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See detailAmélioration de l’efficience d’utilisation de l’eau chez les principales cultures fourragères au Tadla- Maroc
Bouazzama, Bassou ULg

Doctoral thesis (2013)

Aiming to define irrigation strategies improving the water productivity by folder crops under water scarcity in the irrigated perimeter of Tadla (Morocco), this work combines field experimentation and ... [more ▼]

Aiming to define irrigation strategies improving the water productivity by folder crops under water scarcity in the irrigated perimeter of Tadla (Morocco), this work combines field experimentation and modeling. The field study of crop response to water stress is important to maximize yield and improve agricultural water use efficiency (WUE) in areas where water resources are limited. On the silage maize, the results showed that water deficit affected plant height growth, accelerated the senescence of the leaves and reduced the leaf area index. Dry matter yields varied from 3.9 t.ha-1 under T5 (20% ETc) to 16.4 t.ha-1 under T1 (100% ETc). The establishment of the water budget by growth phase showed that the water use efficiency was higher during the linear phase of growth. WUE calculated at harvest varied between 2.99 kg.m-3 under T1 and 1.84 kg.m-3 under T5. The actual evapotranspiration under T1 (100% ETc) was 478 mm and 463 mm in 2009 and 2010, respectively. The yield response factor (Ky) for the silage maize for both growth seasons was 1.12. The ETc of silage maize was determined using lysimeter drainage at 415 mm. the mean values of crop coefficients Kc were 0.56, 1.22 and 1.05 for beginning phase, mid-season and at harvest (grain milky pasty stage) respectively. Drip irrigation allows obtaining dry matter yields similar to flood irrigation but with less water and saves about 30% of irrigation water applied. Over five cycles, berseem dry biomass yields achieved under T1 are 14.3 and 13.9 t/ha in 2009/10 and 2010/11 respectively. The yield reductions by applying 60% of water requirements are 40 and 42% in 2009/10 and 2010/11 respectively. Berseem daily productivity increases with more water applied with the highest value of 102 kg DM/ ha/ day. The dry matter content increases with water stress. The mean values range between 12.3 and 23.7% under T1 (100% ETc) and T4 (40% ETc) respectively. The contribution of without irrigation cycles (rainy period) on the total annual yield may vary from 35% to 52% under treatments T1 and T4 respectively. Water balance achieved by water regime shows that drainage losses increase with more water applied especially in the first cycle. WUE is low during the first cycle, optimal in 2nd, 3rd and 4th cycle and decreases in the last one with water stress. Global WUE of berseem determined over the entire crop period (slope of the regression line) is 3.37 kg.m-3. The yield response factor (Ky) for the berseem for both growth season was 1.11. Berseem ETc determined by drainage lysimeter was 520 mm. The Kc values were estimated for each cycle for all three phases: initial, development (median) and mid-season. Maximum yield average under drip irrigation was 15.7 t/ha and obtained with 411 mm of water supply allowing to save 57% of water compared to traditional irrigation technique. Comparing the behavior of six alfalfa varieties most commonly practiced in the irrigated perimeter of Tadla shows that the "Super Siriver" cultivars followed by «Trifecta» have higher yield potential and higher tolerance to water deficit. Alfalfa maximum annual yield obtained was 24.2 t.ha-1. The contribution of the spring cycles to the annual yields range from 55% under T1 (100% ETc) to 65% under T4 (40 % ETc). In addition to water quantities, alfalfa yields depend on time application during a growth cycle. WUE varies from cycle to another and from one season to another. The maximum value was 2.57 kg.m-3 and obtained in spring 2011, while the low value was 0.64 kg.m-3 and obtained in winter 2010. WUE decreases with water stress, with mean values of 1.83, 1.67, 1.54 and 1.23 kg.m-3 under T1 (100% ETc), T2 (80% ETc), T3 (60% ETc) and T4 (40% ETc) respectively. The yield response factor (Ky) of alfalfa was 0.92. The determination of the alfalfa water requirements was performed on the basis of cycle’s calendar during two years in 2010 and 2011. The values founded for flood irrigation are 1388 and 1364 mm respectively for the two years. Drip irrigation allows achieving similar dry mater yield to flood irrigation with less water and agronomic efficiency. Water applied under T1 in drip irrigation with 50 cm of spacing between ramps was less than water requirements (of alfalfa) by about 7% and 18% in 2010 and 2011 respectively. Under the same treatment in flood irrigation, the water requirements are exceeded by 16% and 21% in 2010 and 2011 respectively. Two crop models, PILOTE and CropSyst, had been selected to be tested on their ability to simulate the growth and yield of the studied crops under the edaphic-climatic conditions of Tadla. Tested on silage maize, both models correctly simulated the growth and development of the crop under different water regimes. The parameters of both models are validated and shown effective for simulation of biomass, leaf area index and soil water storage. Although PILOTE requires less parameters and data than CropSyst, it often proves to be more successful in simulating the biomass of silage maize and water balance. As to berseem, predictions of biomass by CropSyst seem to be more accurate than PILOTE model. The latter was best at predicting the soil water reserve on the soil depth exploited by the roots (0-80 cm). Given its ease of integrating daily climatic data for several years, CropSyst model was chosen to test its ability to simulate the crop rotation of berseem and maize silage. The results show that this model correctly simulates the evolution of biomass and yields of the two crops considered in rotation during three years. Modeling the growth and production of alfalfa is made by both models outside the crop installation period (seeding year). After calibration and validation achieved, the model CropSyst simulates adequately biomass and soil water reserve under all water regimes considered while PILOTE best simulations were limited to non-stressed treatment T1 (100% ETc). Although CropSyst model takes into account several parameters in the simulation of alfalfa growth, their simplifications (unique values) reduce its performance in more water stress situation. Less parameters considered in the PILOTE model makes it validation difficult for perennial crops such as alfalfa. CropSyst model was used to evaluate irrigation practices of farmers and develop irrigation virtual scenarios for the three crops studied. The assessment shows that virtual scenario developed for alfalfa that applying 1600 mm of irrigation water amount through 14 applications divided into six irrigations during the spring, six in summer, one in the fall and another in early winter maximizes irrigation water efficiency (1.21 kg/m3) and achieve a yield of 23.1 t/ha (95% of the yield potential). In the case of maize, if water is available, application of 648 mm according to the combination [2 irrigations in initial phase (after sowing), 2 irrigations in linear and two in final phases] allows to achieve high biomass yield and better water use. On berseem, the simulation results confirm that the adoption of the scenario that provides 625 mm through 7 irrigations (3 in autumn, 2 in winter and 2 in spring) allows obtaining 14.1 t/ha of dry matter which represents 94% of the yield potential of the 6454 cultivar. This scenario allows greater water efficiency (1.24 kg/m3) and results in low water drainage losses estimated at about 17% of applied water. The comparison of the two cropping systems represented by alfalfa and silage maize-berseem rotation shows that the rotation allows the better water use and mobilizes less water than alfalfa, which is distinguished by its profitability. Finally, the coupling of the results of three years (2008 to 2011) "in situ" experimentations with the simulations of scenarios by CropSyst and PILOTE models has shown to be highly effective in order to improve the folder crops irrigation in the Tadla irrigated area in Morocco. [less ▲]

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See detailFundamental and Applied Studies on Freeze-dried Vinegar Starter
Shafiei, Rasoul ULg

Doctoral thesis (2013)

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See detailDynamique d’une espèce ligneuse héliophile longévive dans un monde changeant : le cas de Pericopsis elata (Harms) Meeuwen (Fabaceae) au sud est du Cameroun
Bourland, Nils ULg

Doctoral thesis (2013)

The Central African forests are characterized by high species richness. While little light generally reaches their litter layer, among the species encountered are major long-lived light-demanding logged ... [more ▼]

The Central African forests are characterized by high species richness. While little light generally reaches their litter layer, among the species encountered are major long-lived light-demanding logged trees. These species may have established in the past because of large disturbances. Indeed, major climate changes have occurred in the past few millennia, in some areas coupled with strong human occupations. Among these light-demanding species we find the assamela / afrormosia (Pericopsis elata (Harms) Meeuwen, Fabaceae), a large high trading value tree of African semi-deciduous moist forests. Nowadays this logged species suffers from significant regeneration problems on its natural range from Ghana to the Democratic Republic of Congo. Therefore, it is included in CITES Appendix II and is recorded as “Endangered A1cd” on the IUCN Red List. No convincing solution can be found in the available scientific literature to overcome the deficiency of its regeneration. In addition, little or no information is available describing ca. its population dynamics, genetics, silviculture or the probable origin of its stands. It is in this context that the present PhD was undertaken. In this study, we have adopted a multidisciplinary approach to understanding the dynamics of this population rich in long-lived light-demanding species logged in the Congo basin. Moreover, we have suggested ways for their management and conservation in a changing world. To do so, we have adopted as a study-model the case of P. elata in southeastern Cameroon. The main results of the study show that, on a local scale, physico-chemical soil parameters have no influence on the presence or absence of this clustered species. However, on the same scale, large quantities of charcoal were found in the soil, mainly inside those clusters. The anthracological analysis has also shown that the vegetation at the time of the burn was similar to that of today. Numerous fragments of pottery were also found in the top soil layers only inside clusters formed by the species. Finally, some 14C datings go back to ca. 200 years BP, which is approximately the average age of concerned clusters. This body of evidence leads us to conclude on an ancient form of shifting cultivation as the most likely origin of the assamela populations currently present in southeastern Cameroon. In addition to its current population structure within the study area, several parameters controlling its population dynamics were estimated. While the annualized natural mortality of the species reaches about 1%, its average diameter growth rate is 0.31 cm.year-1, which is a relatively low value compared to other long-lived light-demanding species. Selective logging seems to have only a light influence on the behavior of the species. On the other hand, the impact of logging on its seed tree populations is only ca. 12%. Each seed tree bears fruit on average only once every five years. The minimum diameter of reproduction and the effective flowering diameter were respectively 32 and 37 cm. The recovery rate, varying greatly from one country to another, is more than 100% in Cameroon, where the conservation status assigned to the species seems excessive. A sufficient regeneration by planting should allow the perpetuation of the assamela populations in the long run, as with other major logged light-demanding trees. [less ▲]

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See detailOn the Verification of Programs on Relaxed Memory Models
Linden, Alexander ULg

Doctoral thesis (2013)

Classical model-checking tools verify concurrent programs under the traditional "Sequential Consistency" (SC) memory model, in which all accesses to the shared memory are immediately visible globally, and ... [more ▼]

Classical model-checking tools verify concurrent programs under the traditional "Sequential Consistency" (SC) memory model, in which all accesses to the shared memory are immediately visible globally, and where model-checking consists in verifying a given property when exploring the state space of a program. However, modern multi-core processor architectures implement relaxed memory models, such as "Total Store Order" (TSO), "Partial Store Order" (PSO), or an extension with locks such as "x86-TSO", which allow stores to be delayed in various ways and thus introduce many more possible executions, and hence errors, than those present in SC. Of course, one can force a program executed in the context of a relaxed memory system to behave exactly as in SC by adding synchronization operations after every memory access. But this totally defeats the performance advantage that is precisely the motivation for implementing relaxed memory models instead of SC. Thus, when moving a program to an architecture implementing a relaxed memory model (which includes most current multi-core processors), it is essential to have tools to help the programmer check if correctness (e.g. a safety property) is preserved and, if not, to minimally introduce the necessary synchronization operations. The proposed verification approach uses an operational store-buffer-based semantics of the chosen relaxed memory models and proceeds by using finite automata for symbolically representing the possible contents of the buffers. Store, load, commit and other synchronization operations then correspond to operations on these finite automata. The advantage of this approach is that it operates on (potentially infinite) sets of buffer contents, rather than on individual buffer configurations, and that it is compatible with partial-order reduction techniques. This provides a way to tame the explosion of the number of possible buffer configurations, while preserving the full generality of the analysis. It is thus possible to even check designs that may contain cycles. This verification approach then serves as a basis to a memory fence insertion algorithm that finds how to preserve the correctness of a program when it is moved from SC to TSO or PSO. Its starting point is a program that is correct for the sequential consistency memory model (with respect to a given safety property), but that might be incorrect under TSO or PSO. This program is then analyzed for the chosen relaxed memory model and when errors are found (a violated safety property), memory fences are inserted in order to avoid these errors. The approach proceeds iteratively and heuristically, inserting memory fences until correctness is obtained, which is guaranteed to happen. [less ▲]

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See detailEnzymatic synthesis of glycosylated compounds in non-conventional media
Galonde, Nadine ULg

Doctoral thesis (2013)

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See detailStudy of the roles of Cyprinid herpesvirus 3 ORF134 in the biology of the infection
Ouyang, Ping ULg

Doctoral thesis (2013)

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

The common carp is one of the most important freshwater fish species in aquaculture, and its colourful subspecies koi is grown for personal pleasure and competitive exhibitions. Both two subspecies are economically important. In the late 1990s, a highly contagious and lethal pathogen called koi herpesvirus (KHV) or cyprinid herpesvirus 3 (CyHV-3) began to cause severe financial losses in these two carp industries worldwide. In 2005, CyHV-3 has been classified in the Alloherpesviridae family of the order Herpesvirales. Because of its economic importance and its numerous original biological properties, CyHV 3 became rapidly an attractive subject for applied and fundamental research. However, to date, there is a little information on the roles of individual CyHV-3 genes in the biology of CyHV-3 infection or its pathogenesis. Moreover, there is a lack of safe and efficacious vaccine for the control of CyHV-3 disease. The goal of this thesis was to study the roles of CyHV-3 ORF134 encoding an IL-10 homologue in the biology of the infection. CyHV-3 ORF134 has been predicted to contain an 84 bp intron flanked by 2 exons encoding together a 179 amino acid product. Transcriptomic analyses reveal that ORF134 is expressed as a spliced early-late gene. The identification of the CyHV-3 secretome was achieved using 2D-LC MS/MS proteomic approach. This method led to the identification of 5 viral and 46 cellular proteins in concentrated infected cell culture supernatant. CyHV-3 ORF12 and ORF134 were amongst the most abundant proteins detected. To investigate the roles of ORF134 in the biological of the infection, a strain deleted for ORF134 and a derived revertant strain were produced by using BAC cloning and prokaryotic recombination technologies. Comparison of these strains demonstrated that CyHV-3 ORF134 does not contribute significantly to viral growth in vitro or to virulence in vivo in the present laboratory setting. The present study addressed for the first time the in vivo role of a vIL-10 encoded by a member of the family Alloherpesviridae. This study has been published in Veterinary Research. During the course of the first study, we obtained an unexpected recombination event while we were reconstituting infectious virus from mutated BAC plasmids. To generate a revertant ORF134 Del galK strain, CCB cells were co-transfected with the FL BAC ORF134 Del galK plasmid and the pGEMT-TK vector to remove the BAC cassette inserted in the ORF55 locus (encoding thymidine kinase). One of the clones obtained had an unexpected recombination leading to the deletion of ORF56 and ORF57 in addition to the expected deletion of ORF134. Unexpectedly, this triple deleted strain replicated efficiently in vitro, exhibited an attenuated phenotype in vivo and was proved to confer in a dose dependent manner an immune protection against a lethal challenge. The goal of the second experimental chapter was to investigate the role of the ORF56-57 and ORF134 deletions in the observed safety/efficacy profile of the triple deleted recombinant. To reach this goal, a collection of recombinant strains were produced using BAC cloning technologies, characterized and tested in vivo for their safety/efficacy profile. The results obtained demonstrated that the ORF56-57 deletion is responsible for the phenotype observed and that ORF134 deletion does not contribute to this phenotype significantly. Finally, the immune protection conferred by ORF56-57 deleted recombinant was investigated by challenging immunized fish with a wild type strain expressing luciferase as a reporter gene. In vivo imaging system (IVIS) analyses of immunized and challenged fish demonstrated that the immune response induced by the ORF56-57 deleted strain was able to prevent subclinical infection of the challenge strain. In conclusion, the present thesis addressed both fundamental and applied aspects of CyHV-3. For the first time, it investigated in vivo the roles of a viral IL-10 homologue encoded by a member of the family Alloherpesviridae. Importantly, it identified the ORF56-57 loci as target for production of safe and efficacious attenuated recombinant vaccines. [less ▲]

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See detailLe Rhin aux époques romaines. Zone grise, frontière, branchements
Dignef, Anthony ULg

Doctoral thesis (2013)

Dans cette thèse de doctorat, j’ai repris l’étude des processus et des conditions d’émergence et d’existence, de stabilisation et d’évolution de la frontière du Rhin aux époques romaines, c’est-à-dire ... [more ▼]

Dans cette thèse de doctorat, j’ai repris l’étude des processus et des conditions d’émergence et d’existence, de stabilisation et d’évolution de la frontière du Rhin aux époques romaines, c’est-à-dire essentiellement les périodes post-républicaine et impériale, de César à Valentinien Ier. L’idée était de procéder à une nouvelle analyse des dynamiques liées au phénomène frontalier. Ainsi, dans un souci d’élargissement du domaine de l’histoire militaire généralement attendue, j’ai tenté le difficile exercice de l’appréhension du système de limite du Nord-Ouest de l’Empire, par une relecture croisée des problématiques de l’affirmation du pouvoir romain, des transformations socio-politiques des sociétés en marge de l’Empire, et des façons dont celles-ci ont conditionné la frontière du Rhin. Ce travail dépasse donc largement le cadre d’une étude des installations frontalières, lesquelles ont déjà considérablement retenu l’attention des chercheurs. Il tient, en outre, et probablement davantage, de l’histoire politique, de l’histoire des relations internationales et de l’histoire connectée, telle que je l’ai découverte à travers les travaux de Sanjay Subrahmanyam et de Romain Bertrand. [less ▲]

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See detailAdaptation de la procédure de Maquet pour le traitement chirurgical de la rupture du ligament croisé crânial chez le chien
Etchepareborde, Sébastien ULg

Doctoral thesis (2013)

La rupture du ligament croisé crânial est la première cause d’ostéoarthrose chez le chien. Récemment, une étude a évalué à plus d’un milliard de dollars le chiffre d’affaire que générait cette pathologie ... [more ▼]

La rupture du ligament croisé crânial est la première cause d’ostéoarthrose chez le chien. Récemment, une étude a évalué à plus d’un milliard de dollars le chiffre d’affaire que générait cette pathologie annuellement aux Etats-Unis. Bien que la rupture du ligament croisé crânial (RLCC) soit la cause la plus fréquente de boiterie du membre postérieur rencontrée dans les centres de référés, aucune technique chirurgicale ne semble prévaloir sur les autres. La pléthore de publications sur la RLCC, pas moins de 160 articles consacrés à ce sujet au cours des 6 dernières années dans les 5 plus importantes revues de chirurgie vétérinaire, témoigne du manque de consensus dans ce domaine. Si les chirurgies intracapsulaires ou la physiothérapie uniquement sont les méthodes les plus employées en médecine humaine pour traiter la rupture du ligament croisé antérieur (RLCA), elles se sont montrées insatisfaisantes en médecine vétérinaire. Les techniques extracapsulaires utilisées depuis des décennies se sont vues, elles aussi, remplacées par des techniques de stabilisation dite dynamique : principalement l’ostéotomie de nivellement du plateau tibial (Tibial Plateau Levelling Osteotomy : TPLO) et l’avancement de la tubérosité tibiale (Tibial Tuberosity Advancement : TTA). Cette dernière chirurgie est une adaptation d’une technique utilisée chez l’homme et décrite par P. Maquet en 1976. Bien que la technique se réalise sans aucun implant synthétique chez l’homme, la technique décrite chez le chien présente de nombreux implants pour stabiliser la crête tibiale une fois son avancement réalisé. La mise en place de ces implants entraine une approche invasive de la face médiale du tibia. Les objectifs de ce travail sont d’adapter progressivement la TTA originalement décrite, pour la simplifier telle qu’elle est réalisée chez l’homme, c’est à dire avec pour seul implant un bloc placé dans le trait d’ostéotomie. Cette simplification s’inscrit dans le mouvement actuel de chirurgie minimalement invasive avec une préservation optimale des tissus. En référence à son inventeur chez l’homme, nous avons baptisé cette chirurgie la Technique de Maquet Modifiée (Modified Maquet Technique : MMT). Dans la première étude, le trait d’ostéotomie décrit dans la technique de TTA a été modifié pour laisser intact la partie la plus distale de la corticale de la crête tibiale créant ainsi une « charnière » osseuse. Après cette nouvelle ostéotomie, la résistance à la traction de la crête tibiale a été testée dans trois cas de figures : 1) lorsque la charnière est intacte et la crête maintenue par un fil de cerclage, 2) lorsque la charnière est intacte mais non maintenue et 3) lorsque la charnière est accidentellement cassée, la crête étant maintenue uniquement par un fil de cerclage. Cette étude biomécanique a montré que lorsque la charnière est intacte, le fil de cerclage n’augmente pas la résistance du montage et que la crête tibiale résiste à des tensions supérieures à celles rencontrées dans le grasset d’un chien au pas. En revanche, si la charnière est cassée, la tension tolérée par la crête est significativement inférieure à celle des deux autres groupes. Dans une deuxième étude, la technique nouvellement testée a été utilisée sur un panel de 20 chiens présentés pour une RLCC. Malgré l’absence de plateforme de marche pour évaluer objectivement la récupération fonctionnelle, la MMT a montré des résultats prometteurs et subjectivement comparables à ceux des autres techniques de stabilisation dynamique. Le temps moyen de cicatrisation de la crête était inférieur à 7 semaines, ce qui est dans la moyenne publiée pour la TTA. Aucune complication majeure n’a nécessité de réintervention dans cette étude préliminaire. Une étude prospective avec une plateforme de marche permettrait de comparer directement ces résultats à ceux déjà publiés sur la TTA. Grâce à notre expérience tant ex-vivo que clinique, il nous est apparu que le trait d’ostéotomie tel que nous l’avions décrit pour réaliser cette charnière osseuse n’était pas optimal. En effet, le trou foré à l’extrémité distale de l’ostéotomie, censé prévenir la propagation de fissures lors de l’avancée de la tubérosité tibiale, non seulement n’empêchait pas toujours l’apparition de telles fissures mais était, de plus, toujours le site de fracture de la crête tibiale dans les rares cas où nous l’avons observée. Au lieu de concentrer toutes les contraintes de la déformation osseuse au niveau de cette charnière, nous avons donc eu l’idée de prolonger distalement l’ostéotomie parallèlement à la corticale afin de diminuer les contraintes de déformation. Cette troisième étude nous a permis de tester de manière approfondie ce nouveau trait d’ostéotomie. Nous en avons conclu que l’avancement maximal autorisé était proportionnel au poids du chien et à l’avancée angulaire de la crête ; la résistance maximale était proportionnelle à l’épaisseur de la charnière. Grâce à cette nouvelle ostéotomie, pour toutes les catégories de chiens, l’avancement permis était supérieur aux valeurs utilisées cliniquement. Par ailleurs, la résistance de la crête à la traction était encore supérieure à celle décrite dans notre première étude. Notre quatrième étude visait poursuivre le processus de simplification pour atteindre notre objectif d’appliquer directement au chien l’avancement de la tubérosité tibiale tel que réalisé chez l’homme. Après une étude monotonique de plusieurs matériaux (cage en titane Kyon, bloc de mousse de titane et bloc d’os synthétique biphasique de différentes porosités), ceux présentant une résistance compatible avec les forces rencontrées in vivo ont été soumis à une étude cyclique afin d’évaluer leur capacité à rester dans le trait d’ostéotomie sans aucun autre moyen de fixation que la friction avec l’os. Le bloc de mousse de titane et le bloc d’os synthétique de porosité 60% ont ainsi été testés cycliquement. Durant le test, aucun des implants n’a migré, prouvant ainsi que la friction était suffisante pour maintenir l’implant dans l’ostéotomie. De plus, l’os synthétique s’est révélé capable de résister aux 200 000 cycles permettant ainsi d’envisager, enfin, la réalisation d’une MMT aussi simplement que l’avancement de la tubérosité tibiale décrite chez l’homme. Nos travaux intensifs sur la technique d’avancement de la tubérosité tibiale nous ont conduit à observer une sous-estimation de l’avancement nécessaire préconisé jusque-là. Bien que cela n’ait jamais été mentionné dans la littérature, la prise en compte de cette sous-estimation est indispensable à la réalisation correcte de la chirurgie. Après avoir étudié, dans un premier papier, la variabilité intra- et inter-opérateur de la mesure de l’angle entre le tendon patellaire et le plateau tibial (PTA), et donc indirectement de celle de l’avancement, une deuxième étude a porté sur la quantification de cette sous-estimation et la proposition d’abaques destinés à la corriger. [less ▲]

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See detailProbabilistic Models of Visual Appearance For Object Identity, Class, and Pose Inference
Teney, Damien ULg

Doctoral thesis (2013)

The topic of object recognition is a central challenge of computer vision. In addition to being studied as a scientific problem in its own right, it also counts many direct practical applications. We ... [more ▼]

The topic of object recognition is a central challenge of computer vision. In addition to being studied as a scientific problem in its own right, it also counts many direct practical applications. We specifically consider robotic applications involving the manipulation, and grasping of everyday objects, in the typical situations that would be encountered by personal service robots. Visual object recognition, in the large sense, is then paramount to provide a robot the sensing capabilities for scene understanding, the localization of objects of interests and the planning of actions such as the grasping of such objects. This thesis presents a number of methods that tackle the related tasks of object detection, localization, recognition, and pose estimation in 2D images, of both specific objects and of object categories. We aim at providing techniques that are the most generally applicable, by considering those different tasks as different sides of a same problem, and by not focusing on a specific type of image information or image features. We first address the use of 3D models of objects for continuous pose estimation. We represent an object by a constellation of points, corresponding to potentially observable features, which serve to define a continuous probability distribution of such features in 3D. This distribution can be projected onto the image plane, and the task of pose estimation is then to maximize its “match” with the test image. Applied to the use of edge segments as observable features, the method is capable of localizing and estimating the pose of non-textured objects, while the probabilistic formulation offers an elegant way of dealing with uncertainty in the definition of the models, which can be learned from observations — as opposed to being available as hand-made CAD models. We also propose a method, framed in a similar probabilistic formulation, in order to obtain, or reconstruct such 3D models, using multiple calibrated views of the object of interest. A larger part of this thesis is then interested in exemplar-based recognition methods, using directly 2D example images for training, without any explicit 3D information. The appearance of objects is also defined as probability distributions of observable features, defined in a nonparametric manner through kernel density estimation, using image features from multiple training examples as supporting particles. The task of object localization is cast as the cross-correlation of distributions of features of the model and of the test image, which we efficiently solve through a voting-based algorithm. We then propose several techniques to perform continuous pose estimation, yielding a precision well beyond a mere classification among the discrete, trained viewpoints. One of the proposed method in this regard consists in a generative model of appearance, capable of interpolating the appearance of learned objects (or object categories), which then allows optimizing explicitly for the pose of the object in the test image. Our model of appearance, initially defined in general terms, is applied to the use of edge segments and of intensity gradients as image features. We are particularly interested in the use of gradients extracted at a coarse scale, and defined densely across images, as they can effectively represent shape as they capture the shading onto smooth non-textured surfaces. This allows handling some cases, common in robotic applications, of objects of primitive shapes with little texture and few discriminative details, which are challenging to recognize with most existing methods. The proposed contributions, which all integrate seamlessly in a same coherent framework, proved successful on a number of tasks and datasets. Most interestingly, we obtain performance on well-studied tasks of localization in clutter and pose estimation, well above baseline methods, often on par with or superior to state-of-the-art method individually designed for each of those specific tasks, whereas the proposed framework is similarly applied to a wide range of problems. [less ▲]

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See detailEtude ab-initio d’oxydes antiferroélectriques de structure pérovskite
Amisi, Safari ULg

Doctoral thesis (2013)

In this thesis we present an original ab-initio study of the evolution of antiferrodistortive (AFD), anti-polar electric (APE), and ferroelectric (FE) instabilities in various ABO3 oxides of perovskite ... [more ▼]

In this thesis we present an original ab-initio study of the evolution of antiferrodistortive (AFD), anti-polar electric (APE), and ferroelectric (FE) instabilities in various ABO3 oxides of perovskite structure, as well as their structural and dynamic properties. The main goal is to understand better the microscopic origin of the antiferroelectricity exhibited in these compounds. Three prototypical compounds are studied in detail : PbZrO3 , NaNbO3 , and SrZrO3. After a general introduction on ABO3 compounds, and the ab-initio techniques, we review the concept of antiferroelectricity in perovskites, highlighting some ambiguities in the usual definition and the necessity of turning to what we call a modern definition of antiferroelectricity. First, we highlight that it is the rigidity of the oxygen cage that tends to favor the FE distortion compared to the APE instability. Although illustrated on BaTiO3 , this argument is general, and confirmed by the inspection of the phonons dispersion curves of the ABO3 compounds in whom the strongest instability of the FE/APE branch is systematically at Γ. We show that the emergence of a stable or meta-stable APE distortion appear naturally through a coupling with other instabilities. The presence of AFD modes turns out to be a concrete way to create mixed FE/AFD and APE/AFD phases, crucial for the emergence of antiferroelectricity (AFE). This clarifies why the known AFE compounds systematically include AFD distortions. In this context, since the FE, APE and AFD instabilities are usually in competition, the coexistence of FE, APE and AFD instabilities of strong amplitudes seems required to create mixed phases combining them. This establishes the context convenient to the development of FE and AFE metastable phases close in energy. Another important element concerns the need of a first order AFE-FE transition under electric field producing a double hysteresis loop, typical of AFE compounds. Here also the AFD modes could play a key-role by allowing the emergence of FE/AFD and APE/AFD phases close in energy and developing distinct tilt patterns. These various elements give a new perspective on AFE and allow us to have a more precise idea of the origin of the AFE behavior in perovskites. We identify some key intrinsic characteristics allowing the prediction of materials with the propensity of developing an AFE behavior. [less ▲]

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See detailVALORISATION INDUSTRIELLE ET ARTISANALE DES ARGILES DU MAROC
El Ouahabi, Meriam ULg

Doctoral thesis (2013)

Dans une perspective de développement local durable, la présente étude est focalisée sur la caractérisation des matériaux argileux du Nord du Maroc en vue de leur valorisation dans le secteur de la ... [more ▼]

Dans une perspective de développement local durable, la présente étude est focalisée sur la caractérisation des matériaux argileux du Nord du Maroc en vue de leur valorisation dans le secteur de la céramique. Elle a l’avantage de contribuer à la promotion des matériaux locaux de construction tout en améliorant la qualité des céramiques artisanales produites. Les sédiments utilisés dans cette étude proviennent de la région du nord du Maroc (Tétouan, Tanger et Meknès), ainsi que de sites argileux utilisés à l’échelle nationale dans la fabrication de la céramique traditionnelle, à savoir les sites de Fès, Salé et Safi. Dans le cadre de ce travail, nous avons procédé à une caractérisation minéralogique, granulométrique, texturale, physique, chimique, thermique et technologiques de ces argiles afin d’évaluer leurs potentialités en industrie céramique. Les argiles de Tétouan et Tanger sont caractérisées par des assemblages minéralogiques diversifiés (en particulier une proportion variable d'argile, de quartz et de calcite). En particulier, les argiles de Meknès, Fès, Salé et Safi présentent une forte teneur en argile, en quartz et en calcite. La fraction argileuse des échantillons de Tétouan et Tanger est dominée par l'illite et la kaolinite avec des proportions variables de chlorite. Ces trois types de minéraux argileux sont responsables en grande partie des propriétés céramiques favorables des échantillons d’argiles étudiées. Les matériaux argileux étudiés sont généralement constitués de fines particules d'argiles avec une plasticité moyenne à forte et une faible teneur en matière organique. Ces échantillons sont composés essentiellement de SiO2 (35 - 60 %), Al2O3 (7 - 30 %) et Fe2O3 (10 - 22 %). La quantité de CaO dans les argiles de Tanger et Meknès est très variable (0 - 30 %). Le CaO n’est présent que dans certaines argiles de Tétouan. Le taux de Fe2O3 est variable allant de 0 à 22 %. Les autres oxydes représentent de faibles proportions (< 6 %). La capacité d’échange cationique et la surface spécifique de tous les échantillons sont faibles. La masse volumique apparente, le volume poreux et le nombre de micropores sont peu variables pour toutes les argiles. Les argiles de Tétouan et de Meknès montrent globalement un bon comportement au séchage, à l’exception de quelques échantillons qui montrent des fissures superficielles au séchage due à la présence des argiles gonflantes (smectite et vermiculite). Les argiles de Tétouan et de Meknès constituent des ressources minérales industrielles de bonne qualité pour la fabrication des produits variés dont des carreaux de sol, des briques et les tuiles. Afin d’avoir de bon produit fini, ces argiles doivent êtres cuites à des températures supérieur à 1050 °C. Les argiles de Tanger montrent des propriétés conformes avec les critères de production des briques. Néanmoins, la présence de sulfates en faible quantité dans quelques échantillons carbonatés conduit après cuisson à 1000 °C à la formation de nodules blancs de sulfate de calcium (CaSO4) à la surface de la brique, résultant de la réaction de sulfates avec le CaO. Néanmoins, quelques produits cuits ont présenté un retrait à la cuisson supérieur à 10% pour de températures allant de 1100 à 1150°C et une perte en poids à la cuisson supérieur à 10%. Pour une bonne rentabilité industrielle, ces retraits peuvent être minimisés par l’ajout d’une quantité optimale de dégraissant ou en faisant des mélanges et/ ou des formulations avec d’autres argiles proche géographiquement afin d’obtenir un mélange adéquat. [less ▲]

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See detailSmart drug delivery systems based on specifically-designed macromolecules and inorganic colloids
Liu, Ji ULg

Doctoral thesis (2013)

In the past few decades, various hybrid nano-vehicles have been developed as new drug delivery systems (DDS), in which inorganic and organic components are integrated within a nano-object. An ideal DDS ... [more ▼]

In the past few decades, various hybrid nano-vehicles have been developed as new drug delivery systems (DDS), in which inorganic and organic components are integrated within a nano-object. An ideal DDS should satisfy the conflicting requirements for high stability in extracellular fluid, so that it maintains its integrity during the in vivo circulation; however, it becomes labile upon the activation of internal or external stimuli after targeting to the disease sites, allowing the triggered release of therapeutic agents. The aim of this thesis was to build different hybrid nano-vehicles, explore the possibility to manipulate the release behaviors and evaluate their potential biomedical application. The first part presents an original work on reversibly-crosslinked nanogels based on poly(vinyl alcohol)-b-poly (Nvinylcaprolactam) copolymers. The second part is devoted to stimuli-responsive hybrid nanovehicles, composed of inorganic cores, e.g. maghemite nanoparticles or gold nanorods, and a stimuli-responsive polymer corona, e.g. poly(vinyl alcohol)-b-poly(acrylic acid) or poly(ethyl glycol)-b-poly(N-vinylcaprolactam). The third part focuses on core-shell nanoparticles made of a maghemite core and a mesoporous silica shell, while phase-changed molecules, e.g. 1-tetradecanol with melting temperature of 39 °C, were introduced as gatekeepers to regulate the release behaviors. These different nanostructures were developed as DDS to accommodate cargo molecules, and the triggered cargo release upon variation in pH or temperature, activation of reductive agent or presence of glucose was explored. Moreover, remote stimuli, e.g. alternating magnetic field or near infrared light, were also applied to trigger the release. Studies on cytotoxicity, cellular uptake and in vitro triggered release with cell culture are also described. [less ▲]

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See detailEcologie, dynamique des populations et intérêts économiques du noisetier d'Afrique (Coula edulis Baill.) au Gabon
Moupela, Christian ULg

Doctoral thesis (2013)

Le noisetier d’Afrique (Coula edulis Baill. Olacaceae) est une espèce à usages multiples des forêts denses humides africaines. Elle produit des graines d’une grande valeur nutritive qui sont régulièrement ... [more ▼]

Le noisetier d’Afrique (Coula edulis Baill. Olacaceae) est une espèce à usages multiples des forêts denses humides africaines. Elle produit des graines d’une grande valeur nutritive qui sont régulièrement collectées et commercialisées par les populations locales. Cependant, la valorisation et la domestication de ce produit forestier non ligneux (PFNL) est entravée faute de connaissances précises sur ses caractères reproductifs, son potentiel de production, ses mécanismes de régénération, et les perspectives de développement d'un marché commercial local pour ce produit. Une étude dédiée à cette espèce a donc été entreprise. L’objectif visé était d’améliorer les connaissances sur cette espèce afin de promouvoir sa place dans les systèmes agroforestiers et fournir des informations permettant d'assurer la conservation in situ de la ressource. Les résultats de l'étude montrent que C. edulis est utilisé selon une stratégie de subsistance par les populations, avant tout pour leur autoconsommation et éventuellement pour un revenu qui reste marginal. La reproduction de l'espèce est annuelle, garantissant une disponibilité régulière des fruits. Le diamètre minimum de floraison est de 10,6 cm tandis que le diamètre de fructification régulière est de 23 cm. L’accroissement annuel moyen de l’espèce est de 0,22 cm/an, une valeur similaire à celles observées chez d'autres arbres du sous-bois. La production fruitière est fortement liée au diamètre des tiges et varie d’une année à l’autre. En forêt naturelle, la dissémination de l'espèce est potentiellement assurée par sept espèces frugivores, le principal étant le potamochère, Potamochoerus porcus. Des rongeurs fouisseurs pourraient également jouer un rôle non négligeable dans la dispersion de C. edulis. Par contre, l'éléphant qui était soupçonné de contribuer significativement à la dispersion de l'espèce s'avère n'être qu'un disperseur anecdotique, voire nul. En matière de domestication, les stratégies ne devront pas être basées sur le semis, la germination de C. edulis étant très lente et échelonnée sur plusieurs années, avec des taux de levée très faibles. En revanche, le marcottage aérien a été un succès relatif sur cette espèce et présente l'avantage de maintenir le potentiel génétique de l'arbre multiplié. Les implications de ces résultats aussi bien en termes de gestion durable des peuplements naturels que de domestication de l'espèce dans un contexte agroforestier sont détaillés dans le document. Si l’on désire que les PFNL d’intérêt local comme C. edulis participent substantiellement au développement en milieu rural gabonais, il est essentiel d’orienter ces ressources à la fois dans une stratégie de gestion durable par leur domestication et leur intégration dans le cycle agricole et dans une stratégie de revenu supplémentaire où l’exploitation répond à une demande marchande. [less ▲]

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See detailCONTRIBUTION A LA CARTOGRAPHIE, PAR ETUDES DE LIAISON ET D’ASSOCIATION, DE LOCI D’INTERET CHEZ LES ANIMAUX DOMESTIQUES.
Zhang, Zhiyan ULg

Doctoral thesis (2013)

Until recently, breeding values were estimated based on phenotypes measured on the individual and its relatives, and the notion that the covariance between breeding values is proportionate to the kinship ... [more ▼]

Until recently, breeding values were estimated based on phenotypes measured on the individual and its relatives, and the notion that the covariance between breeding values is proportionate to the kinship coefficient. Advances in genomics now allow for direct analysis of the genome and identification of the loci that determine the breeding values of individuals. As a consequence, marker assisted selection and genomic selection have become more effective and are replacing conventional selection. The identification of loci influencing the traits of interest requires the use of advanced statistical methods that are constantly evolving. In the context of this thesis, we have (i) contributed to the development of gene mapping methods, (ii) applied these methods to map loci influencing both metric and meristic traits, and (iii) contributed to the development of methods for the integration of genomic information in livestock breeding and management. The mapping methods that we have helped developing distinguish themselves mainly by the fact that (i) they exploit haplotype information (by means of a hidden markov model) which should increase the linkage disequilibrium with causative variants and hence detection power, (ii) they can simultaneously extract linkage information within families, and linkage disequilibrium information across the population, and (iii) they correct for population stratification by means of a random polygenic effect, and (iv) they can be applied to binary as well as quantitative traits. We have applied these and other methods to map loci influencing (i) quantitative hematological parameters in a porcine line-cross, and (ii) binary traits including diseases in bovine and non-syntenic Copy Number Variants in cattle, horse and human. In fine, we have contributed to the development of methods for the utilization of marker information in animal selection and production. We have extended the haplotype-based mapping method to allow imputation and have evaluated the utility of this approach in scenarios mimicking reality. We have also contributed to the development of a method to quantify somatic cell counts in the milk of individual cows by genotyping a sample of milk from the farm’s tank (hence a mixture of milk from all cows on the farm) Our work has resulted in the development of a software package (“GLASCOW”) that is increasingly used by the community to map genes influencing complex traits, primarily binary. By using this tool, we have contributed to the localization of several trait loci in pig, cattle, horse and human. We have contributed to the development of approaches that reduce the costs of genomic analyses in livestock by, on the one hand, complementing real SNP genotypes with genotypes obtained in silico by means imputation, and, on the other hand, by developing a method to deconvolute genotypes obtained on DNA pools. [less ▲]

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See detailA walk into random forests: adaptation and application to Genome-Wide Association Studies
Botta, Vincent ULg

Doctoral thesis (2013)

Understanding underlying mechanisms of common diseases is one of the major goals of current research in medicine. As most of these disorders are linked to genetic factors, identification of the associated ... [more ▼]

Understanding underlying mechanisms of common diseases is one of the major goals of current research in medicine. As most of these disorders are linked to genetic factors, identification of the associated variants forms an excellent strategy towards the elucidation of molecular and cellular dysfunctions, and in fine could lead to better personalised diagnostics and treatments. Genome-Wide Association Studies (GWAS) aim to discover variants spread over the genome that could lead, in isolation or in combination, to a particular trait or an unfortunate phenotype such as a disease. The basic idea behind these studies is to statistically analyse the genetic differences between groups of healthy (controls) and diseased (cases) individuals. Advances in genetic marker technology indeed allow for dense genotyping of hundreds of thousands of Single Nucleotide Polymorphisms (SNPs) per individual. This allows to characterise representative samples composed of several hundreds to several thousands of cases and controls, each one characterised by up to a million of genetic markers sampling the genomic variations among these individuals. The standard approach to genome wide association studies is based on univariate hypothesis tests. In this approach each genetic marker is analysed in isolation from the others, in order to assess its potential association with the studied phenotype, in practice by the computation of so-called p-values based on some statistical assumptions about the data-generation mechanism. Because of the very high ratio between the large number of SNPs genotyped and the limited number of individuals, multiple-testing corrections need to be applied when carrying out these analyses, leading to reduced statistical power. While this standard approach has been at the basis of many novel loci unravelled in the last years for several complex diseases, it has several intrinsic limitations. A first limitation is that this approach does not directly account for correlations among the explanatory variables. A second intrinsic limitation of GWAS is that they can't account for genetic interactions, i.e. causal effects that are only observed when specific combinations of mutations and/or non-mutations are present at the same time. The third limitation of univariate approaches is that they do not directly allow to assess the genetic risk, since many of the identified markers (with similarly small p-values) actually account for the same underlying causal factor: exploiting their information to predict the genetic risk is hence far from straightforward. Within bioinformatics, machine learning has actually become one of the major potential sources of progress. As a matter of fact, biology has become nowadays one of the main drivers of research in machine learning, and is by itself already a very competitive research field. Among the subfields of machine learning, supervised learning and its extensions such as semi-supervised learning, stand out as the most mature and at the same time most rapidly evolving area of research. Within this context, the purpose of this thesis was to study the application of random forest types of methods to genome wide association studies, with the twofold goal of (i) inferring predictive models able to asses disease risk and (ii) to identify causal mutations explaining the phenotype. The choice of this family of methods was originally motivated by the fact that these methods are a priori well suited for that kind of analysis due to some of their interesting properties. They are indeed able to deal efficiently with very large amounts of data without relying on strong assumptions about the underlying mechanisms linking genetic and environmental factors to phenotypes, and they can also provide interpretable information, in the form of scorings and/or rankings of SNPs so as to help in the identification of causal genetic loci. In the first part of this manuscript, we analyse the state-of-the art in the application field of genome wide association studies and in supervised machine learning, and subsequently describe in details the three tree-based ensemble methods that we have implemented and applied in our research; in Part II, we report our empirical investigations, in three successive steps, namely i.) a preliminary study on simulated datasets yielding controlled conditions with known ground-truth and allowing for a first sanity check of the T-Trees methods, in ideal conditions; ii.) a detailed study on a given real-life dataset concerning Crohn's disease, where we try to understand the main features of the three different algorithms in terms of predictive accuracy and capability of identification of relevant genetic information, and their sensitivity with respect to various kinds of quality control procedures and algorithmic parameters; iii.) a systematic replication study, where we confirm, on 7 different datasets from the Wellcome Trust Case Control Consortium, the main outcomes of our study on the Crohn's disease, while using default parameter settings. 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See detailLarge scale phylogenetic patterns of diversification in Bryophytes
Laenen, Benjamin ULg

Doctoral thesis (2013)

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See detailVers une gestion rationnelle de l'eau dans une situation complexe d'urbanisation anarchique dans un pays en développement : cas du bassin versant de l'Abiergué (Yaoundé-Cameroun)
Kouam Kenmogne, Guy Romain ULg

Doctoral thesis (2013)

This study focuses on an analysis of water resource management in cities of developing countries with very rapid rates of urbanization. The objectives are twofold: firstly, to highlight the factors which ... [more ▼]

This study focuses on an analysis of water resource management in cities of developing countries with very rapid rates of urbanization. The objectives are twofold: firstly, to highlight the factors which caused and which govern poor water resources management these cities and secondly to develop a coherent sustainable urban water resources management strategy. The study was conducted in the Abiergue watershed in Yaoundé-Cameroon. The methodology used is based on holistic and participative approaches resulting from the combination of principles of "Integrated Water Resources Management-IWRM" and "Ecosystem and Human Health-ECOHEALTH". Political, economic, social, environmental, historical and mesological factors have resulted in a water resources management system marked by many inadequacies and constraints. Poor access to drinking water and sanitation, recurrent flooding, endemic waterborne diseases, water pollution etc are all permanent pressures that contribute to the impoverishment of households and hamper the development of the area in particular and that of the town of Yaoundé in general. The poor water resources management in the Abiergué watershed is an indicator of an urban governance crisis. Three scenarios to improve this situation were developed: maintaining the status quo; destruction of buildings and a scenario based on IWRM and ECOHEALTH. The optimal strategy integrates principles from IWRM and ECOHEALTH with the base scenario 3.4 focused on actors. Using a sequential process, it takes into account actions on water resources, health and reforms on the legislative, regulatory and institutional framework. Many constraints like land tenure, corruption, limited financial resources and poor urban governance may undermine the implementation of this strategy despite the potential of the watershed. All indicators suggest that water resources management in the Abiergue watershed is poor. There is therefore an urgency to implement this strategy within the framework of the ongoing IWRM process in Cameroon. "Time for Solutions", the theme of the 6th World Water Forum held in Marseille in 2012 is fully translated into action through this study. [less ▲]

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See detailL’Arganeraie des Haha : droits réels, inégalités d’accès aux ressources naturelles et principales dynamiques (Sud Ouest du Maroc)
Bejbouji, Jihane ULg

Doctoral thesis (2013)

Véritable spécificité du Sud-Ouest marocain, l’arganeraie est l’ensemble des écosystèmes dont l’espèce caractéristique est l’arganier, relique de la végétation subtropicale de l’ère tertiaire. Outre son ... [more ▼]

Véritable spécificité du Sud-Ouest marocain, l’arganeraie est l’ensemble des écosystèmes dont l’espèce caractéristique est l’arganier, relique de la végétation subtropicale de l’ère tertiaire. Outre son originalité historique et géographique, l’arganeraie assure de multiples fonctions écologiques et procure de nombreux biens à une population pauvre et vivant dans des conditions précaires. Toutefois, cet espace intrigue. Alors que dans les autres forêts marocaines, les riverains ne disposent que de deux droits (la récolte de bois mort gisant et le parcours), la population de l’arganeraie bénéficie depuis 1925 d’une législation spéciale lui assurant une large gamme d’utilisations et d’exploitations des ressources forestières. Cette thèse, menée dans l’arganeraie des Haha (province d’Essaouira) se propose de contribuer à la gestion durable d’un territoire partagé dans un contexte caractérisé par de nombreuses mutations. Pour appréhender les évolutions de cet éco-socio-système, nous avons privilégié une entrée par l’étude des droits réels, d’accès et d’usage, en accordant une attention particulière aux inégalités qui les caractérisent. Nous nous sommes fixé trois objectifs : identifier les modes de gestion, analyser les dynamiques actuelles des usages et pratiques dans ces écosystèmes à arganier et proposer des scénarios de gestion. Pour ce faire, nous avons mené une enquête qualitative et quantitative auprès de 100 ménages au niveau de trois communes rurales, Smimou, Ida ou Azza et Imgrade, situées autour du massif du Jbel Amsitten, l’une des zones centrales de la Réserve de Biosphère de l’arganier. Notre travail de recherche a d’abord dressé le portrait actuel de l’espace et de l’ensemble des droits qui le régissent. Il montre que leur appropriation s’est faite progressivement par une population en majorité issue d’un brassage récent d’émigrants provenant du sud. Il en résulte une trame de droits récemment forgée et très diversifiée. Ensuite, en partant des représentations que se font les populations de leur patrimoine, nous avons identifié trois grands types de propriétaires se comportant selon des logiques différentes : d’abord des ménages, qui sont les plus nombreux, dont les ressources sont rares ou limitées et qui cherchent avant tout à survivre. Ensuite des ménages dont les ressources sont modérées et qui développent une logique de gestionnaire et finalement, quelques ménages dont les ressources sont importantes et qui poursuivent une logique d’entrepreneur. Par ailleurs, l’étude du compartiment agdal, son concept, ses configurations sociales et spatiales et ses types de gestion a montré l’évolution d’une pratique de mise en défens à celle d’un terroir se révélant comme un agrégat de droits. Et contrairement à ce qu’on croit, la détention de l’agdal ne concerne pas toute la population, mais elle semble plutôt liée à la disponibilité des ressources aux différentes périodes d’arrivée des ménages immigrants. Quant à sa gestion, deux types ont été identifiés : individuel et commun. En ayant recours à une étude monographique, nous avons alors montré que la gestion de cet espace-ressources est complexe. Elle résulte à la fois de l’histoire de l’appropriation des droits, de la délimitation forestière et des stratégies de gestion intergénérationnelle individuelles et collectives adoptées par la population pour mettre en valeur ces ressources. Enfin, moyennant la systémique, nous avons identifié quatre principales dynamiques qui traversent ce système : une dynamique de déprise, de maintien/résistance, de marché et de projet. Ce travail de recherche a mis en lumière le fait que l’arganeraie n’est pas un tout, approprié par un groupe homogène, mais qu’elle renvoie plutôt à un ensemble d’éléments en osmose : une population diversifiée, des patrimoines inégaux et des rapports au territoire variés. Par ailleurs, les formes de gestion en commun dans cet espace déclinent tandis que la tendance à la gestion privée se renforce. La prise en compte de cette complexité, des inégalités d’accès aux ressources naturelles, des stratégies anticipatives adoptées par la population et de la diversité des compartiments et des pratiques, s’avère nécessaire pour la réussite de tout projet d’aménagement, mais aussi pour la durabilité de l’approvisionnement en fruits. C’est ainsi que nous avons construit trois scénarios de gestion qui sont, à notre avis, les plus plausibles : un scénario tendanciel ou de statu quo, un scénario optimiste ou de gestion partagée entre l’Etat et les communautés et un scénario modéré ou de gestion privée. La gestion patrimoniale et intégrée de l’arganeraie serait en mesure de contribuer à sa gestion durable. Renouer avec le corpus de règles qu’entretenait la population avec cet espace-ressources peut être, à notre avis, une des principales portes d’entrée de sa conservation. [less ▲]

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See detailUse of Bacillus subtilis starter cultures during red sorghum malting
Bwanganga Tawaba, Jean-Claude ULg

Doctoral thesis (2013)

Bacillus subtilis was used to inhibit mould growth during red sorghum malting. Improved conditions for achieving good malt properties were studied and mathematical models are proposed for the induction ... [more ▼]

Bacillus subtilis was used to inhibit mould growth during red sorghum malting. Improved conditions for achieving good malt properties were studied and mathematical models are proposed for the induction and the repression phases of α- and β-amylase synthesis. The problems associated with the hydrolysis of β-glucans and the biocontrol steeping effect on β-glucanase activities are discussed. The effect of the biocontrol treatment and that of phytohormones produced by the bacterial strain used on the synthesis of specific red sorghum enzymes are elucidated. Gibberellic acid and abscisic acid diffusion and cross-talk as factors affecting the synthesis of red sorghum malt α- and β-amylase activities are also discussed. The production of 3-indole acetic acid (IAA) by B. subtilis S499 was also a focus in this study and the determination of the conditions for improving the production of indole-3-acetic acid are determined. [less ▲]

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See detailEffet de l'effort, l'entrainement et l'inflammation sur l'immunité innée des voies respiratoires profondes du Trotteur Français
Waldschmidt, Ingrid ULg

Doctoral thesis (2013)

Ce manuscrit rapporte dans un premier temps, l'élaboration du protocole expérimental de stimulation des TLR des macrophages alvéolaires équins ex vivo. Dans un second temps, l'effet de l'exercice et l ... [more ▼]

Ce manuscrit rapporte dans un premier temps, l'élaboration du protocole expérimental de stimulation des TLR des macrophages alvéolaires équins ex vivo. Dans un second temps, l'effet de l'exercice et l'entrainement sur la réponse des macrophages alvéolaires équins en conditions standardisées d'entrainement. Enfin, dans un troisième temps, l'impact de l'inflammation pulmonaire sur la réponse des macrophages alvéolaires ex vivo de chevaux de course atteints d'IAD, en conditions de terrain. [less ▲]

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See detailAnalyse critique de l'économie politique de l'utilisation des ''enfants-soldats''. Etude de cas des pays du fleuve Mano (Liebria, Sierra Léone, Côte d'Ivoire)
Zina, Seydina Ousmane ULg

Doctoral thesis (2013)

Notre thèse a consisté à construire analytiquement le cadre de pensée de la rationalité économique et à le discuter au regard de la littérature et des cas des pays du fleuve Mano (Libéria, Sierra Léone ... [more ▼]

Notre thèse a consisté à construire analytiquement le cadre de pensée de la rationalité économique et à le discuter au regard de la littérature et des cas des pays du fleuve Mano (Libéria, Sierra Léone, Côte d’Ivoire). Et elle a retenu que les variables de l’approche économique (nombre élevé de jeunes, faible niveau d’éducation, faible revenu et pillage des ressources naturelles) sont contrairement à leur fonction utilitariste, des répertoires d’action mobilisés par les jeunes et les groupes armés dans le cadre du ‘’marché de la violence’’. Cette approche de la violence remet le comportement économique du jeune au cœur des contextes socio-économiques, politiques et culturels du conflit armé, et limite l’hypothèse du choix rationnel. [less ▲]

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See detailDynamics of Agrarian Systems in Hai Duong Province, North Vietnam
Han Quang, Hanh ULg

Doctoral thesis (2013)

In Vietnam, the agrarian systems have evolved considerably during the socio-economic transformation period initiated in the late 1980s with the political reform (Doi Moi). In a region around the capital ... [more ▼]

In Vietnam, the agrarian systems have evolved considerably during the socio-economic transformation period initiated in the late 1980s with the political reform (Doi Moi). In a region around the capital, where the process of industrialization, urbanization, and international integration has been accelerating, a number of questions about the sustainability of agrarian systems are raising. By diagnosing and analysing the dynamics of agrarian systems from 1980 to 2010, this study aims to provide decision-makers with some sectorial and territorial policy options authorizing the sustainable development of agriculture and rural society in the new socio-economic context. Combining the historical, adaptive, and systematic approaches, this study shows that farmers in Hai Duong province adapted effectively to the socio-economic and institutional changes, notably by transforming part of the rice land areas into other agricultural land use purposes such as fish ponds, animal buildings, vegetable fields and fruit orchards. These rapid changes, however, do not go in the direction of improving the sustainability of agrarian systems. Farm holders are now facing with many technical and economic contradictions whereas land issues are not only related to the agricultural purposes. Competition functions in land use, fragmentation of plots, the imperfection of the land market and rising property values are all emerging. The prospects for sustainability of agrarian systems are analysed under different scenarios which highlight the complexity of policy options. The recommendations are made not only for the agricultural sector in general, but also for different agrarian systems in specific regions. [less ▲]

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See detailL'impact des politiques internationales de financement du développement sur les marges de manoeuvre politiques (policy space) des pays en développement. Une étude selon la grille d'analyse centre/périphérie
Zacharie, Arnaud ULg

Doctoral thesis (2013)

La thèse de ce travail est que dans le contexte du processus contemporain de globalisation, le système international du financement du développement a renforcé les contraintes de jure et de facto qui ... [more ▼]

La thèse de ce travail est que dans le contexte du processus contemporain de globalisation, le système international du financement du développement a renforcé les contraintes de jure et de facto qui pèsent sur l’autonomie des politiques économiques des pays en développement, mais qu’il offre également de nouvelles opportunités en transformant la géographie de la production mondiale et des flux économiques et financiers qui en découlent. Notre hypothèse est dès lors que l’impact des politiques internationales de financement du développement sur les marges de manœuvre politiques des pays en développement n’a pas été uniforme et que ce sont précisément les pays qui ont réussi à assurer un équilibre entre les contraintes du système international et leur autonomie politico-économique qui ont réussi à tirer profit de ce système et à entamer un processus de convergence économique avec les pays du centre. [less ▲]

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See detailSimulations numériques de la dynamique d’épidémies sur réseaux aléatoires selon une approche de physique statistique
Ababou, Malika ULg

Doctoral thesis (2013)

Dans le présent manuscrit, notre travail est focalisé dans un premier temps, sur l’étude de la dynamique de propagation des épidémies sur un modèle de réseaux complexes qui est une variante du modèle de ... [more ▼]

Dans le présent manuscrit, notre travail est focalisé dans un premier temps, sur l’étude de la dynamique de propagation des épidémies sur un modèle de réseaux complexes qui est une variante du modèle de Barabási-Albert (BA). Les simulations numériques révèlent une transition d’une loi exponentielle à une loi de puissance de la distribution du nombre de liens par nœud en fonction du paramètre de précision ω. Nous avons prouvé aussi que la synchronisation collective σ induite par le processus épidémiologique Susceptible-Infected-Recovered-Susceptible (SIRS ) dépend de la structure topologique du réseau. Dans un second temps, nous nous intéressons à l’étude numérique de ce modèle épidémique en introduisant une source permanente d’infection I_0, afin d’éviter la disparition de la maladie, sur un réseau exponentiel généré par le modèle (BA) d’attachement préférentiel à précision finie. Les simulations montrent que la valeur moyenne de la fraction des personnes infectées dépend de la période naturelle du cycle d’infection τ_0 et du temps d’infection τ_I . Un maximum de synchronisation des personnes infectées est atteint lorsque le rapport τ_I /τ_0 est légèrement plus petit que 1/2. Un autre résultat important est la dépendance linéaire de la valeur moyenne de la fraction d’éléments infectés ⟨n_inf ⟩ en fonction de τ_I /τ_0 bien que, la synchronisation est une fonction non triviale de τ_I /τ_0. [less ▲]

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See detailConstruction of an interactomic map of Ets factors and identification of new functions in mRNA processing
Rambout, Xavier ULg

Doctoral thesis (2013)

The family of Ets factors is one of the largest families of human transcription factors. This thesis aimed at molecularly and biologically defining these well known though not well-understood ... [more ▼]

The family of Ets factors is one of the largest families of human transcription factors. This thesis aimed at molecularly and biologically defining these well known though not well-understood transcription factors using a system biology approach. Combination of interactomic and bioinformatics tools gave rise to the first interactome of the human Ets factors built on more than 400 interactions with nearly 300 interaction partners. We fragmented our interactome in 24 functional highly intraconnected sub-networks (clusters, or CL) and highlighted a new role for Ets transcription factors in mRNA processing (CL1). Steady-state levels of mRNAs result from the balance between transcription and mRNA decay, two events sitting at both ends of the mRNA life. In the traditional and still prominent view, these events are spatially, functionally and temporally independent. Here, we showed that the Erg subfamily of Ets factors (composed of the three members ERG, FLI1, and FEV) regulate mRNA decay of specific targets via promoter-mediated mRNA imprinting with sequence-specific RNA-binding proteins (CL1) and the CCR4-NOT deadenylation complex. This constitutes the first evidence, regardless of the organism, that DNA-binding transcription factors recruit RNA-binding proteins and mRNA decay components to control the degradation of specific mRNAs. This is also the most detailed demonstration of a functional coupling between transcription and mRNA decay machineries in humans. We showed that ERG promoted mRNA decay of key mitotic regulators, among which the Aurora kinases Aurora A and B. Depletion of ERG prevented degradation of Aurora A and B mRNAs during mitosis, leading to aberrant levels of Aurora proteins, accumulation of centrosome and mitotic spindle defects, and ultimately mitosis blockage. This consists in a significant advance in understanding of mitosis progression that was until now thought to be exclusively regulated by post-translational modifications and proteasomal degradation of proteins. Our results show that, in the contrary of bulk mRNAs whose decay is inhibited during mitosis, degradation of specific transcripts is a prerequisite for normal mitosis progression. [less ▲]

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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 detailTartaglia, Zigzag et Flips : les particules denses à haut Reynolds
Darbois-Texier, Baptiste ULg

Doctoral thesis (2013)

This experimental work deals with sports balls trajectories. Those dense projectiles are laun- ched in air at several hundred kilometers per hour. In this situation, ball trajectories depend on the fluid ... [more ▼]

This experimental work deals with sports balls trajectories. Those dense projectiles are laun- ched in air at several hundred kilometers per hour. In this situation, ball trajectories depend on the fluid flow around them which occurs at high Reynolds number (Re > 1000). The first effect we consider is the fluid drag. This friction reduces the range and gives rise to trajectories very different from parabola which are non symmetric toward the top. This kind of trajectories occurs in badminton for high clears. Nicollo Tartaglia was the first to draw those curves observing the trajectories of cannon balls. However, the air doesn’t only limit the forward motion. When balls spin, the Robin-Magnus effect produces a lateral force and curves the trajectory. This is studied in the case of clearances in soccer. Lateral aerodynamic forces also exist when the ball has no spin. The turbulent behavior of the flow around a spherical particle provides lateral forces with complex temporal dependency. This induces zigzag trajectories which are occasionally observed in volley, soccer and baseball. We inspect the condition of occurrence of this phenomenon. Then, the case of non spherical balls are considered. Such balls are used in rugby, football and badminton. Shuttlecocks have the propriety to fly the nose ahead which oblige them to flip after each racket impact. Finally, we study the motion of a fluid particle with the particular case of a Leidenfrost liquid ring. A such object is created by approaching an annular magnet from a paramagnetic liquid oxygen drop. The closing dynamics of this non wetting ring is described with by the way of a potential flow approach. [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 detailMETHODOLOGIES FOR ESTIMATING REPEATABILITY AND REPRODUCIBILITY VARIANCES IN MULTIVARIATE DATABASES
Rozet, Eric ULg

Master's dissertation (2013)

Due to the huge amount of information available from spectra obtained from the analyses of biological samples using spectroscopic analytical techniques such as NMR or MIR/NIR multivariate analysis such as ... [more ▼]

Due to the huge amount of information available from spectra obtained from the analyses of biological samples using spectroscopic analytical techniques such as NMR or MIR/NIR multivariate analysis such as Principal Component Analysis (PCA) are required to understand the influence of major experimental factors. However, many experiments in these studies have more complexes variability structures than simply comparing several treatments: they may include time effects, biological effects such as diet or hormonal status, and other blocking factors or variability sources: samples stability, age of the individuals, pH of a buffer, days of acquisition, and so on. Analysis of these databases needs to extract from the spectral data matrix the variations linked to a change indicated in the factor of interest. However other sources of variability may impair this objective. This stresses the importance to discover the sources of variability of the spectral data using appropriate methodology. Classically, to analyze such data analysis of variance (ANOVA) or multivariate ANOVA (MANOVA) is used. However direct application of these methodologies to spectrum obtained from structured experimental studies is inappropriate or impossible. More complex data analyses methodologies are required to understand the importance of the various factors implied in the experiments and to provide a measure of their variance components. Three related methodologies have been proposed to achieve this: ANOVA simultaneous component analysis (ASCA), ANOVA-PCA (APCA) and AComDim. The ASCA and APCA methodologies combine first an analysis of variance step (ANOVA) and then a PCA step. The AComDim one adds to the output of the ANOVA-PCA step a multi-block analysis. In addition, an extension of MANOVA is also available called 50-50 MANOVA and Principal variance component analysis (PVCA) has also been proposed. In this work, the usefulness and applicability of these advanced techniques to data analysis of NMR metabolomic spectra and MIR spectra are given to highlight the increase of knowledge gained and the estimation of main sources of variability arising in an experimental setup. In addition another methodology is proposed which combines PCA and Multivariate linear mixed modeling (PCA-MLMM). [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 detailLa citadelle de Namur : patrimoine fortifié comme enjeu patrimonial de développement durable
Van Laere, Bertrand ULg

Master's dissertation (2013)

Quels sont les éléments clefs de conception entrant en compte lors de la restauration paysagère d’un ancien domaine fortifié au relief accidenté dans l’optique du développement durable ? Dans l’usage ... [more ▼]

Quels sont les éléments clefs de conception entrant en compte lors de la restauration paysagère d’un ancien domaine fortifié au relief accidenté dans l’optique du développement durable ? Dans l’usage actuel, le mot « citadelle » est souvent mal employé pour désigner des forteresses de diverses époques. Le terme émerge pendant la Renaissance italienne et s’exporte vite, comme le bastion. Étymologiquement, citadella veut dire « petite cité, en référence à la grande, face à laquelle elle s’implante. Il n’y a pas de citadelle sans ville, et, généralement, sans ville forte. Elle participe de son système défensif et prend place sur un point stratégique. La ville de Namur, née au confluent de la Sambre et de la Meuse occupe un paysage d’une grande beauté. La citadelle, l’une des plus vastes d’Europe en cours de restauration, située sur l’éperon rocher du confluent sambro-mosan est un ensemble monumental unique en Belgique ainsi qu’un élément essentiel du paysage namurois. «Les places créées par Vauban sont un jeu sur la protection et l’ouverture, sur le caché et le montré. C’est un acte urbain sur la relation au temps et à l’espace du paysage» Jean Nouvel d’après sa préface de «Vauban, l’intelligence du territoire» (2006). [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 detailFaiRebel, du lait au projet équitable. Analyse du réseau socio-technique d'une innovation pour une transition à deux échelles
Feyereisen, Marlène ULg

Master's dissertation (2013)

Étude de cas focalisant sur le label de lait équitable Fairebel qui s'inscrit dans le projet de Lait Equitable chapeauté par l'EMB (European Milk Board). Retrace le contexte, la création et l'évolution de ... [more ▼]

Étude de cas focalisant sur le label de lait équitable Fairebel qui s'inscrit dans le projet de Lait Equitable chapeauté par l'EMB (European Milk Board). Retrace le contexte, la création et l'évolution de ce label de lait depuis ses origines pendant la crise du lait de 2009 jusqu'à aujourd'hui (2013). L'histoire de ce lait démontre comment une innovation, vue comme étant un objet technique, devient un réseau socio-technique. L'étude met également en avant les verrous du système agro-alimentaire qui bloquent toute innovation et explique comment les incohérences d'une innovation peuvent aussi devenir sa force car elles permettent de lui donner sa réalité (concrétisation). [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 detailÉvaluation des effets de la formation et de la supervision de services d’aide aux familles qui accompagnent des personnes atteintes d’une maladie de type Alzheimer
Marquet, Manon ULg

Master's dissertation (2013)

Introduction : Des interventions peuvent réduire le risque que des aidants professionnels qui accompagnent des personnes âgées (atteintes ou non de démence) développent des attitudes âgistes, un sentiment ... [more ▼]

Introduction : Des interventions peuvent réduire le risque que des aidants professionnels qui accompagnent des personnes âgées (atteintes ou non de démence) développent des attitudes âgistes, un sentiment d’incompétence, une insatisfaction et un épuisement professionnels. Ces interventions sont néanmoins essentiellement destinées aux aidants en milieu institutionnel. Objectifs : (1) vérifier que des aidants professionnels à domicile avec un niveau d’études peu élevé présentent une vision négative du vieillissement et une méconnaissance de la maladie d’Alzheimer et qu’à cette vision conjuguée à cette méconnaissance sont liés un faible sentiment d’efficacité et une satisfaction professionnelle moindre et (2) évaluer, au niveau de ces différents paramètres, l’efficacité d’une intervention destinée à ces aidants. Méthodologie : 17 aides familiales ont bénéficié d’une intervention visant à améliorer leurs connaissances sur les démences et à les aider à mettre en place des stratégies de résolution de problèmes face aux difficultés rencontrées dans leur pratique, et ceci, afin de favoriser une vision moins stigmatisante de la maladie d’Alzheimer. Différents auto-questionnaires ont été complétés par les participantes avant et après l’intervention. Résultats : Indépendamment de leur faible niveau d’éducation, les aides familiales ont des attitudes plutôt positives envers le vieillissement et des connaissances satisfaisantes sur la maladie d’Alzheimer. Lorsque ces dernières augmentent, elles sont reliées à une satisfaction moindre vis-à-vis du contexte professionnel. La diminution des stéréotypes âgistes est quant à elle reliée à une diminution du sentiment de compétence. Quant à l’intervention, elle permet de diminuer l’âgisme des aides familiales, d’améliorer leurs connaissances sur la maladie d’Alzheimer, leur sentiment de compétence et leur satisfaction vis-à-vis de leurs tâches professionnelles. Conclusion : Les relations initialement prédites entre les variables ne sont pas toutes présentes et sont parfois contraires à nos prédictions, ce qui peut s’expliquer, en partie, par les questionnaires que nous avons employés. Quant à l’intervention, elle est efficace puisqu’elle atteint ses objectifs de départ. Ces résultats encouragent non seulement la formation des aidants professionnels à domicile mais aussi l’évaluation de l’efficacité des interventions proposées, à la fois auprès des aidants professionnels, informels et des personnes accompagnées. [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 detailPortfolio Professionnel : Itinéraire d'un technopédagogue
Van de Poël, Jean-François ULg

Master of advanced studies dissertation (2013)

Ce portfolio retrace mon parcours professionnel et illustre les compétences acquises au travers de mon développement en tant que conseiller techno-pédagogique et de formateur auprès des enseignants de l ... [more ▼]

Ce portfolio retrace mon parcours professionnel et illustre les compétences acquises au travers de mon développement en tant que conseiller techno-pédagogique et de formateur auprès des enseignants de l'Université de Liège [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 detailImplication de la sous-famille Erg des facteurs de transcription Ets dans la régulation de l'épissage chez l'Homme
Vincent, Côme ULg

Master's dissertation (2013)

The human family of Ets proteins and the Erg subfamily composed of 3 members (ERG, FLI1 and FEV) are known as transcription factors, involved in many cellular processes. On the other hand, most protein ... [more ▼]

The human family of Ets proteins and the Erg subfamily composed of 3 members (ERG, FLI1 and FEV) are known as transcription factors, involved in many cellular processes. On the other hand, most protein-coding genes contain intervening sequences (introns) that must be precisely removed from pre-mRNA through the process of pre-mRNA splicing. The first aim of this project was to molecularly characterise the link between these two actors. To achieve this goal, three different approaches were used. Firth, the link between the Erg subfamily and nuclear speckles, subnuclear structures that are enriched in pre-mRNA splicing factors, was studied using immunofluorescence and confocal microscopy, then an MS2-tethering assay was performed and finally, endogenous targets whose splicing would be dependent on this subfamily were identified. The results of these approaches highlighted interconnectivity between gene expression machineries. Moreover, such understanding of molecular basis of cancer-involved proteins provide new possibilities for earlier detection as well as better diagnosis, prevention and novel treatment strategies. [less ▲]

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See detailDetection of Staphylococcus aureus enterotoxins in meat using UPLC-MS/MS
Davin, Marie ULg

Master's dissertation (2013)

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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 detailImpact de la gestion des risques sur le processus budgétaire dans le cadre des contrats de construction et élaboration d'un outil d'aide à la prise de décision
Marville, Grégoire ULg

Master's dissertation (2013)

The Belgian construction sector was not spared by the 2008 financial crisis, and is still seriously affected by it. The market is currently characterized by a fall-off in activities, a pressure on prices ... [more ▼]

The Belgian construction sector was not spared by the 2008 financial crisis, and is still seriously affected by it. The market is currently characterized by a fall-off in activities, a pressure on prices and a significant number of bankruptcies. Consequently, companies have no other choice than engaging in harsh competition, even if it means diminishing drastically their profit margins in order to obtain some contracts. In such a context, companies must have at their disposal an efficient budgetary control in order to survive in such a risky sector as the construction one. The first objective of this work is to determine the way in which risk management can influence on budgetary control. For that purpose, the present state of knowledge of risk management and budgetary control is drawn up. The legislative and contractual influences on both these processes and the potential impact of public-private partnerships are analysed. The second objective of this work is to offer companies a tool enabling them to improve their budgetary control by means of an improved risk management. In order to be exploitable and valuable, such a tool must take into account the companies’ real needs and the weaknesses of their current processes. So as to identify these needs and weaknesses, the present state of the sector practices is drawn up by means of interviews carried out in 2013 among various companies of the sector. The gathered data are analysed on the basis of an analytical grid made up of criteria resulting from the present state of theoretical knowledge. The elaboration of the tool itself relies on theoretical knowledge and the present state of practices. This work shows that an efficient risk management ensures a better control of the costs of a project and a more accurate knowledge of the risk taken when agreeing to work for a given price. It offers a scalable decision-making tool, structured around nine phases, including: an adjustable technique of risk management meeting the theoretical recommendations as well as taking into account the companies’ real needs; and a budgetary control that comes along with risk management in order to better assess the costs and the risk-taking. [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 detailDeveloping a common Key performance indicators framework for biodiversity management in gypsum quarries throughout Europe for Eurogypsum
Pitz, Carline ULg

Master's dissertation (2013)

This study aims to establish a common Key Performance Indicators (KPIs) framework to report biodiversity for the Gypsum Industry at the European level. An original approach of participatory process has ... [more ▼]

This study aims to establish a common Key Performance Indicators (KPIs) framework to report biodiversity for the Gypsum Industry at the European level. An original approach of participatory process has been developed in order to integrate the different opinions and to reach a consensus framework between different stakeholders’ groups: - Eurogypsum stakeholders - European and local authorities - Scientific panel : universities and consulting offices - European and local associations for the conservation of nature - Stakeholders from the mining sector The strategy is based on five main steps: (i) To Build a stakeholders’ network; (ii) To build a framework proposal to be submitted to stakeholders by selecting a maximum set of indicators based on the literature and reaching an agreement on indicators with Eurogypsum (Focus Group); (iii) Reaching a consensus framework with all the stakeholders and evaluating feasibility by a Delphi Policy survey, by the analysis of the EIAs of the Gypsum Industry and by visiting three European quarries; (iv) Final validation with Eurogypsum (meeting); (v) Creating indicators’ Factsheets and a Eurogyspum report to the destination of the public. The resulting framework contains eleven indicators which are the most acceptable set of indicators for all the stakeholders. It answers to European legislation and strategies for biodiversity. It is intended to improve sustainability in the quarries and to help managing biodiversity, to allow setting up of appropriate reporting systems. The aim is to maintain the biodiversity status of the gypsum quarries. It is a flexible framework adaptable given the local context of each gypsum quarry in order to prove if a No Net Loss has been reached at a quarry’s scale. [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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