References of "Dissertations and theses"
     in
Bookmark and Share    
See detailSois belle et tais-toi: la bienveillance sexiste comme outil de discrimination
Sarlet, Marie ULg

Doctoral thesis (2012)

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

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

Detailed reference viewed: 47 (7 ULg)
Full Text
See detailNumerical simulations of brittle and elasto-plastic fracture for thin structures subjected to dynamic loadings
Becker, Gauthier ULg

Doctoral thesis (2012)

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

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

Detailed reference viewed: 219 (54 ULg)
Full Text
See detailModélisation des tensions circonférentielles en simulation méridienne d'écoulements en turbomachines
Thomas, Jean-Philippe ULg

Doctoral thesis (2012)

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

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

Detailed reference viewed: 55 (5 ULg)
Full Text
See detailEtude de la glycoprotéine L de l'herpèsvirus bovin 4 et de sa protection vis-à-vis des anticorps neutralisants
Lété, Céline ULg

Doctoral thesis (2012)

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

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

Detailed reference viewed: 76 (17 ULg)
Full Text
See detail« Abandonner le contrôle sans perdre le contrôle ». Une investigation du rôle de la confiance des subordonnés envers leur manager comme levier potentiel du contrôle organisationnel
De Zanet, Fabrice ULg

Doctoral thesis (2012)

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

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

Detailed reference viewed: 102 (22 ULg)
Full Text
See detailA Tool for Design Decision Making Zero Energy Residential Buildings in Hot Humid Climates
Attia, Shady ULg

Doctoral thesis (2012)

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

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

Detailed reference viewed: 503 (2 ULg)
Full Text
See detailExperimental Investigation of the Aerodynamics and Aeroelasticity of Flapping, Plunging and Pitching Wings
Norizham, Abdul Razak ULg

Doctoral thesis (2012)

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

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

Detailed reference viewed: 73 (8 ULg)
Full Text
See detailCorpus et catégorisation. Perspective linguistique sur les genres en néo-égyptien
Gohy, Stéphanie ULg

Doctoral thesis (2012)

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

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

Detailed reference viewed: 155 (16 ULg)
Full Text
See detailPrévisions des rendements du blé d’hiver à échelle régionale par modélisation de la courbe de chute de l’indice foliaire
Kouadio, Amani Louis ULg

Doctoral thesis (2012)

Estimation of cereal-crop production is considered as a priority in most crop research programs due to the relevance of food grain to world agricultural production. A large number of agrometeorological ... [more ▼]

Estimation of cereal-crop production is considered as a priority in most crop research programs due to the relevance of food grain to world agricultural production. A large number of agrometeorological models for crop yield assessment are available with various levels of complexity and empiricism. The current development of models for wheat yield forecasts, however, does not always reflect the inclusion of the loss of valuable green area and its relation to biotic and abiotic processes in production situation. At the field level, the close correlation between green leaf area during maturation and grain yield in wheat revealed that the onset and rate of senescence appeared to be important factors for determining wheat grain yield. Earth observation data, owing to their synoptic, timely and repetitive coverage, have been recognized as a valuable tool for crop monitoring at different levels. Our study sought to explore an approach for winter wheat (Triticum aestivum L.) yield forecasts at a regional scale, based on metrics derived from the senescence phase of the green area index (GAI). The senescence phase of winter wheat was analyzed and its modelling was achieved through two curve-fitting functions (modified Gompertz and logistic function). Metrics derived from these functions and characterizing this phase (i.e. the maximum value of GAI, the senescence rate and the time taken to reach either 37% or 50% of the remaining green surface in the senescent phase) were related to grain yields. The Senescence-based Approach For Yield estimates (SenAFY) was established and first tested at plot scale based on GAI values derived from digital hemispherical photograph. Then, it was applied at a regional scale using GAI temporal profiles retrieved from MODIS data. This second part of our study took advantage of recent methodological improvements in which imagery with high revisit frequency but coarse spatial resolution can be exploited to derive crop-specific GAI time series by selecting pixels whose ground-projected instantaneous field of view is dominated by the winter wheat. The regression-based models derived from the SenAFY provide interesting yield estimates at these two spatial scales. At regional scale, especially, the use of the SenAFY in order to forecast wheat yield gave satisfactory results. Such an approach may be considered as a first yield estimate that could be performed in order to provide better integrated yield assessments in operational systems. [less ▲]

Detailed reference viewed: 119 (26 ULg)
Full Text
See detailConception et réalisation d'un photobioréacteur adapté à l'étude de la production d'hydrogène chez les micro-algues. Application à l'étude de l'influence d'une NAD(P)H déshydrogénase-plastoquinone-réductase chloroplastique de type II sur le potentiel de photoproduction d'hydrogène chez Chlamydomonas reinhardtii.
Mignolet, Emmanuel ULg

Doctoral thesis (2012)

Conception and building of a photobioreactor adapted to the study of the production of hydrogen in microalgae. Application to the study of the influence of a Type II NAD(P)H dehydrogenase plastoquinone ... [more ▼]

Conception and building of a photobioreactor adapted to the study of the production of hydrogen in microalgae. Application to the study of the influence of a Type II NAD(P)H dehydrogenase plastoquinone reduction chloroplast on the potential of hydrogen photo-production in Chlamydomonas reinhardtii. Context and abstract of the thesis This project is part of a research framework to better understand the process of hydrogen photobioproduction in microalgae. Overall, we can say that hydrogen photobioproduction depends on the set of biochemical reactions that define cellular energy metabolism. In Chlamydomonas, H2 photobioproduction is ensured by two enzymes (Hyda1 and Hyda2). These two enzymes are located in the chloroplast stroma, they catalyze the reaction of hydrogen production (Fig. 1). The electrons required for the synthesis of H2 come from two different metabolic pathways, situated upstream of the PSI and CytB6f. The transport of electrons between these two paths and the CyB6f is via the plastoquinones (PQ) pool. The first pathway for the reduction of PQ involves the photolysis of water via photosystem II, known as the PSII-dependent pathway. The second reduction pathway is thought to involve an enzyme catalyzing the oxidation of NAD(P)H, and the reduction of PQ. Thought to be located on the stroma side of the membrane, it is known as the PSII-independent pathway. Succinctly, the PSII-dependent pathway could be considered as a contribution to the reductant supply from light energy and the PSII-independent pathway as a contribution to the reductant supply from starch, or more generally, from cellular carbon substrates. The existing situation: the NAD(P H-type II (Ndh-II) are enzymes capable of oxidizing NAD (P) H and transferring electrons to a quinone molecule (plastoquinone or ubiquinone). They are known as type II by analogy with mitochondrial complex I. As regards the chain of mitochondrial electron transport, NDH-II proteins constitute an alternative pathway to complex I and II to bring electrons to the ubiquinone pool. This alternative pathway would enable an adaptation to the yield of the electron transport chain based on the metabolic state of the algae. As regards the chloroplast electron transport chain, Ndh-II proteins are thought to participate in several mechanisms of adaptation to light intensity variations. Their function would be for the non-photochemical reduction of the PQ pool. In 2005, seven ''open reading frames'' corresponding to hypothetical type II NAD(P)H dehydrogenase (NDA1 to NDA2) were identified in the nuclear genome of Chlamydomonas. A study of Chlamydomonas NDA gene expression highlighted the most important expression of the NDA2 gene. In order to specifically study the role of the NDA2 enzyme, it was inactivated by RNA-interference. (Fred Jans thesis 2011). From the wt84 strain (Chlamydomonas reinhardtii), two lines of mutant deficient Nda2 were obtained: G4: Nda2-RNAi (1) P11: Nda2-RNAi (2) If we consider these lines from a phenotypic point of view, two main theoretical hypotheses can be made: is there a significantly decreased reduction of the PQ pool by the PSII-independent pathway? is there an affected, reduced or even completely inhibited hydrogen photobioproduction? In order to study the effect of the deficiency of the enzyme (Nda2) on the potential for hydrogen production, a set of tools and specific experimental protocols had to be developed to meet the second hypothesis (above). The aim of this project was mainly be to develop the study of modifications in hydrogen production. Purpose and specificity of the thesis: The purpose and specificity of this project was to break away from complex technical difficulties: knowing that the two mutant lines of Chlamydomonas reinhardtii were wall-less cells and therefore, highly sensitive to hydrodynamic stress; knowing that the study of hydrogen photobioproduction by microalgae was based on the capacity of degassing the culture medium, i.e. the need to obtain optimal hydrodynamic agitation favoring gas exchange. The main challenge was therefore to develop a system to find a consensus technique in order to resolve the contradiction between preserving the fragile algae while causing sufficient hydrodynamic agitation to degas the culture medium. In 2005, experimental tools for the study of hydrogen production by microalgae were poorly developed. The majority of H2 photoproduction experiments were conducted in glass bottles according to the Melis protocol. The Melis protocol is based on a temporal separation of two phases: the first is a phase of growth of microalgae in a culture medium that is optimal for photosynthesis and the accumulation of reserves (starch); the second phase begins after the transfer of the microalgae into a sulfur depleted medium. This procedure consists of causing biochemical stress, inducing reorganization and metabolic adaptation which will eventually lead to hydrogen photobioproduction. Although it is sufficient for a basic approach, the experimental procedure of bottle culture has several major drawbacks when it comes to studying the processes of hydrogen production over long periods (100 to 200 hours). In the bottles, the homogenization of the culture medium is conducted using magnetic stirrers moved by rotary shakers. To obtain good homogenization, a minimum speed of agitation is necessary. This process induces a relatively large hydrodynamic stress, resulting in significant cell death. On the other hand, microscope observation of Chlamydomonas cells grown in sulfur depleted medium deficient shows that the majority of algae lose their flagella and thus their natural mobility. This phenomenon reinforces the idea that magnetic stirrers severely limit the quality of experimental results: the agitation necessary for good homogenization must be more vigorous in sulfur depleted medium than in an optimal medium. Another major problem encountered in experiments using bottles is the quality of degassing. Generally, the analysis of gas products is done by gas chromatography; samples are taken in the gas phase, and then analysed. This method is unsuitable for this type of experiment. Is the gas phase in equilibrium with the liquid phase? Is there a risk of over or under-saturation of hydrogen? Is there an influence from pressure? Is there a risk of inhibiting the production of hydrogen by its own concentration in the medium? Does periodic and repeated sampling induce disturbances in how the reaction takes place? In order to solve these uncertainties and technical difficulties, a new and original concept of algal culture has been developed. The basic principle of this system involves placing a suspension of algae (culture medium) in a photobioreactor made of two transparent tubes connected at their ends. The photobioreactor is fixed on an oscillating table. A glass ball placed in one of the tubes slides because of the force of gravity, and this enables the homogenization of the medium. In addition to obtaining optimal homogenization without hydrodynamic stress (by three different types of mixing), a geometric feature of the whole has enabled active degassing of the hydrogen produced in the culture medium. Parallel and in annex to this photobioreactor (PBR), a system enabling the measurement and analysis in real time of the concentration of hydrogen in the gas phase has been developed. This system is based on the principle of polarographic analysis of oxygen concentration developed by Leland C. Clark. The O2 and H2 concentrations can be measured by a periodic reversal of the voltage across the electrodes. Finally, a theoretical model of evolution and equilibrium of hydrogen concentration in the PBR has been developed to monitor and compare the experimental results. The findings: The new concept of microalgae culture developed in this project has solved several problems. The homogenization of the culture medium by mixing the phases and stirring with a glass ball is a particularly effective alternative compared to mixing with the magnetic stirrers commonly used in bottles. Cell death by hydrodynamic stress can be reduced to virtually zero, whereas experience has shown that in this field, mixing using magnetic stirrers is a relatively harmful process. The original system of mixed phases with active degassing (at atmospheric pressure) has resulted in superior yields of hydrogen being produced than in other systems. The real-time analysis of changes in concentrations of oxygen and hydrogen via the probes has increased the accuracy of the results. It was observed that the variation of several experimental factors could lead to significant distortions between the theoretical model of evolution of the concentration of hydrogen (depending on the gas collected in the gasometer) and the measurements made using gaseous chromatography (GC). Those factors are the following: the quantity of culture medium in the reactor; he geometry of the interface between gas phase and liquid phase; he speeds of the mixing cycles; the pressure of the PBR; dynamic permeability and porosity; changes in production rates of hydrogen in different strains of microalgae. Because of these factors, changes in the experimental protocol were required: fixing an interval of time (within each experiment) to obtain the speed ​​of stable production; a study on the influence of pH, which helped validate the experimental range usually used; a study on the influence of hydrogen concentration on the rate of production. These changes have not only increased measurement accuracy, but have also confirmed certain hypotheses concerning a probable inhibition of hydrogen production by its own concentration in the culture medium. Confirmation of the inhibition of hydrogen production by its own concentration in the culture medium is undoubtedly the most important piece of information provided by the latter optimization of the protocol. Parallel to this, the observation of significant discrepancies between the theoretical model of the evolution of hydrogen concentration (depending on the gas collected in the gasometer) and the measurements made by gas chromatography (GC), result in the latter (GC) seeming to be unreliable in this type of experiment. The contribution of hydrogen / oxygen probes in the field of hydrogen photobioproduction by microalgae Developing of the system of measuring O2/H2 probes by time multiplexing (periodic alternation of the polarity probe) has provided new insights into the possibilities of monitoring the evolution of hydrogen concentration in real time. Although these probes were made by hand and used without the real purpose of gaining precise quantification, their potential in this area of ​​research is clearly visible. It is obvious that developing a similar system, but more accurate in terms of electrode geometry, would allow the calibration and enhancement of measurements (from a quantitative point of view). Besides this, an optimization of surface characteristics of the electrodes would also improve performance and increase capacity of use. A perfectly sealed probe head could work in the liquid medium and directly provide the values ​​of hydrogen concentration in the liquid phase. It is likely that this method of measuring hydrogen concentration by polarography, may in future replace the current method of gas chromatography. Taking all these elements into account: In the semi-closed PBR, the main problem for obtaining the values ​​of metabolic fluxes to study is keeping the characteristics of the gas exchange in well-defined operating range (pressure, H2 concentration and mixing dynamics). It is demonstrated in this paper that this procedure is relatively easy to carry out: the only constraint is to precisely define the characteristics of the PBR and the theoretical models. In the second part of the project, the photobioreactor is used to develop and complete a protocol analysis to characterize the relative contributions of the two metabolic pathways involved in hydrogen photobioproduction (the chloroplast electron transport chain) in the microalgae Chlamydomonas reinhardtii. Two publications have been written regarding the biochemical approach of the second part; interested readers can find there all the results and comments that this project has brought to the field. Follow-up to, and the future of, this project: Thanks to the PBR and its multi-adaptability, an original approach to the theoretical modeling of the metabolism of hydrogen production is possible if the following are known: the various flux values ​​of the metabolic pathways; the volumes of hydrogen produced; production rates based on metabolic configurations; the speed and quantity of starch consumed; the speeds of mitochondrial respiration and their involvement in hydrogen production (via PEDO2). By standardizing and unifying the various units of measurement used to characterize the flow and the amounts of material as well as the electrochemical potentials and the gradients, through which the matter passes, it should be possible to construct a matrix model according to Kirchhoff's laws. From this model, it should be possible to deduce other values and other metabolic constants without having to necessarily pass through experimentation. This model would also, by successive iterative approaches and extrapolation, determine new optimal operating ranges for the PBR. [less ▲]

Detailed reference viewed: 109 (12 ULg)
Full Text
See detailLithostratigraphie, sédimentologie et analyse séquentielle du Quartzite de Berlé (Emsien supérieur, Grand-Duché de Luxembourg)
Michel, Jonathan ULg

Doctoral thesis (2012)

The Lower Devonian is a period of interest because it is characterized by the first transgression of the Rheic Ocean, after the Caledonian orogeny, over the coasts of the Old Red Sandstones Continent. In ... [more ▼]

The Lower Devonian is a period of interest because it is characterized by the first transgression of the Rheic Ocean, after the Caledonian orogeny, over the coasts of the Old Red Sandstones Continent. In the Ardenne Basin, during this transgression, widespread siliciclastic deposits were deposited. From the Lochkovian to the Upper Emsian, the basin underwent various stages of development. The main object of this PhD thesis was to focus on one of these episodes recorded in the Neufchâteau-Wiltz-Eifel Basin. This work is the result of the integration of different techniques, such as field work, microscopic analyses, biostratigraphy, sequence stratigraphy, magnetic susceptibility and diagenesis. The analysis of the microfossil content of four sections in Luxembourg led to the identification of 23 species of spores and 11 species of acritarchs. Biostratigraphically, these spores confirmed the Emsian age of the different lithological units (“Couches de Clervaux”, “Quartzite de Berlé” and “Schistes de Wiltz”). The sedimentological analysis of the Neufchâteau-Wiltz-Eifel Basin is based on the study of more than 600 thin sections from 11 sections covering the entire basin. This study allowed to identify an estuary setting divided into three types of environments: an alluvial, a tidal and finally a marine distal environment. Detailed sedimentology associated with sequence stratigraphy of the whole Neufchâteau-Wiltz-Eifel Basin allowed to propose a vertical and lateral succession model of this estuarine setting. In this model, the “Quartzite de Berlé” corresponds to tidal sand ridges and changes laterally to the flaser bedded sandstones of the top of the “Couches de Clervaux”. This lateral facies transition tends to proof that the “Quartzite de Berlé” is a lenticular deposit. The “Quartzite de Berlé” is a prominent feature in the landscapes and a very resistant rock appreciated as a building material. Diagenesis study allows a better understanding of the mechanisms responsible for these characteristics, trough the identification of different cements and authigenic minerals. Temporal relationships between these different components are integrated in a paragenetic modelisation that includes four distinct phases: an eogenetic, a mesogenetic, a metamorphic and a telogenetic phase. The clay mineralogy (illite cristallinity) shows that the “Quartzite de Berlé” underwent variable conditions of burial, depending of the area considered. Our results point out that this variability is related to the pre-orogenetic rifting stage of the Rhenohercynian Basin. Finally, the use of magnetic susceptibility, suggested that in proximal setting, the magnetic susceptibility signal is mainly controlled by environmental parameters (water agitation, sedimentation rates) and diagenesis. [less ▲]

Detailed reference viewed: 123 (18 ULg)
Full Text
See detailIntegration of farmers in the shrimp subsector in the Mekong River Delta, Vietnam
Ho, Thi Minh Hop ULg

Doctoral thesis (2012)

Hatcheries, input dealers, farmers, collectors and processors are the primary actors of shrimp value chain in the Mekong River Delta (MRD) Vietnam, a sector that has many problems of disease, shrimp seed ... [more ▼]

Hatcheries, input dealers, farmers, collectors and processors are the primary actors of shrimp value chain in the Mekong River Delta (MRD) Vietnam, a sector that has many problems of disease, shrimp seed, environmental pollution, and management skills. Holding the strongest power in the shrimp value chain, the processors determine shrimp prices and set up requirements of shrimp quality and size in the market though quality control has not been completely implemented due to the limitations of financial capital, knowledge, awareness, as well as the quality of raw material supplied by collectors and farmers. Farmers stayed in the weakest position in the chain due to their small individual scale, and low skills. The results of the study show that most of the shrimp farmers stay out of vertical integration under farming contracts while the rest joined in the game without success. Contract farming seems not for small scale farmers who account for a large part in the MRD, and not interesting for producers who get success with their cultivation. Farmers prefer a non-contract option due to non-transparency of interest share as well as cost account. Food safety standards, decision No. 80/2002/QĐ-TTg, culture, trust, government structure, credit support and corruption are the main factors affecting farmers’ integration chances. Floor price mechanism, risk sharing, small scale of the model of vertical integration and excess suppliers in the market, administrative misconception and inefficient public management are the main reasons of failures of contract farming of two case studies in the MRD. Planning and projection of shrimp production zones are therefore the priority matters to address. Furthermore, re-organizing shrimp farmers into legal teams or groups or cooperatives is also necessary to increase the size of the existing shrimp cultivation units in Vietnam in order to improve the sector. [less ▲]

Detailed reference viewed: 90 (11 ULg)
Full Text
See detailGeophysical identification, characterization, and monitoring of preferential groundwater flow paths in fractured media
Robert, Tanguy ULg

Doctoral thesis (2012)

This thesis investigates fractured zones leading to preferential groundwater flow paths. In this context, we used the electrical resistivity tomography (ERT) and the self-potential (SP) methods to ... [more ▼]

This thesis investigates fractured zones leading to preferential groundwater flow paths. In this context, we used the electrical resistivity tomography (ERT) and the self-potential (SP) methods to identify, characterize, monitor, and finally model preferential flow in hydraulically-active fractured zones at a scale representative of real world applications. From an experimental point of view, we first identified the magnitude of self-potential signature, a -15 mV anomaly that could be associated with preferential groundwater flow in a shallow quartzite aquitard whereas the streaming potential theory was originally developed for porous media. This signature was confirmed experimentally in limestone aquifers at greater depths. The joint use of surface ERT and SP allowed the identification of water-bearing fractured areas which were electrically more conductive, presenting contrasts from 1 to 10 and which were hydraulically-active presenting negative SP anomalies ranging from -10 to -30 mV. We were also able to correlate hydraulic heads and SP gradients during a low and a high groundwater level period leading to interesting perspectives in understanding the dynamics of complex groundwater flow systems. Finally, a preferential flow and rapid transport path, over 10 m/h, was highlighted in a 20 m deep fractured and karstified limestone valley by monitoring a salt tracer test with only surface ERT. This methodology was being mostly used for relatively shallow and homogeneous aquifers up to now. Such information is crucial to set up new monitoring wells or to define the sampling rates of classic tracer test. From a methodological point of view, we quantitatively assessed the efficiency of blocky and minimum-gradient-support regularizations in electrical imaging to recover sharp interfaces on numerical benchmarks and with field data. The usefulness of resolution indicators such as the cumulative sensitivity matrix and the resolution matrix were also assessed in this context. We demonstrated that noise characterization is crucial in time-lapse inversion and may supplant the choice of the time-lapse inversion scheme, calling for a systematic analysis of reciprocal measurements (or a subset of them). We also showed that, when using data differences in an inversion scheme, the data error, as estimated by time-lapse reciprocal measurements, depends on the mean measured resistance. These error characterization studies should always be performed if one wants to avoid wrong interpretations about the hydrodynamics. We further showed that focused inversion techniques (blocky inversion, minimum-gradient-support) may offer great perspectives when recovering model changes in time-lapse inversion. Finally, ERT and SP were jointly used to conceptualize a physically-based and spatially distributed hydrogeological model, in particular to characterize the preferential flow paths. Predicted hydraulic heads and SP-derived hydraulic heads using the water table model showed a clear correlation, leading to perspectives in terms of hydrogeological model calibration. Further experiments are however needed to fully estimate the streaming potential apparent coupling coefficient, but the use of the full SP signals for hydrogeological model calibration is a clear perspective to this work. [less ▲]

Detailed reference viewed: 125 (39 ULg)
See detailEtudes des systèmes de défenses antitoxiques chez l’amphipode Gammarus roeseli : Effets du parasitisme et d’une exposition au cadmium.
Gismondi, Eric ULg

Doctoral thesis (2012)

Pour faire face à des perturbations environnementales, les organismes ont développé des défenses antitoxiques couramment utilisés comme biomarqueurs dans l’évaluation de la qualité des milieux. Cependant ... [more ▼]

Pour faire face à des perturbations environnementales, les organismes ont développé des défenses antitoxiques couramment utilisés comme biomarqueurs dans l’évaluation de la qualité des milieux. Cependant, de nombreux facteurs confondants comme la température ou le genre, influencent la réponse de ces biomarqueurs. Il est ainsi nécessaire de connaitre les effets de ces facteurs afin d’imputer correctement la réponse biologique mesurée à la présence de polluants. Dans ce contexte, nous avons choisi d’étudier l’influence d’un parasite acanthocéphale, Polymorphus minutus, transmis horizontalement et de microsporidies à transmission verticale, sur les réponses physiologiques de leur hôte, Gammarus roeseli, un crustacé amphipode d’eau douce d’intérêt écotoxicologique. Pour cela, nous avons choisi d’étudier le glutathion, tripeptide jouant un rôle central dans les systèmes antitoxiques, sa synthèse (i.e. activité γ-glutamylcystéine ligase), les réserves énergétiques (i.e. lipides, glycogène, protéines) et un biomarqueur d’effets toxiques, le malondialdéhyde. L’influence du parasitisme a été appréhendé dans différents cas d’études: (i) chez G. roeseli infecté par P. minutus, (ii) chez G. roeseli infecté par des microsporidies (Dictyocoela roeselum essentiellement) et (iii) chez G. roeseli co-infecté par ces deux types de parasite. Chaque cas d’étude a été réalisé en absence de stress et lors d’une exposition au cadmium. Nous avons mis en évidence qu’en absence de contamination, la présence de P. minutus et une co-infection par P. minutus et D. roeselum affectent les biomarqueurs de G. roeseli. Après exposition au cadmium, la présence de parasites (i.e. infection simple ou co-infection) modifie la mobilisation des défenses antitoxiques et accentue les effets toxiques subits par l’hôte. Les résultats obtenus au cours de ce travail mettent en avant le caractère confondant du parasitisme en écotoxicologie et souligne l’importance de prendre en compte ce paramètre lors de l’évaluation de la qualité des milieux. [less ▲]

Detailed reference viewed: 7 (0 ULg)
Full Text
See detailStudy of the portals of entry of Cyprinid herpesvirus 3 in Cyprinus carpio
Fournier, Guillaume ULg

Doctoral thesis (2012)

The common carp is one of the most important freshwater species in aquaculture and its colourful subspecies koi is grown for personal pleasure and exhibitions. Both subspecies are economically important ... [more ▼]

The common carp is one of the most important freshwater species in aquaculture and its colourful subspecies koi is grown for personal pleasure and exhibitions. Both subspecies are economically important. In the 1990s, a highly contagious and lethal pathogen called koi herpesvirus (KHV) or cyprinid herpesvirus 3 (CyHV-3) began to cause 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 applied and fundamental research. The goal of this thesis was to identify the portals of entry of CyHV-3 in carp. This information is essential to understand the pathogenesis and the epidemiology of the infection, but also to develop efficacious vaccines. Prolonged CyHV-3 cultivation in vitro leads to the spontaneous attenuation of the virus. To circumvent this problem, the entire viral genome was cloned as a bacterial artificial chromosome (BAC). Then to test the usefulness of the BAC clone, several recombinants strains were generated as described in the first chapter. In the second chapter, we took profit of the CyHV-3 BAC clone to produce a recombinant strain encoding a firefly luciferase (LUC) expression cassette. Infection of carp by immersion in water containing the CyHV-3 LUC strain demonstrated, using bioluminescent in vivo imaging system (IVIS), that the skin, and not the gills, is the major portal of entry for CyHV-3. Fish skin provides mechanical, chemical and immune protection against injury and pathogenic microorganisms. Its mucus layer confers an innate immune protection against pathogen entry. However, there is little in vivo evidence on the role of skin mucus as a first line of innate immune protection against bacterial and viral infections. In the third chapter, we used the CyHV-3 LUC strain and IVIS to investigate the roles of epidermal mucus as an innate immune barrier against CyHV-3 entry. Our results demonstrate that the mucus of the skin inhibits CyHV-3 binding to epidermal cells and contains soluble molecules able to neutralize CyHV-3 infectivity. The skin is the major portal of entry after inoculation by immersion in water containing CyHV-3. While this model of infection mimics some natural conditions in which infection takes place, other epidemiological conditions could favor entry of virus through the digestive tract. Consequently, in the fourth and last chapter, we investigated the role of the carp digestive tract as a viral portal of entry using bioluminescence imaging. We found that feeding carp with infectious materials induces CyHV-3 entry through infection of the pharyngeal periodontal mucosa. In conclusion, this study demonstrated that according to epidemiological conditions, CyHV-3 can enter carp either through infection of the skin (immersion in infectious water) or through infection of the pharyngeal periodontal mucosa (feeding on infectious materials). The existence of these two portal of entry adapted to different epidemiological conditions most probably contributes to the high contagious nature of the virus. [less ▲]

Detailed reference viewed: 78 (10 ULg)
Full Text
See detailL’action publique de lutte contre le travail des enfants au Burkina Faso : politiques, acteurs, dynamique d’actions et controverses
Wouango, Joséphine ULg

Doctoral thesis (2012)

La thèse analyse les politiques et les interventions en matière de protection de l'enfance au Burkina Faso. Les enseignements de cette recherche concernent sa dimension empirique d'une part et son objet ... [more ▼]

La thèse analyse les politiques et les interventions en matière de protection de l'enfance au Burkina Faso. Les enseignements de cette recherche concernent sa dimension empirique d'une part et son objet spécifique d'autre part. Cet objet n'est pas le travail des enfants comme tel, mais la construction d'une politique publique dans un pays qui reste massivement rural et largement dépendant de l'aide internationale. [less ▲]

Detailed reference viewed: 124 (29 ULg)
Full Text
See detailPoroelastic Center of Dilation Revisited
Huynen, Alexandre ULg

Master of advanced studies dissertation (2012)

In both elasticity and poroelasticity, the nucleus of strain is usually used to refer to a singular solution such as the point force, the force dipole, the centers of rotation and dilation, etc. These ... [more ▼]

In both elasticity and poroelasticity, the nucleus of strain is usually used to refer to a singular solution such as the point force, the force dipole, the centers of rotation and dilation, etc. These fundamentals solutions constitute the building blocks for various problems of practical importance and are, therefore, relatively well understood. However, a comparison of the original elastic solution for the center of dilation with the classic Lamé solution reveals an unexpected dependence of the center of dilation solution on the Poisson’s ratio. This inconsistency is investigated by means of two alternative representations of the singularity and leads to the identification of a compressed zone inside the singularity. The poroelastic equivalent to this nucleus of strain is shown to be the superposition of the elastic one with drained material parameters and an instantaneous point fluid source associated with a finite volume of fluid that is expelled from the compressed region inside the singularity and is injected in the porous medium. [less ▲]

Detailed reference viewed: 16 (4 ULg)
Full Text
See detailOrigine et effet de la myéloperoxydase lors de la congélation du sperme d'étalon
Ponthier, Jérôme ULg

Doctoral thesis (2012)

Semen freezing allows worldwide commercialization of equine genetic. Despite improvement of techniques, semen of 20% of stallions remains unfreezable. Currently, post-thaw semen quality is only determined ... [more ▼]

Semen freezing allows worldwide commercialization of equine genetic. Despite improvement of techniques, semen of 20% of stallions remains unfreezable. Currently, post-thaw semen quality is only determined by progressive motility, but its definition is not standardised. Spermatozoa are highly differentiated cells and freezing lesions can occur on DNA, membrane, mitochondria or acrosome. Current research focuses on prediction of freezability, improvement of freezing extenders and prevention of Reactive Oxygen Species (ROS) effects. Under its O2 form, oxygen is inactive and oxidase or oxygenase enzymes are required to produce ROS. Two pathways of ROS production in semen are described: the intrinsic pathway reflecting ROS escaping from the spermatozoon mitochondria and the extrinsic pathway corresponding to ROS produced by inflammatory cells. ROS induce DNA fragmentation, lipid peroxidation, apoptosis and decreased motility of spermatozoa. Myeloperoxidase (MPO) is a pro-oxidant enzyme contained in and released by neutrophils during degranulation or after lysis. It is responsible for formation of hypochlorous acid, a strong oxidant, which could damage spermatozoa. However, MPO presence and effects have never been investigated in equine semen. The first aim was to assay presence of MPO in equine thawed semen and to determine a relation between MPO concentration and post-thaw semen parameters. 35 straws from different stallions were analyzed. Post-thaw spermatozoa and MPO concentrations, viability, morphology, progressive and total motility were determined. Our study showed that thawed semen contains large amounts of free MPO. High MPO concentration samples showed lower total and progressive motility. Higher proportion of acrosome reaction was observed in late examinations of the high MPO concentration group. As MPO was present in frozen semen and did interfere with its quality, timing and origin of its release was determined during the freezing process. Forty ejaculates were frozen with a classical procedure. MPO ELISA and MPO immunocytochemistries (ICC) were assayed in raw semen, centrifugation supernatant, and after cooling down to 4°C. Post-thaw MPO concentration and spermogram parameters were determined. MPO concentration increased after cooling and thawing when compared to fresh semen. As temperature decreased, MPO was higher in post-thaw poor quality samples. Non-sperm cells (NSC) showed various degrees of MPO-ICC, and were mostly epithelial cells with nuclear picnosis. Elastase, another neutrophil pro-inflammatory enzyme, was also assayed in post-thaw semen. In twenty ejaculates, NSC concentration was determined in fresh semen. Post-thaw motilities were determined by CASA; MPO and elastase concentrations were assayed by ELISA. Post-thaw elastase concentrations were low and there was no difference according to semen quality. NSC or MPO concentrations were not correlated to elastase concentration. NSC concentration was higher in unfreezable semen and correlated to post-thaw MPO concentration. To confirm MPO release by NSC during freezing, the effect of washing semen with density gradient centrifugation (DGC) was then assayed on NSC and MPO concentrations. NSC and MPO concentrations were assessed at each step and MPO localization was performed by ICC. DGC washing decreased NSC and MPO concentrations in post-thaw semen and NSC were mainly remaining in DGC supernatant. MPO concentration was correlated with NSC concentration in the upper layer of the DGC supernatant and in post-thaw semen. NSC were epithelial cells showing MPO-ICC staining. Fresh semen MPO concentration had no effect on fresh or post-thaw semen quality, while post-thaw semen concentrations were correlated with decreased motility. To understand these findings, concentration, activity and structure of MPO present in seminal plasma, sperm-rich pellet and post-thaw semen were assayed. Factor inducing MPO release was determined by adding or not glycerol in samples stored at 4°C or 20°C. Total MPO was high in seminal plasma and thawed semen and low in sperm-rich pellet. Active MPO was high in sperm-rich pellet and low in seminal plasma and post-thaw semen. MPO concentrations were correlated in post-thaw and in semen cooled at 4°C with or without glycerol. Active MPO in sperm-rich pellet and post-thaw progressive motility were highly negatively correlated. MPO present in fresh semen is mainly the native inactive enzyme subunit. To confirm our previous findings, effect of active MPO and fresh or frozen-thawed NSC was assayed on purified spermatozoa motility, mitochondrial potential, membrane and acrosome integrity. Highest MPO concentration tested (50ng/ml) decreased motility. However, highest MPO concentration did not affect mitochondrial potential, membrane or acrosome integrity. Thawed NSC did decrease motility and mitochondrial potential when compared to fresh NSC, suggesting a synergic effect between MPO and other products released by NSC after thawing. Temperature decrease during freezing process increases MPO concentration and post-thaw concentration is negatively associated to post-thaw motilities. ICC slides have shown MPO presence on epithelial keratinized and pycnotic cells while neutrophils were rarely observed. Semen washing with DGC decreases MPO and NSC concentrations in post-thaw semen as NSC and MPO concentrations were positively correlated. MPO present in seminal plasma is native and inactive form while MPO present in sperm-rich pellet is active and negatively correlated to the post-thaw progressive motility. Addition of active MPO in semen decreased motility but had no effect on acrosome integrity, despite what had previously been suggested. Thawed NSC addition to spermatozoa decreased mitochondrial potential, suggesting a synergic effect between MPO and other factors released by NSC. Further studies should investigate the origin of high inactive MPO concentrations in fresh semen. Other studies should be conduced about the origin of epithelial keratinized pyknotic NSC in fresh semen and the pathophysiological mechanism leading to their MPO release during freezing. Large scale studies should be conducted to confirm the use of NSC concentration in fresh semen or active MPO concentration in sperm rich pellet as freezability prognosis. Further studies should also investigate effect of MPO specific inhibitors. [less ▲]

Detailed reference viewed: 129 (34 ULg)
Full Text
See detailL'identité à travers l'espace et le temps. Vers une définition de l’identité et des relations spatio-temporelles entre objets géographiques.
Hallot, Pierre ULg

Doctoral thesis (2012)

The principal goal of this research is to model object’s evolution in space and time; it implies questioning identity, space and time. First, we define the concept of object spatio-temporal state. This ... [more ▼]

The principal goal of this research is to model object’s evolution in space and time; it implies questioning identity, space and time. First, we define the concept of object spatio-temporal state. This concept allows modelling object identity evolution. Indeed, managing object identity must not be related to the object spatiality. In other words, we assume that the existence of an object is not dependant of its spatial extension. We show that there exist a lot of relationships associated to objects which does not yet exist or which does not exist anymore. We show also that when objects are not visible during an interval of time, it does not imply the lost of their identity. The model we propose aims at providing a framework for non-existent and non-visible objects Then, we study the spatio-temporal interactions between objects. The proposed solution is to define relationships between objects spatio-temporal states. It appears that the proposed set of relationships is a generalized vision of existing spatio-temporal reasoning models. Knowing that space-time continuity is not preserved in qualitative modelling, we apply the dominance theory which aims at retrieving continuous transitions between qualitative states. This development provides formal definitions of possible transition between spatio-temporal states relationships. Logically, the next step is to study the possible evolution of these spatio-temporal states relationships. This leads to the development of a formal model called “life and motion configurations”. This iconic representation gives a simplified view of the spatio-temporal evolution between two objects. It can be used to formalize the relationship between two spatio-temporal histories. In this work, we prove that this language is sufficient to provide spatio-temporal knowledge on moving objects. It determines also a framework in which others spatio-temporal reasoning models can be classified. Based on life and motion configurations, we propose two applications. Firstly, the life and motion configurations are generalised into a set of 25 relationships representing spatio-temporal information with a high level of abstraction. We believe that this set is close to people perception of spatio-temporal information. Secondly, two natural language interpretations of life and motion configurations are proposed; one applied to generalized spatio-temporal relationships, one applied to spatio-temporal predicates used in common French language. [less ▲]

Detailed reference viewed: 275 (46 ULg)
Full Text
See detailDéveloppement d'un photocatalyseur à base d'oxyde de titane pour l'élimination de polluants et de bactéries en milieu aqueux
Tasseroul, Ludivine ULg

Doctoral thesis (2012)

Dans le cadre de la réutilisation des eaux usées et de l’accès limité à l’eau potable dans certaines régions du globe, de nouvelles techniques d’épuration nécessitant de faibles consommations d’énergie ... [more ▼]

Dans le cadre de la réutilisation des eaux usées et de l’accès limité à l’eau potable dans certaines régions du globe, de nouvelles techniques d’épuration nécessitant de faibles consommations d’énergie sont étudiées. Parmi ces nouvelles techniques, la photocatalyse hétérogène utilise des réactions d’oxydation et de réduction pour la dégradation de polluants organiques et de micro-organismes. Le photocatalyseur le plus employé est le TiO2. Lorsqu’il est illuminé par un rayonnement UV, des paires électron/trou sont générées et réagissent avec l’eau et l’oxygène pour former des radicaux libres qui vont dégrader les polluants. Le procédé sol-gel permet de contrôler facilement la texture, la cristallinité, l’introduction de dopants et la mise en forme de matériaux. Il a été utilisé dans ce travail pour la synthèse de photocatalyseurs à base de TiO2, (xérogels). À partir de sols en cours de gélification, des films de TiO2 ont été déposés par spin-coating. Après calcination, ces films sont actifs pour la dégradation du bleu de méthylène sous UV-A. Afin d’améliorer l’activité photocatalytique de xérogels de TiO2, des particules d’argent ont été introduites dans la matrice par cogélification. Ces particules d’argent améliorent l’activité du TiO2 pour la dégradation du bleu de méthylène sous UV-A. En plus de l’amélioration de l’activité photocatalytique, l’extension de l’activation du TiO2 au domaine visible du spectre solaire a été étudiée par sensibilisation avec des porphyrines. Ces porphyrines sont introduites d’une part, par greffage sur le catalyseur Degussa P25 et d’autre part, in situ dans la matrice de xérogels de TiO2. Le greffage des porphyrines ne permet pas l’activation du catalyseur Degussa P25 sous lumière halogène. Par contre, l’introduction in situ des porphyrines permet l’activation du TiO2 avec des longueurs d’onde du domaine visible et améliore ainsi l’activité des xérogels sous lumière halogène pour la dégradation du p-nitrophénol. L’activité antibactérienne de plusieurs catalyseurs préparés au cours de la thèse a également été évaluée pour la dégradation de deux espèces de bactéries : Escherichia coli et Lactobacillus rhamnosus. Cette activité antibactérienne est corrélée à l’activité dépolluante des photocatalyseurs. L’étude cinétique de la dégradation du p-nitrophénol sur un xérogel de TiO2 dopé in situ avec une porphyrine a été réalisée. Cette étude montre que la dégradation implique un type de site actif correspondant aux trous h+ créés lorsque le TiO2 est exposé à la lumière. L’étape limitante correspond à la réaction de surface entre le p-nitrophénol adsorbé et les radicaux OH• adsorbés. Cette étude cinétique utilise une loi sigmoïdale plutôt que linéaire pour modéliser les courbes de dégradation du p-nitrophénol. [less ▲]

Detailed reference viewed: 80 (23 ULg)
Full Text
See detailCommercialisation des produits vivriers paysans dans le Bas-Congo (R. D. Congo) : contraintes et stratégies des acteurs
Mpanzu Balomba, Patience ULg

Doctoral thesis (2012)

The results of this study reveal that the marketing of the main food products of Bas-Congo (cassava, plantain, maize, bean and groundnut) faces many constraints. Indeed, the food markets of Bas-Congo are ... [more ▼]

The results of this study reveal that the marketing of the main food products of Bas-Congo (cassava, plantain, maize, bean and groundnut) faces many constraints. Indeed, the food markets of Bas-Congo are characterized by inadequate infrastructures (transport, storage and processing), no-standard sale units, problems of information on the market, an informal operation, a large number of intermediaries and harassment on the roads and the markets. In the countryside, the peasants walk an average of 8 km to sell their small crop surplus in the rural markets. Financial constraints often force the wholesalers to turn to certain actors of the sector to finance the payment of marketing costs by giving up to them, in return, the exclusive right to sell their food products. These constraints have as consequences particularly high costs of transaction at the level of wholesalers of which the most important is the transportation which represents 46 to 61% of the total of these costs, significant margins on wholesale (45 to 68% of the wholesale price), etc. The study shows also a lack of spatial integration between Kimpese (Bas-Congo) and Kinshasa markets. Food markets actors adapt themselves by developing strategies in order to mitigate the impacts of these constraints and to maintain both production and marketing activities. [less ▲]

Detailed reference viewed: 129 (53 ULg)
See detailOpening Participation through Participatory Technology Assessment: The Case of Nanotechnologies for Tomorrow's Society
Van Oudheusden, Michiel ULg

Doctoral thesis (2012)

This dissertation examines how participants in a Flemish participatory technology assessment (pTA) on nanotechnologies defined and negotiated the meaning of participation in (nano)science and technology ... [more ▼]

This dissertation examines how participants in a Flemish participatory technology assessment (pTA) on nanotechnologies defined and negotiated the meaning of participation in (nano)science and technology in the course of their engagements. It focuses explicitly on the initiating role that social scientists played in the project and how they performed participation. The dissertation proposes a critical reappraisal of the way in which participation in pTA is planned and implemented, which is explicitly political in character. [less ▲]

Detailed reference viewed: 24 (2 ULg)
Full Text
See detailBio-inspired polymers for the functionalization of industrial steel surfaces
Faure, Emilie ULg

Doctoral thesis (2012)

Detailed reference viewed: 29 (6 ULg)
Full Text
See detailElaboration d’un protocole in vitro de contournement des barrières d’incompatibilité génétique entre Phaseolus coccineus L. et P. vulgaris L.
Barikissou, Eugénie ULg

Doctoral thesis (2012)

L’amélioration du haricot commun Phaseolus vulgaris L. par hybridations interspécifiques avec P. coccineus L. nécessite l’utilisation de ce dernier comme parent femelle (♀). Mais ce croisement aboutit ... [more ▼]

L’amélioration du haricot commun Phaseolus vulgaris L. par hybridations interspécifiques avec P. coccineus L. nécessite l’utilisation de ce dernier comme parent femelle (♀). Mais ce croisement aboutit souvent à des avortements et ce, dès le stade globulaire. L’embryoculture permet d’obtenir, dans certains cas, des hybrides interspécifiques via la culture d’embryons isolés aux stades cordiforme âgé ou cotylédonaire, mais pas au stade globulaire. A ce dernier stade de développement, il a été possible d’obtenir des plantes chez le génotype NI 637 de P. vulgaris, via le protocole de culture de gousses. Mais l’absence de formation de racines chez les embryons germés, qui devraient évoluer en plantules, a limité le taux de réussite à un pourcentage de 3% de plantules en croissance. L’objectif de notre travail est d’améliorer ce taux afin de parvenir à sauver efficacement les embryons hybrides P. coccineus (♀) x P. vulgaris. Nous avons tout d’abord étudié les conditions de régénération in vitro des embryons obtenus par autofécondations, pour les appliquer ensuite aux embryons hybrides interspécifiques. Différents essais ont été réalisés sur base du protocole de culture de gousses. Ce protocole consiste à réaliser la culture de jeunes gousses successivement sur trois milieux à osmolarité décroissante et nommés : P00 (à 580 mosm), P01 (à 450 mosm) et P01 (à 350 mosm). Après une semaine de culture les embryons sont isolés des gousses puis transférés successivement sur les milieux G1 de maturation et germination, G6 de déshydratation, G7g d’induction de racines et G7c de développement en plantules. L’évaluation de ce protocole de culture de gousses chez trois génotypes : NI 637, NI 622 et X 484 de P. vulgaris et un génotype NI 16 de P. coccineus, nous a permis de confirmer les difficultés d’enracinement des embryons germés, comme rapportées auparavant chez NI 637. Toutefois, le retrait de la BAP (0,1 µM) du milieu G1 et la culture, au-dessus du milieu des embryons isolés, ont permis d’obtenir un taux de germination de 91%, c’est-à-dire un taux deux fois plus élevé par rapport au résultats rapportés antérieurement chez NI 637. La culture préalable des embryons en milieu G1 liquide a favorisé, après leur transfert successif sur les milieux gélosés G6, G7g et G7c, l’enracinement et le développement en plantules, en réduisant le brunissement du milieu et la formation de cals. Cela nous a permis d’obtenir un taux de 10% de plantules en croissance, taux trois fois plus élevé par rapport à celui rapporté auparavant en milieu gélosé. Toutes les plantules obtenues, par culture préalable en milieu liquide, ont développé des plantes adultes après un mois d’acclimatation. La culture des embryons en milieu gélosé et l’ajout du charbon actif dans les deux milieux G7g et G7c ont également permis de réduire le brunissement et la formation de cals. Cela a donné un taux de plantules en croissance de 60%, c’est-à-dire un taux 20 fois plus élevé par rapport à celui rapporté auparavant sans charbon actif. Le microbouturage de nœuds cotylédonaires, combiné au protocole de culture de gousses, a permis de régénérer des plantules chez tous les génotypes testés, avec un taux de régénération plus élevé chez NI 16 de P. coccineus (90%) par rapport à P. vulgaris (50%). Cela représente un taux de régénération trois fois plus élevé par rapport au résultat rapporté auparavant avec la culture de gousses seule chez le génotype NI 637 de P. vulgaris. La culture in vitro des embryons en cours d’avortement et isolés de l’ovule au stade cordiforme jeune, combinée au microbouturage de nœuds cotylédonaires, nous a permis d’obtenir, pour la première fois, une plantule hybride P. coccineus (NI 16) x P. vulgaris (NI 637). Notre protocole, qui combine le protocole de culture de gousses et le microbouturage de nœuds cotylédonaires, pourrait être une alternative intéressante pour le sauvetage d’embryons qui avortent au stade globulaire. [less ▲]

Detailed reference viewed: 70 (14 ULg)
Full Text
See detailDegradation mechanisms of Prussian blue pigments in paint layers
Samain, Louise ULg

Doctoral thesis (2012)

Prussian blue is a modern synthetic pigment discovered in Berlin at the beginning of the eighteenth century. Prussian blue is a hydrated iron(III) hexacyanoferrate(II) complex and its color results from ... [more ▼]

Prussian blue is a modern synthetic pigment discovered in Berlin at the beginning of the eighteenth century. Prussian blue is a hydrated iron(III) hexacyanoferrate(II) complex and its color results from an intervalence charge transfer between the iron(II) and iron(III) ions when light is absorbed at ca. 700 nm. Because of both its highly intense color and its low cost, Prussian blue enjoyed immediate popularity among artists and was widely used as a pigment in paintings until the 1970's. However, the permanence of Prussian blue had already been questioned by the mid-eighteenth century, because it exhibits a tendency to fade in light and to turn green. The preparative methods were rapidly recognized as a contributory factor in the fading of the pigment. The main objective of this thesis is the identification of the degradation mechanisms of Prussian blue pigments in paint layers. Prussian blue was synthesized according to both ancient and modern preparation methods. A thorough analysis of the pigments revealed a dependency upon the type of synthesis, the crystallite size, and vacancy content, all properties that influence the local electronic and structural configurations of the iron ions in Prussian blue. The presence of nanocrystalline ferrihydrite as an undesirable iron containing reaction product was identified in Prussian blue pigments prepared according to eighteenth-century recipes. Discoloration upon light exposure in Prussian blue paint layers was induced by accelerated ageing. Pure Prussian blue painted in a dark shade is extremely light fast but fades when either painted in a lighter shade or mixed with white pigments. The fading of Prussian blue was attributed to a reduction of the iron(III) ions at the surface of the paint layer. A partial oxidation of Prussian blue in the entire paint layer was also observed. The analysis of works of art containing Prussian blue confirmed the combined oxidation and reduction of Prussian blue iron ions upon ageing. The study of alteration mechanisms in a painting pigment is essential both for conservation and historical studies in order to best preserve our cultural and artistic heritage with respect to an artist’s original intentions. [less ▲]

Detailed reference viewed: 261 (39 ULg)
Full Text
See detailEtude pluridisciplinaire de l'implication bactérienne du phénomène de blanchissement des coraux Scléractiniaires (Indo-Pacifique)
Ladrière, Ophélie ULg

Doctoral thesis (2012)

Given the increasing number of coral diseases linked to the growing impact of global warming and human activities, the present research focused on the phenomenon of coral bleaching. The Scleractinian ... [more ▼]

Given the increasing number of coral diseases linked to the growing impact of global warming and human activities, the present research focused on the phenomenon of coral bleaching. The Scleractinian Cnidaria are the essential building blocks of the coral reef ecosystem, whose ecological, economic and societal interests are demonstrated. The symptom of bleaching has multiple and complex causes that are still unclear. It corresponds to the rupture of the mutualistic symbiosis between the coral and microalgae, called zooxanthellae, and can causes death of many corals. An assumption underlying this phenomenon suggests that corals are bleaching by the action of pathogenic bacteria, penetrating inside the coral tissues. However, this hypothesis seems quite controversial and the present work attempts to elucidate a set of issues surrounding this controversy. To do this, a multidisciplinary approach combining ecology (general and microbial) and molecular biology has been established through field and experimental studies. Using electron microscopy, morphological criteria were established to characterize the status of coral bleaching. Furthermore, this technique was also used to identify different types of bacteria within coral tissues. Their presence and their role within the coral holobiont were discussed. Several molecular biology techniques (DGGE, sequencing) have provided evidences on the non-specificity of bacterial communities associated with corals species, sampling sites and different status of bleaching. This non-specificity shows that the functions performed by bacteria in the coral holobiont could be the result of opportunistic bacteria from various taxonomic groups. The presence of Cyanobacteria in some corals, detected by microscopy and confirmed by molecular techniques, raises the question about their role within the holobiont and the alternative pathway that they offer for the symbiotic host compared with zooxanthellae. The issues of potential competition between these different symbionts or the benefit of this symbiotic diversity, in case of bleaching event, remain open. Transcriptomic genetics was used to study the response of coral facing a bacterial stress in different experimental conditions of temperature determining the expression of bacterial virulence. Studying the expression profile of genes involved in immunity of the coral allowed to understand the sequence of reactions and changes in resource allocation in response to different stages of bacterial infection. On this experiment, the first antimicrobial peptide of Scleractinia, the damicornin, has been identified and characterized. All these results suggest that the context of changes in environmental parameters is more important than the presence of pathogens itself. The bacteria would then act as an aggravating factor in a situation where the coral, already weakened and stressed, cannot defend itself adequately. Finally, the observation of an increase in cnidocytes in a coral species that has undergone bleaching, suggests that some coral species are able to shift to a more heterotrophic nutritional regime adapting to the lack of inputs caused by the significant loss of zooxanthellae. This would favor the resilience of coral. [less ▲]

Detailed reference viewed: 82 (22 ULg)
See detailImmuno-inflammatory mechanisms in refractory asthma
Manise, Maïté ULg

Doctoral thesis (2012)

Detailed reference viewed: 18 (3 ULg)
Full Text
See detailApplications de la résonance magnétique nucléaire à la chimie des actinides et au retraitement des combustibles nucléaires.
Vidick, Geoffrey ULg

Doctoral thesis (2012)

This research work is dedicated to develop and bring to light the contribution of nuclear magnetic resonance (NMR) in the study of the actinide ions and their complexes in aqueous or in organic solvents ... [more ▼]

This research work is dedicated to develop and bring to light the contribution of nuclear magnetic resonance (NMR) in the study of the actinide ions and their complexes in aqueous or in organic solvents. We use several advanced NMR techniques. The dispersion of the longitudinal relaxation time T1 of solvent nuclei with the magnetic field (NMRD) yields information on the magnetic properties of paramagnetic actinide ions. The sensitivity of NMR to the exact nature of the ground state of actinide ions is also illustrated by detailed studies on the complexes of U, Np, Pu, Am and Cm in different oxidation states. It will be shown that the paramagnetic shifts induced by the actinide ions originate from both a through space dipolar contribution and a through bonds contact contribution. The latter gives access to delocalized unpaired electron densities that are directly related to the covalency of the actinide-ligand bonds. However, electronic densities can only be obtained after separation of the two contributions. This separation made thanks three different methods based on studies with variable temperature and by synthesizing highly symmetric and anisotropic complexes. The use of dipolar contribution can be, as for her, related to the geometry of complexes formed in solution. This method of determination of solution structure is illustrated in the case of four specially designed N-polyaromatic ligands actinide/lanthanide partitioning by liquid-liquid extraction, an essential step for the ultimate nuclear fuel reprocessing. Besides their structure determination, the use of NMR techniques allowed of determined the stoechiometry and speciation in solution of these complexes. [less ▲]

Detailed reference viewed: 41 (10 ULg)
Full Text
See detailDispersal ability and speciation mechanisms in bryophytes
Hutsemekers, Virginie ULg

Doctoral thesis (2012)

Detailed reference viewed: 37 (8 ULg)
Full Text
See detailÉvolution des effectifs des populations d’éléphants d’Afrique soudanosahélienne :enjeux pour leur conservation
Bouché, Philippe ULg

Doctoral thesis (2012)

The first objective of this thesis was to analyze the evolution of Sudano-Sahelian African elephant populations in a context of environmental challenges and increasing human demography. The second ... [more ▼]

The first objective of this thesis was to analyze the evolution of Sudano-Sahelian African elephant populations in a context of environmental challenges and increasing human demography. The second objective was to propose solutions for elephant conservation in the Sudano-Sahelian context. To fulfill these objectives, aerial surveys have been carried out in every protected area harboring a known population of elephants. This work was first implemented at a local level on several study cases and finally at a global level. Results of aerial surveys estimate the current elephant number at minimum 7,745 elephants, about 2% of the African elephant total population. This confirmed that the elephant populations have been progressively fragmented and confined to few protected areas representing 5% of the Soudano-Sahelian strip. The long term (four decades) elephant population trends has been studied by comparing our results with the database of the study area. The half of the monitored population collapse during the last 40 years. The viability of small elephant population of 200 elephants and below is critical and several of them collapsed. Contrasted local situation have been observed : if a number depletion is often observed, in some protected areas elephant populations are stable or increasing. Although, trends of other large mammals’ population is not linked to that of the elephants. This result allow to conclude that the elephant is not a good indicator of the abundance of other large mammals’ population. Causes of elephant populations’ depletion are both due to climate change (global drought) and socio-economic (human demography and land use pressure) issues. An appropriate and permanent field management, a better valorisation of elephants and the creation of negotiated corridors with local people could garantee the future of Sudano-Sahelian African elephants. [less ▲]

Detailed reference viewed: 237 (19 ULg)
Full Text
See detailCaractérisation des espaces périurbains, morphologie actuelle et prospective
De Smet, Fabian ULg

Doctoral thesis (2012)

L’étalement urbain est un défi majeur pour nos territoires européens et plus spécifiquement belges. Il se concrétise par l’urbanisation massive de territoires périphériques de villes, appelés espaces ... [more ▼]

L’étalement urbain est un défi majeur pour nos territoires européens et plus spécifiquement belges. Il se concrétise par l’urbanisation massive de territoires périphériques de villes, appelés espaces périurbains. Cette urbanisation a des conséquences multiples, notamment en termes architecturaux et urbanistiques. Nous avons défini la forme périurbaine comme un état de l’évolution des espaces périurbains, formulé à partir de leurs composantes bâties et de leur organisation. Dans ce contexte, l’objectif principal de cette thèse est l’amélioration de la connaissance de la forme périurbaine. En d’autres termes, il s’agit de contribuer à l’émergence d’un cadre de réflexion sur l’actualité et l’avenir morphologique des espaces périurbains. Pour nous, il s’agit d’un préalable indispensable à la gestion des caractères architecturaux et urbanistiques de ces espaces. Afin d’apporter notre contribution à la construction de ce cadre de réflexion, nous avons structuré notre démarche scientifique autour de trois objectifs plus spécifiques. Ceux-ci structurent cette thèse. Le premier de ces objectifs est l’évaluation de la connaissance et de la reconnaissance des spécificités des espaces périurbains. Dans la première partie de cette thèse, nous nous sommes attaché à faire l’état de la connaissance des espaces périurbains et des concepts qui sont mobilisés pour les décrire. Ainsi, le second chapitre de notre dissertation dresse un bilan critique des connaissances relatives aux espaces périurbains. Dans le troisième chapitre, nous mettons en perspective le vocabulaire mobilisé dans leur description et leur gestion légale et opératoire. Le second objectif de cette thèse est le développement d’un outil d’analyse des tissus bâtis périurbains. Ainsi, le quatrième chapitre de la dissertation porte plus spécifiquement sur les formes périurbaines et leur analyse. Nous y développons la méthode d’observation et d’analyse morphologique de l’espace périurbain que nous avons construite et testée sur l’espace périurbain liégeois. Nous en explicitons le développement et en commentons les résultats. Cette méthode nous a permis de construire une typologie des tissus bâtis périurbains et, ainsi, de proposer un cadre de caractérisation de la forme périurbaine. Le troisième objectif est la proposition de scénarios prospectifs quant aux avenirs possibles de la forme périurbaine. Dans le cinquième chapitre de cette dissertation nous nous sommes intéressé à l’utilisation des résultats de la classification typologique à des fins de simulations prospectives. Sur base de ces résultats, nous avons construit des scénarios d’évolution potentielle de l’urbanisation périurbaine et de la forme périurbaine. [less ▲]

Detailed reference viewed: 253 (30 ULg)
See detail"Identification organisationnelle et changement: les logiques identitaires à l'épreuve du New Public Management"
Rondeaux, Giseline ULg

Doctoral thesis (2012)

Depuis près de 30 ans, nombre de pays se sont engagés dans la réforme de leur administration publique, inspirée du New Public Management (NPM), inspirant de multiples travaux et débats sur ses fondements ... [more ▼]

Depuis près de 30 ans, nombre de pays se sont engagés dans la réforme de leur administration publique, inspirée du New Public Management (NPM), inspirant de multiples travaux et débats sur ses fondements et ses déclinaisons, ses avantages et inconvénients, sa pertinence, ses paradoxes ou encore les difficultés liées à sa mise en oeuvre ou à son évaluation. Construit comme une critique des règles de l’administration bureaucratique, ce modèle managérial constitue une profonde remise en cause de celle-ci en termes d’organisation, de management, de GRH et de valeurs fondamentales. Les réformes inspirées du NPM sont aussi à la base d’une redéfinition de l’identité organisationnelle institutionnalisée de l’administration (Du Gay, 1996) : l’organisation s’interroge sur ce qu’elle est, ce qu’elle devient, ce qu’elle veut être, propulsant l’identité organisationnelle au premier plan des préoccupations. Alors que le processus de modernisation de l’administration vise à redéfinir la réponse à la question « qui sommes-nous en tant qu’organisation ? », de quelle manière les membres de celle-ci en font-ils l’expérience? Au travers de l’analyse de trois cas de réforme d’administrations publiques, notre thèse s’intéresse aux dynamiques d’identification à l’oeuvre en regard de la perception des évolutions du contexte par les individus. Nous mettons en évidence le lien qui existe entre les processus d’identification organisationnelle et deux dimensions spécifiques à chaque contexte en évolution : le caractère plus ou moins radical de changement d’identité organisationnelle institutionnalisée que suppose la réforme mise en œuvre, et le degré de maturité de ce processus de réforme, ou en d’autres termes la mesure dans laquelle la réforme est plus ou moins perceptible dans la transformation du contexte même. Au départ des différents éléments relevés dans chacun de nos terrains, notre thèse illustre concrètement comment la mise en œuvre d’un management polyphonique du processus de changement peut contribuer de manière positive à l’identification organisationnelle des membres de ces organisations en évolution. Cette approche mène à réfléchir autrement à la gestion du changement au travers de la prise en compte de cette diversité de positionnements identitaires. Elle conduit en outre à une réflexion plus large sur la mise en œuvre du NPM et sur l’administration publique de demain. [less ▲]

Detailed reference viewed: 109 (28 ULg)
Full Text
See detailFeeding and ranging behavior of northern pigtailed macaques (Macaca leonina): impact on their seed dispersal effectiveness and ecological contribution in a tropical rainforest at Khao Yai National Park, Thailand
Albert, Aurélie ULg

Doctoral thesis (2012)

Southeast Asia experiences an exceptional loss of natural habitat due to a deforestation rate that strongly increased during the last decades. The first consequence is the loss of many animal and plant ... [more ▼]

Southeast Asia experiences an exceptional loss of natural habitat due to a deforestation rate that strongly increased during the last decades. The first consequence is the loss of many animal and plant species, threatened by their habitat degradation and by the loss of interactions necessary to the survival of the whole ecosystem. Large mammals and birds populations, the principal dispersal agent of some plant species, already collapsed massively due to hunting and habitat fragmentation and now threaten to die out. Among the large frugivorous species, primates are particularly vulnerable. Only few species, such as macaques, are able to survive in some man-made habitats, due to their opportunistic life-style. But, in the long term, habitat destruction, hunting and capture for local trade threaten their survival. The extinction of primates in Southeast Asian forests would be disastrous for many plant species as primates are among the major seed-dispersal agents. The study of Macaca, the only Cercopithecinae genus in Southeast Asia, could provide a better understanding of the role of cheek-pouched monkeys in tropical rainforest maintenance and restoration. In this study, we chose to focus on northern pigtailed macaques (Macaca leonina) as few studies were carried out on this species, making data concerning its ecology and behavior highly limited. Their seed dispersal capacity, although unknown, is potentially high and pigtailed macaques could be as good seed dispersers as sympatric frugivores. They seem to eat a large number of fruits of many plant species, process seeds with care, and range daily over large areas. Moreover they could have a role in forest maintenance and regeneration given that they seem to eat species with all seed sizes, belonging to all plant life forms present in the forest, and they are able to cross various habitat types (primary as well as secondary forests). After providing an outline of our current knowledge on seed dispersal by Cercopithecinae species and their specific role in forest regeneration, our aim was to highlight the importance of northern pigtailed macaques on seed dispersal and thus on forest regeneration by studying (1) how their eco-ethological characteristics can make them effective dispersers, from a quantitative and a qualitative point of view, (2) how the influence of biotic factors, such as resources and predation, on their activities and movements may impact their seed dispersal effectiveness, and (3) what role Macaca spp. can have in a seed dispersal assemblage. While following a troop of northern pigtailed macaques habituated to humans in Khao Yai National Park, Thailand, we recorded their behavior, travels, and consumed items, from dawn to dusk. Moreover, we studied the spatio-temporal distribution of fruits included in their diet, and the characteristics of their sleeping sites. Finally, we performed germination and viability tests on ingested seeds. Results showed that northern pigtailed macaques could disperse thousands of seeds, up to 58 mm in length, coming from the 126 fruit species they eat. Especially, they could disperse them from primary to secondary forest, thanks to handling techniques such as swallowing, spitting and dropping. Finally, the seed passage through their digestive tract mostly had a neutral or positive effect on seed germination and viability. Macaques observed in this study satisfied therefore most requirements defining effective seed dispersers in both quantitative and qualitative terms and we can conclude to the potential importance of Macaca leonina in the tropical rainforest regeneration. To confirm the seed dispersal effectiveness of M. leonina, we needed to make sure that its ranging behavior did not negatively affect dispersed seeds. Moreover, given the importance of human food in their diet, we wondered if this resource had a negative impact on seed dispersal. Our results showed that northern pigtailed macaques adapted their ranging pattern according to fruit availability. Moreover, during fruit scarcity, they shifted their diet from frugivorous to omnivorous with an important part of human food. However, human food did not seem to have an impact on seed dispersal in high fruit abundance periods where macaques had a large home range, traveled long distances and ate mainly fruits. However, in low fruit abundance periods, macaques decreased their home range size, traveled shorter distances and ate mainly human food. This latter could have a negative impact on the seed dispersal of some rare fructifying species. However, these species were eaten by many other animal species able to provide good dispersal services. Then, we showed that sleeping sites characteristics and pre-sleep behavior in M. leonina were influenced by the proximity of resources and the risk of predation. Given that macaques used few sleeping sites, defecated when they woke up and that all troop members slept concentrated in a small area, we think that they created a high seed density below the sleeping trees. This may be harmful for some seed species but may be beneficial for the ecosystem. Moreover, this pattern may be shown in other effective seed dispersers in the park. So as harmful for seeds it may be, it does not make pigtailed macaques less effective than other frugivores. Finally, we demonstrated that Macaca species are important associates in the seed dispersal assemblage found in Southeast Asian forests. Indeed they may disperse most plant species, usually more efficiently dispersed by other frugivores, and thus provide a significant complement in term of dispersal quantity. Moreover, they are sometimes the only frugivores able to disperse the seeds of some species, mainly large-seeded and/or protected ones, and may thus bring them a vital dispersal service. [less ▲]

Detailed reference viewed: 151 (12 ULg)
See detailModèles d'écoulements incompressibles en plan vertical appliqués aux structures du génie civil
Detrembleur, Sylvain ULg

Doctoral thesis (2012)

Le travail entrepris s’intègre complètement dans la filière d’étude propre au HACH, à savoir une interaction étroite entre modèles numériques et validation sur bases d’éléments issus de la modélisation ... [more ▼]

Le travail entrepris s’intègre complètement dans la filière d’étude propre au HACH, à savoir une interaction étroite entre modèles numériques et validation sur bases d’éléments issus de la modélisation physique. Les hypothèses restrictives du modèle intégré sur la hauteur (WOLF2D) ont été gommées par l’ajout de deux nouveaux modules permettant de calculer explicitement la distribution des variables hydrodynamiques sur la hauteur de l’écoulement. L’utilisation intensive du code bidimensionnel horizontal et les modélisations diverses et variées menées au moyen de ce module ont conduit à de nombreuses implémentations nouvelles dans ce code, permettant de traiter un nombre grandissant de situations complexes. L’utilisation d’un maillage structuré, même différentiable spatialement au moyen d’une technique multiblocs, ne permet cependant pas à l’utilisateur de représenter adéquatement certaines géométries complexes. Il ressort de ce constat que les techniques numériques à même de supprimer cette dépendance ont fait l’objet d’une partie de cette recherche, en permettant l’utilisation de contours quelconques qui ne respectent pas nécessairement la structure cartésienne du maillage. Ces développements ont tout naturellement conduit à la modélisation d’interactions de structures solides sur le fluide. D’autre part, le grand nombre de modèles hydrodynamiques spécifiques implémentés dans le code WOLF2D trahissent une volonté d’intégrer les variations verticales des composantes hydrodynamiques agglomérées par l’intégration sur la hauteur. Ces distributions peuvent, certes, être maîtrisées dans une certaine mesure, mais ne peuvent en aucun cas reproduire la dynamique complexe qui est observée dans la direction d’intégration de ce type de modèle. Par conséquent, la partie principale des recherches entreprises dans cette thèse est concentrée sur le développement d’un modèle bidimensionnel explicitement discrétisé sur la verticale (WOLF2DV) qui permet de combler le manque d’informations distribuées induit lors de l’élaboration d’un modèle bidimensionnel horizontal. L’obtention de ces informations a cependant un coût, puisque la structure et la technique de résolution du système d’équations est différente des modèles intégrés sur la hauteur ou sur la section et engendre des coûts de calcul supplémentaires. Afin de conserver la philosophie générale de la suite logicielle WOLF, qui se veut polyvalente et efficace même sur de grandes applications réelles, un effort considérable a été consenti lors de l’évaluation des techniques de résolution et de leur implémentation et ce, afin de conserver des temps de calcul acceptables. En outre, la volonté de s’affranchir de la discrétisation sur des maillages structurés transparaît également au niveau des recherches entreprises pour ce code explicitement discrétisé sur la verticale puisqu’un second challenge important a consisté en l’élaboration d’une technique de suivi d’interface adaptée. Finalement, les résultats probants et prometteurs fournis ont amené tout naturellement à étendre ce module bidimensionnel vers la troisième dimension et à ainsi représenter explicitement un écoulement tridimensionnel (WOLF3D). Compte tenu de la lourdeur de développement dans la troisième dimension, ce module est limité aux écoulements sous pression et constitue la base de recherches futures qui viseront à adjoindre à ce code une gestion de surface libre ou encore des modèles de turbulence. [less ▲]

Detailed reference viewed: 66 (6 ULg)
Full Text
See detailAfter Melancholia: A Reappraisal of Second-Generation Diasporic Subjectivity in the Work of Jhumpa Lahiri
Munos, Delphine ULg

Doctoral thesis (2012)

While Jhumpa Lahiri’s work might be thought of as one of the most emblematic instances of the popularity of today’s Indian-American diasporic literature, it remains that its hyper-visibility coincides ... [more ▼]

While Jhumpa Lahiri’s work might be thought of as one of the most emblematic instances of the popularity of today’s Indian-American diasporic literature, it remains that its hyper-visibility coincides with an odd form of critical invisibility. This is not to say that critical interventions on Lahiri’s three books have been nonexistent, nor could they have been in view of the fact that the author won the Pulitzer Prize in 2000 for her first collection of short-stories, Interpreter of Maladies. But the vast majority of these readings takes as its premise that view that cultural assimilation and hybridity are still valid notions to investigate narratives focusing on members of the second generation, even as these descendants of migrants consider themselves Indian simply by virtue of their parents, so that they can only claim a second-hand knowledge of migration. Ignoring the difference between first and second-generation Indian-American diasporic experiences – and, what is more, overlooking the fact that the offspring of migrants, unlike their parents, “[do] not really have any other place [than the U.S.] to call home” (Lahiri) – such critical consensus ignores important aspects of Gogol’s complex trajectory in The Namesake. Worse, it proves highly unsatisfactory when it comes to discussing Lahiri’s recent collection of short stories, Unaccustomed Earth, in which the second generation’s accession to early middle age calls into question various preconceptions on heritage and transmission. Can it be then that what is passed on from one generation to the next organizes itself less around positive, than negative entities, that is, around categories such as the gap, the absent, and the unsaid? Taking its cue from Vijay Mishra’s understanding of the diasporic subjectivity in terms of an impossible mourning, my dissertation examines the ways in which Lahiri redefines the notions of belonging and arrival as regards the Indian-American second generation not in terms of cultural assimilation – which would hardly make sense for characters who were born in the U.S. in the first place – but in terms of a re-symbolization of the gaps in the parents’ migrant narratives, more particularly in terms of the “phantom loss” haunting transgenerational relationships between migrants and their offspring. While investigating the figures of emptiness, spectrality, and the message, my dissertation takes various psychoanalytic theories by Sigmund Freud, Julia Kristeva, Nicolas Abraham, Maria Torok and Jean Laplanche, among others, as its major methodological tools. As against a critical consensus that overemphasizes matters of culture, such theoretical framework aims to revaluate the power of the literary in Lahiri’s work. Although this dissertation extends, at times, to Lahiri’s three books, its four chapters boil down to a close reading of the three texts constituting the “Hema and Kaushik” trilogy, which also form part 2 of Lahiri’s 2008 collection of short stories, Unaccustomed Earth. Through these three narratives, which all traffic with the dead-mother metaphor, Lahiri can be seen to inscribe the dimension of mourning at the heart of her approach to “generational arrival.” The three short stories of “Hema and Kaushik” indeed bring to the fore some unacknowledged facets of the much-idealized diasporic experience, which forces us to revise the cultural scenarios through which today’s contemporary world constructs, even essentializes, the figure of the migrant as an emblem of ultimate freedom. My close reading of “Hema and Kaushik” falls into four parts. Part 1 looks at “Once in a Lifetime,” the first text of Lahiri’s trilogy, with a view to showing how the apostrophic form of the text opens up a space of mourning which might blur the boundaries between absence and presence, return and arrival, self and other, but also positions Kaushik, for Hema, as a transitionary figure whose absence might well prove crucial in letting Hema-as-narrator acquire her own generational voice. Part 2 is devoted to “Year’s End,” and investigates the ways in which Lahiri employs the Gothic to represent the second generation as being haunted by its own belatedness in relation to the first generation’s experiences. The psychoanalytic theories of Nicolas Abraham and Maria Torok, among others, will help me clarify how the dead-mother metaphor, in “Hema and Kaushik,” proves tightly interweaved with notions of transgenerational transmission, connection, and infiltration. Calling into question the possible unity of the “I” in the second text of the trilogy, Part 3 tracks the mole, so to speak, and bears witness to aspects of Lahiri’s work that are not all “in the words,” but “among the words,” to borrow Marcel Proust’s suggestive phrase, notably by revisiting aspects of “Once in a Lifetime” and “Years’ End” that are given a new significance through the interplay of the three texts of the trilogy. Relying on André Green’s concept of the “dead mother,” I will then propose an alternative reading of Lahiri’s trilogy in which Hema’s and Kaushik’s romance is only a surface-plot, enlisted to give representability to “the great unspeakable” of Hema’s life. In Part 4, Jean Laplanche’s description of the formation of the ego and the unconscious in relation to “early messages of the m/other” will allow me to look behind the curtain of transgenerational forms of melancholia, to that place where infinite longing is shown to organize itself not around any “real thing” but around a phantom entity whose idealization covers up the necessity to grapple with one’s involvement in a history of loss, which is also a history of guilt. [less ▲]

Detailed reference viewed: 136 (32 ULg)
Full Text
See detailApplication of molecular tools to study the hydrogen production by the bacteria of the genus Clostridium
Calusinska, Magdalena ULg

Doctoral thesis (2012)

L’hydrogène moléculaire a un potential énorme comme futur vecteur énergétique car sa combustion n’est pas polluante. Cependant, les processus industriels actuels de production contribuent ... [more ▼]

L’hydrogène moléculaire a un potential énorme comme futur vecteur énergétique car sa combustion n’est pas polluante. Cependant, les processus industriels actuels de production contribuent substantiellement à l’effet de serre. Au contraire, une production d’H2 qui est neutre en CO2 peut être obtenue par la fermentation anaérobique obscure. Les bactéries du genre Clostridium peuvent fermenter les sucres en H2 et CO2 avec production d’ acide acétique et butyrique qui servent d’accepteurs principaux d’électrons. Cependant, en fonction de la souche/co-culture utilisée et des conditions de culture, des composés plus réduits peuvent être obtenus, par ex. l’éthanol, le lactate, ce qui réduit substantiellement le rendement final en H2. De plus, les différentes voies métaboliques et les circuits de régulation conduisant à la production d’H2 dans les clostridies ne sont pas bien connus. Dans cette étude, nous avons étudié deux sujets principaux. D’une part, nous avons étudié différentes co-cultures de Clostridium spp. dans des bioréacteurs produisant de l’H2. En suivant les co-cultures de C. butyricum et C. pasteurianum par FISH (Fluorescence in situ hybridisation) et qPCR (quantitative real-time PCR), nous avons montré que les deux espèces co-existent de manière stable durant la fermentation de différents sucres dans deux bioréacteurs. D’autre part, en utilisant Clostridium butyricum CWBI1009 comme modèle, nous avons étudié le métabolisme complexe de l’H2 chez les clostridies. La découverte de gènes nouveaux codant pour des hydrogènases [FeFe] dans les génomes séquencés a changé notre vue de la façon dont ces microbes produisent l’ H2. En effet, en utilisant différents outils moléculaires (2D-DIGE, RT-qPCR et RNA-seq), nous avons montré que dans différents conditions de milieu, différentes hydrogénases contribuent à la production d’H2. De plus, sous atmosphère d’N2 pendant la fermentation du glucose dans des conditions de pH non régulées, nous observons que la nitrogénase contribue à la production globale d’H2. De manière surprenante, alors que les clostridies semblent bien équipées pour produire de l’H2, elles n’ont probablement développé cette capacité que pour s’adapter rapidement aux variations de conditions, cad la diminution du pH. Donc, pour maintenir un pH intracellulaire constant, elles rejettent les protons (sans doute sous forme de H2) dans le milieu. Ainsi, elles se débarrassent de l’excès d’équivalents réducteurs produits pendant la fermentation du glucose. En résumé, nos résultats contribuent à une meilleure connaissance du métabolisme complexe de l’H2 chez les clostridies. Cependant, un défi pour le futur consiste à caractériser les enzymes responsables de ce métabolisme et, par bioengineering métabolique, de développer des systèmes microbiens optimaux pour la conversion de la biomasse en H2. [less ▲]

Detailed reference viewed: 156 (13 ULg)
Full Text
See detailTraverser la Belgique ? De l'Indépendance au Plan Schlieffen (1839-1905)
Bechet, Christophe ULg

Doctoral thesis (2012)

La question des voies de communication belges liée à la politique de défense du pays et aux plans de guerre des puissances voisines n’avait encore jamais fait l’objet d’une recherche systématique pour ... [more ▼]

La question des voies de communication belges liée à la politique de défense du pays et aux plans de guerre des puissances voisines n’avait encore jamais fait l’objet d’une recherche systématique pour cette période importante qui s’étend de l’indépendance de la Belgique à l’aube du premier conflit mondial. L’étude de cette problématique est étroitement liée à celle des perceptions entretenues au sein des milieux diplomatiques et militaires des deux grandes puissances voisines de la Belgique ; la rivalité franco-allemande tout au long du 19e – début 20e siècle a en effet induit un questionnement continuel des diplomates et des hommes de guerre français et allemands sur le rôle de l’espace belge en cas de guerre future. Par un effet de balancier, ces perceptions étrangères ont elles-même influencé en retour les réflexions stratégiques de la diplomatie et du milieu militaire belge et in fine la politique défensive du pays. Afin de vaincre l’apparente hétérogénéité de l'objet d'étude comme les difficultés liées à la longueur de la période choisie, le concept de « traversée » du territoire belge entre la France et l’Allemagne s’est imposé comme l’axe de réflexion idéal, capable de réunir dans un même travail des événements divers de l’histoire militaire et diplomatique belge. Ainsi se détachent sur le « temps long » des constantes géopolitiques et géostratégiques liées à l’espace belge, à ses routes, chemins de fer et fortifications militaires. Les termini chronologiques choisis sont d’une part le traité des XXIV articles de 1839 et d’autre part le « Plan Schlieffen » (1905-1906). Néanmoins, pour des raisons d’unité, certaines thématiques débutent avant 1839 tandis que d’autres sont poursuivies jusqu’en 1914. C’est le cas de la problématique des nouvelles lignes de chemins de fer entre la Belgique, le Grand-Duché de Luxembourg et l’Allemagne, dont l’intérêt stratégique n’est pas évident si l’on choisit de s’arrêter arbitrairement à 1905. Pareillement, la problématique des plans du Génie belge pour interrompre les ponts de la Meuse et les tunnels ferroviaires en cas de conflit a été poursuivie jusqu’en 1914 pour conserver toute sa pertinence. En revanche, concernant l’étude des plans de guerre, la date de 1905-1906 a été privilégiée pour des raisons historiographiques justifiées dans notre introduction. Un des objectifs principaux de cette thèse est en effet de présenter et d’analyser l’évolution des plans français et prusso-allemands depuis 1839 dans leur relation avec la Belgique jusqu’au moment où l’on a dit admettre la violation de la neutralité belge comme un fait inéluctable. « Comment en est-on arrivé là ? », telle est la question à laquelle nous répondons. Sur le plan diplomatique, cette transition stratégique correspond aux débuts de l’Entente cordiale et à la conférence d’Algésiras, événements qui viennent complexifier la problématique du plan de guerre français par l’envoi hypothétique d’un corps expéditionnaire britannique appelé à opérer éventuellement en Belgique. En Allemagne, cette date charnière correspond à la retraite du général Alfred von Schlieffen. Un des autres aspects novateurs de cette thèse est d’étudier, parallèlement au processus d’élaboration des plans de guerre, l’évolution de l’infrastructure ferroviaire belge et de ses relations avec les pays limitrophes. Nous prouvons en définitive que l’évolution du réseau belgo-allemand, principalement dans la région Eifel/Ardennes, a eu une grande influence sur les plans d’Etat-major du début du 20e siècle. La fameuse « trouée du Luxembourg » les conduit à assumer progressivement le passage par la Belgique comme une future réalité de guerre. Enfin, malgré cette date charnière de 1905-1906, il nous a paru intéressant de problématiser ensuite dans un épilogue non exhaustif la question des plans français et allemands de l’immédiat avant-guerre, toujours en relation avec la traversée du territoire belge. Le chercheur y trouvera, nous le pensons, d’utiles pistes de réflexion pour des études ultérieures. [less ▲]

Detailed reference viewed: 280 (25 ULg)
Full Text
See detailIngénierie génétique d'une β2-intégrine LFA-1 bovine résistante à la leucotoxine de Mannheimia haemolytica
Fett, Thomas ULg

Doctoral thesis (2012)

Domesticated bovines are known since decades to be prone to bacterial pneumonias. Among the causative agents, a consensus emerged stating that Mannheimia haemolytica is the most frequent bacterium ... [more ▼]

Domesticated bovines are known since decades to be prone to bacterial pneumonias. Among the causative agents, a consensus emerged stating that Mannheimia haemolytica is the most frequent bacterium isolated from bovine lungs throughout the world. Moreover, it appeared that its virulence specifically targets ruminant lungs in vivo and ruminant leucocytes in vitro. When the thesis was started, the two main actors underlying this species-specific virulence were known: the leukotoxin (LKT) on the pathogen side and the beta2-integrin LFA-1 on the host side. The objective of the thesis was to contribute to the understanding of the LKT/LFA 1 interaction at the molecular level. Using a between-species perspective, we showed that (i) the CD11a subunit of the LFA-1 heterodimer was not involved in the LKT-specificity for ruminant LFA-1, (ii) the EGF-3 module within the CD18 controls the susceptibility of any given CD18 to LKT and (iii) a non cleavable signal peptide conjugated to a LKT susceptible EGF-3-containing CD18 exacerbates LKT pronecrotic effects. [less ▲]

Detailed reference viewed: 56 (7 ULg)
Full Text
See detailContribution à l'étude des propriétés tensioactives et membranaires d'esters dérivés de la glycine bétaïne
Nsimba Zakanda, Francis ULg

Doctoral thesis (2012)

The objective of this doctoral research is to contribute to the study of surface active and membrane properties of esters derived from glycine betaine. In this context, esters of glycine betaine ... [more ▼]

The objective of this doctoral research is to contribute to the study of surface active and membrane properties of esters derived from glycine betaine. In this context, esters of glycine betaine (alkylbétaïnate chlorides: CnBC, n = 10-16) were obtained using a new synthetic methodology. Glycine betaine (activated by thionyl chloride) and the primary fatty alcohols were used as basic raw materials for the chemical synthesis of CnBC. Some parameters to optimize the synthesis were studied, such as the nature of the organic solvent, the temperature, the molar ratio of reactants and the concentration of the latter in the reaction medium. Next, the surface active and membrane properties of CnBC were characterized using several instrumental techniques such as Langmuir film balance, isothermal titration calorimetry, fluorescence spectrometry and zeta potential and particle size measurements. Hexadécylbétaïnate chloride (C16BC) was synthesized with better performance under the following conditions: absence of a catalyst/base, a solvent of medium polarity (2-methyl-2-butanol), a temperature of 45°C, a molar ratio of betainyl chloride/1-hexadecanol of 3/1 and a concentration of reactants of 0.132 mol/L. Decylbetainate chloride (C10BC) dodecylbetainate chloride (C12BC) and tetradecylbetainate chloride (C14BC) were obtained using the optimal conditions for the synthesis of C16BC. Concerning the interfacial organization of CnBC, C10BC and C12BC did not form insoluble monolayers at the air-water at 20°C compared to their counterparts, C14BC and C16BC. The study of the monolayer of C16BC in various conditions of the aqueous subphase showed that the pH and monovalent anions (OHˉ, Brˉ, NO3ˉ, ClO4ˉ) did not influence the behavior of the monolayer compared to that in water with Clˉ as counterion while the temperature beyond 25°C, the divalent anions (HPO42-, SO42-) and the ionic strength of sodium sulfate (Na2SO4) affected it in term of interfacial area occupation of the molecules. Interactions between CnBC and model membranes have shown that in water, CnBC, regardless of the length of the alkyl chain, have highly penetreted into the negatively charged lipid monolayers (dipalmitoylphosphatidylserine and dipalmitoylphosphatidic acid), whereas their penetration was average and low into monolayers formed by lipids with small polar head (dipalmitoylphosphatidylethanolamine and cholesterol, CHOL) and lipid with large polar head (palmitoyloleoylphosphatidylcholine, POPC), respectively. In salted buffer, the adsorption of C16BC at the air-water interface and onto the surfaces of the lipid monolayers was instantaneous, and in all cases, the penetrating power was above the presumed pressure of biological membranes. C16BC formed miscible and stable mixtures with POPC and sphingomyelin while an almost ideal behavior was observed for its mixtures with CHOL. An affinity of C16BC for the membrane bilayer containing CHOL was also observed. The adsorption of CnBC onto the surfaces of bilayers was alkyl chain-dependent. C10BC, C14BC and C16BC did not significantly perturbed membranes even at high surfactant concnetrations compared to C12BC that has highly perturbed membranes without solubilizing them. In all cases, particles of positive charge and larger than those of membrane bilayers prepared were formed in the presence of high amounts of CnBC. [less ▲]

Detailed reference viewed: 44 (6 ULg)
Full Text
See detailContribution à l'étude de la surveillance de la mécanique ventilatoire du nouveau-né ventilé.
RIGO, Vincent ULg

Doctoral thesis (2012)

Mechanical ventilation, still a major intervention to improve prognosis in newborns, requires careful monitoring of ventilated infants. This monitoring integrates different parameters. Its classical focus ... [more ▼]

Mechanical ventilation, still a major intervention to improve prognosis in newborns, requires careful monitoring of ventilated infants. This monitoring integrates different parameters. Its classical focus is on blood gases and their proxy (pulse oxymetry, transcutaneous oxygen and carbon dioxide content), and also includes physical assessment, thoracic imaging and appraisal of ventilator settings. Use of currently available on-line respiratory mechanics (RM) as displayed by ventilators seems limited given a large apparent variability. As current respiratory support strategies aim to reduce exposure to mechanical ventilation and to decrease ventilator associated lung injuries, additional continuous monitoring tools could benefit neonatal patients. In a review of advanced biomedical devices in use in the neonatal intensive care units and areas where improvement or evaluation is necessary, the National Institute for Child Health and Human Development underlines simple tools for continuous assessment of vital pulmonary functions at the bedside. This research aims at finding solutions to that problem. In a first step, different respiratory mechanics parameters (dynamic compliance –Cdyn, dynamic resistance –Rdyn, tidal volume –VT and the overdistension parameter C20/C) are obtained from ventilatory recordings of newborns under respiratory support with the most commonly used neonatal ventilator to evaluate their clinical relevance. Those data present a high variability and therefore lack precision. It is possible to mathematically decrease this variability by using parameters averaged over a few minutes and to obtain reproducible results. Continuous pressure, flow and volume data from the ventilator allow construction of pressure-volume, pressure-flow and flow-volume loops. From those loops, Cdyn, Rdyn and VT can be computed by the Mead-Whittenberger method. Those values when derived from respiratory cycles with good appearance significantly differ from ventilator values. Given the lack of precision of ventilator derived respiratory mechanics data, a new strategy is developed to obtain those parameters only from optimal looking respiratory cycles. A new software is designed to reconstruct waves and loops from the ventilator continuous recordings. This software individualises respiratory cycles and compute Cdyn and Rdyn (least mean square method), VT and C20/C. Using 10 sets of two recordings (one in Synchronized Intermittent Mandatory Ventilation and one in Assist/Control ventilatory modes), visual evaluation of 11274 respiratory cycles selects 4847 cycles considered optimal looking. Those assisted cycles present no or minimal leak, good hysteresis of the pressure-volume loop, and no abnormalities of the flow curves. The coefficients of variation of the respiratory mechanics parameters obtained with this method are significantly decreased, by 25-27% from the ventilator values for Rdyn, Cdyn and C20/C, and by 60% for VT. This increase in parameters precision is associated with an improved capacity to discriminate different values. Analysis of discordant values between ventilator and optimal respiratory cycles is relevant. In A/C mode, the VTs from the selected respiratory cycles are lower than values reported by the ventilator, suggesting that currently available VTs give incomplete information for adjustment of ventilator settings. In SIMV mode, the weak correlation between Cdyn from both methods leads to question the relevance of ventilator informations. The important scattering of ventilator C20/Cs out of classical values, and the absence of correlation with values from selected respiratory cycles demonstrate the lack of validity of ventilator C20/Cs. Overall, the results suggest that the use of data derived from selected respiratory cycles could underlie the conception of RM monitoring tools to support ventilatory management. To avoid the heavy workload associated with visual respiratory cycles’ selection, the software is improved to automatically identify optimal cycles. The positive predictive values and specificity of this selection are high. Respiratory mechanics parameters from cycles selected automatically are very concordant with those from visually selected cycles. The last step of this work assesses the software potential with analysis of 21 recordings from various clinical situations. The discriminating power of automatically selected respiratory cycles’ parameters is tested in an extended population. Trending abilities of those parameters are evaluated. Analyses of respiratory mechanics parameters derived from automatically selected cycles are able to demonstrate differences of 4.6-7.1% and more between parameters from two 10min recordings. Averaging data over 3-7min allows to determine a 10% difference. Parameters averaged over 10min allow detection of 10% changes in most patients. Those results should allow building trend curves with clinically and statistically significant informations. In conclusion, the continuous respiratory mechanics analysis software developed and evaluated in this work should give precise informations on the dynamic evolution of RM parameters. Functions integrated in the last version of the software give immediate research opportunities, and should lead to clinical application in a very near future. Those parameters could then complete current informations integrated in ventilatory management. [less ▲]

Detailed reference viewed: 46 (4 ULg)
Full Text
See detailLes jeunes Belges francophones et le génocide des Juifs. Les enseignements d’une perspective de socialisation politique
Grandjean, Geoffrey ULg

Doctoral thesis (2012)

La mémoire du génocide des Juifs est encore vivace dans nos sociétés contemporaines. Ce fait passé apparaît fréquemment dans l’actualité au rythme des commémorations régulièrement organisées. Mais que ... [more ▼]

La mémoire du génocide des Juifs est encore vivace dans nos sociétés contemporaines. Ce fait passé apparaît fréquemment dans l’actualité au rythme des commémorations régulièrement organisées. Mais que peut-il signifier aujourd’hui pour de jeunes générations qui en prennent connaissance à l’école, en famille, par la visite de lieux de mémoire ou encore par de multiples œuvres cinématographiques ? Les impacts de ces connaissances sont ainsi très peu étudiés, notamment en termes d’apprentissage d’attitudes et de comportements politiques chez des jeunes amenés à devenir les citoyens de demain. En s’inscrivant dans le champ de la socialisation politique, l’objectif de cette étude est justement d’analyser les conséquences de ces connaissances. Pour ce faire, de jeunes Belges francophones ont été rencontrés dans le cadre de groupes de discussion. L’analyse des échanges montre que ces jeunes ont tenu différentes expressions sociales et politiques à partir de discussions portant uniquement sur le génocide des Juifs. En soulignant l’importance du souvenir, en témoignant de multiples émotions et en mobilisant toute une série de valeurs, ils ont envisagé la transmission de ce fait passé. Par ailleurs, leurs connaissances et leurs perceptions de l’univers politique ainsi que la façon dont ils envisagent leur participation politique interrogent leur rapport au pouvoir politique. En explorant l’univers mental des jeunes à partir de la thématique du génocide des Juifs, leur prise de conscience des cheminements politiques conduisant à un tel fait est mise en perspective. C’est aussi l’éventualité de sa répétition ou encore l’effacement de sa mémoire dans la dynamique des générations qui est mis en questions et en débats. [less ▲]

Detailed reference viewed: 181 (13 ULg)
Full Text
See detailDirect imaging, photometry and spectroscopy of gravitationally lensed quasars
Ricci, Davide ULg

Doctoral thesis (2012)

Detailed reference viewed: 21 (3 ULg)
Full Text
See detailEsthétique, affectivité et réflexivité. Essai sur la dimension interculturelle de l'anthropologie existentielle de Jean-Paul Sartre
Nke, Fridolin ULg

Doctoral thesis (2012)

Using existential anthropology in understanding contemporary history I try to reveal the value of the Sartrean model of intentional consciousness in understanding the human relationships and the political ... [more ▼]

Using existential anthropology in understanding contemporary history I try to reveal the value of the Sartrean model of intentional consciousness in understanding the human relationships and the political conflicts of our time. I examine the cultural aspects of Sartre’s thought. Sartre’s existential anthropology of the historical real-life refers to a complex philosophical method inspired by Husserl’s phenomenology, Freud’s psychoanalysis and Marx’s dialectic. It aims at understanding individual’s imaginary and behavior. Using that method, not only are we able to reveal the structure of people’s intentions in building and defending their personal and national interests, but also can we manifest the imaginary that constitute what Sartre designates by Dog’s mind, that meant criminal’s and racist’s beliefs. Sartre used his method in understanding writers as Baudelaire, Flaubert or Genet, who was also a criminal. Our intention is to apply psycho-analysis in understanding great figures of human history, such as Hitler, the “Dog” of our time, so that we shall be able to built harmless intercultural relationships. [less ▲]

Detailed reference viewed: 40 (6 ULg)
Full Text
See detailÉvaluation de l’impact de l’extrapolation de bioréacteur sur la physiologie de Yarrowia lipolytica pour la production de lipase
Kar, Tambi ULg

Doctoral thesis (2012)

Les travaux entrepris au cours de cette thèse visent à mettre en place une méthodologie globale d’extrapolation de bioréacteurs. Le procédé de production de lipase par Yarrowia lipolytica a été plus ... [more ▼]

Les travaux entrepris au cours de cette thèse visent à mettre en place une méthodologie globale d’extrapolation de bioréacteurs. Le procédé de production de lipase par Yarrowia lipolytica a été plus particulièrement investigué, compte tenu de la complexité du système biologique et des paramètres physico-chimiques mis en œuvre. En effet, ce procédé met en œuvre une levure dite non conventionnelle dans un réacteur multiphasique G-L-L comprenant un substrat hydrophobe (le méthyloléate étant utilisé comme source de carbone renouvelable). Du fait du caractère strictement aérobie de ce type de levure, le transfert d’oxygène est un paramètre critique pour ce procédé. Dans un premier temps, l’ensemble des paramètres physico-chimiques clés du procédé ont été investigués (c’est-à-dire la dispersion du méthyloléate, les fluctuations en oxygène dissous et en pH). Cette évaluation a été menée en se basant sur des paramètres physico-chimiques (mélange du réacteur, transfert d’oxygène,…), mais également sur base de paramètres biologiques (synthèse et excrétion de la lipase, activation du gène lip2,…). Cette première étude a démontré que le paramètre critique était la fluctuation de l’oxygène dissous, ce paramètre menant à une réduction du rendement spécifique en lipase, liée à une atténuation de l’activité du gène lip2 codant pour la lipase extracellulaire de Y. lipolytica. Ce paramètre est d’autant plus important que les amplitudes des fluctuations en oxygène dissous sont amplifiées lors du processus de montée en échelle pour l’extrapolation du procédé. L’efficacité de dispersion du substrat hydrophobe (méthyloléate) au sein du milieu aqueux ne semble pas avoir d’impact sur l’efficacité du procédé, la levure sécrétant un biosurfactant permettant de stabiliser la dispersion. Les fluctuations en pH ont également peu d’impact sur le rendement de production de lipase, mais des observations au microscope ont révélé un début de dimorphisme cellulaire. Cette observation démontre la complexité de la réponse du système biologique face aux conditions de procédé. L’impact des fluctuations en oxygène dissous sur l’activité du gène lip2 a été confirmé par des analyses plus poussées en PCR quantitative (RT-qPCR). La deuxième partie du travail a donc été focalisée sur l’optimisation du transfert d’oxygène. Cette optimisation n’est pas triviale si on considère le phénomène de formation de mousse important lorsque la dispersion G-L au sein du réacteur est trop fine. Deux stratégies antimousse ont donc été envisagées : l’une mettant en œuvre l’ajout d’antimousse chimique et l’autre l’emploi d’un briseur de mousse mécanique. Cette dernière méthode s’est révélée inefficace du fait de la formation d’une couche de mousse persistante entre la surface du liquide et la turbine du briseur de mousse. Des analyses en cytométrie en flux ont permis d’observer un phénomène de dimorphisme qui semble lié au passage des cellules microbiennes au travers de cette couche de mousse, ce qui diminue le rendement en lipase. L’ajout d’antimousse chimique a donc été retenu et le transfert d’oxygène a pu être optimisé en fonction de contraintes de formation de mousse en considérant un enrichissement progressif de l’air d’entrée en oxygène pur. La dernière partie du travail a consisté à estimer l’extrapolation du procédé en prenant en compte à la fois les contraintes physico-chimiques du système (optimisation du transfert d’oxygène et limitation de la formation de mousse), ainsi que les contraintes biologiques. Cette extrapolation a tout d’abord été estimée au niveau de réacteurs scale-down permettant de reproduire les défauts d’écoulement généralement rencontrés au niveau industriel. De manière surprenante, cette étude a démontré que suite à l’adaptation physiologique des micro-organismes aux conditions d’écoulement, les problèmes de formation de mousse étaient de moins en moins marqués au cours de la montée en échelle du procédé. Cette observation va à l’encontre des calculs du génie chimique qui prédisent une augmentation du volume de mousse généré suite à la montée en volume des bioréacteurs et a été validée au niveau d’un bioréacteur pilote de 500L. Cela nous mène à conclure que la présence d’hétérogénéités au sein du volume réactionnel ne doit pas forcément être considérée comme un facteur négatif et pourrait au contraire être exploitée afin d’améliorer les performances des procédés et le design des bioréacteurs. [less ▲]

Detailed reference viewed: 100 (25 ULg)
Full Text
See detailStructuration de la diversité génétique du genre Milicia: taxonomie, phylogéographie, dynamique des populations
Daïnou, Kasso ULg

Doctoral thesis (2012)

Characterizing population genetic structure using phylogeographic approach contributes to understanding of evolutionary processes that affect plant populations. The present study investigated how past ... [more ▼]

Characterizing population genetic structure using phylogeographic approach contributes to understanding of evolutionary processes that affect plant populations. The present study investigated how past environmental variations can shape the spatial genetic diversity of an African timber tree species, Milicia excelsa (Welw) C.C. Berg. Given that plant responses to disturbances are closely linked to life history traits, this research also aimed to describe relationships between the reproductive traits of M. excelsa and its population genetic structure. Phylogeographic analyses were performed throughout the range of M. excelsa using nuclear and chloroplastic markers. Ecological characterization was conducted for a single population located in south-East Cameroon. Since M. excelsa is similar to the other species of its genus, M. regia (A. Chev) C.C. Berg, we first performed a morphogenetic comparison of these two taxa. The results confirmed an important morphological similarity between the two species with very rare discriminating criteria. In fact Bayesian assignment methods and reproductive isolation patterns suggest the occurrence of interspecific hybridization, which appeared to be unidirectional: hybrids displayed the M. regia morphotype. Because M. regia is known to be more adapted to humid tropical forests, one may expect it to occur in the Congo basin zone. However, its range is restricted to the western part of West Africa while M. excelsa occurs from Guinea-Conakry to Zimbabwe. Interestingly, in the case of M. excelsa, Central and West African specimens had no shared haplotype. This result was unexpected because long gene dispersal distances were found in Cameroonian populations, as expected from the behaviours of the main dispersal animals we identified, the bat Eidolon helvum and the parrots Psittacus erithacus and Agapornis swindernianus. In general, despite the likelihood for long distance seed dispersal, distinct genetic clusters were identified over West and Central Africa and their location may support the forest refugia hypothesis. In addition a phylogeographical signal was detected in chloroplast DNA indicating a prolonged separation between West and Central Africa populations with an accumulation of new mutations. At a smaller spatial scale, patterns of genetic structure also seemed to be weakly influenced by divergent reproduction times among sympatric individuals. The level of genetic diversity in the study populations falls within the range of values calculated for other tropical tree species. If phylogeography helps to infer population history, it also requires ecological or biological information to confirm some uncertainties. Such detailed data were often lacking to completely interpret numerous of our results. The present study raised new questions and led to new perspectives for further investigation both in phylogeography and botany. [less ▲]

Detailed reference viewed: 148 (36 ULg)
Full Text
See detailEtude de l'autofloculation dans un Chenal Algal à Haut Rendement (CAHR)
Baya, Dehenould Guy ULg

Doctoral thesis (2012)

Dans la technique du Chenal Algal à Haut Rendement (CAHR), l’effluent récupéré est très riche en microalgues. Les caractéristiques particulières de ce système (faible profondeur, faible temps de séjour ... [more ▼]

Dans la technique du Chenal Algal à Haut Rendement (CAHR), l’effluent récupéré est très riche en microalgues. Les caractéristiques particulières de ce système (faible profondeur, faible temps de séjour, agitation mécanique) combinées avec la présence d’ions inorganiques dans l’effluent sont les principaux éléments qui favorisent le développement intensif d’algues. Le rejet d’un tel effluent sans récupération préalable des microalgues est nuisible aux ressources biologiques terrestres et aquatiques et, plus généralement à l’ensemble des écosystèmes naturels. Par ailleurs, les microalgues peuvent être valorisées à des fins alimentaires ou d’extraction de sous-produits à valeur ajoutée. De plus, la récupération de la biomasse algale permettrait la réutilisation possible de la fraction liquide en irrigation notamment. Dans ce contexte, la récolte de la biomasse algale issue du CAHR constitue un enjeu majeur. Cependant, la petite taille des microalgues, la faible densité et les concentrations limitées rencontrées dans le CAHR comparées à celles de bioréacteurs industriels soulèvent un problème de rentabilité économique pour leur récupération en raison des énormes volumes d’eau à traiter. Les techniques usuelles de récupération de ces biomasses (en particulier par centrifugation) ont des coûts prohibitifs vis-à-vis de la valeur des produits récupérés. Dans ce cadre l’autofloculation qui est définie comme la formation et le rassemblement spontané de microalgues se présente comme une alternative aux problèmes rencontrés par les techniques conventionnelles de récupération des algues. C’est dans cette dynamique de recherche de s’inscrit cette thèse dont l’objectif est de déterminer les mécanismes impliqués dans l’autofloculation ainsi que les conditions optimales nécessaires à la réalisation de ce phénomène. Ce document est divisé en six grands chapitres : Les deux premiers chapitres sont consacrés à une revue des connaissances sur CAHR et la biomasse algale se développant dans ce système d’épuration. Également, un état de l’art concernant les méthodes de récolte de la biomasse algale notamment l’autofloculation est réalisé. Les simulations réalisées dans le chapitre III grâce à notre modèle thermodynamique de calcul de l’indice de saturation (IS) de différents composés mettent en évidence que les phosphates de calcium et formes substituées (Octacalcium phosphate, Ca4H(PO4)3; phosphate de calcium amorphe, Ca3(PO4)2; Hydroxyapatite, Ca5(PO4)3(OH); fluoroapatite, Ca5(PO4)3F et chloroapatite, Ca5(PO4)3Cl) sont les principaux composés inorganiques susceptibles d’être impliqués dans l’autofloculation. Le chapitre IV est consacré à la caractérisation des charges de surface, du potentiel zêta et des points isoélectriques de quelques phosphates de calcium et de la biomasse algale qui se développe dans le CAHR. Ces trois caractéristiques ont été déterminées respectivement par titrage colloïdal, par la méthode électrophorétique et par la méthode de Park et Regalbuto (1995) (détermination du pH d’équilibre à charge élevée). Cette étude a permis de conclure que la neutralisation des charges de surface des algues par les phosphates de calcium est probablement un moteur de l’autofloculation. Dans le chapitre V, des essais d’autofloculation simulée sur une biomasse provenant du CAHR et d’un milieu de culture ont été réalisés. Cette étude a essentiellement porté sur la détermination des concentrations optimales en ions calciums et orthophosphates, mais également sur la détermination des rapports de masse et de charge optimum entre les phosphates de calcium et algues pour une floculation maximale de la biomasse. Les résultats obtenus démontrent que les rendements d’autofloculation simulée sont très sensibles aux variations des concentrations en Ca2+ et PO43- et qu’il est indispensable de déterminer les concentrations optimales en ions calciums et orthophosphates pour obtenir les rendements maximums. En outre, les résultats permettent également de conclure que la neutralisation des charges des algues par les phosphates de calcium (purs ou substitués) se fait avec une stœchiométrie 1:1. Les doses de floculant nécessaires sont donc liées à la charge et peuvent être déterminées a priori sur cette base. Enfin, le chapitre VI porte sur le suivi expérimental de l’évolution de la biomasse algale dans une installation pilote et une installation réelle de traitement d’effluents par culture de microalgues installées au campus d’Arlon (eaux usées synthétiques) et Marrakech (eaux usées domestiques prétraitées). Les paramètres physiques, chimiques et biologiques ont été investigués, suivant les variations des conditions du milieu. Les résultats obtenus démontrent que l’installation de l’autofloculation entraine une déstabilisation du CAHR et une réduction de l’activité photosynthétique des algues. Ainsi, nous avons à notre disposition pour une eau de composition donnée, les outils pour prévoir la quantité d’algues qui pourra être récupérée sans ajouts de réactifs, encore faut il pouvoir gérer le réacteur pour atteindre ces conditions dans un délai court. [less ▲]

Detailed reference viewed: 101 (16 ULg)
Full Text
See detailIsolation and identification of antioxidant phytochemicals from Cuban species of the genera Erythroxylum P. Browne and Pluchea Cass
Perera Cordova, Wilmer ULg

Doctoral thesis (2012)

Phytochemicals showing antioxidant properties are largely recognized as beneficial to human health and disease prevention. Cuba is well known for having a rich flora with a high percentage of endemic ... [more ▼]

Phytochemicals showing antioxidant properties are largely recognized as beneficial to human health and disease prevention. Cuba is well known for having a rich flora with a high percentage of endemic species; it is considered as an interesting source of plant species for searching bioactive metabolites. Polar and non-polar extracts were prepared by fractionation from macerations in ethanol: H2O (7:3 v/v) from several Cuban plant species. The antioxidant capacity and the concentration in phenolic compounds were assayed in these extracts. The native species Pluchea carolinensis (Jacq.) G. Don., Pluchea odorata (L.) Cass. and Pluchea rosea Godfrey were identified as the most promising sources of antioxidants. The n-butanol extracts obtained by reflux from endemic Erythroxylum alaternifolium A. Rich. var. alaternifolium, var. parvifolium and suborbiculare also displayed high antioxidant capacity and high levels in phenolic compounds. The antioxidant capacity and the phenolic content of hydroalcoholic macerations from leaves, inflorescences, stems and roots of species of the genus Pluchea were also compared. Leaf extracts followed by inflorescence extracts showed the highest values of antioxidant capacity. The species P. carolinensis was used as a model to evaluate the antioxidant capacity in two locations and two phenological stages and also for monitoring the antioxidant capacity over some months. Natural adult specimens presented a higher phenolic content, as well as higher antioxidant capacity than young and cultivated specimens. Maximal antioxidant capacity and concentrations in phenolics were recorded in January, September and December; over the blooming stage (March), the antioxidant capacity was minimal. Two different solvents of extraction and two methods were also screened for extracting the maximal concentrations in antioxidants. Hydroalcoholic extractions showed higher antioxidant capacity than ethanolic ones. However, no difference in antioxidant capacity were measured between the two methods of extraction. The antioxidant capacity of P. carolinensis was also measured in leaves of plantlets micro-propagated on three different in vitro culture media and it was compared with leaves of young specimens grown ex-vitro. The inclusion of a cytokinin in culture media increased the antioxidant capacity of the leaf extracts of plantlets grown in vitro. However, the antioxidant capacity of plantlets grown in vitro was lower than that of young specimens grown ex-vitro. Additionally, several phenolic compounds were isolated from the species studied. Two flavonol glycosides were isolated from n-butanol leaf extract of Erythroxylum alaternifolium var. alaternifolium. Moreover, 22 phenolic compounds (including 9 phenolic acids and 13 flavonoids) were also identified from leaf, inflorescence and stem extracts of the three Pluchea species. All of them are reported for the first time in Cuban Pluchea species. In addition, rosmarinic acid, ferulic acid, quercetagetin, herbacetin, quercitrin, eupalitin and 3-methyl-quercetagetin were described for the first time in the genus Pluchea. The antioxidant capacity of each of these compounds was evaluated. The results suggested that most of these phytochemicals have an important contribution to the antioxidant capacity found in plant extracts. [less ▲]

Detailed reference viewed: 156 (10 ULg)
Full Text
See detailEtude des mécanismes cellulaires et moléculaires à l'origine du phénomène des DOMS (Delayed-Onset Muscle Soreness) consécutif à l'exercice excentrique.
Hody, Stéphanie ULg

Doctoral thesis (2012)

Tous, nous avons déjà ressenti diverses sensations de courbatures après avoir réalisé un exercice musculaire intense et/ou inhabituel. Ces douleurs musculaires d’apparition retardée et d’intensité ... [more ▼]

Tous, nous avons déjà ressenti diverses sensations de courbatures après avoir réalisé un exercice musculaire intense et/ou inhabituel. Ces douleurs musculaires d’apparition retardée et d’intensité variable sont désignées scientifiquement par l’acronyme « DOMS » pour « Delayed-Onset Muscle Soreness ». Le rôle particulier du mode de contraction excentrique dans la survenue des DOMS est largement accepté. Rappelons que l’exercice excentrique est caractérisé par l’association paradoxale des phénomènes opposés d’allongement musculo-tendineux et de développement tensionnel. Dès lors, les contraintes mécaniques accompagnant les contractions excentriques peuvent entraîner diverses altérations de l’ultrastructure musculaire qui se manifestent par une série de symptômes cliniques rendant les DOMS invalidants sur le plan fonctionnel. Or, le caractère discriminant de l’évaluation excentrique et l’efficacité rééducative de l’exercice excentrique dans plusieurs types de pathologies de l’appareil locomoteur ont formellement été démontrées. Dans ces conditions et bien qu’elles disparaissent spontanément après quelques jours de récupération, les DOMS retardent fréquemment la mise en route de programmes de réadaptation ou d’entraînement sportif. Actuellement, à l’analyse de la littérature, on ne peut que constater l’absence de solution thérapeutique susceptible d’atténuer significativement l’intensité des DOMS et de leurs conséquences fonctionnelles associées. Paradoxalement, l’exercice excentrique lui-même, lorsqu’il est proposé en conditions sous-maximales progressivement intensifiées, semble constituer la seule prévention réellement efficace, capable de prévenir l’apparition des DOMS. Malgré la littérature abondante consacrée à la description du phénomène des DOMS, aucune théorie unifiée n’est actuellement disponible pour expliquer la survenue différée des sensations douloureuses et les signes associés. L’efficacité d’un entraînement spécifique dans la prévention des DOMS a été confirmée par de nombreux travaux mais la nature de cet effet protecteur reste sujette à conjectures. Ce travail vise à une meilleure connaissance des mécanismes cellulaires et moléculaires impliqués dans le phénomène des DOMS survenant après la réalisation d’un exercice excentrique. Au cours de ce travail, nous avons donc tenté de contribuer à répondre aux questions suivantes : (1) Quels sont les corrélats biochimiques correspondants à l’apparition des DOMS suite à l’exécution d’exercices excentriques ? (2) Quels sont les mécanismes responsables de la variabilité interindividuelle des réponses à l’exercice excentrique ? (3) Quelles sont les adaptations induites par l’entraînement excentrique permettant de prévenir l’apparition des DOMS ? L’originalité de notre travail réside dans la mise au point d’un protocole expérimental chez l’humain associant la provocation de DOMS au moyen d’un dynamomètre isocinétique, le prélèvement de tissus musculaires humains par biopsie à l’aiguille et l’analyse protéomique comparative de ceux-ci par la méthode du 2D-DIGE. Nos travaux suggèrent qu’une plus grande sensibilité aux microlésions induites par l’exercice excentrique s’expliquerait par une prédominance de fibres rapides de type glycolytique et qu’un entraînement excentrique visant à prévenir les DOMS induirait une transition des fibres rapides de type glycolytique vers des fibres plus oxydatives. Le modèle humain, utilisé dans ce travail, nous a également permis de définir des indices de fatigue permettant de prédire l’ampleur de la réponse de la CK et de suggérer l’existence d’un effet protecteur controlatéral. Toutefois, les limites de l’expérimentation humaine ne nous permettent pas d’envisager une « manipulation » du système expérimental. Si on veut dépasser le stade expérimental d’observation encore possible chez l’humain et aborder le stade de stimulation et/ou d’invalidation par exemple, le recours à un modèle animal s’impose de lui-même. [less ▲]

Detailed reference viewed: 41 (14 ULg)
Full Text
See detailTotal Electron Content reconstruction using triple frequency GNSS signals
Spits, Justine ULg

Doctoral thesis (2012)

Nowadays, Global Navigation Satellite System (GNSS) provide accurate three dimensional positioning and navigation anywhere and anytime on the Earth’s surface and are being utilized in numerous civilian ... [more ▼]

Nowadays, Global Navigation Satellite System (GNSS) provide accurate three dimensional positioning and navigation anywhere and anytime on the Earth’s surface and are being utilized in numerous civilian and military applications. The US Global Positioning System (GPS) is currently being modernized to transmit radio signals on an additional third frequency, while the European Galileo is a newly developed system which will transmit on three civil frequency bands. One of the major error sources affecting GNSS is the delay caused when the signals pass through the ionosphere on their way to the Earth’s surface. This delay is inversely proportional to the square of the carrier frequency, and directly proportional to the Total Electron Content (TEC) of the ionosphere. In the last 20 years, several techniques using dual frequency GNSS measurements have been developed to estimate the TEC. With these techniques, systematic errors are confined to at least - 2.5 and 2.5 TECU for a mid-latitude site, and to at least - 5.5 and 5 TECU for a low-latitude location. In the last decades, knowledge about the ionosphere has grown considerably thanks to the use of GNSS measurements, and in turn the GNSS have highly benefited from this improved knowledge. Nowadays the availability of triple frequency GNSS signals enables the development of new processing techniques. We have therefore dedicated this work to developing a TEC reconstruction methodology based on triple frequency GNSS measurements and aimed at improving the accuracy of the final TEC values with regards to existing techniques. The structure of this study is as follows. Firstly, we provide information about GNSS, focusing on concepts, definitions and assumptions which will be used throughout this study. Then, we introduce the concepts of ionospheric propagation of radio signals and give a review of the literature on existing techniques used to extract the TEC with dual frequency GNSS measurements. We further present the complete design of the triple frequency TEC reconstruction methodology. We start by giving the set of combinations which allows us to resolve the original integer ambiguities, then we address the principles of TEC reconstruction, and finally we give an accuracy assessment of the computed TEC values. We also present an innovative technique to calibrate the satellite and receiver code hardware delays. We continue with testing the features developed on a simulated GPS and Galileo observation dataset, as well as on a real GIOVE observation dataset. Finally, we conclude this work by providing a critical overview of our investigations and suggesting various improvements of the current limitations. [less ▲]

Detailed reference viewed: 138 (7 ULg)
Full Text
See detailIdentification of Pythium species inducing common bean (Phaseolus vulgaris L.) root rot symptoms and development of backcrosses to improve the level of varietal resistance to this disease
Nzungize Rusagara, John ULg

Doctoral thesis (2012)

The common bean (Phaseolus vulgaris L.) is the most important food legume grown worldwide. It is a prioritary crop in various countries of East Africa and is grown mainly by small farmers for home ... [more ▼]

The common bean (Phaseolus vulgaris L.) is the most important food legume grown worldwide. It is a prioritary crop in various countries of East Africa and is grown mainly by small farmers for home consumption, the excess being sold in markets. Important yield losses of common bean induced by root rot diseases have been identified in several countries in East Africa including Rwanda. This is partly explained by the intensification of the cultivation of beans, the absence of rotations, the practice of continuous cultivation of this legume, and decline in soil fertility. Although bean root rot symptoms are caused by a number of soil borne pathogens depending on environmental conditions, Pythium spp. are the fungal pathogens most frequently associated with severe epidemics in eastern Africa. Studies on root rot have indicated that continuous cropping of beans, a common practice in eastern Africa, exacerbates the problem. This work was undertaken to improve the varietal resistance of common bean to limit the damages caused by Pythium in Rwanda. An analysis of the diversity of Pythium species associated with root rot was conducted through collect of samples of common bean plants throughout the country and through the characterization of the Pythium species causing root rot. The collected samples were used to isolate 96 typical Pythium colonies which were classified into 16 Pythium species according to their respective molecular sequences of the ribosomal ITS fragments. Molecular characterization using the ITS-DNA sequences was also carried out on samples isolated on infected beans roots. The study of the distribution of each species identified within the samples analyzed, revealed that Pythium vexans is the most widespread taxon in the different common bean producing areas in Rwanda. Pathogenicity tests of the 16 identified Pythium species were performed on a set of 10 common bean varieties. The results showed that all identified Pythium species were pathogenic to common bean: they all induce symptoms of root rot under controlled conditions. However, the common bean varieties used in this investigation showed differences in their reaction to inoculation with the 16 Pythium species. At the end of this work of the characterization of Pythium species isolated in Rwanda, a scheme for improving varietal resistance has been implemented. It is based on a backcross protocol assisted by molecular marker (PYAA 19800). Recurrent parents are composed of three common bean varieties traditionally grown in Rwanda while the two donor parents are a resistant variety of the Mesoamerican gene pool and a resistant variety of Andean pool. The progeny obtained after the backcrossing program was subjected to the pathogenicity trials by inoculating with a strain of Pythium ultimum in controlled conditions in order to verify the effectiveness of this improvement protocol. These trials have shown that in the offspring all the individuals showing the presence of the marker gene were also resistant to Pythium with very low levels of severity at the end of inoculation tests. [less ▲]

Detailed reference viewed: 101 (7 ULg)
Full Text
See detailGouverner la maternité au Bénin. Les difficiles conditions d'application des politiques sanitaires dans le territoire de la Pendjari
Sambiéni, N'Koué Emmanuel ULg

Doctoral thesis (2012)

La Zone Sanitaire de Tanguiéta, partie intégrante du système de santé au Bénin, expérimente, depuis la décentralisation de ce système, la gestion autonome de l’offre de soins de santé moderne dans toutes ... [more ▼]

La Zone Sanitaire de Tanguiéta, partie intégrante du système de santé au Bénin, expérimente, depuis la décentralisation de ce système, la gestion autonome de l’offre de soins de santé moderne dans toutes ses dimensions. Elle est particulièrement ingénieuse dans la production d’initiatives de soins au profit des mères engagées dans l’enfantement, avec le soutien de l’Etat et des partenaires du secteur de la santé. Cet engagement est justifié officiellement par la situation critique des indicateurs de Santé Maternelle traduisant une morbidité et une mortalité élevées. La ZST est tout d’abord un espace socioculturel d’une particularité remarquable, comparée au reste du pays, du fait même de sa position géographique, de son identité culturelle pendjarienne et de son histoire sociopolitique. C’est de son identité socioculturelle et sociopolitique qu’elle revendique son autonomie technico-administrative dans la fourniture des soins de santé. La curiosité intellectuelle de cette recherche socioanthropologique est de comprendre comment la demande et les soins aux femmes qui « veulent donner la vie » sont véritablement « structurés » et « gouvernés » dans cet espace socioculturel et médical. « Habitus maternel » et « gouvernementalité» sont utilisés à la fois comme concepts et comme postures méthodologiques et épistémologiques afin de décrypter et d’analyser « l’ordre » et « le progrès » dans ces logiques et pratiques obstétricales. Suivant une méthodologie essentiellement qualitative, la recherche a duré quatre ans, avec une longue présence sur le terrain, consistant en des observations dans les maternités et dans les familles ainsi que des entretiens avec les différents acteurs participant aux soins. Cette recherche nous apprend que dans l’ordre traditionnel, l’enfantement a été historiquement et socialement géré par des institutions laissant une place assez faible à l’expression de l’individu, qu’il soit le père ou la mère de l’enfant en construction bio-sociale. A l’heure actuelle, les maternités modernes ont toujours du mal à prendre le pas sur ces institutions dans le contrôle des soins avant, pendant et après l’accouchement. Malheureusement, affaiblies par les différentes influences sociales, ces institutions apparaissent socialement et techniquement incapables de contenir et de régler le mal de la grossesse et de l’accouchement. La maternité, tant dans son état traditionnel que moderne, demeure encore morbide et mortelle. L’Etat et ses institutions d’encadrement et d’offre de soins maternels, peu connectés aux réalités socioculturelles, s’avèrent constamment dépendants des agences des Nations Unies et des autres partenaires privés, producteurs de stratégies le plus souvent d’ordre idéologique et militant. La Stratégie Nationale de Réduction de la Mortalité Maternelle et Néonatale et l’Initiative Femme pour Femme, respectivement élaborées au Ministère de la Santé et au niveau de la Zone Sanitaire, révèlent le rendez-vous manqué dans la rencontre programmée entre usagers des maternités et offre de soins dans la planification sanitaire. La maternité, avec ses multiples acteurs en négociation permanente sans consensus, est conflictuelle et souvent détournée de sa mission. Elle empile régulièrement des stratégies tout en chassant constamment ses premiers bénéficiaires et en mettant les enjeux sanitaires en arrière-plan. Pour une « Maternité Sans Risques » dans les espaces traditionnel et moderne, il faudra chercher et comprendre comment, dans la nébuleuse des institutions qui les gèrent dans ces deux registres, les femmes peuvent renforcer leurs positions légitimes dans la négociation pour l’orientation des soins obstétricaux essentiels et d’urgence. Il conviendra enfin d’étudier les conditions pour une lecture effective du risque obstétrical dans l’environnement social des femmes. [less ▲]

Detailed reference viewed: 53 (1 ULg)
Full Text
See detailMachine learning-based feature ranking: Statistical interpretation and gene network inference
Huynh-Thu, Vân Anh ULg

Doctoral thesis (2012)

Machine learning techniques, and in particular supervised learning methods, are nowadays widely used in bioinformatics. Two prominent applications that we target specifically in this thesis are biomarker ... [more ▼]

Machine learning techniques, and in particular supervised learning methods, are nowadays widely used in bioinformatics. Two prominent applications that we target specifically in this thesis are biomarker discovery and regulatory network inference. These two problems are commonly addressed through the use of feature ranking methods that order the input features of a supervised learning problem from the most to the less relevant for predicting the output. This thesis presents, on the one hand, methodological contributions around machine learning-based feature ranking techniques and on the other hand, more applicative contributions on gene regulatory network inference. Our methodological contributions focus on the problem of selecting truly relevant features from machine learning-based feature rankings. Unlike the p-values returned by univariate tests, relevance scores derived from machine learning techniques to rank the features are usually not statistically interpretable. This lack of interpretability makes the identification of the truly relevant features among the top-ranked ones a very difficult task and hence prevents the wide adoption of these methods by practitioners. Our first contribution in this field concerns a procedure, based on permutation tests, that estimates for each subset of top-ranked features the probability for that subset to contain at least one irrelevant feature (called CER for "conditional error rate"). As a second contribution, we performed a large-scale evaluation of several, existing or novel, procedures, including our CER method, that all replace the original relevance scores with measures that can be interpreted in a statistical way. These procedures, which were assessed on several artificial and real datasets, differ greatly in terms of computing times and the tradeoff they achieve in terms of false positives and false negatives. Our experiments also clearly highlight that using model performance as a criterion for feature selection is often counter-productive. The problem of gene regulatory network inference can be formulated as several feature selection problems, each one aiming at discovering the regulators of one target gene. Within this family of methods, we developed the GENIE3 algorithm that exploits feature rankings derived from tree-based ensemble methods to infer gene networks from steady-state gene expression data. In a second step, we derived two extensions of GENIE3 that aim to infer regulatory networks from other types of data. The first extension exploits expression data provided by time course experiments, while the second extension is related to genetical genomics datasets, which contain expression data together with information about genetic markers. GENIE3 was best performer in the DREAM4 In Silico Multifactorial challenge in 2009 and in the DREAM5 Network Inference challenge in 2010, and its extensions perform very well compared to other methods on several artificial datasets. [less ▲]

Detailed reference viewed: 413 (39 ULg)
Full Text
See detailDynamique associative et réduction de la pauvreté rurale: une étude comparative de villages inégalement couverts par des Organisations Non Gouvernementales dans la province du Bandundu et dans l’hinterland de Kinshasa.
Nganda Afumba, Jean Pierre ULg

Doctoral thesis (2012)

Comme bon nombre de pays en développement, la République Démocratique du Congo observe, depuis le début des années 90, un développement sans précédent du mouvement associatif, particulièrement des ... [more ▼]

Comme bon nombre de pays en développement, la République Démocratique du Congo observe, depuis le début des années 90, un développement sans précédent du mouvement associatif, particulièrement des organisations non gouvernementales de développement. Dans un environnement où les pouvoirs publics sont quasi inexistants, ces dernières sont considérées par certains comme des instruments efficaces de réduction de la pauvreté, et par d’autres comme des opportunistes évoluant aux dépens de la misère des gens. La présente recherche se propose de faire une étude comparative entre, d’une part, des ménages de deux villages de l’hinterland de Kinshasa largement couverts par des ONG, et d’autre part, des ménages de deux autres villages dans le Bandundu ne bénéficiant d’aucune intervention d’ONG. Cette étude a pour but la compréhension, l’analyse et l’appréciation empirique de la pertinence de la stratégie de développement et de réduction de la pauvreté rurale orientée vers la promotion des organisations associatives du type ONG, et in fine suggère un outil susceptible d’améliorer les interventions visant la réduction de la pauvreté rurale. [less ▲]

Detailed reference viewed: 125 (22 ULg)
Full Text
See detailContribution à l’identification de l’agent étiologique de l’entéropathie épizootique du lapin
Huybens, Nathalie ULg

Doctoral thesis (2012)

Epizootic rabbit enteropathy (ERE) is a pathology of the digestive system inducing economic loss in rabbit husbandry throughout Europe. The aetiological agent is unknown at the present time but a ... [more ▼]

Epizootic rabbit enteropathy (ERE) is a pathology of the digestive system inducing economic loss in rabbit husbandry throughout Europe. The aetiological agent is unknown at the present time but a reference inoculum (TEC4) reproduces the pathology. This inoculum contains an extremely rich bacterial flora. Several methods were used to reduce this bacterial flora while retaining virulence: centrifugation on discontinuous sucrose gradient, cellular adherence and treatment with chloroform/ethanol, antibiotics and an acid buffer. The flora of the obtained fractions were analyzed using traditional bacteriological techniques: identification of cultivable species, counting of colony forming units (CFU) and direct bacterioscopic exam after Gram coloration. Then, molecular biology was used to compare inocula, fractions and negative control. Three methods were used to find sequences present in virulent inocula and absent from non virulent inocula and negative controls. Twenty-two restriction enzymes were used to compare the 16SrDNA restriction profile (Amplified Ribosomal DNA Restriction Analysis or ARDRA). Hypervariable regions V3 and V6 to V8 were studied by Denaturating Gradient Gel Electrophoresis (DGGE). Finally, Random Amplification of Polymorphic DNA (RAPD) was used on the inocula, fractions and negative controls. Only the RAPD allow the obtainment of sequences specific to virulent inoculum. Unfortunately, a study on field samples did not confirm the link between the sequences and ERE. For one of the two identified sequences, a bacterial strain carrier was isolated. The strain was inoculated into rabbits but no clinical signs of ERE were observed. Samples of stools, blood and serum were collected during an experimental ERE infection. The evolution of fecal bacterial flora was studied using DGGE to follow the evolution of flora over the course of the disease. Unfortunately, neither specific bands nor specific band patterns appeared to be linked to the disease. Seven bacterial species were detected in the blood samples of three inoculated rabbits at day two post inoculation, confirming the hypothesis that bacteriemia occurs early on ERE infection. Finally, six fractions were analysed by pyrosequencing of the 16SrDNA gene. The aim was to find one or several species present in the virulent inocula but absent or less numerous in the nonvirulent inocula and control. The richness and diversity of all the inocula is equal or superior to human feces. As expected, the flora identified by pyrosequencing was different from the cultivable flora. However, no genera or species was specifically linked to the virulent inocula. The resolution of this technique was inadequate to identify the aetiological agent of ERE. A higher number of samples and sequences could at best restrain the identification to one genus. [less ▲]

Detailed reference viewed: 34 (5 ULg)
Full Text
See detailEssays on the complex relationships between Innovation and Performance in service firms, with particular reference to financial services: An intellectual capital perspective
Mention, Anne-Laure ULg

Doctoral thesis (2012)

Service sector firms have long been neglected in innovation studies despite their increasing importance for economy. However, recent research has revealed that service firms do innovate although they ... [more ▼]

Service sector firms have long been neglected in innovation studies despite their increasing importance for economy. However, recent research has revealed that service firms do innovate although they follow distinct paths and reach different outcomes than those of the manufacturing sector. Measuring the effects of innovation on performance has thus become an essential concern for both policy‐makers and business leaders. This dissertation specifically contributes to the current debate on the effects of innovation on performance at firm‐level in the service sector by shedding more light on the characteristics of these complex relationships and by defining its underlying mechanisms. For these purposes, an intellectual capital perspective is adopted. This dissertation first takes a broad sector approach to services, focusing on potentially innovative core service activities, and relying on the concept of relational capital, it explores the most commonly reported feature of innovation in services, which is the openness of the innovation process. As prior research indicates that there is a diversity of innovation patterns in services, the dissertation then concentrates on financial service firms. Besides their own significance, financial firms play a critical role in the proper functioning of the entire economy. Focusing on this specific industry, the dissertation further delineates the innovation process into its constitutive elements, referring to human, structural and relational capital concepts. The setting for most of the empirical studies is Luxembourg, which allows benefitting from the peculiarities of this small, open, international but highly innovative economy dominated by service firms. This dissertation mainly concludes that adopting an open strategy for innovation activities brings differentiated results according to the partners involved, with some contrast observed between market, science and competitor co‐operation. When examining how resources mobilized in the innovation process interact to affect performance in financial services, the dominant role of relational capital emerges. Furthermore, the examination unveils the interaction effects between the constitutive elements of intellectual capital and confirms the importance of the orientation towards innovation, in its various facets, in financial firms. Overall, this dissertation shows that adopting an intellectual capital perspective to understand the innovation process, to reveal its main ingredients and to disentangle its effects on performance can be insightful. [less ▲]

Detailed reference viewed: 36 (7 ULg)
Full Text
See detailPracticing local culture as a vehicle of integration? Creative collaborations and Brussels’ Zinneke Parade.
Costanzo, Joseph ULg

Doctoral thesis (2012)

Immigrant integration, and socio-economic cohesion more broadly, continue to be top priorities at many levels of governance in Europe and are long-standing fixtures of scholarly, political and public ... [more ▼]

Immigrant integration, and socio-economic cohesion more broadly, continue to be top priorities at many levels of governance in Europe and are long-standing fixtures of scholarly, political and public debate across Europe and North America. Although integration and culture have been dominant themes in contemporary European and American social science and humanities literatures, their intersections—particularly involving immigrant participation in local arts and cultural activities—remain understudied. Through the use of mixed-methods research, my doctoral thesis addresses how participating in such creative activities serves as a vehicle for integration. This topic is examined within the context of the European capital city-region of Brussels, and provokes further inquiry into the role of place in integration and identity-making particularly within a context in which there is no universal or normative local identity. With the onsite support of local experts, artistic and cultural actors and the public at large, I examine the ‘creative collaboration’ of Zinneke Parade 2010—a biennial socio-cultural and urban project with origins in the Brussels 2000 European Capital of Culture Programme (ECoC). Though politicians and community organizers frequently cite Zinneke as an exemplary project of the Brussels-Capital Region, to date, no formal study has been conducted neither into its role in bridging many of the city’s socio-linguistic, spatial and economic divides nor into its role as a source for building local networks, social, cultural, economic or otherwise. Finally, this work is unique in its treatment of migrant and ethnic minority identity representations in an explicitly non-ethno-cultural event. In its biennial parade, Zinneke purposefully does not re-present separate ethno-cultural pasts, but instead reflects the identities of collective and creative efforts of today’s local Bruxellois. Fielded throughout 2010 and early 2011, in-depth interviews, combined with short as well as detailed questionnaires, form the basis of data which I have collected to answer the question: Does practicing local culture facilitate integration? [less ▲]

Detailed reference viewed: 141 (4 ULg)
Full Text
See detailAssessing the impacts of technical and structure choices on groundwater model performance using a complex synthetic case
Wildemeersch, Samuel ULg

Doctoral thesis (2012)

According to the European Water Framework Directive (2000/60/EC) and the specific Groundwater Directive (2006/188/EC), Member States have to manage groundwater at the groundwater body scale and in an ... [more ▼]

According to the European Water Framework Directive (2000/60/EC) and the specific Groundwater Directive (2006/188/EC), Member States have to manage groundwater at the groundwater body scale and in an integrated way. Given the objectives of “good quantitative and qualitative status” of groundwater for 2015 stated by the Directive, end-users want to know the quantitative and qualitative evolution of groundwater for several scenarios. Physically-based and spatially-distributed groundwater flow and transport models constitute useful management tools in this context since they take explicitely into account the heterogeneity and the physical processes occuring in the subsurface for predicting system responses to future stress factors. However, at such a scale, groundwater flow and transport modelling is challenging due to (1) the complexity of geological and hydrogeological contexts, (2) the uneven level of characterisation knowledge, and (3) the representativity of measured parameters. Furthermore, such models require long execution times. As a consequence, a series of choices and simplifications are made for dealing with these issues. Therefore, the outstanding question is to know whether endusers’expectations can be met in spite of such choices and simplifications. This work focuses on choices and simplifications related to spatial discretisation and saturation–pressure relations in the unsaturated one. The influence of stress factor time resolution is also tested. Considering this general context, the objective of the present work is to evaluate the influence of some model technical (spatial discretisation) and structure (saturation–pressure relations) uncertainties on model results, parameter sensitivities, and optimisation performance in order to provide guidelines for model development. This is performed using a synthetic case inspired by typical groundwater bodies of Wallonia (Belgium). This synthetic case is used for obtaining reference observations in terms of flow rates and hydraulic heads. These reference observations are then compared with their simulated equivalent produced by simplified models differing by their spatial discretisation, their saturation–pressure relations in the unsaturated zone, or the time resolution of their stress factors. The simplified models are then ranked using several performance criteria measuring the discrepancies between reference observations and their simulated equivalent. This ranking leads to guidelines for large-scale groundwater flow model development with respect to typical end-users’ expectations. Whatever the time resolution of stress factors, the quantitative and qualitative analyses performed indicate that coarsening horizontal spatial discretisation deteriorates mainly the simulation of flow rates, coarsening vertical spatial discretisation deteriorates mainly the simulation of hydraulic heads, and (over)simplifying saturation–pressure relations in the unsaturated zone significantly impair the simulation of both flow rates and hydraulic heads. Although optimisation can compensate for errors induced by model technical and structure uncertainties, the improvement of model fit is limited, especially for the coarsest models. Furthermore, with respect to end-users’ expectations, the weighted least-square objective function is not always the most relevant criteria for optimising models. Therefore, it is essential to use specific performance criteria for evaluating model performance depending on the objectives of the study. The ideal would be to develop an end-users objective function for including such performance criteria in the optimisation process and stop the optimisation process once performance criteria would have reached the values specified by the end-users with respect to the objectives of the study. [less ▲]

Detailed reference viewed: 78 (26 ULg)
Full Text
See detailIdentification d'effecteurs de la signalisation Delta/Notch dans la différenciation des cellules endocrines du système digestif
Flasse, Lydie ULg

Doctoral thesis (2012)

Les cellules endocrines du système digestif incluent les cellules pancréatiques, regroupées en ilots de Langherhans et les cellules entéroendocrines, disséminées tout le long de l’épithélium du tube ... [more ▼]

Les cellules endocrines du système digestif incluent les cellules pancréatiques, regroupées en ilots de Langherhans et les cellules entéroendocrines, disséminées tout le long de l’épithélium du tube digestif. Un disfonctionnement de ces cellules peut être à l’origine de graves maladies, en conséquence les cellules endocrine du tractus digestif font l’objet de nombreuses études. Une connaissance précise du mode de fonctionnement mais aussi du développement et de la différenciation de ces cellules est requise afin de pouvoir élaborer de nouveaux traitements. Bien que ces deux populations de cellules endocrines soient situées dans des organes distincts, elles présentent de nombreuses similarités. Ces similitudes se retrouvent au niveau des hormones produites mais également au niveau des facteurs de transcription et des voies de signalisation impliquées dans le développement de ces cellules. La signalisation Notch joue un rôle primordial dans le contrôle de la différenciation des cellules endocrines pancréatiques et intestinales, chez la souris et le zebrafish. L’objectif de ce travail consiste à mieux comprendre les étapes précoces de la différenciation endocrine en recherchant des effecteurs de type ARP/ASCL de la voie de signalisation Delta/Notch, impliqués dans le développement endocrine du tractus digestif. Dans le pancréas, nous montrons que le facteur ascl1b est le premier marqueur pancréatique endocrine à apparaître. Ce facteur qui appartient à la famille des ASCL, est requis pour initier la différenciation de la lignée endocrine. Le facteur neurod1, appartenant à la famille des ARP, agit plus tardivement dans le développement de cette lignée afin de permettre le maintien du programme de différenciation endocrine. Nous démontrons que ces deux facteurs agissent séquentiellement dans les précurseurs endocrines pour promouvoir leur différenciation. La perte simultanée de ces deux facteurs conduit à l’absence totale de cellules endocrine. Dans le tractus gastro-intestinal, nous montrons que la signalisation Delta/Notch réprime le destin sécréteur en inhibant l’expression du facteur ascl1a. La présence de ce facteur est absolument requise pour la différenciation de l’ensemble des cellules sécrétrice. ascl1a est à la base de la cascade de facteur de transcription contrôlant la différenciation des cellules entéroendocrines. Nous montrons également que, dans cet organe, neurod1 régule la différenciation de certains types de cellules entéroendocrines. Parallèlement à cette étude des facteurs ARP/ASCL, nous avons mis en évidence la fonction d’un nouveau régulateur de la différenciation endocrine pancréatique: rfx6. Ce facteur est exclusivement exprimé dans la lignée endocrine chez le zebrafish. En l’absence de rfx6, les précurseurs endocrine sont bloqués dans leur différenciation et s’accumulent. Ce facteur est donc requis pour la différenciation terminale des précurseurs endocrines. [less ▲]

Detailed reference viewed: 52 (14 ULg)
Full Text
See detailReal-time Simultaneous Modelling and Tracking of Articulated Objects
Declercq, Arnaud ULg

Doctoral thesis (2012)

In terms of capability, there is still a huge gap between the human visual system and existing computer vision algorithms. To achieve results of su cient quality, these algorithms are generally extremely ... [more ▼]

In terms of capability, there is still a huge gap between the human visual system and existing computer vision algorithms. To achieve results of su cient quality, these algorithms are generally extremely specialised in the task they have been designed for. All the knowledge available during their implementation is used to bias the output result and/or facilitate the initialisation of the system. This leads to increased robustness but a lower reusability of the code. In most cases, it also majorly limits the freedom of the user by constraining him to a limited set of possible interactions. In this thesis, we propose to go in the opposite direction by developing a general framework capable of both tracking and learning objects as complex as articulated objects. The robustness will be achieved by using one task to assist the other. The method should be completely unsupervised with no prior knowledge about the appearance or shape of the objects encountered (although, we decided to focus on rigid and articulated objects). With this framework, we hope to provide directions for a more di cult and distant goal: that of completely eliminating the time consuming prior design of object models in computer vision applications. This long term target will allow the reduction of the time and cost of implementing computer vision applications. It will also provide a larger freedom in the range of objects that can be used by the program. Our research focuses on three main aspects of this framework. The rst one is to create an object description e ective on a wide variety of complex objects and able to assist the object tracking while being learnt. The second is to provide both tracking and learning methods that can be executed simultaneously in real-time. This is particularly challenging for tracking when a large number of features are involved. Finally, our most challenging task and the core of this thesis, is to design robust tracking and learning solutions able to assist each other without creating counter-productive bias when one of them fails. [less ▲]

Detailed reference viewed: 20 (6 ULg)
Full Text
See detailExperimental and Numerical Investigations of the Aeroelastic Stability of Bluff Structures
Andrianne, Thomas ULg

Doctoral thesis (2012)

The study of the dynamic interactions between the wind and civil engineering structures has become increasingly important over the last few decades. Most of these structures are aerodynamically "bluff ... [more ▼]

The study of the dynamic interactions between the wind and civil engineering structures has become increasingly important over the last few decades. Most of these structures are aerodynamically "bluff" and are becoming more flexible. Bluff-body aeroelasticity is a very challenging research area due to the unsteadiness and nonlinearity of the aerodynamic loading. This thesis presents the investigation of three aeroelastic phenomena affecting bluff-bodies: Vortex Induced Vibration (VIV), Galloping and Torsional Flutter. For each instability, extensive experimental studies are carried out in the wind tunnel. Innovative analysis, based on the Common-base Proper Orthogonal Decomposition (CPOD) method is used to study the flow visualization data. The VIV phenomenon is studied on a flexible tube with a circular cross-section, supported from its midpoint. A CPOD-based input-output model is developed to describe the system. The galloping instability is studied on a generic bridge section. A complete analysis of the aeroelastic behaviour of the structure is presented and a new polynomial empirical model is developed, which reflects accurately the nonlinear nature of the system. The torsional flutter phenomenon is extensively studied for two different structures: a generic bridge deck and a rectangular cylinder. The Motion Induced Vortex is identified as the fundamental cause of this aeroelastic phenomenon, on the basis of the analysis of the flow around the oscillating rectangle. In addition, it is demonstrated that the quasi-steady theory is not adapted to estimate the onset velocity of torsional flutter. Finally, a 2D aeroelastic simulation code, based on the Discrete Vortex Method (DVM) is developed. The non-linear aerodynamics around the body are well reproduced, allowing the simulation of all the aeroelastic instabilities investigated experimentally. [less ▲]

Detailed reference viewed: 204 (65 ULg)
Full Text
See detailSpatial and temporal responses of marine gastropods and biofilms to urban wastewater pollution in a Mediterranean coastal area
Vermeulen, Simon ULg

Doctoral thesis (2012)

The increasing human pressure exerted along coastlines and the subsequent increase in the delivery of pollutants at sea is a matter of concern worldwide. Urban wastewaters contain a variety of pollutants ... [more ▼]

The increasing human pressure exerted along coastlines and the subsequent increase in the delivery of pollutants at sea is a matter of concern worldwide. Urban wastewaters contain a variety of pollutants (mainly N, P, and trace elements) which can be involved in the launching of eutrophication. This complex process is able to fundamentally alter the integrity of coastal ecosystems thereby impairing the sustainability of economic activities and involving health risks for human through the consumption of sea products. Eutrophication is considered for more than 40 years as a pervasive process and a priority issue for the preservation of the health status of coastal ecosystems. The Mediterranean Sea supports high economic pressures in relation with the continuously increasing number of inhabitants and tourists in coastal areas. The physico-chemical (e.g. oligotrophy, microtidal regime) features of waters make them sensitive to eutrophication and several heavily urbanized areas have been experiencing adverse effects of this process for decades (e.g. biodiversity losses, Harmful Algal Blooms, fishes’ kills,…etc). Nowadays, smaller localities discharging insufficiently treated or raw wastewaters at sea also begin to report eutrophication problems especially during summer months when the number of tourists considerably increases the resident populations. National monitoring programs generally focus on priority areas by using either toxicological (e.g. trace metals in molluscs) and / or structural (e.g. phytoplankton biomasses) parameters to follow the evolution of already impacted water bodies. However, if the most deleterious effects of eutrophication are well known, little information is actually available regarding the early symptoms of the process. The identification of time- and cost-efficient indicators along with analytical procedures that would deliver early warning signals of pollution is therefore required to assist local authorities in the implementation of environmental policies. This research aimed at implementing some easy-to-use and efficient tools to detect the impact of urban wastewater pollution in Mediterranean coastal areas. A new set of potential early bioindicators has been identified. The gastropods Patella caerulea and Monodonta turbinata inhabiting the Mediterranean rocky midlittoral zone and epilithic biofilms were selected as good candidates for monitoring purpose. Biofilms which are microbenthic communities mainly composed of microalgae have been used for decades in freshwater systems as early indicators of pollution. In contrast, marine biofilms have largely been neglected and little is known regarding their composition, their physiology, and the way they react to wastewater pollution. We focused our studies on the Calvi Bay (NW Mediterranean, France) which is, regarding the anthropogenic pressure exerted on its coastal fringe, representative of other moderately urbanized areas of the Mediterranean basin. The Calvi Bay area is indeed among the preferred summer destinations by tourists in Corsica and is influenced by a single point source of pollution which is secondary-treated urban wastewater. A control vs. impacted sites approach has been used to assess the responses of the selected bioindicators to wastewater pollution. Our first task was to characterize the nature and amounts of the main pollutants (nutrients, trace elements) discharged in the Calvi Bay. Since nutrient measurements are commonly used to infer into the trophic status of water bodies, we assessed whether this parameter was reliable to detect the influence of wastewater discharge in the study area. The main pollutants discharged at sea were ammonium, phosphorus and iron. Amounts considerably increased during summer months (July and August) which was related to the high frequentation of the Calvi Bay area by tourists. Measurements of nutrient concentrations in seawater samples from controls and impacted sites did not allow evidencing the influence of wastewater inputs. In contrast, the high spatial and temporal resolution achieved through a small scale sampling design conducted in a small harbour impacted by wastewater discharges showed large spatial variability in the dispersion of effluents and hourly variations in the amounts of pollutants. The extrapolation of these results at the scale of the Calvi Bay may have explained our failure to detect the pollution by using samples collected punctually in space and time. These results suggested that the use of bioindicators that integrate the variable influence of nutrient pulses was required to evidence pollution. We focused our second study on a toxicological approach to detect the bioavailability of anthropogenically-derived nutrients in the midlittoral zone of the Calvi Bay and of the Marseille harbour. Multi-spatial scales and seasonal dual C and N stable isotope analyses were performed on the limpet Patella caerulea, the snail Monodonta turbinata, epilithic biofilms, and the macroalga Rissoella verruculosa. All bioindicators exhibited strongly elevated δ15N values at impacted sites compared to pristine ones, which revealed the influence of wastewater pollution in the midlittoral zone and the biological availability of anthropogenically-derived nitrogen at the base of the food web. Gastropods provided a time-integrated response reflecting the control vs. impacted status of sites. Results indicated that one sampling campaign per year should be sufficient to evidence wastewater pollution likely because of the slow turnover rate of gastropods’ muscles. Macroalgae showed a reliable but less consistent signal of wastewater pollution compared to other indicators. Only epilithic biofilms tended to show the occurrence of nutrient pulses during the tourist season which suggested that wastewater discharges may have influenced the composition and / or the physiology of communities. However the sampling of biofilms developed on natural rocky substrates was destructive and did not allow investigating the fine biological structure of communities and thus to fully understand the output of community scale parameters such as stable isotopes. We therefore recommended using biofilms grown on artificial substrates to circumvent this problem. We then allowed biofilms to develop on glass slides which are the most currently used artificial substrates in freshwater systems. Our task was to find out the most suitable technique to isolate and identify benthic diatoms which are common colonizers on newly available substrates. The species-specific tolerance to pollution of diatoms has been used for decades in the assessment of the health status of freshwater bodies. However, little is known on their marine counterparts and on their ability to evidence wastewater pollution. A specific and time-cost-efficient technique was implemented for the processing of lightly silicified benthic marine diatoms from Mediterranean oligotrophic areas. This was achieved through the multiple comparisons of existing protocols used either in sea- or fresh-waters. We finally investigated, by means of mesocosm deployed in situ and field experiments, the responses of biofilms developed on glass slides to a range of urban wastewater exposures. Colonization experiments lasted for 24 days in summer conditions. A multi-parametric assessment was conducted using a combination of toxicological and structural approaches applied to different biological scales. Toxicological parameters such as C-N stable isotopes, C:N:P ratios, and Trace Elements were measured at the community scale while the structural parameters were considered at the community (standing crops), assemblage (densities of the main autotroph and heterotroph organisms), and the genus (diatoms) scales. The mesocosm experiments were highly efficient to demonstrate the good potential of biofilms as early indicators of wastewater pollution. The impact of wastewater pollution was mainly identified at the community and the genus (diatoms) scales. Standing crops and the C-N stable isotopes were the most useful parameters showing respectively a stimulation of microalgal biomasses (i.e. eutrophication) and the bioavailability of wastewater-derived nitrogen even at low pollution levels. At the genus scale, the composition of diatoms’ assemblages changed markedly especially in the most polluted mesocosms. Results notably highlighted the proliferation of the small-sized individuals of Entomoneis which was thought to outcompete the larger diatoms belonging to the genus Mastogloia for nutrient uptake. The responses of biofilms to pollution largely differed between mesocosm and field experiments. Nevertheless, standing crop parameters corroborated results obtained in mesocosms allowing to assume an influence of wastewater pollution in the Calvi Bay. Field samples were generally characterized by the presence of well developed hydrozoan colonies which were only seldom reported at mesocosm sites. The presumably impacted site also exhibited the highest densities in other heterotrophic eukaryote groups (e.g. nematodes, polychaetes, foraminifers) and primary producers. We interpreted these results either as a top-down effect or as an increase in habitat complexity. The genus scale determination of diatoms’ assemblages showed a decrease in the relative abundances of Mastogloia at the impacted site which was in accordance with results from the mesocosm experiments. The highest density values were also observed for Cylindrotheca at impacted site. The last part of this research gathers the multiple spatial and temporal responses provided by the selected bioindicators to urban wastewater pollution in order to validate their future routine use in the context of monitoring programs. The occurrence of potential confusion sources in the interpretation of data was critically reviewed. The time-cost-efficiency of the tested parameters was then evaluated in order to assist environmental managers in their choices of biofilm-based techniques for detecting wastewater pollution. Finally since biofilms exhibited some strong accumulations of toxic elements, ecological hypotheses dealing with the trophic role of biofilms and the transfer of pollutants through the food webs are provided. [less ▲]

Detailed reference viewed: 149 (31 ULg)
Full Text
See detailNumerical schemes for tracer studies in shallow shelf seas
Mercier, Christophe ULg

Doctoral thesis (2012)

Nowadays, tracers have revealed to be an invaluable integrated tool to investigate the different thematics related to coastal areas, shallow shelf seas or estuaries. In this work, they are used in ... [more ▼]

Nowadays, tracers have revealed to be an invaluable integrated tool to investigate the different thematics related to coastal areas, shallow shelf seas or estuaries. In this work, they are used in combination with a parallel scalable Fortran90 implementation of a 3D hydrodynamic model to study the transport of mud within the Belgian Coastal Zone. The results obtained illustrate the need for tools to understand the interactions between such highly energetic coastal areas and the sediment dynamics. The Constituent Age and Residence time Theory (CART), originally applied to passive tracers, is therefore extended to describe the sediments and used to quantify their rates of resuspension and horizontal transport. This application reveals some numerical issues that may degrade the reliability of the results. The different numerical parameterizations are thus revisited starting with the use of advection schemes, and especially, the Total Variation Diminishing (TVD) schemes built along the line defined by Harten. It is shown that the blind application of the usual TVD schemes and associated flux limiters can lead to non-TVD solutions when applied to complex geometries. Spatial and/or temporal variations of the bathymetry can indeed break the TVD property. Hopefully, really TVD schemes can be recovered by taking these variations into account in the formulation of the flux limiters. Even if its Eulerian formulation eases the implementation of CART into existing models, it is shown that CART's computation procedure lacks a numerical framework for a robust application. To address this, we enforce the consistency, defined as the requirement that the integration scheme does not introduce errors in the age field when aging is the only active process. Unfortunately, this does not guarantee the absence of overshootings. While it does not seem feasible to ensure a TVD behavior of the age field, appropriate modifications of the flux/slope limiters are derived here to prevent the occurrence of age values outside the physically acceptable range. On the bases of the solutions obtained after the advection of any numbers of tracers using high-order non-linear schemes, several control or global variables can be built. Even if the independent advection schemes used are specifically built to produce profiles free from the numerical artifacts that can spoil the physical meaning of the results, such global/control variables can exhibit these unwanted behaviors. This problematic is firstly treated with regard to the TVD schemes built from Harten's theorem. But guaranteeing the TVD property is not always feasible. Alternatively, appropriate modifications of the flux/slope limiters are implemented here to enforce a maximum principle for any global/control variable built as first-order homographic function of its components. [less ▲]

Detailed reference viewed: 49 (17 ULg)
Full Text
See detailRole of NF-κB p65 subunit phosphorylation by ATM in DNA damage-regulated gene expression
Sabatel, Hélène ULg

Doctoral thesis (2012)

DNA damage, induced by several genotoxic agents, challenge genome integrity. Among the different types of DNA lesions, DNA double-strand breaks (DSB) are the most deleterious. Indeed, if not correctly ... [more ▼]

DNA damage, induced by several genotoxic agents, challenge genome integrity. Among the different types of DNA lesions, DNA double-strand breaks (DSB) are the most deleterious. Indeed, if not correctly repaired, they can lead to cell death or carcinogenesis. Upon DSB, cells activate a complex signaling network, the DNA damage response (DDR), to counteract those threats. The DDR coordinates DSB repair, checkpoint activation, apoptosis and transcription factors regulation, including NF-κB.   NF-κB family is composed of 5 proteins (RelA/p65, RelB, c-Rel, p105/p50 and p100/p52) which assemble in dimers to form active NF-κB transcription factor. In resting cells, NF-κB complexes are bound to inhibitor proteins such as IκBα, and maintained inactive in the cytoplasm. Classical NF-κB activation requires activation of IκB kinase (IKK) complex, which phosphorylates IκBα, finally leading to its degradation. NF-κB transcription factor is then free to translocate to the nucleus where it regulates a wide array of target genes. NF-κB is an important regulator of diverse cellular processes, including immune response, inflammation, cell survival, proliferation, differentiation, adhesion and apoptosis. NF-κB activation is associated to several pathogenesis and especially contributes to the growth and malignancy of cancer cells. NF-κB also affects the tumor response to many types of chemotherapy and ionizing radiation. Therefore the understanding of the regulation mechanisms of this transcription factor represent a major concern.   This work was interested in the regulation mechanism of DSB-induced NF-κB via the direct phosphorylation of the NF-κB subunit p65 by ATM kinase, the main mediator protein of the DDR. Indeed, rapidly activated in response to DSB, this kinase phosporylates a huge amount of substrates involved in different cellular functions. It had been previously shown that ATM was required for DSB-induced NF-κB activation by acting at two levels. On the one hand, activated ATM phosphorylates the IKK regulatory subunit NEMO. On the other hand, ATM is important for TAK1 activation and TRAF6 poly-ubiquitination, two steps necessary for full IKK complex activation too. The present work therefore highlighted a third ATM-mediated NF-κB regulation mechanism. This study showed that following DNA damage, the phosphorylation of p65 on Ser547 by ATM lead to the lower expression of a set of specific genes mainly involved in inflammation. Phosphorylated p65 was shown to interact with the co-repressor HDAC1, leading to specific promoter deacetylation and subsequent decreased gene expression.   In a second time, we also showed for the first time the requirement of MDC1 protein in DNA damage-induced NF-κB activation. MDC1 protein is mainly described as playing an important role in DSB-induced nuclear foci, which consist in large protein structures that assemble at the site of the DSB. Nevertheless, it appeared in this study that the role of MDC1 in NF-κB activation pathway is foci-independent. [less ▲]

Detailed reference viewed: 83 (38 ULg)
Full Text
See detailDiversity and endemism of Murinae rodents in Thai limestone karsts: a genetic approach
Latinne, Alice ULg

Doctoral thesis (2012)

Limestone karsts are characterized by an important species richness and high levels of endemic species of plants, vertebrates and invertebrates adapted to this extreme environment. However, in Southeast ... [more ▼]

Limestone karsts are characterized by an important species richness and high levels of endemic species of plants, vertebrates and invertebrates adapted to this extreme environment. However, in Southeast Asia, karst ecosystems suffer from a considerable lack of scientific data and remain widely unknown despite their high biological importance. Combining field investigations with phylogeographic and phylogenetic analyses based on several kinds of molecular markers, this thesis aims at exploring the diversity and endemism of Murinae rodents in limestone karsts of Thailand. Thai limestone karsts host two endemic Murinae rodent species, Leopoldamys neilli and Niviventer hinpoon. This thesis reveals that L. neilli is more largely distributed in Thailand than indicated by previous records available in the literature. The species has been recorded in numerous limestone karsts of Thailand with the exception of its peninsular area. L. neilli has also been discovered in central Laos. Moreover our niche modeling study indicates that large tracts of suitable habitat for this species may also occur in several regions of Indochina. L. neilli populations are highly fragmented and a deep genealogical divergence among its lineages is observed. Both mitochondrial and nuclear markers support a large-scale population structure of four main groups (west, centre, north and northeast) and a strong finer structure within each of these groups. These results indicate that L. neilli populations are isolated on karsts such as on islands and that migrations among them are reduced. Our findings also suggest that the current phylogeographic pattern of this species results from the fragmentation of a widespread ancestral population and that vicariance has played a significant role in the evolutionary history of L. neilli. These deep vicariant events that occurred during Plio-Pleistocene are related to the formation of the Central Plain of Thailand. Moreover, the western populations of L. neilli are genetically and morphologically highly divergent from the other populations and could represent a separate species. This strong phylogeographic pattern is not observed for other Murinae species with lower levels of ecological specialization such as Leopoldamys edwardsi and Rattus tanezumi. Finally, this thesis provides preliminary information about the diet of L. neilli and indicates that plants of the Solanaceae family constitute an important part of its diet. The phylogeographic structure of N. hinpoon is not similar to the one of L. neilli. In contrast to L. neilli, N. hinpoon is confined to central Thailand and mitochondrial markers used in this study indicated that this species is genetically homogenous and characterized by a single mitochondrial lineage. Valuable data to refine the conservation status of L. neilli and N. hinpoon, two species currently listed as Data Deficient on the IUCN Red List have been gathered during this study. Three main threats to the long-term subsistence of L. neilli have been identified: (1) the high fragmentation of its population, (2) the large-scale destruction of limestone karsts in Southeast Asia, and (3) the intense trapping of this species for human consumption in northeastern Thailand. Therefore we propose to consider L. neilli as “Near threatened” on the IUCN Red List. However, if the western lineage of L. neilli represents a separate species, it should be listed as “Vulnerable”. Due to its small distribution range and the high threats that its habitat is facing in central Thailand, N. hinpoon would also be qualified as “Vulnerable” on the IUCN Red List. In addition to karst endemic species, this thesis reveals that Thai limestone karsts host high levels of Murinae rodent diversity. A sequence-based species delimitation method completed by the analysis of the level of genetic divergence was used to define species boundaries within our rodent samples collected in limestone karsts. A total of 12 described Murinae species, corresponding to 17 putative species based on our genetic criteria, were encountered in limestone karsts of Thailand. Most of these species are associated to forest ecosystems. Therefore this study suggests that limestone karsts could play a key role in the preservation of the rodent biodiversity by providing refuges for the forest-dwelling Murinae rodents in deforested regions. An important cryptic diversity has been detected within the traditionally recognized species Maxomys surifer and Berylmys bowersi. They could be considered as species complex and require further taxonomic work. The potential distribution of Leopoldamys edwardsi and Leopoldamys sabanus, two species also distributed in Thailand, has been investigated using niche modeling techniques. The predicted distribution ranges of these two species suggest a clear geographical separation between them, with the potential distribution of L. edwardsi being limited to the northern part of Indochina while L. sabanus is mainly distributed in the Sundaic region. Our findings also suggest that these two species could have survived in large areas of Southeast Asia during Quaternary ice ages without large scale extinction and that no drastic modification of the distribution of these species will occur in the future due to climate changes. In conclusion, using various genetic approaches, this work gains important insights into the Murinae rodent diversity of Thai limestone karsts and represents the first detailed study of karst endemic rodent species in Southeast Asia. [less ▲]

Detailed reference viewed: 84 (11 ULg)
Full Text
See detailExperimental study of the hydraulic behaviour of Piano Key Weirs
Machiels, Olivier ULg

Doctoral thesis (2012)

Detailed reference viewed: 94 (26 ULg)
Full Text
See detailModélisation régionale des écoulements souterrains et du transport de nitrates dans le bassin de la Dyle amont
Cesar, Emilie ULg

Master's dissertation (2012)

Les objectifs principaux de cette étude visaient à, d’une part, recalibrer le modèle hydrogéologique d’écoulement préexistant du bassin de la Dyle amont en distribuant spatialement la recharge et, d’autre ... [more ▼]

Les objectifs principaux de cette étude visaient à, d’une part, recalibrer le modèle hydrogéologique d’écoulement préexistant du bassin de la Dyle amont en distribuant spatialement la recharge et, d’autre part, étudier la pollution diffuse en nitrates en considérant un flux massique associé aux eaux d’infiltration variant spatialement. Le modèle WetSpass a été utilisé pour calculer la recharge moyenne annuelle distribuée sur le bassin. La technique HFEMC implémentée dans code SUFT3D a été utilisée pour modéliser les écoulements souterrains et le transport de nitrates. La modélisation du transport de nitrates dans les eaux souterraines a été effectuée en considérant plusieurs scénarios simplifiés d’intrants, de 1950 à 2010. L’approche classique de détermination des écoulements a été combinée à la technique des « mixing cells » pour modéliser le transport de solutés. Ce travail a démontré la faisabilité de l’association, à l’échelle du bassin de la Dyle amont, du modèle WetSpass et du code SUFT3D pour la modélisation des écoulements souterrains et du transport de nitrates. [less ▲]

Detailed reference viewed: 73 (10 ULg)
Full Text
See detailEtude de l’implication du microARN miR-146a dans
Halkein, Julie ULg

Doctoral thesis (2012)

La cardiomyopathie du péripartum (PPCM) est une maladie mortelle qui touche certaines femmes entre le dernier mois de la grossesse et jusqu’à 5 mois après l’accouchement. Ces femmes présentent des ... [more ▼]

La cardiomyopathie du péripartum (PPCM) est une maladie mortelle qui touche certaines femmes entre le dernier mois de la grossesse et jusqu’à 5 mois après l’accouchement. Ces femmes présentent des symptômes d’hypertension et un dysfonctionnemment du ventricule gauche. A la fois l’endothélium et les cardiomyocytes sont affectés dans le cœur des patientes atteintes de la PPCM et il a été récemment montré que le fragment de 16 kDa de la prolactine (PRL 16K) était un facteur majeur dans la pathophysiologie de la maladie. Dans notre laboratoire, nous travaillons depuis des années sur les mécanismes d’action de la PRL 16K. Nous nous intéressons également aux microARN (miARN), ces régulateurs de l’expression des gènes décrits pour être impliqués dans la plupart des processus physiologiques et pathologiques tels que l’angiogenèse ou les maladies cardiovasculaires. Ils sont également décrits depuis peu pour pouvoir être sécrétés par une cellule productrice et transférés à une cellule receveuse, via des microvésicules, afin d’y jouer un rôle. Au cours de ce travail, nous avons mis en évidence que la PRL 16K est capable d’induire l’expression de miR-146a au sein des cellules endothéliales via l’activation de NF-B et d’induire son transfert via des microvésicules appelées exosomes. Ces exosomes endothéliaux sont capable d’interagir avec les cardiomyocytes et le contenu en miR-146a y est transféré. Au sein des cellules endothéliales, miR-146a possède des propriétés anti-angiogènes. Il réprime la prolifération et favorise l’apoptose des cellules endothéliales. Parmi ses gènes cibles potentiels, nous validons NRAS via lequel miR-146a pourrait médier une partie de ses effets. Au sein des cardiomyocytes, nous avons mis en évidence un rôle de miR-146a dans la répression du métabolisme corrélé à une diminution de l’expression d’ErbB4. Nous avons ensuite montré le rôle central tenu par miR-146a dans un modèle murin de souris développant la PPCM. On retrouve dans le cœur de ces souris un niveau augmenté de miR-146a et un niveau diminué d’ErbB4 et de NRAS. De plus, l’inhibition de miR-146a dans ces souris PPCM, via l’injection d’oligonucléotides anti-sens, permet de restaurer le phénotype sain des souris PPCM. On observe une restauration de l’activité cardiaque ainsi qu’une normalisation des niveaux d’expression de miR-146a et de ses gènes cibles. Chez la femme présentant une PPCM, les niveaux cardiaques de miR-146a et d’ErbB4 sont également dérégulés. Ces résultats suggèrent que miR-146a tient un rôle central dans la pathophysiologie de la PPCM et permet d’expliquer la dualité d’action de la PRL 16K sur les cellules endothéliales et les cardiomyocytes. Enfin, les miARN extracellulaires présents dans le plasma constituent des biomarqueurs de choix pour le diagnostic d’un grand nombre de pathologies. Ainsi, nous avons mis en évidence un niveau d’expression plasmatique significativement plus élevé chez les patientes atteintes d’une PPCM comparé à celui de femmes saines ainsi que de patientes présentant également de l’insuffisance cardiaque dû à une cardiomyopathie dilatée. En conclusion, en plus d’être un facteur impliqué de façon centrale dans la pathophysiologie de la PPCM et constituant dès lors une cible thérapeutique intéressante, miR-146a permet un diagnostic spécifique de la maladie. [less ▲]

Detailed reference viewed: 79 (4 ULg)
Full Text
See detailIntérêt du broutage des haies et bandes boisées pour les bovins sur parcours en Wallonie
Vandermeulen, Sophie ULg

Master's dissertation (2012)

The establishment of agri-environmental measures in Wallonia promotes hedges and woody strips planting in the agricultural landscape. This study aimed at evaluating the influence of trees and shrubs ... [more ▼]

The establishment of agri-environmental measures in Wallonia promotes hedges and woody strips planting in the agricultural landscape. This study aimed at evaluating the influence of trees and shrubs access on the feeding behaviour of grazing heifers and determining the feeding value of woody species. The second objective was to assess the anti-parasitical effect of these ligneous forages. For 4 consecutive weeks from April to May 2012, 12 dairy heifers were equally distributed among two different groups: one with an open access to a woody hedge (experimental group) and the other not (control group). The feeding behavior of heifers was recorded during days of 10 hours, in relation to the available herbaceous biomass. At the end of the experiment, a faeces analysis was used to assess the presence and the number of parasites infesting heifers. The leaves of 12 woody species harvested in late May 2012 were analyzed for their chemical composition and their in vitro ruminal fermentability using a gas test. The results were compared to those obtained for white clover and ryegrass. The feeding behavior of heifers was influenced by their access to woody species. Indeed, grazing time of control animals (59.8%) was superior to animals that could browse the hedge (54.8%). The experimental animals browsed the ligneous when the pasture herbaceous biomass was the lowest (0.22 kg DM/kgBW*ha), namely the second week of the experiment only. During this week, browsing time represented 3.72% of the time spent on pasture. Faeces parasites analysis showed a significantly lower infestation of trichostrongyles in experimental animals. The chemical composition and kinetic parameters of in vitro ruminal fermentation varied significantly among woody species. The CP content ranged from 14.3% in Viburnum opulus to 31.9% in Sambucus nigra. Fraxinus excelsior had a CP content of 24.5% and a maximum gas production of 120ml/gDM. These values were similar to the values obtained for ryegrass (26.4% CP and 132.2 ml /gDM). The highest maximum gas volume produced was reached for Populus nigra (135.5 ml /gDM) and was equivalent to ryegrass. In conclusion, in the grazing conditions in Wallonia, browsing can be considered as complementary feeding for cattle on pasture with hedges. Indeed, some woody species appear promising for livestock nutrition such as Sambucus nigra, Fraxinus excelsior or Populus nigra. This work is a preliminary study in the sylvopastoral area. Future studies should be explored to confirm the results obtained in this study and to deepen knowledge of this area. [less ▲]

Detailed reference viewed: 49 (17 ULg)
Full Text
See detailNarration et jeu vidéo. Pour une exploration des univers fictionnels
Barnabé, Fanny ULg

Master's dissertation (2012)

This dissertation is devoted to the study of the various terms through which the video game as a medium can build a narrative. First of all, it is quite relevant to note that traditional narratologic ... [more ▼]

This dissertation is devoted to the study of the various terms through which the video game as a medium can build a narrative. First of all, it is quite relevant to note that traditional narratologic tools are not suitable to describe every aspect of video game narrativity. Indeed, contrary to what some researchers say, this medium does not necessarily limits itself to imitating literature and cinema in order to build a narrative (which would therefore consist merely of texts and cutscenes): it is also able to convey narrative information through purely ludic elements (a setting can reveal the past of a character, the interface can or cannot be integrated into the fiction etc.). Moreover, these "narrativisation elements" (as named by Sébastien Genvo ) make sense only when they are activated i.e. acknowledged by the video game player: the gamer’s attitude is therefore a variable which is to be taken account in the study of video game narrative. However, if the video game narrative only exists in the form of potentiality possibly updatable by the player, how could we define precisely a corpus that would set apart narrative games from those radically devoid of narrative? With what tangible elements could we study an object that varies according to the receiver who activates it? The reflexion of this work shows that these methodological difficulties cannot be solved thanks to the traditional narratology tools – unless distorting them until they become inoperative. The thesis sustained here consists of calling into question the validity of the notion of narrative (as a linear sequence of events) because this latter is neither able to render all the "narrativisation elements" nor the player’s influence on the narration. The notion of fiction world then stands in for the notion of narrative. This concept designates a particular form of narration, displayed on several dimensions and in which the linear narrative is one aspect among others. More precisely, the universe is divided into three key notions (borrowed from Etienne Armand Amato ): the cosmos, the diegesis and the ludiegesis. In order to test the effectiveness of this new conception of the narrative and to establish a first approach of the field through the new vision that it allows, this dissertation suggests to take an inventory and describe the main "narrativisation elements" that can occur in the construction of a diegesis. Forteen of these can be counted: the cutscenes, the texts, the avatar, the characters, the intertextual references, the paratext, the interface, the camera, the objects, the environment, the objectives, the sounds, the gameplay and the variations introduced by the player (the manipulation of the rules and the choices). The conception of the narration as a universe (i.e an arrangement of elements that the player has to organize into a hierarchy, and not a succession of events) permits to consider the possibility to "load" with narrative these different game levels and the consequences of this investment on the story which is vehicled this way. Moreover, this reformulation favors the acknowledgement of the player in the elaboration of the narrative, since it authorizes a new conception of the story, which no longer appears like a "whole to receive", but like an "area to explore". [less ▲]

Detailed reference viewed: 178 (29 ULg)
Full Text
See detailDéveloppement d’un procédé biotechnologique de production de molécules à note verte à partir de feuilles de betterave
Gigot, Cédric ULg

Doctoral thesis (2011)

La grande richesse des feuilles de betterave en 13-HPL (entre 10 et 12 UE1/g de poids frais), une enzyme produisant le (3Z)-hexénol, le (2E)-hexénal et le n-hexanal, fait de ce substrat un candidat ... [more ▼]

La grande richesse des feuilles de betterave en 13-HPL (entre 10 et 12 UE1/g de poids frais), une enzyme produisant le (3Z)-hexénol, le (2E)-hexénal et le n-hexanal, fait de ce substrat un candidat potentiel pour le développement d’un procédé biotechnologique de production d’arômes alimentaires. Maillon essentiel du système de défense des plantes, l’enzyme 13-HPL est inductible par des stimuli externes et son expression dépend de l’âge et de l’état physiologique de la plante. Au cours de ce travail, l’optimisation de l’expression de cette enzyme au sein du végétal a été étudiée préalablement au développement d’un procédé industriel visant à exploiter ce substrat. Ce procédé comprend successivement quatre opérations chimiques : une hydrolyse d’huile végétale riche en acides gras insaturés, une oxydation de ces acides, un clivage par les 13-HPLs et une purification des aldéhydes et des alcools synthétisés. Selon nos résultats, l’étape limitante de ce procédé est la synthèse d’aldéhydes qui présente, dans des conditions optimales de réaction, une capacité de production maximale de 0,502mM à l’échelle pilote (100L). L’inhibition suicide par le substrat et l’instabilité combinée de l’enzyme et de ces produits de réaction réduisent le taux de clivage des aldéhydes. La mise au point d’un système d’extraction des arômes volatils par flux gazeux et d’une alimentation fedbatch en substrat permet de réduire l’impact limitant de ces facteurs et d’accroître la capacité de production à 1,37mM. Afin de mieux comprendre les mécanismes réactionnels, l’enzyme 13-HPL de la betterave a été séquencée et clonée dans un vecteur procaryote permettant de disposer d’une source d’activité enzymatique indépendante des contraintes du milieu extérieur. L’utilisation de ces techniques a permis de développer un procédé bivalent (à la fois de source microbienne et végétale) de production d’arôme exploitable au sein de l’industrie alimentaire. [less ▲]

Detailed reference viewed: 95 (19 ULg)