Modeling of Electromagnetic Systems by Coupling of Subproblems – Application to Thin Shell Finite Element Magnetic Models

Doctoral thesis (2013)

The direct application of the finite element method to realistic electromagnetic problems is challenging, especially when modeling structures with thin conductive and/or magnetic parts. This work presents ... [more ▼]

The direct application of the finite element method to realistic electromagnetic problems is challenging, especially when modeling structures with thin conductive and/or magnetic parts. This work presents a subproblem method for correcting the inaccuracies inherent to classical thin shell models, and to efficiently handle geometrical and material variations in parametric studies. [less ▲]

Sustainable housing in Vietnam: Climate responsive design strategies to optimize thermal comfort

Doctoral thesis (2013)

Housing issue in Vietnam is still a big concern as in 2008, 72.2% of the existing housing was semi-permanent or temporary and 89.2% of the poor did not have a permanent shelter. As a response to ... [more ▼]

Housing issue in Vietnam is still a big concern as in 2008, 72.2% of the existing housing was semi-permanent or temporary and 89.2% of the poor did not have a permanent shelter. As a response to sustainability, the global aim of this thesis is to develop design strategies toward comfortable, energy-efficient housing with acceptable building cost. Occupants’ thermal comfort is the key assessment criterion throughout the research. <br />First of all, the thesis develops a thermal comfort model for Vietnamese people living in naturally ventilated buildings through the data from field surveys around South-East Asia. This comfort model is then validated by survey data in Vietnam in 2012. <br />A new simple climate analysis tool is developed, used to analyze the climate of 3 regions in question and to draw preliminary design guidelines. A comprehensive study on climate responsive design strategies of vernacular housing in Vietnam is also carried out. The results to some extend reveal the remaining values of vernacular architecture and provide valuable lessons for modern applications. <br />Three most common housing prototypes in Vietnam are selected. Afterward a comprehensive framework is implemented to derive thermal performances of 3 typical housing types. Various techniques (in situ monitoring, building thermal simulation, CFD and airflow network model, numerical model calibration, parametric simulation method) are employed to improve the thermal performances and natural ventilation of these houses. <br />The sensitivity of building performance to the design variables is outlined by Monte Carlo-based sensitivity analysis. The thermal performances of the reference cases are optimized using the simulation-based optimization method and the most influential design variables. Optimization results show the best combinations of design strategies for each climatic region. The performances of the optimal solutions are compared with the references, providing an insight of the efficiency of this approach in building design. <br />Finally, the different objectives yielded in this thesis are summarized. The possible future extensions of this research are outlined. [less ▲]

Etude prospective des caractéristiques hématologiques, biochimiques et urinaires du Dogue de Bordeaux: Une race prédisposée à une glomérulopathie familiale

Doctoral thesis (2013)

Dogue de Bordeaux (DDB) dogs are predisposed to a juvenile glomerulonephropathy (JGN), usually leading to an end-stage chronic kidney disease (CKD), mostly before 2 years of age. Since its first ... [more ▼]

Dogue de Bordeaux (DDB) dogs are predisposed to a juvenile glomerulonephropathy (JGN), usually leading to an end-stage chronic kidney disease (CKD), mostly before 2 years of age. Since its first description a few years ago, the number of DDB dogs diagnosed with JGN has drastically increased in Europe. Furthermore, some DDB dogs might develop clinical signs far later than initially thought. As the mode of inheritance of this condition has not yet been elucidated, an early diagnosis of JGN is of central importance for breeders and owners. To ease screening of affected dogs, we first wanted to improve our knowledge of this ancient French breed by describing characteristics of healthy DDB dogs. Given available information, we indeed suspected that some biological specificity existed in this breed, which could affect diagnostic processes and lead to erroneous clinical decisions. We thus determined, in a first study, breed-specific biochemical and hematological reference intervals (RI). For most of the 29 measured biochemical analytes, using the manufacturer’s generic canine RI would not have had a major clinical impact, however breed-specific RI established for 6 of them were relevantly different. Limits of the RI for total proteins, total cholesterol, aspartate aminotransferase, alanine aminotransferase and lipase were higher, while they were markedly lower for total thyroxin. Among the 25 hematological RI that were determined and compared with generic canine RI established in the same laboratory, only those of some red blood cells and platelet indices were sufficiently different to have a significant impact on clinical decision. Most red blood cells indices had higher, whereas most platelet indices had lower RI. As we also hypothesized that some apparently healthy adult DDB could suffer from JGN, we decided to look, in a second study, for the biological abnormalities that were previously described in association with the disease. We thus recruited a large cohort of adult DDB and found that proteinuria (urine protein-to-creatinine ratio (UPC) > 0.5) was present in 33%, and proteinuric CKD in 2% of the dogs. When assessed by UPC, proteinuria increased with age and was associated with changes in several biological variables. Urine specific gravity, plasma albumin and total calcium decreased, whereas cholesterol, fibrinogen and thyroid-stimulating hormone increased with UPC. Furthermore, changes in total renal volume, evaluated by ultrasound, were also described to be affected by magnitude of proteinuria. Having a UPC>0.5 increased the probability of observing urinary granular casts by an odds-ratio of 4. Amplitude of biological variations observed in this study was however generally moderate. Finally, to investigate if proteinuric DDB could be suffering from a glomerular disease related to the JGN, we attempted in a third study to characterize the nature of their proteinuria. For that purpose, we used urinary proteins electrophoresis and specific tubular (retinol binding protein (uRPB) and N-acetyl-β-D-glucosaminidase (uNAG) enzyme) and glomerular (albumin (uAlb) and immunoglobulins G (uIgG)) urinary markers. One hundred and two DDB, including 2 dogs with proteinuric CKD, were retrospectively recruited for this study, irrespective of UPC values, to facilitate comparison. Final interpretations of urine proteins electrophoresis attributed a “normal” pattern to 39 dogs, a tubular pattern to 9 of them, a glomerular pattern to 38, and a mixed pattern to 16. Most of these results were highly correlated to UPC values. However, tubular and mixed patterns were only attributed to entire male dogs because of the presence of an isolated 25kDa band, which might be due to urinary contamination by seminal proteins. When results for urinary markers were compared to values obtained in non proteinuric (UPC≤0.2) DDB dogs, 37% of the borderline proteinuric dogs (0.2≤UPC<0.5) had all four markers within reference limits. On the other hand, all proteinuric DDB dogs had elevated ratios of uAlb and uIgG when their concentrations were related to urinary creatinine (/c). Only 53% of them had an elevated uRBP/c and 35% an elevated uNAG/c, which corresponded to the dogs with highest UPC values. Results of this last study support the hypothesis that proteinuric DDB dogs have a glomerular disease which is likely related to JGN. Additionally, sensitivity, specificity, positive and negative likelihood ratio of electrophoresis to identify dogs with elevated uAlb/c were 94%, 92%, 11.85 and 0.07, in that order. These indices were respectively 90%, 74%, 3.43 and 0.13, to identify DDB dogs with abnormally elevated uIgG/c. [less ▲]

Le potentiel du saule pour la phytostabilisation des sols pollués par les éléments-traces métalliques

Doctoral thesis (2013)

Since the ‘80s, when the concept of phytoremediation first appeared, a lot of research has been put into studying the efficiency of woody plants in metal extraction. Willows, as fast growing plants and ... [more ▼]

Since the ‘80s, when the concept of phytoremediation first appeared, a lot of research has been put into studying the efficiency of woody plants in metal extraction. Willows, as fast growing plants and because of their tolerance to difficult edaphic conditions, have been particularly well investigated. In this investigation, the essays were done on Salix clones, which come from a Walloon collection provided by ECOLIRI and ECOLIRIMED projects. The first objective was to study the potential of these local clones by considering not only their ability to extract their pollutants, but also by adding their biomass production to this parameter. We have called the study of these criteria the phenotypic approach to the tolerance of Salix clones to metals. The second added value of this investigation lies in the second objective which aims to complete these phenotypic criteria with physiological and proteomic criteria. These last criteria are often used to study the metal tolerance of plant species, but rarely for willows. The combination of these different approaches gives a expand view of metal tolerance in Salix clones studied in this investigation. As the phenotypical parameters help to answer the extraction ability challenge, the physiological and proteomic approaches give answers linked to the “health” of the willow trees when they grow in the presence of metals. Our results indicate that the clones that produced more biomass were the ones that showed the highest metal concentrations. The clones with lower biomass production showed the same tolerance as the highest producers and our results revealed that growth reduction indicates metal tolerance. Finally, after comparing our results of the metal concentrations obtained in the twigs, to results obtained during the last two decades of research papers, we have concluded that we should reconsider the use of Salix potential in phytoextraction. The first chapter of this investigation was about Salix clones exposed to metals, but, in natural conditions, their roots are colonized by fungi. Thus, their rhizosphere constitutes a separate ecosystem, which is interesting to investigate. The rhizospheric fungi, the first interface between roots and soil pollutants, play an important role in metal tolerance in woody plants. For this reason, the second chapter of this thesis aimed to test the in vitro growth of rhizospheric fungi collected on woody plant roots in the presence of cadmium. The outcome of these essays is that fungal strains have been identified and classified as tolerant to this metal. This chapter thus constitutes a first step in a future study aiming to analyze these strains in association with woody plant roots in the presence of metals. [less ▲]

Variabilité de la respiration hétérotrophe du sol dans des écosystèmes agricoles: Analyse à différentes échelles spatiales et temporelles.

Doctoral thesis (2013)

Soil heterotrophic respiration (HR) was studied at different spatial and temporal scales in agricultural ecosystems in Belgium (loamy region). Results from both laboratory and field experiments conducted ... [more ▼]

Soil heterotrophic respiration (HR) was studied at different spatial and temporal scales in agricultural ecosystems in Belgium (loamy region). Results from both laboratory and field experiments conducted at short and long timescales were analysed with the aim to better understand the influence of driving variables such as temperature, substrate input quantity and quality on HR. Both empirical and semi-mechanistic models were used in order to help interpret experimental results. Our observations showed that temperature is an important HR driving variable in agricultural ecosystems in temperate regions. HR sensitivity to temperature, characterized by a Q10 differing from 2 in our experiments, was very likely influenced by substrate availability and quality. The impact of these last two factors was however never observed through our measurements. Good agreement between modelled and observed CO2 fluxes in the incubation experiment, where carbon substrate was limited, suggested that temperature played a role both directly (enzymatic response) and indirectly (labile carbon stock depletion) at a relatively short term, and confirmed the hypothesis of occurrence of abiotic fluxes linked to the presence of carbonates in the samples taken from a limed agricultural field. Crop residue management (in both quantity and quality), as characterized by relatively low input levels in our experiment, influenced soil carbon stocks in the long term. However, HR, microbial biomass, labile carbon and metabolic diversity were not affected by the investigated treatments. Besides, results from both soil carbon budgets and short term HR measurements showed that supposedly large differences were likely to be reduced due to the relatively large proportion of root residues, weeds and residues unexported at harvest. [less ▲]

La structuration du monde paysan au Rwanda : cas des coopératives et des stations de lavage de café de Maraba et de Karaba, District de Huye

Doctoral thesis (2013)

The agricultural sector is the main economic activity of Rwanda, which occupies approximately 90% of the active population in rural areas. It contributes more than 36% to the GDP. Coffee is the main cash ... [more ▼]

The agricultural sector is the main economic activity of Rwanda, which occupies approximately 90% of the active population in rural areas. It contributes more than 36% to the GDP. Coffee is the main cash crop and source of income for farmers, and provides major currencies for the national economy. Although it covers only 6.3% of cultivated areas, coffee is produced by 500,000 households in Rwanda. Since its introduction in the country in 1904, coffee has always been operated by individual producers. After the liberalization of the coffee sector in Rwanda in 1998, the quantity and quality produced are steadily decreasing which affects the price and the income of coffee growers. In the search for a solution to this problem, the Rwandan government has focused on the consolidation of producers cooperatives, and on the building of coffee washing stations (CWS) in all coffee growing areas at national level. The goal is to produce a fully washed coffee, exportable and better valued on the international market, which can provide better income for peasant producers. Washing stations are then seen as tools to produce quality coffee and are mainly run by cooperatives, which are structural elements in the rural world. Survey work on a sample of 80 farms for the three seasons (2008, 2009, 2010) as well as interviews with various key agents involved in the coffee sector have been conducted to understand and analyze the effects of CWS and cooperatives on coffee growers. This original dissertation is devoted to analyze the impact resulting from the structure action of the peasant world through cooperatives and coffee washing stations of Maraba and Karaba in southern Rwanda, on the socio-economic development of farmers who are members of a cooperative and the surrounding world by comparing to non-members of cooperatives. Through these facilities and structures put in place, jobs are created for producers, farmers are motivated due to income increases, the market is guaranteed, the prices are higher for members and loans are given, thereby improving the socio-economic and technical assistance to growers, which reduces the poverty among coffee growers’ households. [less ▲]

INFLUENCE DE L'ENCLAVEMENT SUR LE DEVELOPPEMENT RURAL (Cas du territoire d'OPALA, District de la Tshopo, R. D. Congo)

Doctoral thesis (2013)

Opala municipality is known for isolation and the precarious conditions of survival for the population. Natural factors such as climate, forest environment, soil erosion and socio-cultural factors ... [more ▼]

Opala municipality is known for isolation and the precarious conditions of survival for the population. Natural factors such as climate, forest environment, soil erosion and socio-cultural factors contribute to its isolation. Since Independence, wars and unrests were added to these factors. After a theoretical approach that analyzes the spatial and territorial issues, the general framework of economic policies and institutional contexts are specified in the thesis. A focus is placed on the poor infrastructures that resulted in isolation of a large part of the Congolese territory. In Opala, a code of community life, the Lilwa, relatively coercive or restrictive regulates social relationships. It contributes to the cognitive confinement of the Mbole, majority ethnic in Opala, making them suspicious and less receptive to new technical innovations. However, it is, at the same time, a solid foundation of social cohesion, based on which should be based any strategy for integral development of the municipality. The thesis includes an empirical research based on a sample of 120 farming households spread over four geographic areas selected according to the distance from Kisangani. The analysis of the main variables used in this research highlights an adaptation of farming systems in relation to isolation. Furthermore, it is important to emphasize the multidimensional nature of poverty, affected by low agronomic performance and lack of infrastructure. The thesis concludes with recommendations for a revival of economic activities in Opala. [less ▲]

Contribution à l'étude des amylases du sorgho et leurs utilisations dans la transformation des produits amylacés

Doctoral thesis (2013)

Les amylases sont des enzymes largement utilisées dans le secteur industriel. Elles occupent d'ailleurs une place primordiale dans le marché mondial des enzymes. Les travaux présentés dans ce manuscrit se ... [more ▼]

Les amylases sont des enzymes largement utilisées dans le secteur industriel. Elles occupent d'ailleurs une place primordiale dans le marché mondial des enzymes. Les travaux présentés dans ce manuscrit se sont intéressés à la production d’amylases à partir d’une source végétale peu coûteuse et disponible, le sorgho et aux possibilités de les utiliser dans la transformation des produits amylacés. Dans la première partie de l’étude, après avoir caractérisé et malté sept variétés de sorgho blanc sélectionné à l’ISRA de Bambey (Sénégal), la meilleure variété, la F-2-20 (sans tanins, faible teneur en composés phénoliques et bonnes activités amylasiques) a été retenue pour la suite de l’étude. Dans la deuxième partie des travaux, les paramètres physico-chimiques tels que le pH optimum, la température optimale et la thermostabilité des amylases (α et β) du malt ont été caractérisés. Les deux amylases ont le même pH optimal 5,5 et la température optimale est de 65 °C pour l’α-amylase et 55 °C pour la β amylase. Par ailleurs, le gène de la β-amylase a été aussi étudié. Les résultats de la troisième partie des travaux ont montré la capacité des amylases du malt de sorgho à être utilisées dans des processus d’hydrolyse d’amidon (maïs et blé) et farines (blé et manioc). L’ajout d’ions calcium n’améliore pas significativement les rendements d’hydrolyse. Enfin, suite aux résultats obtenus, l’hydrolyse a été réalisée à plus grande échelle afin de produire des dextrines de différents DE. Les dextrines ont été analysées chimiquement et physicochimiquement pour déterminer leur composition en oligosaccharides et leurs propriétés physiques en vue de leur application dans les secteurs agroalimentaires. [less ▲]

La charge vocale : De sa quantification à l’étude de son impact sur la fonction phonatoire et sur la qualité vocale

Doctoral thesis (2013)

Ce travail étudie la charge vocale principalement chez les enseignants. La prévalence élevée des troubles de la voix chez ces professionnels serait en partie liée aux trois facteurs principaux de charge ... [more ▼]

Ce travail étudie la charge vocale principalement chez les enseignants. La prévalence élevée des troubles de la voix chez ces professionnels serait en partie liée aux trois facteurs principaux de charge vocale que sont la durée de phonation, le niveau de pression sonore, et la fréquence vocale. Ces facteurs sont associés à des contraintes mécaniques appliquées aux plis vocaux lors de la vibration, potentiellement responsables de microtraumatismes du tissu, et participant au développement de lésions bénignes. Notre contribution intervient à deux niveaux d’étude de la charge vocale. Dans un premier temps, nous l’avons quantifiée en situation écologique dans une population d’enseignantes, en comparant deux niveaux de l’enseignement ordinaire belge : le maternel et le primaire. A cette fin, le comportement vocal de 12 enseignantes du maternel et de 20 enseignantes du primaire a été enregistré durant une semaine de travail, à l’aide d’un système de dosimétrie. Les objectifs étaient, d’une part, de déterminer les différences d’utilisation vocale selon le niveau d’enseignement, et d’autre part, de comparer l’utilisation vocale professionnelle et extra-professionnelle des enseignantes. Globalement, nos résultats montrent une charge vocale plus élevée en situation professionnelle qu’en situation extra-professionnelle. Par ailleurs, les enseignantes du maternel présentent une charge vocale plus élevée que celles du primaire, en termes de nombre de cycles vibratoires et de distance parcourue par les plis vocaux. Dans un deuxième temps, nous avons étudié l’impact de la charge vocale sur la fonction phonatoire et sur la qualité vocale en condition de laboratoire. Une première condition expérimentale avait pour but d’améliorer la compréhension des facteurs de durée et d’intensité de la charge vocale, en soumettant 50 femmes normophoniques à 2 heures de charge, réalisées à deux reprises en variant le niveau d’intensité. Une seconde condition expérimentale avait pour but de comparer les effets de 2 heures de charge chez 16 enseignantes normophoniques et 16 enseignantes dysphoniques. Les effets de la charge vocale ont été évalués à l’aide de mesures objectives et subjectives. Les principaux résultats montrent plus d’impact de la durée que de l’intensité de la charge sur les paramètres observés. Par ailleurs, peu de différences sont observées entre les deux groupes d’enseignantes au cours de la tâche de charge, suggérant que les enseignantes dysphoniques présentent une bonne résistance durant la charge. [less ▲]

The transcription factor Egr1 in zebrafish cartilage development

Doctoral thesis (2013)

The cartilaginous elements forming the pharyngeal arches of the zebrafish derive from cranial neural crest cells. Their proper differentiation and patterning are regulated by reciprocal interactions ... [more ▼]

The cartilaginous elements forming the pharyngeal arches of the zebrafish derive from cranial neural crest cells. Their proper differentiation and patterning are regulated by reciprocal interactions between neural crest cells and surrounding endodermal, ectodermal and mesodermal tissues. In this study, we show that the endodermal factors Runx3 and Sox9b form a regulatory cascade with Egr1 resulting in transcriptional repression of the fsta gene, encoding a BMP antagonist, in pharyngeal endoderm. Using a transgenic line expressing a dominant negative BMP receptor or a specific BMP inhibitor (dorsomorphin), we show that BMP signaling is indeed required around 30 hpf in the neural crest cells to allow cell differentiation and proper pharyngeal cartilage formation. Runx3, Egr1, Sox9b and BMP signaling are required for expression of runx2b, one of the key regulators of cranial cartilage maturation and bone formation. Finally, we show that egr1 depletion leads to increased expression of fsta and inhibition of BMP signaling in the pharyngeal region. In conclusion, we show that the successive induction of the transcription factors Runx3, Egr1 and Sox9b constitutes a regulatory cascade that controls expression of Follistatin A in pharyngeal endoderm, the latter modulating BMP signaling in developing cranial cartilage in zebrafish. [less ▲]

Modified TiO2-based Photocatalytic Films and Powders produced by Aqueous and Non-Aqueous Sol-Gel Processes for Water Purification

Doctoral thesis (2013)

Summary Two major research goals have been proposed for this thesis. The first goal concerns the development of photocatalysts in the shape of thin films coated on glass substrates which includes (i) the ... [more ▼]

Summary Two major research goals have been proposed for this thesis. The first goal concerns the development of photocatalysts in the shape of thin films coated on glass substrates which includes (i) the development of a sol-gel chemistry suitable for the production of stable colloidal suspensions of TiO2 particles, (ii) the optimization of the deposition method and (iii) the development of an experimental device to measure the photocatalytic activity of the films. The second objective is the development of innovative non-aqueous and aqueous sol-gel routes, including the development of new methods for the introduction of dopants as well as the photocatalytic testing of the resulting materials. Two original non-aqueous sol-gel processes involving respectively, an in situ production of water and the controlled addition of a small amount of water, have been developed to produce a series of stable colloidal suspensions of TiO2 particles (sols). From those sols, transparent, adherent, homogeneous thin films have been produced using an optimized dip-coating deposition method and have been proven to be photocatalytically active for the degradation of an organic pollutant in aqueous solution. The photocatalytic activity of the films has been improved through an increase of their roughness thanks to the addition of an organic additive into the sol, leading to an increased active surface involved into the photocatalytic reaction. A mathematical model allowing the rigorous evaluation of the kinetic parameters of the photocatalytic reaction taking into account the influence of the variation of the volume inside the batch photoreactor has been developed. The equations have been established in the case of a photocatalytic powder homogeneously dispersed in the pollutant solution, and in the case of a photocatalytic thin film placed at the bottom of the reactor. The particular case of a first order reaction has been treated and the error on the reaction rate constant induced by neglecting the volume variation has been quantified. An environmentally-friendly aqueous sol-gel process for producing undoped and Cu2+, Ni2+, Zn2+, Pb2+, Fe3+, Cr3+, La3+ or Eu3+ single-doped as well as La3+- Fe3+ and Eu3+- Fe3+ co-doped TiO2 bulk photocatalysts composed of nanocrystallites of anatase and exhibiting a remarkably high photocatalytic activity without requiring any calcination step has been developed. Different effects of the metal ion dopant on the photocatalytic activity have been observed and discussed according to the dopant nature and content. A kinetic study of the photocatalytic degradation of a model pollutant (4-nitrophenol) in aqueous solution under UV-Visible light (330 nm < λ < 800 nm) has been performed over a promising TiO2-Zn2+ doped catalyst. Statistical validations have confirmed the suitability of the phenomenological reaction rate model developed to represent the 4-nitrophenol photocatalytic degradation over time. [less ▲]

Embarquement immédiat pour les nanotechnologies responsables. Comment poser et re-poser la question de la réflexivité?

Doctoral thesis (2013)

Contribution à l'étude des mécanismes transcriptionnels du facteur de transcription SIP1/ZEB2

Doctoral thesis (2013)

Lors de la conversion métastatique des tumeurs épithéliales, certaines cellules tumorales acquièrent la capacité d’envahir le tissu sous-jacent et de former des métastases à distance. De nombreuses ... [more ▼]

Lors de la conversion métastatique des tumeurs épithéliales, certaines cellules tumorales acquièrent la capacité d’envahir le tissu sous-jacent et de former des métastases à distance. De nombreuses données de la littérature montrent que l’acquisition de ces propriétés est accompagnée d’un phénomène de transdifférenciation appelé « transition épithéliomésenchymateuse » (TEM), impliquant la perte de caractéristiques de cellules épithéliales au profit de caractéristiques de cellules mésenchymateuses. Parmi les modifications moléculaires caractéristiques de la TEM, on observe une diminution de l’expression de cadhérine E ainsi et l’expression de novo de filaments de vimentine. L’expression accrue de différents facteurs de transcription inducteurs de la TEM est aussi rapportée. SIP1 est un des facteurs de transcription impliqués dans les phénomènes de TEM tumorale. Il a été clairement montré que SIP1 réprime l’expression de la cadhérine E en liant son promoteur. Le mécanisme de répression n’est pas précisément connu, mais il n’implique pas le co-répresseur CtBP. Un modèle de répression suggère que SIP1 empêche l’accès de facteurs activateurs aux promoteurs des gènes réprimés. Les données obtenues au cours de ce travail nous permettent d’appuyer cette hypothèse et impliquent KLF4, un facteur de transcription activateur liant le promoteur de la cadhérine E, dans ce modèle. Nos résultats révèlent en effet une compétition entre SIP1 et KLF4 pour la liaison sur le promoteur de la cadhérine E. Nous montrons aussi que les deux facteurs ont des effets opposés sur l’activité du promoteur de la cadhérine E et que KLF4 n’active celui-ci que lorsque SIP1 ne peut s’y lier. Enfin, nos données nous ont permis de localiser plus précisément la région du promoteur de la cadhérine E liée par KLF4. Cette région chevauche un des sites liés par SIP1. SIP1 est considéré comme répresseur de la transcription, mais les données s’accumulent montrant l’induction rapide de gènes cibles de la TEM, dont la vimentine, suite à une surexpression de SIP1. Nous avons entrepris de mieux comprendre l’activation de la transcription par SIP1 en utilisant le promoteur de la vimentine comme modèle, et par une approche globale à l’aide de la technique de ChIPSeq. Cette partie n’a malheureusement pas atteint ses objectifs. [less ▲]

Identification et caractérisation des sous-unités ELP5 et ELP6 du complexe Elongator humain

Doctoral thesis (2013)

Familial Dysautonomia is a neurodegenerative disorder that affects the autonomic and sensory nervous systems. This disease results from loss-of-function mutations of the ELP1-encoding gene. ELP1 is ... [more ▼]

Familial Dysautonomia is a neurodegenerative disorder that affects the autonomic and sensory nervous systems. This disease results from loss-of-function mutations of the ELP1-encoding gene. ELP1 is required for the integrity of the so-called Elongator complex, which is composed of two sub-proteins complexes, namely the core-Elongator (ELP1 to ELP3) and HAP (ELP4 to ELP6). While ELP3 is acting as an acetyltransferase that target multiple substrates such as nuclear histones and cytoplasmic α-tubulin, the ELP4-6 has been recently described as an ATPase. This complex has been initially identified as a component of a hyperphosphorylated RNA polymerase II holoenzyme. As a result, Elongator is involved in transcriptional elongation. Since, other roles have been assigned. Elongator is indeed also required for some tRNA modifications in the cytoplasm and consequently controls translation fidelity. Those molecular functions underlie the capacity of Elongator to regulate cell division, DNA-damage response and cell motility. It is likely that a better understanding of the molecular functions of Elongator will clarify its role in these cellular processes and probably highlight new features. The identity of human ELP1 through ELP4 has been reported but human ELP5 and ELP6 have remained uncharacterized. We therefore initiated a study dedicated to the identification and characterization of both proteins. A biochemical purification of ELP4 was conducted to isolate all associated proteins. Such experimental approach led to the identification of DERP6 and C3ORF75 as human ELP5 and ELP6 subunits of the Elongator complex, respectively. We further investigated the cellular functions of both subunits by combining biochemical analysis and cellular assays. Our results show that DERP6/Elp5 is required for the integrity and the fucntion of Elongator and directly connects ELP3 to ELP4. Our laboratory has previously demonstrated the key role of Elongator in cell migration. As cell motility is required for cell invasion and metastasis, we therefore investigated to which extent Elongator is involved in those processes. The migration and tumorigenicity of melanoma-derived cells are significantly decreased upon Elongator invalidation through Elp1 or Elp3 depletion. Strikingly, DERP6/Elp5 and C3ORF75/Elp6-depleted melanoma cells have similar defects, further supporting the idea that DERP6/Elp5 and C3ORF75/Elp6 are essential for Elongator function. Together, our data identify DERP6/ELP5 and C3ORF75/ELP6 as key players for migration, invasion and tumorigenicity of melanoma cells, as integral subunits of Elongator. [less ▲]

Méthode d'intégration de modèles adaptée aux systèmes hydrologiques multicompartimentés

Doctoral thesis (2013)

The water resource management often results from a compartmented view coming from conceptual clippings and administrative apportionments, involving a great specific vertical expertise, confined to a ... [more ▼]

The water resource management often results from a compartmented view coming from conceptual clippings and administrative apportionments, involving a great specific vertical expertise, confined to a unique expertise field. The computer science era immediately participated to the numerical transcription of this order. Numerous compartmented models coexist separately and - if other multi-sectorial are available - the required multidisciplinary expertise that consolidates them is not always ensured in all represented knowledge fields. However, the stakes of the integrated water resource management require a multidisciplinary approach which leads to the emerging of new adapted organizations (water agencies, multidisciplinary centers, international commissions, networks …). Also, since the 70’s, the European Union concern for water policy was leading to a sectorial way of management driven by about thirty water related directives. The 23rd of October 2000, the European Parliament has adopted the Water Framework Directive, establishing a common policy in water domain (European Parliament, 2000). The common approach introduced (watershed level management, objectives by water body, measurement program and agenda, economic analysis of water use…) aimed at harmonizing the water resource management by - among others -integrating available tools (including the former directives). Similarly, at the end of the 90’s, new numerical solutions appeared, allowing to follow this evolution by authorizing the coupling of compartmented models while ensuring the self-preservation of each proper module expertise. More recently, the concept of standard interface dedicated to integrated modeling appeared, sometimes instigating the (wrong) idea, nevertheless desirable, of evolving towards more simplicity. However, the development of such integrated models is still demanding, and requires to strictly follow a modus operandi that guarantees the viability, the consistence and the durability of these new tools. Indeed, the complexity of the modeled systems is reflected in the computer architecture’s tangle allowing couplings, considering numerical and hardware constraints and the pertinence of the represented processes as well as the physical consistency of the integrated model. This kind of tools can also need to satisfy constraints that go beyond the field of expertise of developers as well as the scientific community (usability, autonomous management of scenarios and interoperability of results), to make them operational for an eventual external end-user.   The investigation field covered by the present work aims to structure the integrating expertise acquired for several years at the University of Liege, through numerous concrete developed applications. In that way, we propose an original and operational methodology for internal coupling of compartmented models, primarily applicable to the transversal water resource management (environmental modeling, hydrology in a general way), but also applicable to other related expertise (quality, economy, sociology, …), while considering the boundaries of the field of application of the models and the strong constraints linked to their use. The MOHISE project, dedicated to the integrated hydrological simulation of the water cycle in the scope of studying the effect of potential climatic changes on the state of the water resources, is used as a reference application. In parallel, concrete applications are deployed to illustrate the following topics: • Numerical coupling issues (problems and solutions) ; • Conceptual and processing architectures (interfaces, supervisor, synchronization, …) and the fixation of validity range of the integrated models in the scope of their physical and numerical consistencies ; • Preliminary operations required to implement integrated tools ; • The constrains linked to the methodological choices ; • The management of the simulations themselves (calibration-validation, stability, sensitivity…) ; • Creation of scenarios within the validity range of the model. The subjects are not only addressed on the basis of their strict computer science or compartmented modeling implications but also through an original and sideway lighting to emphasize the essential coupling constraints and the global coherence of the integrated system. [less ▲]

Observation de l’atmosphère de Vénus par le spectromètre imageur VIRTIS-M de Venus-Express : analyse des émissions nocturnes de O2 et OH

Doctoral thesis (2013)

Venus, the second planet of the solar system, has a very dense CO2-dominated atmosphere. Above 50 km, its dynamics is usually decomposed into two main circulation patterns. The first one, the Retrograde ... [more ▼]

Venus, the second planet of the solar system, has a very dense CO2-dominated atmosphere. Above 50 km, its dynamics is usually decomposed into two main circulation patterns. The first one, the Retrograde Superrotating Zonal (RSZ) circulation, controls atmospheric layers below 65 km of altitude. This motion is related to the retrograde rotation of the planet. The second circulation operates above 120 km. This Subsolar-Antisolar (SS-AS) circulation generates a flux from the dayside to the nightside of Venus. It originates from the strong temperature gradients at the top of the atmospheric layer. Between 65 and 120km, the circulation is more complex and no in situ measurement has been performed to study this region of the atmosphere. However, it is possible to use minor atmospheric constituents and their spectral signatures as dynamic tracers to better understand this region. For example, oxygen atoms are produced by photodissociation of CO2 molecules which dominate the Venusian atmosphere. They are then carried by the SS-AS circulation to the planet nightside, where they recombine into O2 molecules in several metastable excited states. Their de-excitation produces measurable emissions, named nightglow which may be qualitatively investigated. This thesis focuses on the study of these emission phenomena. Data have been acquired by the Venus Express spacecraft, in a quasi-polar elliptical orbit around Venus since April 2006. More specifically, observations have been made with the VIRTIS-M instrument, a multispectral imager. As VIRTIS observes in the visible and near infrared domains, some molecular oxygen and hydroxyl transitions can be detected in the data. The main goal of this study has been to extract quantitative information from these observations and to analyze both the density of constituents (such as excited molecular oxygen, atomic oxygen and ozone) and the dynamical processes involved in this region of the Venusian atmosphere. In a first part, data acquired at 1.27 µm in nadir mode have been processed and analyzed in order to study the O2(a1Δg→X3Σg-) infrared atmospheric transition. Data processing consists in correcting the geometrical effects associated with the view angle, the cloud reflection and the thermal contribution. Data analysis following emission patches in individual data sets points out a large variability of the phenomenon, both in terms of brightness and localization. Emission peaks vary from 0.5 to 6 MegaRayleighs (MR) and may be observed over the entire southern hemisphere of the planet, which is the observable part in nadir mode. However, once the individual data are grouped together to generate a statistical map, our analysis shows that the emission at 1.27 µm is located around the antisolar point, which confirms the SS-AS circulation predominance. This map is improved in the northern hemisphere by adding vertical intensity profiles derived from limb images. These profiles are deconvolved to take into account VIRTIS-M spatial resolution and transformed by the Abel inversion to get a local profile of the volume emission rate. A vertical integration of these profiles simulates a nadir observation and completes the bidimensional statistical map of the O2(a1Δg) emission. The intensity reaches 1.6 MR at the antisolar point and the mean nightside value is 0.5 MR. This map, combined with limb profiles, allows to generate a tridimensional distribution of the emission. It shows that the emitting layer is located at ~96.5 km. These results, combined with a tridimensional distribution of the CO2 density (generated with the VTS3 model or measurements from the SPICAV spectrometer on board Venus Express) allows to generate a 3-D map of the atomic oxygen density. The mean nightside density value is 2.0x1011 cm-3 at 103.4 km. This empirical map validates the VTGCM model, as no measurements of the atomic oxygen density had ever been performed in this region of the Venus atmosphere. Other oxygen transitions have been detected in the visible domain (Migliorini et al., 2012): the Herzberg II (c1Σu-→X3Σg-) and Chamberlain (A’3Δu→a1Δg) transitions. Using CO2 and O density profiles derived from our previous study, these transitions have been modeled. Some reaction parameters, whose laboratory measurements are insufficient or inexistent, have thus been estimated. The distribution of the Herzberg I (A3Σu→X3Σg-) transition has also been simulated. Other emission limb profiles have also been extracted from the VIRTIS-M database: the OH(Δv=1) and OH(Δv=2) Meinel emission bands of the hydroxyl molecule. First, these profiles have been processed to subtract a stray signal. The simultaneous statistical study shows that IOH(Δv=1)= 0.60 MR and IOH(Δv=2)=0.23 MR at ~97 km and that their intensity are correlated. The spectral analysis with synthetic spectra demonstrates that only v’≤4 vibrational levels are populated. These emissions have been modeled taking into account excited OH production, deactivation by collisions and reaction and spontaneous emission loss. The CO2 and O density profiles derived from the oxygen study have been used. The quenching coefficients have been adjusted to consider the temperature of the emitting layer and two quenching mechanisms by CO2 have been implemented. This model showed that collisional quenching by single quantum jump (Δv=1) best reproduces the observations. Likewise, an ozone density of 5.8x106 cm-3 at 96.5 km (for the best case) is in good agreement with the recent SPICAV O3 detection. Finally, the study of simultaneous OH(Δv=1) and O2(a1Δg) limb profiles showed a very high spatial correlation of these two emissions. This result has been explained by the role of atomic oxygen as a common precursor for the formation of both molecular oxygen and hydroxyl. [less ▲]

Perception et confort acoustiques des Systèmes de Traitement d'Air

Doctoral thesis (2013)

This thesis addresses the perceived acoustic comfort of Air-Treatment Systems (ATS), such as air-conditioners installed in offices, by taking into account the environmental factors related to the specific ... [more ▼]

This thesis addresses the perceived acoustic comfort of Air-Treatment Systems (ATS), such as air-conditioners installed in offices, by taking into account the environmental factors related to the specific context of ATS usage. The only existing standard to evaluate the sounds emitted by ATS, which is the emitted sound level in dBA, is only loosely related to perception. Therefore, the need of manufacturers for a more reliable standard arises. This implies a thorough study of the perception of the sound of ATS as it is emitted. A precise methodology was then followed: it includes first collecting a high number of ATS sound recordings, up to finally developing a robust metrics to predict the perceived sound quality. For that purpose, different perceptual categories were first identified to constitute the recording database of ATS sounds. A corpus considered as fully representative of the different types of emitted sounds was then extracted from the recording database. Current principles of musical timbre description have already proved to be adequate to other types of environmental sounds; by applying these principles, the relevant auditive attributes for the corpus perceptual description were identified. In order to develop an efficient sound quality predictor through audio features calculation, prominent features based on these auditive attributes were identified that explain the listeners' preferences among ATS sounds. The ecological context of ATS was examined in a second step. Two environmental factors were addressed in the context of ATS sound quality evaluation to ponder their importance in the listeners' perception. As the ATS under study are exclusively indoor systems designed for offices, the effect of reverberation on sound quality evaluation was first studied; for that purpose, an auralization tool was used to simulate room acoustic response. The influence of listeners' attention context on perceived sound quality was then evaluated through a comparative study of various listening conditions. As a matter of fact, the sound emitted by ATS in real conditions is perceived as a perturbation of current activities. It is therefore relevant to evaluate how deeply the degree of attention related to the sound affects listeners as regards their perception of acoustic quality. Eventually, the relevance of the proposed sound quality predictor to comfort perception was assessed in conditions more ecologically representative than usual laboratory environment. [less ▲]

La production d'hydrogène par fermentation anaérobie: Voies d'optimalisation et d'application du bioprocédé

Doctoral thesis (2013)

The emergence of environmental and societal issues caused by the fossil fuels consumption and the simultaneous increase of the energetic needs will lead the society to evolve into a new energetic system ... [more ▼]

The emergence of environmental and societal issues caused by the fossil fuels consumption and the simultaneous increase of the energetic needs will lead the society to evolve into a new energetic system. The creation of the hydrogen society could bring a suitable and sustainable solution since the production and use of hydrogen could be operated at higher yields than the fossil fuels economy and produce energy while generating only water vapour as co product. However, in order to get rid of the fossil fuels consumption, there is a need to diversify the hydrogen production processes and technology, currently still based on CO2—emitting technologies. The so-called “dark fermentation” process is based on strict of facultative anaerobic bacteria producing biohydrogen and soluble metabolites as a fermentation co product. These microorganisms consume organic substrates such as in wastewater to achieve their growth. The biohydrogen technology has been studied during several years in laboratory but still is not mature to be brought at an industrial scale. Indeed, there is first a need to improve the performances (such as the H2 yields and production rates) to achieve the technical and economical requirements. This thesis investigates and discusses various possibilities in order to bring the biohydrogen production process to a larger scale. The strain investigated in this work, Clostridium butyricum, can achieve high performances (in terms of hydrogen yields, about 1.9 to 2.2 molH2·molglucose -1 and production rates, about 50 to 110 mLH2·L-1·h-1 in batch or sequencing-batch cultures) and is able to consume simple and more complex substrates. However, being a strict anaerobic strain, its uses in pure culture requires the achievement of strong anaerobic conditions using artificial and costly means. Moreover, even if the work in pure culture has some advantages at the laboratory scale, it is inappropriate to larger volumes of bioreactor. Therefore, mixed cultures were investigated in batch and sequencing-batch bioreactors, resulting in a decrease by about 30 to 50% of the yields (down to 1.2 to 1.7 molH2·molglucose -1). The mixed cultures reached however comparable or higher performances than the scientific literature confirming the interest of the approach suggested in this work. However, the performances need to be further enhanced in order to make the process economically possible. Therefore, improvements of the yields and the rates were proposed. On the one hand, the yields were increased by 55 to 100% (up to 3.1 molH2·molglucose -1) by improving the mass transfer conditions and, by the way, decreasing the dissolved hydrogen concentration in the liquid media. These considerations led to the design of a novel biodisc bioreactor working continuously and allowing the efficient hydrogen mass transfer. In mixed culture, the biodisc bioreactor reached high performances (H2 yields of 2.4 molH2·molglucose -1 and H2 rates of 600 mLH2·L-1·h-1), showing the interest of the original design and of the “mass transfer” approach achieved in this work. On the other hand, the addition in the culture medium of small quantities of metallic nanoparticles showed a catalytic-like effect by enhancing the hydrogen production rate by about 40 to 100%. Ending this work, the general discussion evidences the advantages of the different techniques suggested in the work and compares them to the recent scientific literature. Furthermore, perspectives are given in terms of scientific outlooks, considering the economical, environmental and technical aspects, in order to bring the hydrogen production process at a large scale. [less ▲]

Contribution à l'étude du rôle des protéases de Microsporum canis dans les premières étapes du processus infectieux et caractérisation d'un nouveau facteur potentiel de virulence

Doctoral thesis (2013)

Evaluation de l'impact environnemental de la production de bioéthanol à partir de canne à sucre, betterave ou froment par analyse du cycle de vie. Comparaison des utilisations biocarburant et bioplastique.

Doctoral thesis (2013)

Creative Spatializations: New Cartographies in Contemporary Black Canadian Fiction

Doctoral thesis (2013)

My dissertation explores the ways in which contemporary black Canadian novels rewrite national space by integrating into it what might be called past and present black spatialities. Regardless of its ... [more ▼]

My dissertation explores the ways in which contemporary black Canadian novels rewrite national space by integrating into it what might be called past and present black spatialities. Regardless of its official policy of multiculturalism, Canada appears unable to reflect the diversity of its population, one of the most multi-ethnic in the world, which results in the social and spatial exclusion of minorities—whose presence is perpetually construed as ‘recent’—from the dominant national narratives. Starting from Henri Lefebvre’s assertion that “[a] social transformation, to be truly revolutionary in character, must manifest a creative capacity in its effects on daily life, on language and on space” (54), and from the conceptualization of fictional literature as both a product and a producer of geographical creativities, this work considers the literary respatializations of black Canada in five recent novels, At the Full and Change of the Moon (1999) and What We All Long For (2005) by Dionne Brand, Any Known Blood (1997) and The Book of Negroes (2007) by Lawrence Hill, and Soucouyant (2007) by David Chariandy. I specifically examine four topographies through which these writers relate ‘blackness’ to ‘Canadianness,’ namely, the ocean, the city, the rural suburb, and the home space. More specifically, this dissertation illuminates how these literary representations of Canadian space locate this nation within the paradigmatic locations of black history but also show how the country’s social and geographical landscape is marked by the black history that took place in the country itself. Through a multidisciplinary approach which looks at theorizations of space emanating from literary, geographical, and sociological fields of study, I examine how these writers shift the terms of Canadian identity by disrupting the founding narratives of the nation which rely on the country’s wild landscapes and construct Canada as a white-only space. Finally, this dissertation engages with racialized bodies whose interconnectedness with both physical and imaginary spaces allow for a multiplicity of creative spatializations to emerge. [less ▲]

Study of the induced systemic resistance of plants: molecular aspects of the interaction between plant cells and amphiphilic elicitors produced by non-pathogenic rhizobacteria

Doctoral thesis (2013)

Some non pathogenic rhizobacteria could locally interact with plants, leading to the stimulation of a primed protection state in the host plant. Upon subsequent pathogen attack, this priming state allows ... [more ▼]

Some non pathogenic rhizobacteria could locally interact with plants, leading to the stimulation of a primed protection state in the host plant. Upon subsequent pathogen attack, this priming state allows an accelerated activation of defense responses extending to all organs of the plant. Fundamental as well as applied research about this induced systemic resistance (ISR) has been tremendously boosted in the past decades, driven by its evident potential for biological control of plant diseases in agriculture. However very little information is available about molecular mechanisms governing the recognition by plant cells of ISR-specific elicitors. Various compounds retaining the ability to elicit ISR have been isolated, among which the recently emerged class of biosurfactants. We conducted the present thesis work with the scope to highlight how such amphiphilic compounds are perceived at the plant cell surface to stimulate the systemic plant immune system. In the first part, the strain B. amyloliquefaciens was selected out of other isolates for its technological traits and previously characterized ISR activity. We demonstrated that surfactin is the most competent cyclic lipopeptide (cLP) family produced by this strain to confer ISR on the selected plant model, tobacco. In order to improve our knowledge about the mechanism governing the perception of this biosurfactant at the plant cell surface, we have combined various approaches such as structure/activity (stimulation of the defense-related oxidative burst) relationship, insertion kinetics within membranes of tobacco cultured cells and thermodynamic determination of binding parameters on various model membranes via isothermal titration calorimetry. Our data indicate that surfactin perception relies on a lipid-driven process which is quite uncommon regarding the typical proteic receptor-mediated recognition of molecular patterns governing the plant basal immunity. We then demonstrate that cLPs induce some enrichment or depletion into specific lipid platforms of different proteins. We hypothesize that it may be: (1) the direct consequence of the generation of insertion sites for some proteins in the entire plasma membrane due to specific cLP segregation at lipid phase interfaces; or (2) result from the indirect adjustment of lipid-modifying enzymes activities through an induced rearrangement of the plasma membrane lipid organization. It reinforces the current hypothesis of a role for lipid microdomains-driven lateral compartmentalization in plant cell signaling. The lipid bilayer of target cells could now be considered as the focal point of cLPs perception from where start cellular responses. As they display an original mechanism of action, the class of amphiphilic ISR elicitors to which they belong become more attractive than ever for further development of innovative biopesticides. [less ▲]

Etude des interactions entre l'entomofaune et un cadavre: approches biologique, comportementale et chémo-écologique du coléoptère nécrophage, Thanatophilus sinuatus Fabricius (Col., Silphidae)

Doctoral thesis (2013)

La décomposition d’un corps entraîne des changements physiques et biochimiques importants, le cadavre va émettre des odeurs attractives pour certaines espèces et d’autres moins attractives. Au sein des ... [more ▼]

La décomposition d’un corps entraîne des changements physiques et biochimiques importants, le cadavre va émettre des odeurs attractives pour certaines espèces et d’autres moins attractives. Au sein des écosystèmes terrestres tempérés, les insectes sont généralement les principaux organismes qui colonisent un corps selon une séquence plus ou moins prédictive. Ces insectes nécrophages et/ou nécrophiles, principalement des Diptères et des Coléoptères, utilisent le micro-habitat créé par le cadavre comme un substrat nourricier, un site de reproduction, un refuge ou encore comme un territoire de chasse. L’objectif principal de cette thèse était de mieux connaitre l’écosystème cadavre et plus précisément les interactions cadavre-entomofaune sous l’angle novateur de l’écologie chimique. Cette approche pluridisciplinaire combine des études biologiques, électrophysiologiques (EAG), comportementales (olfactométrie) ainsi que des analyses de composés volatils par diverses méthodes analytiques ((TDS)-GC-MS, GCxGC-TOF-MS). Le cochon domestique, substitut couramment utilisé pour modéliser la décomposition humaine, a servi de modèle animal pour les études faunistiques de suivis postmortem et les études visant à caractériser la signature olfactive d’un cadavre au cours du processus de décomposition. L’«odeur de la mort» est constituée par un mélange de centaines de composés organiques volatils cadavériques (COVs) dont le profil qualitatif et quantitatif évoluent au cours du processus de décomposition. Les Coléoptères, acteurs importants de l’écosystème-cadavre, étaient jusqu’à présent délaissés par les entomologistes forensiques au profit des Diptères. Ce travail de recherche s’est intéressé à deux familles de Staphylinoidea: les Staphylinidae et les Silphidae. 62 espèces de Staphylinidae ont été recensées au sein de l’écosystème-cadavre. Une espèce de staphylin ressort nettement de ces études in situ: Creophilus maxillosus. Concernant les Silphidae, 9 espèces de Nicrophorinae et de Silphinae ont été recensées sur les carcasses de porc avec une nette prépondérance des Silphinae. Néanmoins, seul le taxon des Silphinae semble avoir un intérêt potentiel en entomologie forensique et plus particulièrement les Thanatophilus spp. et Necrodes littoralis. T. sinuatus a été choisi comme insecte modèle, son cycle de développement ainsi que celui de N. littoralis ont été étudiés en conditions contrôlées à deux températures constantes. Une approche chémo-écologique, combinant des études EAG et olfactométriques, a été réalisée sur T. sinuatus avec une sélection de molécules cadavériques. Ces essais ont mis en avant le rôle attractif du diméthyldisulfure (DMDS) sur T. sinuatus. Ce composé semble être un marqueur clé dans les processus de décomposition animale. Le p-crésol était quant à lui uniquement attractif pour les mâles de T. sinuatus. Ces découvertes améliorent notre compréhension de l’écosystème cadavre et plus particulièrement la communication chimique entre une espèce de Silphinae et un corps en décomposition. Cette recherche a également permis de mieux connaitre les populations de staphylins et de silphes que l’on retrouve au sein de l’écosystème cadavre. [less ▲]

Les cultes isiaques dans la péninsule Ibérique. Contribution à l'étude du phénomène isiaque dans l'Occident méditerranéen

Doctoral thesis (2013)

En 1967, dans son ouvrage plus largement consacré aux religions orientales dans l'Espagne romaine, Antonio García y Bellido offrait une synthèse des cultes isiaques dans la péninsule Ibérique. Après lui ... [more ▼]

En 1967, dans son ouvrage plus largement consacré aux religions orientales dans l'Espagne romaine, Antonio García y Bellido offrait une synthèse des cultes isiaques dans la péninsule Ibérique. Après lui, quelques savants ont tenté d'actualiser son catalogue, d'autres ont posé à la documentation de nouvelles questions. Depuis les années quatre-vingt-dix, Jaime Alvar a écrit une série d'articles sur le sujet, sans jamais les coordonner dans un seul et même volume. Après plusieurs mois de recherches, grâce au matériel déjà connu, il apparaît que l'absence d'une histoire des cultes isiaques dans la péninsule Ibérique peut et mérite d'être comblée. Le développement des études isiaques permet aux chercheurs de poser à la documentation de nouvelles questions, d'autant que les découvertes d'isiaca, aussi ponctuelles soient elles, ont étoffé peu à peu le catalogue des sources. L'apparition de ces documents présume une nouvelle interprétation du phénomène isiaque dans la péninsule Ibérique. A première vue, on sera conduit à enregistrer une évolution, mais il semble qu'elle sera d'abord d'ordre quantitatif. Elle confirmera surtout l'importance de l'étendue des cultes isiaques dans la Péninsule, le principal obstacle restant l'absence de nouvelles données transmises par ces documents. Néanmoins, ces découvertes, considérées dans une perspective plus large, contribueront à améliorer notre vision du phénomène religieux dans un espace géographique dont les spécificités ne manquent pas et actualiseront une recherche en sommeil depuis quarante ans. [less ▲]

Gestion intégrée des ravageurs de céréales et de légumineuses stockées au Sénégal par l’utilisation de substances issues de plantes

Doctoral thesis (2013)

This thesis used an integrated approach to develop options for the control of cereal and legumes insect pests in Senegal combining laboratory and field tests. A diagnostic survey was conducted to fully ... [more ▼]

This thesis used an integrated approach to develop options for the control of cereal and legumes insect pests in Senegal combining laboratory and field tests. A diagnostic survey was conducted to fully understand current storage practices and control methods in foods and seeds. The study focused on traditional practices from the eastern parts of Senegal to develop options in harmony with the populations concerns. Boscia senegalensis is a plant known for its medicinal properties and its food use was the first plant to be tested for the control of Caryedon serratus, the groundnut weevil. We observed that fruits (3% w/w) and crushed leaves (6% w/w) of this species protected groundnuts. B. senegalensis was subsequently used for protection of cowpea, millet and maize against Callosobruchus maculatus, Tribolium castaneum, Sitophilus zeamais and Prostephanus truncatus. Only T. castaneum was insensitive to this plant at low concentrations. Methylisothiocyanate (MITC) is the main active ingredient of this plant liberated from glucocapparin. This molecule can reach C. maculatus and C. serratus larvae and eggs which develop inside grains but concentrations need to be two to four times higher than adults. Ripe fruits still proved to be effective but immature fruits had a higher efficacy. Residues of MITC were detected in the stored grains after treatment, but the treatment had no effect on germination of stored grains. During the study a reliable and effective method to analyze glucocapparin in leaves and fruits of B. senegalensis was developed, during two years in four localities showing an apparently very marked “soil effect”. Highest glucocapparin concentrations were recorded in January at the beginning of dry season and the lowest during the rainy season from August to November, independent of locality. Powdered maize cobs were effective in maintaining maize grain quality in laboratory studies. Observed damage and losses were respectively 5 and 1% at 2.4% (w/w). At higher doses, mixing of powdered maize cobs with grains offered equal protection as Actellic (pyrimiphos-methyl). The efficacy of this control method was tested during two years in farmer’s granaries confirmed the validity of the laboratory tests. The traditional practice of incorporating insecticidal plants within the storage structure did not impact development of pests already established in the granaries. By contrast, storage of maize cobs using a sandwich method with Hyptis spicigera proved to be effective against storage pests. In addition, the storage of non-winnowed maize grains offered a substantial degree of protection against insect infestations. Their composition was carried out by GC-MS/GC-FID analyses. [less ▲]

Learning to Predict End-to-End Network Performance

Doctoral thesis (2013)

The knowledge of end-to-end network performance is essential to many Internet applications and systems including traffic engineering, content distribution networks, overlay routing, application-level ... [more ▼]

The knowledge of end-to-end network performance is essential to many Internet applications and systems including traffic engineering, content distribution networks, overlay routing, application-level multicast, and peer-to-peer applications. On the one hand, such knowledge allows service providers to adjust their services according to the dynamic network conditions. On the other hand, as many systems are flexible in choosing their communication paths and targets, knowing network performance enables to optimize services by e.g. intelligent path selection. In the networking field, end-to-end network performance refers to some property of a network path measured by various metrics such as round-trip time (RTT), available bandwidth (ABW) and packet loss rate (PLR). While much progress has been made in network measurement, a main challenge in the acquisition of network performance on large-scale networks is the quadratical growth of the measurement overheads with respect to the number of network nodes, which renders the active probing of all paths infeasible. Thus, a natural idea is to measure a small set of paths and then predict the others where there are no direct measurements. This understanding has motivated numerous research on approaches to network performance prediction. Commonly, the success of a prediction system is built on its scalability, efficiency, accuracy and practicability. For network performance prediction, two specific requirements have to be met. First, the prediction system should have a decentralized architecture which allows the natural deployment of the system within a networked application. Second, as different performance metrics are useful for different applications, the prediction system should be general and flexible to deal with various metrics in a unified framework. This thesis presents practical approaches to network performance prediction. There are three main contributions. First, the problem of network performance prediction is formulated as a matrix completion problem where the matrix contains performance measures between network nodes with some of them known and the others unknown and thus to be filled. This new formulation is advantageous in that it is flexible to deal with various metrics in a unified framework, despite their diverse nature. The only requirement is that the matrix to be completed has a low-rank characteristic, which has long been observed in performance matrices constructed from various networks and in various metrics. Second, the matrix completion problem is solved by a novel approach called Decentralized Matrix Factorization by Stochastic Gradient Descent (DMFSGD). The approach requires neither explicit constructions of matrices nor special nodes such as landmarks and central servers. Instead, by letting network nodes exchange messages with each other, matrix factorization is collaboratively and iteratively achieved at all nodes, with each node equally retrieving a number of measurements. The approach is practical in that it is simple, with no infrastructure, and is computationally lightweight, containing only vector operations. Third, instead of the conventional representation of exact metric values, this thesis also investigates coarse performance representations including binary classes (The performance is classified into binary classes of either ``good'' or ``bad''.) and ordinal ratings (The performance is quantized from 1 star to 5 stars.). Such more qualitative than quantitative measures not only fulfill the requirements of many Internet applications, but also reduce the measurement cost and enable a unified treatment of various metrics. In addition, as both class and rating measures can be nicely integrated in the matrix completion framework, the same DMFSGD approach is applicable for their prediction, with little modification required. The resulting prediction system has been extensively evaluated on various publicly-available datasets of two kinds of metrics, namely RTT and ABW. These experiments demonstrate not only the scalability and the accuracy of the DMFSGD approach but also its usability in real Internet applications. In addition, the benefits of predicting performance classes and ratings, rather than their actual values, are demonstrated by a case study on peer selection, a function that is commonly required in a number of network applications. [less ▲]

Essays in Portfolio Performance Analysis

Doctoral thesis (2013)

Origin, biodiversity, and extinction of Cretaceous ichthyosaurs

Doctoral thesis (2013)

Ichthyosauria is a group of reptiles that colonized numerous niches in Mesozoic marine ecosystems. Their Cretaceous representatives were however regarded as undiversified, especially compared to their ... [more ▼]

Ichthyosauria is a group of reptiles that colonized numerous niches in Mesozoic marine ecosystems. Their Cretaceous representatives were however regarded as undiversified, especially compared to their Triassic and Jurassic ancestors, because only a few species are regarded as valid in the Cretaceous. Besides, most of them belong to a single genus, Platypterygius, whose taxonomy and phylogeny are problematic. Therefore, Cretaceous ichthyosaurs have been widely considered as the last members of a group on the decline, although the timing, the cause and the magnitude of their extinction phases greatly vary among authors. Yet, a great part of the Cretaceous ichthyosaur record, the Eurasian material, has been neglected from more than 100 years; theories explaining the evolution of the last ichthyosaurs therefore miss the biggest part of the picture. Notably, how ichthyosaurs diversified and went extinct during the Cretaceous is basically unknown. To tackle these topics, I assess the taxonomy of Cretaceous ichthyosaurs from Eurasia, test their phylogenetic position within a global analysis of post-Triassic ichthyosaurs, evaluate their ecological diversity and analyse their phases of radiation and extinction. Assessment of the Eurasian material led to the discovery of seven new taxa (“Iraq animal”, Acamptonectes densus, “Lenin Form”, Sveltonectes insolitus, Sveltonectes “Ebbo Form”, “Sisteron Form”, “Colossal Form”) and the re-installation of several other taxa as valid (Simbirskiasaurus birjukovi, P. bannovkensis, Cetarthrosaurus walkeri, P. hercynicus). Morphological and phylogenetic evidence suggest Platypterygius hides a very large generic diversity and should be limited to its type species P. platydactylus; however, the interrelationships of the large platypterygiine ichthyosaurs from the Aptian–Cenomanian interval are poorly constrained. Phylogenetic analyses provide robust evidence for disparate origins of Cretaceous ichthyosaurs; these animals actually belonged to three distinct clades that diverged several tens of million years before the Cretaceous. These three clades had contrasted evolutionary histories and colonized disctinct ecological niches during the Cretaceous. Survival and extinction rates demonstrate ichthyosaurs suffered no extinction event at the Jurassic–Cretaceous boundary. They were therefore highly diverse during the Cretaceous, although the sampling of some stages remains inadequate. Notably, up to eight genera were present during the late Albian, a few million years before their final extinction. This extinction appears staggered over four phases that span the entire Cenomanian stage; it also forms one of the facets of a much wider event that affected most levels of marine trophic chains during the Cenomanian. Compilation of published data and collaborations with other specialists show that the radiation of snakes, mosasaurs, and numerous lineages of modern fishes, the severe extinctions among cephalopods and rudist bivalves and the complete extinction of ichthyosaurs likely belong to the same global turnover event. The magnitude, diversity and simultaneity of the biotic responses strongly suggest that global physico-chemical factors triggered this profound reorganization of the marine ecosystems, notably the conjunction of a rather brutal onset of extremely high temperatures and sea level, intense marine volcanism and phases of worldwide ocean anoxia. [less ▲]

Epidémiologie de la brucellose et de la tuberculose animales dans les milieux urbain, périurbain et rural au Niger

Doctoral thesis (2013)

Etude chémo-écologique et comportementale du parasitoïde, Nasonia vitripennis Walker (Hym., Pteromalidae), en vue de son utilisation comme biodétecteur en entomologie forensique

Doctoral thesis (2012)

Most reports published in the field of forensic entomology are focused on Diptera, mostly on Calliphoridae. However, Hymenoptera are part of the entomofaunal colonisation of a dead body. Despite their ... [more ▼]

Most reports published in the field of forensic entomology are focused on Diptera, mostly on Calliphoridae. However, Hymenoptera are part of the entomofaunal colonisation of a dead body. Despite their significant presence in crime scenes, parasitoids are largely ignored due to their small size and the paucity of biological and behavioral information available in the ecosystem of corpse. The use of Hymenoptera parasitoids in forensic entomology can be relevant to many applications such as development of a biodectector. The objectives of this thesis were (1) to identify the Hymenoptera community parasitizing necrophagous Diptera, (2) to identify volatile organic compounds emitted by decaying process and by hosts which facilitate host-habitat and host location by female Nasonia vitripennis Walker (3) to evaluate the species N. vitripennis as biodectector of corpses. The faunistic study has identified five species of Hymenoptera in cadaver ecosystem. Alysia manducator was the most abundant Braconidae species. However, N. vitripennis was chosen as insect model; because over the last 50 years, this wasp has been intensely investigated in the subject of genetic, ecological and evolutionary research. A chemo-ecological approach, combining EAG and behavioral studies, was used on N. vitripennis with selected compounds from the decay process and their hosts. Firstly, we have demonstrated that host- habitat location and host location were dependent on the concentration of volatile organic compounds tested. In addition, dimethyldisulfide, a key component of decomposition and also released by Calliphora vicina Robineau-Desvoidy (Diptera, Calliphoridae) pupae, has a biological activity. Secondly, we have showed that rate of parasitism was based on the age of pupa, depth and substrate in which larvae burrow. This rate is the most important when pupae were six day-old, on the surface of soil and in a soil with a granulometry greater than 1mm. Moreover, N. vitripennis expanded our potential resource in biosensor used in forensic science. Females demonstrated a capacity for learning and memory. [less ▲]

Study of the physiological component involved in the development of crown rot in bananas and the role of phenolics in susceptibility variation mechanisms

Doctoral thesis (2012)

Crown rot is a post-harvest disease caused by a broad unspecific and opportunistic parasitic complex, which affects the quality of export bananas in Cameroon, as well as in most of the production areas ... [more ▼]

Crown rot is a post-harvest disease caused by a broad unspecific and opportunistic parasitic complex, which affects the quality of export bananas in Cameroon, as well as in most of the production areas around the world. The originality of this research is that it is sets out, not only to investigate on the conditions surrounding the development of the disease and the variable factors of fruit’s susceptibility, but equally to characterize the phenolic content of the banana crown with differential susceptibility levels. The study therefore aims at showing the influence of abiotic and biotic factors on the fruit’s physiological component at harvest and the involvement of phenolic compounds in the mechanism staked in fruit’s susceptibility variations to this pathology. At the end of this study, it appears that abiotic and biotic factors influence the fruit’s physiological component at harvest, affecting thus its susceptibility level and therefore favours the development of crown rot disease. The reliability of internal necrosis surface (INS) assessments method was improved. The influence of abiotic factors (production area and harvest date) on fruit susceptibility was demonstrated without season influence. Fruits grown in high altitudes (Ekona, 500 m) were less susceptible to crown rot than the ones grown in low altitudes (Dia-Dia, Koumba, 80 m). It was noticed that at certain harvest dates within the rainy season, fruit susceptibility was higher in plantations with low altitudes. Concerning biotic factors, Mycosphaerella leaf spot disease’s influence was shown in two geographical areas. In Cameroon, black leaf streak disease significantly influenced banana’s sensitivity to crown rot (P< 0.001). In Guadeloupe, Sigatoka disease had no effect (P> 0.05) on banana’s susceptibility to the development of crown rot disease. The influence of the source-sink ratio variations, an abiotic factor, on fruit physiology could explain these differences. The influence of severe source-sink ratio modification on fruit susceptibility to crown rot was shown. Fruits with low source-sink ratio were the most susceptible. Bananas of extreme modalities (12leaves/1hand, 1leaf/8hands) and with differential susceptibility (S-, S+) to crown rot were used for the biochemical characterization of their phenolic content at two stages: the day of harvest before inoculation (dhbi) and 13 days post-inoculation (13dpi) by chromatographic methods (GC-MS, HPLC, LC-MS). Dopamine was identified as the major secondary metabolite (phenolic alkaloid) in banana crown. Norepinephrine and normetanephrine levels were high in the dhbi, especially in the S+ crowns. Hydroxycinnamic acids (ferulic acid, coumaric acid and their derivatives) and other unidentified compounds were accumulated in highly significant quantities (P <0.001) in the dhbi in the less susceptible crown (S-) as compared to the susceptible ones (S+), with decreased 13dpi mostly in the susceptible fruits (S+). These results suggest a possible role of these phenolics in banana crown biochemical defense. However, the main role of each phenolic detected in the susceptibility variations mechanism remains unclear. This study is the starting point to understanding the function(s) of phenolics in banana crown defense. This is a pioneer study on the influence of abiotic and biotic factors on the banana fruit’s physiological component at harvest through the assessment of their incidence on crown rot development. This work appears to be the first to link the level of fruit’s susceptibility at two stages (dhbi and13dpi) with their crown phenolic content. [less ▲]

Achromatization of nonimaging Fresnel lenses for photovoltaic solar concentration using refractive and diffractive patterns

Doctoral thesis (2012)

In the field of concentrated photovoltaics, the main disadvantage of lenses compared to mirrors lies in their chromaticity: Snell's law is related to the refractive index which is wavelength dependent ... [more ▼]

In the field of concentrated photovoltaics, the main disadvantage of lenses compared to mirrors lies in their chromaticity: Snell's law is related to the refractive index which is wavelength dependent. Consequently, even for purely collimated beams under normal incidence, the maximum concentration achievable with typical lenses made of PMMA is limited to ~1000×. This maximum value becomes even lower when considering Sun's angular aperture. Since the law of reflection is not wavelength dependent, mirrors can theoretically achieve the thermodynamic limit of concentration which is about 46'000×. This thesis aims at the design and the manufacturing of an achromatic Fresnel lens suitable for photovoltaic solar concentration, i.e. combining high concentration, low production cost and tolerance to manufacturing errors. Firstly, we investigated a hybrid lens made of a refractive lens and a diffractive lens. The investigations showed that the concentration ratio could be multiplied by 4. A full chapter is dedicated to the optimisation of blazed diffraction gratings to finally achieve the design of the diffractive lens. Nevertheless, a bilayer diffractive lens is needed to obtain a high diffraction efficiency which makes the diffractive lens highly sensitive to manufacturing errors and consequently not suitable for photovoltaic solar concentration. Purely refractive achromatic Fresnel doublets were then investigated and several designs were compared. They allow for very high concentration ratios in the case of collimated beams under normal incidence, higher than 100'000×. Therefore, contrary to singlets, Fresnel doublets are much more affected by the angular size of the source than by the chromatic aberration. Moreover, it was shown that they are tolerant to manufacturing error, change of temperature and uncertainty on the refractive index. It emerges from this thesis that the concept of achromatic doublets is a tolerant and low-cost production solution to achieve a highly concentrated white flux. Although bilayer diffractive lenses are not suitable for concentrated photovoltaics, the combination of refractive with diffractive structures seems to be promised to a bright future for spectrum splitting applications, including spectrum splitting for concentrated photovoltaics. [less ▲]

The functional neuroanatomy of tinnitus: insights from resting-state fMRI

Doctoral thesis (2012)

La fonction mitochondriale des cellules musculaires squelettiques équines en culture : effet de l'anoxie et des neutrophiles activés.

Doctoral thesis (2012)

Introduction Horses are known to be remarkable athletes. However, to realize such repeated intense exercises, as competition horses do, and could also became a stressing condition leading to muscular ... [more ▼]

Introduction Horses are known to be remarkable athletes. However, to realize such repeated intense exercises, as competition horses do, and could also became a stressing condition leading to muscular dysfunctions but could also decrease their performances. In horses, lesions from ischemia/reperfusion are found in numerous clinical situations but also during intense exercise, the muscular oxygenation decreasing as a function of the exercise intensity. But it is during the reoxygenation, with the subsequent increase of the electron flux within the mitochondrial respiratory electron transport chain at the cessation of exercise, that an important increase of the reactive oxygen and nitrogen species (RNOS) production will be observed. The realization of such intense exercise provokes also an important systemic inflammatory reaction. Recently, some studies realized by our group on competing horses showed that intense exercise can activate the polymorphonuclear neutrophils (PMNs) which degranulate their myeloperoxidase (MPO) and elastase (ELT). The increase of MPO was not only plasmatic but also muscular, where it was associated with a decrease of the mitochondrial complex I activity, showing there a possible link between the MPO activity and the mitochondrial dysfunction in horses performing exercise. The relationship between ischemia/reperfusion, ROS production from mitochondria, muscular damages and inflammatory reaction is largely unexplored in horses. The principal objectives of this work were to study, on a primary culture of equine skeletal muscle cells obtained from muscular microbiopsies, the effect of anoxia/reoxygenation (A/R) and/or of MPO on their ROS production and mitochondrial respiratory function. Results Primary culture of equine skeletal muscle cells from muscular microbiopsies With muscular microbiopsies, we developed an efficient and convenient sampling method, usable in current practice and even on high level competing horses. By using the microbiopsies as explants, we obtained a primary culture of skeletal muscle cells, a suitable experimental model for the in vitro study of equine muscular function. Model of anoxia/reoxygenation applied on cultured equine skeletal muscle cells Thanks to the primary culture, we showed by fluorescence spectroscopy and gas chromatography, an increased ROS production by adherent cells submitted to 2 h of A/R. For the following investigations, 2 other models were designed on detached cells : a first one of cyclic A/R (2 x 30 min) and a second one of a single long period of 1 h, 2 h or 3 h of A/R. The first one showed a decrease of the routine respiration, but also of ROS production and of the mitochondrial complex I specific activity of the cells submitted to cyclic A/R. After a single long period of A/R, on the contrary, the routine respiration, the ROS production and the mitochondrial complex I specific activity of the cells were increased while the ATP production by these cells was decreased. This observation, arguing for an uncoupling of the oxidative phosphorylation, prompted us to investigate the uncoupling protein 3 (UCP3) expression by cultured cells. The indirect immunofluorescence, as well as the electrophoresis coupled with the western blot, showed that they expressed UCP3, in normoxia and after 2 h of A/R, but also that this expression varied as a function of the duration of the A/R, with a maximum observed for 2 h. The oxygraphic phosphorylation control protocol (PCP) applied on detached cells showed an increase of their routine but also of their non phosphorylating (after ATP synthase inhibition) respirations after a single long period of 2 h A/R. Their maximal respiratory capacity, per contra, decreased significantly. When regarding the flux control ratios (FCR, related to maximal respiratory capacity), we confirmed that cells submitted to 2 h of A/R need to function more to keep stable their energetic state (increase of the part of their maximal respiratory capacity used for oxidative phosphorylation because of a lesser efficiency). Inflammatory model Equine neutrophils activation in whole blood All the activation systems used, 12-phorbol 13-myristate acetate (PMA), cytochalasin B with N-formyl-methionyl-leucyl-phenylalanine (CB/fMLP), tumor necrosis factor-alpha (TNF- α), lipopolysaccharides (LPS) and LPS with TNF-α, induced a significant degranulation of total MPO by the PMNs activated in whole blood. Only the combinations CB/fMLP and LPS/TNF-α caused a significant release of active MPO. For the release of ELT by activated PMNs, only the action of the PMA was significant. Use of purified active equine MPO Initially, we showed that MPO incubated with equine skeletal muscle cells was able to bind to the cell membranes, but furthermore, thanks to the differential centrifugation protocol, that we demonstrated that it was able to enter within the cells, because we found it in the cytosolic fraction. Our following experiences showed that it was able, even alone, to increase the ROS produced by the cells, as demonstrated by fluorescence and gas chromatography. Furthermore, MPO worked harder than Horseradish peroxidase (HRP), our "peroxidasic control". The MPO seemed also to alter the mitochondrial respiratory function of cultured cells. Anyway, thanks to the oxygraphic PCP protocol, we showed that MPO alone decreased mostly their routine respiration and their maximal respiratory capacity. Paradoxically, we seen that it increased the part of the maximal respiratory capacity used for routine and non phosphorylating respirations. The second oxygraphic protocol, designed on permeabilized cells, seems to confirm these observations. Compared to control cells, the MPO-treated cells had a increased non phosphorylating respiration and a decreased maximal respiratory capacity, particularly via the mitochondrial complex I. Combined model: anoxia/reoxygenation in inflammatory conditions With fluorescence spectroscopy as well as with gas chromatography, the MPO amplifies the ROS production already increased with the A/R alone. Furthermore, with a 3,3-diaminobenzidine (DAB) coloration, we showed the persistence of the MPO (and of the HRP), within the cells, even after 2 h of A/R. The oxygraphic PCP protocol confirms that MPO seems to exacerbate the damage initiated by A/R. Thus, compared to what we observed with A/R alone, the addition of MPO causes a further decrease of the routine respiration and the maximal respiratory capacity of the cells and increases their non phosphorylating respiration. These observations, along the lines of an important mitochondrial dysfunction, were confirmed when regarding the FCR. Thus, MPO-treated cells, submitted to A/R need to use a greater part of their maximal respiratory capacity for routine respiration, but a greater part of it was also used for non efficient respiration. So, these cells need to work more intensely to keep stable their energetic state, what is reflected in our protocol by an increased part of the maximal respiratory capacity used for oxidative phosphorylation compared to what we observed after A/R alone. Conclusion and perspectives During intense exercise, some physiopathological conditions, inducing important mitochondrial and energetic alterations, seem to gather within the muscle of sport horses. As showed by our work, because of its implication in the mitochondrial regulation at the respiratory level as well as for RNOS production, and of its particular sensibility to nitration, the mitochondrial complex I could play a pivotal role. Although our results clearly indicate that MPO, by exacerbating the deleterious effects of A/R, is detrimental to cellular and mitochondrial functions, further precisions are needed to confirm the specific implication of mitochondrial complex I in the observed phenomena. The results obtained by our group in vivo on competing horses lead the way in this direction but, the adaptation of the oxygraphic protocol on permeabilized cells, combining A/R with the action of MPO, will help to confirm, in vitro, the hypothesis. On another way, the effect of nitration or nitrosation on the mitochondrial complex I will need to be further investigated. Finally, to consider in a largest way the action of the PMNs on the mitochondrial function, it will be interesting to use the whole blood model of PMNs activation in co-culture with equine skeletal myoblasts. By this way, the action of other inflammatory factors or mediators could be studied in conditions nearly to the ones observed in vivo. [less ▲]

Etude des mécanismes responsables du comportement agrégatif d’Harmonia axyridis (Pallas) (Coleoptera : Coccinellidae)

Doctoral thesis (2012)

The negative impacts linked to the introductions of the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), progressively increasing in Europe and in North America, it is urgent to find a way to ... [more ▼]

The negative impacts linked to the introductions of the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), progressively increasing in Europe and in North America, it is urgent to find a way to manage its populations. The social interactions involved in its aggregative behavior remain misunderstood although a better understanding of the semiochemicals the ladybeetles use during this phenomenon could lead to the development of new control methods. Therefore, the main objective of this thesis was to improve the understanding of the mechanisms set up by H. axyridis during its aggregative stage. Firstly, we have demonstrated the use of two different area markings by this species during its overwintering. The first one, laid by the ladybeetles while walking, lead conspecifics towards aggregation sites whereas the second one, deposited inside these sites, ensures the cohesion of the cluster. These markings are made up of saturated, mono- and diunsaturated hydrocarbons. Among these chemicals, it seems that the unsaturated hydrocarbons, and in particular the ones containing two double bonds, present a greater biological activity. However, the response of H. axyridis towards these chemicals depends on the insect physiological state. In the second instance, we have showed for the first time that H. axyridis presents a permanent aggregative behavior. The hydrocarbons laid by the ladybeetles during their displacements do not play any role in this behavior during summer conditions. On the other hand, conspecific elytral compounds and, in a lesser extent, physical contact, are well involved. Moreover, all our experiments have pointed out that visual elements play a major role in this social behavior and so, have also to be taken into account in the design of traps to control the populations of this invasive species. [less ▲]

Coastal pollution of the Mediterranean and extension of its biomonitoring to trace elements of emerging concern

Doctoral thesis (2012)

The Mediterranean Sea, a semi-enclosed sea with densely populated coasts, is submitted to numerous anthropogenic pressures: among them, the chemical pollution by traces elements. These pollutants, coming ... [more ▼]

The Mediterranean Sea, a semi-enclosed sea with densely populated coasts, is submitted to numerous anthropogenic pressures: among them, the chemical pollution by traces elements. These pollutants, coming from our continental activities, are transported through rivers or by air and accumulate in seas and oceans where they mainly affect coastal areas. During the 70ies, scientists suggested to use organisms, in particular mussels of the genus Mytilus, in order to evaluate the status of chemical contamination of coastal ecosystems. Biomonitoring was born. Since, many monitoring studies were published using various animal and vegetal species. Two of the most studied bioindicators species in the Mediterranean are the marine magnoliophyte Posidonia oceanica and the Mediterranean mussel Mytilus galloprovincialis. Monitoring studies with these two species have mainly focussed on contaminations by Cr, Ni, Cu, Zn, Cd, Pb (Mytilus galloprovincialis and Posidonia oceanica), Fe (Posidonia oceanica), As, V and Ag (Mytilus galloprovincialis). However, other trace elements like Be, Al, Mn, Co, Se, Mo, Sn, Sb and Bi have been subject to nearly no ecotoxicological survey. Furthermore the worldwide evolution of our technologies and of our lifestyle increases the extraction and production of trace elements (notably to answer needs of developing countries). The biomonitoring of the pollution by trace elements is henceforth a topical subject. The overall objective of this work was therefore to evaluate the potential use of Mytilus galloprovincialis and Posidonia oceanica as bioindicators to monitor the Mediterranean coastal pollution by Be, Al, Mn, Co, Se, Mo, Sn, Sb, Bi, Fe, As, V, and Ag. These trace elements, mostly little studied, can be categorized as elements of “environmental emerging concern”. A time-integrated efficient monitoring of trace elements requires the continuous survey of their environmental levels; we therefore also measured levels of trace elements classically monitored with these two species. Mytilus galloprovincialis and Posidonia oceanica complement each other in monitoring surveys. Both species accumulate pollutants dissolved in the water column. Posidonia oceanica, rooted in the seafloor, accumulates moreover pollutants stored in sediments in the long term. Mytilus galloprovincialis, as a filter feeder, further accumulate particulate pollutants suspended in the water column. The combined use of both bioindicators therefore provides a global view of the health status of the coastal environment (water, sediments, suspended matter). Our first goal was to measure, at the scale of the French Mediterranean littoral, the spatial variability of trace element contents in Posidonia oceanica, and to determine if trace elements of environmental emerging concern threaten the chemical integrity of coastal ecosystems. We observed that the large majority of trace elements little or no monitored with Posidonia oceanica showed an equivalent to higher spatial variability than elements classically monitored with that species. We also showed that the spatial variability could be associated to specific anthropic activities like agriculture (Mo), mining (Sb), storage and refinement of oil products (V), or the presence of harbours and major urban centres (Sn, Bi). Their monitoring, along with the one of trace elements classically studied in the Mediterranean, turns out to be essential. In addition, the in-depth study of the contamination state of the Calvi Bay (Northwestern coast of Corsica, France), enabled us to define (or re-define) this site as a reference site for the monitoring of the chemical pollution by trace elements in the Northwestern Mediterranean. We further studied the physiological mechanisms of accumulation, storage and excretion of trace elements by Posidonia oceanica. In situ contamination of seagrass bed portions allowed us to model the rapid kinetics of accumulation of contaminants by Posidonia oceanica shoots. Compartments of the plant answered differently to pollutant exposures. So, adult and senescent leaves assimilated pollutants less rapidly than young actively growing leaves. Trace elements, once accumulated, could be redistributed between the plant compartments, notably towards the rhizomes-roots systems buried in sediments. Our results experimentally showed that these below-ground organs could therefore play the role of biological archives for many elements. At the end of periods of exposure to pollutants, kinetics of decontaminations of Posidonia oceanica shoots were relatively fast and depended notably on the duration of the exposure to trace elements, on their toxic or essential character and on the studied compartment. We concluded that Posidonia oceanica was a sensitive bioindicator for the monitoring of the past and present coastal pollution by trace elements. We showed that Mytilus galloprovincialis efficiently accumulated trace elements of environmental emerging concern as well as elements classically studied with this bioindicator species. The physiology of mussels further conditioned their answers to pollutant exposures. Their reproductive cycle dissolved trace element concentrations during the massive production of gametes and conducted to differences more or less important between individuals of both sexes. The conservative character of the distribution of trace elements between the different body compartments of Mytilus galloprovincialis suggested an important physiological regulation of their internal levels. Finally, the size of mussels used in this study, harvested from an aquaculture farm, did not noticeably influence inter-individual concentrations, all mussels of a same rope having approximately the same age. In conclusion, this study enabled to improve and enlarge our state of knowledge about the monitoring of the pollution of the Mediterranean coastal environment by trace elements. In particular, both Mytilus galloprovincialis and Posidonia oceanica showed to be good candidates for the monitoring of trace elements of environmental emerging concern. [less ▲]

GRH et Organisation du travail dans les centres d'appels délocalisés au Maroc

Doctoral thesis (2012)

Considered, rightly or wrongly, as "new factories of the future", call centers generate more interest for both researchers and professionals. Their human aspects in general and their HR practices in ... [more ▼]

Considered, rightly or wrongly, as "new factories of the future", call centers generate more interest for both researchers and professionals. Their human aspects in general and their HR practices in particular is a rich field for investigations, due to the importance of their technical and social systems in their performance or their sustainability. The question of the choice of HR practices is the focus of this work devoted to the issue of HRM and work organization in offshoring call centers. It is based on nine case studies representing a varied typology of Moroccan call centers sector and three typical -ideal models adopted by them (Hard, Soft or hybrid). The choice of a model or another comes, initially, from a business strategy, a targeted market segment and a given level of outsourced value-added activities. The alignment between strategy and organization of the call center operates for each model to incorporate the same operational requirements (customer-agent interactions, colleagues) and its internal labor market. This variable is the link between work organization and HR strategy adopted. Referring to an HR model or another is conditioned by the intervention of the principal who greatly influence the decisions of managers as well as decision makers. [less ▲]

Extending Donor Pool with Donation after Cardiac Death in Kidney and Liver Transplantation:What is the Price to Pay?

Doctoral thesis (2012)

Through a series of clinical studies, this thesis aims to clarify the contribution of donation after cardiac death (DCD) to the deceased donor (DD) pool and results of kidney and liver transplantation ... [more ▼]

Through a series of clinical studies, this thesis aims to clarify the contribution of donation after cardiac death (DCD) to the deceased donor (DD) pool and results of kidney and liver transplantation coming from this donor source in Liège and Belgium. Additionally, an adapted DCD Maastricht classification is also discussed. Chapters 2.1 and 2.2 summarize the DCD procurement and transplant activity in Liège and Belgium from 2000 to 2009 with an update on data up to 2011. In Liège, DCD really contributes to the DD pool and boosts the transplant activity of the center in both kidneys and livers by on average 30%. By contrast, the steady rise in DCD activity in Belgium does not lead to major increase in the DD donation and transplantation. In other words, some kind of donor-type redistribution within the DD pool might occur. Chapters 2.2, 3.1, and 3.2 discuss the results of kidney transplantation (KT) from DCD. We demonstrate that Liège‟s experience is comparable to the national level in Belgium and does not differ from the general results in the world with regard to early graft dysfunction, medium-term graft function, graft and patient survival. The excellent results of DCD-KT are attributed to the relatively short warm and cold ischemia, favorable donor factors, and the role of hypothermic machine perfusion (in Belgian series). Chapters 4.1, and 4.2 discuss the results of liver transplantation (LT) from DCD. Liège‟s results are encouraging and apparently as good as those from donation-after-brain-death LT because of short warm and cold ischemia times. Belgian results show an increased incidence of primary non-function and ischemic cholangiopathy which is in agreement with previously published data. Chapter 5 proposes an adapted DCD Maastricht classification which maintains the original categories 1 to 4 that are now well-known and widely accepted, and adds a fifth category, so-called „DCD after euthanasia‟. Each category is divided into two or three sub-categories: sub-category A is linked to longer warm ischemia (and worse results) than sub-category B; and B versus C, respectively. In addition, sub-categories A (2A, 3A, 4A, and 5A) are mostly linked to DCD processes occurring in the ICU, which helps to understand and memorize this classification. By keeping the original skeleton of the 1995 Maastricht classification, room is left to add new sub-categories in the future, if deemed clinically relevant. [less ▲]

La littérature scientifique dans la formation des bioingénieurs à Gembloux. Vingt années d'évolution du concept d'Information Literacy

Doctoral thesis (2012)

In the education of bioengineers at Gembloux, the concept of information literacy was chosen as a guide for information literacy education. This concept describes a set of skills that allow individuals to ... [more ▼]

In the education of bioengineers at Gembloux, the concept of information literacy was chosen as a guide for information literacy education. This concept describes a set of skills that allow individuals to recognize an information need and enable them to locate, evaluate and use information needed. The concept of information literacy has evolved over the last two decades. This essay traces, through five articles and a review of the literature on the subject, the evolution of the concept. It also presents ways to implement information literacy education with a methodological approach, starting by the identification of the need of information to solve a problem to the production of a scientific communication (a homework, a conference, a scholarly paper...). This work addresses also the question of the relative invisibility of the concept of information literacy outside information specialists such as librarians. The major objective is to demonstrate that information literacy education is going well beyond the library. The skills involved are also intellectual, social and cultural skills. They include media and new information technologies and are not limited to technical or technological skills. Information literacy has become an autonomous discipline, with specific content, evolving, to talk about a didactic. Information literacy courses held in Gembloux should be considered as tools to improve the training of bioengineers and particularly the quality of their scientific publications. [less ▲]

Biolixiviation de la carrolite-Application aux minerais polymétalliques de l'Arc Cuprifère du Katanga (cas de minerais de la mine de Kamoya, Kambove) en RDC

Doctoral thesis (2012)

The present work focuses on the bioleaching of carrolite as pure mineral and application of bioleaching as an alternative technique for processing the polymetallic sulphide ores in Katanga copperbelt ... [more ▼]

The present work focuses on the bioleaching of carrolite as pure mineral and application of bioleaching as an alternative technique for processing the polymetallic sulphide ores in Katanga copperbelt (case of Kamoya deposit ores) in Democratic Republic of Congo (DRC). A preliminary study on the bioleaching of carrolite in the presence of mesophilic bacteria has highlighted the effect of the initial pH (pH = 1.5, 2.0 and 2.5), particle size (-53μm, -75+53 µm, -106+75µm), the pulp density (dp= 2.5 and 10) on the pH, the solution redox and on the dissolution performance of copper, nickel and cobalt. The results obtained at this stage showed that the initial pH, particle size and pulp density greatly influences the process of bioleaching of carrolite. The evolution of pH, solution redox and the efficiency of metals dissolution with time considering these factors indicate the importance of bacterial growth. Good bacterial activity thereby yields high metal dissolution which is being obtained at initial pH 2.0, particle size of -53μm and 2% pulp density. A second study upon the bioleaching of carrolite has allowed highlighting the metal dissolution mechanism during the bioleaching process. The evolution of the bacterial population, observations of Optical Microscope (MO), Scanning Electron Microscope (SEM), Confocal Laser Scanning Microscope (CLSM) of carrolite grains during bioleaching and spectroscopical analysis in X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) of bioleaching residues allowed us to demonstrate the role and importance of bacteria attached on the surface of carrolite grains from one hand, and ferric ions on the other hand, during the carrolite bioleaching. Strong adhesion of bacteria to the surface of the carrolite grains was observed during early bioleach stages and playing an important role in the process. This phenomenon would cause the release of ferrous ions in solution by a direct contact mechanism on the one hand and causing oxidation of ferrous ions, elemental sulfur or sulfur compounds on the other hand, compounds which would accumulate at the surface of carrolite grains. The number of free bacteria in solution increases thus promoting the oxidation of ferrous to ferric ions, which oxidize the mineral through indirect mechanism. The number of free bacteria in solution and that of attached bacteria became constant over time, suggesting a cooperative mechanism of carrolite bioleaching. Finally, a statistical study of bioleaching of polymetallic concentrate from Kamoya deposit by Taguchi methodology and analysis of variance (ANOVA) was used to investigate the effect of different physicochemical parameters (initial pH, temperature, agitation, pulp density and duration of bioleaching) on the process efficiency. The results obtained from this statistical approach showed the possibility of bioleaching application as an alternative technique for treatment of the polymetallic sulphide ores of the Katanga copperbelt in Democratic Republic of Congo (DRC) but further investigation using thermophilic bacteria should be considered to improve metal dissolution. [less ▲]

Regulation of water flow in the soil-root domain. New tools and methods

Doctoral thesis (2012)

Dynamique et perspectives de la filière cotonnière du Burundi

Doctoral thesis (2012)

Cotton cultivation was introduced in Burundi in 1919 under the Belgian mandate with the objective to monetize the rural economy and open the country to international trade. After independence (1962), the ... [more ▼]

Cotton cultivation was introduced in Burundi in 1919 under the Belgian mandate with the objective to monetize the rural economy and open the country to international trade. After independence (1962), the cotton crop continued to flourish as a vertically integrated chain from upstream to downstream in pursuing the objectives of job creation, import substitution and maximizing the added value generated by various cotton products. Since 1993, the cotton is in perpetual decline due to various factors both endogenous and exogenous to reach in 2009 the lowest level in its history. Its competitiveness is challenged by instability of the global market of cotton fiber, policies (subsidies) of large producers (China, India, USA, Pakistan, ...), competition from synthetic textile industry, the prices of agricultural inputs (fertilizers and phytosanitary products) and raw materials for industries, competition for food crops production factors which are already scarce and especially less remunerative producer prices. Survey work on a sample of 120 farms during three seasons (2007/2008, 2008/2009, 2009/2010) as well as interviews with various agents involved in the cotton sector have been conducted to understand the reasons of the decline of the cotton sector and see the adaptation mechanisms implemented in the segment "producers - COGERCO." It appears from these investigations that the cotton is not competitive with food crops. The price paid to growers is not motivating, production costs are expensive and factors of production become increasingly restrictive. COGERCO however, continues to subsidize cotton without benefit. In this context the majority of cotton producers combine beans or cowpeas with cotton to take advantage of subsidies (inputs, management, ...) and other benefits (loans, fields ...) that the company offers to producers without benefit to the company. The latter is in chronic deficit due to poor sector governance which is under pressure of privatization already imposed on other agro-industrial crops of the country (coffee, tea). [less ▲]

The effects of a cadmium exposure on poplar plants: A combined proteomic, physiological and biochemical approach to unravel stress-responses in poplar.

Doctoral thesis (2012)

The industrial revolution in the 1800s and the subsequent industrialization had the consequence of an anthropogenic release of many organic and inorganic pollutants. Among these pollutants, cadmium is ... [more ▼]

The industrial revolution in the 1800s and the subsequent industrialization had the consequence of an anthropogenic release of many organic and inorganic pollutants. Among these pollutants, cadmium is very problematic due to its high toxicity. It can induce significant damage to the vegetation and an accumulation in farmland introduces the pollutant into the food chain. This creates a possible major health risk for humans. Poplar plants, as a member of the Salicaceae family, seem to possess a certain tolerance to this toxic metal and accumulate significant amount in their aerial parts, making poplar a possible candidate for phytoremedation. The metabolic and physiological impact of cadmium have been studied as well in field trials as in controlled laboratory conditions, but mostly in clearly targeted studies focusing on a few key aspects. The recent advent of more global techniques such as transcriptomics and proteomics, make it possible to obtain new results. In the thesis presented here, a proteomic study of the short-term and long-term effects of cadmium on poplar leaf and roots metabolic processes in controlled laboratory conditions was carried out. With the help of this technique, complemented with biochemical and physiological approaches and with morphological observations, it was possible to obtain results on the stress-coping mechanisms underlying an acute first response, but also on the more general adaptation mechanism which make it possible for the poplar plants to tolerate significant amounts of cadmium. Results showed a negative impact on important cell processes like photosynthesis and ATP synthesis and the antioxidant system, explaining the impaired growth. Similar results could be obtained in roots, although the stress seemed much more acute, as evidenced by the stronger accumulation of typical stress proteins (i.e. heat shock proteins). In a final set of experiments a controlled combination of two stresses (cadmium and nonlethal chilling stress; 4°C) allowed separating specific cadmium responses from a more general stress response. Cadmium had a much more severe impact on plant survival when combined with an additional constraints. In this present work, the procedures, results and conclusions obtained are presented in detail. [less ▲]

Modélisation de l’impact de la structure des vents stellaires sur le spectre X et visible des étoiles massives

Doctoral thesis (2012)

Optimisation de l'utilisation des ressources en eau du bassin du Kou pour des usages agricoles

Doctoral thesis (2012)

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

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

Alternative possible à la production traditionnelle du coton en Afrique dans une perspective de développement durable? Le cas du système de production biologique et équitable au Mali

Doctoral thesis (2012)

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

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

Development of a transmission model of Murid herpesvirus 4

Doctoral thesis (2012)

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

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

Ionosphere Modelling for Galileo Single Frequency Users

Doctoral thesis (2012)

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

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

Adaptations structurales et fonctionnelles aux températures extrêmes au sein de la famille des alpha-amylases chlorure-dépendantes

Doctoral thesis (2012)

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

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

Structure and Lattice Dynamics of Thermoelectric Complex Chalcogenides

Doctoral thesis (2012)

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

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