred before the carbon isotope excursion (CIE) of the Paleocene-Eocene boundary and the coeval Paleocene-Eocene thermal maximum (PETM). The acme of Apectodinium in the Douala Basin is thus markedly diachronous with the Apectodinium acme identified in various Nordic Basins, where it is contemporaneous with the PETM (earliest Eocene). Ninety-four sporomorph species have been recognized, among which fifty are stratigraphically informative. Three biozones have been established. The biozone 1 is predominantly characterized by Palmae- and Proteaceae-type pollens, the latter with Cretaceous characteristics. The biozone 2, Late Paleocene in age, is characterized by a transition from original floras towards more « modern » floras. The biozone 3 is earliest Eocene in age and shows the early steps of the extant « Leguminosae flora » of West Africa. Together with the biostratigraphic analysis, a palaeoenvironmental reconstruction is proposed, based on dinoflagellate ecology, on the evolution of the dinoflagellate /sporomorph ratio, as well as on the reconstruction of the plant environments in the studied sedimentary sequences. The evolution of the Douala Basin during the timespan studied occurred according to two geographical axes: a WE (Moulongo-Ngata) axis and a SSW-NNE (Moulongo-Mamiwater-North Matanda) axis. During the Early and Middle Paleocene, the Douala Basin was open towards the sea and showed a coastal-estuarine environment, with marginal mangroves and lowland swamp forests. During the Late Paleocene, the marine character of the sedimentation was less prominent as brackish fluvio-lagoonal intertidal environments developped. They were accompanied by gallery forests and surrounded by dense, periodically flooded, forests northwards and by forests on wet soils eastwards. During the earliest Eocene, a marine regression occurred. The palaeoenvironments included confined coastal lagoon systems with a peripheral impoverished local flora northwards, and moist, dense, evergreen forests eastwards. [less ▲]

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See detailLa limite Paléocène-Eocène dans le Bassin de Douala Biostratigraphie et essai de reconstitution des paléoenvironnements
Mbesse, Cécile ULg

Doctoral thesis (2013)

RESUME Ce travail présente une analyse du phytoplancton et des sporomorphes recensés dans divers puits de prospection pétrolière ayant traversé la Formation de Nkapa dans le Bassin de Douala au Cameroun ... [more ▼]

RESUME Ce travail présente une analyse du phytoplancton et des sporomorphes recensés dans divers puits de prospection pétrolière ayant traversé la Formation de Nkapa dans le Bassin de Douala au Cameroun. La distribution verticale de taxons marqueurs dans les sondages de Moulongo, Ngata, Mamiwater et Nord Matanda a permis d’établir une biostratigraphie du Tertiaire inférieur du Bassin et d’y préciser la position de la limite Paléocène-Eocène sur base d’une comparaison avec les bassins sédimentaires avoisinants. En considérant trente espèces de dinoflagellés à caractère stratigraphique sur les quelque septante inventoriées, quatre biozones ont pu être établies, trois pour le Paléocène, une pour l’Eocène basal. La biozone 1 se caractérise par des espèces héritées du Crétacé, Cerodinium diebelii, Lejeunecysta hyalina, Andalusiella gabonensis, Palaeocystodinium australinum et Palaeocystodinium golzowense; les biozones 2 et 3 par les acmés de certaines espèces, pour la 2, de Areoligera coronata, Adnatosphaeridium multispinosum et Glaphyrocysta ordinata, pour la 3, de diverses espèces du genre Apectodinium (A. hyperacanthum, A. homomorphum, A. paniculatum, A. parvum, A. quinquelatum). La biozone 4 voit apparaître des espèces caractéristiques de l’Eocène: Deflandrea cf. oebisfeldensis, Hystrichosphaeridium tubiferum et Wetzeliella sp. En tenant compte de la limite Paléocène/Eocène établie par les stratigraphes pétroliers à Moulongo, les corrélations ont été précisées avec les autres séquences analysées. L’étude a mis en évidence l’existence d’un diachronisme entre deux acmés d’Apectodinium, celui pré-CIE (Carbon Isotope Excursion) observé au Paléocène supérieur dans le Bassin de Douala comme dans celui du Nigeria voisin et celui contemporain du PETM (Paleocene-Eocene Thermal Maximum) dans l’Eocène basal de divers bassins nordiques passés en revue dans le travail. Sur les nonante-quatre espèces de sporomorphes identifiées, une cinquantaine de taxons a été retenue dans un objectif biostratigraphique. Trois biozones à caractère évolutif se sont dégagées: une biozone inférieure à caractère paléocène soulignée par une dominance de formes de types « Palmae » et « Proteaceae », ces dernières d’aspect archaïque crétacé; une biozone intermédiaire du Paléocène supérieur avec évolution de la flore originelle vers un ensemble qui peut être qualifié de plus « moderne » et enfin, à l’Eocène basal, de l’installation d’associations annonçant les prémices de la mise en place de la flore actuelle à « Légumineuses » d’Afrique de l’Ouest. En parallèle de l’analyse biostratigraphique est proposée une reconstitution paléoenvironnementale basée sur l’écologie des dinoflagellés, sur l’évolution du ratio dinoflagellés/pollen et spores et sur la reconstitution des milieux végétaux dans les différentes séquences étudiées. L’évolution du Bassin selon deux axes géographiques a été mise en évidence: un axe WE (Moulongo-Ngata) et un axe SSW-NNE (Moulongo-Mamiwater-Nord Matanda). Au Paléocène inférieur et moyen, le Bassin, largement ouvert sur la mer, présente un milieu côtier-estuarien frangé de mangroves et de forêts de basse plaine marécageuse. Au Paléocène supérieur, l’influence marine se faisant moins importante, des milieux saumâtres fluvio-lagunaires soumis aux marées se développent, ils sont bordés de galeries forestières et entourés de forêts denses périodiquement inondées vers le Nord et de forêts sur sols humides vers l’Est. Avec la régression marine amorcée à la base de l’Eocène, les paléoenvironnements s’individualisent: vers le Nord s’installent des milieux lagunaires confinés entourés d’une flore locale appauvrie et vers l’Est, autour de milieux d’eau douce d’arrière-delta, une forêt dense sempervirente humide de terre ferme occupe le terrain. [less ▲]

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