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See detailFirst-principles study of ferroelectricity in oxide superlattices
Zhao, Jinzhu ULg

Doctoral thesis (2013)

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See detailDesign, performance analysis, and implementation of a positioning system for autonomous mobile robots
Pierlot, Vincent ULg

Doctoral thesis (2013)

Positioning is a fundamental issue in mobile robot applications, and it can be achieved in multiple ways. Among these methods, triangulation based on angle measurements is widely used, robust, and ... [more ▼]

Positioning is a fundamental issue in mobile robot applications, and it can be achieved in multiple ways. Among these methods, triangulation based on angle measurements is widely used, robust, and flexible. In this thesis, we present an original beacon-based angle measurement system, an original triangulation algorithm, and a calibration method, which are parts of an absolute robot positioning system in the 2D plane. Also, we develop a theoretical model, useful for evaluating the performance of our system. In the first part, we present the hardware system, named BeAMS, which introduces several innovations. A simple infrared receiver is the main sensor for the angle measurements, and the beacons are common infrared LEDs emitting an On-Off Keying signal containing the beacon ID. Furthermore, the system does not require an additional synchronization channel between the beacons and the robot. BeAMS introduces a new mechanism to measure angles: it detects a beacon when it enters and leaves an angular window. This allows the sensor to analyze the temporal evolution of the received signal inside the angular window. In our case, this feature is used to code the beacon ID. Then, a theoretical framework for a thorough performance analysis of BeAMS is provided. We establish the upper bound of the variance and its exact evolution as a function of the angular window. Finally, we validate our theory by means of simulated and experimental results. The second part of the thesis is concerned with triangulation algorithms. Most triangulation algorithms proposed so far have major limitations. For example, some of them need a particular beacon ordering, have blind spots, or only work within the triangle defined by the three beacons. More reliable methods exist, but they have an increasing complexity or they require to handle certain spatial arrangements separately. Therefore, we have designed our own triangulation algorithm, named ToTal, that natively works in the whole plane, and for any beacon ordering. We also provide a comprehensive comparison between other algorithms, and benchmarks show that our algorithm is faster and simpler than similar algorithms. In addition to its inherent efficiency, our algorithm provides a useful and unique reliability measure, assessable anywhere in the plane, which can be used to identify pathological cases, or as a validation gate in data fusion algorithms. Finally, in the last part, we concentrate on the biases that affect the angle measurements. We show that there are four sources of errors (or biases) resulting in inaccuracies in the computed positions. Then, we establish a model of these errors, and we propose a complete calibration procedure in order to reduce the final bias. Based on the results obtained with our calibration setup, the angular RMS error of BeAMS has been evaluated to 0.4 deg without calibration, and to 0.27 deg, after the calibration procedure. Even for the uncalibrated hardware, BeAMS has a better performance than other prototypes found in the literature and, when the system is calibrated, BeAMS is close to state of the art commercial systems. [less ▲]

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See detailDesign of sugar-based surface active agents for emulsion polymerization in supercritical carbon dioxide
Boyère, Cédric ULg

Doctoral thesis (2013)

The use of supercritical CO2 (scCO2) as alternative to traditional organic solvents and the valorization of biomass are interesting approaches to reduce the ecological footprint of chemical processes. On ... [more ▼]

The use of supercritical CO2 (scCO2) as alternative to traditional organic solvents and the valorization of biomass are interesting approaches to reduce the ecological footprint of chemical processes. On the other hand, emulsions offers many advantages over bulk and solution processes for polymerization reactions including limited environmental impact, ease of products recovery and increased reaction rate. In this context, this thesis aims to design novel fluorinated sugar-based surfactants able to stabilize water/CO2 (W/C) emulsion systems and explore their potential as template for polymerization reactions. Such surface active agents were prepared either by lipase-catalyzed esterification of mannose with fluorinated acid derivatives or following chemoenzymatic approaches involving very efficient and versatile "click" chemistries like the thiol-Michael addition or the thiol-ene/-yne reactions. The W/C interfacial activity of these novel glycosurfactants was confirmed by tensiometry as well as their ability to form stable W/C microemulsions. Then, we tested a range of these neutral fluorinated carbohydrate esters as stabilizers for the CO2-in-water (C/W) emulsion polymerization. In particular, the radical polymerization of acrylamide was performed in the continuous aqueous phase of a C/W high internal phase emulsion (HIPE) leading to highly interconnected macroporous polymer matrices, also called polyHIPEs. In this case, we emphasized a clear dependence of morphology of the porous structure with the concentration and the structure of the glycosurfactant. Thanks to the electrical neutrality of these fluorinated glycosurfactants which confers them a lower sensitivity to the ionic forces compared to their ionic counterparts, we could extend this system to the polymerization of ionic liquid monomers. Porous poly(ionic liquid)s were thus formed by emulsion polymerization for the first time and exhibit spherical cells interconnected by pores with size (~ 1 μm) among the lowest reported for polyHIPEs produced from C/W emulsions. The emulsion C/W templating methodology based on the designed fluorinated glycosurfactants thus appears as a technique of choice for the preparation of valuable macroporous polymer matrices. [less ▲]

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See detailScalar and fermionic extensions of the Standard Model
Degée, Audrey ULg

Doctoral thesis (2013)

In this thesis several aspects of beyond SM physics schemes have been treated. In particular, two categories of models have been considered: ($i$) models with extra Higgs ElectroWeak (EW) doublets (multi ... [more ▼]

In this thesis several aspects of beyond SM physics schemes have been treated. In particular, two categories of models have been considered: ($i$) models with extra Higgs ElectroWeak (EW) doublets (multi-Higgs-doublet models), ($ii$) models with new fermion EW singlets (type-I seesawmodels). In the first category, two problems associated with the most general two-Higgs-Doublet Model (2HDM) and with the three-Higgs-Doublet Model (3HDM) have been tackled. In the former case the scalar mass spectrum has been derived in a basis-invariant fashion whereas in the later, after introducing a general procedure for the minimization of highly symmetric potentials, the minimization of an $S_4$ and of an $A_4$ 3HDM has been analyzed. In the second category, the possibility of envisaging seesaw-like models yielding sizeable lepton-flavor-violating decay rates has been investigated. With the models at hand, the corresponding charged lepton-flavor-violating phenomenology has been studied focusing on rare muon decays, for which forthcoming lepton-flavor-violating experiments will be able to prove large parts of their parameter space. [less ▲]

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See detailAbsorbing Layers for Wave-Like Time-Dependent Problems - Design, Discretization and Optimization
Modave, Axel ULg

Doctoral thesis (2013)

The numerical simulation of wave-like phenomena occurring in large or infinite domains is a great challenge for a wide range of technological and scientifical problems. A classical way consists in ... [more ▼]

The numerical simulation of wave-like phenomena occurring in large or infinite domains is a great challenge for a wide range of technological and scientifical problems. A classical way consists in considering only a limited computational domain with an artificial boundary that requires a specific treatment. In this thesis, \textit{absorbing layers} are developed and studied for time-dependent problems in order to deal with such artificial boundary. A large part of this thesis is dedicated to the \textit{perfectly matched layers} (PMLs), which exhibit appealing properties. They are first studied in a fundamental case with non-dispersive linear scalar waves. A procedure for building PMLs is proposed for convex domains with regular boundary. It permits a great flexibility when choosing the shape of the computational domain. After, the issue of choosing PML parameters is addressed with the aim of optimizing the PML effectiveness in discrete contexts. The role of each parameter, including the so-called \textit{absorption function}, is highlighted by means of analytical and numerical results. A systematic comparison of different kinds of absorption functions is performed for several classical numerical schemes (based on finite differences, finite volumes or finite elements). Then, while the PMLs do not a priori account for incoming signals generated outside the computational domain, different problem formulations that account for such forcing are detailed and compared. The interest of the whole approach is finally illustrated with two- and three-dimensional numerical examples in electromagnetism and acoustics, using a discontinuous finite element scheme. In regional oceanic models, modeling open-sea boundaries brings new difficulties. Indeed, additional linear/nonlinear dynamics are involved and the external forcing is generally poorly known. In this context, different absorbing layers and the widely used Flather boundary condition are compared by means of classical benchmarks. The choice of the absorption function and the way of prescribing the external forcing are discussed in specific marine cases. [less ▲]

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See detailLes processus d'écologisation entre santé et environnement. Le cas de la maladie de Lyme
Massart, Clémence ULg

Doctoral thesis (2013)

La thèse vise à comprendre comment une diversité de définitions d’une maladie émergente et complexe, la Borréliose de Lyme, se construisent aujourd’hui dans un grand nombre de lieux. Ces définitions sont ... [more ▼]

La thèse vise à comprendre comment une diversité de définitions d’une maladie émergente et complexe, la Borréliose de Lyme, se construisent aujourd’hui dans un grand nombre de lieux. Ces définitions sont parfois concurrentes, parfois étrangères l’une à l’autre ; parfois médiatisées, parfois confinées dans des espaces discrets. Pour comprendre cette diversité, je mobilise le concept de pratique développé par Stengers (2006). J’ai accédé aux processus de connaissance mis en œuvre par les praticiens à travers les deux versants qui définissent une pratique : les obligations, qui renvoient à leur manière spécifique d’interroger l’objet ou l’être dont ils cherchent à apprendre quelque chose ; les exigences qui opèrent des exclusions et tracent des frontières entre pratiques. Cette grille d’analyse s’applique à des groupes de taille variable, professionnels ou non, mandatés ou pas par le politique, de même qu’aux vivants non-humains. La première partie situe la maladie de Lyme dans le champ des maladies et définit sa spécificité en regard des « maladies environnementales » qui ont pour cause les pollutions industrielles. En tant que maladie infectieuse ayant pour vecteur une tique et pour réservoir la faune sauvage, la maladie de Lyme présente davantage les traits d’une « maladie écologique » qui renouvelle l’attribution des responsabilités, les modes de gestion, la nature des entités incriminées ainsi que l’identité des praticiens impliqués. À partir de ce constat, j’ai fait l’hypothèse d’une « écologisation des problèmes sanitaires » : les problématiques environnementales s’immiscent dans d’autres secteurs. J’ai interrogé cette écologisation thématique à la lumière de « l’écologisation des pratiques » que Stengers définit comme un mode de relation entre pratiques qui remplace les exclusions par des coordinations pour produire des savoirs nouveaux, dynamiques et irréductibles à chaque pratique. La deuxième partie expose les pratiques de quatre groupes de praticiens : les malades chroniques qui échangent sur Internet, les infectiologues, les ticologues et les écologues généticiens des populations. L’analyse révèle l’existence de deux espaces de discussions marqués par des relations distinctes : dans le premier, médical, diagnostic et curatif, les définitions de la maladie s’opposent tandis qu’elles se chevauchent dans le second, environnemental, épidémiologique et préventif. Ces deux espaces entretiennent peu de relations entre eux. La troisième partie s’intéresse aux interractions entre praticiens. À travers un groupe de travail, un lieu, un concept et des techniques diagnostiques, j’interroge la rencontre effective entre pratiques environnementales et médicales. L’essentiel des collaborations entre acteurs environnementaux et médicaux portent sur la prévention de la maladie. Les savoirs écologiques, comme ceux des malades, ont pourtant un potentiel pour une autre élaboration du diagnostic de ces maladies. Cette analyse montre que des frictions apparaissent lorsque des praticiens interrogent un même vivant sur des modes différents. À l’inverse, une sympathie se manifeste entre praticiens dès lors qu’ils interrogent sur le même mode des vivants différents. Plus qu’une écologisation du sanitaire, la thèse met en évidence un processus de « sanitarisation de l’écologie ». En effet, ce sont les praticiens rattachés à l’écologie qui s’immiscent dans la thématique des « maladies infectieuses émergentes ». Les savoirs qu’ils produisent tendent à dépeindre un ensemble de maladies variables dans le corps et le milieu, qui rappelle la définition par les malades, sans que ces groupes de praticiens disposent à ce jour d’espace de rencontre. [less ▲]

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See detailRéalisation d'un spectromètre à fluorescence X portable
Carapelle, Alain ULg

Doctoral thesis (2013)

Réalisation d'un spectromètre XRF portable à haute résolution à détecteur X SDD et tube à rayons X. L'utilisation d'algorithmes spécifiques a permis de démontrer l'utilisation dans plusieurs cas pratiques ... [more ▼]

Réalisation d'un spectromètre XRF portable à haute résolution à détecteur X SDD et tube à rayons X. L'utilisation d'algorithmes spécifiques a permis de démontrer l'utilisation dans plusieurs cas pratiques. En particulier la mesure d'épaisseurs de coatings de 0.4 à 1500 nm grâce à une routine d'optimisation de la définition de la ROI du pic. Il a été montré qu'un monitoring d'un étalon pendant la mesure permet, via renormalisation du spectre, d'améliorer la répétabilité des mesures d'un facteur >2. [less ▲]

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See detailVers une méthode de conception de SIG 3D collaboratif
Hajji, Rafika ULg

Doctoral thesis (2013)

Our thesis work focuses on collaborative 3D GIS and considers two main aspects governing their implementation: a conceptual framework for an approach to design these systems and a technical framework ... [more ▼]

Our thesis work focuses on collaborative 3D GIS and considers two main aspects governing their implementation: a conceptual framework for an approach to design these systems and a technical framework dealing with the main issues of integration of multiple data sources from different partners in a 3D collaborative database. [less ▲]

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See detailANTIBODY-COUPLED NANORODS AS BIOSENSOR PLATFORM FOR SPECIFIC CANCER DETECTION
Schol, Daureen ULg

Doctoral thesis (2013)

This work started as part of a Specific Targeted Research Project, ADONIS (FP-6 of the European Commission) and the aim of the project was the development of active targeting gold nanoparticles for ... [more ▼]

This work started as part of a Specific Targeted Research Project, ADONIS (FP-6 of the European Commission) and the aim of the project was the development of active targeting gold nanoparticles for optoacoustic imaging, from chemistry to biology. The establishment of a biosensor composed of antibody-functionalized gold nanorods is achieved on a model of tumor, in our case prostate cancer. Prostate cancer is a major public health problem in our industrialized countries, indeed it is the most frequent cancer and the second leading cause of death by cancer in men [1]. A major challenge in prostate cancer oncology is to develop more accurate, precise and less invasive tools for early stage diagnostic, including more accurate imaging assessments than those currently available. An efficient imaging technique which significantly improves the sensitivity and the specificity of the diagnostic and enables prediction of the cancer behavior would be extremely valuable to oncologists. Briefly the developed biosensor model consists of a gold nanorod – designed to convert a primary optical excitation into a detectable acoustic signal – coupled with a monoclonal antibody that targets prostate cancer cells for a specific recognition. Improved access to the target can be achieved by targeting accessible extracellular domain of a membrane protein, here the Prostate Specific Membrane Antigen (PSMA) [2]. PSMA is a transmembrane protein considered as a suitable biomarker for prostate cancer [3] and which is under intense investigation for use as an imaging and therapeutic target. PSMA is highly expressed in prostate cancers and also expressed in the tumor associated neovasculature of most solid cancers [4]. Before biological assessments the cytotoxic surfactant, essential to form rod-shaped nanoparticles, is exchanged by a mixture of two functionalized polyethylene glycol (PEG) molecules: HS-PEG-OMe for nanoparticle passivation and HS-PEG-NH2 for subsequent coupling with the antibody. The different cytotoxicity assays are achieved to establish the toxic threshold of the surfactant in order to know what CTAB concentration maybe tolerable on the cells. This argument is important during the displacement of the surfactant, based on successive centrifugations, because the whole discard of CTAB seem to be time-consuming or even routinely unfeasible. Once this threshold drawn up, the PEGylated GNRs can be assessed on cancer cells, what seems being a common in vitro investigation. However unexpected issues came up during the experiments and had to be considered due to the properties of the nanomaterial. Nevertheless, after cytotoxicity assessment of PEGylated nanoparticles, the biosensor binding on targeted cells was assessed by fluorescence and scanning electron microscopies, two straightforward and flexible techniques. The antibody coupled to the gold nanorod is specific to the human prostate carcinoma LNCaP cell line, reported to express PSMA which is an admitted biomarker of this cell line [5]. Finally, in order to complete the specific targeting of the biosensor, the antibody-coupled gold nanorods are injected in nude mice to evaluate their biodistribution and bioaccumulation for which inductively coupled plasma mass spectrometry (ICP/MS) is the technique of choice. Preliminary optoacoustic imaging is the ultimate step for the state-of-theart of the developed biosensor. Although the promising end results, particularly biodistribution assays, new questioning swarm and this is more and more discussed in publications due to the in vivo use of nanomaterials. Owing to their increasingly extensive use, their nanometer sizes and their physiological contact (more or less long), controlling the interaction of nanoparticles with biological systems became a fundamental challenge of nanomedicine [6]. Therefore the protein opsonization on the gold nanorods is a tremendous study and is accomplished via mass spectrometry analyses. [less ▲]

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See detailSystems analysis of oscillator models in the space of phase response curves
Sacré, Pierre ULg

Doctoral thesis (2013)

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See detailSélection et caractérisation de Nanobodies inhibiteurs de métallo-β-lactamases
Sohier, Jean ULg

Doctoral thesis (2013)

Les antibiotiques, et notamment les antibiotiques à noyau β-lactame, ont révolutionné la médecine du 20ième siècle, et sauvé un nombre incalculable de vies. Leur efficacité est cependant mise en péril par ... [more ▼]

Les antibiotiques, et notamment les antibiotiques à noyau β-lactame, ont révolutionné la médecine du 20ième siècle, et sauvé un nombre incalculable de vies. Leur efficacité est cependant mise en péril par la dissémination croissante des facteurs de résistance. La production de β-lactamases par des souches infectieuses est le principal mode de résistance aux antibiotiques à noyau β-lactame. Ces enzymes hydrolysent le noyau β-lactame de ces antibiotiques, les empêchant ainsi d’exercer leur action lytique. Parmi les β-lactamases, les métallo-β-lactamases (MβLs) attirent plus particulièrement l’attention en raison de leur capacité à hydrolyser les carbapénèmes, antibiotiques considérés comme les plus efficaces, et parce qu’il n’existe à l’heure actuelle aucun inhibiteur utile d’un point de vue clinique. Avec ce travail, nous avons voulu explorer le potentiel des Nanobodies (Nbs) de camélidé en tant qu’inhibiteurs de β-lactamases, et plus particulièrement de MβLs. Ces fragments d’anticorps correspondent aux domaines variables des anticorps à chaîne lourde produits par les camélidés (HCAbs). Aussi appelés VHHs, ou « single-domain antibodies » (sdAbs), ils sont considérés comme les plus petits fragments fonctionnels dérivés d’anticorps, et peuvent être facilement sélectionnés par phage-display. Des lamas et un dromadaire ont donc été immunisés avec la MβL VIM-4, ainsi qu’avec d’autres β-lactamases choisies comme modèles. Une sélection par phage-display nous a permis d’identifier un Nb inhibiteur de VIM-4, i.e. le Nanobody Nb_VIM38. Ce Nb a été fusionné à la protéine « cherry » pour augmenter sa production. Des concentrations de l’ordre du μM en cherry-NbVIM_38 inhibent l’hydrolyse de toutes les β-lactamines testées. Par ailleurs, un modèle d’inhibition mixte hyperbolique à tendance anticompétitive est proposé. L’épitope de NbVIM_38 a pu être déterminé par immunodétection en faisant usage de peptides chevauchants. Etant donné que le site de fixation de cherry-NbVIM_38 est distant du site actif, ce Nb peut être considéré comme un inhibiteur allostérique de la MβL VIM-4, et de probablement toutes les MβLs de type VIM. Notre hypothèse est que sa fixation interfère avec la dynamique de la boucle L7 du site actif. L’inhibition de la MβL BcII par le Nanobody cAbBcII10 a aussi été étudiée. Ce Nanobody a été obtenu par K. Conrath et al. en 2001. Il a une affinité de l’ordre du nM pour la MβL BcII (« tight-binding »), ce qui devrait être pris en compte si une caractérisation détaillée de l’inhibition devait être réalisée. De manière surprenante, l’inhibition observée est partielle et dépendante du substrat, ce qui suggère un modèle d’inhibition mixte. Ce Nb peut probablement aussi être considéré comme un inhibiteur allostérique. Ces Nanobodies illustrent la possibilité d’une inhibition allostérique des MβLs. Cette piste mériterait peut-être d’être explorée. [less ▲]

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See detailEvaluation échocardiographique de la fonction cardiaque chez le cheval en coliques
Borde, Laura ULg

Doctoral thesis (2013)

Endotoxemia is a common complication of colic in adult horses and its outcome is mainly related to cardiovascular status. Endotoxic shock, like septic shock, involves hypovolemic, cardiogenic and ... [more ▼]

Endotoxemia is a common complication of colic in adult horses and its outcome is mainly related to cardiovascular status. Endotoxic shock, like septic shock, involves hypovolemic, cardiogenic and distributive components leading to tissue hypoperfusion with a high risk for multiple organ failure and an elevated mortality rate in equine and human intensive care units. Via the release of pro-inflammatory mediators, endotoxins induce a fall in systemic vascular resistance (SVR) and a drop of cardiac output (CO) resulting both from reduction in venous return and myocardial depression. First, CO is preserved thanks to a compensatory vasoconstriction and an increase in heart rate (HR), myocardial contractility and venous return. However, a loss of vascular responsiveness to catecholamines and a myocardial depression finally result in a drop of CO and SVR with a progressive hypotension despite a persistent tachycardia. The time point during the course of septic shock when hemodynamic monitoring is used has been proven to influence outcome, allowing early goal-directed therapy in humans. Unfortunately, hemodynamic monitoring in conscious horses is often limited due to animal size, working conditions and lack of patient cooperation. Therefore, such as in human patients, echocardiography could provide useful non invasive information about stroke volume (SV) and CO, systolic and diastolic function as well as fluid status. In human septic shock patients, this technique has emphasised a myocardial depression with both diastolic and systolic dysfunction reversible in survivors. Previous studies in horses focused on quantitative evaluation of hemodynamic parameters after an experimental endotoxin challenge. However, LV function had not been reported in naturally-occurring endotoxemia in horses. The purpose of the first prospective study was to assess the impact of clinically-occuring endotoxic shock on echocardiographic indices of LV systolic function in horses. Fifty horses admitted in clinic on emergency for colic were submitted to an echocardiographic exam on admission. A shock score from 1 to 4 was established for each horse based on clinical evaluation, non invasive systolic blood pressure and blood tests measurements. LV echocardiographic parameters were compared between the 4 groups according to the shock score (SS) (SS1: no or discrete signs of shock, n=11; SS2 : mild, n=17; SS3: moderate, n=12; SS4: severe, n=10) using a multivariable analysis. Significance was set at p < 0.05. Stroke volume, stroke index (SI), ejection time (ET), ejection time index corrected for HR (ETI), aortic velocity time integral (AoVTI), aortic flow acceleration time (TTP) and deceleration time (DTAo) were significantly lower, whereas aortic flow acceleration rate (dv/dtAo) was significantly higher in shocked horses than in SS1. CO was not significantly different between groups. Even if those results were difficult to interpret because of the shock-induced changes in loading conditions of the heart, they suggested that alterations in some indicators of systolic function can be quantified by Doppler echocardiography in horses with colic-induced endotoxemic shock. The aim of the second study was to non invasively assess the impact of colic-related endotoxic shock on equine diastolic cardiac function. Sixty-eight horses admitted in clinic on emergency with colic were included in this study. A similar SS was established for each horse. LV echocardiographic parameters were compared between the 4 groups according to the SS (SS1 n=14; SS2 n=16; SS3 n=27; SS4 n=12) using a multivariable analysis. Significance was set at p < 0.05. Deceleration rate of peak early LV filling velocity, peak late LV filling velocity and E/Em (peak early LV filling velocity (E) to peak early myocardial velocity (Em) ratio) were significantly higher whereas time to Em onset was significantly lower in high shock score groups compared with horses with no or mild signs of shock. The results of this second study could suggest a diastolic dysfunction with a rise of LV filling pressure ocurring with endotoxic shock in horses. Since E/Em has shown to be a very reliable predictor of mortality in human with septic shock, the results of this second study warranted further investigations. To assess the prognostic value of echocardiographic parameters of LV function in horses with endotoxic shock, 41 horses admitted for colic with clinical evidence of systemic inflammatory response syndrome associated to hyperlactatemia or hypotension underwent echocardiographic examination on admission. LV echocardiographic parameters were compared between nonsurvivors (n=29) and horses that survived to discharge (n=12). With comparable heart rate and LV preload estimate, LV SV, AoVTI, DTAo, ET and ETI of aortic flow and Em were lower in the nonsurviving than in the surviving horses while pre-ejection period to ejection time ratio (PEP/ET) of Doppler aortic flow and E/Em ratio were higher (p<0.05). A cut-off value of 0.26 for PEP/ET predicted mortality with 100% sensitivity and 42% specificity (area under the receiver operating characteristic curve (AUC): 0.71), whereas a cut-off value of 2.67 for E/Em predicted mortality with 100% sensitivity and 83% specificity (AUC: 0.89). The results of this third study suggested that echocardiography may provide prognostic information in colic horses with clinical evidence of endotoxic shock. Especially, PEP/ET and E/Em could be useful markers of systolic and diastolic dysfunction, respectively, to detect horses with a high risk of death requiring more intensive cardiovascular monitoring as it has been reported in human patients with septic shock. Finally, to assess LV function after preload restoration in colic horses, 5 horses were followed echocardiographically from admission to at least 24 hours after colic surgery in a preliminary study. Systolic dysfunction was detected in 4/5 horses and diastolic dysfunction assumed in 2/5 horses and suspected in the 3 other horses during hospitalisation. Moreover, echocardiography provided useful diagnosis informations about hemodynamic and fluid status suggesting that ultrasonographic monitoring of cardiovascular function could be of interest in equine intensive care. 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See detailEcotoxicology of Organic and Inorganic Pollutants in Chelonians. Marine Turtle Risk to Pollutant Exposure
Dyc, Christelle ULg

Doctoral thesis (2013)

Marine turtles are oviparous vertebrates subdivided in seven existing species widespread in most of the oceans. They are suffering from human activities and especially from fishery by-catch, egg ... [more ▼]

Marine turtles are oviparous vertebrates subdivided in seven existing species widespread in most of the oceans. They are suffering from human activities and especially from fishery by-catch, egg harvesting, adult poaching, degradation of their habitats, environmental pollution and climate change. While direct threats (e.g. fishery by-catch) are often less challenging to identify and predict, indirect threats associated with environmental pollution often induce more insidious effects that can take longer to manifest and be more significant and lasting. Understanding the marine turtle risks to pollutant exposure is critical because a) pollutants are persistent and ubiquitous in the environment, b) all the marine turtle species are listed on the Red List of Threatened Species by the IUCN and c) pollutants were indicated to adversely threaten the marine turtles’ survival, especially the developing individuals. Despite decades of investigations and evidences of significant pollutant threats, few data is still being available for marine turtles. The present study proposed to assess pollutant exposure in the green Chelonia mydas and hawksbill Eretmochelys imbricata marine turtles nesting in Guadeloupe (French West Indies FWI, Caribbean Sea). Trace elements (e.g. selenium, mercury and cadmium) and organohalogen pollutants OHP (e.g. polychlorobiphenyls PCBs and chlordecone) were determined in dermis collected from the nesting females and in their eggs. A broad range of pollutants was detected in these tissues among which chlordecone. This was quite interesting because of the past history of chlordecone in the FWI. Results suggested that the green and hawksbill marine turtles fed on contaminated foraging ground, accumulated chlordecone in their body and then transferred it into their eggs during the egg formation. Both Guadeloupean marine turtle species appeared less exposed to OHP and trace elements than other marine turtle populations, except for other green marine turtle colonies (i.e. trace elements). The developing embryo risks to pollutant exposure were evaluated as those for the Guadeloupean inhabitants that consume marine turtle eggs. Little threat may be expected for the Guadeloupean inhabitants while some pollutants may affect the marine turtle embryos’ survival of both species (i.e. p,p’-DDE, cadmium, mercury and selenium). The present study was not the first to arise concern about embryo risks to selenium exposure as suggested by previous reptilian studies including marine turtles. As part of the present study, the toxicokinetics and dynamics of selenium were thus approached under laboratory conditions by using the slider turtle Trachemys scripta as model candidate. Juvenile turtles dietary exposed to selenium effectively accumulated selenium in their tissues but appeared unaffected by the exposure. Indeed, their body condition and antioxidant system were unaffected over the feeding trial. This was unexpected since the dietary levels used in the present study were indicated to induce sublethal effects in birds and other reptilian species. Selenium toxicity was initiated by oxidative stress leading to unusual production of oxidant species such as reactive oxygenated species. Therefore, turtles could tolerate high selenium levels due to specific trait of life (e.g. ability to deal with oxygen introduction after anoxic conditions associated with hibernation and/or diving). It is challenging to transpose results obtained from laboratory animals exposed to controlled conditions to wild individuals exposed to many environmental factors, even if species are closely related. The development life-stage further greatly affects the sensitivity of individuals to pollutant exposure. Nevertheless, the green and hawksbill marine turtle embryos could also tolerate high selenium exposure. This would contradict the risk assessment conducted in the present study but would be possible considering the food habits of both marine turtle species. These species are feeding on seagrasses and sponges which may expose the marine turtles to natural toxic compounds. Consequently, they could have developed adaptive strategies to deal with toxics in response to pressure at their foraging ground. To date, more works are needed to better understand the metabolism of selenium in turtles as well as to properly determine toxic thresholds of selenium for marine turtles. Finally, nondestructive collection techniques were tested for their suitability in assessing the turtle exposure to pollutants in both field and laboratory conditions. Keratinized tissues (i.e. carapace and skin) were proposed as promising tools and should warrant further investigations in researches aiming at the conservation of marine turtles. The present study provides several firsts such as the first baseline levels of a) pollutants in green and hawksbill marine turtles nesting in an area not investigated yet (i.e. Guadeloupe), b) OHP in the marine turtle dermis, c) OHP in hawksbill turtle eggs and d) chlordecone in marine turtle tissues. The first toxicological data on e) selenium kinetics and dynamics were further provided in turtles. [less ▲]

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See detailGeometric statistical processing of brain diffusion tensor images
Collard, Anne ULg

Doctoral thesis (2013)

Nowadays, the functioning of the human brain is still one of the biggest mysteries of humanity. The multiple holes in the understanding of the human brain explain why an intensification of brain-oriented ... [more ▼]

Nowadays, the functioning of the human brain is still one of the biggest mysteries of humanity. The multiple holes in the understanding of the human brain explain why an intensification of brain-oriented research can be observed since a few years. One of the most recent techniques to better understand the brain is Diffusion Tensor Imaging (DTI), a noninvasive imaging modality that provides information about orientation of nervous fibers, and their spatial density, with a high resolution. The particular nature of DTI images makes them multi-valued. Their processing therefore requires to adapt state-of-the-art techniques, which are fundamentally tailored to scalar-valued images. The objective of this PhD thesis is to develop a novel framework for the processing of tensor diffusion images. The focus is threefold: first, we adopt a Riemannian geometric framework to generalize image processing from linear to nonlinear spaces. Second, we aim at developing a processing framework that retains the physical information of measurement data. Thirdly, the proposed algorithm must be computationally efficient in order to scale with the data size of clinical applications. The main contribution of this thesis is the development of a novel processing method, which has the particularity to preserve the important features of diffusion tensors, while being computationally affordable. This technique is based on the decoupling between the two types of information conveyed by tensors: the diffusion intensity on one hand, and the orientation of diffusion on the other hand. Moreover, the computational cost is limited thanks to the use of unit quaternions to represent tensors orientation. Another contribution of the thesis lies in the development of a statistical method for group comparison. This method uses the notion of similarity measure between the values, a notion that can be defined for multi-valued images, and which enables to reduce the computational cost. The use, for the statistical tests, of the similarity measure associated to our framework turns out to be efficient and informative. The study of geometric methods for multi-valued images together with the study of potential applications of diffusion tensor images have enabled the introduction of a novel framework, which is particularly appropriate for those images. The basic operations developed in the thesis open the way to more sophisticated processing algorithms, while ensuring the preservation of the main information associated to the tensors. [less ▲]

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See detailImplicit Real Vector Automata
Degbomont, Jean-François ULg

Doctoral thesis (2013)

This thesis introduces a new data structure, the Implicit Real Vector Automaton (IRVA), suited for representing symbolically polyhedra, i.e., regions of n-dimensional space defined by finite Boolean ... [more ▼]

This thesis introduces a new data structure, the Implicit Real Vector Automaton (IRVA), suited for representing symbolically polyhedra, i.e., regions of n-dimensional space defined by finite Boolean combinations of linear inequalities. IRVA can represent exactly arbitrary convex and non-convex polyhedra, including features such as open and closed boundaries, unconnected parts, and non-manifold components. In addition, they provide efficient procedures for deciding whether a point belongs to a given polyhedron, and determining the polyhedron component (vertex, edge, facet, ...) that contains a point. An advantage of IRVA is that they can easily be minimized into a canonical form, which leads to a simple and efficient test for equality between represented polyhedra. Elementary IRVA representing primitive polyhedra, such as linear (in)equations and vector spaces are easily constructed and algorithms have been developed for computing Boolean combinations as well as projections of polyhedra represented by IRVA. These algorithms are illustrated by complete examples of executions as a support for the comprehension of their mechanisms. Another contribution is a first prototype implementation of an IRVA library, containing functions for building and manipulating arbitrary n-dimensional polyhedra. We reinforce the presentation of the implementation by discussing some design choices. Such choices include the use of exact arithmetic. Finally, experimental results are presented and discussed. These experiments pave the way to future adaptations and improvements. [less ▲]

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See detailImmunotoxicology of methylmercury and other contaminants in harbour seals (Phoca vitulina) from the North Sea
Dupont, Aurélie ULg

Doctoral thesis (2013)

Environmental contaminants are suspected to have detrimental effects on marine mammal health. They were notably hypothesised to be involved in the severity and extent of catastrophic viral epidemics that ... [more ▼]

Environmental contaminants are suspected to have detrimental effects on marine mammal health. They were notably hypothesised to be involved in the severity and extent of catastrophic viral epidemics that recently affected the harbour seal (Phoca vitulina) population from the North Sea. High levels were indeed found in their tissues. However, the exact effects of those pollutants on free-ranging harbour seal health are not yet elucidated. In the field of immunotoxicology, in vitro cell culture techniques have been developed and are considered as valuable tools to assess specific toxicity mechanisms. The first objective of this study was to investigate the relationships between environmental contaminant levels found in harbour seal blood and lymphocyte proliferation responses in vitro. Indeed, wild harbour seal cells used in the framework of in vitro culture studies are isolated from the blood of animals that are contaminated, but little is known about the possible relationships between them. They were thus investigated in harbour seals from the North Sea. Peripheral blood leucocytes were isolated and cultured during 72h with Concanavalin A (ConA), a mitogen agent, to evaluate the lymphocyte proliferative responses as a stimulation index. The ConA-induced lymphocyte proliferation assay evaluates their ability to proliferate in response to a polyclonal stimulation, which is considered to reflect the activation of the immune response after an antigenic stimulation in vivo. No statistically significant relationship was found between the lymphocyte stimulation index and blood pollutants or class of pollutants studied (i.e. mercury, lead, persistent organic pollutants, pentachlorophenol, tribromoanisole) in harbour seals sampled while in good body condition and presenting no sign of disease. However, the number of lymphocytes per milliliter of whole blood appeared to be negatively correlated to pentachlorophenol, an organochlorine pesticide. A high interindividual variability of lymphocyte stimulation indexes was observed although cells were isolated in the same way and cultured in identical conditions. This is probably linked to a whole set of parameters such as precise age, sex, life history leading to particular immune status (probably partly related to pollutant loads), physiological parameters and inevitable experimental variability. So, in a general manner, experiments with in vitro immune cell cultures of wild marine mammals should be designed so as to minimise confounding factors in which case they remain a valuable tool to study pollutant effects in vitro. The second objective of this study was to determine underlying mechanisms of methylmercury immunotoxicity. Indeed, among the numerous contaminants found in harbour seal tissues, methylmercury is one of the most hazardous organic compounds known to have numerous detrimental effects on living organisms. It has the property to bioaccumulate and biomagnify in the trophic chain, and can reach very high levels in harbour seal tissues. Peripheral blood leucocytes exposed to relatively low concentrations of methylmercury chloride (MeHg) in vitro revealed a significant decrease of viable cell counts with obvious ultrastructural effects. A higher frequency of apoptosis was observed in lymphocytes, in which mitochondria and nuclei may have been targeted, as demonstrated by ultrastructural analysis. These results were in accordance with the significant decrease of the mitochondrial membrane potential and of lymphocyte proliferation (BrdU assay) observed. The toxicity of this compound was shown to be counteracted by selenium. However, little is known about that interaction in marine mammal blood and the underlying mechanisms still remain unclear. The present study aimed to investigate the in vitro effects of relatively low (0.75 µM) MeHgCl levels on harbour seal ConA-stimulated leucocytes while added concomitantly to Se. Two different forms of Se were studied: selenite and selenomethionine. Their concentrations were within the range of those measured in free-ranging harbour seal blood, and in a Hg:Se ratio of 1:10. Lymphocyte proliferation as well as the mitochondrial membrane potentials were significantly reduced following in vitro exposure to MeHgCl during 72h. No significant difference was found when sodium selenite or selenomethionine was added concomitantly to MeHgCl. Conversely, on average, Se alone did not lead to significant decreased proliferation and mitochondrial membrane potentials. The absence of protection of Se, either in organic or inorganic form, against Hg toxicity in harbour seal blood leucocytes in vitro raises concern as regards the deleterious effects this toxic compound could have on marine mammal immune system. The range of current Hg levels found in free-ranging harbour seals from the North Sea encompasses exposure levels which elicited deleterious effects on lymphocytes in the present study. This highlights the potential for effects on host resistance to disease. [less ▲]

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See detailAnalysis of performance and robustness of biological switches: local tools for non-local dynamical phenomena.
Trotta, Laura ULg

Doctoral thesis (2013)

Biological switches are frequently encountered in mathematical modeling of biological systems because binary decisions are at the core of many cellular processes. A bistable switch presents two stable ... [more ▼]

Biological switches are frequently encountered in mathematical modeling of biological systems because binary decisions are at the core of many cellular processes. A bistable switch presents two stable steady-states, each of them corresponding to a distinct decision. These two decisions are assumed to result from the interactions between biochemical effectors at the molecular level. Because these molecular interactions are particularly complex, involving many effectors, mathematical models of biological switches are often high dimensional and nonlinear. Therefore, an analysis of these systems is challenging. In this dissertation, we try to identify principles and tools to study the performance and robustness of biological switches. Our first contribution is to highlight the dynamical nature of these switches. A biological switch encodes a decision-making process rather than a static binary code. It captures dynamical phenomena that are important for the decision-making process, such as decision latencies and reversibility. Our second contribution is methodological. While most of the classical analysis tools are based on a linearization of the system around a stable steady-state, a switch is a non local phenomenon involving a transition between two stable steady-sates. Rather than studying the system around stable equilibria, we identify the local rulers of the decision-making process in both the state and parameter spaces and propose a local analysis in the vicinity of these particular points. Our third contribution is to emphasize the added value of an abstract (that is, mathematical) framework for the analysis of biological switches. By studying different models, we point out that the same principles can be used to encode dynamical phenomena in very different cellular processes. Physiological processes as different as apoptosis, the cellular choice of death, and action potential, the cellular choice to emit an electrical spike, share common features when regarded as decision-making processes. [less ▲]

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See detailLes forêts à Marantaceae au sein de la mosaïque forestière du Nord de la République du Congo : origines et modalités de gestion
Gillet, Jean-François ULg

Doctoral thesis (2013)

The Marantaceae forests are conspicuous by an unusual physiognomy with a giant herbaceous continuous stratum in association with a scattered tree component regenerating with difficulty. This vegetation ... [more ▼]

The Marantaceae forests are conspicuous by an unusual physiognomy with a giant herbaceous continuous stratum in association with a scattered tree component regenerating with difficulty. This vegetation, arranged as a heterogeneous patchwork within the lowland semi-deciduous forests, is widely extended in the Northern Republic of Congo. The thesis aims to define and describe the vegetation types of this forest patchwork in order to identify the key factors that have shaped it and to recommend an appropriate forestry. To achieve this, the study was conducted in the CIB-OLAM logging concession (Sangha and Likwala departments). Two types of monodominant G. dewevrei forests and three hydromorphic vegetation types have been described trough on ordination multivariate analysis of the woody stand in relation with the hydrological conditions. In addition, a multi-strata classification of mixed terra firma forests has individualized five vegetation types that are defined and characterized. These are: (1.1) open vegetation types with Marantaceae and Aframomum cf. subsericeum, (1.2) sparse Marantaceae forests with Megaphrynium macrostachyum and (1.3) with Haumania liebrechtsiana, (1.4) dense forests with Marantaceae and (2) moist semi-deciduous dense forests (3 forms: (2.1) with Sarcophrynium schweinfurthianum, (2.2) with Haumania danckelmaniana and (2.3) with Triplochiton scleroxylon). They are characterized by their specific richness, floristic composition and/or structural parameters. Thanks to an archaeo-pedological study coupled with 14C dating, we established that the Marantaceae forests suffered the strongest past disturbances. The perturbations were mostly caused by humans and predominated around 1,550 yrs BP. They would be related to an expansion phase of the oil palm Elaeis guineensis and its exploitation by humans. The simultaneous degradation of the forest cover, combined with poor and wet soils, has facilitated the expanding of giant herbs, gradually inhibiting the tree regeneration. The dense forests on the contrary, whose the dominant species are light-demanding and wind-dispersed trees (eg. T. scleroxylon) would have a more recent origin. Indeed, they date back about 7 to 2 centuries and are related to shifting cultivation on richer and well-drained soils. The logging within the open canopy Marantaceae vegetation types results in a recovery of the forest dynamic on skid trails. Thanks to the destruction of the herbaceous understorey by logging equipment. On these trails, an assisted regeneration by selection and freeing of seedlings and an additional planting turns out to be an effective technique for woody species regeneration. The results are especially encouraging for the following species: Canarium schweinfurthii, Terminalia superba, Ricinodendron heudelotii and Nauclea diderrichii whose average height growth is respectively 154, 130, 125 and 124 cm, one year after the silvicultural treatment. Given the evolutionary dynamics of these open canopy Marantaceae vegetation types, systematic reforestation with timber species on skid trails seems to be the most appropriate silvicultural technique to ensure sustainable exploitation. [less ▲]

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See detailLa propriété intellectuelle : nature juridique et régime patrimonial
Vanbrabant, Bernard ULg

Doctoral thesis (2013)

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See detailProduction et caractérisation d'hydrolysats de pectine obtenus par voies enzymatique et thermique(micro-onde)
Combo, Agnan Marie Michel ULg

Doctoral thesis (2013)

L’objectif de cette thèse est de contribuer à étudier d’une part les voies de production des oligosaccharides pectiques (POS) et d’autre part à déterminer leurs principales propriétés physico-chimiques ... [more ▼]

L’objectif de cette thèse est de contribuer à étudier d’une part les voies de production des oligosaccharides pectiques (POS) et d’autre part à déterminer leurs principales propriétés physico-chimiques. Pour ce faire, deux voies de production ont été utilisées : enzymatique et thermique. En ce qui concerne la production de POS par voie enzymatique, six pectinases commerciales de qualité alimentaire (Endopolygalacturonase-M2, Pectinase P-4716, Viscozyme L, Pectinex Ultra SP-L, Pectinase 62L et Macer8 FJ) ont été testées sur une pectine modèle (acide polygalacturonique) pour sélectionner la pectinase capable de produire au mieux des POS. Préalablement, la totalité de ces pectinases a été caractérisée en termes d’activité polygalacturonase et de pureté: toutes possédaient une activité polygalacturonase, mais concernant la pureté, ces préparations commerciales se sont révélées être un mélange de plusieurs activités enzymatiques à l’exception de l’Endopolygalacturonase-M2 (EPG-M2). Cette dernière a présenté, après deux heures d’hydrolyse de l’acide polygalacturonique, les meilleurs résultats pour la production de POS avec 18% et 58% de la masse convertie en acides di et tri-galacturoniques respectivement (contre 0,22 et 0,20% pour la Pectinase P-4716, 0,9 et 0,3% pour la Viscozyme, 2,7 et 9,4% pour la Pectinex Ultra SP-L, 0,4 et 0,3% pour la Pectinase 62L et 0,2 et 0,15% pour la Macer8 FJ). L’EPG-M2 a donc été choisie pour modifier la pectine de betterave dans la suite du travail. Ainsi, en utilisant l’EPG-M2 combinée à une pectine-méthylestérase (Rapidase Smart®), des poudres de POS ont été obtenues par lyophilisation après hydrolyse de la pectine de betterave. Une étude des propriétés chimiques et physico-chimiques de ces POS a été ensuite réalisée par chromatographie liquide haute performance, par analyse thermogravimétrique couplée à la spectroscopie infrarouge à transformée de Fourier, par analyse calorimétrique différentielle et par diffraction des rayons X. Les analyses chromatographiques ont montré que les POS sont composés de mélanges d’oligomères de masses moléculaires (Mw) diverses avec différentes teneurs en acide galacturonique. L'analyse thermique a toutefois révélé que les POS étaient plus sensibles à la dégradation thermique que la pectine native. L'analyse par ATG-IRTF n’a montré aucun changement majeur dans les groupes fonctionnels après hydrolyse enzymatique de la pectine de betterave. La diffraction RX des POS a indiqué une diminution de la cristallinité par rapport à la pectine native. La seconde voie suivie pour la production de POS a été une voie hydro-thermique par utilisation de micro-ondes. Le potentiel des micro-ondes pour produire des POS a été exploré et les conditions optimales conduisant aux meilleures teneurs en POS ont été déterminées. Trois paramètres ont été simultanément étudiés: la température, le temps ainsi que le pH. Un plan expérimental a permis d’évaluer l’effet de ces paramètres sur la production de POS à partir d’une solution de pectine de betterave. Une diminution considérable de la Mw de la pectine de betterave a été observée avec des Mw correspondant à des oligosaccharides de degré de polymérisation (DP) moyen de l’ordre de 24 à 25. Les résultats de cette étude ont montré qu’un pH de 3, une durée supérieure à 15 min et une température comprise entre 140 et 148°C sont les conditions les plus favorables à l’obtention de POS. Ces deux voies d’hydrolyse de la pectine en POS pourraient représenter des méthodes pratiques et fiables pour une production en routine de POS, composés utilisables comme ingrédients additifs pouvant être incorporés dans des formulations alimentaires ayant des propriétés nutritionnelles et/ou technofonctionelles. [less ▲]

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See detailEvaluation de la justesse vocale en contexte mélodique
Larrouy, Pauline ULg

Doctoral thesis (2013)

In order to determine if a vocal performance is “in tune” or “out of tune”, to better understand the causes of poor-pitch singing or to evaluate the quality of a singer, tools are necessary. Two methods ... [more ▼]

In order to determine if a vocal performance is “in tune” or “out of tune”, to better understand the causes of poor-pitch singing or to evaluate the quality of a singer, tools are necessary. Two methods are actually used to evaluate the vocal accuracy of a sung performance. The "subjective" method makes use of judges whereas the "objective" method uses computer tools. While the first method allows a rapid assessment, it lacks precision. The “objective” method seems currently preferred but shows limits that our research aims to overcome. The first step was to develop a functional and objective method, which takes into account the different melodic errors we encounter when using the Western tonal system (i.e. respect of the melodic contours, the pitch intervals, and the tonal center). We then applied this method to sung performances of occasional and professional singers. These first studies confirmed the functionality and legitimacy of our method. However, some limits occurred regarding the evaluation of Western operatic singers. In a second step, we observed the relevance of this method and more specifically the interest to evaluate complete melodies (compared to pitch matching tasks) and the interest to differentiate the possible melodic errors. Finally, the comparison of our method with the evaluation made by music experts has enabled us to examine their perception and definition of vocal accuracy. Through seven studies, we explored the theoretical and methodological aspects of vocal accuracy in a melodic context. Taken together, the results of these studies allow us to clarify the definition of vocal accuracy and to consider the several clinical and experimental perspectives of our objective method for evaluating singing voice accuracy. [less ▲]

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See detailDevelopment of an analytical method to determine the composition of cryolitic baths used in the Hall-Heroult process, by Raman spectroscopy, at 1000°C
Malherbe, Cédric ULg

Doctoral thesis (2013)

Worldwide metallic aluminium production involves the Hall-Héroult process where the metal is electro-deposited from aluminium oxide solubilised in a molten NaF-AlF3-CaF2 mixture at around 950°C. The ... [more ▼]

Worldwide metallic aluminium production involves the Hall-Héroult process where the metal is electro-deposited from aluminium oxide solubilised in a molten NaF-AlF3-CaF2 mixture at around 950°C. The cryolitic melt is conveniently characterised by both the molar NaF/AlF3 ratio and the Al2O3 content. Nowadays the Hall-Héroult process remains the more economically efficient process even if it still suffers from a high consumption of energy. In particular the overvoltage required by the electrolysis is strongly dependent on the melt composition, especially regarding the Al2O3 content. Controlling the industrial baths composition during the process is therefore critical to reduce the energy loss. Unfortunately there is, up to now, no in situ direct analytical method to do so. Considering our experience in the study of such highly corrosive media by Raman spectroscopy, that technique has been applied to directly determine the melt composition. Three sets of reference spectra are considered in this study, each of them recorded with a different setup. The employed setups were developed to reach progressively, at the laboratory scale, a design that is suitable for a plant application. Eventually, a high quality spectrum can be recorded by the top of the melt, in less than 20 seconds. The employed apparatus is found to influence significantly the shape and quality of the spectra, and consequently their involvement in the quantification. A complex digital treatment of the spectral data acquired is necessary because all Raman bands of interest strongly overlap and some are situated close to the Rayleigh decay. Two main quantitative procedures for the melt composition determination are studied. The first one, the AutoAnalysis procedure, developed in the past and adapted here to the new data, gives reliable predictive results for both the NaF/AlF3 molar ratio and the alumina content. They can be determined with an absolute deviation of 0.06 molar ratio unit and 0.5 wt% respectively. However, the intensity normalisation, required for comparing the intensities of different spectra, relies on the Rayleigh decay that is likely to change with the experimental conditions in the plants. In our second quantitative procedure, the NormaAnalysis procedure, the intensity normalisation is based on the equilibria taking place in the melt. Since those equilibria do no differ with the experimental setup, the NormaAnalysis procedure can be imported to the industrial field. The predicted composition is also evaluated with a good precision: the NaF/AlF3 molar ratio and the alumina content can be determined with an absolute deviation of 0.08 cryolitic ratio unit and 0.3 wt% respectively. It is concluded that the composition of the melt can now be determined with our NormaAnalysis procedure, from a single Raman spectrum, recorded with a Raman apparatus exportable for an in situ measurement on the industrial cells. [less ▲]

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See detailEtude des relations pucerons-virus en pomme de terre et perspectives de stratégies alternatives de lutte
Yattara, Almouner Ag Alhamis ULg

Doctoral thesis (2013)

Abstract – Sustainable approach of crop production, including the implementation of biological control is essential in potato pest and disease control in general, and aphids and viruses associated in ... [more ▼]

Abstract – Sustainable approach of crop production, including the implementation of biological control is essential in potato pest and disease control in general, and aphids and viruses associated in particular. In addition, given to the lack of data available for Mali, it was essential to study the aphid and virus actors related to this geographical location. Here we firstly proposed to compare two techniques for trapping aphids. During two growing seasons, the yellow traps were found to be more effective (73.6%) than Malaise traps (26.4%) in the potato aphid survey. The use of trapping techniques and limitations of each of these were discussed in the context of the implementation of a monitoring crop pests in an area or issue of sampling aphids collected. How to efficiently proceed for this purpose was discussed. Then, as very few data documenting the presence and impact of aphids in Mali were available, we followed for three consecutive years, the abundance and diversity of aphids in the fields of potato consumption. Nineteen species of aphids have been identified for the first time in all investigated areas. As a corollary, the presence of potato virus Y and potato leaf roll virus was shown in the two main producing areas of potato. The occurrence of these viral diseases has proved to be very consistent from one year to another with relatively high levels. This study is a first quantification in this region of Mali of the importance of aphid vector- virus couples in cultured potato. Finally, a comparison with the conditions of production in Belgium was performed and higher abundance and richness of aphid species was found in Belgium than in Mali. Unlike Mali, only the potato virus Y detected by RT-PCR in the fields of plant production and consumption in Wallonia with the appearance of PVY-N and PVY-NTN strains. The relationship between the diversity of aphids - abundance and the presence of virus in the potato fields were examined to improve the control strategies of the virus. [less ▲]

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See detailLes facteurs parentaux, les stéréotypes de genre et l'intelligence émotionnelle dans le développement d'une sensibilité à l'anxiété chez l'enfant
Stassart, Céline ULg

Doctoral thesis (2013)

Ce travail de thèse tente de favoriser une meilleure connaissance de l'étude de la sensibilité à l'anxiété chez l'enfant et de sa pertinence, ainsi que de permettre une compréhension plus précise des ... [more ▼]

Ce travail de thèse tente de favoriser une meilleure connaissance de l'étude de la sensibilité à l'anxiété chez l'enfant et de sa pertinence, ainsi que de permettre une compréhension plus précise des facteurs impliqués dans le développement d'une sensibilité à l'anxiété chez l'enfant. De manière plus spécifique, il poursuit trois objectifs précis. (1) Après une description détaillée de la littérature sur la pertinence d'étudier un concept tel que la sensibilité à l'anxiété, il parait important d'être en mesure de posséder une échelle valide permettant de l'investiguer. Le questionnaire de sensibilité à l'anxiété chez l'enfant, intitulé Children Anxiety Sensitivity Index (CASI) de Silverman, Fleisig, Rabian, & Peterson (1991), n’a pas encore fait l'objet d'une validation dans une population belge. Une analyse de la structure factorielle, ainsi qu'une exploration des qualités psychométriques de la version française de la CASI est le premier objectif de cette étude. (2) Le deuxième objectif concerne l'impact de rôle de genre et de l'intelligence émotionnelle dans le développement d'une sensibilité à l'anxiété chez l'enfant. Différents auteurs mettent en avant la pertinence de prendre en compte le rôle de genre, plutôt que le sexe biologique, dans la .prévalence des troubles anxieux. Ceci est davantage documenté dans une population adulte, et n'a jamais été investigué dans la sensibilité à l'anxiété. De plus, les compétences émotionnelles ont montré leur facteur protecteur dans la vie de l'enfant, tant au niveau relationnel, que psychologique et physique. Ce travail investigue si cet effet protecteur est également présent dans la sensibilité à l'anxiété. (3) Enfin, le troisième objectif approfondit la question de l'influence des parents dans le développement d'une sensibilité à l'anxiété chez l'enfant. En effet, la littérature met en évidence l'implication parentale dans la présence des peurs des sensations anxieuses chez l'enfant. En conséquence, la sensibilité à l'anxiété des parents ainsi que les expériences d'apprentissages catastrophiques au sein du milieu familial sont examinées. De plus, l'influence de deux modérateurs est investigué: plus spécifiquement, l'impact d'un facteur de vulnérabilité et de protection, respectivement le niveau de féminité (du parent et de l'enfant) et l'intelligence émotionnelle de l'enfant dans le lien entre les facteurs parentaux et le développement d'une sensibilité à l'anxiété chez l'enfant. [less ▲]

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See detailSynthèse et étude biologique des phosphonopeptides: les rhizocticines, les plumbemycines et leurs analogues
Gahungu, Mathias ULg

Doctoral thesis (2013)

Rhizocticins and Plumbemycins are natural phosphonate antibiotics produced by the bacterial strains Bacillus subtilis ATCC 6633 and Streptomyces plumbeus, respectively. Up to now, these potential ... [more ▼]

Rhizocticins and Plumbemycins are natural phosphonate antibiotics produced by the bacterial strains Bacillus subtilis ATCC 6633 and Streptomyces plumbeus, respectively. Up to now, these potential threonine synthase inhibitors have only been synthesized under enzymatic catalysis. Here we report the chemical stereoselective synthesis of the non-proteinogenic (S,Z)-2-amino-5-phosphonopent-3-enoic acid [(S,Z)-APPA] and its use for the synthesis of Rhizocticin A and Plumbemycin A. In this work, (S,Z)-APPA was synthesized via the Still–Gennari olefination starting from Garner’s aldehyde. The Michaelis–Arbuzov reaction was used to form the phosphorus–carbon bond. Oligopeptides were prepared using liquid phase peptide synthesis (LPPS) and were tested against selected bacteria and fungi. [less ▲]

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See detailVirus transmission efficiency: investigation on Chinese clone diversity of wheat aphids and role of aphid endosymbionts
Yu, Wenjuan ULg

Doctoral thesis (2013)

Clone diversity in aphids (Hemiptera: Aphididae) was known to be related to acceptance and suitability of host plant. Occurrence of particular patterns of bacterial endosymbionts was demonstrated to ... [more ▼]

Clone diversity in aphids (Hemiptera: Aphididae) was known to be related to acceptance and suitability of host plant. Occurrence of particular patterns of bacterial endosymbionts was demonstrated to specific plant – aphid interactions. Barley yellow dwarf virus (BYDY) has a high degree of vector specificity to be transmitted only by specific species of cereal aphids. BYDV and their aphid vectors are associated in a variety of complex interactions. In this context, the main objective of this dissertation was to understand the virus partners in host-aphid interactions, the role of endosymbionts pattern on virus transmission efficiency and (E)-β-farnesene (EBF) production. Aphids were of closely association with bacterial endosymbionts; which substantially affect the physiology, ecology, reproduction and behaviors of aphids in a variety of way. Firstly, endosymbionts were selective eliminated by antibiotic, the EBF production was reduced; from the result of protein analysis, some protein from Buchnera aphidicola were found. It demonstrated that endosymbionts take part in the EBF production. Secondly, Fourteen populations of Sitobion avenae Fabricius (Hemiptera: Aphididae) originating from China were tested for their ability to transmit Barley yellow dwarf virus-PAV (BYDV-PAV, one isolate from Belgium, another from China) using wheat plants. All populations could transmit BYDV-PAV and variation in transmission rates ranged from 24.42% to 66.67% with BYDV-PAV-Belgium and from 23.55% to 56.18% with BYDV-PAV-CN. Significant differences of percentages of transmission between the populations with BYDV-PAV-Belgium and BYDV-PAV-CN were observed. Buchnera and seven S-symbionts (PASS, PABS, PAUS, Rickettsia, Spiroplasma, Wolbachia and Arsenophonus) universally found in different local population with different infection frequencies. The endosymbionts in most and least efficient vector aphid clones were selectively eliminated by antibiotic, the BYDV transmission efficiencies were inhibited. Compared with the result of western blot, Buchnera plays an import role on BYDV transmission. Finally, according to the direct toxic effect of lectins on insect biological parameters but also to the potential competitive effect of lectins towards viral particles in virus transmission by aphids, GNA and PSL incorporated in an artificial diet, the BYDV transmission efficiencies were inhibited. The inhibition rate of GNA-treatment reached to 46.63% in STY-BYDV-PAV-CN treatment and PSL-treatment was 46.47% in STY-BYDV-PAV-CN treatment. It is demonstrated that lectins represent a very promising protein to control aphid pest damages in crops. [less ▲]

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See detailEtude d’impact de l’apprentissage par la vidéo et la radio rurale sur la transformation à petite échelle du riz local au Bénin
Zossou, Enangnon ULg

Doctoral thesis (2013)

La culture du riz a été reconnue par les Nations Unies comme l'une des principales sources de nourriture pouvant favoriser la sécurité alimentaire, l'éradication de la pauvreté et la réalisation à l ... [more ▼]

La culture du riz a été reconnue par les Nations Unies comme l'une des principales sources de nourriture pouvant favoriser la sécurité alimentaire, l'éradication de la pauvreté et la réalisation à l'échelle internationale des objectifs du Millénaire. Au Bénin, beaucoup de réformes ont été faites dans la filière riz pour accroître la production nationale. La production et la transformation du riz sont des tâches souvent réparties sur la base du sexe avec les femmes en grande partie responsables des opérations post-récoltes. La transformation du riz au Bénin est généralement faite à petite échelle et constitue une source non négligeable de revenus. Dans le but d’améliorer l’apprentissage au sein des acteurs du riz, des chercheurs et des partenaires, en collaboration avec les producteurs et transformateurs de riz au Bénin, ont élaboré une série de vidéos sur la production de riz et les activités post-récoltes. Les vidéos ont été utilisées comme une ressource à partir de laquelle des scripts radiophoniques ont été développés. Cette étude s’intéresse à l'impact de l’apprentissage par les vidéos et émissions radiophoniques (relatives à la post-récolte du riz) sur (i) les pratiques des transformateurs, (ii) les caractéristiques physiques et les propriétés de cuisson du riz local, (iii) la valorisation du riz local par les consommateurs et (iv) le capital financier, social et humain des transformateurs du riz local. L'étude a été menée dans le sud et le nord du Bénin avec 240 transformateurs de riz et 270 femmes consommatrices de riz ; et dans le centre du Bénin avec 160 femmes étuveuses de riz et 100 consommatrices de riz. En plus des interviews structurées et des fiches de suivi hebdomadaire, l'évaluation participative utilisant l'approche des moyens d'existence durable a été utilisée pour apprécier l’état du capital financier, social et humain des transformateurs de riz. Pour l’analyse des données, nous avons utilisé le modèle de la double différence « Diff-in-Diff », le modèle de régression OLS (Ordinary Least Squares), le modèle de régression de Poisson et l'effet moyen de traitement (ATE). Pour apprécier la volonté des consommateurs béninois à payer pour le riz local, nous avons mené des enchères expérimentales dans les marchés au nord, centre et sud du Bénin. Avant l’apprentissage par la vidéo ou la radio, les transformateurs de riz avaient moins accès aux sources formelles d'apprentissage et avaient des pratiques peu recommandées. Les méthodes traditionnelles ne conduisant pas à une bonne qualité de riz étaient prédominantes. Par conséquent, l'état général des capitaux des moyens d’existence était faible. Les projections publiques des vidéos et les émissions radiophoniques ont été très bien appréciées par les transformateurs de riz dans les zones d’étude. La radio rurale semble être moins efficace que la vidéo et doit être utilisée avec précaution dans la vulgarisation agricole. Les animateurs des radios rurales ont en effet besoin d’une connaissance suffisante des sujets agricoles et de se familiariser avec le vernaculaire agricole local afin de diffuser des messages appropriés. Les scripts radiophoniques développés à partir des vidéos aident à relever ces défis. Les transformateurs de riz qui ont suivi les vidéos et les émissions radiophoniques ont amélioré leurs pratiques et leur créativité en développant des technologies appropriées à leur environnement. Ce qui a eu un impact positif sur la qualité du riz local transformé ; améliorant ainsi le prix sur le marché. Par rapport au prix du riz étuvé traditionnel, les consommateurs sont prêts à payer un surplus de 9 à 27% pour avoir le riz étuvé avec des technologies d'innovation locale; et 25 à 34% pour avoir le riz étuvé avec la technologie améliorée. Comparativement aux offres du groupe témoin, la sensibilisation par la vidéo et la radio a augmenté respectivement les offres des consommatrices pour le riz étuvé avec la méthode améliorée de 23 à 47F CFA et de 9 à 18 F CFA. vi En 2012, on constate dans les villages vidéo une augmentation du pourcentage de transformateurs de riz qui font la vente dans les marchés régionaux ; ce qui constitue un indicateur de la bonne qualité du riz. Avec l’utilisation du modèle de l'ATE, nous notons pour le riz blanc qu'il n'y a pas eu un impact significatif de la radio sur les revenus parce que le message a été à un moment mal compris. La vidéo par contre a eu un impact significatif sur les revenus des transformateurs aussi bien pour le cas du riz blanc que pour celui du riz étuvé. L’impact de la vidéo sur les revenus des transformateurs de riz étuvé est pratiquement le double de ce qui a été noté dans le cas de la radio rurale. Les transformateurs de riz qui ont suivi la vidéo et les émissions radiophoniques ont perçu une amélioration significative au niveau de leur capital financier, social et humain. Des campagnes d'information sur les technologies améliorées de transformation du riz ont non seulement joué un rôle important au niveau des transformateurs de riz en améliorant la qualité de leurs produits ; mais aussi elles ont permis d’informer les consommateurs sur la valeur du produit final. Les résultats de la présente étude ont été certainement influencés par (i) l’approche participative utilisée lors de la réalisation des vidéos et des émissions radiophoniques ; (ii) le mode d’utilisation des vidéos, c’est-à-dire leurs projections publiques sur des écrans géants ; et (iii) l’utilisation des vidéos comme des ressources à partir desquelles les émissions radiophoniques ont été réalisées. D’autres projets utilisant la vidéo et la radio rurale pourraient ne pas avoir les mêmes résultats si les conditions précitées n’ont pas été remplies. Ce qui nécessite des études ultérieures quant à l’influence du mode de réalisation et d’utilisation des vidéos et émissions radiophoniques dans le monde rural sur leur efficacité et durabilité dans le temps. Dans un contexte de pauvreté généralisée, d’insécurité alimentaire, de fort taux de ruralité et de faible taux d’alphabétisation, l’utilisation dans la vulgarisation agricole de la vidéo et de la radio rurale (fondées sur les principes de base des approches participatives) constitue une opportunité pour favoriser l’accès général des populations rurales à l’information agricole. Ce qui constitue un potentiel pouvant promouvoir une agriculture durable en encourageant les innovations locales. Au regard de l’intérêt que présentent la vidéo et la radio rurale, des suggestions ont été faites à l’endroit de la recherche, du développement et des décideurs politiques afin qu’une attention particulière soit portée sur ces outils de communication dans la vulgarisation agricole. [less ▲]

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See detailStudy of CMV - plant - aphid interactions focusing on Myzus persicae in vegetable crops
Yin, Rongling ULg

Doctoral thesis (2013)

Myzus persicae aphid is a very polyphagous pest found on hundreds of host plants including several vegetable crops. Its role as virus potential vector was cited for many viruses including the ones found ... [more ▼]

Myzus persicae aphid is a very polyphagous pest found on hundreds of host plants including several vegetable crops. Its role as virus potential vector was cited for many viruses including the ones found in vegetable crops. Transmission efficiency of virus such as Cucumber mosaic virus (CMV), transmitted by M. persicae to vegetable crops is the most common model used in many researches. In a non-persistent manner, CMV particles bind on the top of aphid stylet and transmitted in a few minutes, with an efficiency affected by a number of factors, like virus strains, aphid species, source and recipient plant species, and plant species on which the aphid is maintained. Management of vector-borne plant diseases has presented a challenge because of complex dynamics and interactions of host plants, vectors and viruses within natural environment. Lectins as defense proteins in plants are present in large quantities in storage organs and seeds that are especially vulnerable to pathogens or pest insects (Peumans and Van Damme, 1995). Numerous reports in recent years have shown that lectins are toxic to various pest insects belonging to economically important insects such as Lepidoptera, Coleoptera, Diptera or Hemiptera in genetic engineered plants or artificial diets with lectins, which negatively affected the performances of pest insects. In the last decades, some plant lectins were shown to be toxic particularly to several aphids. Plant-aphid-virus interactions have been researched for several decades, and there are some important questions studied, and still being in process. Although there are reports on virus transmission, we focus on transmission efficiency affected by 8 geographic aphid species, virus strains and plant lectins, and finally we performed to get a better understanding of the virus-aphid interactions and to propose new insight of lectins in non-persistent virus transmission control in crop protection. [less ▲]

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See detailBelgian population exposed to furan: from analytical developments to risk assessment
Scholl, Georges ULg

Doctoral thesis (2013)

Since the acrylamide incident in 2002, food authorities such as EFSA, FDA, FAO and Belgian FFSA paid more attention to the food borne contaminants such as furan, glycidyl esters or nitrosamines. As a ... [more ▼]

Since the acrylamide incident in 2002, food authorities such as EFSA, FDA, FAO and Belgian FFSA paid more attention to the food borne contaminants such as furan, glycidyl esters or nitrosamines. As a consequence, authorities support scientific initiatives to gather information about these toxicants. The thesis was conducted in this framework and was specifically dedicated to the furan issue. The fundamental concept behind this work on furan was to include analytical developments, to determine its occurrence in Belgian food and to carry out a risk assessment of the Belgian population. The first section was dedicated to the development of a high sensitive analytical method able to report sub-parts-per-billion (ppb) levels in foodstuffs with the aim to limit the number of unreported results below of the limit of quantification (LOQ). A HS-SPME-GC-MS method has been developed and optimized using the experimental design approach. The developed method has been validated to fulfill the requirements of the European Commission decision regarding the validation of analytical method (2002/657/EC). The second section was dedicated to the achievement of a contamination survey of the foodstuffs available on the Belgian market with a restricted number of samples (n=496). A specific sampling plan was designed to cover every food matrices with regard to the more consumed and/or contaminated items. The analytical method developed in the first section was applied and 78% of results were reported above LOQ. We concluded to a ubiquitous contamination of our food chain with specially high levels in coffee, roasted and long-time cooking foodstuffs. The third section was dedicated to the assessment of the risk linked to the furan ingestion by the Belgian population. A methodology involving the estimation of the furan daily intake (by both deterministic and probabilistic approach) and the calculation of the Margin of Exposure (MoE) was applied to 3 sub-populations namely Adults, Children and Toddlers. The adults and children assessments highlighted that almost none have a “High concern risk level” (MoE < 100), that the risk for health tends to be low (median MoE for adults 5486; median MoE for children 5079), and that the risk for children is slightly higher than for adults. For infants, the assessment showed a higher risk (median MoE 817) compared to children and adults. However, this finding has to be tempered by the current limited knowledge of the furan toxicity for toddlers. In addition, the size of the datasets available for this work was low and limited to ready-to-eat baby foods, which are known to be more contaminated than home-made baby food. It gives however the first benchmark for Belgian infants exposed to furan. Thus, developing consumption survey for infants that are harmonized at European level, and basic research on furan toxicity for toddlers are necessary. [less ▲]

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See detailLa filière avicole de chair dans les zones périurbaines de Hanoï, Vietnam: situation économique et perspectives
Phan Dang, Thang ULg

Doctoral thesis (2013)

In Vietnam, the economic growth in recent years, has brought a strong demand for animal products consumption, particularly poultry meat. This research aims to better understand how the factors in the meat ... [more ▼]

In Vietnam, the economic growth in recent years, has brought a strong demand for animal products consumption, particularly poultry meat. This research aims to better understand how the factors in the meat-producing poultry sector adapt to current economic conditions in Hanoi suburbs by analyzing agricultural product chains. These studies have conducted two surveys from October 2008 to November 2010. As results, three meat-producing poultry systems have been identified. The industrial farms with contract farming have obtained the most important net income (from 28,923,000 VND per farm per year for colored chickens to 67,341,000 VND for standard chickens). The productivity is also very high. The mortality rate is 5 % for colored and standards chickens. But number of these industrial farms is still limited due to a large capital investment and the limitation of available land. The cost price of broiler production is really competitive compared to other chickens. Meat-producing poultry farms on semi-industrial scale have obtained weak productivity. The mortality rate is 13 % for colored chickens and ducks. Agricultural by-products of the farms are generally used for poultry. The net income has varied from 14,279,000 VND per farm per year with colored chickens to 25,424,000 VND with standard chickens. Backyard poultry farms are widely practiced in household farms with low investment. The productivity is very weak. The mortality rate of chickens is high (19 %). The net income of poultry production is also weak in households (4,432,000 VND per farm per year, or equivalent to 9 % of net income in farms). Majority surveyed farms raised various species of chickens and ducks. This is to permit a better risk management and responds to varied market demand according to different consumer tastes. Poultry meat production also aims to satisfy a significant share of the demand for self-consumption with chickens and ducks in small households. [less ▲]

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See detailLe dumping social dans l'Union européenne : Étude à l'aune du droit primaire et de la directive détachement
Defossez, Alexandre ULg

Doctoral thesis (2013)

La dénonciation du risque de « dumping social » que fait courir le processus d’intégration économique européen aux systèmes sociaux des États membres apparaît, en filigrane, tout au long de l’histoire de ... [more ▼]

La dénonciation du risque de « dumping social » que fait courir le processus d’intégration économique européen aux systèmes sociaux des États membres apparaît, en filigrane, tout au long de l’histoire de l’édification du marché intérieur . Les exemples récents de telles dénonciations ont fait l’objet d’une forte médiatisation, qui ne doit toutefois pas masquer l’ancienneté du risque ainsi dénoncé . Plusieurs affaires ont ainsi défrayé la chronique et ont poussé citoyens et syndicats à interpeller les responsables politiques, européens et nationaux. L’objet de cette étude est né de cette interrogation : le risque de dumping social étant une crainte permanente au sein de l’Union, une crainte elle-même associée à la construction et à l’approfondissement du marché intérieur européen, quels mécanismes juridiques le législateur européen a mis (ou pas) en place afin d’en contrer les effets ? L’objectif de cette recherche est, plus précisément, d’identifier la manière dont ces débats, récurrents, ont conduit le législateur européen à adopter des mécanismes de lutte contre le dumping social et d’évaluer les effets des mécanismes ainsi mis en place. Il ne s’agira donc pas d’analyser comment l’espace européen s’intègre lui-même dans le tissu économique mondial et peut, à cette occasion, se protéger contre le risque de concurrence sociale induit par les échanges avec le reste du monde . Le dumping social intra-européen, et la manière dont l’Union européenne cherche (ou pas) à s’en prémunir, forme le cœur, plus modeste, de cette étude. [less ▲]

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See detailCaractérisation structurale des protéines et de complexes non covalents par "footprinting" et MALDI In-Source Decay
Lemaire, Pascale ULg

Doctoral thesis (2013)

La fragmentation de protéines entières dans la source d’un spectromètre de masse (« In-Source Decay » ou « ISD ») lors de l’ionisation-désorption laser assistée par une matrice (« Matrix-Assisted Laser ... [more ▼]

La fragmentation de protéines entières dans la source d’un spectromètre de masse (« In-Source Decay » ou « ISD ») lors de l’ionisation-désorption laser assistée par une matrice (« Matrix-Assisted Laser Desorption/Ionisation » ou « MALDI ») permet leur identification. On parle alors de méthode « Top-down », par opposition à l’approche « Bottom-up » dans laquelle les protéines sont d’abord digérées en peptides. Cette fragmentation étant rapide, elle peut être considérée comme une technique intéressante pour analyser les régions d’une protéine qui sont accessibles au solvant dans des expériences qualifiées de « footprinting ». En effet, les zones non accessibles soit en raison de la conformation d’une protéine soit suite à son interaction avec un ligand seront protégées. En plus d’être rapide, la fragmentation par MALDI-ISD ne nécessite qu’une faible quantité d’échantillon. Les spectres de masse obtenus sont principalement composés d’ions fragments monochargés résultant de la rupture de la liaison peptidique, ce qui permet leur interprétation en termes de séquence. Cette technique peut donc être intégrée dans une stratégie permettant d’obtenir rapidement des données qualitatives concernant la topologie d’une protéine. Dans ce manuscrit, la fragmentation par MALDI-ISD a été utilisée pour localiser les sites qui sont accessibles au solvant et par là, les sites protégés par repliement ou par interaction de protéines avec des ligands non covalents. Les méthodes de footprinting qui utilisent des techniques de marquage oxydatif ou de marquage par le deutérium en solution ont été utilisées. La fragmentation ISD elle même peut être vue comme une méthode de footprinting directe, n’utilisant pas de marquage préalable de protéines en solution. Cette analyse repose sur l’étude des modifications d’accessibilité des groupes carbonyles en comparant le profil de fragmentation des protéines lors d’un changement structural ou lors de leur interaction avec un ligand. Footprinting oxydatif analysé par MALDI-In-Source Decay. N’ayant jamais été exploitée pour l’analyse des données de footprinting oxydatif, la fragmentation par MALDI-ISD a été utilisée pour localiser les sites d’oxydation du peptide amyloïde Aβ(1-40). Une étude de la faisabilité de détection de produits d’oxydation ainsi que l’identification des chaînes latérales oxydées a tout d’abord été effectuée en oxydant le peptide Aβ(1-40) dans une solution de peroxyde d’hydrogène. La modification des profils de fragmentation ISD du peptide oxydéa été expliquée par la probabilité d’intervention de compétitions de réactions d’addition radicalaire et de transfert de charge. Cet effet sur l’aspect global des spectres de masse n’affecte cependant que le rendement des oxydations et non leur localisation. L’oxydation du peptide Aβ(1-40) résultant de son interaction spécifique avec le fer a permis de valider l’utilisation de la méthode pour la localisation des sites d’oxydation. Une corrélation entre l’identité des résidus oxydés et les données d’interaction du métal fournies par la littérature a pu être établie. Le peptide Aβ(1-40) constitue une cible thérapeutique potentielle étant donné son implication dans la toxicité cellulaire observée dans la maladie d’Alzheimer. Les sites d’interaction de molécules bi-aromatiques susceptibles d’inhiber potentiellement l’agrégation du peptide devaient au départ être identifiés par la méthode d’échange hydrogène/deutérium (« hydrogen/deuterium exchange » ou « HDX ») analysé par MALDI-ISD. Les premières expériences ont cependant révélé que les fonctions amides du peptide étaient caractérisées par des cinétiques d’échange isotopique intrinsèques rapides. Le marquage oxydatif par des radicaux hydroxyles produits par photolyse laser du peroxyde d’hydrogène a été la stratégie alternative de choix pour l’étude d’interaction du peptide avec un ligand bi-aromatique leader. Une diminution de la proportion de la forme mono-oxydée du peptide en présence du ligand est observée sur les spectres de masse MALDI. L’identité de l’acide aminé oxydé n’a malheureusement pas été élucidée, cependant, la méthionine 35 pourrait être l’acide aminé oxydé. Footprinting utilisant le deutérium analysé par MALDI-In-Source Decay. La matrice MALDI 1,5-DAN qui est pourtant connue pour présenter un potentiel réducteur élevé, favorisant la production d’ions fragments par MALDI-ISD, n’a cependant jamais été utilisée pour l’analyse des données d’échange H/D de protéines. Les cinétiques d’échange H/D intrinsèques rapides du peptide Aβ(1-40) ont permis de l’utiliser comme modèle pour évaluer l’utilisation de la matrice 1,5-DAN pour le couplage de l’échange H/D à la spectrométrie de masse MALDI. L’homogénéité des profils d’échange isotopique et le degré de rétroéchange moyen observé sur un spot MALDI ont été examinés en comparant les résultats obtenus avec la matrice 1,5-DAN à ceux obtenus avec trois matrices MALDI plus communes. Les résultats révèlent qu’outre son potentiel réducteur élevé, la matrice 1,5-DAN possède une cinétique de cristallisation très rapide. Ceparamètre facilite la mise au point de protocoles robustes. La matrice 1,5-DAN a été utilisée pour l’analyse des données d’échange H/D de la structure tertiaire de l’ubiquitine dans des conditions natives. Les résultats obtenus en ISD sont en accord avec des données préalablement obtenues en ETD et RMN. Cet accord entre les résultats a permis de valider la méthode proposée. Une seconde étude basée sur la caractérisation de structures secondaires a été effectuée avec la β- endorphine. Les profils d’échange H/D de la β-endorphine sous une structure secondaire hélicoïdale, induite par le méthanol, ont été comparés à ceux obtenus lorsque le peptide est sous une conformation en pelote statistique non périodique. Le peptide sous sa conformation hélicoïdale présente systématiquement une accessibilité au solvant plus réduite. Les résultats obtenus sont en accord avec les prédictions qualitatives, sur base de la polarité des acides aminés, de formation d’hélices α induite par le méthanol. Footprinting utilisant la voie de fragmentation radicalaire en MALDI-In- Source Decay. Les résultats de marquage oxydatif du peptide Aβ(1-40) analysé par MALDI-ISD ont révélé une variation considérable de l’intensité relative de signaux ioniques caractéristiques d’une fragmentation induite par les radicaux hydrogènes de la matrice. Le profil de fragmentation est modifié au niveau de l’ion fragment caractérisant la tyrosine 10 du peptide. Ce résidu, selon la littérature, est impliqué dans l’interaction du peptide avec le fer. Nous avons donc évalué l’utilisation de la fragmentation ISD comme méthode de footprinting reposant sur l’étude de l’accessibilité des groupes carbonyles des protéines aux radicaux hydrogènes de matrice. Une comparaison des spectres de fragmentation ISD du lysozyme humain natif ou dénaturé puis alkylé en solution a été réalisée. Les profils de fragmentation ISD des deux conformères du lysozyme sont différents. En particulier, les ions fragments c18, c19 et z14 ont fourni une information pertinente sur la différence d’accessibilité des deux conformères visà- vis des radicaux hydrogènes. Cependant, la différence d’intensité de l’ion fragment z14 observée entre les deux conformères peut aussi être expliquée par un effet de l’alkylation de la cystéine 116 du lysozyme sur le clivage du lien N—Cα du côté C-terminal du résidu. Une étude supplémentaire a été réalisée avec un complexe formé entre le lysozyme humain et un fragment d’anticorps de camélidé, cAb-HuL6. L’objectif était de détecter une modification éventuelle du profil de fragmentation ISD lors de la complexation du lysozyme. Les intensitésrelatives des ions fragments caractérisant des acides aminés de l’interface du complexe lysozyme—cAb-HuL6 sont peu modifiées par rapport à celles du complexe Aβ(1-40)—Fe. Cette observation a conduit la conclusion que l’utilisation de la fragmentation ISD comme méthode de footprinting dépend non seulement de la stabilité du complexe (constante d’affinité, Kaff, et constante de vitesse de dissociation, kd) et des conditions expérimentales utilisées (solvant, additifs et matrice), mais aussi du type d’interactions impliquées dans la formation du complexe. [less ▲]

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See detailTopology optimization of electrostatic MEMS including stability constraints
Lemaire, Etienne ULg

Doctoral thesis (2013)

Among actuation techniques available for MEMS devices, electrostatic actuation is often used as it provides a short response time and is relatively easy to implement. However, these actuators possess a ... [more ▼]

Among actuation techniques available for MEMS devices, electrostatic actuation is often used as it provides a short response time and is relatively easy to implement. However, these actuators possess a limit voltage called pull-in voltage beyond which they are unstable. The pull-in effect, can eventually damage the device since it can be impossible to separate the electrodes afterward. Consequently, pull-in phenomenon should be taken into account during the design process of electromechanical microdevices to ensure that it is avoided within utilization range. In this thesis, a topology optimization procedure which allows controlling pull-in phenomenon during the design process is developed. A first approach is based on a simplified optimization problem where the optimization domain is separated from the electrical domain by a perfectly conducting material layer making the optimization domain purely mechanical. This assumption reduces the difficulty of the optimization problem as the location of the electrostatic forces is then independent from the design. However, it allows us to develop and validate a design function based on pull-in voltage in the framework of a topology optimization problem. Nevertheless, in some applications, the developed pull-in voltage optimization procedure suffers from design oscillations that prevent from reaching solution. In order to solve this issue, we propose to investigate an alternative approach consisting in formulating a linear eigenproblem approximation for the nonlinear stability problem. The first eigenmode of the proposed stability eigenproblem corresponds to the actual pull-in mode while higher order modes allow estimating upcoming instability modes. By including several instability modes into a multiobjective formulation, it is possible to circumvent the oscillations encountered with pull-in voltage design function. Next, the possibility to generalize the pull-in optimization problem by removing the separation between optimization and electrostatic domains is studied. Unlike the original method, the dielectric permittivity has then to depend on the pseudo-density like the Young Modulus to represent the different electrostatic behavior of void and solid. Additionally, in order to render perfect conducting behavior for the structural part of the optimization domain, a fictitious permittivity is also introduced into the material model. Difficulties caused by non-physical local instability modes could be solved by using a force filtering technique which removes electrostatic forces originating from numerical inaccuracies of the modeling method. Thanks to these improvements, the optimization problem based on the pull-in design function can be generalized. As a result, the optimizer is able to adapt the electrostatic force distribution applied on the structure which leads to a higher efficiency of the optimal device. In order to illustrate the interest of the pull-in voltage design function, the pull-in voltage optimization problem is merged with the electrostatic actuator optimization problem. In this new optimization problem, the pull-in voltage does not appear anymore in the objective function but in a constraint which prevents the pull-in voltage to decrease below a given minimal value. Firstly, the new optimization problem is compared to the basic electrostatic actuator design procedure on basis of a numerical application. The pull-in voltage constraint proved to be very useful since it prevents the pull-in voltage of the mechanism to decrease below the driving voltage during the optimization process. Finally, the effect of geometric nonlinearity modeling is also tested on numerical applications of our optimization procedure. [less ▲]

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See detailReproduction en groupe chez l'Hirondelle rustique (Hirundo rustica):stratégies individuelles et interactions sociales
Dardenne, Sophie ULg

Doctoral thesis (2013)

The fact that some individuals reproduce close to other adults of the same species, and particularly the origin and maintenance of a sometimes high variation of breeding group sizes, are central themes in ... [more ▼]

The fact that some individuals reproduce close to other adults of the same species, and particularly the origin and maintenance of a sometimes high variation of breeding group sizes, are central themes in evolutionary ecology and behavioral biology. The recent approach to these issues is no more to identify the consequences of group living (i.e. the costs and benefits for the group), but to assess the environmental signals used by individuals to choose their breeding habitat and their mate. These signals can be of two types: cues of the habitat itself, and those of the social environment. The selection of breeding habitat has deep consequences on seasonal reproductive success, and each individual thus has to choose the environment that best matches to its own capacity and individual needs, is such a way that the chosen environment will enable it to maximize its fitness. Therefore, the characteristics of individuals, whether in terms of intrinsic characteristics such as morphology or age, but also their behavior, play an important role in habitat selection. The causes of the variation in breeding group sizes are still unclear, and it seems appropriate to assess whether breeding habitat selection is based on habitat characteristics, individual characteristics, or a combination of both, and to assess the relative roles of each habitat or individual characteristic in that process. To that purpose, we studied a wild population of Barn Swallows (Hirundo rustica) during three breeding seasons (May to September 2009 to 2011), in a rural area of southern Belgium. We collected banding, genetic, and behavioral data, and carried out several behavioral tests. This semi-colonial species forms breeding colonies of variable sizes. It was suggested that barn swallows choose their breeding habitat primarily on the basis of habitat signals such as the presence of old nests, and not on the basis of social cues such as the reproductive success of conspecifics. However, we observed in the study population that the breeding habitat was not saturated: suitable places remain unoccupied some years, while we observed grouping in others, including cases where new nests had to be built in already occupied rooms. This indicated a voluntary aggregation. We showed that breeding habitat choice results in part from the selection of intrinsic characteristics of the habitat. The importance of these parameters for breeding habitat choice however is not dominant, and their variation can only explain a small part of the variation in room occupancy. This choice in fact is also driven by the characteristics of the social environment, i.e. the presence and the behavior of conspecifics. The major result of this work shows that the choice of a given social environment depends on individual traits, and will impact the individual’s behavior, for instance its use of alternative strategies of reproduction. Indeed, we have shown in this thesis that the choice of a social context is an active decision, at least for some individuals. In consequence, individuals are not distributed along the gradient of social environments independently of their morphology and of their personality. Large colonies host birds with higher neophobia and higher social tolerance. Group living is likely to provide some fitness rewards but it bears also some costs that were assessed in this thesis. Several elements were assessed: the cooperation among adults (for breeding and nest defense); the use of alternative strategies of reproduction like extra-pair copulations and brood parasitism (cuckoldry); the prevalence of ectoparasites; and the realized annual fitness. We showed that cooperation is associated with group living, and is probably a bonus for those individuals that decide to breed in groups, while ectoparasites are there more frequent. We did not identify any particular pattern of association between the presence of extra-pair or parasite brood in a nest and the breeding group size, both being common in the colonies and in isolated nests. It seems however that the use of these alternative mating strategies is related with the social environment chosen: females use more often cuckoldry when isolated than when in large colonies, and males have more extra-pair offspring when they breed in colonies. Finally, although they adopt contrasting strategies, barn swallows that breed in colony or isolated have all similar annual reproductive success. We suggest that the social benefits of group living (or alternatively those of isolation) can be evaluated by the birds when selecting their breeding habitat, and we propose that the variability of these benefits and costs for birds with contrasting phenotypes (morphology, temperament) is involved in the maintenance of the semi-colonial character of this species. In conclusion, this thesis has shown the existence of individuality in the maintenance of variation in group sizes of reproduction. The question of "why individuals reproduce group" remains however largely open, but our study has provided new elements on this topic. La reproduction d’individus à proximité d’autres adultes de la même espèce et plus particulièrement l’origine et le maintien de la variation de la taille des groupes de reproduction chez les espèces semi-coloniales sont des thèmes centraux en écologie évolutive et en biologie comportementale. L’approche récente de ces thèmes consiste non plus à identifier les conséquences de la vie en groupe (coûts et bénéfices pour le groupe), mais à évaluer quels signaux de l’environnement sont pris en compte par l’individu lors du choix de son habitat de reproduction ou de son partenaire. Ces signaux sont de deux types: signaux de l’habitat et signaux de l’environnement social. Le comportement de sélection de l’habitat durant la saison de reproduction ayant des conséquences sur le succès reproducteur saisonnier, chaque individu devrait idéalement opter pour l’environnement qui regroupe les paramètres lui permettant de maximiser sa fitness au vu de ses qualités et besoins individuels. Dès lors, les caractéristiques des individus, que ce soit des caractéristiques intrinsèques telles que la morphologie ou l’âge, mais également leur comportement jouent un rôle prépondérant dans la sélection d’un habitat. Les causes de la variation observée pour la taille des groupes de reproduction sont peu claires et il parait opportun d’évaluer si le choix de l’habitat repose sur des caractéristiques de l’habitat, des individus, ou d’une combinaison des deux et d’évaluer quel est le rôle relatif de chacun de ces éléments. A cette fin, nous avons étudié une population naturelle d’Hirondelles rustiques (Hirundo rustica), que nous avons suivie pendant trois saisons de reproduction (de mai à septembre 2009 à 2011), dans une région rurale du sud de la Belgique. Nous avons collecté pour cette population des données de baguage, des données génétiques et comportementales, et effectué différents tests comportementaux. Cette espèce est qualifiée de semi-coloniale car elle présente une gamme variable de taille des colonies de reproduction. Il a été proposé précédemment que cette espèce base son choix d’habitat principalement sur des signaux de l’habitat tels que la présence d’anciens nids plutôt que sur base d’indices sociaux comme le succès reproducteur des conspécifiques. Cependant, nous avons observé que l’habitat de la population étudiée n’était pas saturé, des sites adéquats pour la reproduction n’étant pas occupés certaines années. A l’inverse, nous avons observé le regroupement dans certains autres locaux, avec parfois même la construction de nouveaux nids dans des pièces déjà occupées. Cela indique que l’on se trouve en présence d’une agrégation volontaire. Nous montrons que le choix d’un habitat de reproduction s’effectue en partie sur une sélection de caractéristiques intrinsèques de l’habitat. L’importance de ces paramètres intrinsèques ne semble cependant pas prépondérante puisque leur variation ne permet d’expliquer qu’une part faible de la variation des taux d’occupation des locaux. En fait, le choix fait également intervenir des caractéristiques sociales de l’environnement de reproduction, i.e. la présence et les comportements des conspécifiques. Le résultat majeur de ce travail montre que le choix d’un environnement social donné est fonction des caractéristiques de l’oiseau, et qu’il a un impact sur les comportements exhibés par les individus, comme par exemple la pratique de stratégies alternatives de reproduction. Nous avons montré dans cette thèse que le choix d’un environnement social de reproduction s’effectuait de manière active, au moins pour une partie des individus. En conséquence, les individus ne sont pas distribués dans le gradient des environnements sociaux disponibles indépendamment de leurs caractéristiques morphologiques et de leur personnalité. Ainsi, les grandes colonies abritent des individus à néophobie élevée et à haute tolérance sociale. La vie en groupe est susceptible d’apporter certains bénéfices de fitness mais a également des coûts. Plusieurs de ces coûts et bénéfices ont été évalués: la coopération entre les adultes (pour l'élevage des jeunes et de la défense du nid), l'utilisation de stratégies alternatives de reproduction comme les copulations hors couple (EPC) et le parasitisme de nichée, la prévalence des ectoparasites, et le succès reproducteur annuel. Nous avons montré que la coopération est associée à la vie de groupe et constitue probablement une prime pour les oiseaux qui décident de se reproduire dans les groupes, où la fréquence des ectoparasites est plus élevée. Nous n'avons pas relevé de motif particulier d'association entre la présence dans un nid de poussins issus d’EPC ou du parasitisme de nichée et la taille du groupe de reproduction, les deux étant commun dans les colonies comme dans les nids isolés. Il semble toutefois que l'utilisation de ces stratégies alternatives soit en relation avec l'environnement social choisi: les femelles utilisent plus souvent le parasitisme lorsqu'elles sont isolées que lorsque dans les grandes colonies, et les mâles ont plus de progéniture extra-couple quand ils se reproduisent en colonies. Au final, même si elles adoptent des stratégies contrastées, les hirondelles qui nichent en colonie ou isolées ont toutes un succès reproducteur annuel similaire. Nous suggérons que les avantages sociaux de la vie de groupe (ou encore ceux de l'isolement) peuvent être évalués lors de la sélection de l'habitat de reproduction, et nous proposons que la variabilité de ces avantages pour les oiseaux avec des phénotypes contrastés (en termes de morphologie ou de tempérament) soit impliquée dans le maintien du caractère semi-colonial de cette espèce. En conclusion, cette thèse a montré l’importance de l'individualité dans le maintien de la variation dans la taille des groupes de reproduction. La question du « pourquoi les individus reproduisent groupe » reste cependant largement ouverte, mais notre étude a fourni de nouveaux éléments sur ce sujet. [less ▲]

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See detailContributions to Monte Carlo Search
Lupien St-Pierre, David ULg

Doctoral thesis (2013)

This research is motivated by improving decision making under uncertainty and in particular for games and symbolic regression. The present dissertation gathers research contributions in the field of Monte ... [more ▼]

This research is motivated by improving decision making under uncertainty and in particular for games and symbolic regression. The present dissertation gathers research contributions in the field of Monte Carlo Search. These contributions are focused around the selection, the simulation and the recommendation policies. Moreover, we develop a methodology to automatically generate an MCS algorithm for a given problem. For the selection policy, in most of the bandit literature, it is assumed that there is no structure or similarities between arms. Thus each arm is independent from one another. In several instances however, arms can be closely related. We show both theoretically and empirically, that a significant improvement over the state-of-the-art selection policies is possible. For the contribution on simulation policy, we focus on the symbolic regression problem and ponder on how to consistently generate different expressions by changing the probability to draw each symbol. We formalize the situation into an optimization problem and try different approaches. We show a clear improvement in the sampling process for any length. We further test the best approach by embedding it into a MCS algorithm and it still shows an improvement. For the contribution on recommendation policy, we study the most common in combination with selection policies. A good recommendation policy is a policy that works well with a given selection policy. We show that there is a trend that seems to favor a robust recommendation policy over a riskier one. We also present a contribution where we automatically generate several MCS algorithms from a list of core components upon which most MCS algorithms are built upon and compare them to generic algorithms. The results show that it often enables discovering new variants of MCS that significantly outperform generic MCS algorithms. [less ▲]

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See detailBody condition score and milk fatty acids as indicators of dairy cattle reproductive performances
Bastin, Catherine ULg

Doctoral thesis (2013)

Improving cow fertility by means of genetic selection has become increasingly important over the last years in order to overcome the decline in dairy cow fertility that has taken place over the past ... [more ▼]

Improving cow fertility by means of genetic selection has become increasingly important over the last years in order to overcome the decline in dairy cow fertility that has taken place over the past decades. However, fertility traits are difficult to measure and have low heritabilities. Consequently, indicator traits are of interest for breeding value estimation for fertility especially if these traits are easier to measure, have higher heritabilities and are well correlated with fertility. Therefore, the objective of this thesis was to investigate the opportunity of using either fatty acid contents (FA) in milk predicted by mid-infrared spectrometry or body condition score (BCS; i.e., a subjective measure of the amount of metabolizable energy stored in a live animal) as indicator traits of female fertility. Research conducted on BCS and fertility records from Canadian Ayrshire and Holstein cows indicated that BCS was heritable and showed a low to moderate favorable genetic correlation with fertility suggesting that higher BCS would be related to better fertility. Also, based on results obtained on Walloon data, selection for higher nadir BCS was suggested as useful to change BCS curve over the lactation and improve fertility. Furthermore, using records from Walloon Holstein cows, FA were demonstrated to be moderately heritable. Genetic correlations among FA and fertility were low to moderate and changed over the lactation. Overall, the pattern of genetic correlations of fertility with BCS and FA substantiated the known relationship between energy balance status and fertility. Body fat mobilization in early lactation induces BCS loss. Also, the release of long-chain FA in milk from the body fat mobilization inhibits de novo FA synthesis in the mammary gland, leading to a decrease of short- and medium- chain FA. To conclude, this research has shown that traits based on BCS and milk FA profile fulfill criteria to be considered as indicator traits to improve indirectly fertility of dairy cows. [less ▲]

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See detailEpigenetic regulation of angiogenesis
Shiva Shankar, Thammadihalli Veerasangaiah ULg

Doctoral thesis (2013)

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See detailAnalysis of solar air-conditioning systems and their integration in buildings
Thomas, Sébastien ULg

Doctoral thesis (2013)

Due to economical and environmental concerns, the energy e fficiency of buildings nowadays has proven to play an increasingly important role. To satisfy the occupants comfort, the cooling of buildings ... [more ▼]

Due to economical and environmental concerns, the energy e fficiency of buildings nowadays has proven to play an increasingly important role. To satisfy the occupants comfort, the cooling of buildings generally involves a considerable consumption of electricity. Solar radiation, which is a free and renewable resource, is linked to the cooling needs of buildings. This work consists in the evaluation, from an energy-saving and economical point of view, of a potential use of solar energy for air-conditioning in residential and o ffice buildings. It includes an integral approach of solar air-conditioning, involving the analysis of the buildings cooling needs, the cold production devices, the solar collector fields and climates. This analysis is supported by simulations and experimental setups. The study of solar air-conditioning systems already available on the market or in laboratories reveals their operational principles as well as their main performance indicators. Two main solar cooling paths are investigated: a thermal and a photovoltaic conversion of solar energy. Besides this, the performance of the entire air-conditioning system broadens the question of the energy performance to the interactions between the diff erent parts of the system. The building thermal loads (heating, cooling, domestic hot water) of some theoretical residential and o ffice buildings are computed in a part of this work dealing with the influence of the comfort model, the building energy performance level and the climate. What comes across through this analysis is that, the location of the buildings put aside, the cooling load is greatly influenced by the envelope thermal performance and the internal gains. The cooling systems involving absorption or adsorption or vapour compression chiller cooling machines are simulated for the previously defi ned building cases. The use of solar energy through thermal collectors for heating meets higher primary energy savings than for cooling. In all cases, the thermally driven system achieves a lower energy and economical performance than a vapour compression chiller partially supplied with a photovoltaic field. Some real scale testing of solar air-conditioning systems was carried out in Arlon (Belgium). A thermally driven adsorption chiller and a vapour compression chiller with a photovoltaic grid-connected fi eld were operated during the cooling season. The measurements made during this experiment and their analysis manage to discover every thermal and electrical energy flows of the systems leading to a new adsorption chiller model. Concerning the comparison with the simulations, the main point of interest is the consumption of electricity dedicated to thermally driven systems, which is two times higher in real scale conditions. The results obtained from the monitoring campaigns corroborate the simulation results about system comparison. [less ▲]

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See detailO2: Dr Jekyll and Mr Hyde in symbiotic dinoflagellates (Symbiodinium) from reef-building corals
Roberty, Stéphane ULg

Doctoral thesis (2013)

Coral reefs are among the most beautiful and complex of all ecosystems on Earth. Although they cover less than 1% of the world’s oceans area, this marine ecosystem harbors a huge biodiversity and is vital ... [more ▼]

Coral reefs are among the most beautiful and complex of all ecosystems on Earth. Although they cover less than 1% of the world’s oceans area, this marine ecosystem harbors a huge biodiversity and is vital to human society and industries. The foundation of coral reefs relies on the fragile mutualistic relationship between reef-building corals and their photosynthetic dinoflagellates of the genus Symbiodinium. However, this symbiosis is highly sensitive to environmental or anthropogenic disturbances and may be disrupted, thus leading to the coral bleaching phenomenon. It has been reported that the initial steps of this process are linked to photosynthesis and the antioxidant network in Symbiodinium. However the nature of the cellular mechanisms leading to the generation of reactive oxygen species and to the disruption of the symbiosis is not completely unraveled. Therefore, this study aimed to highlight the existence of photosynthetic alternative electron flows reducing molecular oxygen and the way by which they can induces an oxidative stress, in four Symbiodinium strains belonging to three different clades. Joint measurements of oxygen evolution, PSI and PSII activities by chlorophyll a fluorescence and spectrophotometric measurements allowed us to demonstrate that photoreduction of oxygen by the so-called Mehler reaction is the main electron sink at the onset of photosynthesis and during steady state photosynthesis. When Symbiodinium cells were exposed to high light conditions, the Mehler reaction and the ascorbate-glutathione cycle (water-water cycle) acted as a safety valve and drained up to 50% of the electrons from PSII, protecting it from photoinhibition and dissipating rapidly the excess photon energy by downregulation of PSII. As long as the WWC efficiency was maintained in the chloroplasts of Symbiodinium, ROS generated as a by-product of the Mehler reaction did not significantly damage target molecules and induced an acclimatory response through up-regulation of enzymes involved in the antioxidant response (superoxide dismutase, ascorbate peroxidase, glutathione reductase). Nevertheless, when cells were exposed to light stress and elevated temperature (33°C), the WWC supported 75% of the electrons coming from PSII. This increase generated twice more H2O2 than during the treatment at 26°C and resulted in the inactivation of target enzymes of the WWC. Therefore, this means that under these conditions the photoprotective functions of the WWC can no longer be maintained, thus opening the way to ROS accumulation and to the induction of coral bleaching.We found that the response to oxidative stress differed between and within Symbiodinium clades. Symbiodinium clade A was less sensitive to the chemical induced oxidative stress than the others investigated strains. These variations are most likely related to their geographic origin, their thermal history, as well as to their physiological adaptations to the local environment. They may contribute to the explanation of why coral colonies and coral species have been found to differ in their susceptibilities to bleach. However, although the antioxidant response differs to some extent, some common traits were conserved. Among them, Diatoxanthin, a xanthophyll pigment involved in the non-photochemical quenching process could also have an antioxidant function. In addition, it seems that the ubiquitin-proteasome pathway is involved in the antioxidant response by eliminating carbonylated protein. [less ▲]

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See detailOptimal design of a CO2 capture unit with assessment of solvent degradation
Léonard, Grégoire ULg

Doctoral thesis (2013)

CO2 capture in power plants by absorption in amine solvents is a technology aiming at the reduction of CO2 emissions while simultaneously addressing the growth of the global energy demand. However, the ... [more ▼]

CO2 capture in power plants by absorption in amine solvents is a technology aiming at the reduction of CO2 emissions while simultaneously addressing the growth of the global energy demand. However, the energy impact of this technology on the power plant efficiency is high and amine solvent degradation induces a non-negligible environmental impact. The main innovation of this thesis is to combine both aspects within a process model based on experimental data of solvent degradation. This model leads to the identification of optimal operating conditions for the CO2 capture process, from an energetic as well as environmental point of view. [less ▲]

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See detailPrediction of DP steel fracture by FEM simulations using an advanced Gurson model
Fansi Tchonko, Joseph ULg

Doctoral thesis (2013)

This numerical investigation of an advanced Gurson–Tvergaard–Needleman (GTN) model is an extension of the original work of Ben Bettaieb et al. (2011). The model has been implemented as a user-defined ... [more ▼]

This numerical investigation of an advanced Gurson–Tvergaard–Needleman (GTN) model is an extension of the original work of Ben Bettaieb et al. (2011). The model has been implemented as a user-defined material model subroutine (VUMAT) in the Abaqus/explicit FE code. The current damage model extends the previous version by integrating the three damage mechanisms: nucleation, growth and coalescence of voids. Physically based void nucleation and growth laws are considered, including an effect of the kinematic hardening. These new contributions are based and validated on experimental results provided by high-resolution X-ray absorption tomography measurements. Also, the numerical implementation of the kinematic hardening in this damage extension has obliged to readapt the classical triaxiality definition. Besides, a secondary fracture initiation criterion based on the ultimate average inter-cavities distance has been integrated to localize and quantify with good accuracy the strain distribution just before the material fails apart. The current damage model is applied in industrial conditions to predict the damage evolution, the stress state and the fracture initiation in various tensile thin flat sheet geometries and the cross-die drawing tests. [less ▲]

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See detailOptimalisation de la radiosynthèse et production au niveau de la curie d'acides aminés aromatiques marqués au fluor-18
Libert, Lionel ULg

Doctoral thesis (2013)

6-[18F]fluoro-L-dopa (FDOPA) and 2-[18F]fluoro-L-tyrosine (FTYR) are useful radiopharmaceuticals for evaluation by positron emission tomography (PET) of the dopaminergic function and oncological studies ... [more ▼]

6-[18F]fluoro-L-dopa (FDOPA) and 2-[18F]fluoro-L-tyrosine (FTYR) are useful radiopharmaceuticals for evaluation by positron emission tomography (PET) of the dopaminergic function and oncological studies, respectively. In comparison to electrophilic synthesis, the no-carrier-added (nca) nucleophilic preparation of these 2 radiopharmaceuticals, described in 2004 by Lemaire et al, has several advantages such a high batch yield and high specific activity. However, this nca enantioselective synthesis using a chiral phase-transfer catalyst requires some chemicals (i.e. corrosive HBr gas) arduous to handle and store and reactions at low and high temperature (0°C, 200°C) difficult to implement into a commercially available synthesizer. Important chemical improvements, realized during this PhD thesis, having resulted in straightforward automation of FDOPA and FTYR synthesis, in a commercially available FASTLab module (GE healthcare) are presented. The first significant improvement to the synthesis has consisted in the development of a fast and reliable method suitable for the preparation of (substituted) [18F]fluorobenzyl halides from several [18F]fluorobenzaldehydes. Aromatic nucleophilic substitution of trimethylammonium benzaldehyde triflate and nitro precursors were realized with nca [18F]fluoride. After labeling, [18F]fluorobenzaldehydes were trapped on a Solid Phase Extraction (SPE) cartridge and the subsequent conversion (reduction and halogenation) into benzyl halides was directly realized, on-line, on the support. Reduction of the aldehydes and the following halogenation step were performed with an aqueous solution of NaBH4 and aqueous solutions of concentrated acid (HI, HBr, HCl), respectively. These two near-quantitative reactions proceed at room temperature within 2 minutes at high yields. The second improvement of the nca synthesis of FDOPA and FTYR has consisted in the enantioselective formation of a new carbon-carbon bond by phase-transfer catalysis in presence of a chiral phase-transfer catalyst (PTC) at RT rather than at 0°C. Seven chiral phase-transfer catalysts with a potential high enantioselectivity, at room temperature, for the asymmetric alkylation of a N-(diphenylmethylene)glycine tert-butyl ester have been prepared. Two of these catalysts affords high enantiomeric excess in FDOPA and FTYR (e.e. ≥ 95%) at room temperature and even at 75°C (e.e. ≥ 90%). One is readily available from a cinchona alkaloid and the other one from a biphenyl substrate. The third improvement concerned the hydrolysis step (200°C, 20 min). Different starting precursors with more labile protective groups than the methoxy were synthesized and evaluated. Among these compounds, the isopropyl ether protective group seems the more advantageous. By exploiting the advantages of the improvements to the chemistry described in this work and the potential of the nca approach, the synthesis of FDOPA and FTYR was automated in a FASTlab module with GMP single use cassettes. After 100 min of bombardment (167 GBq) and 63 min of synthesis, more than 50 GBq (1,35 Ci) of 6-[18F]fluoro-L-dopa (e.e. ≥ 96,3%) with a specific activity in excess of 0.75 TBq/µmol are routinely produced. For FTYR, slightly higher yield was obtained. With such reliable production, 6-[18F]fluoro-L-dopa and 2-[18F]fluoro-L-tyrosine are now available for clinical investigation. [less ▲]

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See detailStratégies et représentations de l'apprentissage du français langue étrangère chez des lycéens vietnamiens : description et étude de leur rapport avec les compétences linguistiques
Nguyen, Huu Binh ULg

Doctoral thesis (2013)

Strategies that language learners use and their beliefs about language learning are fields that have interested many researchers in recent years. So, what are language learning strategies used by ... [more ▼]

Strategies that language learners use and their beliefs about language learning are fields that have interested many researchers in recent years. So, what are language learning strategies used by Vietnamese learners of French as foreign language? What are their beliefs concerning language learning? Is there any relationship between these elements and proficiency? This is what we propose to study in this doctoral work using quantitative approach with three main research tools: the Strategy Inventory for Language Learning (Oxford, 1990), the Beliefs About Language Learning Inventory (Horwitz, 1988) and a linguistic test. We start this research by meeting the important requirement of the cross-cultural validation of the adopted questionnaires. Then, statistical analysis (descriptive and inferential) will allow us to answer to research questions. The results show that Vietnamese learners have limited and varied strategy use and they have different beliefs about the learning of French as a foreign language. Furthermore, the relationship between strategy use and representations, on the one hand, and between these elements and proficiency, on the other hand, is statistically significant. However, it is fairly complex. To conclude this thesis, we will try to provide possible explanations and point out implications. This discussion will lead to some recommendations aimed at different players involved in the teaching/learning of French in Vietnam. [less ▲]

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See detailProtein Identification and Quantification in Mixtures of highly-modified Proteins
Dobson, Rowan ULg

Doctoral thesis (2013)

The identification and quantification of proteins in highly-modified mixtures using proteomics has been performed. Two research projects have been undertaken which fulfil this aim. The first comprised the ... [more ▼]

The identification and quantification of proteins in highly-modified mixtures using proteomics has been performed. Two research projects have been undertaken which fulfil this aim. The first comprised the development of quantitative methods to detect trace amounts of hazelnut and soy in complex mixtures. A method for the detection and absolute quantification of Cor a 9, a major hazelnut (Corylus avellana) allergen was developed based on mass spectrometry. One hundred and ten hazelnut proteins were detected, five of which were allergens. The peptide chosen for quantification was from Cor a 9 (11S globulin-like protein). Two specific fragmentation reactions were chosen in multiplexed Selected Reaction Monitoring (SRM). Forty three hazelnut food processing imitation samples, varying a range of factors, such as the temperature and incubation time were analysed. A calibration curve was made for cookies. The developed method was for home-made cookies, shop-bought cookies and chocolate. The quantities of Cor a 9 in each sample were determined from the quantification of the target peptide using isotopic dilution with a heavy isotopically labelled peptide. A second peptide with two transitions was also proven to be a possible alternative as a detection method for hazelnut. The presence of soybean allergens in processed food can be detected using the mass spectrometric identification of a soybean peptide which is resistant to the heating and chemical reactions associated with food processing. The proteomic analysis of soybeans allowed the identification of 11 allergens. A method using a peptide (VFDGELQEGR) from glycinin G1 (Gly m 6.0101) was developed for the detection and semi-quantification of the allergen in food samples. Two specific fragmentation pathways were chosen in selected reaction monitoring for unambiguous identification of glycinin G1 and were: 575.3 903.4 Da and 575.3 788.4 Da. Sixteen imitation samples of processed food spiked with soybean were analyzed, where factors such as temperature and incubation time were varied, and the chosen transitions were detected. The developed method was specific for home-made cookies and a shop-bought biscuit. Semi-quantification from both cooked and uncooked cookies was demonstrated. The second comprised the identification and quantification of conotoxins in the venom of Conus textile by the use of isotope coded affinity tagging (ICAT) and label-free quantification. The extreme variety and complexity of the conotoxins has been insufficiently documented and this research demonstrates the varied nature of conotoxins found in different parts of the venom duct and their patterns of expression. Fifteen conotoxins, several with different post-translational modifications (PTMs), were identified and quantified. Distinctive patterns emerged, with the largest group of conotoxins increasing, then peaking in the central6 proximal part, before decreasing; whilst the second largest group peaked in the distal region, generally displaying nothing in the first parts. A new conotoxin, PCCSKLHDNSCCGL*, was sequenced. [less ▲]

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See detailTesting candidate effectors contributing to resistance to pneumoviruses
Dermine, Martin ULg

Doctoral thesis (2013)

Pneumoviruses are members of the Paramyxoviridae family, negative sense single stranded RNA viruses. The 3 major members of the pneumovirus genus are human respiratory syncytial virus (huRSV), bovine ... [more ▼]

Pneumoviruses are members of the Paramyxoviridae family, negative sense single stranded RNA viruses. The 3 major members of the pneumovirus genus are human respiratory syncytial virus (huRSV), bovine respiratory syncytial virus (boRSV) and their murine counterpart, pneumonia virus of mice (PVM). In humans, huRSV mainly infects young children and can lead, in the worst cases, to infantile bronchiolitis, which is the first cause of children hospitalization and concerns 2.3% of children under the age of one. Many laboratories are studying this disease in order to better understand the role played by the immune system on its pathogenesis and to create an efficient and safe vaccine that does not exist for now. In bovine, boRSV generates stable epidemics in calves under 6 months of age and causes important economic losses in terms of veterinary costs and loss of productivity. These viruses infect the respiratory tract and generate a disease that importantly depends on the genetic background of the host. The quality of the immune response plays a considerable role in the expression as well as in the outcome of the disease, especially during its first instants. The study of pneumoviruses diseases has been widely developed using murine models of infection by heterologous huRSV. It is now assumed that this model, although providing interesting information, only weakly reproduces human disease on the contrary to infection of mice with their homologous pneumovirus: PVM. This model has been broadly developed in our laboratory, by highlighting the similarities between murine, human and bovine diseases, i.e. an important morbidity, intra-pulmonary granulocytic influx, viral amplification and evolution toward acute respiratory distress syndrome. The present work consisted in studying potential effectors of the resistance of mice against PVM infection: two proteic and two cellular effectors. A first working hypothesis was to evaluate the role of Carcinoembryonic antigen-related cell adhesion molecule 1 (Ceacam1) as a potential receptor for PVM. This membrane protein present at the surface of respiratory epithelial cells is known to be mutated in SJL/J mice, the most resistant strain to PVM infection. We have thus infected highly PVM-susceptible 129/Sv mice and compared their susceptibility to Ceacam1a knock-out 129/Sv mice. Our results have permitted to discard Ceacam1a as a receptor to PVM. The second tested protein is bovine Mx1 (boMx1) GTPase. We wished to assess if its expression could lead, as it is the case for numerous negative sense single stranded RNA viruses, to a resistance to PVM. Transgenic mice producing boMx1, engineerd in our laboratory in an FVB/J background, have been infected and their susceptibility has been compared to wild-type FVB/J mice. We could evidently demonstrated that boMx1 induces resistance to PVM. We have thus, for the first time, demonstrated that an Mx protein induces resistance to a pneumovirus. We have then compared 2 inbred mice strains presenting opposite phenotypes concerning their susceptibility to PVM: SJL/J (resistant) and 129/Sv (susceptible). Our goal was to evaluate if the difference in resistance is present during the first moments of infection. Therefore, we have focussed on both cell types that first interact with the virus: respiratory epithelial cells and alveolar macrophages. Virus tropism and respiratory epithelial permissivity to viral amplification were compared between both strains. In the same way, alveolar macrophages’ phenotypes (phagocytosis, susceptibility to viral infection, cytokine production) were compared between SJL/J and 129/Sv. Our results could not demonstrate any difference concerning respiratory epithelium. On the other hand, a pivotal role could be attributed to alveolar macrophages in the first instants of the infection. SJL/J alveolar macrophages presented greater phagocytic capacity, increased resistance to virus replication and earlier and higher cytokine production. Our results concerning the role of alveolar macrophages as a key effector of the immune response during the infection of mice by PVM raises new interrogations. Differences observed between SJL/J and 129/Sv alveolar macrophages regarding their resistance to viral infection, their greater phagocytic capacity and their cytokine secretion will have to be further investigated in order to understand the relative importance of these three characteristics in the resistance process of SJL/J to PVM infection. A particular attention will have to be given to the candidate cytokines in order to determine if one of them plays a particular role in the disease outcome. Moreover, the anti-PVM property of boMx1 raises the question of why boMx1 possesses an anti-PVM property but no anti-boRSV effect. Comparison of the interaction of boMx1 with PVM or boRSV could help understanding this anti-PVM effect. [less ▲]

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See detailLa réforme du Conseil de sécurité et les relations internationales. Processus, Acteurs et Enjeux
Mputu-Jngole, Jean-Claude ULg

Doctoral thesis (2013)

The UN has committed in recent years in a long process of reform to adapt to the changing world. If several reforms have emerged, Member States are unable to agree on the content of the reform of the ... [more ▼]

The UN has committed in recent years in a long process of reform to adapt to the changing world. If several reforms have emerged, Member States are unable to agree on the content of the reform of the Security Council. The present thesis analyzes this process through the positions of the players to highlight the issues of the reform in international relations from the perspective of power. [less ▲]

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See detailContribution to the Inverse Dynamics of Flexible Manipulators
Guimaraes Bastos Junior, Guaraci ULg

Doctoral thesis (2013)

This thesis studies innovative, stable but non-causal inverse dynamics algorithms for flexible manipulators. Robust direct optimal control methods are proposed. The nonlinear finite element method is used ... [more ▼]

This thesis studies innovative, stable but non-causal inverse dynamics algorithms for flexible manipulators. Robust direct optimal control methods are proposed. The nonlinear finite element method is used to derive the mechanical model of the multibody system and the time discretization is performed using the generalized-alpha method. The sparse gradients of the optimization constraints are computed using a semi-analytical method. The inverse dynamics of both serial and parallel kinematic manipulators with flexible links and joints is successfully studied using the proposed method. Finally, the possible extension of the method for the integrated control/structure optimization of mechatronic systems is investigated. [less ▲]

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See detailCost monitoring in dairy farms to promote the value chain of fresh milk in North Vietnam
Bui, Thi Nga ULg

Doctoral thesis (2013)

In Vietnam, the consumption of dairy products has increased dramatically in recent years due to rising incomes. To meet this growing demand, and reduce imports, the Vietnamese Government has encouraged ... [more ▼]

In Vietnam, the consumption of dairy products has increased dramatically in recent years due to rising incomes. To meet this growing demand, and reduce imports, the Vietnamese Government has encouraged milk production. In this context, our research is primarily interested in the distribution of value added among the actors within the fresh milk chain observed in the province of Son La. Our study demonstrates that value added within the fresh milk chain was unequally distributed among actors in the chain in the bias orientation to the non-farmers (nonproducer). The key feature in the chain was the dairy farmers, but they were also the most vulnerable actors of the chain. Given the balance of power among the actors, the most appropriate method to promote the added value for dairy producers is to help a better control on their production costs by improving the management at the dairy farm. In the second part of the work, we are inspired from foreign experience in this field to define an accounting system for technical-economic monitoring of dairy cattle adapted for the situation of Vietnamese farmers. This system has been tested in Moc Chau in an experimental dairy farm to provide data regarding the efficiency and profitability of operations. Dairy farmers were interested in the proposed monitoring system because it allows them to know the level of performance and to compare it to the others. They were interested in revenue generated from costs control. The major constraints in the application of this monitoring in selected farms were the lack of capacity and knowledge from producers. In conclusion, our study provides an appropriate model for the establishment of a management system of milk production. The most suitable model is to set up an independent agency. The cost of this monitoring was estimated, and scenarios for sustainability have been proposed. Contributing to lower costs through a better understanding of technical and economic performance of farmers, the service management operations will improve the competitiveness of locally produced milk with imported products. [less ▲]

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See detailEstimation des débits d'étiage pour des sites non jaugés. Application en Région wallonne.
Gailliez, Sébastien ULg

Doctoral thesis (2013)

La mise en oeuvre de la Directive sur l’Eau, l’attribution des permis d’environnement et le contexte de l’hydro-électricité, demandent régulièrement la connaissance des débits caractérisant l’étiage d’un ... [more ▼]

La mise en oeuvre de la Directive sur l’Eau, l’attribution des permis d’environnement et le contexte de l’hydro-électricité, demandent régulièrement la connaissance des débits caractérisant l’étiage d’un cours d’eau. L’objectif de cette thèse est de développer un modèle permettant de définir ce débit en n’importe quel point d’un linéaire de cours d’eau non jaugé, et ce, pour n’importe quelle période de retour, ainsi que l’incertitude sur la valeur calculée. Les variables hydrologiques choisies sont le percentile95 (débit atteint ou dépassé 95 pourcents de l’année, Q95) et le MAM7 (plus faible valeur de la moyenne mobile des débits atteints pendant 7 jours consécutifs de l’année). Après avoir sélectionné les stations de mesures situées sur le territoire wallon sur base d’un certain nombre de critères (taille de l’historique, extrapolation de la courbe de tarage, présence d’algues durant la période estivale, homogénéité des données, …), une analyse fréquentielle est réalisée sur les débits caractéristiques d’étiage (Q95 et MAM7). L’extraction de paramètres physiques et climatiques des bassins versants (pente, occupation du sol, superficie du bassin versant, pédologie, hydrogéologie, précipitations, …), permet de régionaliser la zone étudiée par classification numérique. Les bassins versants des 59 stations de mesures retenues sont regroupés en quatre zones homogènes qui sont ensuite différenciées à l’aide d’une analyse en composantes principales. Suite à une analyse de la variance et considérant le nombre peu élevé de stations de mesures retenues dans certains groupes homogènes, un modèle de régression linéaire est défini pour l’ensemble de la Wallonie à partir de 24 paramètres physiques et de la méthode ‘Stepwise’, pour les périodes de retour de 2, 5, 10, 20 et 50 ans. Les modèles obtenus permettent la détermination d’une valeur de débit d’étiage en n’importe quel point d’un petit bassin versant non jaugé et l’estimation de l’incertitude sur base des intervalles de confiance. Les deux paramètres retenus dans les modèles de régression sont le coefficient de tarissement et la percolation. En imposant la forme du modèle pour chaque période de retour et en analysant la relation entre les coefficients des paramètres explicatifs et les périodes de retour, on met en évidence la possibilité d’interpoler entre les périodes de retour. Ainsi, un modèle global permettant le calcul d’un débit caractérisant l’étiage pour n’importe quelle période de retour (entre 2 et 50 ans) est déduit. Les modèles de régression sont ensuite validés et une mise en oeuvre simple de ces derniers est proposée. L’identification des régions homogènes devra conduire à la construction de modèles dédiés à chaque région selon la même méthodologie, lorsque le nombre de stations disposant d’une chronique suffisante et répondant aux critères de qualité, sera suffisant dans chacune d’elles. [less ▲]

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See detailCaractères génétiques et zootechniques du porc Piétrain stress négatif en croisement avec les truies exotiques et locales au Nord du Vietnam
Do Duc, Luc ULg

Doctoral thesis (2013)

This study is concerned negative stress Piétrain pigs (Piétrain RéHal) and its use under households and farming intensive conditions in northern Vietnam to improve the lean meat percentage of fattening ... [more ▼]

This study is concerned negative stress Piétrain pigs (Piétrain RéHal) and its use under households and farming intensive conditions in northern Vietnam to improve the lean meat percentage of fattening pigs. At the beginning, the imported purebred nucleus of Piétrain from Belgium was studied. Later, Piétrain pigs were used as the terminal boars under household and farming intensive conditions. Finally, hybrid terminal boars between Piétrain and Duroc were studied. Performance of purebred nucleus of stress negative Piétrain In 2007, a total of 19 pigs of purebred Piétrain RéHal (6 males and 13 females) aged approximately 2 months was imported into North Vietnam from the Experimental farm of the Faculty of Veterinary Medicine of the University of Liège. At the first time, the production performance of the first imported pigs was studied since their arrival to 8.5 months of age. The average body weights of this nucleus at the age of 2, 4, 5.5 and 8.5 months were 19.05, 51.05, 85.82 and 119.47 kg respectively. The average daily gain and the lean meat percentage of these animals are 528.56 g/d and 64.08% respectively. The males (546.48 g/d) grew faster than females (520.29 g/d); however this difference was not significant (P> 0.05). The same trend was present in both sexes for the percentage of lean meat (65.26 vs. 63.44%). The feed conversion ratio was 2.69 kg. Stress negative Piétrain pig could develop well on farm conditions in Hai Phong province, Vietnam. In the second time, the initial nucleus was multiplied. Reproduction and production performances and the semen quality of purebred nucleus were studied. No significant differences were observed between the halothane genotypes (CC and CT) of sows for reproduction traits (P>0.0578). At the age of 7.5 months, body weight, backfat thickness and longissimus depth of CC pigs were higher than those of CT (P <0.05). Compared to sows born in Belgium, sows born in Vietnam had a longer gestation (117.42 vs. 116.38 days), more piglets born alive (8.73 vs. 6.99) and heavier average litter weight (12.37 vs. 10.04) at birth (P <0.01). Gilts had more lean meat (P<0.01) than intact boars (65.00 vs. 64.03%). The total number of spermatozoa per ejaculat of boars born in Vietnam was higher (P<0.001) than that those of boars born in Belgium (114.54x109 vs. 80.47x109). This value of CC boars was higher than those of CT (P<0.05). Compared with observations made in temperate countries, the reproduction and production performances, sperm concentration and total number of spermatozoa of Piétrain pigs were reduced, whereas lean meat percentage was not affected. The results support the interest of the use of this new Piétrain line in tropical countries with ecological and climatic conditions similar to Vietnam. Utilization of stress negative Piétrain pigs under household conditions In the next step, Piétrain pigs were used as terminal boars under household conditions for the production of fattening pigs. The hybrid sows between Large White and Mong Cai (F1) mated to Duroc (DU) or Piétrain (PI) boars to the production of the two types of fattening pigs as following: 1) DuxF1 and 2) PIxF1. Reproduction and production performances, carcass characteristics as well as meat quality were evaluated. The results show that household affected production performances, carcass, and meat quality traits (P<0.05) as well as reproduction (weights at birth and weaning, P<0.01). Inversely, boar breeds did not influence (P>0.06) on reproduction traits (except individual weight of born alive pigs and weaned pigs, P<0.01), production traits, meat chemical composition and meat quality (except pH at 4 days post mortem, P<0.05) while lean meat percentage of Piétrain-sired pigs was higher than those of Duroc-sired pigs (P<0.05). The utilization of Piétrain boars does not affect reproduction performances, growth rate and meat quality while improving lean meat percentage in comparison to Duroc boars. This suggests that the use of stress-negative Piétrain boars as terminal sires would improve lean meat percentage under household conditions in North Vietnam. Utilization of stress negative Piétrain pigs in the farming intensive conditions In the farming intensive conditions, Piétrain pigs are also used as the terminal boars to the production of 3-ways fattening pigs and as the genetic resource to the production of hybrid terminal boars with Duroc. Production performance, carcass traits and meat quality of 3-ways fattening pigs [Px(LxY)] between Piétrain boars (P) and Landrace x Large White sows (LxY) had been studied. Barrows grew faster (P=0.0171) than gilts (670 vs. 631 g/d) but had less (P=0.0015) lean meat percentage (58.6 vs. 60.4%). However, sex did not affect carcass and meat quality traits (P>0.0656). The pH values of longissimus dorsi muscle of barrows and gilts at 45 minutes (6.38 and 6.43) and 24 hours (5.46 and 5.49) post mortem were similar (P>0.312). This pH value corresponds to a normal meat. Crossbred fattening pigs from stress negative Piétrain sires mated to Landrace x Large White sows under intensive production system presented normal growth rate, high lean meat percentage and satisfactory meat quality. This suggests that the use of stress negative Piétrain boar under farming intensive conditions in northern Vietnam could improve lean meat percentage while not affecting growth rate and meat quality. The Piétrain pig is not only used as a terminal sire, but also as a genetic resource to the production of hybrid terminal boars according different component of Piétrain and Duroc. Five genetic groups PiDu25, PiDu50, PiDu75, PiCC and PiCT were hybrid boars with 25, 50 and 75% of Piétrain origin and purebred Piétrain with halothane genotypes CC and CT respectively. The results showed that genetic group has a significant effect on growth performance and semen quality (P<0.05). The hybrid boars had better growth rate (577.48 to 635.07 g/d) than purebred stress-negative Piétrain (516.00 to 552.93 g/d), but lean meat percentage was lower (59.02 to 63.57 for hybrids vs. 63.87 to 65.11 % for purebred Piétrain). The increased proportion of Piétrain in hybrids boars did not affect the growth rate (P> 0.05), while it has a significant effect on the lean meat percentage (P <0.05). The total number of spermatozoa of PiDu75 (53.78x109) and PiCT (49.83x109 spermatozoa) is lower than those of other genetic groups (92.27x109 to 93.99 x109 spermatozoa). The total number of spermatozoa was affected by the seasons of the year (P<0.01). This value was lower during the hot period (summer and autumn) and higher during the cold period (winter and spring). The Piétrain x Duroc hybrid boars, especially PiDu75 seem to be promising as terminal boars to improve growth rate of fattening pigs while still maintaining high lean meat percentage. Cette étude aborde les porcs de Piétrain stress négatif (Piétrain RéHal) et son utilisation dans les conditions d’élevage familial et intensif au nord du Vietnam pour améliorer le pourcentage de viande maigre des porcs d’engraissement. Le noyau de Piétrain pur importé de la Belgique a d’abord été étudié. Ensuite, les porcs de Piétrain ont été utilisés comme verrats terminaux dans les conditions d’élevage familial et intensif. Enfin, des verrats hybrides terminaux Piétrain x Duroc ont été étudiés. Performances du noyau pur de porc Piétrain stress négatif En 2007, Un total de 19 porcs de Piétrain pur RéHal (6 mâles et 13 femelles) âgés d’environ 2 mois, a été importé au nord du Vietnam au départ de la ferme expérimentale de la Faculté de Médecine Vétérinaire de l’Université de Liège. Dans un premier temps, les performances de production de ces premiers porcs ont été étudiées depuis leur arrivée jusqu’à 8,5 mois d’âge. Le poids vif moyen de ce noyau à l’âge de 2 ; 4; 5,5 et 8,5 mois était respectivement de 19,05 ; 51,05 ; 85,82 et 119,47 kg. Le gain quotidien moyen et le pourcentage de viande maigre de ces animaux sont respectivement 528,56 g/j et 64,08 %. Le gain quotidien moyen était plus important chez les mâles (546,48g) que chez les femelles (520,29 g) cependant cette différence n’est pas significative (P>0,05). La même tendance existait entre les deux sexes pour le pourcentage de la viande maigre (65,26 vs 63,44 %). L’indice de conversion alimentaire était de 2,69 kg. Le porc Piétrain stress négatif pourrait bien se développer dans les conditions de la ferme à Hai Phong, au Vietnam. Dans un deuxième temps, le noyau de départ fut multiplié. Les performances de reproduction et de production et qualité du sperme des animaux issus de ce noyau pur ont été étudiées. Aucune différence n’a été observée entre les génotypes CC et CT chez les truies pour ce qui concerne les caractères de reproduction (P> 0,0578). À l'âge de 7,5 mois, le poids vif, l’épaisseur du lard dorsal et l’épaisseur du carré de porcs CC étaient plus élevées que ceux de CT (P<0,05). Par rapport aux truies nées en Belgique, les truies nées au Vietnam avaient une plus longue durée de gestation (117,42 vs 116,38 jours), plus de porcelets nés vivants (8,73 vs 6,99) et le poids moyen d’une portée à la naissance plus lourd (12,37 vs 10,04, P<0,01). La teneur en viande maigre chez les femelles (65,00 %) était supérieur (P<0,01) à celle chez les mâles intacts (64,03 %). Le nombre de spermatozoïdes par éjaculat de verrats nés au Vietnam était supérieur (P<0,001) que celui de verrats nés en Belgique (114,54x109 vs 80,47x109). Cette valeur de verrats CC était supérieure à celle de CT (P<0,05). En comparaison avec les observations faites dans les pays tempérés, les performances de reproduction et de production, la concentration du sperme et le nombre total de spermatozoïdes de porcs Piétrain ont été diminués, néanmoins le pourcentage de viande maigre n'a pas été affecté. L’implication possible de ce résultat pour la production porcine dans les pays tropicaux ayant des conditions écologiques et climatiques comme celles du Vietnam. Utilisation de porc Piétrain stress négatif dans les conditions d’élevage familial Dans l’étape suivant, les porcs Piétrain sont utilisés comme les verrats terminaux dans les conditions d’élevage familial pour produire les porcs d’engraissement. Les truies hybrides entre Large White et Mong Cai (F1) croisent soit avec les verrats Duroc (DU), soit avec Piétrain (PI) pour produire 2 types des animaux d’engraissement à savoir : 1) DuxF1 et 2) PIxF1. Les performances de reproduction, production, caractères de carcasse et la qualité de la viande ont été évalués. Les familles-éleveurs ont affecté les caractères production, de carcasse, et de qualité de la viande (P <0,05) ainsi sur reproduction (les poids de porcelets à la naissance et au sevrage, P <0,01). A l'inverse, les types de verrats n’ont pas influencé (P>0,06) sur les caractères de reproduction (à l'exception du poids individuel des porcs nés vivants et des porcs sevrés, P <0,01), de production, la qualité de la viande (sauf le pH obtenu à 4 jours post mortem, P <0,05). Cependant la teneur en viande maigre des porcs PIxF1 était plus élevé que cela de DUxF1 (P<0,05). Ces résultats ont montré que le pourcentage de viande maigre des porcs d’engraissement dans les conditions d’élevage familial au nord du Vietnam peut être amélioré en utilisant le verrat Piétrain dans le croisement terminal à la place du verrat Duroc sans affecter le gain quotidien moyen. Utilisation de porc Piétrain stress négatif dans les conditions d’élevage intensif Dans les conditions d’élevage intensif, les porcs de Piétrain sont également utilisés comme les verrats terminaux pour produire les porcs d’engraissement à 3 voies ainsi que comme la source génétique pour produire les verrats terminaux hybrides avec Duroc. Les performances de productions, carcasse et qualité de la viande des porcs d’engraissement à trois voies [Px(LxY)] entre les verrats Piétrain (P) et les truies Landrace x Large White (LxY) ont été étudiées. Les mâles castrés présentaient une vitesse de croissance plus rapide (P=0,0171) que les femelles (670 vs 631 g/j), cependant le pourcentage de viande maigre avait présenté une tendance inversée (58,6 vs 60,4%, P=0,0015). Le sexe n’a pas affecté les caractères de la carcasse et la qualité de viande (P>0.0656). Le pH du carré chez les mâles castrat et femelles à 45 minutes (6,38 et 6,43) et à 24 heures (5,46 and 5,49) post mortem était similaire (P>0,312). Cette valeur de pH correspond à une viande normale. Les porcs d’engraissement issus du croisement entre le père Piétrain et la mère Landrace x Large White dans les conditions d’élevage intensif ont présenté une vitesse de croissance normale, une teneur en viande maigre élevé et une viande de qualité satisfaisante. Ceci suggère que l'utilisation de stress négatif sanglier Piétrain dans les conditions d'élevage intensif au nord du Vietnam pourrait améliorer la teneur en viande maigre en n'affectant pas le gain quotidien moyen et la qualité de la viande. Le porc Piétrain n’est pas seulement utilisé comme un verrat terminal, mais encore comme une source génétique pour produire des verrats terminaux hybrides en fonction de taux différent de Piétrain et Duroc. Cinq groupes génétiques PiDu25, PiDu50 et PiDu75, PiCC et PiCT étaient les verrats avec respectivement 25, 50 et 75% d’origine Piétrain et Piétrain pur avec les génotypes CC et CT. Les résultats ont montré que le groupe génétique avait un effet sur les performances de production et qualité du sperme (P<0,05). Les verrats hybrides présentent généralement une vitesse de croissance (577,48 à 635,07 g/j) supérieure que ceux de Piétrain pur (516,00 à 552,93 g/j), mais avec une teneur en viande maigre est inférieure (59,02 à 63,57 vs 63,87 à 65,11 %). L’augmentation de proportion de Piétrain chez les verrats hybrides n’a pas affecté sur la vitesse de croissance (P>0,05) alors qu’elle exerce un effet significatif sur le pourcentage de viande maigre (P<0,05). Le nombre total de spermatozoïdes des verrats PiDu75 (53,78x109) et PiCT (49,83x109) est inférieur à celui des autres groupes (92,27x109 à 93,99x109). Le nombre total de spermatozoïdes a été affecté par les saisons de l’année (P<0,01). Il était inférieur pendant la période chaude (été et automne) et supérieur en période froide (hiver et le printemps). Ces résultats montrent que les hybrides entre Piétrain et Duroc, en particulier PiDu75 semblent être prometteurs comme les verrats terminaux pour améliorer la vitesse de croissance chez les porcs d'engraissement tout en gardant le pourcentage élevé de viande maigre. [less ▲]

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See detailORF9p: a new player in the Varicella-Zoster Virus egress
Riva, Laura ULg

Doctoral thesis (2013)

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See detailExoplanet imaging with mid-infrared vector vortex coronagraphs: design, manufacture, validation and first light of the annular groove phase mask
Delacroix, Christian ULg

Doctoral thesis (2013)

During the past twenty years, detections of extrasolar planets have flourished and grown expo- nentially, reaching almost 900 confirmed exoplanets so far. This number is doubling every two or three years ... [more ▼]

During the past twenty years, detections of extrasolar planets have flourished and grown expo- nentially, reaching almost 900 confirmed exoplanets so far. This number is doubling every two or three years. The most recent discoveries made by the Kepler mission have revealed two Earth- size exoplanets orbiting the same star, and fulfilling all the required conditions to be habitable. Imaging techniques have also come a long way. Since the first direct detection in 2004, some stunning exoplanet pictures have been captured at the telescope under special circumstances of moderate contrast and/or angular separation, thanks to the advent and continuous improvement of adaptive optics systems and data reduction methods. In this broad context, the need for high contrast imaging techniques with very small inner working angles has never been so strong. Coro- nagraphy has a key role to play in order to provide the means necessary for imaging Earth-size planets, and try to answer the recurring question of the possible presence of life outside the solar system. The present thesis is dedicated to the development of the annular groove phase mask (AGPM), a specific type of broadband vector vortex coronagraph based on subwavelength gratings. Consid- ered for several years as one of the best solutions for building high-performance mid-infrared coron- agraphs with small inner working angles, the AGPM has never been validated up to now. Although various fabrication processes are available, depending on the substrates and micro-lithography techniques considered, they often face extremely challenging constraints. In the present work, we explored the feasibility of achromatic micro-components made out of subwavelength gratings, for which two technological solutions are followed: quartz and diamond. As we focussed on the diamond option, its unique material properties making it a prime candidate for mid-infrared ap- plications, we managed to develop mid-infrared broadband half-wave plates, ideally optimized to enable the manufacturing of charge-2 vortices. Following this success, we continued our devel- opments leading to the fabrication of several AGPMs for two astronomic windows, the L and N bands, and we successfully validated several L-band AGPMs on a coronagraphic test bench at the Observatoire de Paris. In the last chapter, we expose the recent installation of our components on three world-class infrared cameras, VISIR and NACO at the Very Large Telescope in Chile, and LMIRCam at the Large Binocular Telescope in Arizona. We conclude with the very first on-sky results of both N-band and L-band AGPMs, and the discovery and successful imaging of a faint stellar companion at two beamwidths from an F-type star. [less ▲]

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See detailImpacts and mechanisms of action of endocrine disrupting chemicals on the hermaphroditic freshwater gastropod Lymnaea stagnalis (Linnaeus, 1758)
Giusti, Arnaud ULg

Doctoral thesis (2013)

Adverse impacts exerted by molecules called endocrine disruptors on reproduction have been extensively described in vertebrates. However, endocrine-disrupting chemicals might alter reproduction of ... [more ▼]

Adverse impacts exerted by molecules called endocrine disruptors on reproduction have been extensively described in vertebrates. However, endocrine-disrupting chemicals might alter reproduction of invertebrate species, at lower concentrations or through different modes of action, with consequences on population growth and stability. Among invertebrates, molluscs have been shown to be very sensitive to endocrine disruptors and were therefore proposed as model species for the development of OECD guideline for the testing and the assessment of reprotoxic effect of chemicals, including EDCs. The hermaphrodite gastropod species Lymnaea stagnalis is a candidate species for the development of such guidelines. In this context, the aim of this thesis is to provide a better understanding of the impacts and the mechanisms of action of endocrine disrupting chemicals on the reproduction of L. stagnalis. The chemicals tested in the present work were chosen based on their interactions with the endocrine system of vertebrates. Testosterone is the natural ligand of the androgen receptor in vertebrates. Three different molecules were selected for their antagonism of the androgen receptor in vertebrates: the synthetic steroid cyproterone acetate, the dicarbamide fungicide vinclozolin and the organophosphate insecticide fenitrothion. Chlordecone is an organochlorinated pesticide, which binds oestrogen receptors in vertebrates. Finally, two organotin compounds, triphenyltin and tributyltin, are able to induce the development of imposex, imposition of male sex organs in females, in gonochoric gastropod molluscs. Results of the present work are divided into two main sections. Firstly, we investigated the impacts of the selected chemicals on the reproduction of L. stagnalis. Our results displayed that TBT, TPT, and chlordecone are able to induce adverse impacts on the reproduction of L. stagnalis through a reduction of the cumulative number of eggs and clutches produced per individual. The assessment of the quality of eggs produced showed that exposure to the chemicals, except TPT, increases the frequency of abnormal eggs laid. The impacts on egg quality were observed at lower concentrations than those affecting the classical reproductive endpoints assessed in reprotoxicity tests in this species. Our results highlight that the implementation of egg quality as an endpoint should increase the sensitivity of the reprotoxicity test with L. stagnalis. The second section of results aims at providing new insights on the mechanisms of action of putative endocrine disruptors in L. stagnalis. Results from chapter 3 and 4 allowed us to select chemical treatments (testosterone, tributyltin, cyproterone acetate, and chlordecone) that induced adverse effects, by interacting with the endocrine system, on the reproduction of L. stagnalis. In Chapter 5, we analysed endogenous concentrations of testosterone, in its free and esterified forms, in the reproductive organs of L. stagnalis. Exposure to waterborne testosterone has confirmed that molluscs can take up this steroid from environmental media and that a homeostatic regulation of endogenous concentrations occurs through the esterification of steroids to fatty acid esters. Moreover, our results support that testosterone is endogenously synthesised in L. stagnalis, as it has been suggested in other mollusc species. However, the impacts on the reproduction and the modifications of endogenous concentrations of testosterone reported in this thesis could not be associated. In chapter 6, proteomic experiments were used to identify proteins differently expressed in reproductive organs of L. stagnalis exposed to testosterone, tributyltin, cyproterone acetate, and chlordecone. Modifications in the expression of three proteins involved in L. stagnalis reproduction (i.e., ovipostatin, yolk ferritin and PIWI) could be associated with the alterations of reproductive endpoints reported in chapters 3 and 4, therefore suggesting possible endocrine disruption mechanisms. Altogether, the results obtained in the present work provide evidences of interactions between chemicals and the endocrine system of this hermaphrodite species. Moreover, the additional sensitive reproductive endpoints described in this thesis (i.e., egg quality) as well as the identification of particular proteins (i.e., ovipostatin, yolk ferritin and PIWI) and their differential expression patterns following chemical exposure, provide reliable tools to screen potency of toxicants to be endocrine disruptors in a partial life cycle test on the freshwater gastropod Lymnaea stagnalis. [less ▲]

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See detailMinéralogie et propriétés physico-chimiques des smectites de Bana et Sabga (Cameroun). Utilisation dans la décoloration d'une huile végétale alimentaire
Mache, Jacques Richard ULg

Doctoral thesis (2013)

In this study, clay samples were collected in the localities of Bana and Sabga, in the regions of the west and north-west Cameroon, respectively. The purpose of this study was to determine their ... [more ▼]

In this study, clay samples were collected in the localities of Bana and Sabga, in the regions of the west and north-west Cameroon, respectively. The purpose of this study was to determine their mineralogical composition, their physico-chemical properties and to assess their potential use in the bleaching process of palm oil, which is the main edible vegetable oil produced and refined in Cameroon. <br /> The results obtained from the analyses (XRD, FTIR, DTA / TGA and SEM) revealed that montmorillonite is the main clay mineral in these materials. It is associated with kaolinite and mica. Non-clay minerals such as quartz, anatase, cristobalite, K-feldspar and heulandite are also identified in variable quantities. Chemical analyses of the major elements show that the clays from Bana and Sabga consist mainly of the follow oxides such as SiO2, Al2O3 and Fe2O3. Bana clays have a cation exchange capacity (CEC) between 50 and 60 meq/100 g and a specific surface area between 50 and 60 m2/ g. Sabga clays have a lower capacity cation exchange (38- 46 meq/100 g) and a wider range of specific surface area (33-90 m2 / g). The characterization of the natural clays allowed to select of one sample by locality for sulfuric acid treatment. <br />The acid treatment of these materials led to structural, morphological and textural changes. Analysis by X-ray diffraction showed a progressive decrease in the intensity of the (001) reflection of montmorillonite and a shift of its basal d001-value. Treatment with more acid concentration causes an increase in the surface area of the obtained products and a decrease in cation exchange capacity. <br />The assessment of the bleaching power of natural and acid-activated Bana clay in palm oil decolorization shows that the activated clay has a high bleaching capacity (~ 87%) compared to the natural clay (~ 55%). palm oil Bleaching by these clay materials does not deteriorate the bleached oil. These materials can thus be used as bleaching earths in the refining oil process. [less ▲]

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See detailModeling of Electromagnetic Systems by Coupling of Subproblems – Application to Thin Shell Finite Element Magnetic Models
Dang, Quoc Vuong ULg

Doctoral thesis (2013)

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

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

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See detailLe Munkoyo : une source d'amylases végétales pour une boisson fermentée traditionnelle
Foma Kibwega, Roland ULg

Doctoral thesis (2013)

In Africa, several sources of amylases are not well documented. Munkoyo roots are used as the source of amylases during the traditional preparation of a fermented beverage called munkoyo. These roots are ... [more ▼]

In Africa, several sources of amylases are not well documented. Munkoyo roots are used as the source of amylases during the traditional preparation of a fermented beverage called munkoyo. These roots are unique as the synthesis and accumulation of amylases activities do not require germination. Despite this advantage, munkoyo roots are not well known as sources of amylases and they have not yet been introduced into industrial processes. Thus, the aim of this PhD project was to (1) promote munkoyo roots as sources of α- and β-amylases and to (2) propose pathways of optimization and industrialization of manufacturing munkoyo beverage. In the first part, purification, characterization and identification of α- and β-amylases from munkoyo roots was achieved. Amylases from roots of Eminia holubii, Eminia harmsiana, Rhynchosia insignis insignis and Rhynchosia insignis affinis were retained in our study. Compared to malted cereals, α- and β-amylases from munkoyo roots are more thermostable and their activities are optimal at high temperatures. However, these properties are closer to those of germinated cotyledons belonging to some Fabaceae family plants. Using LC-ESI MSMS analysis, this study showed significant matching of α- and β-amylases from munkoyo roots to germinated leguminous seeds. In the second part, the traditional production of munkoyo beverage was studied. The evolution of physicochemical parameters and ferments involved in spontaneous fermentation was investigated. Acidification is promoted by thermophilic and heterofermentative lactic acid bacteria. Alcohol production in munkoyo is due mainly to Saccharomyces cerevisiae. The study shows that knowledge of amylase properties and the use of an appropriate microbial starter will optimize the manufacturing process and the quality of munkoyo beverage. [less ▲]

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See detailThe role of glycine receptors during cerebral cortical development
Avila Macaya, Ariel Salvatore ULg

Doctoral thesis (2013)

This study focuses on glycine receptors (GlyR) and explores their possible physiological functions on the control of the migration of cortical interneurons and the generation of projection neurons during ... [more ▼]

This study focuses on glycine receptors (GlyR) and explores their possible physiological functions on the control of the migration of cortical interneurons and the generation of projection neurons during brain development. Chapter one is the introduction and exposes the context for the experimental work presented in the subsequent chapters. This chapter begins with a description of the characteristics of the brain in terms of its anatomy, morphology, cellular structure and functionality. Then, it focuses on general events that occur during brain development and explains, in general terms, how the main characteristics of the brain emerge starting from cycling progenitors to functional neurons. Subsequently, it separately explains the development of the two major types of neurons present in the cortex, the projection neurons and the interneurons. Following that, there is an introduction to GlyR by describing their properties and physiological roles in the functioning of the central and peripheral nervous system. Finally, the most important studies that link GlyR to a possible role on the brain development are presented and discussed. Chapter two describes the materials and methods that were used during the experimental work. Chapter three presents the results of the study in relation to the effect of GlyR and interneuron development. Based on the literature we hypothesized that activation of GlyR expressed by interneurons can trigger a sequence of molecular events that ultimately contribute to their tangential migration in the forebrain. To test this hypothesis, we performed patch-clamp recordings on interneurons migrating in brain slice culture and demonstrated the functional expression of alpha two homomeric GlyR. Complementary electrophoretic analyses (western blot) and immunolabelings were performed to: 1) confirm the results and unravel the possible dynamic changes that occurred during development; 2) get an insight in the cellular distribution of the receptors. We further explored the possible effects of GlyR activation on cell migration by using time lapse experiments in slices or explant cultures in combination with ex-vivo electroporation. These experiments demonstrated that GlyR activation can change the speed of cell migration by affecting nucleokinesis (translocation of the nucleus towards the centrosome). Therefore, we assessed the effect of GlyR activation on two processes that have been associated with the regulation of nuclear translocation, the spontaneous calcium activity and the phosphorylation of myosin II. Altogether, our results support a mechanism by which GlyR activation depolarizes cell membrane activating voltage gated calcium channels that further contribute to increase intracellular calcium concentration. This increase in intracellular calcium contributes to myosin contraction at the rear of the cell which ultimately controls the frequency of nuclear translocations. VII Chapter four presents experimental results obtained during the study of dorsal progenitors and radially migrating projection neurons. Electrophysiological experiments were carried out to identify and characterize GlyR expressed by progenitors and radially migrating neurons at embryonic day 13 (E13). In addition, calcium imaging was performed to get some insight into the cellular and molecular mechanisms downstream GlyR activation. To understand the physiological relevance of GlyR on these cells, we assessed cell proliferation using pharmacological tools and shRNA-mediated knockdown. Finally, the last two chapters are devoted to a general discussion, the conclusions of the study, and perspectives. [less ▲]

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See detailEtude de la sphéroïdisation de la perlite et de la recristallisation de la ferrite sous champ magnétique
Nutal, Nicolas ULg

Doctoral thesis (2013)

The steel industry is constantly looking for innovations and solutions to improve production processes as well as product properties. However, current technologies result from decades of development and ... [more ▼]

The steel industry is constantly looking for innovations and solutions to improve production processes as well as product properties. However, current technologies result from decades of development and thus have already reached maturity. Therefore, bright innovations have to arise from technological breakthroughs. The objective of those novelties is to induce drastic changes in terms of process or product. Magnetic heat treatment might be a solution to reach both objectives. Indeed, recent researches have shown that magnetic fields can significantly modify the transformation kinetics in steels. This can turn into very positive impacts on the metallurgical processes. However, researches on this topic are in the early stage and a lot of fields have not been studied yet. This work has been carried out in this challenging context. The main objective is to study the effect of magnetic fields on cementite spheroidization and ferrite recrystallization. So far, these two transformations involve long thermal treatments at high temperatures. Thus, a reduction of the processing time or an improvement of the mechanical properties of the steels by using magnetic field processing would be a significant improvement for this kind of thermal treatment. The transformations that are studied imply large microstructure modifications: lamellae breaks into spheroids while ferrite recrystallizes. As a consequence, the developments of dedicated microstructure characterization techniques are concomitant objectives. As it will be shown latter, we decided to develop and optimize image analysis tools. Practically, the completion of this work has required the pursuit of four objectives: Objective 1: develop an image analysis tool dedicated to pearlite spheroidization study, Objective 2: study the effect of magnetic field on cementite spheroidization, Objective 3: develop an image analysis tool dedicated to ferrite recrystallization study, Objective 4: study the effect of magnetic field on ferrite recrystallization. This work is divided in four parts described below. A general introduction constitutes the first part. It contains two chapters. Chapter I focuses on a literature review of the effect of magnetic fields on steels. The first section of this chapter deals with the basics of metallurgy and magnetism required to understand this work. Then, the reader will find a literature review about the effects of homogeneous magnetic fields on steel transformations. As it has been said before, the specificity of this work lies in the fact that the transformations studied were analysed and characterized using image analysis. The Chapter II is dedicated to this technique. The basics of image analysis are summarized in the first section of this chapter. Then, specific sections are dedicated to each step of image analysis: pre-treatment, image segmentation and characterizations. The limits of this technique, as well as its applications are described in the two last sections of this chapter. The second part of this work is divided in three chapters and deals with cementite spheroidization under magnetic field. Chapter III provides a detailed introduction to cementite spheroidization. The first section of this chapter introduces the pearlite as well as its microstructure. Using these concepts, the mechanisms and the kinetic of cementite spheroidization and cementite ripening will be introduced. Finally, the last section of this chapter will focus literature results which indicate that a potential effect of magnetic field on cementite spheroidization might be expected. After this detailed introduction, the tools used to study the cementite spheroidization under magnetic field will be described in Chapter IV. The first section deals with the characterization techniques used to study pearlite spheroidization. Then, the furnace and the heat treatments that have been performed will be described. With these tools, we will describe, in Chapter V, the results that have been achieved about cementite spheroidization under magnetic field. First, we will deeply analyse the effect of temperature and heat treatment duration on cementite spheroidization. This will be the opportunity to study in details the mechanism of cementite spheroidization and spheroids ripening. Microstructure evolutions induced by these two transformations will also be analysed. The effects of magnetic field on cementite spheroidization are described in the last section of this chapter. The analysis of the effect of magnetic field on ferrite recrystallization constitutes the third part of this work. It is divided in three chapters. Chapter VI provides a detailed introduction to ferrite recrystallization. The first section of this chapter deals with the crystalline structure defects induced by the steel forming. The detailed description of the mechanisms and the kinetics of defects elimination by the recovery, primary recrystallization and secondary recrystallization constitute the three next sections of this chapter. The last section of this chapter summarizes the results of different relevant studies on the effects of magnetic fields on these three processes. The chapter VI is followed by a detailed description of the characterization techniques as well as the heat treatment performed to study ferrite recrystallization (Chapter VII). Chapter VIII describes the results that have been obtained about ferrite recrystallization under magnetic field. We will study the effect of temperature and heat treatment duration on ferrite recrystallization. The involved transformations will be studied in detail. Finally, the effect of magnetic field on ferrite recrystallization will be discussed in the last section of this chapter. The general conclusions as well as the prospects of this work will be addressed in the fourth part of this work, respectively in Chapters IX and X. [less ▲]

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See detailCopper phthalocyanine blue pigments in conservation
Defeyt, Catherine ULg

Doctoral thesis (2013)

The phthalocyanine family, and more specifically the copper phthalocyanines (CuPcs) are the most important blue and green artists’ pigments from the end of the 20th century. This thesis focuses on the ... [more ▼]

The phthalocyanine family, and more specifically the copper phthalocyanines (CuPcs) are the most important blue and green artists’ pigments from the end of the 20th century. This thesis focuses on the CuPc blue pigments used in the artists’ paint formulations. CuPc blue extensive use as modern artists’ pigment and its implications in conservation science are pointed out. Their discovery, chemical composition, molecular structure and general properties are also reviewed. Additionally, the polymorphism and the influence of the crystal form on the final properties of the phthalo blue pigments are discussed. A methodology using non-destructive techniques and statistical analysis is then presented. This new procedure allows the identification of the CuPc crystal form in paint layers and is suitable for artwork analysis. Some CuPc polymorphs are prone to crystallization defects in presence of aromatic solvents, leading to a reduction of color strength and a shift in hue. Crystallization resistance of the CuPc polymorphs has then been assessed by means of crystallization tests performed on dry pigments and on paint films. Case studies are then presented. La famille Soler by Picasso has been studied by imaging and non-invasive analytical techniques. The successive underlying compositions have been revealed and the pigments used for the different compositions have been characterized. Then micro-samples taken from Delvaux’s paintings and Francis and Lichtenstein’s studio paints have been analyzed to characterize the blue pigments preferred by these artists. The crystal form of the phthalo blue pigments identified from four micro-samples taken from two Léger and Pechstein fake paintings have been investigated as well. Finally, the historic phthalo blue samples from the Getty Conservation Institute Reference Collection have been studied. [less ▲]

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See detail"Rends excellente ta place de l'Occident". Pour une approche intégrée de la décoration des tombes thébaines sous le règne d'Amenhotep II
Gathy, Maruschka ULg

Doctoral thesis (2013)

Sur l’ensemble des règnes de la XVIIIème dynastie égyptienne, il apparaît, jusqu’assez récemment, que celui d’Amenhotep II a suscité un intérêt moindre de la part des chercheurs, ces derniers lui ayant ... [more ▼]

Sur l’ensemble des règnes de la XVIIIème dynastie égyptienne, il apparaît, jusqu’assez récemment, que celui d’Amenhotep II a suscité un intérêt moindre de la part des chercheurs, ces derniers lui ayant préféré, de manière générale, ceux plus longs ou historiquement plus déterminants de Thoutmosis III, d’Amenhotep III ou encore d’Amenhotep IV – Akhenaton, et ce bien que plusieurs travaux fondamentaux aient déjà permis de mettre en évidence une série de traits spécifiques à cette période. Le règne d’Amenhotep II se caractérise en effet par une nouvelle gestion du gouvernement, où le phénomène d’hérédité qui s’installait progressivement dans certaines fonctions est endigué mais où, dans le même temps, les membres de quelques familles puissantes et particulièrement proches du roi se voient confier les plus hautes charges de l’administration. Aussi, pour la réalisation de leurs « demeures d’éternité », véritables cartes de visite de leurs propriétaires et témoins privilégiés des grandes orientations de l’époque, les principaux officiels du règne d’Amenhotep II ont pour la plupart porté leur choix sur la partie supérieure de la colline de Sheikh Abd el-Gourna, site particulièrement prisé pour sa position surélevée comme pour la proximité qu’il entretient avec les temples funéraires royaux. Les tombes de ces dignitaires se distinguent néanmoins de celles de leurs prédécesseurs, par des dimensions colossales, par l’étendue et la complexité des dispositifs intérieurs ainsi que par le choix de représentations et d’inscriptions qui, placées à des endroits stratégiques, soulignent les relations étroites qu’entretenait le propriétaire avec Pharaon. En outre, le traitement même des scènes figurées est également, à ce moment précis, l’objet de modifications considérables ; l’art pictural, qui se voulait depuis ses origines purement conceptuel et d’apparence hiéroglyphique, s’assouplit à divers égards pour prendre une apparence plus « sensuelle », plus « perceptuelle ». Ces transformations, qui s’amplifieront encore durant les règnes suivants, jettent déjà, en quelque sorte, les bases de ce qui deviendra la « révolution » du règne d’Akhenaton. Dans ce contexte, la présente thèse vise, au moyen d’une analyse pluridisciplinaire et « intégrée » de la décoration des chapelles du règne d’Amenhotep II, à caractériser dans une perspective socioculturelle les changements iconographiques et stylistiques qui affectent cette production artistique en pleine mutation. [less ▲]

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See detailEtude des potentialités hydrogéologiques d’une plaine alluviale en relation avec les eaux souterraines et de surface dans un contexte d’agriculture irriguée (Burkina Faso)
Sauret, Elie ULg

Doctoral thesis (2013)

The Kou river, located in the south-west of Burkina Faso, is intensively exploited for crop irrigation. However, groundwater of the alluvial plain of the Kou river could constitute an alternative to ... [more ▼]

The Kou river, located in the south-west of Burkina Faso, is intensively exploited for crop irrigation. However, groundwater of the alluvial plain of the Kou river could constitute an alternative to surface water for crop irrigation during the dry season. The objective of the present thesis is to study the alluvial aquifer of the Kou river using a approach for (i) characterizing the physical and the hydrodynamic properties of the alluvial plain, (ii) quantifying inflow and outflow in the alluvial plain, (iii) quantifying exchanged fluxes between the alluvial plain and the other reservoirs such as the Kou river and the sedimentary bedrock aquifer, and finally, (iv) calculating a groundwater balance for the alluvial plain for evaluating the volume of water available for crop irrigation. The study of the map showing the lateral and vertical heterogeneity of the alluvial plain indicates that its width is about 300 to 500 m on each side of the Kou river downstream of the Nasso/Guinguette springs. While in the centre of the catchment, the alluvial plain is constituted of clay and sand with a maximum thickness of 15 m, downstream of the catchment, the alluvial plain is constituted of clay, laterite, and weathered bedrock with a thickness of 15 to 45 m. The clayey-sandy sediments in the centre of the catchment constitute a low permeable aquifer (K=10-5 m/s) drained by the Kou river all over the year (gaining section of the river). Conversely, the sediments downstream of the catchment constitute a shallow relatively permeable aquifer (K=10-4 m/s) that drains the Kou river all over the year (losing section of the river). Water exchange between the alluvial plain and the Kou river has been quantified by water balances performed for several sections of the Kou river. Additionally, gaining and losing sections of the Kou river have been determined by direct measurements performed with seepage meters. The hydrochemical analyses performed on samples from tke Kou river, the bedrock, and the springs have shown that (i) groundwater is exchanged between the alluvial plain and the bedrock, and that (ii) Kou river is directly fed by the bedrock or indirectly through springs and alluvial plain, this power supply is facilitated by the system of fractures. The alluvial plain of the Kou river is a groundwater reservoir with a storage-drainage function. During the dry season, the alluvial plain stores groundwater coming from the bedrock and discharges it into the Kou river. Conversely, downstream of the catchment, the Kou river is drained by the alluvial plain that stores of important water resources intensively exploited for crop irrigation. [less ▲]

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See detailSustainable housing in Vietnam: Climate responsive design strategies to optimize thermal comfort
Nguyen, Anh Tuan ULg

Doctoral thesis (2013)

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

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

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See detailProjectively Invariant Quantization in Super Geometry
Leuther, Thomas ULg

Doctoral thesis (2013)

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See detailMise au point d’un protocole de multiplication in vitro de Jatropha curcas L. en vue d’une application à grande échelle
Medza Mve, Samson Daudet ULg

Doctoral thesis (2013)

Jatropha curcas L. is a wild plant, that emerged as a source of energy for biodiesel production. It has acquired significant economic potential as it does not compete with the edible oil supplies ... [more ▼]

Jatropha curcas L. is a wild plant, that emerged as a source of energy for biodiesel production. It has acquired significant economic potential as it does not compete with the edible oil supplies. Realizing its importance, in vitro multiplication methods have been established to meet the demand of large scale supply of superior clones. In order to improve the in vitro multiplication rate (number of shoots/explant/subculture/three weeks) of J. curcas, axillary nodes taken from young plants of two accessions (originating from Cameroon and Senegal) have been cultivated for three weeks on a Murashige and Skoog (1962) medium (MS) supplemented with 8.87 µM BAP, 4.92 µM IBA, and 30 g/l sucrose at pH 5.7±0.1, and solidified with 0.7% agar. The shoots obtained from each original explant were then transferred to a multiplication media consisting of MS medium supplemented with 2.21 to 8.9 μM BA or 2.21 to 8.9 μM kinetin in combination with 2.46 μM IBA. Each combination was completed with 12.2 mg.l-1 adenine sulfate and 25 mg.l-1 of glutamine. The best multiplication rate was obtained for the PM medium containing 6.65 μM BA and 2.46 μM IBA. The mean multiplication rate is 8.1 shoots per explant during the 7 following subcultures. Leafy shoots obtained have been rooted in a medium containing half of the major mineral and minor mineral components of MS supplemented with 5.7 μM IBA, then acclimated with a survival rate of 97%. With the aim of finding a more efficient production protocol practicable on a large-scale, an alternative method has been developed to regenerate whole plants of J. curcas from nodes via the induction of buds aggregates. Histological observation shows that bud aggregates are simultaneously formed through axillary budding and adventitious regeneration of buds. These buds are elongated in MS medium supplemented with 2.21 µM BA, 5.70 µM IAA (indole-3-acetic acid) and 15 mg.l-1 L arginine. The leafy stems are then rooted on MS containing 2.46 µM IBA, 2% sucrose, and 0.7% agar. The entire process takes 14 weeks with 98% plants survival after acclimatization. We obtain a multiplication rate of 13 buds per explant per subculture. This protocol is more efficient than previously known protocols. [less ▲]

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See detailEtude des propriétés de repliement d’une protéine hélice bêta parallèle droite la pectine méthylesterase d’Erwinia chrysanthemi 3937
Guillerm, Jessica ULg

Doctoral thesis (2013)

The aim of protein folding studies is to elucidate the process by which a polypeptide chain spontaneously adopts its functional three-dimensional structure in vivo. This issue, known as the « protein ... [more ▼]

The aim of protein folding studies is to elucidate the process by which a polypeptide chain spontaneously adopts its functional three-dimensional structure in vivo. This issue, known as the « protein folding problem », is one of the major challenges in modern structural biology. Indeed, a better understanding of the fundamental principles underlying protein folding could have many applications, either in the understanding of various diseases related to protein misfolding, in the exploitation of advances in genomics, or in the design of proteins with new functions. Pectin methylesterase of Erwinia chrysanthemi 3937 (PemA) was chosen as a model protein for folding studies. It is a 37 kDa protein that is involved in the degradation of pectin, a major component of the plant cell wall. This enzyme has a right-handed parallel beta-helix structure, which has been proposed as a plausible model to describe the structure of amyloid fibrils. Characterization of PemA thermodynamic properties led to the determination of its conformationnal stability, whereas kinetic studies highlighted occurence of at least two obligatory intermediates on the folding patway of the the protein when it acquires its native structure. We first developed an effective procedure to obtain the protein of interest in sufficient quantities to perform various biophysical studies. PemA gene was cloned into an expression vector allowing improved production yields of the recombinant protein. The purification protocol was also improved and we developed an efficient activity test in order to probe the functionality of the enzyme.The conformational stability of PemA was assessed by destabilizing the native protein using different denaturing agents (guanidinium chloride, urea, temperature, pH, pressure) and probing the structural integrity of the protein with the help of one or more spectroscopic technique(s) (fluorescence, circular dichroism and FTIR spectroscopy). Data showed that PemA is particularly resistant to high pressure, while its chemical and thermal stability are in the range of what is commonly observed for mesophilic proteins. On the other hand, characterization of PemA folding kinetics highlighted that it folds along a sequential pathway, characterized by the formation of at least two obligatory kinetic intermediates. Simulation of the kinetics on the basis of the experimental data reinforced the view that PemA folding is adequatly described by a four states model. [less ▲]

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See detailIntérêt de l'épidémiologie et des modèles animaux expérimentaux dans l'étude des valvulopathies en cardiologie humaine et équine
Leroux, Aurélia ULg

Doctoral thesis (2013)

Valvular regurgitations are one of the most common causes of cardiac diseases in humans and in domestic animals. Clinical studies, epidemiological studies, and animal experimental models have been ... [more ▼]

Valvular regurgitations are one of the most common causes of cardiac diseases in humans and in domestic animals. Clinical studies, epidemiological studies, and animal experimental models have been developed to test new diagnostic and therapeutic techniques. Electrocardiography, Doppler echocardiography, angiography, magnetic resonance imaging (MRI) and computed tomography are currently used in clinical practice for diagnosis and prognosis. Medical management and, in humans, surgical treatments can increase life expectancy and improve quality of life of cardiac patients. In horses, cardiac clinical abnormalities including murmurs and arrhythmias are relatively common while the prevalence of clinically significant cardiac diseases is low. However, investigation of these with ECG and Doppler echocardiography is recommended as even mild cardiac abnormalities may lead to significant cardiac disease and cause poor performance in sport horses. To our knowledge, risk factors for several cardiac diseases have been suspected in equids. Few have been statistically demonstrated in a large equine population, since most studies about cardiac murmurs or arrhythmias concerned only racehorses. The first aim of this research work was to perform an epidemiological study in a large equine population to describe risk factors for various cardiac diseases. The prevalence of main cardiac diseases in the studied population was in accordance with previously described prevalence as mitral regurgitation (MR), atrial fibrillation (AF), aortic regurgitation (AR) and tricuspid regurgitation (TR) were the most frequently observed cardiac diseases. Various risk factors of these cardiac diseases were statistically demonstrated: Ageing and male gender appear to predispose to AR, TR appears to affect middle-aged patients, and AF was significantly more common in larger and heavier horses. Moreover MR was an important cardiac disease since it led to congestive heart failure (CHF) whereas AR was not a direct risk factor for CHF. Functional ischemic MR is one of the main human valvular diseases and is caused by ischemic cardiomyopathy with one or more prior myocardial infarctions involving most commonly the basal posterolateral myocardium of the left ventricle (LV). The therapeutic approach to functional MR is difficult and still controversy as regards the timing and the nature of the treatment. To our knowledge, no percutaneous large animal model of functional MR has been conceptualized. This model would be the first one to allow studying the dynamic component of functional MR. Therefore the second aim of this work was the development of an experimental animal model of functional ischemic MR. Goats appeared as good candidates for the model as they fulfill all requested conditions. They have a body and heart size comparable to that of humans and can be handled easily even during exercise tests. As few publications are available in this species, three first studies were designed to test the repeatability and to establish the reference values of measurements obtained using Two-Dimensional (2D), M-Mode, Pulsed-wave (PW) Doppler and 2D speckle tracking (2DST) echocardiography in unsedated standing adult goats. Standardized echocardiographic protocols were performed three times by the same observer at one day interval on 10 to 12 goats and the intra-observer inter-day repeatability and variability was calculated. 2D and M-Mode echocardiography showed a good inter-day repeatability and a low variability of the cardiac measurements, whereas PW Doppler measurements had a poor inter-day repeatability and a moderate variability. Caprine 2DST parameters demonstrated a poor but acceptable repeatability and a high variability and allowed determination of significant physiologic differences between measurements at rest and after exercise. Then the experimental model of functional ischemic mitral regurgitation induced by a percutaneous approach in goats was developed. This experimental study was conducted in two steps: first, the study of the goat coronary arteries anatomy to determine the best myocardial infarction location to induce ischemic MR in adult Saanen goats and, secondly, the development and the imaging characterization of the goat model of functional ischemic MR. The anatomic pattern of the coronary artery system of the goat was determined using casts made of auto polymerizing resin. Two coronary arteries branches were highlighted from the results of this anatomical study: the left marginal branch (LMB) and the posterior descending branch (PDB) of the left circumflex artery, which could supply the posterolateral wall of the LV. Then myocardial infarction was induced by microcoil embolization of LMB, PDB, or both, under fluoroscopic guidance. The results confirmed that LMB and PDB occlusion produced a large myocardial infarction and an immediate severe functional MR (n=3) unlike only LMB (n=2) or only PDB occlusion (n=2). Mortality rate of this model was high (56%), particularly when LMB and PDB were simultaneously occluded (87,5%). After the myocardial infarction, a complete follow-up was performed in each surviving goat using echocardiographic techniques previously described and MRI. 2DST techniques allowed quantifying LV dysfunction during acute ischemic MR. Quantification of functional MR was performed by Doppler techniques including measurements of the vena contracta width, the effective regurgitant orifice area and the regurgitant volume using the proximal isovelocity surface area method (PISA), and by 2D-echocardiographic technique analyzing the geometrical distortion of the mitral apparatus in mid-systole (tenting area and coaptation distance). Finally, MRI confirmed the location of myocardial ischemia and the presence of functional MR. These findings make this model an interesting alternative to study the pathophysiology of the functional ischemic MR, especially for its dynamic component yielding useful prognostic information. In conclusion, the two major aims of this research were met: the prevalence of various cardiac diseases and their risk factors in a large population of equids were described and an experimental model of functional ischemic mitral regurgitation induced by a percutaneous approach in goats was developed. This model of experimental ischemic MR could be useful to further study the pathophysiology of the functional ischemic MR, especially for its dynamic component and to maximize further treatment in problem patients. Our epidemiologic study confirmed that horses with cardiac murmurs or arrhythmias and presenting demonstrated risk factors, should routinely undergo ECG and Doppler echocardiography to diagnose and to evaluate the severity of any pathological cardiac abnormalities and to identify potential signs of evolution into CHF, including the presence of multiple cardiac diseases and enlargement of the cardiac chambers. [less ▲]

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See detailMaison, architecture domestique et société dans le Moyen-Euphrate et la Djézireh syrienne à l'âge du Bronze
Mas, Juliette ULg

Doctoral thesis (2013)

Cette thèse s’est attachée à l’étude de l’architecture domestique et de la société dans les régions du Moyen-Euphrate et de la Djézireh syrienne à l’âge du Bronze. L’étude a été fondée sur la constitution ... [more ▼]

Cette thèse s’est attachée à l’étude de l’architecture domestique et de la société dans les régions du Moyen-Euphrate et de la Djézireh syrienne à l’âge du Bronze. L’étude a été fondée sur la constitution d’un vaste catalogue regroupant les vestiges de 375 maisons mises au jour sur 35 sites. L’attention a été portée sur différents aspects techniques de ces édifices ainsi que sur les aménagements, le matériel in situ et les tombes qui y ont été découvertes. Différentes séries statistiques ont été tirées du corpus et confrontées à nos connaissances sur le contexte historique, politique, social et économique de la région, selon des axes synchronique et diachronique. Or, l’âge du Bronze, qui couvre plus d’un millénaire offre l’opportunité de mieux comprendre les phénomènes de discontinuité et d’évolution des structures socio-économiques. Les débuts de la période ont vu l’émergence des sociétés complexes et stratifiées, organisées par des structures étatiques, dans le cadre des établissements urbains. Le système économique y était déjà très articulé et, au delà des grandes organisations palatiales, était au moins en partie basé sur les activités de groupes privés, qui, dans certains cas, étaient structurés par des liens de parenté. L’analyse de la masse documentaire réunie a permis de tester certaines hypothèses proposées par de précédentes études sur l’architecture domestique, d’en formuler de nouvelles et enfin de proposer un modèle interprétatif permettant d’expliquer la diversité typologique des habitations de ces régions à l’âge du Bronze par le degré de stratification économique de leurs occupants, le plus élevé correspondant à des groupes ayant développé leurs propres moyens de subsistance et s’apparentant à des entreprises privées. [less ▲]

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See detailEtude prospective des caractéristiques hématologiques, biochimiques et urinaires du Dogue de Bordeaux: Une race prédisposée à une glomérulopathie familiale
Lavoué, Rachel ULg

Doctoral thesis (2013)

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

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

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See detailEvaluation expérimentale de l'impact thoracique des projectiles non-létaux
Robbe, Cyril ULg

Doctoral thesis (2013)

On constate depuis une vingtaine d'années une augmentation significative de l'emploi d'armes non-létales, aussi bien au sein des forces de l'ordre que du côté militaire. L'idée est effectivement ... [more ▼]

On constate depuis une vingtaine d'années une augmentation significative de l'emploi d'armes non-létales, aussi bien au sein des forces de l'ordre que du côté militaire. L'idée est effectivement séduisante: pouvoir stopper ou neutraliser la cible, sans lui occasionner de blessures graves, ou de lésions permanentes, voire létales. La technologie actuellement prépondérante consiste en le tir d'un projectile, généralement très déformable, à l'aide d'un lanceur pneumatique ou d'une arme à feu classique, à des vitesses de l'ordre de 100 m/s. L'impact provoque une douleur, qui amène à la neutralisation ou à l'obtempération de la cible. En pratique, on constate que ces armes provoquent néanmoins des blessures graves et même létales, d'où la nécessité de mettre au point des méthodes d'évaluation avant leur mise sur le marché. Les impacts au niveau du thorax, zone d'impact prépondérante, sont caractérisés par des lésions plus importantes que pour d'autres parties du corps, à l'exception de la tête qui n'est jamais visée. Les lésions observées consistent en des blessures provoquées par un impact non-pénétrant, ou en la pénétration du projectile dans l'organisme. Une étude de la littérature sur le sujet oriente cette recherche vers les résultats obtenus à l'Université de Wayne State, par le professeur C. Bir. Ainsi, le critère lésionnel de l'impact non-pénétrant étudié dans cette thèse sera le (VC)max, même si la méthode mise en place est adaptable à tout autre critère. Par ailleurs, l'étude de la pénétration de la peau s'inspirera d'un modèle anthropomorphique ou "surrogate", également développé par C. Bir. La méthode d'évaluation proposée dans ce travail combine des mesures expérimentales et des simulations numériques. La présente thèse s'intéresse exclusivement à l'aspect expérimental, l'aspect numérique faisant l'objet d'une autre thèse développée au département ABAL (Systèmes d'Armes et Balistique) de l'Ecole Royale Militaire. Les deux tests expérimentaux mis au point consistent en des tirs de projectiles non-létaux respectivement sur une cible supposée infiniment rigide, équipée d'un capteur de force, et sur le "surrogate" susmentionné. Ces deux tests nécessitent l'emploi d'un lanceur pneumatique, développé pour l'occasion, qui permet de tirer l'intégralité des projectiles aux vitesses voulues. Ses caractéristiques inédites apportent entière satisfaction tout au long de l'étude. L'emploi du "surrogate" ne nécessite qu'une mesure de vitesse avant l'impact, tandis que les mesures réalisées lors du tir sur le mur rigide consistent en une mesure de vitesse avant l'impact, ainsi que de force et de déplacement du projectile pendant l'impact. La mesure de force est effectuée à l'aide d'un capteur piézoélectrique, les deux autres sont réalisées à l'aide d'une caméra haute-vitesse. L'emploi de celle-ci nécessite le développement d'un logiciel de poursuite dédié à l'application de mesures dynamiques d'impacts de projectiles non-létaux. Ce logiciel apporte une flexibilité, une précision et quantité d'information jusque là jamais atteintes. Les résultats consistent alors en la prise de ces mesures pour six projectiles commerciaux et un projectile en développement. Un énorme effort est fourni pour quantifier les incertitudes de mesure. celles-ci sont calculées grâce à l'emploi du logiciel de poursuite dédié et constituent une originalité supplémentaire de cette thèse. Finalement l'ensemble des résultats expérimentaux sont collationnés et intégrés dans l'approche hybride expérimentale et numérique pour évaluer le potentiel lésionnel de l'impact non-pénétrant et de l'impact pénétrant, à différentes vitesses d'impact, pour le projectile Spartan LE 40 mm de Nobel Sport et le FN303. Les données obtenues pour ces deux projectiles sont ensuite reliés à des distances de tirs. Trois systèmes d'armes sont alors étudiés: le F2000 pour le projectile 40 mm, et le FN303 et FN303p pour le projectile FN303. Grâce à une étude de dispersion et d'efficacité supplémentaire, les résultats définitifs permettent de dimensionner des distances minimum et maximum d'engagement, qui garantissent un tir sûr et efficace. [less ▲]

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See detailQuasi-One-Dimensional Numerical Simulations of Post-Stall Compression Systems
Du, Wenhai ULg

Doctoral thesis (2013)

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See detailLe potentiel du saule pour la phytostabilisation des sols pollués par les éléments-traces métalliques
Evlard, Aricia ULg

Doctoral thesis (2013)

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

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

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See detailContributions to Recognizability: Self-generating Sets, Decidability, Automaticity and Multidimensional Sets
Lacroix, Anne ULg

Doctoral thesis (2013)

In this thesis, we study and answer several questions concerning recognizability of integer sets by finite automata. Each particular problem is the focus of a chapter. First, we study the recognizability ... [more ▼]

In this thesis, we study and answer several questions concerning recognizability of integer sets by finite automata. Each particular problem is the focus of a chapter. First, we study the recognizability of the so-called self-generating sets, initially introduced by C. Kimberling. In the second part, we study the syntactic complexity of any ultimately periodic set and we use our results to give an alternative decision procedure for a well-known decidability problem. Next, we give bounds on the automaticity of three different languages: the language of primitive words over a finite alphabet, the language of unbordered words over a finite alphabet and the language of representations of monic irreducible polynomials over a finite fields. Finally, we characterize the multidimensional sets that are recognizable in all abstract numeration systems. [less ▲]

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See detailLiquidité des titres, communication financière et gouvernance d’entreprise
Ajina, Aymen ULg

Doctoral thesis (2013)

A travers ce travail doctoral, nous cherchons à étudier l’influence des mécanismes de gouvernance d’entreprise sur la liquidité des titres. Nous nous focalisons aussi sur l’efficacité et la qualité du ... [more ▼]

A travers ce travail doctoral, nous cherchons à étudier l’influence des mécanismes de gouvernance d’entreprise sur la liquidité des titres. Nous nous focalisons aussi sur l’efficacité et la qualité du système de gouvernance en passant d’une étude fragmentée des mécanismes de contrôle à une étude systémique de la gouvernance d’entreprise. Les résultats défendent une orientation législative française envers l’adoption de certaines normes pour la bonne conduite de la gouvernance d’entreprise. L’étendue des informations publiées dans les rapports annuels augmente la visibilité d’une entreprise, réduit éventuellement l’asymétrie d’informations et augmente la liquidité des titres. Ces effets sont d’autant plus prononcés par l’application des normes IFRS rendues obligatoires à partir de 2005. Par ailleurs, nous montrons que le développement de la demande d’actionnariat institutionnel est une nécessité pour le marché parisien, afin de favoriser sa croissance de façon générale et soutenir sa liquidité. Nous mettons en évidence également un impact positif de la taille du conseil d’administration, de l’indépendance et de l’expertise financière des administrateurs, et du nombre des réunions du conseil sur la liquidité des titres. De même, le comité d’audit offre un support indispensable pour prévenir le risque « d’illiquidité ». [less ▲]

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See detailVariabilité de la respiration hétérotrophe du sol dans des écosystèmes agricoles: Analyse à différentes échelles spatiales et temporelles.
Buysse, Pauline ULg

Doctoral thesis (2013)

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

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

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See detailLa Bibliothèque miroir : Gabriel Naudé et le libertinage érudit
Decoster, Sara ULg

Doctoral thesis (2013)

Cette thèse est centrée sur la figure de Gabriel Naudé, l’auteur d’un Avis pour dresser une bibliothèque (1627, 1644). Comme ce traité reflète tant la doctrine politique de l’auteur que sa vision sur le ... [more ▼]

Cette thèse est centrée sur la figure de Gabriel Naudé, l’auteur d’un Avis pour dresser une bibliothèque (1627, 1644). Comme ce traité reflète tant la doctrine politique de l’auteur que sa vision sur le savoir, le texte constitue le point de départ pour une analyse détaillée de l’œuvre de l’auteur. Il importe en effet de resituer la pensée de Naudé dans le courant très complexe du libertinage érudit. En soi, les idées de Naudé concernant la bibliothèque ne sont effectivement pas novatrices. Ce constat s’impose comme une évidence lorsque l’opuscule est réinséré dans son contexte. Il s’avère que le bibliothécaire expose d’une manière concise des idées largement répandues, qui rejoignent les préoccupations de la République des lettres. La bibliothèque naudéenne épouse l’irénisme de la communauté intellectuelle et se veut accessible au public. Cette conception très ouverte pose de front le problème de la relation des libertins avec le pouvoir. Dans une France rongée par les guerres de religion et d’incessantes révoltes populaires, Naudé a lié son sort au régime absolutiste, qui était seul à pouvoir garantir la stabilité nécessaire au bonheur commun. Pourtant, Naudé démystifie impitoyablement les mécanismes d’un état qui utilise la religion pour mieux gouverner les âmes. Son œuvre possède donc un potentiel subversif important, qui s’explique par des motifs sociologiques. C’est que Naudé revendique sa place dans la société en tant qu’intellectuel, comme la théorie du jeu permet de le démontrer. En ce qui concerne le contenu de la bibliothèque, il s’agit clairement d’une bibliothèque docte, qui embrasse tous les domaines du savoir. Si Naudé accueillit les hypothèses non prouvées, il reste très attaché aux bases solides de la tradition. Toutefois, pour lui, l’érudition doit être éclairée par les lumières de la raison, ce qui implique que le savoir est soumis à l’exigence de l’efficacité. La vraie connaissance ne s’embarrasse pas de détails inutiles. Le lettré se concentre sur les aspects réellement porteurs de progrès, au lieu de verser dans un esthétisme inutile. D’ailleurs, le véritable savoir ne s’enferme pas dans une tour d’ivoire, mais s’intègre dans la vie civile. La méthode d’analyse de Naudé est philologique. Le libertin préfère la profondeur érudite à l’empirie, comme le montre clairement sa manière d’appréhender la médecine. Pourtant, il ne s’intéresse pas davantage à l’analyse de textes qu’aux sciences naturelles. En réalité, la pensée de Naudé est une pensée métaréflexive, définissant les caractéristiques de l’esprit fort. Le bibliothécaire crée les conditions de possibilité pour l’avancement du savoir, mais s’abstient de produire des travaux d’envergure lui-même. C’est cette conception qui préside à la bibliothèque naudéenne : il s’agit d’un lieu de développement du savoir, dont tous les aspects sont soumis au paradigme de l’utilité. Cette logique s’applique à toutes les composantes de la collection. De fait, les objets non livresques que Naudé intègre dans sa bibliothèque s’avèrent très fonctionnels. [less ▲]

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See detailLa structuration du monde paysan au Rwanda : cas des coopératives et des stations de lavage de café de Maraba et de Karaba, District de Huye
Gisaro Ca-Madeberi, Ya-Bititi ULg

Doctoral thesis (2013)

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

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

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See detailLes contraintes à la valorisation écotouristique du Parc National des ïles Ehotilé (Littoral sud est de la Côte d'Ivoire)
Kouakou, Guy Eric Anicet Quassy ULg

Doctoral thesis (2013)

Under the pressure of the environmental financiers and within the framework of the reform of its conservation policy of the protected areas, the Côte d’Ivoire State decided to preserve, to valorize spaces ... [more ▼]

Under the pressure of the environmental financiers and within the framework of the reform of its conservation policy of the protected areas, the Côte d’Ivoire State decided to preserve, to valorize spaces protected by the ecotourist approach. The first field of experiment of this approach was the National Park of Islands Ehotilé. But decade after the implementation of this policy, this initiative has difficulty in being set up. The question is to know what are the determining factors of failure of the process of ecotourist exploitation in the PNIE? To answer this question, this research, approached according to a multidisciplinary approach, suggests studying the progress of two experiences of ecotourism in the PNIE (A project introduced by the WWF and financed by the English cooperation, and an other, set up by a local NGO financed by the Global Environment Facility), to identify and analyze the factors of inhibition of the ecotourist process in this park. Analyses (quantitative and qualitative) were made from the data collected in ten waterside villages of the PNIE, through structured or semi-structured interview. These conversations also concerned the state departments (in charge of the preservation and of the tourism), the local authorities, the local administrators, the initiators of projects. We also proceeded to the consultation of several sources of documentation. The obtained results show that the material, legal and institutional conditions were not performed at the time of the political decision-making of implementation of the approach of preservation by the ecotourism. In a general way, the hotel, road infrastructures, the socio-sanitary equipments inside and outside are of inferior quality even non-existent. The tourist development (no observation, runways, landing stage) inside the park has been lacking. It was revealed also no promotional support (advertising, web site, etc.) exists to sell the PNIE. At the legal and institutional level, the legal and institutional requirements are on straddle between those mobilized by the actors of the tourism and those used by the actors of the preservation without synergy between these two groups of participants. The results also allowed to highlight the existence of a multitude of participants in interaction in and the periphery of the PNIE, characterized by differences of interests and logics of action as much at the level of the priorities of actions as means of carrying out the ecotourist exploitation of the PNIE. What was lacking in the attempt of putting in ecotourism of this park, it is the capacity to make compatible these differences of interests and logics of action, and the possibility of coordinating them. Our study also revealed differences of vision and representations towards the resources of the PNIE in the attempt of putting in ecotourism of this park. These differences concern the ancestral dimension, as well as the use values of this protected space. These conflicts are indicator of an elaboration and an inadequate management of the mechanism of ecotourist production in connection with the non-inclusion of the diverse social representations mobilized by the various actors of the projects. Besides, the convergences of representations mentioned with the actors concern "myths". The myth of the “ancestralité” bases itself on the ancestral link of the local residents with the islands of the park and appears for the promoters of the projects of ecotourist development as the element which has to justify the membership of the local populations. There is also a mythical version of the natural potentialities of the park which bases itself on the presence of exceptional species that " we do not find somewhere else ". The myth of the tourism as the vector of protection and development was also indicated. The problem is that, in the process of ecotourist valuation, the participants do not question any more these mythical versions mobilized around the PNIE. The latter appear for these participants as an obvious fact; not arousing question, they are not really worked to become resources. Finally, the results showed that the attempt of development of the ecotourism in the PNIE is marked by a governance, - in terms of piloting of the projects -, characterized by a series of uninsured coordinations or which are failing. The ecotourist projects tended to push aside or to make a weak place to the actors responsible for the park, to the actors of the territorial administration and to the actors of the tourism. In political terms, it was missing a space of coordination and piloting of this coordination. After all, recommendations are made to revitalize and strengthen the conditions of implementation and management of experiences of ecotourism in the PNIE and generally in the parks of Côte d’Ivoire. These recommendations would aim at improving the questions connected to the organizational, regulatory aspects and of planning. [less ▲]

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See detailThe International Liquid Mirror Telescope project: optical quality tests and prospective detection of multiply imaged quasars
Finet, François ULg

Doctoral thesis (2013)

The International Liquid Mirror Telescope (ILMT) project is a joint collaboration between different universities and research institutes in Belgium, Canada, India and Poland, for the design, construction ... [more ▼]

The International Liquid Mirror Telescope (ILMT) project is a joint collaboration between different universities and research institutes in Belgium, Canada, India and Poland, for the design, construction and operation of a 4 meter liquid mirror telescope at the Devasthal Observatory (India). In the framework of the present thesis, we have contributed to the development of the ILMT. We have namely designed and manufactured an innovative instru- ment capable of measuring the optical quality of the primary mirror that may be affected by the propagation of wavelets on the mercury layer. The instrument is composed of a laser source, emitting a beam whose reflection on the mirror is modulated by slope variations induced by the wavelets. Preliminary tests were carried out showing the validity of the method for on site testing of the mirror. The ILMT has been designed to perform a photometric variability survey of a narrow strip of sky, making it very suitable for the detection and follow-up of photometrically variable sources such as supernovae and quasars. In the second part of this thesis, we present an estimate of the number of QSOs to be detected within the ILMT survey, and of the expected number of multiply imaged sources among these caused by the presence of a deflector near the lines-of- sight. We have studied the impact of various parameters on the expected number of detected gravitational lens systems, such as the instrumental resolution of the telescope, the galaxy population type(s) and corresponding lensing model(s), and the cosmological parameters. The statistical sample of multiply imaged QSOs is intended to be used as a cosmological probe. In order to make a sensitivity comparison between vari- ous modelling approaches, we introduce a new formalism to estimate the lensing probabilities, based on the joined probability density of the observed QSOs. This new formalism allows to calculate three probability densities: that asso- ciated with the optical depth distribution, as well as those related to the deflector and the lensed source redshift distributions. For the case of FLRW universes, we compare the sensitivity of these distributions as a function of the cosmological mass density. [less ▲]

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See detailINFLUENCE DE L'ENCLAVEMENT SUR LE DEVELOPPEMENT RURAL (Cas du territoire d'OPALA, District de la Tshopo, R. D. Congo)
Bolakonga Ilye, Antoine Bily ULg

Doctoral thesis (2013)

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

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

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See detailDevelopment of a high-order interior penalty discontinuous Galerkin method for compressible turbulent flows. Application to Reynolds-averaged Navier-Stokes and large eddy simulations
Drosson, Marcus ULg

Doctoral thesis (2013)

Over the last decade several studies and workgroups came to the conclusion that high-order discretisation schemes are the most suited to overcome the limitations of today’s flow solvers. The latter are at ... [more ▼]

Over the last decade several studies and workgroups came to the conclusion that high-order discretisation schemes are the most suited to overcome the limitations of today’s flow solvers. The latter are at most second-order accurate and therefore often deliver poor results on currently used meshes. Within this context, discontinuous Galerkin (DG) methods have recently been identified as having the biggest potential for future flow solvers. Further research is however needed to improve the computational efficiency and the robustness of these schemes. Both issues are faced in the subsequent chapters of the thesis. The first part of the thesis is devoted to the solution of the Reynolds-averaged Navier-Stokes (RANS) equations using an interior penalty (IP) formulation. Whereas the intention is not to develop new turbulence models, the focus lies on the adaptation of existing models to the particular features of high-order discretisation schemes. In contrast to classical low-order methods, high-order schemes are prone to Gibbs oscillations which – if no care is taken – can lead to the breakdown of the algorithm. Given the stability issues caused by negative values of the eddy viscosity, different changes of the one-equation Spalart-Allmaras (S-A) model are discussed. Whilst having identical sparsity patterns as the popular second Bassi-Rebay scheme (BR2), the simpler IP formulation is up to 30% less time-consuming. Unfortunately, its stability strongly depends on a seemingly more or less arbitrary penalty parameter. As this parameter also effects the conditioning of the resulting system of discretised equations, its choice is of utmost importance. This might explain why the IP formulation has received only little attention over the past decades. The thesis analyses for the first time the use of the interior penalty discretisation to solve a system of RANS equations. One of the principal contributions of this work is the generalisation of the penalty parameter to anisotropic meshes and a highly variable viscosity. Several numerical examples are presented to illustrate the effect of the newly proposed definition of the penalty parameter. The focus of the second part lies on turbulent boundary layer resolution. Based on detailed grid convergence analyses as a function of interpolation order, element type and grid size, clear guidelines for the choice of boundary layer meshes for practical applications are provided. Besides straight boundaries, the effect of boundary curvature or a hybrid discretisation are investigated. Moreover, the concept of “quasi-straight” elements is introduced. Following this innovative approach, the accuracy of the calculated shear friction can further be improved by a proper choice of the position of the inner-element nodes, without increasing the total number of unknowns. Finally, several numerical applications clearly demonstrate the potential of the method to solve industrial problems. In the last part, large eddy simulations of the Taylor-Green vortex and the decay of homogeneous isotropic turbulence are presented. This last chapter constitutes a first step towards the use of discontinuous Galerkin methods for large eddy simulations. Besides a validation study for the Smagorinsky and the WALE subgrid scale model, the resolution requirements of resolved LES are determined. Furthermore different subgrid filters are compared and the choice of the Smagorinsky constant in the case of filtered LES is briefly examined. [less ▲]

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See detailLarge-scale alignments of quasar polarisations: a detailed study of the spinless-particle scenario
Payez, Alexandre ULg

Doctoral thesis (2013)

The main motivation for our work has been a puzzling observation concerning quasars. No one expected the existence of correlations in the polarisation of visible light coming from objects separated by ... [more ▼]

The main motivation for our work has been a puzzling observation concerning quasars. No one expected the existence of correlations in the polarisation of visible light coming from objects separated by gigaparsecs, until they were first reported in the form of a redshift-dependent effect that has become more and more significant with the growth of the data sample. In close connexion with the observational group, we have studied in detail the most widely considered scenario, involving axion-photon mixing in extragalactic magnetic fields. After a systematic investigation, we conclude that it is very unlikely that these observations can be accounted for by axion-like particles, given current data and constraints. We also derive new limits on the parameters describing these particles. This thesis gives in particular a detailed account of the consequences of axion-photon mixing on polarisation, studies the influence of averages over the frequency (including a wave-packet treatment of the mixing), and discusses the consequences of different magnetic-field morphologies. [less ▲]

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See detailLa charge vocale : De sa quantification à l’étude de son impact sur la fonction phonatoire et sur la qualité vocale
Remacle, Angélique ULg

Doctoral thesis (2013)

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

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

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See detailContribution à l'étude des amylases du sorgho et leurs utilisations dans la transformation des produits amylacés
Ba, Khady ULg

Doctoral thesis (2013)

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

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

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See detailLe vagabondage de l'esprit : aspects cognitifs, affectifs et neuronaux des pensées découplées des situations et tâches en cours
Stawarczyk, David ULg

Doctoral thesis (2013)

Dans ce travail de thèse, nous avons défini et validé une conceptualisation plus précise du vagabondage de l’esprit en tant que pensées à la fois stimulus-indépendantes et non-liées à la tâche en cours en ... [more ▼]

Dans ce travail de thèse, nous avons défini et validé une conceptualisation plus précise du vagabondage de l’esprit en tant que pensées à la fois stimulus-indépendantes et non-liées à la tâche en cours en distinguant clairement celles-ci des pensées interférentes liées à la tâche et des distractions externes. À l’aide de cette conceptualisation, nous avons exploré quatre aspects peu étudiés ou sujets à débats du vagabondage de l’esprit que sont les fonctions possibles de ce phénomène, ses soubassements cérébraux, le lien qu’il entretient avec les capacités de contrôle de l’attention, ainsi que la nature de la relation entre le vagabondage de l’esprit et les affects négatifs. Les résultats des études réalisées au sein de ce travail suggèrent qu’une fonction importante du vagabondage de l’esprit concerne la planification et la préparation des évènements futurs en lien avec nos buts et projets personnels. Notre travail démontre par ailleurs que le vagabondage de l’esprit est sous-tendu par un ensemble spécifique de régions cérébrales (généralement référenciées sous le terme de réseau du mode par défaut) et que ce phénomène représente plus que des échecs au niveau des processus de contrôle de l’attention en impliquant notamment un état d’attention découplée de l’environnement présent. Nous avons également montré que le vagabondage de l’esprit peut résulter d’une augmentation des affects négatifs et que sa présence est associée au maintien de ces affects dans le temps. Le fait que les individus qui vagabondent le plus en pensées font l’expérience d’un plus haut taux d’affects négatifs pourrait être expliqué par une moindre conscience et attention portées au moment présent. Sur base de ces résultats, nous avons proposé une perspective intégrative du vagabondage de l’esprit qui suppose que ce phénomène représente l’accès à la conscience, à travers un espace de travail global limité, des processus de mise à jour des scripts, schémas et plans stockés en mémoire à long terme et sous-tendus par le réseau du mode par défaut. La fonction de ces scripts, schémas et plans serait de guider les comportements des individus en formant une plate-forme cognitive impliquée dans la génération de prédictions relatives au futur. Nous avons dès lors proposé que le vagabondage de l’esprit peut représenter un phénomène adaptatif mais uniquement lorsque les bénéfices de ces pensées en termes de préparation et de planification du futur dépassent leurs conséquences délétères sur la qualité de l’attention portée à la tâche en cours et au moment présent. [less ▲]

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See detailThe transcription factor Egr1 in zebrafish cartilage development
Dalcq, Julia ULg

Doctoral thesis (2013)

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

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

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See detailMécanismes de l'anosognosie: une étude sémiologique et par imagerie fonctionnelle.
Jedidi, Haroun ULg

Doctoral thesis (2013)

La maladie d’Alzheimer constitue une affection fréquente et très invalidante tant sur le plan individuel que social ou affectif. Elle s’inscrit comme un objectif majeur de recherche dans la mesure où elle ... [more ▼]

La maladie d’Alzheimer constitue une affection fréquente et très invalidante tant sur le plan individuel que social ou affectif. Elle s’inscrit comme un objectif majeur de recherche dans la mesure où elle constitue de par sa fréquence, les complications qu'elle entraîne et les soins multidisciplinaires lourds et coûteux qu'elle nécessite, un enjeu majeur pour l'économie de la santé des pays industrialisés. L’anosognosie qui complique souvent le décours de la maladie est un symptôme complexe, variable dans sa présentation tant au fil de l’évolution de la maladie que d’un patient à l’autre. La présence de l’anosognosie peut notamment compliquer le diagnostic ou la prise en charge voire mettre en jeu la sécurité du patient ou de ses proches. Elle peut, virtuellement, intéresser tous les domaines de la cognition. Tant sa prévalence que les mécanismes qui la sous-tendent au niveau anatomique ou fonctionnel demeurent méconnus et largement débattus dans la littérature. Dans cette optique, les corrélats neuraux de l’anosognosie doivent être mieux précisés et intégrés dans un modèle de fonctionnement global de la conscience de soi. Le domaine de l’anosognosie et en particulier celui de l’anosognosie portant sur les traits de la personnalité demeure donc un champ de recherche ouvert ou de nombreux travaux doivent encore être réalisés. C’est dans cette optique que nous avons choisi de mener notre étude. Le propos de notre ouvrage est donc l’étude des mécanismes de l’anosognosie par une approche tant comportementale que par le biais de la neuroimagerie fonctionnelle (IRMf et TEP). Au vu de l’étendue et de la complexité du sujet abordé, nous avons centré notre travail sur l’anosognosie portant sur les traits de personnalité. Au niveau cérébral, nous avons tout particulièrement étudié l’implication des régions préfrontales médiales dans ces processus de représentation de soi et dans la genèse de l’anosognosie portant sur les traits de personnalité. Notre première étude avait pour objectif d’étudier l’activité et la spécialisation fonctionnelle des régions préfrontales médiales au cours de la réflexion sur soi. Pour ce faire nous avons présenté à des volontaires jeunes une série d’adjectifs descriptifs. Durant l’acquisition en IRMf les sujets devaient juger à quel point ces adjectifs les décrivaient ou non. Juste après l’acquisition fonctionnelle, les sujets devaient à nouveau juger à quel point les mêmes adjectifs les décrivaient et de surcroît, ils devaient préciser à quel point ils avaient la certitude de posséder ou non ce trait de caractère et à quel point il était important pour eux de le posséder ou non. Les analyses de régression réalisées à partir de ces données ont démontré que l’activité au sein du cortex préfrontal dorsomédial étant corrélée à une évaluation de nature cognitive (certitude de posséder un trait de personnalité) et l’activité du cortex préfrontal ventromédial paraissant associée à des processus de nature émotionnelle (importance de posséder un trait de personnalité). Notre seconde étude avait comme objectif d’explorer les corrélats neuraux de l’anosognosie portant sur les traits de personnalité dans la maladie d’Alzheimer. Nous avons donc étudié une population de sujets présentant une maladie d’Alzheimer débutante et une population de sujets âgés sains auxquelles nous avons présenté divers questionnaires de jugement de personnalité. Nous avons également acquis une image du métabolisme cérébral de repos à l’aide de la TEP au 18 FDG chez ces patients et ces contrôles. Les résultats de cette étude suggèrent que l’anosognosie portant sur les traits de personnalité ne repose probablement pas entièrement sur un déficit de réactualisation des informations autobiographiques et du Self mais peut également être le fruit d’un déficit au niveau des capacités de prise de perspective à la troisième personne. Cette étude suggère également que le cortex préfrontal dorsomédial joue probablement un rôle dans ces mécanismes de prise de perspective. Notre troisième étude avait pour but d’évaluer le modèle dit « à deux voies » du syndrome de Capgras (Ellis et Young, 1997) qui constitue le modèle dominant de ce trouble dans la littérature et d’étudier l’implication des régions préfrontales médiales dans les processus de récupération des informations liées à un visage, de prise de perspective et de référence à autrui ou à soi-même. Pour ce faire nous avons acquis une image structurelle (en IRM) et une image fonctionnelle au repos (à l’aide de la TEP) du cerveau de notre patiente et nous avons comparé ces images à celles d’un groupe de sujets sains et de sujets présentant une maladie d’Alzheimer débutante. Les résultats de cette étude remettent quelque peu en question les corrélats anatomiques du modèle à deux voies du syndrome de Capgras et compte tenu des mécanismes actuellement connus de la reconnaissance des visages, semblent apporter de nouveaux arguments à l’hypothèse d’un rôle de centre d’intégration des informations liées à un visage et de la représentation d’autrui pour le cortex dorsomédial préfrontal. L’ensemble des résultats de ce travail démontre encore une fois combien les mécanismes de l’anosognosie et ceux de la conscience de soi sont complexes, intriqués et encore largement méconnus. Nous avons pu souligner l’importance du cortex préfrontal médial dans les processus de réflexion sur soi et d’évaluation du Self et en préciser la sous spécialisation fonctionnelle, l’activité au sein du cortex préfrontal dorsomédial étant corrélée à une évaluation de nature cognitive et l’activité du cortex préfrontal ventromédial paraissant associée à des processus de nature émotionnelle. Nous avons également pu démontrer que l’anosognosie portant sur les traits de personnalité actuelle semble davantage liée à une altération des capacités de prise de perspective tierce qu’à un déficit de réactualisation des informations autobiographiques (petrified Self). Ce dysfonctionnement des capacités de prise de perspective a également pu être corrélé à un dysfonctionnement (hypométabolisme) des régions préfrontales dorsomédiales. La dernière partie de notre travail nous permet en outre d’envisager et de mieux comprendre la complexité du rôle de ces structures préfrontales médiales et en particulier du cortex préfrontal dorsomédial, qui semble constituer, comme l’ont déjà suggéré plusieurs auteurs, un carrefour d’intégration important pour un ensemble complexe de processus cognitifs impliqués dans la représentation d’autrui, des ses intentions et de ses états mentaux, constituant ainsi une partie prenante du réseau cérébral ayant souvent été désigné par le terme de cerveau social (social brain). [less ▲]

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See detailModified TiO2-based Photocatalytic Films and Powders produced by Aqueous and Non-Aqueous Sol-Gel Processes for Water Purification
Malengreaux, Charline ULg

Doctoral thesis (2013)

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

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

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See detailLa neuroinvasion dans les maladies à prions: étude de l'interface neuroimmune FDC - système nerveux sympathique
Demonceau, Caroline ULg

Doctoral thesis (2013)

Prion diseases are neurodegenerative diseases affecting the central nervous system (CNS) wherein the PrPd disease-associated prion infectious agent is an abnormal isoform of PrPc host-encoded cellular ... [more ▼]

Prion diseases are neurodegenerative diseases affecting the central nervous system (CNS) wherein the PrPd disease-associated prion infectious agent is an abnormal isoform of PrPc host-encoded cellular prion protein. The process through which the prion infectious agent is transferred to the CNS, the neuroinvasion, is still unknown, but secondary lymphoid organs seem to play an important role in prion amplification prior the invasion of the associated peripheral nervous system (PNS). In particular, modifications of follicular dendritic cells (FDC) and sympathetic nervous system (SNS) of lymphoid organs could influence the speed of neuroinvasion, and thus the length of the disease incubation period. It was shown that the lack of mature FDC prevents the replication of the infectious agent in secondary lymphoid organs. Likewise, sympathectomy delays the onset of the disease, and enhances sympathetic innervation reduces the incubation period. In mice, the relative positioning of FDC and sympathetic neural fibres plays a role in the incubation period following scrapie inoculation. This study thus focuses on the neuroimmune interface between FDC and sympathetic neural fibres. First, the number of close interactions between FDC and sympathetic neural fibres of five mouse strains with the same Prnpa genotype was estimated to check if it could explain the different incubation period observed after inoculation of primary bovine spongiform encephalopathy (BSE) infected-brain. Then we checked if scrapie infection, by oral or intraperitoneal route, could influence this neuroimmune interface between FDC and sympathetic neural fibres within Peyer’s patches (PP) and spleen of the C57BL/6 mouse strain. In the first part of this work, co-localizations between FDC and sympathetic neural fibres were observed in vivo within germinal centers (GC) of mouse spleen. Among the five mouse strains exhibiting the same Prnpa genotype, three strains (RIII-1, RIII-2 and 129/Ola) showed an incubation period about 100 days shorter than those of C57BL and C57BL/6 mouse strains when inoculated with primary BSE. Moreover, amplification by FDC seems an obligatory process before subsequent neuroinvasion as an intracerebral inoculation doesn’t reduce the incubation period observed with an intraperitoneal inoculation. A meticulous analysis revealed that the density of close interactions between FDC and sympathetic neural fibres is not higher for the three mouse strains with a shorter incubation period. However, these three mouse strains with a shorter incubation period after primary BSE inoculation have a higher proportion of FDC networks with close interactions than the mouse strains with a longer incubation period. These results suggest that it is not the quantity of sympathetic neural fibres close to FDC, but rather the percentage of FDC with close sympathetic neural endings that could influence the incubation period of prions diseases. In the second part of this work, it came out that prion infection did not result in neuronal loss within the PNS like observed in the CNS, and also did not modify the FDC-SNS neuroimmune interface of secondary lymphoid organs where PrPd deposits are observed within germinal centers. For a single mouse strain orally infected with scrapie, neither FDC networks hypertrophy nor sympathetic neural fibres closer than 10 μm from a FDC network were observed within GC of PP. Moreover, in our conditions, the prion strain did not seem to alter the neuroimmune interface between FDC and SNS in PP that could explain the different incubation periods observed with the 139A and ME7 scrapie strains. To check if prion infection does not modify the FDC-SNS neuroimmune interface, close interactions between FDC and sympathetic neural fibres already shown in the spleen were analyzed in the same mouse strain intraperitoneally infected with the 139A scrapie strain. In that case as well, no differences were observed in FDC network hypertrophy, in the in vivo density of sympathetic neural fibres closer than 10 μm from a FDC network, or in the proportion of well innervated FDC networks, compared to control mice. An in vitro model of coculture of splenic FDC from the same C57BL/6 mouse strain with nerve cells from dorsal root ganglia (DRG) also yielded similar results. FDC isolated from scrapie 139A infected mice exhibited the same neuritogenic or neurotrophic effects than FDC isolated from control mice. During these experiments, it was also noted that young-adult or middle-age mice showed both the same mean density of close interactions between FDC and SNS. However, with age, even if the splenic volume occupied by FDC networks halved, the proportion of FDC networks with close interactions almost doubled. It would be very interesting to check this last parameter in old mice that show some delay in neuroinvasion of prion disease but also to evaluate if this percentage of well innervated FDC network contributes to the prion pathogenesis within the spleen. In conclusion, scrapie 139A and ME7 strains don’t modify FDC-SNS neuroimmune interface of secondary lymphoid organs, not allowing explaining the different incubation period observed with equivalent infectious doses. Moreover, following an oral inoculation of prion, neuroinvasion within PP would not involve direct contact between FDC and sympathetic nerves, but rather another process still to be determined or implying other nerve fibres and/or mobile cells such as macrophages or dendritic cells. However, in the spleen, the percentage of FDC networks with close sympathetic neural fibres – rather than the number of sympathetic neural fibres close to the FDC network – observed for a given age, species and Prnp genotype at the time of inoculation could play a role in the different incubation periods observed for the same prion strain. The cellular compounds involved in the specific FDC microenvironment still have to be determined for each cell implied in the neuroinvasion process. [less ▲]

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See detailContribution à l'étude des mécanismes transcriptionnels du facteur de transcription SIP1/ZEB2
Koopmansch, Benjamin ULg

Doctoral thesis (2013)

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

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

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See detailAutomatic target recognition using passive bistatic radar signals
Pisane, Jonathan ULg

Doctoral thesis (2013)

We present the design, development, and test of three novel, distinct automatic target recognition (ATR) systems for the recognition of airplanes and, more specifically, non- cooperative airplanes, i.e ... [more ▼]

We present the design, development, and test of three novel, distinct automatic target recognition (ATR) systems for the recognition of airplanes and, more specifically, non- cooperative airplanes, i.e. airplanes that do not provide information when interrogated, in the framework of passive bistatic radar systems. Passive bistatic radar systems use one or more illuminators of opportunity (already present in the field), with frequencies up to 1 GHz for the transmitter part of the systems considered here, and one or more receivers, deployed by the persons managing the system, and not co-located with the transmitters. The sole source of information are the signal scattered on the airplane and the direct-path signal that are collected by the receiver, some basic knowledge about the transmitter, and the geometrical bistatic radar configuration. The three distinct ATR systems that we built respectively use the radar images, the bistatic complex radar cross-section (BS-RCS), and the bistatic radar cross-section (BS- RCS) of the targets. We use data acquired either on scale models of airplanes placed in an anechoic, electromagnetic chamber or on real-size airplanes using a bistatic testbed consisting of a VOR transmitter and a software-defined radio (SDR) receiver, located near Orly airport, France. We describe the radar phenomenology pertinent for the problem at hand, as well as the mathematical underpinnings of the derivation of the bistatic RCS values and of the construction of the radar images. For the classification of the observed targets into pre-defined classes, we use either extremely randomized trees or subspace methods. A key feature of our approach is that we break the recognition problem into a set of sub-problems by decomposing the parameter space, which consists of the frequency, the polarization, the aspect angle, and the bistatic angle, into regions. We build one recognizer for each region. We first validate the extra-trees method on the radar images of the MSTAR dataset, featuring ground vehicles. We then test the method on the images of the airplanes constructed from data acquired in the anechoic chamber, achieving a probability of correct recognition up to 0.99. We test the subspace methods on the BS-CRCS and on the BS-RCS of the airplanes extracted from the data acquired in the anechoic chamber, achieving a probability of correct recognition up to 0.98, with variations according to the frequency band, the polarization, the sector of aspect angle, the sector of bistatic angle, and the number of (Tx,Rx) pairs used. The ATR system deployed in the field gives a probability of correct recognition of 0.82, with variations according to the sector of aspect angle and the sector of bistatic angle. [less ▲]

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