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See detailEvaluation des charges polluantes (domestiques et industrielles) arrivant au lac Kivu dans la ville de Bukavu, RD. Congo
Lina Aleke, Alex ULg

Doctoral thesis (2016)

Dans les pays en développement (PED) en général, et plus particulièrement en République Démocratique du Congo (RDC), le développement des villes et l'augmentation des populations urbaines se font avec une ... [more ▼]

Dans les pays en développement (PED) en général, et plus particulièrement en République Démocratique du Congo (RDC), le développement des villes et l'augmentation des populations urbaines se font avec une rapidité telle que l'accessibilité à l'eau potable et à l'assainissement de basepose un problème croissant de sante publique et de bien-être des populations. Le manque d'expertise et des moyens techniques et/ou financiers ne permet pas de mettre en place des programmes cohérents et adaptés aux réalités et défis que connaissent ces pays. C'est dans cette optique que la présente étude qui porte sur la caractérisation des eaux résiduaires domestiques et industrielles générées dans la ville de Bukavu, a été menée en vue d'évaluer les flux des pollutions arrivant dans le lac Kivu. Différents axes de recherche ont été ainsi exploités pour répondre a cet objectif. Ce sont :l'évaluation de l'assainissement non collectif (ANC),la caractérisation des flux polluants générés par les activités domestiques et industrielles, etl'analyse critique des atouts naturels (physiques, géologiques, hydrogéologiques, etc.) de la ville de Bukavu en vue de mettre sur pied des filières permettant un assainissement correctet la protection du lac Kivu. L'évaluation de l'assainissement a été basée sur une démarche sociologique faisant appel à des techniques d'enquêtes et d'observation deterrain. Une approche d’évaluation par un indicateur découlant de la combinaison des indicateurs mis en place au prorata des trois maillons composants une filière d’ANC (amont, intermédiaire et aval) a été utilisée. Les résultats obtenus montrent un faible niveau d'accès à l'eau potable et à l'assainissement de base qui serait lié à des facteurs historiques, physiques, politiques, et socio-économiques. De plus, un effort considérable reste à faire pour la gestion du maillon aval car la gestion des boues produites se fait pour le moment de manière non conforme. Par ailleurs, la densité de la population, en pleine croissance, nécessite une politique de construction de logements bien appropriée. Réalisée au niveau des émissaires domestiques (ITFM, Rukumbuka, PIR, Nyamugo et Bagira) et des rivières (Bwindi, Tshula, Wesha et Kahwa) qui traversent Bukavu, la caractérisation des flux de pollutions domestiques a été menéeau travers des méthodes physicochimiques et microbiologiques. Elle a permisd'apprécier l'importance des risques sanitaires qu'encourent les habitants de Bukavu dans leur quotidien, ainsi que l'ampleur des pressions que subit le lac qui en est le réceptacle. De la même manière, notre étude s'est intéressée aux flux produits des pollutions industrielles brassicoles et pharmaceutiques, suivant une approche physicochimique. Il ressort de ces analyses que les émissaires domestiques constituent le cadre de premier choix adopté par les habitants pour le rejet de leurs déchets. Ce faisant, les rivières de la ville font l'objet d'importantes pollutions engendrées par les activités domestiques, et constituent des égouts à ciel ouvert. Les flux évacués et arrivant quotidiennement dans le lac vont de 2165 kg (rivière Bwindi) à 5974 kg DBO5 (riviere Kahwa) en saison sèche, et de 5303 kg (rivière Bwindi) à 14270 kgDBO5 (rivière Kahwa) en saison de pluie, correspondant aux charges totales respectives de 7468 kg DBO5 et 20244 kg DBO5. Les flux des pollutions microbiologiques ont été évalués a 2,3.109 UFC/EH DBO5 pour la rivière Bwindi et 6.109 UFC/EH DBO5 pour la rivière Kahwa en ce qui concerne les coliformes fécaux, et 2800 œufs/EH DBO5 (rivière Bwindi) et 4185 œufs/EH DBO5 (rivièreKahwa) pour les parasites.En outre, 11 taxons de parasites ont été identifiés. Ce sont : Entamoeba coli, Giardia lamblia, Entamoeba histolytica, Ascaris sp. (taxon le plus distribué), Ankylostoma sp., Strongyloides sp., Trichuris trichiura, Hymenolepis nana, Hymenolepis diminuta, Taenia saginata et Schistosoma mansoni. Recevant les eaux de 4 de 5 émissaires domestiques étudiés, la rivière Kahwa s'est avérée comme la plus polluée des rivières de Bukavu. Concernant les pollutions industrielles, pour chaque litre de boisson (bières et boissons gazeuses confondues), la société brassicole Bralima utilise entre 4,7 et 5,7 l d'eau, avec une moyenne de 5,1 l.Les pollutions spécifiques s'établissent entre 1,2 et 1,6 kg DCO/hl, et 0,2 et 0,4 kg MES/hl de produits finis, avec unecharge globale évaluée 194,1 kgDCO par jour, avant traitement. L'abattement des pollutions dans la station d'épuration de cette société brassicole devrait être amélioré en vue de réduire ses pressions sur le lac et les risques sanitaires auxquels sont exposées les populations. Quant à la Pharmakina, la charge globale des pollutions, évaluée à 1229,2 kgDCO par jour, arrive dans le lac Kivu sans aucun traitement préalable, constituant ainsi de graves menaces environnementales et écologiques imputables à sa responsabilité. [less ▲]

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See detailDynamique des flux de carbone entre l'atmosphère et des écosystèmes ouest-africains: cas des forêts et savanes sous climat soudanien au Bénin
Ago, Expédit Evariste ULg

Doctoral thesis (2016)

In West Africa as elsewhere in other parts of the world, natural and anthropogenic ecosystems are the main sources for energy, building poles and livestock fodder. They probably behave like some nets ... [more ▼]

In West Africa as elsewhere in other parts of the world, natural and anthropogenic ecosystems are the main sources for energy, building poles and livestock fodder. They probably behave like some nets carbon sinks, but there are only few studies that have focused on their carbon exchanges with the atmosphere. Preserving terrestrial ecosystems has proven essential to any emissions mitigation policy of green house gases, notably CO2. This thesis focuses on the analysis of the CO2 fluxes in three contrasting types of the ecosystem under a Sudanian climate in Benin. Specifically, it was a cultivated forest, a protected forest and a cultivated savannah. Turbulent CO2 fluxes were measured by an eddy-covariance system placed above the ecosystems. The measurements were made during variable periods of 17 months (cultivated forest), 18 months (protected forest) and 29 months (cultivated savannah). The three studied sites have been equipped by the hydro-meteorological observatory AMMA-CATCH and the national project Ouémé 2025. The CO2 fluxes data were completed by some meteorological measurements and by an inventory of dominating species the three sites. Fluxes were examined on the basis of the two main seasons imposed by the cycle of West African Monsoon. The spatial (local and regional) and temporal (hour, seasonal, annual and inter-annual) scales were considered according to the sites. Water was the main factor controlling the dynamic of the terrestrial West African ecosystems. At the daily scales, the radiation was the main driving variable of the net CO2 fluxes. Besides that radiation control, a clear relationship was observed between the net CO2 fluxes and the canopy conductance. A limited impact of saturation deficit was observed, notably during the afternoon. The soil moisture was the main factor governing the ecosystem respiration. However, no clear dependency of the ecosystem respiration on the temperature was observed at hourly scale. After long dry periods, the ecosystem respiration increased immediately in response to the first significant rains. The CO2 fluxes and the characteristics of the protected forest were always higher than those of the cultivated savannah at the daily and seasonal scales. At the annual scale, while the protected forest (Bellefoungou) and cultivated savannah (Nalohou) sequestered an average of 640 ± 50 and 232 ± 27 g C m-2, respectively considering the period of the measurements, the cultivated forest was in equilibrium with 29 ± 16 g C m-2. Overall, the three studied ecosystems were more efficient during morning and wet season than during afternoon and dry season. Finally, this study revealed that the inter-annual variability of the carbon sequestration by the cultivated savannah was mainly controlled by the ecosystem respiration variability in relation to the soil water content variation. [less ▲]

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See detailDe la magie au magique. Conscience, réalité-humaine et être-dans-le-monde chez Sartre (1927-1948)
Dassonneville, Gautier ULg

Doctoral thesis (2016)

This research deals with Sartre's early existential philosophy by resituating it in the field of French post-Comtian philosophy in the early twentieth century and by re-establishing an anthropological ... [more ▼]

This research deals with Sartre's early existential philosophy by resituating it in the field of French post-Comtian philosophy in the early twentieth century and by re-establishing an anthropological moment in which the issue of magic is explored in the psychological and social sciences. Following the different paths of the conceptual exchange through which the notion of magic becomes that the magical in Sartre's view, we study three poles of sartrian phenomenological ontology : intentional consciousness, human reality and being-in-the-world. The hypothesis advanced by this thesis is that the magical, according to different modes ranging from topicalization through obliteration, plays a determining role in the elaboration of existentialism whose genesis is traced here from Sartre's very first writings in 1927.  Faced with the legacy of a positivist anthropology in terms of an analytical methodology, Sartre privileges a synthetic approach and conceives consciousness in its affective and irrational aspects. Images of magical thought are called upon for rethinking openness to the world of consciousness and its relationship to itself and to Others. Returning to Sartrian anthropology, we question how consciousness can be grasped as an irreflexive and absolute spontaneity and how human reality is interpreted through its attitudes and behaviours; in particular through the way it faces its own freedom which is fundamentally and irremediably exposed to contradiction. This structure of human reality as existential project leads Sartre to reconsider being-in-the-world as based in originary dispossession through which ontology is brought back to the magical. [less ▲]

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See detailAspects socio-économiques et technique de la conservation du mouton Koundoum au Niger
Hamadou, Issa ULg

Doctoral thesis (2016)

Résumé Le mouton Koundoum représente le principal mouton à laine du Niger et est exclusivement élevé dans les îles et sur les bords du fleuve Niger, depuis la frontière du Mali jusqu’à Niamey. Il ... [more ▼]

Résumé Le mouton Koundoum représente le principal mouton à laine du Niger et est exclusivement élevé dans les îles et sur les bords du fleuve Niger, depuis la frontière du Mali jusqu’à Niamey. Il constitue une source de nourriture et de revenus pour les agriculteurs ruraux de cette zone. Cette race est reconnue pour sa production de laine et sa remarquable adaptation à l’humidité dans la vallée du fleuve Niger. Peu d’informations sont disponibles sur les caractéristiques de cette race alors qu’on assiste à une régression drastique de son effectif. La documentation des caractéristiques d’une race est importante pour son utilisation et sa conservation. Cette étude a été entreprise pour documenter (i) le système de production et les caractéristiques morphobiométriques du mouton Koundoum, (ii) les préférences des éleveurs et leur disposition à payer ou à recevoir une compensation pour les caractéristiques des ovins, (iii) les caractéristiques de reproduction du mouton Koundoum et (iv) les points de vue des parties prenantes potentielles susceptibles de contribuer à la réussite de la gestion et la conservation de la biodiversité des animaux d'élevage au Niger. Ainsi, pour caractériser la race et comprendre son contexte de production, une enquête a été menée auprès de 104 ménages dans quatre communes le long du fleuve Niger (Kollo, Tillabéry, Say et Tera) pendant la période d’août à décembre 2011. Neuf mesures corporelles, comprenant le poids vif, ont été prises sur 180 moutons Koundoum (101 femelles et 79 mâles). L’effectif des troupeaux de moutons varie de 2 à 60 têtes, avec une taille moyenne de huit animaux et les deux tiers des troupeaux comptant moins de 10 animaux. Principalement alimentés sur les pâturages naturels, 85,6% des troupeaux reçoivent des résidus de récolte en supplément. Seul l'accouplement naturel est pratiqué par les éleveurs et les soins vétérinaires sont limités aux anti-helminthiques et à une pharmacopée traditionnelle. L'affiliation fréquente des éleveurs à des associations professionnelles apparait comme un facteur favorable à la mise en œuvre d'un programme collectif de conservation. Le mouton Koundoum est de robe blanche ou noire, avec une fréquence plus élevée pour la couleur noire (75,6%). Les pendeloques sont présentes dans les deux sexes à des fréquences similaires, d’environ 14 %. Toutes les variables biométriques sont positivement et significativement corrélées entre elles. Le périmètre thoracique montre la meilleure corrélation avec le poids vif, tant chez les mâles que chez les femelles. Trois variables ont été sélectionnées pour la prédiction du poids vif: le périmètre thoracique, la hauteur au garrot et la longueur de la croupe. Il ressort de cette étude que la conservation in situ de la race Koundoum s’annonce comme très problématique, du fait du manque d’opportunités de marché pour la laine et de disposition des petits éleveurs à élever le mouton Koundoum en race pure. Dans le but d’objectiver ce dernier frein, la seconde étude, conduite dans la même zone de septembre 2012 à février 2013, caractérise les préférences des éleveurs pour les béliers reproducteurs et aborde leur disposition à contribuer au programme de conservation du mouton Koundoum à travers leur appréciation quantifiée des principales caractéristiques phénotypiques de la race. L'outil de l'empilement proportionnel est utilisé d'abord dans 11 groupes de discussion focalisée réunissant des éleveurs autour de la question des principaux critères de sélection de béliers reproducteurs. La méthode d'analyse conjointe multi-attributs est ensuite appliquée avec 168 propriétaires de moutons. L'estimation économétrique de la fonction d'utilité des éleveurs est réalisée avec un modèle logit conditionnel et la disposition à payer est calculée par le rapport entre chaque coefficient d’utilité des caractères et de l’attribut monétaire. Les résultats révèlent un fort rejet par les éleveurs des caractéristiques comme la laine et la robe noire et montre ainsi la faible acceptabilité d'un programme de conservation in situ. Quelques éleveurs avec une préoccupation particulière pour la conservation de la race, pour des motifs culturels, peuvent néanmoins adhérer à un tel programme de conservation, qui devrait être principalement fondé sur des stratégies ex situ. En vue de ces stratégies ex situ, il est nécessaire d’étudier les caractéristiques de reproduction chez le mouton Koundoum. La troisième étude a ainsi été conduite en station, à la ferme expérimentale et de recherche de la Faculté d’Agronomie de l’Université Abdou Moumouni de Niamey (Niger) pendant la période de décembre 2013 à avril 2014. L’étude a plus précisément déterminé les caractéristiques du cycle œstral de la brebis et quelques caractéristiques spermatiques du bélier de la race Koundoum du Niger. Ainsi, seize brebis et huit béliers Koundoum ont été utilisés pour cette étude. Les brebis ont été soumises à une observation biquotidienne de leur comportement sexuel en vue de détecter les œstrus, à l’aide de béliers boute-en-train. Les échantillons de sperme ont été recueillis à l’aide d’un vagin artificiel chez les béliers pendant les périodes d’œstrus des brebis. La motilité du sperme a été déterminée à l’aide d’un microscope et sa concentration à l’aide d’un spectrophotomètre. Sur les 16 brebis, 13 ont manifesté au moins une fois des comportements d’œstrus ayant une durée moyenne de 37,8 ± 5,8 heures avec une durée moyenne de cycle œstral de 18,1 ± 1,1 jours. La collecte de semence a pu être réalisée sur 4 béliers sur les 8 inclus dans le protocole. Les éjaculats collectés ont présenté un volume moyen de 1,03 ± 0,3 ml, une motilité de 3,4, et une concentration de 1322 ± 544 millions/ ml. La connaissance de la durée du cycle et de l’œstrus est un élément de base pour la maîtrise de la fonction sexuelle des brebis. La difficulté de collecte de la semence de béliers Koundoum devra être prise en compte dans les plans de conservation par cryogénisation de paillettes. Les informations obtenues à travers cette étude sont une base permettant de poser les premiers jalons du programme de conservation et d’amélioration de cette race. Enfin, une quatrième et dernière étude a été conduite de mars à avril 2014 pour examiner les points de vue des parties prenantes potentielles susceptibles de contribuer à la réussite de la gestion et la conservation de la biodiversité des animaux d'élevage au Niger. La recherche applique la méthodologie Q afin de révéler des discours consensuels et divergents. Après le développement de l'ensemble des affirmations sur le thème de la biodiversité (échantillon Q), les arrangements des affirmations ont été réalisées par les répondants à travers une échelle de Likert à 7 niveaux, de -3 à +3. L'analyse des données (les arrangements Q) avec le package qmethod sous le logiciel R a révélé trois points de vue distincts des parties prenantes sur l'importance de la biodiversité dans l'agriculture et l'élevage, l'équilibre entre le progrès et la conservation et les différentes méthodes de conservation. L'étude montre un consensus apparent sur l'importance de la biodiversité, qui est évidemment un sujet promu dans le pays. Derrière le consensus, différents discours sont définis qui semblent tous divisés par le même dilemme entre la conservation et le développement économique. Comprendre les différentes réponses et poids attribués à chacun des composants du dilemme guidera des campagnes de sensibilisation et aidera à identifier les intérêts divergents des parties prenantes. [less ▲]

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See detailExperimental and Numerical Characterization of Damage and Application to Incremental Forming
Guzmán Inostroza, Carlos Felipe ULg

Doctoral thesis (2016)

Nowadays, product manufacturing can be divided into two groups: relatively simple products produced in a large production chain and complex (specialized) components produced in reduced batches. Within the ... [more ▼]

Nowadays, product manufacturing can be divided into two groups: relatively simple products produced in a large production chain and complex (specialized) components produced in reduced batches. Within the second group, prototyping through incremental sheet forming (ISF) has been subject of several studies. ISF refers to processes where the plastic deformation occurs by repeated contact with a relatively small tool. A crucial aspect in the ISF processes is that the final shape is determined only by the tool movement. The focus of this research is the single point incremental forming (SPIF) process variant, where a clamped sheet metal is deformed by using a relatively small spherical tool. SPIF has several advantages over traditional forming, such as the high formability attainable by the material. Different hypothesis haven been proposed to explain this behavior, but there is still not a clear and definitive understanding of the relation between the particular stress and strain state induced in the material during SPIF and the material degradation leading to localization or fracture. In this thesis, a fundamental research is proposed using the finite element (FE) code LAGAMINE, developed within the University of Liège. Numerical implementation and validation of the Gurson-Tvergaard-Needleman (GTN) damage model into this FE code is performed. An experimental test campaign is developed to characterize plastic and damage behavior and to validate the damage model for the DC01 steel grade. Finally, this damage model is applied to simulate the SPIF process in order to verify if it is capable to predict failure. The thesis discusses the material parameter identification for classical plasticity models, describing the anisotropy and hardening behavior of the sheet metal. The derivation of the equations of the numerical damage model and the efficiency of the implementation is presented in great detail. A methodology for the numerical parameter identification of the damage model is proposed, including microscopic measurements by optical microscopy and strain and displacement field measurements by digital image correlation (DIC). The identified Gurson model is applied to simulate standard SPIF geometries, like the line, cone and pyramid tests. The simulations are performed using the solid-shell element formulation and validated in terms of shape and force prediction. Literature reviews of the Gurson model and the SPIF process are also included. The experimental results show that the selected material (DC01 steel sheet) exhibits a slight anisotropic behavior and work-hardening stagnation on cyclic tests. The performed microscopic measurements are not representative of the actual damage, but they give a qualitative estimation of the physical mechanism of fracture. The initial porosity of the material was determined using optical microscopy measurements in the base material. The numerical implementation of the model is developed with all variables integrated in an implicit way, based on the backward Euler scheme. Nucleation, coalescence and shear extensions implementations are validated by results obtained from the literature. The macroscopic campaign allowed to identify the parameters for nucleation, coalescence and shear. An unique set of results matching all experiments was not possible to obtain, so different sets of parameters are retrieved following an approach that includes inverse modeling and sensitivity analysis. A numerical-experimental comparison of strain values in the loading direction shows that the model is able to correctly predict the strain distribution except during localization of the strain. Globally, the obtained set of material parameters is in good agreement with the experimental results. For SPIF FE simulations, the results of the shape prediction are in good agreement with the experimental results, both for the line and pyramid test. Nevertheless, the force prediction is too high compared to reference values. On the other hand, the GTN model is capable to detect failure in a pyramid and a cone, but the prediction is too premature compared to the experimental failure angle for the same material and geometry. An accurate prediction of failure for the SPIF process was not possible to achieve. The GTN model extended to shear presents inherent flaws that prevent an accurate prediction of the failure angle for the SPIF process. Hence, an extensive research on the damage mechanisms leading to fracture for SPIF cannot rely (only) on the GTN model. The classical coalescence model of the GTN model is insufficient to correctly predict failure. Hence, it is recommended that further analysis concentrates on the description of this particular stage of damage evolution. During the development of this thesis, a robust implementation of the GTN model into the FE code LAGAMINE was done, including an extensive experimental database of microscopic and macroscopic measurements for the DC01 steel sheet. Other phenomena can be explored thanks to this model. [less ▲]

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See detailCo-simulation of Electromagnetic Transients and Phasor Models of Electric Power Systems
Plumier, Frédéric ULg

Doctoral thesis (2016)

This study investigates and improves methods used for the combination of phasor and electromagnetic transients time domain simulations of power systems. It involves the study of the protocols of ... [more ▼]

This study investigates and improves methods used for the combination of phasor and electromagnetic transients time domain simulations of power systems. It involves the study of the protocols of computation, the comparison of the different kinds of boundary conditions used to represent one sub-system when simulating the other, and the interfacing of phasor and electromagnetic transients models. The Nordic system has been used to realize the tests. Illustrative simulation results are reported for the case of a single and of multiple boundary buses between the sub-systems. [less ▲]

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See detailEfficient methods for large-scale time-harmonic wave simulations
Marsic, Nicolas ULg

Doctoral thesis (2016)

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See detailBeyond the Line: Murray Bail's Spatial Poetics
Herbillon, Marie ULg

Doctoral thesis (2016)

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See detailLa justice pénale internationale à l'épreuve des droits humains : étude de la privation de liberté devant la Cour pénale internationale
Deprez, Christophe ULg

Doctoral thesis (2016)

Entre instrument de protection des libertés fondamentales et menace à l'égard de ces mêmes libertés, l'activité pénale est un phénomène cerné de paradoxes. Les règles de protection des droits humains ont ... [more ▼]

Entre instrument de protection des libertés fondamentales et menace à l'égard de ces mêmes libertés, l'activité pénale est un phénomène cerné de paradoxes. Les règles de protection des droits humains ont notamment pour ambition de contenir ces paradoxes : en encadrant le pouvoir de contrainte que l'autorité répressive peut exercer sur les individus, ces normes essentielles doivent permettre de garantir une justice pénale qui demeure fidèle aux principes qu'elle entend défendre. Mais quelle peut bien être l'emprise des droits humains sur l'action du juge pénal international ? Dès lors que le droit international des droits de l'homme a été pensé et conçu pour circonscrire l'autorité des États, qu'en reste-t-il lorsqu'on cherche à l'appliquer – en particulier – à la Cour pénale internationale ? Dans quelle mesure et sur la base de quel(s) fondement(s) juridique(s) cet acteur répressif d'un genre nouveau est-il tenu au respect de règles auxquelles il n'a pas expressément souscrit ? Les spécificités de la justice pénale internationale – et, singulièrement, la gravité des crimes ayant favorisé son émergence – réclament-elles une adaptation du niveau de protection accordé aux suspects et accusés internationaux ? Quel accueil le Statut de la Cour pénale internationale et les règlements qui l'accompagnent réservent-ils aux standards pertinents, en particulier en matière de privation de liberté ? La jurisprudence de la Cour révèle-t-elle une pratique conforme à ces standards ? Le projet de recherche vise à apporter un éclairage sur l'ensemble de ces questions et, ainsi, à mettre la justice pénale internationale à l'épreuve des droits humains. [less ▲]

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See detailStimuli-responsive self-assembled macromolecular systems with potential drug delivery applications: structural characterization by Small-Angle Neutron Scattering
Joset, Arnaud ULg

Doctoral thesis (2016)

Colloids are known since the early 19th century but they have mainly sparked interest since the last few decades thanks to their use in biomedical applications or in the design of new materials. The aim ... [more ▼]

Colloids are known since the early 19th century but they have mainly sparked interest since the last few decades thanks to their use in biomedical applications or in the design of new materials. The aim of this thesis is the study of stimuli-responsive colloids by Small-Angle Neutron Scattering (SANS). The stimuli may be the pH, the temperature, the addition of a ligand or of metallic ions or a combination of them. SANS is a useful technique which provides information about the internal structure of nano-objects but also, if appropriate conditions are met, about the organization of the objects in solution. Several samples built from the auto-assembly of block copolymers and liposomes have been prepared. The macroscopic cross sections have been modeled with the aim to infer the main structural parameters of the samples: the global size, the polydispersity, the structure and volume occupied by the hydrophilic and hydrophobic components inside the nano-objects. The SANS measurements have been performed as a function of the intensity of the stimulus, in order to quantify the evolution of the structural parameters. The first experimental part focuses on micellar samples built from sequenced block copolymers. The blocks may be biodegradable (e.g., poly(ε-caprolactone)), biocompatible (e.g., poly(ethylene oxide)), pH-sensitive (e.g., poly(2 vinylpyridine), poly(acrylic acid)) or temperature-sensitive (e.g., poly(N-isopropylacrylamide)). The influence of the concentration and the formation of bridges between micelles have been investigated through the analysis of metallo-supramolecular micellar gels resulting from the self-assembling of polystyrene-block-poly(tert-butylacrylate) PS-b-PtBA-tpy (tpy stands for terpyridine) block copolymers in the presence of transition metal ions. The second part focuses on the analysis of liposomes interacting with an increasing concentration of Randomly Methylated β-cyclodextrins (RAMEB). This part is divided into two chapters. The first one deals with liposomes mainly composed of dimyristoylphosphatidylcholine (DMPC) and the second one investigates the effects of cholesterol doping on the same DMPC liposomes interacting with RAMEB. [less ▲]

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See detailLa disponibilité et le prix du foncier à vocation économique: quel impact sur le développement économique en Wallonie?
Vandermeer, Marie-Caroline ULg

Doctoral thesis (2016)

This doctoral dissertation concerns the policy of land production related to economic land in Wallonia. This policy corresponds to the development of economic estates by public authorities, through ... [more ▼]

This doctoral dissertation concerns the policy of land production related to economic land in Wallonia. This policy corresponds to the development of economic estates by public authorities, through economic development agencies, to accommodate businesses. It is based on the argument according to which the availability of land – cheap if possible – is an essential factor in territorial attractiveness and competitiveness. The reflections presented in this dissertation originate from the discrepancy between this argument and the scientific literature devoted to regional development. Indeed, unlike elected representatives and economic development agencies, scholars active in the field of regional sciences only very rarely refer to the impact of the land markets on levels of development. Rather than focusing on the theme of land prices and land availability, regional scientists underline the importance of intangible factors such as innovation, education, integration into networks, territorial identity, strategic management or governance. In view of this difference, it seems appropriate to assess the spatial and economic effectiveness of the Walloon policy of land production. To do this, our wish is to objectify the real role of the availability and the price of economic land on territorial development. The first part of the dissertation develops a reflection on the literature dedicated to the relationships between land and property markets and regional development. It leads to highlight the need to develop knowledge on the impact of land and property markets on business competitiveness, regional attractiveness and economic development. The second part is devoted to the study of the availability of economic land and aims to assess the spatial effectiveness and the economic effectiveness of policies which offer an important quantity of economic land. To do this, statistical analyses were conducted on two study areas: the Northwest Europe and Belgium. As regards spatial effectiveness, the results underline significant national differentials in terms of land consumption on the one hand, while highlighting the economic sprawl that characterises France and Belgium on the other hand. As regards economic effectiveness, our results show that the impact of the development of economic estates on growth depends largely on regional contexts. Our analyses identified three regional profiles. First, urban regions, where land availability only plays a marginal role, most likely owing to the presence of numerous activities that are not very extensive spatially, yet very productive in terms of added value. Secondly, intermediate regions, where the availability of economic land has a real impact on development. However, it would appear that the profile of these regions is adapted to the presence of activities which, like logistics, generate a limited amount of jobs and added value per surface unit. Thirdly, rural regions, where the opening of land to urbanisation does not deliver the desired results. In these regions, the availability of land is not a sufficient condition for economic growth and job creation. However, we have to precise that the Belgian rural regions are rather similar to intermediate regions, probably thanks to their good connectivity. The third part concerns the study of the economic land prices. It tends to assess the impact of these prices on company property costs. The developed statistical analysis is based on annual accounts of companies with one reporting unit localised in Walloon economic estates. Results suggest that property costs are rather low. On average, they represent 1.4% of all their operational costs and 5.4% of their added-values. By contrast, labour costs are eight times higher. In addition, our analyses suggest that an increase in land prices would have a limited impact on property costs. These results tend to invalidate the hypothesis that low land prices are a key determinant of regional development. Although, property costs are highly dependent on the business sector and the size of firms. For instance, for logistic companies and small firms, property costs represent more than 10% of their added-values and 2% to 5% of their operational costs. These results tend to highlight the fact that high land prices can have a negative impact on the development of these companies. As a final point, our conclusion discusses the recommendation that economic land supply policies must be adapted according to both, the profile of the territories and the profile of the firms. Indeed, in urban regions, land supply policies aiming to supply an important land supply at low price is probably inefficient from an economic standpoint. By contrast, economic development can be expected in intermediate regions with active land policies dedicated to land-intensive activities. Moreover, a specific attention should be paid to small companies. [less ▲]

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See detailÉtude des anthocyanes de l’Hibiscus sp
Beye, Cheikh ULg

Doctoral thesis (2016)

Très répandues dans le règne végétal, les anthocyanes sont le sujet d'un grand nombre d'études. Celles-ci abordent en général les aspects concernant leur instabilité vis-à-vis des conditions dans ... [more ▼]

Très répandues dans le règne végétal, les anthocyanes sont le sujet d'un grand nombre d'études. Celles-ci abordent en général les aspects concernant leur instabilité vis-à-vis des conditions dans lesquelles elles sont employées ou l'effet bénéfique de leur consommation sur certaines pathologies chroniques. Provenant de nombreux types de fruits et légumes comestibles, elles sont extraites en vue de leur utilisation comme colorant alimentaire naturel. C'est ce dernier aspect qui a été le sujet principal de ce travail dont l'objectif était de montrer que les calices d’Hibiscus sabdariffa (H. sabdariffa) pouvaient être utilisés comme matière première pour la fabrication de colorant. Les deux principaux cultivars provenant du Sénégal présentent des différences significatives du point de vue de leur contenu en anthocyanes sur le plan qualitatif et quantitatif. L'influence des conditions de culture sur la concentration en anthocyanes a été mise en évidence. Une technique chromatographique a été utilisée pour concentrer les anthocyanes. Les résultats provenant d'expériences faites en batch agité avec une résine macroporeuse ont permis de déterminer les paramètres tels que le temps de contact nécessaire à l'atteinte de l'équilibre, la capacité d'adsorption maximale et de conclure que la résine utilisée avait une capacité d'adsorption élevée pour les anthocyanes. Suite à la fabrication du colorant, une partie importante de la masse de calices restait inutilisée alors qu'elle contenait encore des substances valorisables. Leur caractérisation a permis de montrer que les résidus des calices d'H. sabdariffa pourraient être valorisés par la production de pectines destinées au marché des additifs alimentaires, d'oligosaccharides à effet prébiotique ou de biocarburants. [less ▲]

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See detailMarket Dynamics in the Financial Industry - Essays on Interdependence and Market Timing
Biell, Elisabeth ULg

Doctoral thesis (2016)

The global financial crisis and the subsequent sovereign crisis are painful reminders of how the standards of financial markets are profoundly challenged in times of crisis. The main lesson is that the ... [more ▼]

The global financial crisis and the subsequent sovereign crisis are painful reminders of how the standards of financial markets are profoundly challenged in times of crisis. The main lesson is that the structural changes and the increased risk of shock transmissions require a more accurate risk assessment that captures the complexity of market dynamics. Based on an empirical approach, this thesis aims at loosening a priori assumptions common in literature in order to develop new methodologies that are more robust and more flexible to the dynamics of changing market conditions. The first aspect of market dynamics addressed in this thesis is the dependence structure of financial markets. The connectedness of the banking and sovereign sectors is dynamically assessed on the basis of daily CDS spreads using complex networks. We turn away from the traditional linear correlation measures and use copula theory to account for extreme events and tail dependence, which is crucial when studying credit and default risk. Through the calculation of minimum spanning trees, our methodology evaluates the transmission pattern of shocks over time and their propagation across geopolitical borders. Going beyond the analysis of simple interdependence, we apply a structural break analysis to measure a contagion index that captures increased co-movements in the network. This thesis tackles a second aspect of market dynamics which relates to major events in the life of a company affecting a company’s market value. By means of operational loss events and cross-listing decisions, we illustrate our refined event study technique that overcomes the drawback of a priori assumptions about the event date. In addition to the reaction magnitude, our approach investigates the point in time when most of the market reaction takes place by highlighting two variables: the start and the length of stock markets' responses. [less ▲]

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See detailẾtude de l’émergence des organisations pastorales et de leur rôle dans les processus de gestion partagée de la vallée de la Tarka dans les départements de Bermo et Dakoro (Centre sud du Niger)
Ibrahim, Habibou ULg

Doctoral thesis (2016)

Cette thèse vise à analyser les organisations pastorales et leurs rôles dans la gestion des conflits fonciers. En Afrique subsaharienne et particulièrement au Niger, le foncier est au centre des enjeux de ... [more ▼]

Cette thèse vise à analyser les organisations pastorales et leurs rôles dans la gestion des conflits fonciers. En Afrique subsaharienne et particulièrement au Niger, le foncier est au centre des enjeux de l’agro-pastoralisme. La sécurisation des droits d’accès aux ressources et des systèmes de tenure foncière sont essentiels pour la gestion et la résolution des conflits fonciers (Herrea et al., 2007). La région de Maradi constitue la zone de contact entre le Nord pastoral et le Sud agricole. Dans cette partie centrale où la pression foncière, aggravée par la croissance démographique, se pose avec acuité, le spectre des conflits fonciers est malheureusement devenu un phénomène chronique, une donnée permanente (GADO., 2000). La pluralité des normes et plusieurs sources de droit contribuent à complexifier le règlement des litiges fonciers entre acteurs dans les départements de Dakoro et Guidan Roumdji (Moutari., 2001). Or la dynamique globale des systèmes d’élevage est déterminée par la complémentarité des espaces agro-pastoraux. Cette complémentarité est remise en cause par ces pressions foncières et suscite des changements organisationnels dans les communautés du centre Sud du Niger (Yamba., 2004 ; 2000). C’est le rôle des associations pastorales à Dakoro et Bermo qui est l’objet de cette recherche. En effet les organisations paysannes en Afrique Subsaharienne et au Niger en particulier jouent un rôle important dans la définition des politiques agricoles et deviennent des conditions indiscutables de la réussite des actions à promouvoir à l’échelle locale (Courade et Deveze., 2006 ; Mercoiret, 2006 ; Mercoiret et al. 2004). La méthodologie de travail relève de l’approche ethnographique. Les outils et instruments d’enquête sont les questionnaires et les entretiens ouverts avec les acteurs locaux sur les dynamiques territoriales, les modes d’action des associations pastorales et les conflits fonciers. Les résultats viennent aussi des travaux et des documents des projets, des ONG et des rapports des services techniques de l’Etat. Pour un souci de fiabilité des données, nous avons tenu à réaliser des séances de restitution des données et de triangulations pour confronter les informations de diverses sources. Au total 104 personnes sont enquêtées dont 30 % auprès des associations. Ces investigations ont concerné aussi les secrétaires des commissions foncières, les préfets, les agents des projets et des ONG et le président du tribunal de Dakoro ainsi que les leaders pastoraux, les transhumants, les agriculteurs et associations pastorales. [less ▲]

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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See detailLaser cooling of iron atoms
Huet, Nicolas ULg

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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See detailPrincipal static wind loads within a rigorous methodology to the envelope reconstruction problem
Blaise, Nicolas ULg

Doctoral thesis (2015)

Static wind loads are being used for the design of large civil structures such as high-rise buildings, large roofs and long-span bridges. Once static wind loads are known, they are used through the ... [more ▼]

Static wind loads are being used for the design of large civil structures such as high-rise buildings, large roofs and long-span bridges. Once static wind loads are known, they are used through the iterative design process without repeating cumbersome dynamical analyses. In this framework, structural engineers can effectively focus on the structural sizing since static analyses are straightforward. No codified wind loads, however, exist for those large structures with unique shapes and there is no consensual view on how to formally derived them. For each new major project, the challenge consists therefore in deriving a relevant set of static wind loads. Obviously, these loads must provide the actual envelope values of structural responses of interest. This states the objective of the envelope reconstruction problem and constitutes the core of this thesis. The proposed developments to solve this problem are relevant for structures responding with a linear dynamic behavior to the buffeting action of synoptic winds in a stationary framework. The pioneering concept of Equivalent Static Wind Load is normally considered for the design. An extensive review points out two main limitations of the current formulations. They have been originally established in a Gaussian context, are associated with either a nodal or nodal-modal basis and do not have a formal definition. The proposed Conditional Expected Load method overcomes the three drawbacks by defining a Conditional Expected Static Wind Load. This novel approach presents a general rigorous formulation for linear structural behavior, irrespective of the basis used for the analysis and relevant in a non-Gaussian context. The method is particularized for a certain class of non-Gaussian processes through a bicubic translation model. This model covers a large range of non-Gaussianity in the random processes and therefore paves the way for the formal establishment of “non-Gaussian” static wind loads. Other kinds of static loads such as the covariance proper transformation loading modes and the modal inertial loads are additionally studied. Unfortunately, both sets of loads are simply relevant for two limit structural behaviors, quasi-static and resonant, respectively. Moreover, they do not adapt to the set of structural responses of interest. From both points of view, one key result from our study is the innovative concept of Principal Static Wind Load as a sound solution for the envelope reconstruction problem. The concept relies upon a robust mathematical foundation. These loads are determined by the singular value decomposition of a large set of equivalent static wind loads. This decomposition can be seen as a way to rank the most relevant load patterns for the envelope reconstruction problem. The principal static wind loads have also the added distinctive advantage to be flexible. They are, indeed, able to naturally adapt to the set of structural responses of interest. Finally, a complete methodology to solve the envelope reconstruction problem irrespective of the structure, its load-bearing system and its susceptibility to vibrations in a Gaussian or non-Gaussian context is rigorously conceptualized. The intrinsic controllability of a set of pertinent parameters provides a smart balance between over and underestimation of the actual envelope. Moreover, combinations of static wind loads are computed to speed-up the reconstruction of the envelope values. The problem of determining these combination coefficients is formulated as a constrained nonlinear optimization. Equivalent and principal static wind loads, covariance proper transformation loading modes and modal inertial loads are implemented within the proposed methodology. Three examples: a four-span bridge, a real-life large stadium roof and a low-rise building demonstrate that the envelope reconstruction accuracy is considerably improved with principal static wind loads and with combinations thereof. [less ▲]

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

Doctoral thesis (2015)

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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