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See detailLa céramique tardo-républicaine en Italie centro-tyrrhénienne : établissement et confrontation des faciès du Latium septentrional et d'Etrurie méridionale entre le IIe s. et le Ier s. av. n.è.
Motta, Lucie ULiege

Doctoral thesis (2019)

La céramique n’est désormais plus à établir comme élément fondamental de nos connaissances des mondes anciens, que ce soit d’un point de vue chronologique, économique ou culturel puisqu’au-delà de son ... [more ▼]

La céramique n’est désormais plus à établir comme élément fondamental de nos connaissances des mondes anciens, que ce soit d’un point de vue chronologique, économique ou culturel puisqu’au-delà de son rôle d’élément datant auquel s’arrêtent encore bien trop d’études, elle est l’une des principales sources d’informations en étant un produit direct de la culture qui l’a produite. Sa quasi-omniprésence dans le mobilier archéologique et les fortes quantités excavées ne sont alors pas sans lien avec la solidité du matériau. En effet, bien que les objets ainsi réalisés soient aisément brisables, la matière constitutive – l’argile cuite – est particulièrement résistante et ne se détruit que difficilement, que ce soit par le sol et sa nature, le temps, l’action de l’homme ou la combinaison de ces divers facteurs. Elle n’est notamment pas recyclable comme peuvent l’être le verre ou les métaux, et encore moins périssable comme les matières organiques. Le choix d’orienter cette recherche sur l’Italie centro-tyrrhénienne tardo-républicaine n’est évidemment pas anodin et résulte de la constatation d’une lacune flagrante dans nos connaissances de sa céramique, bien qu’il s’agisse d’un ancrage, aussi bien chronologique que géographique, charnière de l’Histoire romaine. Ainsi, la ligne directrice de ce travail vise à constituer une première tentative de caractérisation du faciès céramique, aussi bien dans son uniformité que dans ses spécificités régionales et de déterminer son évolution interne, que ce soit en matière de classes, catégories, formes et types. Pour ce faire, une méthodologie rigoureuse a été mise en place afin de disposer d’un corpus composé d’éléments suffisamment similaires pour établir un raisonnement fiable. Trois axes ont notamment été au coeur de cette réflexion : - la nature des contextes afin d’écarter au maximum la notion de sélection des céramiques a priori, en excluant notamment les contextes cultuels. - la possibilité de disposer de l’intégralité du matériel céramique sans aucune sélection a posteriori, afin de pouvoir croiser les données de toutes les catégories et en tirer les conclusions au sujet des assemblages en eux-mêmes. - la quantification, dont l’usage reste relativement rare dans les études italiques, normalisée et appliquée à l’intégralité du matériel céramique afin d’envisager une nouvelle approche du domaine.L’étude a alors été centrée sur deux aires géographiques bien précises – le Latium septentrional et l’Étrurie méridionale – pour lesquelles il a fallu établir les faciès respectifs et leurs évolutions en s’interrogeant sur les rapports des classes, catégories, formes, types et provenances à travers trois ères chronologiques – la première moitié du IIe s., la seconde moitié du IIe s., et le Ier s. av. n.è. Des études macroscopiques ont également été réalisées sur les pâtes du matériel provenant des études de cas. Les groupes techniques mis en évidence ont alors été confrontés aux données déjà existantes afin de faire ressortir les zones d’approvisionnement, les questions d’échanges commerciaux, d’importations et de productions locales ou régionales. Plus modestement, cette étude a également tenté d’ouvrir le discours aux tendances et pratiques alimentaires en confrontant les résultats, notamment morphologiques et fonctionnels, obtenus lors de l’établissement du faciès avec les sources littéraires et les études déjà menées sur le sujet. Notons enfin que ce travail, loin d’être définitif, devra être nourri par d’autres recherches afin de s’étoffer pour confirmer ou infirmer les hypothèses proposées. [less ▲]

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See detailMolecular breeding and gene function verifying for cucumber fruit traits
Hu, Bowen ULiege

Doctoral thesis (2018)

Cucumber is a widely cultivated vegetable with high economic benefit. The assembled draft genome sequence and variation map generated by deep resequencing provided big data to advantage cucumber serving ... [more ▼]

Cucumber is a widely cultivated vegetable with high economic benefit. The assembled draft genome sequence and variation map generated by deep resequencing provided big data to advantage cucumber serving as the model plant for sex determination, long-distance trafficking and plant viruses disease research. However, the underlying molecular basis of some important horticultural traits, such as peel color, is still unknown. Besides, Cucurbitaceous species are well known to be one of the most refractory plants for transformation, which makes many meaningful traits hardly to be verified reliably in cucumber by reverse genetics, or makes identified gene cannot be applied well in molecular breeding. In this dissertation, the classical research methods of forward genetics and reward genetics was adopted. Initially, we discovered a cucumber mutant showing distinct light green exocarp of immature fruit from our EMS mutant library. By combining bulked-segregant analysis (BSA) and transient RNA interference, we first identified Csa7G051430 responsible for light green skin. Additionally, we successfully obtained transgenic cucumber using an inbred line rather than an F1 hybrid as previously used. We further optimized the CRISPR/Cas9 system by using stronger CsU6 promoter and a GFP tag to facilitate selection both the transformants and transgene-free mutants among the progeny. Thirdly, with these optimized procedures, we first verified the gene function of CsWIP1 which plays an important role in sex determination in cucumber and generated transgene-free gynoecious cucumber plants from a commercially valuable inbred line. The main contents and results are as follows: (1) An accumulation and replication of chloroplasts 5 gene mutation A mutant showing light green exocarp was discovered from ethylmethane sulfonate (EMS) mutagenized cucumber line 406 with dark green exocarp. Genetic analysis showed the mutant phenotype is conferred by a single recessive gene, here designated as lgp (light green peel). By re-sequencing of bulked segregants, we identified the candidate gene Csa7G051430 encoding ACCUMULATION AND REPLICATION OF CHLOROPLASTS 5 (ARC5) that plays a vital role in chloroplast division in Arabidopsis. A single nucleotide polymorphism (SNP) causing amino acid alteration in the conserved GTPase domain of Csa7G051430 showed co-segregation with the altered phenotype. Furthermore, a transient RNA interference of this gene resulted in reduced number and enlarged size of chloroplasts, which were also observed in the lgp mutant. These evidences support that the non-synonymous SNP in Csa7G051430 is the causative mutation for the light green peel. This study provides a new allele for cucumber breeding for light green fruits and additional resource for the study of chloroplast development. (2) Improving transformation protocol and optimizing CRISPR/Cas9 system in cucumber To find a way to improve the genetic transformation efficiency, GFP (green fluorescent protein) was used as a reporter during Agrobacterium infection and in situ hybridization of CsSTM was carried out. The result suggested the regenerated adventitious shoot was originate from cells in deeper layers where Agrobacterium can barely arrived by immerse infection. To enhance infection, a simple syringe was used for vacuum infiltration. Additionally, hemin was used to promote the rooting of transgenic shoots, which solved the problem that addition of auxin promoted chlorosis of the transgenic shoots. The transformation protocol established in this study was used to perform CRISPR/Cas9-mediated knocking out of three genes and the transformation efficiency approached 1.00‰. Aside from cucumber, the transgenic and genome-editing approach has been validated in melon, so it would be possible that this approach can be widely used in Cucurbitaceae species. (3) Engineering non-transgenic gynoecious cucumber using CRISPR/Cas9 system We verified the function of an important sex determination gene CsWIP1 and obtained transgene-free gynoecious cucumber by utilizing the improved efficient transformation protocol and optimized CRISPR/Cas9 system. Cswip1 T0 mutants displayed gynoecious phenotype, with the upper nodes bearing only female flowers, which indicated CsWIP1 acts as an inhibitor of carpel development in cucumber. Three types of deletions were found in T0 plant line 4 which displayed a high mutation rate 64.3% without off target. Homozygous and transgene-free Cswip1 T2 mutants were obtained from self-pollinating of heterozygous T1 mutants generated by crossing-pollinating between T0 and wild-type. Compared with monoecious wild-type plants, the Cswip1 mutants had seven times female flowers more than wild-type. Development of gynoecious cucumber by transgenic approach provide a stable and fast strategy to convert monoecious lines to gynoecious lines. [less ▲]

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See detailL'image exposée. La représentation des photographies de l'Agence France-Presse sur les réseaux sociaux numériques
Fabre, Maxime ULiege

Doctoral thesis (2018)

Le cliché d’une « barquette de frites nappées de chocolat », un « coucher de soleil » aux couleurs saturées près de Puerto Natales au Chili… Cette thèse a pour objectif d’étudier la représentation des ... [more ▼]

Le cliché d’une « barquette de frites nappées de chocolat », un « coucher de soleil » aux couleurs saturées près de Puerto Natales au Chili… Cette thèse a pour objectif d’étudier la représentation des photographies exposées par l’Agence France-Presse sur les « réseaux sociaux » – Instagram, Facebook, Twitter et Tumblr en têtes –, à l’aune d’une réflexion sur les transformations et les mutations des pratiques photojournalistiques en régime « numérique ». L’étude se divise en deux axes : une approche sémiotique d’abord, qui permet de comprendre de quelle manière le discours photojournalistique déploie les conditions formelles et médiatiques qui président à la fixation de la croyance, et articulent des normes et des attentes sur le statut de vérité du monde présenté par ces images ; une approche généalogique ensuite, qui étudie les conditions selon lesquelles les photographies de presse sont exposées. En réinterrogeant le concept de banalité, en lui redonnant son sens premier, ce deuxième axe développe une réflexion sur la complexité de la médiation « numérique », entre le pouvoir de réquisition des « industries du passage » d’un côté, et l’adaptation du discours informationnel de l’AFP de l’autre. À partir d’un point de vue nettement interdisciplinaire, la thèse prouve ici qu’il est possible de comprendre la médiation « numérique » comme la corrélation expressive entre l’économie d’un dispositif et le développement de formes de vies iconiques singulières. [less ▲]

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See detailMagnetocapillary Self-Assemblies: Interfacial Locomotion at Low Reynolds Number
Grosjean, Galien ULiege

Doctoral thesis (2018)

Les auto-assemblages magnétocapillaires se forment lorsque des particules ferromagnétiques douces sont déposées sur la surface d'un liquide et soumises à un champ d'induction. Ils émergent de la ... [more ▼]

Les auto-assemblages magnétocapillaires se forment lorsque des particules ferromagnétiques douces sont déposées sur la surface d'un liquide et soumises à un champ d'induction. Ils émergent de la compétition entre une interaction dipolaire magnétique et l'effet Cheerios, une force attractive due à la déformation du ménisque. Sous des champs variables, ces structures auto-assemblées nagent le long de l'interface. Grâce à leur simplicité conceptuelle, ils permettent de vérifier et d'étendre notre compréhension générale des micronageurs. Différents arrangements de particules peuvent être réalisés dans le but d'accomplir divers objectifs : du plus simple nageur unidimensionel à la plus complexe structure inspirée du vivant ; d'un nageur rapide et contrôlable à un transporteur de cargaison ou mélangeur de fluides. [less ▲]

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See detailSynthesis and AFM-based Single-Molecule Force Spectroscopy of Helical Aromatic Oligoamide foldamers
Devaux, Floriane ULiege

Doctoral thesis (2018)

In this work, we describe the synthesis of aromatic oligoamide foldamers designed for AFM-based single-molecule force spectroscopy (SMFS) and the detailed investigation of their mechanical properties by ... [more ▼]

In this work, we describe the synthesis of aromatic oligoamide foldamers designed for AFM-based single-molecule force spectroscopy (SMFS) and the detailed investigation of their mechanical properties by this technique. The aim of the thesis was to gain insights into the forces governing the folding and the mechanochemical properties of synthetic folded molecules. We designed and studied three different kinds of helical foldamers to investigate the influence of the size of the foldamer and of the chemical architecture on the mechanical properties at the level of the single molecule in organic solvents. Pulling experiments on quinoline-based foldamers of four different sizes revealed a characteristic unfolding pattern, consistent with the sequential opening of the same groups of interactions involved in the helical conformation. The length of the unfolding patterns is proportional to the foldamer size, while the average unfolding forces show non-linear force dependence. This result highlighted the cooperativity of the interactions originating from the chemical sequence in the folding. From pulling-relaxing SMFS experiments, we evaluated the unfolding free energies and evidenced the capacity of the unfolded molecules to rapidly refold under the mechanical load. Together with experiments in different solvents, these results demonstrate the high robustness of this class of foldamers. SMFS experiments on the naphthyridine-constituted foldamer confirmed its helical structure and suggested that the strength of the interactions along the foldamer are weaker for a wider helix. The insertion of a methylene bridge in the aromatic oligoamide sequence showed a substantial effect on the mechanical properties. The aliphatic junction indeed disrupts the interaction continuum in the helical conformation under load. Providing detailed characterizations down to the single-molecule level, which are complementary to the traditional ensemble experiments, we also showed that helically folded aromatic oligoamides are a genuine class of foldamers with very promising properties as building blocks for mechanized nanomachines. [less ▲]

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See detailHow to Support Environmental Protection Policy in Agriculture: A Case Study in Henan and Hebei Provinces, China
Yang, Xiaomei ULiege

Doctoral thesis (2018)

Crop straw (agricultural residue) is one of the most important biomass resources in China. Crop straw is either burned in the field or collected for recycling. Open burning of crop straw releases ... [more ▼]

Crop straw (agricultural residue) is one of the most important biomass resources in China. Crop straw is either burned in the field or collected for recycling. Open burning of crop straw releases particulate matter and gaseous pollutants, which play a key role in poor air quality, prompting heavy haze episodes during the harvest season. Such episodes threaten human health and interfere with social and economic activities. In contrast, recycling of crop straw reduces open burning and avoids its negative environmental impacts. In fact, improving the efficiency of straw use contributes to a circular economy, dedicated to reducing waste, while also making the best use of any ‘waste’ in economically viable processes that increase its value. Returning straw to agricultural fields in China is the easiest solution and the most important measure promoted by governments promising clean technologies to replace open burning. Recently, China’s municipalities have issued regulations forbidding outdoor burning of straw to reduce air pollution and have passed regulations to encourage farmers to use straw shredders during harvesting, and return crop straw as a bio-fertilizer. However, these regulations have not achieved the desired results, with ongoing open burning and reluctant use of straw on fields. In the first part of this research, urban residents’ willingness of to pay (WTP) for a corn straw ban in Henan (China) was assessed using contingent valuation in a face-to-face survey. Such assessments are important for policy makers to determine the investment and policy instruments for regulating the environmental impacts of straw open burning. The expected WTP analyzed using the Tobit model was about 77 RMB per person per year for the total respondents and 143 RMB per person per year for respondents with positive WTP bids. Aggregate values were between 3.4 and 3.9 billion RMB, suggesting that the corn straw burning ban is of considerable economic value in Henan. In the second part of this research, the factors affecting farmers’ willingness to participate in corn straw return and their willingness to accept compensation (WTA) were explored using a questionnaire survey and face-to-face interviews. A logistic regression model was used to assess adoption success, and the Tobit model was used for WTA analysis. High machinery costs, amount of straw returned, and slow decomposition rates of straw were the most significant factors negatively influencing adoption of this practice. They had a positive influence on the WTA. Poor quality of the straw was another significant factor reducing the probability of using straw return technology. Sown areas and soil improvements associated with adding straw wereoth positive factors determining adoption of the practice and negative determinants affecting WTA compensation. The mean WTA for the total respondent sample was 47 RMB per mu. In the third part of this research, a field experiment was carried out to compare the effects of tillage (minimum/full tillage) combined with corn straw return (mulching, incorporation, and removal) and irrigation (reduced/normal irrigation) methods on wheat productivity and water conservation. In 2013-2014, the yield for minimum tillage with residue mulch (MTm) was slightly but not significantly higher than the yield under full tillage with residue incorporation (FTi). Yields for MTm with reduced irrigation were 10.2% higher than FTi and reduced irrigation. The positive crop response to MTm may reflect higher topsoil moisture and soil temperature under MTm compared with FTi during winter. In conclusion, this study showed there is huge value to prohibiting open burning of corn straw to improve air quality. Despite machinery and operational problems that negatively influence farmers’ enthusiasm for straw return, minimum tillage coupled with corn straw return does benefit subsequent wheat yields. [less ▲]

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See detailSynthèse et application de complexes organométalliques et d’hétérocycles dérivés de sulfonamides
Etse, Koffi Senam ULiege

Doctoral thesis (2018)

Ces dernières décennies, la synthèse de nouveaux composés aux structures toujours plus complexes n’a cessé de progresser grâce aux apports de la catalyse. Que ce soit par la formation de liaisons C―C, C―N ... [more ▼]

Ces dernières décennies, la synthèse de nouveaux composés aux structures toujours plus complexes n’a cessé de progresser grâce aux apports de la catalyse. Que ce soit par la formation de liaisons C―C, C―N et C―O, la réduction de composés carbonylés ou l’oxydation des alcools, les complexes de métaux de transition se sont montrés très efficaces dans l’amélioration des réactions. La polyvalence des complexes à base de palladium a plusieurs fois été démontrée et c’est dans ce sens que les travaux de Richard F. Heck, Ei-ichi Negishi et Akira Suzuki ont été récompensés en 2010 par le Prix Nobel de Chimie pour le développement de couplages catalysés par le palladium en synthèse organique. Notre ambition visait initialement à développer une nouvelle famille de carbènes N-hétérocycliques dérivés de sels de benzothiadiazine comme ligands pour des complexes de métaux de transition. Suite aux échecs répétés en matière de cyclisation, ce projet a été réorienté afin de valoriser les intermédiaires formés. Ainsi, dans cette thèse, nous avons étudié plusieurs approches centrées sur les sulfonamides, la synthèse de complexes de palladium et la formation de nouveaux hétérocycles par voie catalytique. En nous intéressant aux benzoisothiazoles, nous avons décrit l’état de l’art et diverses avancées dans la synthèse de sultames. Nous avons poursuivi en rappelant des grandes réactions catalysées par les complexes de palladium et l’influence des ligands sur l’activité de ces complexes. Pour conclure l’introduction, nous avons souligné l’intérêt des complexes organométalliques en biologie et leur possible potentiel comme matériau d’électrode dans les batteries au lithium. Dans le premier chapitre, afin de mettre au point une voie de synthèse des dibenzoisothiazines, nous avons développé une nouvelle méthode de synthèse des N-sulfonylformamides portant des substituants alkyle et aryle. Ces composés sont des intermédiaires pour la synthèse des ynamides. La préparation des N-sulfonyl-formamides procède par une étape de déprotonation des formamides par le n-BuLi suivie de l’addition d’un chlorure de sulfonyle à -100 °C. Nous avons proposé un mécanisme qui permet d’expliquer la formation du produit désiré et des sous-produits. L’analyse par thermogravimétrie a montré que les N-sulfonylformamides sont stables dans une large gamme de température et ne subissent pas de perte du groupe carbonyle avant leur décomposition complète. Après la mise au point de cette réaction et l’obtention de l’ynamide, la synthèse des benzoisothiazoles catalysée par des complexes de palladium a fait l’objet du Chapitre II. En effet, en nous basant sur la méthode de synthèse des carbazoles décrite par Witulski, nous avons imaginé la synthèse de dibenzoisothiazines par une réaction de cycloaddition entre un diyne et un alcyne libre. Les tentatives de synthèse du diyne ont conduit dans les conditions classiques du couplage de Sonogashira au 3-ylidène-dihydrobenzo[d]isothiazole 1,1-dioxide substitué par un alcyne. Ces ènynes présentent une architecture originale et sont potentiellement des composés bioactifs. Nous avons montré que cette réaction procède par un mécanisme de type tandem Heck–Sonogashira et peut être étendue à plusieurs alcynes terminaux. Dans le Chapitre III, l’activation de la liaison C―X caractéristique du couplage de Heck–Sonogashira a ouvert la voie à la synthèse de nouveaux complexes. A cet effet, nous avons valorisé une série de 2-halogénobenzènesulfonamides comme ligands pour la synthèse de complexes de palladium. Plusieurs complexes ont été obtenus par addition oxydante sur le complexe Pd(PPh3)4. L’étude du produit par RMN du proton et du phosphore démontre que, bien que l’isomère trans soit le plus stable et le plus abondant, l’isomère cis est également formé mais de façon minoritaire. Nous avons aussi observé que plus l’encombrement stérique du substituant sulfonamide porté par le ligand aryle est grand, plus la forme cis est favorisée. Après cristallisation, seule la structure moléculaire des isomères trans a été obtenue par diffraction des rayons X. Ces complexes ont montré une bonne activité catalytique dans la réaction de cyclopropanation du styrène et les résultats ont montré que les complexes portant des ligands brome et arylsulfonamides encombrés stériquement sont plus efficaces dans cette réaction. L’activation de la liaison C―I mise au point dans le chapitre précédent a été mise à profit pour la synthèse d’une série de complexes de formule générale [PdX(PPh3)2(4-RC6H4)], R étant H, OMe et OAc. Grâce à la modification du ligand aryle, seule la forme trans est obtenue attestant de complexes isomériquement purs et adaptés à des études biochimiques. La méthode de synthèse décrite par Flemming pour les complexes bromés et chlorés a été améliorée en réalisant la réaction one-pot dans un milieu biphasique eau/toluène, ce qui ne nécessite alors qu’une faible quantité de KBr et KCl. L’étude de l’activité antiradicalaire de ces complexes a été réalisée en utilisant deux tests chimiques (ABTS et DPPH) et un système enzymatique HRP-H2O2/L-012. L’ensemble des résultats montre que les complexes [PdX(PPh3)2(4-MeOC6H4)] avec X = I, Br et Cl possèdent une très bonne activité antioxydante et antiradicalaire. Par contre, les résultats ne permettent pas de mettre en évidence l’effet de l’halogène sur le pouvoir antioxydant de ces complexes. Une étude cinétique a révélé que les molécules synthétisées réagissaient plus rapidement avec le radical DPPH• qu’avec le radical cation ABTS•+ et que le mécanisme impliqué dans la réaction variait suivant le radical. L’étude cinétique a aussi permis de mieux évaluer et de classer l’activité de ces composés. Dans le dernier chapitre de la première partie, la stabilité et les processus rédox mis en évidence par trois des complexes étudiés au chapitre précédent, à savoir [PdI(PPh3)2(4-AcOC6H4)], [PdBr(PPh3)2(4-AcOC6H4)] et [PdCl(PPh3)2(4-AcOC6H4)], ont été mis à profit en les étudiant en tant que matériaux pour électrode des batteries au lithium. Les complexes iodé, bromé et chloré fournissent une capacité irréversible respectivement de 1089, 444 et 684 mA.h.g-1 lors de la première décharge. Les résultats ont aussi montré que le complexe [PdI(PPh3)2(4-AcOC6H4)] présente la capacité spécifique la plus élevée avec une capacité de décharge réversible d’environ 170 mA.h.g-1 après 200 cycles continus à une densité de courant de 50 mA.g-1. En plus, l’ensemble des complexes montre une rétention très intéressante de capacité au-delà de 200 cycles. Dans la deuxième partie de cette thèse, nous nous sommes intéressés aux dérivés de benzodioxoles et des dicétopipérazines comme intermédiaires vers la première synthèse totale du brasiliamide. Ainsi, dans le Chapitre VI, nous avons mis au point une voie de synthèse de l’acide 2-amino-3-(7-méthoxybenzo[d][1,3]dioxol-5-yl) propanoïque, un précurseur biosynthétique des brasiliamides. Les tests biochimiques révèlent que ce composé et certains de ses précurseurs possèdent une activité antiradicalaire vis-à-vis du radical DPPH• et peuvent inhiber efficacement la réaction d’oxydation de la HRP induite par les ROS. De plus, les résultats cellulaires montrent que l’acide 2-amino-3-(7-méthoxybenzo[d][1,3]dioxol-5-yl)propanoïque peut empêcher la production des ROS chez la souche cellulaire HL-60 sans pour autant être une molécule cytotoxique. Enfin, le dernier chapitre de cette thèse a été consacré à des études préliminaires de la condensation de deux acides aminés en vue de la synthèse des brasiliamides. Ainsi, la synthèse et l’étude conformationnelle de la 1,4-diacétyl-3,6-bis(phénylméthyl) pipérazine-2,5-dione ont été réalisées. La structure moléculaire obtenue par diffraction des rayons X a montré que la molécule est centrosymétrique et les paramètres de Cremer et Pople révèlent que le cycle dicétopipérazine adopte une conformation chaise écrasée. Les données cristallographiques ont ensuite été comparées à celles obtenues par calcul théorique en phase gazeuse. Parmi les trois conformations les plus stables, une seule présente la même disposition des groupes benzyle autour du cycle dicétopipérazine montrant que l’adoption de cette conformation est la force motrice de l’inversion de stéréochimie d’un résidu phénylalanine. [less ▲]

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See detailRestauration écologique en carrière, habitats analogues et résistances aux invasions végétales
Pitz, Carline ULiege

Doctoral thesis (2018)

Growing concern over the continued global loss of biodiversity has led to increased efforts for biodiversity conservation and restoration in anthropogenic ecosystems. Mining activities and introduction of ... [more ▼]

Growing concern over the continued global loss of biodiversity has led to increased efforts for biodiversity conservation and restoration in anthropogenic ecosystems. Mining activities and introduction of exotic species are listed as two of the seven major causes of human disturbance. Many studies have shown that adequate quarry management can significantly improve biodiversity. On the other hand, it is generally accepted that the choice of an appropriate target ecosystem is a decisive factor in the success of any restoration program, particularly in anthropogenic ecosystems. One of the major challenges in these novel ecosystems is to identify to which natural habitat they can be analogous (to define new restoration targets) and to deepen our understanding of the ecological (taxonomic and functional) succession that is naturally taking place in these human ecosystems, in order to know how and under which circumstances can restoration programs rely on spontaneous succession to sufficiently develop the target habitat (passive restoration) and when and to what extent human intervention is more effective (active restoration). In this thesis, we studied the assumption that dry zones of calcareous quarries could be analogous to semi-natural grasslands, and that these natural habitats could be used as restoration target of these dry zones. We based our reasoning on this same premise to establish seed mixtures sown in active restoration, choosing a priori calcareous grasslands species, also because these communities have a dominance of species harboring stress-tolerance strategies, which are theoretically more adapted to this type of bare substrate. We examined plant communities’ types that spontaneously assemble in these dry areas, both taxonomically and functionally, and compared these communities to those of semi-natural reference habitats. To that purpose, we compared field inventories in dry areas of calcareous quarries in the Walloon Region with semi-natural grasslands references vegetation. We also tested the installation of seed mixtures of semi-natural grassland species on different quarry substrates, by the establishment of experimental tests in three quarries of the Walloon Region. The various studies carried out during this thesis allowed the evaluation of passive and active restoration on dry zones of calcareous quarries. They allowed putting into perspective implications for quarry management, in several areas tested through the thesis. White chalk or dolomite dry areas of limestone quarries can naturally be oriented by passive restoration to hay meadows, a community of interest throughout the Walloon Region. It has been demonstrated that on calcareous spoil heap, a technical improvement of the substrate by the addition of a large spectrum of granulometry raw spoil (0-30 mm), allows a considerable improvement of the capacity of grassland species to settle along with a better resistance to Buddleja davidii Franch invasion. Finally, on dry areas of hard limestone quarries, where plant assemblages naturally tend towards mesophilous calcareous grasslands, active interventions could be carried out to promote assemblages of species similar to species-rich temperate grasslands, which have a particularly high conservation value. To that purpose, several restorations options are practicable after exploitation, according to targeted temporality criteria, financial resources that can be allocated and long-term management resources. These techniques include: passive restoration after overcoming dispersion limits; technical improvement of the substrate by the addition of a large spectrum of granulometry raw spoil (0-30 mm) or mimicry of the natural succession by initiating processes with ruderal species. Furthermore, this thesis allowed to identify the main components of biodiversity that should be targeted in order to implement relevant and accepted by all restoration and management actions at European level, to promote and conserve biodiversity at a regional level. In any case, this thesis is a new contribution to the definition of potential analogous habitats in anthropogenic habitats, and to the knowledge of practical methods to optimize ecological restorations in these disturbed limestone quarries habitats, with a view to reaching a balance between installation of vegetation of interest for the conservation of biodiversity and resistance to plant invasions. [less ▲]

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See detailArchitecture et déconstruction, remises en jeu d'une rencontre: raconter, traduire, hériter.
Bodart, Céline ULiege

Doctoral thesis (2018)

Cette thèse s'adresse à un domaine de recherche nommé "architecture et philosophie". La spécificité de ce domaine s'inscrit dans la question d'une coordination possible entre ces deux disciplines. Afin de ... [more ▼]

Cette thèse s'adresse à un domaine de recherche nommé "architecture et philosophie". La spécificité de ce domaine s'inscrit dans la question d'une coordination possible entre ces deux disciplines. Afin de mieux comprendre ce à quoi tient ce "et", nous proposons de revenir sur un épisode singulier de son histoire: la rencontre entre la déconstruction derridienne et la culture architecturale anglo-américaine de la seconde moitié du 20e siècle. Trois parties composent la restitution de cette recherche. Premièrement, il s'agit d'étudier comment se raconte cette rencontre depuis différentes situations d'énonciation (anglo-américaine et francophone), afin de mettre en avant comment des réceptions et appropriations culturelles variées conditionnent des poursuites théoriques spécifiques. D'un milieu à l'autre, entre les versions d'une même histoire, il y a de l'écart. L'objet principal de la thèse est alors d'investir l'écart entre ces versions par la mise en traduction de certaines traces de son histoire (Wigley 1993; Kipnis 1997). La seconde partie propose d'expérimenter comment traduire aujourd'hui en français ce qu'ont produit les Derridean years de l'architecture. Enfin, il s'agit de reconsidérer l'héritage de cette rencontre comme un problème à construire, en vue de remettre en jeu l'histoire longue et oscillante de l'hospitalité des discours de l'architecture. Cette thèse est une focale construite sur un épisode de l'histoire récente. En proposant d'en expérimenter de nouveaux modes d'énonciation, nous soutenons l'hypothèse que ces modes spécifiques permettent de transformer et ré-engager notre attention sur les conditions de rencontre entre architecture et philosophie. [less ▲]

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See detailUpdating Failure Probability of a Welded Joint Considering Monitoring and Inspection - For Offshore Wind Turbine Substructures
Mai, Anh Quang ULiege

Doctoral thesis (2018)

Reliability assessment of existing offshore wind turbine (OWT) support structures taking advantage of historical data from inspection and monitoring is crucial for the optimisation of maintenance and life ... [more ▼]

Reliability assessment of existing offshore wind turbine (OWT) support structures taking advantage of historical data from inspection and monitoring is crucial for the optimisation of maintenance and life extension. In this thesis, the crack inspection data and the monitoring data are separately considered for updating failure probability of welded joints. Concerning crack inspection data, this thesis aims at finding advantages of using the fatigue assessment diagram (FAD) in the failure criteria for failure probability estimation and updating. The crack inspection results (no detection or detected) and possible immediate interventions (repair normally or perfectly) are considered. Failure probabilities are calculated using the FAD and then compared with those obtained from the usual critical crack size criteria. The simulation-based approach is used to calculate and update the failure probability. Crack depth and length are simulated simultaneously. The crack propagations are calculated using a bi- linear Paris’ law with stress-range value varying over time. Uncertainties come from the crack growth parameters, initial crack sizes, fracture toughness, yield and ultimate strengths, FAD formula, stress intensity factor, stress-range values, and the detectable crack size. By combining the fracture toughness with the crack size in the failure criteria, the results show that the estimated failure probability of the welded joint is significantly increased in comparison to the case where only critical crack size is considered in the LSF. In comparison with the failure criteria which includes both the critical crack size and fracture toughness, the FAD approach gives similar reliability results when the applied peak tensile stress is small. However, when the applied peak ten- sile stress is high (the ratio between applied peak tensile stress and yield strength is more than 65%), the FAD approach predicts higher failure probability values. The uncertainty in FAD does not significantly affect the predicted failure probability of the joint as compared to the uncertainties in the ultimate and yield strength. This is because the latter affects directly the cut-off location of the FAD curve where the plastic failure is defined. The FAD approach can be used to update failure probability considering crack inspections and intervention actions. The calculation shows that reliability of the welded joint increases when no crack is detected, or when a crack is detected and repaired. In comparison with a perfect repair, a normal repair assumption significantly reduces the reliability of the joint. With regard to the monitoring data, the research questions how to effectively incorporate the measured strain and the oceanographic data (wind, wave) for updating failure probability of a welded joint in fatigue failure mode. To answer the question, the monitoring data is used to update the characteristics of a random variable in the LSF. Consequently, the updated random variable is then used in a reliability analysis to obtain the updated failure probability. The limit state function (LSF) is based on the Miner’s rule and solved using the first order reliability method (FORM). The random variable used to update failure probability is the joint distribution of wind speed, wave height and wave period. The monitoring data consists of strain, 10-minute mean wind speed, significant wave height, and mean wave period. Fatigue damage is summed up from all load combinations, i.e. from all the discretized components of the joint distribution of wind and wave. The measured strain data is used to calculate fatigue damage in each load combination. The probability of each load combination is calculated us- ing its joint distribution, which in turn can be updated using monitoring data. The 10-minute mean wind speed is assumed to follow a Weibull distribution and can be updated using Bayesian approach. Assuming that the scale parameter is a nor- mally distributed random variable with unknown mean and standard deviation, the predictive distribution of this random variable becomes a student’s t-distribution. The proposed methodology has been applied to a monopile support structure of a wind farm in Belgium. The measured strain is used to find the potential hot-spot location. Stresses are derived at the hot-spot location for fatigue analyses. It is assumed that stress-ranges in each load combination follow a Weibull distribution. The stress-range distribution parameters are found by performing least squares fitting method on the fatigue damage. The results show that the Weibull distribution is generally not very good for fitting stress-ranges in each wind-speed bin for the considered data. However, the inte- grated fatigue damage for the considered load combination is quite accurate since it is the objective of the fitting procedure. The main influence on the remaining fatigue life is the magnitude of stress-ranges at the hot-spot. So the stress conentration factor, the interpolating factor (for example to obtain stresses at under water locations), the correction factor for corrosion effects (if any), and their uncer- tainties should be estimated with great care. The measured 10-minute wind speed data has a significant effect in adjusting the predicted probability of failure and eventually the remaining fatigue life. The duration of strain measurement should be long enough to be combined with oceanographic data. Longer strain measurement duration, greater number of parameters in the oceanographic data can be considered for the failure probability updating. [less ▲]

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See detailEarly life programming by prebiotics or ingredients rich in non-starch polysaccharides in broiler chickens and pigs: effects on growth performance, intestinal maturation and colonization
Li, Bing ULiege

Doctoral thesis (2018)

Prebiotics or ingredients rich in non-starch polysaccharides (NSPs) are often used to improve intestinal health aiming to reduce the use of antibiotics in today’s intensive management farms. These ... [more ▼]

Prebiotics or ingredients rich in non-starch polysaccharides (NSPs) are often used to improve intestinal health aiming to reduce the use of antibiotics in today’s intensive management farms. These ingredients display prebiotic effects when fermented in the large intestine. The maturation and colonization of the intestine starts soon after birth/hatch, and can be programmed by early life interventions, affecting their development even until adulthood. However, the effect of fermentable ingredients applied in the early life is so far poorly investigated. Therefore, we chose 2 popular fermentable ingredients: inulin, a mixture of oligomers and polymers of fructose and wheat bran, a feed ingredient containing high levels of NSPs to investigate their effects on growth performance, intestinal maturation and colonization during the early life in broiler chickens and pigs. In addition, we aimed to evaluate whether the early programming of these ingredients resulted in a lasting effect, when the supplementation was stopped. Moreover, we conducted a test on 4 feed ingredients (galacto oligosaccharides, acidic oligosaccharides, colostrum derivative, prototype oligosaccharides) in suckling piglets. Firstly, inulin and wheat bran were provided to broiler chickens separately or in combination to study their effects during the starter period (Chapter 2) or finisher period (Chapter 3). Per dietary treatment (inulin, wheat bran or the combination), chickens received this ingredient either during the entire rearing period or during the starter period only, aiming at investigating a lasting effect of a temporary supplementation. Inulin had a greater ability to shape the microbial fermentation during the starter period, as seen by Chapter 2. The inclusion of 2% inulin in the diet might have been too high for chickens as it did not affect body weight (BW) and gut morphology positively during the entire life. The beneficial effect on gut morphology when the supplementation was stopped might point to this over-dose too. In contrast, the beneficial effect of wheat ban was mainly on BW during the starter period, and this beneficial effect was lasting until slaughter age, suggesting that wheat bran might be a favourable ingredient during the starter period. It also reduced some potential pathogenic bacteria during the finisher period. The combination of inulin and wheat bran not only demonstrated certain properties of the individual supplemented ingredients, but also showed a synergistic effect, seen by its improved results of BW and gut morphology. Lasting effects of inulin and wheat bran were absent in our study, except for the BW in the wheat bran group. Secondly, we investigated the effect of inulin and wheat bran in pigs. In a first attempt, inulin and wheat bran were provided to suckling piglets in creep feed (Chapter 4). However, a low and uncontrolled intake of creep feed was observed, perturbating the interpretation of the results. Therefore, in a proof-of-concept experiment, in Chapter 5, different amounts of inulin (IN-0.5: 0.5 g/d inulin at birth, increasing weekly with 0.5 g/d inulin and IN-0.75: 0.75 g/d inulin at birth, increasing weekly with 0.75 g/d inulin) were provided to piglets orally during the suckling period. Thereafter, piglets were also reared during 3 weeks after weaning to evaluate the lasting effect induced by the early supplementation with inulin. A dose-effect of inulin was observed. Only IN-0.5 displayed prebiotic effects, improving the BW, the gut morphology, the SCFA profile in the large intestine and selected colonic bacteria. But both inulin-groups reduced gene expressions of some inflammatory markers to help piglets against inflammation. Only the BW and gut morphology were found to have a lasting effect when supplementation was stopped, but it could be just an accumulation of early advantages. Thirdly, we performed an experiment in suckling piglets with a company to test 4 feed ingredients, which belonged to oligosaccharides- and colostrums-derivatives (Chapter 6). All these ingredients improved the BW of piglets during the suckling period, but through the measurement of gene expressions of cytokines (acidic oligosaccharides and prototype oligosaccharides) and microbiota profile (galacto oligosaccharides and prototype oligosaccharides), we did not observe any alterations. In summary, this thesis increased the understanding of the early use of inulin, wheat bran, as well as the other potential prebiotic ingredients in broiler chickens and pigs, especially their effects during the early life. The supplementation of inulin and wheat bran improved growth performance and intestinal parameters in broiler chickens and pigs, but in a dose-dependent way, where an excess amount did not affect them positively. In addition, their prebiotic effects relied on the administration of inulin and wheat bran directly, suggesting no or a weak lasting effect. As for the feed ingredients of oligosaccharides- and colostrums-derivatives, all these ingredients improved the BW of suckling piglets, but did not affect immune response and microbial fermentation. Therefore, the prebiotics or ingredients rich in NSPs could display effects in the early life, however, the early programming of these ingredients did not induce a lasting effect. [less ▲]

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See detailUse of pesticides in Fresh Water Aquaculture in the Mekong Delta, Vietnam, and impacts on environment and food safety
Nguyen, Quoc Thinh ULiege

Doctoral thesis (2018)

The research “Use of pesticides in Fresh Water Aquaculture in the Mekong Delta, Vietnam, and impacts on environment and food safety” consisted of four sections. To evaluate the pressure of drugs and ... [more ▼]

The research “Use of pesticides in Fresh Water Aquaculture in the Mekong Delta, Vietnam, and impacts on environment and food safety” consisted of four sections. To evaluate the pressure of drugs and chemicals in the environment, two surveys were performed in the Mekong Delta. The first was focused on rice and rice-fish system and was conducted in 2009. The second, an in depth survey, conducted in 2013, focused on rice-fish, striped catfish and red-tilapia systems. Results showed that, for the rice-fish system, most rice fish farmers grew 2 rice crops and 1 fish crop per year. Pesticides were applied generally 3 times per crop. Farmers normally applied pesticides based on the recommended doses of producers. Chess 50WG (containing 500g/kg pymetrozine, produced by Syngenta, Vietnam), Bassa 50EC (containing 500g/L fenobucard, produced by Việt Thắng Bắc Giang (Vithaco), Vietnam) and Kinalux (containing 250g/L quinalphos, produced by United Phosphorus Ltd., India) were the most common used commercial pesticides in rice crop, rice-fish crop and distributors as well. According to the majority of the distributors, the use of pesticides will increase in future. The in-depth survey showed that much more active compounds were used in 2013 compared to 2009, but, all of the active compounds belonged to the approved list of Vietnamese government. Few farmers used chemicals during fish crop. Farmers reported their awareness towards the use of agrochemicals in terms of health effects. The survey showed that the farmers select an agrochemical based on their experience. The study on red-tilapia demonstrated that many different types of disinfectants and antimicrobials are used. Further, the cost-effectiveness of such pesticide use, especially for feed supplement products, antimicrobials and disinfectants, is questionable and should be assessed. There is an urgent need to improve the farmer’s knowledge and their access to advisory services on careful use of disinfectants and antimicrobials. All visited striped catfish farms applied drugs and chemicals with seven types of antibiotics during the fish production. Enrofloxacin, sulfamethoxazole and trimethoprim were reported to be the most used chemicals by farmers to treat Bacillary Necrosis of Pangasius (BNP). The survey and practical situation demonstrated that quinalphos, trifluralin and dichlorvos were commonly used in rice fish system and, consequently, may contaminate aquaculture products. A Gas chromatography – mass spectrometry (GC-MS) analytical method was developed and validated according to European guidelines (SANTE/11945/2015) for the determination of residues of those pesticides in water. The developed method was then optimized using a gas chromatography – electron capture detector (GC ECD) technique to make the method more applicable in Vietnam. The developed method was used to analyze water samples collected from the aquaculture system in April 2013, at the beginning of the rainy season. Results showed that only 9 % of the total water samples analyzed contained residues of quinalphos, but only in water from rice fish systems. The other two pesticides, trifluralin and dichlorvos, were not detected. A comparison between GC-MS and GC-ECD indicated that GC-ECD is less sensitive than GC-MS. However, for samples with concentrations detectable with both techniques, no significant difference was observed between the results obtained using both equipments GC-ECD and GC-MS. The next step was to determine the distribution and elimination of quinalphos, the active substance of a popular insecticide used in the Mekong Delta, according to the first survey. An experiment was set up in a rice-fish integrated system in Can Tho City, Vietnam. Quinalphos was applied twice in a dose of 42.5 g per 1000 m2, according to the producer recommendations. Samples (fish, water and sediment) were collected at time intervals and were analyzed by GC-ECD. The results showed that quinalphos residues in fish muscles were much higher than those in the water and the bioconcentration factor (logBCF) was above 2 for the fish. The half-lives, after the first and second quinalphos applications, were 12.2 and 11.1 days for sediment, 2.5 and 1.1 days for silver barb, 1.9 and 1.3 days for common carp, and 1.1 and 1.0 days for water, respectively. Finally, as a case study including 3 commonly used pesticides (quinalphos, trifluralin and dichlorvos), dioxins and one forbidden antibiotic (chloramphenicol), the risk for the consumer, linked to the chemical contamination of the aquaculture related environment was evaluated. Sediments samples were collected including 10 samples collected from catfish ponds in An Giang Province and 12 samples randomly collected from rice-fish systems in Can Tho City. Analytical results showed that 3 from the 13 water samples collected from rice field were contaminated with low levels of quinalphos (with concentrations of 0.11, 0.08 and 0.04 μg/L). The other investigated pesticides were not detected in any sample. For chloramphenicol (CAM) residues in fish samples, analysis was performed on 36 fish samples of catfish (18 samples included 9 from small scale and 9 from large scale systems), snakehead (9 samples) and climbing perch (9 samples) collected at the beginning, middle and at the end of culture period. Results showed that one sample of climbing perch and one sample of snakehead were contaminated with traces of CAM (concentrations of 0.17 and 0.19 µg/kg, respectively). It appeared that CAM was not detected in catfish samples neither from the beginning to the end of the crop, nor from small and large scale systems. Dioxins were not detected in any of the collected sediments samples. In order to assess the general risk for the Vietnamese consumer of fish, a survey was performed in Can Tho City, using a questionnaire designed to collect information. A large part of interviewees (77%) stated that they like to eat fish. The number of days of eating fish was 3.4 days per week. In this study, the average amount of fish consumption ranged between 90 and 140 g per day. It was shown that the daily intake of trifluralin of interviewed people was 0.05 µg/kg body weight/day. This level of exposure was much lower than the acceptable daily intake (ADI) (15 µg/kg/day) (EFSA, 2015). However, trifluralin has not been approved in EU, so the presence of residues of trifluralin in aquatic product, even if they cause no problem for the consumer, would be a problem for aquatic product export. [less ▲]

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See detailClimate change in Belgium: recent and future evolution of global radiation and hydroclimatic conditions favouring floods using the regional climate model MAR
Wyard, Coraline ULiege

Doctoral thesis (2018)

In Belgium, the future response of the climate to increasing greenhouse gas concentration is not clear, especially with regard to the perturbations of the precipitation regime, snow cover, and global ... [more ▼]

In Belgium, the future response of the climate to increasing greenhouse gas concentration is not clear, especially with regard to the perturbations of the precipitation regime, snow cover, and global radiation. On the one hand, existing studies show results which differ strongly either according to the future scenario, or from one model to another. On the other hand, there is even an absence of studies focussing on Belgium regarding future changes in snow cover and global radiation. Given their potential impacts on the society (water management, energy supply, biodiversity, tourism), future changes in precipitation, snow cover, and global radiation require further research. As the orography, the exposition to the dominant winds, and the proximity of the North Sea determine a large spatial variability in the Belgian climate, the latter requires a fine representation of these features to be properly simulated. Compared to global climate models (GCM), regional climate models (RCM) are recognized for their ability to represent climatic phenomena with higher spatial resolutions. In the framework of this doctoral thesis, the RCM MAR (for "Modèle Atmosphérique Régional" in French), which is developed at the Laboratory of Climatology and Topoclimatology of the University of Liège, was applied for the first time to Belgium. The aim was first to assess the performances of MAR over Belgium and then to study the current and future evolution of hydroclimatic conditions favouring floods, and also the current and future evolution of global radiation. For this purpose, historical simulations were performed over 1959-2014. Future projections (2006-2100) were then performed under the most pessimist IPCC future scenario (RCP8.5). The horizontal resolution used for both historical and future simulations is 5 km. By comparing the MAR outputs to ground-based measurements from 20 weather stations over 2008-2014, the results show that MAR successfully simulates the spatial and temporal variability of the Belgian climate. In fact, the biases found in the MAR results are non-significant and the correlation coefficients are satisfying with regard to temperature, precipitation, snow height, global radiation and cloudiness. The MAR results are particularly satisfying during the winter months and in High Belgium where the climate is the coldest. Regarding hydroclimatic conditions favouring floods, we focused on the Ourthe catchment. In this river, about 70 % of floods occur during the winter months and result from either the rapid melting of the snow pack covering the Ardennes eventually combined with rainfall or abundant rainfall alone. The current evolution of hydroclimatic conditions favouring floods was first assessed for the period 1959-2010. Conditions favouring floods in the Ourthe River present a negative trend over 1959–2010 as a result of a decrease in snow accumulation and a shortening of the snow season. Regarding the impact of the evolution of extreme precipitation events on hydroclimatic conditions favouring floods, the signal is less clear because the trends depend on the data used to force the MAR model. By the end of the 21st century, under the most pessimist scenario, the results show an acceleration of the snow cover depletion resulting in a decrease in conditions favouring floods. Further, the impact of the evolution of extreme precipitation events on hydroclimatic conditions favouring floods, no significant change was found although these trends are subject to uncertainties due to the deficiencies of the convective scheme of MAR. Regarding global radiation, its current evolution was first assessed for the period 1959-2010. In addition, we consider two distinct periods in our analysis: 1959-1979 (dimming) and 1980-2010 (brightening). For both the dimming and the brightening periods, our results show that the annual global radiation trends are mainly driven by global radiation changes in spring and summer. The increase in global radiation observed in Belgium since the 1980s and especially since the 2000s could mainly be explained by a decrease in low and medium cloud cover. This would strengthen the effect of the decrease in aerosol load on global radiation that has been observed in Europe since the 1980s. The origin of these changes in cloudiness is not clear and could result from changes in both aerosol-cloud interactions and atmospheric-circulation, such as more frequent tropical air advections and more frequent anticyclonic conditions over Western Europe due to the poleward shift of extratropical storm tracks. These changes in the atmospheric circulation may result from global warming and may persist in the future. In fact, by the end of the 21st century, under the most pessimist scenario, the models simulate an increase in the blocking regime frequency in summer over Europe. For Belgium, this implies more frequent anticyclonic conditions favouring cloudless conditions. The future projections performed with MAR exhibit significant decreasing total cloud cover, and particularly decreasing low and medium cloud cover. However, this declining cloud cover leads to contrasting changes in global radiation depending on the data used to force MAR. [less ▲]

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See detailLa collection et la revue Poétique. Histoire intellectuelle, sociale et matérielle d'une discipline moderne (1970-1987)
Lorent, Fanny ULiege

Doctoral thesis (2018)

Cette thèse se veut un essai d’histoire intellectuelle, sociale et matérielle appliqué à une discipline moderne, la poétique. De la poétique, telle qu’elle a été refondée au tournant des années 1970 dans ... [more ▼]

Cette thèse se veut un essai d’histoire intellectuelle, sociale et matérielle appliqué à une discipline moderne, la poétique. De la poétique, telle qu’elle a été refondée au tournant des années 1970 dans le lointain sillage d’Aristote, ce travail n’entend pas donner le dernier mot sur la définition, les objets, les méthodes. Il s’agit plutôt de fournir la chronique, pas à pas, texte par texte, de la façon dont une telle appellation a été mobilisée dans le second XXe siècle dans deux lieux spécifiques : la revue et la collection « Poétique », fondées en 1970 par Gérard Genette, Tzvetan Todorov et Hélène Cixous, et publiées par les Éditions du Seuil. En effet, c’est un critère éditorial qui a régi, au départ, mon enquête. Subordonner de la sorte les savoirs disciplinaires à un découpage « matériel » m’a semblé le premier geste à poser pour se démarquer d’une histoire des idées abstraite et idéaliste. Les textes ne sont pas compris, dans ce travail, en tant qu’entités désincarnées, mais en tant qu’objets, livres, numéros de revue. Cet angle d’approche permet de mener une étude qui, sans négliger le contenu conceptuel des textes, inscrit ceux- ci dans l’ensemble de la chaîne sociale mobilisée pour produire et diffuser les objets dans lesquels ils se réalisent. Ces derniers, unités pertinentes de la présente thèse, s’offrent aux yeux des lecteurs sous certaines configurations graphiques, présentent une composition et une organisation signifiantes des contenus. En outre, ils sont produits par des auteurs (dont la formation, la nationalité, l’appartenance professionnelle, le réseau amical, etc. doivent être pris en compte), et circulent dans un espace social, dans une communauté savante spécifique, et parfois au-delà. Telles sont les diverses dimensions que j’ai souhaité tenir ensemble dans cette thèse, laquelle espère se situer à la croisée de l’histoire des idées, de l’histoire du livre et de l’édition, de la sociologie des intellectuels et de ce que l’on commence à nommer aujourd’hui, à la suite de Marie-Ève Thérenty, la poétique des supports. Cette chronique de la poétique dans et par Poétique et « Poétique » est organisée en quatre temps. Un long prologue, courant de 1963 à 1970, est destiné à saisir en acte la manière dont le terme poétique, après des années d’absence, est réapparu sur la scène intellectuelle, a circulé et s’est enfin stabilisé pour venir désigner le programme auquel la revue et la collection « Poétique » entendent répondre à leur fondation. Ensuite, trois chapitres correspondent aux restructurations internes de la revue et de la collection. Les trois périodes délimitées (1970- 1973 ; 1974-1978 ; 1979-1987) se soldent par le départ de Todorov de la direction de la collection. Si « Poétique » et Poétique sont toujours actives aujourd’hui, j’ai néanmoins choisi de me concentrer sur la période s’étendant de 1970 à 1987. Cruciales pour le paradigme structuraliste, ces années nous mènent des prémisses de la poétique moderne aux premiers moments de sa remise en cause par un retour de l’histoire littéraire. Elles permettent ainsi d’envisager comment la discipline s’est repensée, renouvelée sans cesse, pour survivre jusqu’à nos jours. [less ▲]

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See detailPancreatic Beta Cell Regeneration in Zebrafish : Investigation of the Ductal Contribution and Involved Molecular Mechanisms
Bergemann, David ULiege

Doctoral thesis (2018)

The pancreas, along with its major role in digestion, holds one of the most important cell type involved in glucose homeostasis : the insulin-producing β cell. Diabetes mellitus is characterized by a ... [more ▼]

The pancreas, along with its major role in digestion, holds one of the most important cell type involved in glucose homeostasis : the insulin-producing β cell. Diabetes mellitus is characterized by a disturbed blood glucose balance resulting from a lack or an inadequate secretion/action of insulin. A hallmark of diabetes is the loss of β cells either by an autoimmune destruction (T1D) or by an ongoing exhaustion and subsequent cell death associated with the inability to fit metabolic demands (T2D). As this disease has become a major burden in our modern society, efforts are needed to provide effective therapeutic strategies. While current strategies rely on exogenous insulin supply and glycemic control through medication, restoring a functional β cell pool represents the most promising solution to tackle the disease at its root. To this regard, regeneration studies have provided evidence that β cells can be produced by stimulating their replication or by (trans)differentiation of different cellular sources. In this work, we investigated the possibility that the pancreatic ductal compartment can be a source of regenerated β cells. In order to study regeneration and unravel underlying mechanisms, we conducted our work in the regeneration prone zebrafish model which was previously shown to regenerate its β cells in a very efficient manner. By using a combination of transgenic tools and deep RNA-sequencing, we were able to show that adult pancreatic duct cells display a progenitor-like behavior and that they constitute a source of regenerated β cells. We then used comparative transcriptomics in order to get an insight into the molecular mechanisms (gene regulation) occurring in the ductal cells during regeneration. This provided us with candidate signaling pathways and genes possibly involved in regeneration. To determine their importance in this process, we initiated functional studies by targeting pathways with pharmacological inhibitors/activators. Among the candidates, the Ca2+/calcineurin signaling axis seemed most promising and will be further investigated for its implication in regeneration. In parallel, we also underlined an important pro-endocrine role for the transcription factor ascl1b in β cell regeneration from the ducts. Lastly, this work prompted us to further improve the nitroreductase-mediated ablation system used in regeneration studies. Thus we characterized Nifurpirinol as a more potent substrate than the gold-standard prodrug Metronidazole which displayed suboptimal and variable cell ablation efficiencies. Altogether, our work strengthens the hypothesis that adult pancreatic ducts contain progenitors able to differentiate into β cells and provides new research leads regarding targetable signaling pathways and genes for the stimulation of β cell regeneration. Understanding the fundamentals of β cell regeneration taking place in zebrafish might thus pave the way towards stimulating these mechanisms in diabetic patients. [less ▲]

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See detailTargeted metabolomic study in Brassica napus L. under cadmium and epoxiconazole stress
Durenne, Bastien ULiege

Doctoral thesis (2018)

Investigations carried out during this thesis consisted in the research of volatile and non-volatile abiotic stress markers using winter oilseed rape (Brassica napus L.), a major crop worldwide. Two ... [more ▼]

Investigations carried out during this thesis consisted in the research of volatile and non-volatile abiotic stress markers using winter oilseed rape (Brassica napus L.), a major crop worldwide. Two specific abiotic stresses involved in current agricultural soil threats were studied such as cadmium (Cd), a carcinogen trace heavy metal, and epoxiconazole being a persistent systemic fungicide. A targeted metabolomic approach was therefore used through the analysis of volatile organic compounds (VOCs) profiles, targeting terpenoid compounds largely described in plant abiotic stress response, and through the profiling of glucosinolates (GSLs) as non-volatile sulfur-containing metabolites within Brassicaceae. A new glass device allowing the plantlets growth and the non-invasive dynamic sampling of emitted VOCs was successfully developed. It can be described as an innovative laboratory and high-throughput plant chambers system. Oilseed rape plantlets analysis was performed under sterile and controlled conditions, using in vitro medium in the case of experiments related to cadmium exposure and using perlite as a soil-similar substrate for testing epoxiconazole. A phenotyping based on plantlets observations and physiological measurements under cadmium and epoxiconazole stress: i) characteristic symptoms (chloroses), ii) root and shoot growth and iii) biomass was performed at vegetative stage, in complementarity with the targeted metabolomic approach. Different levels of stress were tested on oilseed rape plantlets through dose-response experiments in order to obtain a concentration gradient representing defined stress conditions (i.e. low, middle and severe). With respect to cadmium stress, the concentration of Cd and sulfur (S) has been also measured in the different plant organs such as roots and shoots. GSL profile and content in plantlet organs were also investigated in order to highlight their putative involvement in Cd stress tolerance. About epoxiconazole stress, a characterisation of molecule concentration in the plantlets was carried out before studying its impact on terpenes profiles and on the breakdown products of GSLs (i.e. isothiocyanates) as putative metabolic markers. Overall results showed that metabolic markers could be identified for both kinds of stress such as cadmium and epoxiconazole. These molecules were also involved in adaptive response of plantlets to stress. The sesquiterpenes clearly emerged from the experiments as VOC stress markers. In addition, the role of GSLs in the mechanisms of Cd-tolerance was highlighted with an emphasis on importance of oilseed rape primary S metabolism. The non-invasive method of rapid analysis of VOCs emitted by oilseed rape plantlets and terpenes quantitation could certainly be used for studying the relationships between plant-emitted VOCs and other abiotic or biotic stresses. Finally, this customised glass chambers system could be used in regards to other plants such as potatoes, sugar beets and vegetable crops using soil substrate in order to discover new putative metabolic markers. [less ▲]

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See detailEchanges de composés organiques volatils d'origine biogénique entre deux écosystèmes agricoles et l'atmosphère
Bachy, Aurélie ULiege

Doctoral thesis (2018)

Some volatile organic compounds (VOC) have a significant effect on climate and air quality. They are mainly or partially exchanged by terrestrial ecosystems, hence they are called BVOC for biogenic VOC ... [more ▼]

Some volatile organic compounds (VOC) have a significant effect on climate and air quality. They are mainly or partially exchanged by terrestrial ecosystems, hence they are called BVOC for biogenic VOC. Many studies were conducted in order to quantify and understand BVOC exchanges between these ecosystems and the atmosphere. However, so far croplands have been poorly studied yet, despite their importance in term of land use at the global scale. Therefore, this thesis focused on ecosystem-atmosphere BVOC exchanges for the two most important cultures worldwide, i.e. wheat and maize. Four objectives were pursued: - Qualify, - Quantify, - Understand the BVOC exchanges mechanisms for both cultures and - Evaluate the ability of up-scaling models (currently used by atmospheric chemistry models to simulate BVOC emissions from terrestrial ecosystems) to reproduce the BVOC exchanges observed in the framework of this thesis. For that purpose, three measurement campaigns were carried out at the Lonzée Terrestrial Observatory (LTO, Belgium): the first on a maize field, the second on a winter wheat field and the third on a bare soil. BVOC fluxes were measured at the ecosystem-scale by using the disjunct eddy covariance by mass scanning technique, with a mass spectrometer for BVOC ambient mixing ratio measurements, during the whole (maize) or the most part of the (winter wheat) growing season. These measurement campaigns are original especially because of their broad and high temporal coverage, which enabled to characterize all vegetation stages in situ and in details. Both the maize and the winter wheat field exchanged mainly methanol. The exchanges were bidirectional but the emissions were much more important than the uptakes. The fluxes were correlated with the temperature, the radiation and the water vapor fluxes. They were also triggered by plant phenology. In addition, the soil exchanged significant amounts of BVOC, methanol being the main exchanged compound. This result is original because it counteracts with the common assumption that soil BVOC exchanges are one to three orders of magnitude lower than plant BVOC exchanges. The soil methanol exchanges were driven by a physical adsorption-desorption process coupled with a methanol source which depended on soil surface temperature. They decreased along with the development of the canopy (leaf and above-ground biomass). Then, the tested up-scaling model was able to reproduce the methanol exchanges observed at LTO between the winter wheat field and the atmosphere when the canopy was well established, so that soil exchanges were reduced. Several parameters of the model were nevertheless strongly modified to adjust the model to the data; otherwise the model overestimated the exchanges by a factor of 3. Lastly, the BVOC exchange rates varied strongly between this study and the other studies conducted on croplands. More generally, we observed strong differences in BVOC exchange rates among all studies, and this even for the same cultivated crop species end under similar temperature, radiation and phenology conditions. Thanks to the two broad measurement campaigns which enabled the analysis of temporal BVOC flux dynamics as well as their relationships with the meteorological variables and the ecosystem (plant development – soil), this thesis brings original values for the exchanges rates, the BVOC budget and the parameters for up-scaling models. In addition, it highlighted or made possible to suggest some exchange mechanisms and this for the two main crops species worldwide, under a temperate climate, with a silty loam soil and conventional crop management techniques. These results should therefore help improving the performance of the models when estimating BVOC exchanges for that region, since they currently use parameters based on few representative species (in terms of cultivated surface) or default values (because of a lack of available flux data) for croplands. The factors causing the differences in BVOC exchanges rates for a same crop species and under similar meteorological and phenological conditions should nevertheless be better constrained. For that purpose we suggest comparing the BVOC exchanges from several wheat, maize and rice varieties, which are the three main crop species in the world, in terms of cultivated area, under various pedoclimatic conditions and crop management practices. Plant and soil BVOC exchanges should furthermore be disentangled, in order to better constrain the exchange rate differences observed at the ecosystem-scale. [less ▲]

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See detailBiomasse et stocks de carbone en Afrique centrale: importance de l'allométrie des arbres
Loubota Panzou, Grâce Jopaul ULiege

Doctoral thesis (2018)

Quantifier les stocks de biomasse et de carbone dans les forêts tropicales est essentiel pour la mise en oeuvre des stratégies d’atténuation des changements climatiques, et notamment le mécanisme de ... [more ▼]

Quantifier les stocks de biomasse et de carbone dans les forêts tropicales est essentiel pour la mise en oeuvre des stratégies d’atténuation des changements climatiques, et notamment le mécanisme de réduction des émissions dues à la déforestation et la dégradation (REDD+). Les scientifiques s’accordent aujourd’hui à utiliser une équation allométrique de biomasse générale, combinée à une allométrie hauteur-diamètre ajustée sur des données locales non-destructives. Or, l’allométrie des arbres varie néanmoins, entre les espèces et stratégies fonctionnelles d’une part, entre les types de forêts et conditions du milieu d’autre part. L’objectif général de cette thèse de doctorat était d’étudier les variations de l’allométrie des arbres en vue d’améliorer les estimations de la biomasse et des stocks de carbone en Afrique centrale. Les variations de l’allométrie des arbres étaient étudiées à deux échelles : (1) entre espèces coexistentes au sein d’un type de forêt ; et (2) entre sites et types de forêts. A l’échelle des espèces, les variations des allométries hauteur-diamètre et houppier-diamètre ont été reportées entre les 45 espèces d’arbres coexistentes d’un site représentatif des forêts semi-décidues à Celtis du nord Congo. Les relations entre les traits architecturaux (hauteur totale et dimensions du houppier) dérivés à partir des allométries spécifiques aux espèces et les traits fonctionnels ont mis en évidence un continuum d’espèces entre les espèces de grande taille dominant canopée et les espèces de petite taille dominant le sous-bois. Les espèces d’arbres de grande taille étaient exigeants en lumière, dispersées par le vent, décidues avec une large contribution à la biomasse forestière, alors que les espèces d’arbres de petite taille étaient tolérantes à l’ombrage, dispersées par les animaux, sempervirentes et plus abondantes en densité de tiges. A l’échelle des sites, nous avons mis en évidence des variations de l’allométrie hauteur-diamètre des arbres entre les types de forêts, et pour la première fois en Afrique centrale, des variations de l’allométrie houppier-diamètre entre les types de forêts. Ces tendances étaient également confirmées pour les espèces communes entre les types de forêts, suggérant un contrôle environnemental sur les variations de l’allométrie des arbres. A partir des allométries spécifiques aux sites, des attributs architecturaux (hauteur totale et dimensions du houppier), en plus des attributs plus classiques de structure (surface terrière, densité de tiges…) et de composition (densité du bois) ont pu être dérivés et reliés aux variations spatiales de la biomasse et des stocks de carbone. Cette thèse de doctorat a fourni de nouvelles données nécessaires sur l’estimation de la biomasse et de stocks de carbone forestiers en Afrique centrale. Il y a également des perspectives pratiques à ce travail, notamment pour les futures cartes de biomasse dans le cadre du suivi du carbone forestier, qui pourraient s’appuyer sur des sites étudiés dans cette thèse. [less ▲]

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See detailContribution of reverse genetics in design of antiviral vaccines
Li, Lin ULiege

Doctoral thesis (2018)

Lin Li. (2018). Lin Li. (2018). Contribution of reverse genetics in design of antiviral vaccines. (PhD Dissertation in English). Gembloux, Belgique, Gembloux Agro-Bio Tech, Université de Liège. Classical ... [more ▼]

Lin Li. (2018). Lin Li. (2018). Contribution of reverse genetics in design of antiviral vaccines. (PhD Dissertation in English). Gembloux, Belgique, Gembloux Agro-Bio Tech, Université de Liège. Classical swine fever (CSF) and pseudorabies are caused by classical swine fever virus (CSFV) or pseudorabies virus (PRV), respectively. Both of them induce important economic losses in many countries, such as China and other developing countries that lack good diagnostic methods and good vaccines. Therefore, in order to wipe out these viruses and protect the animals from virus infection, it is necessary to develop better diagnostic tools and vaccines. In the first part of my thesis, we developed an indirect enzyme-linked immune-sorbent assay (iELISA) to differentiate vaccinated animals from the infected. The results showed that the sensitivity (94.6%) and specificity (97.1%) of the test is very good. The iELISA can thus be employed to diagnose CSF. In the second part of my thesis, we focused on the gE protein of PRV. Using the yeast-two hybrid system, we have isolated 8 proteins from cDNA library interacting with gE. One of these, translocator protein (TSPO) was further characterized. Interaction of gE with TSPO was supported by coimmunoprecipitation and confocal imaging analyzes. We further demonstrate that overexpression of TSPO affects cholesterol levels and suppresses virus attachment and replication. In the third part of my thesis, we studied another viral system. We wrote a review about oncogene-dependent replication of human T-cell leukemia virus (HTLV-1) in the presence of a strong immune response. In conclusion, we have made contributions to a better understanding of different viral systems and provided new tools to improve diagnostics and prevention. [less ▲]

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See detailEnergy-Based Magnetic Hysteresis Models - Theoretical Development and Finite Element Formulations
Jacques, Kevin ULiege

Doctoral thesis (2018)

This work focuses on the development of a highly accurate energy-based hysteresis model for the modeling of magnetic hysteresis phenomena. The model relies on an explicit representation of the magnetic ... [more ▼]

This work focuses on the development of a highly accurate energy-based hysteresis model for the modeling of magnetic hysteresis phenomena. The model relies on an explicit representation of the magnetic pinning effect as a dry friction-like force acting on the magnetic polarization. Unlike Preisach and Jiles-Atherton models, this model is vectorial from the beginning and derives from thermodynamic first principles. Three approaches are considered: the first one, called vector play model, relies on a simplification that allows an explicit, and thus fast, update rule, while the two others, called the variational and the differential approaches, avoid this simplification, but require a non-linear equation to be solved iteratively. The vector play model and the variational approach were already used by other researchers, whereas the differential approach introduced in this thesis, is a new, more efficient, exact implementation, which combines the efficiency of the vector play model with the accuracy of the variational approach. The three hysteresis implementations lead to the same result for purely unidirectional or rotational excitation cases, and give a rather good approximation in all situations in-between, at least in isotropic material conditions. These hysteresis modeling approaches are incorporated into a finite-element code as a local constitutive relation with memory effect. The inclusion is investigated in detail for two complementary finite-element formulations, magnetic field h or flux density b conforming, the latter requiring the inversion of the vector hysteresis model, naturally driven by h, for which the Newton-Raphson method is used. Then, at the finite-element level, once again, the Newton-Raphson technique is adopted to solve the nonlinear finite-element equations, leading to the emergence of discontinuous differential reluctivity and permeability tensors, requiring a relaxation technique in the Newton-Raphson scheme. To the best of the author’s knowledge, the inclusion of an energy-based hysteresis model has never been successfully achieved in a b-conform finite-element formulation before. [less ▲]

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See detailTowards operational use of combined Split-Band Interferometry and Multidimensional Small Baseline Subset: application to geohazard monitoring in the Kivu region
Libert, Ludivine ULiege

Doctoral thesis (2018)

The vulnerable region of Kivu is strongly affected by geohazards such as volcanism and landslides. An essential ingredient for modelling the geophysical processes from which these geohazards originate is ... [more ▼]

The vulnerable region of Kivu is strongly affected by geohazards such as volcanism and landslides. An essential ingredient for modelling the geophysical processes from which these geohazards originate is the measure of the Earth’s surface displacements. In this complex region, monitoring these ground deformations can be efficiently performed by using Synthetic Aperture Radar Interferometry (InSAR). Nevertheless, geophysical modelling requires accurate measurements of the displacements over time, which are not always manageable with conventional InSAR due to area-related limitations such as geometric distortions. Consequently, we consider advanced processing techniques such as Split-Band Interferometry (SBInSAR), which potentially allows to calculate the absolute interferometric phase, and Multidimensional Small Baseline Subset (MSBAS), which reconstructs the history of deformations along the horizontal and vertical directions. The aims of this thesis are the investigation of the SBInSAR and MSBAS techniques for improving the ground deformation measurements, the development of these techniques in order to achieve an operational tool of monitoring, and eventually to combine the information provided by both methods. Regarding the Split-Band Interferometry, we consider its theoretical applicability, determine optimum processing parameters and propose a method that corrects phase ambiguities by using SBInSAR as a complement to classical phase unwrapping, which we call SBInSAR-assisted phase unwrapping. We establish that the best criterion for the detection of spectrally stable pixels is the slope standard deviation. We also study the temporal behaviour of spectrally stable pixels and show that few of them persist over time. We analyze the behaviour of artificial reflectors with respect to SBInSAR and provide strong evidences that there exists a correlation between the signal-to-clutter ratio of a target and its detectability as a spectrally stable pixel. Regarding the Multidimensional Small Baseline Subset, we present the InSAR mass processing chain developed in collaboration with the European Center for Geodynamics and Seismicity for MSBAS preprocessing, and we propose to optimize the spatial coverage of MSBAS measurements by using interpolation or global masking. An MSBAS analysis is carried out over the city of Bukavu for the period from January 2016 to September 2017. We also study temporal decorrelation over the Virunga Volcanic Province and we model it using a decreasing exponential function. As a complement, we implement the Range Split-Spectrum technique in the CIS software for the ionospheric phase compensation in low frequency interferograms. We finally discuss the options for merging SBInSAR and MSBAS together. [less ▲]

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See detailVariabilité des concentrations cellulaires phytoplanctoniques de diméthylsulfoniopropionate (DMSP) et de diméthylsulfoxyde (DMSO) en Baie Sud de la Mer du Nord
Speeckaert, Gaëlle ULiege

Doctoral thesis (2018)

The eutrophication of the Southern Bight of the North Sea has been benefitting to the prymnesiophyte Phaeocystis globosa (P. globosa). This species is a known high dimethylsulfoniopropionate (DMSP ... [more ▼]

The eutrophication of the Southern Bight of the North Sea has been benefitting to the prymnesiophyte Phaeocystis globosa (P. globosa). This species is a known high dimethylsulfoniopropionate (DMSP) producer whose bloom accounts for 95% of spring phytoplankton biomass. An increase in DMS(P) and its oxidation product dimethylsulfoxide (DMSO) cellular contents have been frequently observed in cellular stress conditions. To test this, we have first analysed the natural distribution of DMS(P,O) cellular contents in the North Sea. Secondly, we have measured DMS(P,O) cellular contents in monospecific cultures of several key species of the North Sea and their responses to salinity variations. Our main working hypothesis is that DMSP acts as an osmoregulator and/or as an antioxidant, depending on the species. The DMS(P,O) annual cycle in the Southern Bight of the North Sea revealed a seasonality linked to the spring phytoplankton communities succession: (1) colonial diatoms (reappearing in autumn), (2) Chaetoceros spp., (3) P. globosa, (4) large-size summer diatoms (mainly Guinardia spp.), and (5) dinoflagellates. Spatial gradients of DMS(P) were related to those of phytoplankton biomass, itself related to the inputs of nutrients from the Scheldt estuary. It also discharges suspended matter in which DMSO may have been produced by anaerobic oxidation of DMS. Laboratory measurements confirmed a large variability in DMSP cellular contents between the six studied diatoms (Nitzschia closterium, Skeletonema costatum, Thalassiosira rotula, Chaetoceros socialis, Chaetoceros debilis, and Guinardia delicatula), low producers in comparison with P. globosa and even more with Heterocapsa triquetra (Dinoflagellate). In particular, communities 2 and 4 have lower DMSP cellular contents than community 1 (N. closterium, S. costatum and T. rotula). Senescence induces a decrease in DMSP/DMSO suggesting an oxidative stress caused by nutrients and/or light limitation in DMSP producers. In S. costatum, DMSP seems to play an osmoregulatory role and is oxidised into DMSO in hyposaline conditions. In P. globosa and H. triquetra, an oxidative stress appears in hypo- and hypersaline conditions diverging from their salinity optimum. [less ▲]

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See detailUse of Soil and Litter Arthropods as Biological Indicators of Soil Quality in Southern Rwanda
Nsengimana, Venuste ULiege

Doctoral thesis (2018)

Abstract - Nsengimana Venuste (2018). Use of soil and litter arthropods as biological indicators of soil quality in Southern Rwanda. University of Liège, Gembloux Agro Biotech. Pages: 121, tables: 13 ... [more ▼]

Abstract - Nsengimana Venuste (2018). Use of soil and litter arthropods as biological indicators of soil quality in Southern Rwanda. University of Liège, Gembloux Agro Biotech. Pages: 121, tables: 13, figures: 3 To assess soil quality under different land uses by the use of soil and litter arthropods as biological indicators, a research was conducted in the Arboretum of Ruhande and the Rubona agricultural research station in southern Rwanda. Soil and litter arthropods were collected by pitfall sampling technique and identified to the family level. Ants (Hymenoptera: Formicidae) were identified to species level. Soil cores were collected and analysed for soil organic carbon, total nitrogen, available phosphorus, pH, aggregate stability, cation exchange capacity, electrical conductivity, silt, and clay and sand soil textures. C:N ratios were calculated from the mass of carbon to the mass of nitrogen. Higher levels of total nitrogen, soil organic carbon, and clay and silt soil texture were found in native and exotic tree species. Higher levels of cation exchange capacity, pH, and electrical conductivity were found in native tree species and banana plantations, while higher levels of available phosphorus, aggregate stability and sand soil texture were found in coffee and banana plantations. The analysis of the abundance of collected soil and litter arthropods indicated higher abundance of the most of identified families in native and exotic tree species than in the varieties of coffee and banana plantations. Families of Scolopendridae, Trombiculidae, Eosentomidae, Formicidae and Staphylinidae showed strong correlation with soil physicochemical properties. Formicidae highly occurred in all land uses and discriminated between clay, sand, aggregate stability, pH, available phosphorus, electrical conductivity and cation exchange capacity. The ecological functions of identified families contribute to the soil quality through predation, decomposition, bioturbation and phytophagous that increase soil organic matter and facilitate water retention and soil aeration. The taxonomy of ants to species level indicated 30 species belonging to 14 genera, and four subfamilies, the Formicinae, Dorylinae, Myrmicinae and Ponerinae. These species correlated with soil properties in different ways, but their ecological functions that contribute to soil quality are not yet well documented. We recommend further studies to be replicated in other land uses and ecological zones of Rwanda, to include the impact of climate variability, altitudinal variation, functional diversity, metal and soil microbiology and the taxonomy of the entire community composition of collected soil and litter arthropods to species level in order to generalize these findings. Key words: Community composition, Doryllinae, Formicinae, Myrmicinae, Ponerinae, land use, physicochemical parameters [less ▲]

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See detailAnalyse des risques environnementaux liés aux pratiques phytosanitaires dans les écosystèmes aquatiques du bassin cotonnier (Nord Bénin)
Gouda, Abdoul-Ibrachi ULiege

Doctoral thesis (2018)

In Benin, the cotton sector occupies a preponderant place in the national economy. Its production is confronted with attacks from pests and diseases causing losses of 50 to 70%. In the absence of ... [more ▼]

In Benin, the cotton sector occupies a preponderant place in the national economy. Its production is confronted with attacks from pests and diseases causing losses of 50 to 70%. In the absence of sustainable alternatives, the use of plant protection products (PPPs) is widespread and poorly regulated. A survey of 150 cotton farmers on phytosanitary practices shows that only 19% of PPPs are registered in Benin for cotton. 75% of producers have not received any instruction and 5% have received training on treatments. As a result, 75% of operators overdose insecticides, 80% do not protect themselves and empty packaging is abandoned or sometimes used for domestic purposes. Scenarios based on the observations have made it possible to estimate that the potential exposure of producers significantly exceeds the AOEL values for all the active substances identified, sometimes by more than 50 times. Using a tracer (tartrazine), the drift generated by a backpack device and a centrifugal rod was quantified under identical weather conditions. The results show that a higher spraying height and the use of a centrifugal spray can generate significantly higher drift percentages. The quantities transferred by air to the water reservoirs are small and the droplets disperse up to a distance of 16 m regardless of the device used. Using cotton plot collectors and water retention sampling, the transfer of pesticides by runoff was quantified after several rainfall events during the 2016-2017 season. The results indicate the systematic presence of acetamiprid (mainly in the aqueous phase) and chlorpyrifos (mainly on sediments), which is explained by their solubility and adsorption to soil particles. However, the results also indicate that the quantities transferred by runoff are low and depend on rainfall, environmental characteristics (slope, soil cover and structure) and certain phytosanitary or cultural practices. At concentrations observed in the receiving environment, the ecotoxicological risk of acetamiprid would be negligible (IRE = 4) to aquatic organisms, earthworms and birds. However, chlorpyrifos concentrations in the environment could be harmful to these organisms (IRE = 272). To remedy this situation, actions to develop the surroundings of water reservoirs and to raise producers' awareness of good phytosanitary practices are necessary. [less ▲]

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See detailEvaluation de l’impact des antibiotiques et des pesticides utilisés en élevage et en agriculture sur la qualité sanitaire de la viande bovine consommée au Nord-Est du Bénin
Dognon, Sèmanou Robert ULiege

Doctoral thesis (2018)

The presence of antibiotic and pesticide residues in food can cause health problems for consumers. However, no study has quantified residues of veterinary antibiotics and pesticides in meat of cattle ... [more ▼]

The presence of antibiotic and pesticide residues in food can cause health problems for consumers. However, no study has quantified residues of veterinary antibiotics and pesticides in meat of cattle massively bred in North Benin. This is why the overall objective of this thesis is to evaluate the impact of the use of veterinary antibiotics and pesticides on the safety of cattle meat consumed in North-East of Benin. The first chapter is a compilation of three review papers that were titled, respectively: “production, importation and quality of meat consumed in Benin”; “quality of veterinary antibiotics used in West Africa and methods for detecting of their residues in foodstuffs” and “review on the modes of action, impacts and detection of pesticides used in agriculture”. In chapter 2, a survey was first conducted among 98 farmers in the communes of Banikoara, Kandi, Bembereke and Kalale located in North-East of Benin. This first study showed that the antibiotics used in cattle breeding belonged to the groups of tetracyclines, beta-lactams, sulphonamides, aminoglycosides and macrolides, which were used per 100; 88; 56; 44 and 35% of breeders, respectively, in the study area. Fifty-eight percents of these farmers bought these drugs in the illegal market, 57% of them practiced “self-medication” and 93% of them did not respect the withdrawal times for antibiotics before putting foodstuffs from treated animals on the market. These risky practices led to the contamination of cattle meat with antibiotic residues, as was shown in the second study. The kidney and muscle tissues of 50 cattle carcasses from the Parakou city, in north-east of Benin, were samples to determine antibiotic residues (tetracyclines, beta-lactams and sulfonamides), using a semi-quantitative screening method adapted from the New Two Plates Test (NTPT) of Pham Kim et al. (2011). This modified NTPT showed that 60 % of the 50 carcasses analyzed contained residues of tetracyclines, beta-lactams and sulfonamides. Positive results were confirmed by liquid chromatography - mass spectrometry (LC-MS) analyzes. The maximum levels observed for oxytetracycline, epi-oxytetracycline, tetracycline and epi-tetracycline residues in the kidney were 1380, 350, 190 and 230 μg kg-1, respectively. In one of the bovine carcasses, very high levels of sulfamethazine residues were found: 3900 μg kg-1 in the kidney and 2220 μg kg-1 in the muscle. Overall, 38 % of the carcasses submitted to confirmation analyzes by LC-MS showed antibiotic residue levels that exceeded the maximum residue limits (MRLs) applied in the European legislation. The modified NTPT method was then used to evaluate the quality of veterinary antibiotic drugs used in cattle breeding in the study area. The results of this third study showed that the 28 products tested contained the active ingredient as indicated on the drug labels. However, quantitatively, only 61 % of these drugs contained active substance at levels ranging from 90 to 120 %, 90-115 % and ≥ 90 % of the concentrations mentioned on the labels (for oxytetracycline, penicillin G and tylosin drugs, respectively), and could therefore be declared compliant with the requirements of USP (United States Pharmacopeia). The results of the studies reported in this chapter 2 have shown that veterinary practices, resulting in the presence of residues in the meat, and the poor quality of veterinary antibiotics could promote the development of bacterial resistance to antibiotics in the study area. Chapter 3 presents the results of studies 4 and 5. The inventory realized in study 4 showed that 56 commercial pesticides (including 21 herbicides and 35 insecticides) were used in agriculture in the study area. As regards the active ingredients contained in these products, 13 were herbicides and 14 were insecticides. Seventy-eight percents of farmers bought these pesticides both in the illegal circuit and in the official agricultural inputs selling structures. Only 53 % of these farmers knew the instructions for use of these dangerous products. These practices have led to the contamination of natural ecosystems and the food chain with pesticide residues. Indeed, study 5 revealed traces of glyphosate residues in pasture waters. In addition, three of 25 cattle carcasses that samples were subjected to the analyzes by gas chromatography - mass spectrometry, were contaminated with insecticide residues such as beta-endosulfan (98.6-139.5 μg kg-1) and dichlorodiphenyldichloroethylene (DDE) (4.6 μg kg-1). Overall, only beta-endosulfan found in two carcasses showed concentrations above the MRL established by European Regulation (EC) 396/2005. Finally, chapter 4 presents a general discussion of the results obtained in the five studies. As a general conclusion and recommendation, it can be said that all the veterinary and agricultural practices as described in studies 1 and 4 clearly impact the safety of cattle meat consumed in North-East of Benin, and the results of these studies are benchmarks for future monitoring of the food chain in Benin. [less ▲]

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See detailAnticancer Effects of Soybean Bioactive Components and Anti-inflammatory Activities of the Soybean Peptide Lunasin
Zhu, Yingying ULiege

Doctoral thesis (2018)

Soybean products have been demonstrated to have health-promoting benefits. In this study, we investigated the anticancer effect of 12 bioactive components from soybean on human breast cancer cells in ... [more ▼]

Soybean products have been demonstrated to have health-promoting benefits. In this study, we investigated the anticancer effect of 12 bioactive components from soybean on human breast cancer cells in vitro. Results showed that genistein, daidzein, glycitein, genistin and dainzin showed stronger anti-proliferative activity against MCF-7 cells with median effective concentration (EC50) values of 66.98±4.87 μM, 130.14±2.10 μM, 190.67±5.65 μM, 72.82±2.66 μM and 179.21±6.37 μM, respectively. There was a synergistic effect of combination treatment of genistin plus daidzin in MCF-7 cells with combination index at inhibition of 50% (CI50) of 0.89±0.12. Genistein, glycitein, genistin and β-sitosterol were demonstrated to have a stronger anti-proliferative activity against MDA-MB-231 cells with EC50 values of 93.75±5.15 μM, 142.67±5.88 μM, 127.82±4.70 μM and 196.28±4.45 μM. The synergistic effect was observed in the mixture of genistein plus genistin, genistein plus β-sitosterol or β-sitosterol plus genistin with CI50 values of 0.56±0.13, 0.54±0.20 and 0.45±0.12, respectively. These bioactive components were able to inhibit invasion and migration in breast cancer cells and the combination treatments enhanced the inhibitory effect. Regulation of PI3K/Akt/mTOR pathway seems to be the main mechanism involved in the anticancer activity. Among all the tested components from soybean, lunasin attracted our interests because that it is a novel peptide and many problems about lunasin remained to be studied. About lunasin, we were concerned about its anti-inflammatory activity and involved signalling pathways, as well as its production using genetic engineering method. In this study, we isolated natural lunasin (N-lunasin) from soybean and expressed recombinant lunasin (R-lunasin) from Pichia (P.) pastoris. The expression level of R-lunasin reached 240 mg/L cell-free broth at the optimum condition (initial pH 7.0, 1.0% final methanol concentration and induction for 72 h at 26 °C). The anti-inflammatory activity of N-lunasin and R-lunasin was accessed and compared. Results showed that there was a comparable effect of N-lunsin and R-lunasin on inhibition of release of nitric oxide (NO), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in a dose-dependent manner. In addition, intracellular signalling array analysis demonstrated down-regulated levels of phosphorylated Akt, mechanistic target of rapamycin (mTOR) and p70 s6 kinase (p70s6k) and an up-regulated level of glycogen synthase kinase-3β (GSK-3β) after R-lunasin treatment. These results suggest that lunasin exerted anti-inflammatory activity in LPS-stimulated RAW264.7 cells partly via inhibiting the activation of Akt/mTOR/p70s6k signalling pathway. Soybean is widely cultivated from north China to south China. We were also interested in the variation in lunasin content in soybean seeds. In this study, we determined the lunasin content in a total of 413 soybean samples that were collected from four major regions in China and harvested in 2014 and 2015 to reveal the regional distribution of soybean lunasin content in China and the effects of climate factors. The results showed that the cultivar Changmidou 30 collected from Jilin province and harvested in 2015 had the highest lunasin content (3.25 mg/g dry seeds). The data from both 2014 and 2015 showed that the lunasin content in soybean collected from north China was significantly higher (p<0.05) than that from south China. There was a positive correlation (p<0.01) between lunasin content and hours of sunshine (HS) as well as diurnal temperature range (DTR); however, there was a negative correlation (p<0.01) between the lunasin content and rainfall (RF). In addition, the combined analysis of data from 2014 and 2015 demonstrated that DTR was the dominant factor that affects the lunasin content with a direct path-coefficient of 0.301. These results generated from our study are anticipated to improve our knowledge of bioactive components in soybean as well as their bioactivities. [less ▲]

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See detailStudy of the birth, the growth and the life of a dynamical cluster under microgravity conditions
Noirhomme, Martial ULiege

Doctoral thesis (2018)

Granular materials can produce spectacular phenomena due to the dissipation that occurs when the grains collide. In microgravity environments, a granular material can adopt different behaviors, mainly ... [more ▼]

Granular materials can produce spectacular phenomena due to the dissipation that occurs when the grains collide. In microgravity environments, a granular material can adopt different behaviors, mainly depending on the packing fraction of the system and the intensity of the energy that is injected into the system. By regulating the packing fraction, a granular gas or a dense and slow aggregate can be observed. These aggregates are called "clusters" and their emergence has been studied both theoretically and numerically in the last decades. In addition, the parameters triggering the gas-cluster transition were highlighted during these studies. Nevertheless, these theoretical and numerical considerations have never been verified experimentally and the cluster, which always coexist with granular gases in the case of excited systems, requires still a lot of attention. That's why the SpaceGrains project has been launched by the European Space Agency (ESA). This project contributes to the study of granular phenomena in microgravity thanks to the development of the VIP-Gran-PF instrument, containing of a cell in which bronze beads can be excited by two oscillating pistons. The cell can be quasi-two or three dimensional. The instrument was developed for parabolic flights and the first part of this work has consisted in verifying experimentally the gas-cluster transition and to observe some dynamics which have been predicted by numerical simulations. These simulations constitute the second part of our work. Perfect knowledge of the capabilities and performance of the VIP-Gran-PF instrument as well as advanced training were required before starting to use it in parabolic flights. Our experimental work began with the study of the instrument itself. Once the handling of the VIP-Gran-PF device acquired, we focused on several topics. The first concerned the experimental verification of the gas-cluster transition. This study required a large number of parabolic flight campaigns (5 to be exact) since it was necessary to explore an entire phase diagram, that was derived from numerical simulations. Granular gases and clusters, as well as an unexpected "bouncing aggregate" regime, have been observed during these campaigns. By developing an original image processing, we have been able to reconstruct the distributions of the three dimensional positions of the particles in the VIP-Gran cell on the basis of two dimensional pictures. Adapting an existing model, we also predicted the possibility of emergence of the "bouncing aggregate" regime. In parallel with this study, we performed numerical simulations in order to determine the mechanism of birth and growth of clusters within the instrument. By sorting the grains as gaseous or clustered with a local criterion, we have discovered that the cluster was born in the corners near the lateral walls of the cell, as far as possible from the oscillating pistons. We also show that the cluster grows because the gas has to keep a critical packing fraction. Other numerical simulations allowed us to identify a specific dynamic of the cluster. By asymmetrically exciting the particles, it is possible to displace the position of the center of mass of the system. Moreover, a natural oscillation of the cluster, linked to its size, the asymmetry and the driving frequency, has been highlighted. Finally, we were interested in the structure of clusters in the case of a mixture of two different types of particles. As a function of their difference in mass and/or in volume, we showed that different structures are observed and that a phase segregation could take place in the system. Finally, we realized experiments in order to validate all of our numerical simulations, except for the growth of the clusters, which is impossible to observe in the current configuration of the VIP-Gran-PF instrument. We also investigated the clustering of elongated particles, the behavior of intruders in a granular gas, such granular osmosis by using a semi permeable wall and the behavior of a mobile wall placed in between both pistons. At this point, the data of these studies still has to be analyzed. [less ▲]

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See detailOn the Fluid Mechanics of Self-Aeration in Open Channel Flows
Valero Huerta, Daniel ULiege

Doctoral thesis (2018)

This dissertation is organized in five parts. Part I is made of four chapters which aim to introduce this dissertation and put it in the context of past developments. In Chapter 1, a historic analysis of ... [more ▼]

This dissertation is organized in five parts. Part I is made of four chapters which aim to introduce this dissertation and put it in the context of past developments. In Chapter 1, a historic analysis of air-water flows research in open channel flows is presented, jointly with a detailed discussion on research trends. Besides, aims and scope of this dissertation are clearly defined. Chapter 2 focuses on fundamental studies directly dealing with self-aeration, Chapter 3 deals with experimental studies on the self-aeration onset determination and Chapter 4 examines past attempts on numerical modelling of air-water flows. Part II describes the non-aerated region, which is of interest for the subsequent chapters. This part is intentionally divided into two chapters as to highlight the relevance of a commonly forgotten aspect: the free surface. Thereby, Chapter 5 deals with the water and air phases in the non-aerated flow region of spillways, whereas Chapter 6 is entirely dedicated to conceptualize the free surface. Main hypotheses related to the upcoming analytical derivations are also examined in Chapter 6. Part III is the kernel of this dissertation and is divided into two chapters. The first one, Chapter 7, is dedicated to the mathematical derivations related to the equations governing the turbulent motion of a free surface. The main result of Chapter 7 is a kinematic and a dynamic equation that, together, yield a non-linear second-order differential equation describing the growth of the free surface perturbations. 8 aims to approximate, as accurately as possible, the forces acting over a free surface perturbation. The equations obtained in Chapters 7 and 8 allow computation of the growth rates for each wavelength, the free surface fluctuations spectra and the perturbations steepness. Part IV is composed of two chapters. Chapter 9 presents an application where capabilities of the derived equations are brought to light by means of a prototype scale application. Chapter 10 focuses on some empirical evidences obtained at a large-scale stepped spillway model. Perturbations growth is predicted by the developed theoretical model. Furthermore, it is shown that the free surface turbulent structure agrees, for the biggest wavelengths (gravitational dominated wavelengths), with that predicted by the mathematical analysis up to around 30 % of the non-aerated region length. Downstream, the energy distribution of these wavelengths starts changing. Notwithstanding that, the free surface structure at smaller wavelengths (surface tension dominated wavelengths) holds valid up to the inception point location. Further evidences also point in the direction of a breaking steepness as an appropriate parameter for self-aeration characterization. Part V contains a single chapter. This last chapter brings closure to this thesis and offers a discussion on the most relevant achievements and limitations of this doctoral work, together with an outlook into the future research challenges to be addressed. In summation, this investigation has provided with a fluid mechanics description of the self-aeration onset while demonstrating that it is the result of a new type of two-phase flow instability. [less ▲]

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See detailRôle de la banque de graines du sol dans la régénération des forêts denses humides d’Afrique centrale
Douh, Chauvelin ULiege

Doctoral thesis (2018)

La présente thèse s’intéresse aux moteurs de la régénération des forêts denses humides tropicales d’Afrique, plus particulièrement au rôle joué par la banque de graines du sol dans cette régénération ... [more ▼]

La présente thèse s’intéresse aux moteurs de la régénération des forêts denses humides tropicales d’Afrique, plus particulièrement au rôle joué par la banque de graines du sol dans cette régénération. Plus spécifiquement, l’étude vise à : (i) évaluer l’abondance et la composition floristique de la banque de graines du sol de deux types de forêt reposant sur des sols différents ; (ii) quantifier l’abondance de la banque de graines du sol d’une essence commerciale importante, le tali (Erythrophleum suaveolens) et étudier les facteurs intervenant dans la levée de dormance de ses graines ; (iii) évaluer la capacité du système d’imagerie hyperspectrale proche infrarouge à discriminer des graines de deux espèces soeurs, E. suaveolens et E. ivorense. Les résultats montrent que la densité et la composition floristique de la banque de graines du sol varient significativement selon les types de forêt et de sol. Les taxons pionniers sont largement majoritaires dans les deux cas, mais sont mieux représentés dans la banque du sol de la forêt à Celtis (vieille forêt secondaire) que dans le sol de la forêt à Manilkara (forêt mature). Tous taxons confondus, la similarité floristique entre la banque de graines du sol et la végétation environnante est relativement faible quel que soit le type forestier. Cependant, cette similarité s’avère nettement plus importante en ne considérant que les taxons pionniers. Seulement trois espèces de bois d’oeuvre ont été observées dans la banque du sol : Nauclea diderrichii, Staudtia kamerunensis et Erythrophleum suaveolens. E. suaveolens, le tali, est une des espèces les plus exploitées d’Afrique centrale. L’évaluation de l’abondance des graines de l’espèce au sein des deux types de forêt révèle une densité plus élevée en forêt à Celtis qu’en forêt à Manilkara, où les graines sont quasi inexistantes bien que les densités d’arbres en âge de reproduction ainsi que les structures diamétriques, soient similaires entre sites. Différentes hypothèses ont été émises pour expliquer ce résultat, la plus probable étant liée à la strcuture de végétation différente entre les sites. Les canopées des individus vivant dans la forêt à Manilkara seraient davantage dominées et fructifieraient moins fréquemment que dans la forêt à Celtis. La longévité des graines étudiées par spectroscopie de masse par accélérateur révèle que ces semences de tali, viables et enfouies dans le sol, seraient âgées d’environ dix ans. Le système d’imagerie hyperspectrale proche infrarouge s’est avéré efficace dans la distinction des graines d’E. suaveolens et E. ivorense, ce qui ouvre d’intéressantes perspectives quant à l’utilisation de cette technique pour étudier la banque de graines du sol. [less ▲]

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See detailCase of a hydraulic splashing nozzle: Effect of the disk geometry on the sheet breakup
Ouled Taleb Salah, Sofiene ULiege

Doctoral thesis (2018)

In the agricultural field, conventional farmers use Plant Protection Products (PPP) to control crop enemies as for instance weeds, diseases and pests. In practice, PPP application techniques are based on ... [more ▼]

In the agricultural field, conventional farmers use Plant Protection Products (PPP) to control crop enemies as for instance weeds, diseases and pests. In practice, PPP application techniques are based on droplet clouds to carry the spray mixture containing the active ingredient and the adjuvant to the surface target. The PPP application efficiency consists in maximizing the deposition of the mixture on the target while reducing the environmental losses. However, the droplet characteristics within the spray affect drastically the treatment efficiency. For instance, small droplets (< 200 µm) are prone to drift while big droplets (> 300 µm) have the tendency to splash on a specific target surface. The widely used agricultural nozzles produce a liquid sheet that disintegrates into ligaments leading to droplets with various diameters and velocities. Hence, the generated spray is characterized by a wide droplet size distribution (RSF = 1) resulting in potential drifting or efficiency losses due to splashing phenomena. The spray must deliver an optimal droplet distribution in term of diameters and velocities by reducing the extent of the droplet size distribution. The design of new agricultural nozzles is a challenge for the practitioners in the field of agricultural nozzles. As the simplicity, the robustness, the low cost and the high flow rate ranges are required for the agronomic application, the Savart configuration namely a round jet impacting vertically a motionless disk is the ideal candidate for the massive production of droplets. The Savart sheet develops in the air (outside the disk) and it results in random breakup leading to wide droplet size distribution as in the case in hydraulic nozzles. As the used flow ranges are high in the PPP application, the obtained sheet on the disk is turbulent. The challenge is to tame the turbulent sheet. I propose to split the sheet into individual jets using textured disks by acting on the semi-free film or by inserting the right structures directly in the free sheet. Then, the jets break up according the Plateau-Rayleigh mechanism and lead to a narrower droplet size distribution. Therefore, this thesis aims to study experimentally the effect of the disk geometry on the sheet break up. This study is seen as a practical guide for specialists in fluid mechanics who desire developing the generation of drops with controlled sizes. One firstly detailed the experimental setup based on the impact of a turbulent jet on a non-textured disk. The disk configuration constitutes our reference case to which results on textured disks are to be confronted. The sheet was characterized through several parameters: The mean velocity U, the mean thickness h and the ejection angle φ that depends on the disk geometry and on the flow rate Q. As the jet flow is turbulent at the impact, local disturbances in the film triggered downstream the disk edge the appearance of random holes at a distance R′ (from the jet axis) in the liquid sheet. These holes lead to the disintegration of the sheet into droplets. Furthermore, the produced droplets are characterized in term of diameters. The droplet size distribution is clearly wide (RSF values are close to 1) that is similar to the case of hydraulic nozzles. Moreover, one perturbed the semi-free film evolving on the disk surface. The case of a turbulent round water jet impacting a disk engraved along its circumference by a number N of radial grooves is addressed. By the insertion of grooves, one controls the turbulent flow and the film splits into a number n of liquid jets before reaching the disk edge. The phase diagrams presented as a function of the inside gap between grooves d1 and the flow rate Q illustrate the transition between jet regimes. Droplets were characterized in term of their diameters and velocities. For all configurations including an engraved disk, the obtained droplet size distribution is narrower compared to the ungraved disk and to the standard flat fan nozzle Teejet TP 65 15. The V50 is reduced towards smaller droplets in the case of the engraved disk configurations but it is still coarse compared to that of the Teejet nozzle. Furthermore, one perturbed directly the Savart sheet, i.e. the free sheet evolves in the air. A number N of triangular prisms are set in the sheet at a radial distance r from the jet axis. This radial distance is strictly greater than D/2 (D = disk diameter) and less than or equal to R’ (for which the holes appear in the sheet). Once the number of prisms and the distance from the injector is fixed, the geometry is determined by the size of the prism and the distance b between two successive prisms. When increasing the flow rate Q, the jet numbers are n = 0, n = N and n = N* (elastic coalescence of jets) for large Q. One used a geometrical model that explains the generation of individual jets through these structures. Then, the emitted droplets are characterized in term of diameters and velocities. The droplet size distribution is narrower compared to the non-textured disk and the hydraulic nozzle TP 65 15 with the same spray class. The V50 decreased by decreasing the external gap b between two neighboring textures at the same radial distance r from the jet axis. Also, the V50 decreased by increasing the radial distance from the jet axis as the sheet thickness decreases. However, we are limited by R’ due to holes appearances. Finally, one concludes on the fundamental findings and on the role that the developed nozzle could play in applications. Also, one proposed some original perspectives to the present thesis such as testing the triangular prism textures in the case of the liquid sheet produced by a standard hydraulic nozzle. [less ▲]

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See detailLa cécidomyie orange du blé, Sitodiplosis mosellana (Géhin) : amélioration des stratégies de lutte et gestion intégrée
Chavalle, Sandrine ULiege

Doctoral thesis (2018)

La cécidomyie orange du blé, Sitodiplosis mosellana (Géhin) (Diptera : Cecidomyiidae), est un ravageur important du blé. Ses larves se nourrissent aux dépens des grains en formation pouvant causer ... [more ▼]

La cécidomyie orange du blé, Sitodiplosis mosellana (Géhin) (Diptera : Cecidomyiidae), est un ravageur important du blé. Ses larves se nourrissent aux dépens des grains en formation pouvant causer d’importantes pertes de rendement et de qualité de la récolte. Présente dans tout l’hémisphère nord, cette espèce univoltine a occasionné d’importants dégâts aux cours des trente dernières années. En Belgique, elle est actuellement reconnue comme le ravageur principal du blé. Bien qu’il soit connu depuis près de deux siècles, le contrôle de ce ravageur reste difficile en raison de son comportement discret et de ses populations fortement variables en fonction du champ, de la localisation et de l’année. Une gestion intégrée de S. mosellana afin de limiter ses populations et ses dégâts est donc indispensable. C’est dans ce contexte que s’inscrit cette thèse qui a pour objectif d’améliorer les stratégies de lutte contre le ravageur. Après une revue bibliographique axée principalement sur les connaissances relatives à la biologie de l’insecte et sur les stratégies de lutte existantes contre ce ravageur, plusieurs études touchant différents aspects de la lutte intégrée ont été réalisées afin de répondre à notre objectif. Le risque de dégâts de S. mosellana est essentiellement conditionné par la coïncidence entre la présence d’adultes et la phase sensible des blés. Cette fenêtre de vulnérabilité des blés ne durant qu’une dizaine de jours, la prévision des émergences du ravageur constitue l’élément clé dans l’estimation des risques et dans l’élaboration de sa lutte. Sur base de l’analyse de la phénologie de leurs émergences et des conditions météorologiques, les facteurs induisant le déclenchement des émergences ont été déterminés et un modèle prévisionnel des émergences de S. mosellana a été établi pour la Belgique. Afin de détecter et de quantifier les adultes émergés, les pièges constituent un outil très utile. Plusieurs types de pièges disposés à différentes hauteurs par rapport au sol ont été testés afin d’améliorer l’efficacité de capture de S. mosellana et de son parasitoïde principal, Macroglenes penetrans. Les pièges les plus efficaces ont été le piège à phéromone positionné à 0,2 m pour S. mosellana, et pour M. penetrans le piège cuvette jaune et le piège collant positionné à 0,6 m. Par ailleurs, il a été constaté que l’ajout d’un leurre de phéromone d’Haplodiplosis mariginata, une autre cécidomyie des céréales, dans un piège équipé d’un leurre de phéromone de S. mosellana diminuait drastiquement l’efficacité de capture de S. mosellana. Lorsque des adultes sont détectés durant la phase sensible du blé, un contrôle chimique du ravageur peut être nécessaire. Différents traitements insecticides ont été évalués quant à leur efficacité de protection de variétés de froment sensibles et résistantes. Il a été démontré, qu’en cas d’attaque sévère de S. mosellana, un traitement insecticide bien positionné pouvait protéger le blé contre ce ravageur en conduisant à une augmentation significative des rendements, et que même les variétés résistantes pouvaient valoriser un tel traitement. Une relation non-linéaire entre la perte de rendement et le nombre de larves par épis a également été mise en évidence. L’effet toxique de plusieurs fongicides sur les adultes induisant des taux de mortalités significatifs a été révélé par un essai au champ et au laboratoire. Outre les traitements insecticides, la culture de variétés résistantes constitue l’autre stratégie de lutte contre S. mosellana. La détermination des variétés résistantes est donc essentielle. Dans cette optique, une méthode de phénotypage en conditions semi-contrôlées a été mise au point. Cette méthode permet d'évaluer très simplement un grand nombre de variétés de manière fiable. Par ailleurs, le rôle des parasitoïdes comme agents de régulation des populations de S. mosellana a été étudié. Le complexe parasitaire de S. mosellana présent en Belgique a été identifié et s’est révélé spécifique. Huit espèces appartenant à deux familles d’hyménoptères (Pteromalidae et Platygastridae) parasitent S. mosellana. Les taux de parasitisme ont fortement varié en fonction du site, allant de 3 à 100 %. La phénologie des trois principaux parasitoïdes a été comparée à celle de leur hôte. Il a été démontré que les émergences de M. penetrans étaient étroitement synchronisées avec celles de son hôte et induites par les mêmes pluies inductrices, contrairement à E. error et P. tuberosula. Perfectionnement du modèle prévisionnel des émergences, mise en évidence d’interférences entre les phéromones de deux cécidomyies proches, mesure de l’effet de traitements insecticides mais aussi fongicides, conception d’une méthode de phénotypage des variétés de blé quant à la résistance à S. mosellana, identification du complexe des parasitoïdes, mesure des taux de parasitisme : par différents apports aux connaissances et mise au point technique, la présente thèse permet aux scientifiques et aux acteurs de terrain de mieux appréhender le problème agronomique que pose la cécidomyie orange du blé, et de gérer les populations de ce ravageur dans le respect du concept de lutte intégrée. [less ▲]

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See detailTransformation of CO2 into high performance polyhydroxyurethane adhesives and coatings
Panchireddy, Satyannarayana ULiege

Doctoral thesis (2018)

Today, adhesive bonding is a widespread technology many fields including automotive, aeronautic, surgery, packaging, electronic devices or in the building sector. It enables designing novel (lightweight ... [more ▼]

Today, adhesive bonding is a widespread technology many fields including automotive, aeronautic, surgery, packaging, electronic devices or in the building sector. It enables designing novel (lightweight) materials/products with performances comparable to the ones of systems fixed by mechanical adhesion. Glues, adhesives exist as a large variety of compositions such as cyanoacrylates (superglue ®), (meth)acrylate or epoxy resins, polyesters, polyurethanes… that fit on-demand to the specificity of the glued assembly (nature of the substrate, the thermo- mechanical performances, the resistance against water, acids, bases or solvents…). Due to their easy tunable and versatile properties (soft and flexible to rigid materials, high bonding adhesion, compatibility with numerous substrates…) polyurethanes (PUs) are reference systems. PUs are produced from toxic isocyanates that cause severe health concerns (asthma, skin irritation, DNA mutation). To surpass these issues, the quest for novel isocyanate-free PUs glues and adhesives formulations is essential. This thesis responds to this current trend which aims to develop well-designed innovative sustainable PU adhesives (and coatings) free of isocyanates. It explores the potential of poly(hydroxyurethane)s (PHU) made by step-growth polymerization of CO2-sourced bis- or multi-functional cyclic carbonates with di- or polyamines to construct novel PU glues/adhesives for various substrates (metals, wood, glass, plastics). Three main research axes were investigated and focused i) on the establishment of solvent-free petro-based PHU formulations and their corresponding nanocomposites thermoset PHUs (native or functional silica or ZnO fillers) to tailor high performance adhesives for various substrates; ii) on the increase of the sustainability of the PHU nanocomposites glues by incorporation of renewable monomers (vegetable oils) within the formulations and iii) the development of biomimetic PHU glues inspired from mussels (incorporation of dopamine). All formulations were benchmarked with commercial Terpmix-6700 and Araldite®2000 PU glues and results highlight that these PHU glues represent promising and competitive alternatives to conventional PU glues prepared from the toxic isocyanate chemistry. We believe that this work opens a realistic route to the next generation of PU adhesives. [less ▲]

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See detailChangements cérébraux après réadaptation cognitive dans la maladie d'Alzheimer
KURTH, Sophie ULiege

Doctoral thesis (2018)

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See detailDéveloppement d'un outil de simulation et d'analyse technico-économique et environnementale d'un réseau de chaleur
Sartor, Kevin ULiege

Doctoral thesis (2018)

The first part of this doctoral thesis is composed of 6 chapters. Chapter 1 summarizes the different contexts in which the research work takes place. The global energy context for primary energy ... [more ▼]

The first part of this doctoral thesis is composed of 6 chapters. Chapter 1 summarizes the different contexts in which the research work takes place. The global energy context for primary energy consumption related to heating and cooling buildings is firstly detailed. Indeed, this work focuses on the supply of buildings through district heating networks which are then detailed. To feed these district heating networks, the use of biomass and cogeneration units are also discussed in this first chapter. Chapter 2 presents the case study used to test the methodology developed in the research work. Using its specifications and the concepts introduced in chapter 1, general objectives are defined. Chapter 3 delineates the objectives of this research work on the basis of those set out in chapter 2. To achieve this, the different methods used are detailed and referenced through the scientific articles constituting the part 2 of this manuscript. Finally, the computer tools used to achieve these objectives are also briefly discussed. Chapter 4 presents the results of scientific articles 3, 4 and 8 of the part 2 of this manuscript concerning thermal energy transport modeling. Article 3, based on the limitations observed for a modeling method (finite volumes) commonly used for thermal energy transport modeling, details an alternative method of thermal energy transport simulation in the Matlab software language. This method considers not only the heat losses to the pipe environment but also the thermal inertia of the pipe whose influence on energy transport is demonstrated. Article 4 validates this approach experimentally in a laboratory test bench and on a portion of a heating network pipe of the case study. Article 8 establishes a state of the art of the different thermal energy transport modelling methods which concludes on the requirement to use an alternative method for the dynamic estimation of heat losses and thermal energy transport of a pipeline. This article proposes to use the method envisaged in article 3 by adapting it to the Modelica language. Furthermore, this alternative method is validated on the laboratory installation used in the experimental validation of article 4 as well as a portion of an existing heating network consisting of several consumers. Chapter 5 presents the results obtained for the analysis of a heating network, which are summarized in the scientific articles numbered 1, 2, 5, 6, 7 and 9 in part 2 of this manuscript, and supplements are also discussed where required. Article 1 presents a detailed modeling of biomass and natural gas combustion in order to estimate the emissions of several pollutants while focusing on the formation of nitrogen oxides. Article 2 presents a methodology to estimate the cost of heat and the carbon dioxide emissions balance of a heating network and compares this heating system with other alternative technologies. To achieve this objective, several models are detailed and validated experimentally in order to estimate the performances of the various installations constituting a heating network (boilers, cogeneration unit, heating network). Finally, several scenarios to improve the heating network and the cogeneration unit are considered and compared using the methodology developed. Article 6 and Article 7 consider alternative scenarios for reducing the cost of heating the heating network on the basis of the models developed in Article 2. Article 6 investigates the addition of thermal energy storage in order to maximize the use of a cogeneration unit feeding the heating network. Energy storage is considered in two forms: a hot water buffer storage tank placed close to the network and an adapted regulation allowing the use of the thermal inertia of the heating network. In addition, short-term and seasonal energy storage are considered to verify their relevance to the context of the heating network under study. On the basis of the results obtained, the subsidy policy linked to the use of the cogeneration unit is analyzed in order to determine its adequacy in the context of the case study. Article 7, for its part, envisages the addition of a high-temperature heat pump at a strategic point in the heating network that requires a hot water supply temperature to generate steam. This scenario is based on the assumption that by reducing the average temperature of the network thanks to this heat pump, it would be possible to limit the losses to the environment of the network and thus potentially to reduce the associated costs and the environmental footprint. Article 5 complements the analysis of heating networks by detailing a methodology to estimate the energy consumption and the energetic and environmental performances of different heating systems, including heating networks, in order to compare these solutions as a whole. Chapter 6 summarizes the findings of the research and offers perspectives for research. The second part of this doctoral thesis is composed of the scientific articles that were previously discussed and a section devoted to correct an error present in one of the scientific articles and to specify an aspect related to the cogeneration unit studied, namely the evolution of its rated power during the studies. [less ▲]

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See detailTopology optimization under static and fatigue failure constraints
Collet, Maxime ULiege

Doctoral thesis (2018)

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See detailMachine Learning for Landmark Detection in Biomedical Applications
Vandaele, Rémy ULiege

Doctoral thesis (2018)

Machine Learning aims at developing models able to accurately predict an output variable given the value of some input variables by using a dataset of observed (input, output) pairs. In the recent years ... [more ▼]

Machine Learning aims at developing models able to accurately predict an output variable given the value of some input variables by using a dataset of observed (input, output) pairs. In the recent years, the development of new Machine Learning algorithms as well as the increase of computing capabilities have made these methods very popular and successful to address various image processing related tasks. One of these tasks is landmark detection, which consists in finding the coordinates of one or several interest points in images. Landmark detection finds many applications in computer vision. In this thesis, we focus on two of them, both related to bioimaging. The first is morphometrics, where landmark coordinates are used to measure the size and the shape of body parts. The second is image registration, where the coordinates of the landmarks are used to compute the deformation between two images. During this thesis, we have developed an automated landmark detection algorithm combining tree-based machine learning models with multi-resolution pixel descriptors. Starting from an algorithm used for cephalometric landmark detection, we have progressively extended it in order to fit the needs of morphometric analyzes, where a wide variety of image datasets and body types are observed. We carefully analyzed the behavior of our algorithm in order to provide detailed insights about its performance on new image datasets. We then extended our landmark detection algorithm to 3D images and used it to perform CT-CBCT rigid registration. Finally, we studied the relevance of using post-processing steps based on the landmark shape structure given the specificities of biomedical applications. Throughout this work, we evaluated our method on four different datasets: three datasets concerning 2D morphometrics, and one concerning 3D image registration. On these datasets, we showed that our algorithm could reach state of the art performance while providing additional genericity regarding its application on datasets containing different types of images. [less ▲]

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See detailDeterminants and consequences of abnormal visual cortex responsiveness in migraine without aura
Lisicki Martinez, Marco ULiege

Doctoral thesis (2018)

La migraine est une maladie multifactorielle complexe, qui résulte de l'interaction entre une prédisposition génétique et un environnement facilitant. La majeure partie de l' information venant de notre ... [more ▼]

La migraine est une maladie multifactorielle complexe, qui résulte de l'interaction entre une prédisposition génétique et un environnement facilitant. La majeure partie de l' information venant de notre entourage nous atteint via le système visuel, ce qui fait de la vision la modalité sensorielle la plus développée chez l'Homme et celle qui met en jeu les aires cérébrales les plus tendues. Un faisceau de données cliniques et expérimentales a montré que les patients migraineux sont hyper-réactifs à la stimulation visuelle, mais les déterminants de ce phénomène restent méconnus. De plus, bien qu'étroitement associée à la migraine, l‟hyper-réactivité visuelle n'est ni suffisante, ni nécessaire pour développer la, maladie ce qui suggère l'existence de mécanismes physiopathologiques additionnels. Dans cette thèse nous avons analysé des facteurs environnementaux, métaboliques, anatomo-fonctionnels, et neurochimiques liés à la réactivité visuelle chez les migraineux, et la possible implication de leur interaction dans la pathogénie de la maladie. Pour ce faire, nous avons réalisé une série d‟études neurophysiologiques et de neuroimagerie qui explorent des aspects distincts de la physiologie du cerveau. Les résultats montrent que (1) une part de la variabilité interindividuelle de la réactivité visuelle peut être expliquée par des influences environnementales; (2) l‟hyper-réactivité visuelle dans la migraine est le résultat d'un déséquilibre complexe entre les mécanismes qui favorisent une perception renforcée, et ceux qui protègent contre une surcharge sensorielle; (3) la réserve métabolique au niveau cortical est insuffisante face à la demande énergétique accrue due à l'hyper-réactivité visuelle. Ces résultats illustrent la complexité des mécanismes responsables de l'hyperréactivité visuelle dans la migraine, améliorent notre compréhension de la physiopathologie de cette maladie, et ouvrent la voie à des axes de recherche innovants. [less ▲]

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See detailCharacterization, polymorphism and structuring properties of trisaturated triacylglycerols containing palmitic and stearic acids
Bhaggan, Krishnadath ULiege

Doctoral thesis (2018)

Pure tripalmitoylglycerol (PPP), 1,3-dipalmitoyl-2-stearoyl-sn-glycerol (PSP), 1-palmitoyl-2,3-distearoyl-sn-glycerol (PSS) were successfully synthesized according to a newly developed processing route ... [more ▼]

Pure tripalmitoylglycerol (PPP), 1,3-dipalmitoyl-2-stearoyl-sn-glycerol (PSP), 1-palmitoyl-2,3-distearoyl-sn-glycerol (PSS) were successfully synthesized according to a newly developed processing route. The kinetic phase behavior and phase transformation paths of these pure TAGs, binary and ternary mixtures thereof, were investigated at 10.0°C min-1 (fast cooling) and 1.0°C min-1 (slow cooling) cooling rates, and re-heating at 5.0°C min-1 and 1.0°C min-1 by differential scanning calorimetry and X-Ray diffraction. Polarized light microscopy was used to study the microstructure of different model application blends. At the higher cooling rate, all samples crystallized in α polymorph, while at the lower cooling rate, a different behavior was observed. For pure PPP, the most stable form obtained was the β-form, whereas for PSS and PSP, the most stable form achieved was the β′-form. In PPP-PSP binary mixture, samples containing XPSP ≤ 0.3 crystallized in the α-polymorph and samples containing XPSP ≥ 0.4 crystallized in the β′-polymorph. During heating all samples transformed to a more stable β′-form and melted finally in the β-form (XPSP ≤ 0.3) or in the β′-form (XPSP ≥ 0.4). Kinetic phase diagrams were constructed by using the melting and transformation peak temperatures from the DSC heating thermograms and XRD patterns and displayed an apparently typical eutectic behavior with a eutectic point at XPSP = 0.3, irrespective of the rate at which the samples were cooled and re-heated. The eutectic temperature was independent of the cooling and heating rates used. In PPP-PSS and PSS-PSP binary systems, all samples crystallized in the α-polymorph and transformed into the more stable β′-form via melt mediated crystallization or direct re-crystallization from the α-phase. In PSS-PSP, samples containing XPSP ≥ 0.5 tended to crystallize in the βʹ2-form and transformed during heating to the more stable βʹ1-form. In PPP-PSS, samples containing high PPP concentration ultimately transformed to the most stable β-form. The kinetic phase diagram of PPP-PSS mixtures displayed an apparently typical eutectic behavior with a eutectic point at XPSS = 0.3, when the samples were melted at the higher heating rate, which shifted to higher concentration, XPSS = 0.5, when the lower heating rate was applied. The eutectic temperature (~58.4°C) was independent of the cooling and heating rates used. The kinetic phase diagram of PSS-PSP mixtures displayed two types of behavior, a probable monotectic behavior in the most stable phase and a eutectic behavior in the meta-stable phase when the samples were melted at higher heating rate. To study the most stable form, samples were incubated at different temperature and incubation time. At lower incubation temperature (15°C), most stable forms were not obtained, whereas when stored at temperature close to the melting point (50°C) of the least stable polymorph, samples transformed to the most stable form, although for samples containing higher amount of PPP a mixture of polymorphs was observed. Different ternary blends were derived based on the composition of hydrogenated palm oil. These ternary blends showed similar phase behavior as was observed for the binary mixtures. For these blends, βʹ-form is desired for food application, but when the PPP content was high, the mixtures transformed to the β-form during incubation period. These results showed that samples having high PPP content are not suitable for use as hard stock fat for structuring purposes. Finally, three selected ternary systems were studied in model application blends, and showed different behavior based on the liquid fat used. It seemed that the presence of a high content of OOO facilitated the transformation to the more stable β-form. The microstructure of all the mixtures containing palm oleine (lower OOO content) as the liquid phase consisted of small spherulitic crystals, while the blend containing rapeseed oil (higher OOO content) as the liquid phase showed well-defined dendritic aggregations of crystallites. All samples formed a continuous network under these processing conditions. This study showed that mixed-acid TAGs (PSP and PSS) have a strong effect on the physical properties of the systems studied and dominated a large part of the phase behavior of the mixtures. At lower concentrations of these TAGs, the mixtures transformed to the most stable β-form, but at increasing PSP or PSS concentration, the mixtures stabilized in the β′-phase, which is preferred in many food application because this results in a smooth texture. [less ▲]

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See detailBiostimulant effects of rhizobacteria on wheat growth and nutrient uptake under contrasted N supplies
Nguyen, Minh Luan ULiege

Doctoral thesis (2018)

Plant growth-promoting rhizobacteria (PGPR) are increasingly used as microbial biostimulants. Hereby, the capacities of PGPR to promote plant growth and nutrient uptake in wheat were evaluated under with ... [more ▼]

Plant growth-promoting rhizobacteria (PGPR) are increasingly used as microbial biostimulants. Hereby, the capacities of PGPR to promote plant growth and nutrient uptake in wheat were evaluated under with contrasted mineral N fertilization rates under gnotobiotic, greenhouse, and field conditions. Six PGPR strains were employed for the tests, including three laboratory strains Bacillus velezensis GB03 (BveamGB03), B. megaterium SNji (BmeSNji), Azospirillum brasilense 65B (Abr65B), and three commercially formulated trains, B. velezensis IT45, FZB24, and FZB42. Under gnotobiotic conditions using sterile soil, all of the strains significantly increased plant biomass 14 days after inoculation irrespective of the N fertilization rates. Under greenhouse conditions, the highest growth promotion was recorded under moderate N supply (50N), followed by full N dose (100N), while no significant effect of the inoculant was observed in the absence of N fertilizer (0N). At 50N, the biomass was most significantly increased in specific plant parts, i.e. in roots (increase up to +45%) 30 days after inoculation with Abr65B and in the ears (19–23% increase) with BveamGB03, BmeSNji, Abr65B 60 days after inoculation. At 0N, FZB24 was able to significantly increase root biomass of spring wheat up to +31% 30 days after incoculation. Under field conditions, FZB24 significantly increased grain yields by 983 kg ha−1 (14.9%) as compared to non-inoculated controls at 0N in 2014 field trials. However in 2015 field trials, FZB24 was not able to replicate the previous positive results, likely due to the low temperatures occurring during and after the inoculations at tillering stage. The increase in plant biomass caused by PGPR inoculation was paralleled with lowered concentrations of several nutrients in the same organs of plants growing under greenhouse conditions. Specifically, the increases in root and ear biomass caused by BmeSNji, Abr65B were paralleled with lowered concentrations in N, P, Mn, and Cu (organ- and strain-specific). Regarding IT45 and FZB24 inoculations, when the increase in biomass was lower, only two nutrients (P and K) exhibited a lowered concentration while other nutrient (Fe, Mn, Zn, and Cu) concentrations were significant increased. In contrast, the highest increases in plant biomass stimulated by PGPR inoculations goes along with higher total nutrient content and nutrient uptake efficiency. The results are discussed in the perspective of PGPR implementation in contrasted cultivated systems and their interaction with fertilizer application. [less ▲]

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See detailRasa3 controls turnover of endothelial cell adhesion and vascular lumen integrity by a Rap1-dependent mechanism
Orban, Tanguy ULiege

Doctoral thesis (2018)

Rasa3 est une protéine activatrice des small GTPases et fait partie de la famille GAP1 qui cible Ras et Rap1. Bien que l’inactivation catalytique ou la délétion de Rasa3 en souris résulte en de nombreuses ... [more ▼]

Rasa3 est une protéine activatrice des small GTPases et fait partie de la famille GAP1 qui cible Ras et Rap1. Bien que l’inactivation catalytique ou la délétion de Rasa3 en souris résulte en de nombreuses hémorragies et à la létalité embryonnaire, la fonction biologique sous-jacente à ces défauts reste inconnue. Ici, via une combinaison d’approche in vivo en souris et zebrafish et in vitro en HUVECs, nous avons identifié un rôle clé de Rasa3 dans le développement vasculaire. L’ablation spécifique de Rasa3 dans les cellules endothéliales de la souris récapitule complétement le phénotype observé chez les souris Rasa3-/-. Des défauts de lumenisation ont été mis en évidence chez les souris où Rasa3 est spécifiquement inactivée dans la lignée endothéliale ainsi que dans le zébrafish via l’utilisation d’un morpholino. In vitro en HUVECs, la déplétion de Rasa3 augmente l’activation de l’intégrine β1, l’adhésion des cellules à la matrice extracellulaire entrainant une diminution de la migration cellulaire et unblocage de la tubulogenèse. Durant la migration, les cellules déplétées pour Rasa3 exhibent des adhésions plus larges et plus matures résultant d’une perturbation des processus d’assemblage et de désassemblage entrainant une augmentation de leur durée de vie. Ces défauts sont dus à une hyperactivation de Rap1 et à un blocage dans la signalisation FAK/Src. De plus, la déplétion de Rasa3 augmente la stabilité des jonctions cellule-cellule résultant en une diminution de la perméabilité. Finalement, des défauts d’adhésion et d’étalement des péricytes (cellules impliquées dans les interactions hétérotypic avec les cellules endothéliales) ont été observés in vivo en souris et in vitro en HUVECs. L’ensemble de ces résultats indique que Rasa3 est un régulateur critique de Rap1 dans les cellules endothéliales en régulant les propriétés d’adhésion et la maintenance de l’intégrité du lumen. [less ▲]

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See detailNitroxide Based Radical Polymers as Active Materials for Organic Radical Batteries
Aqil, Mohamed ULiege

Doctoral thesis (2018)

Research on devices for electrical energy storage systems, such as lithium ion batteries, has currently received significant attention and their applications are very popular in portable electronic ... [more ▼]

Research on devices for electrical energy storage systems, such as lithium ion batteries, has currently received significant attention and their applications are very popular in portable electronic devices (mobile phones, laptop PCs, and digital cameras), in electric vehicles (electrics cars and drones), and recently it shows promises for stationary storage (solar- and wind-energy converters). However, to satisfy the demand for their use in the future, the Li-ion batteries should possess higher performances including superior storage capacity, fast charging-discharging process, better safety, long life cycle, adaptability to multiple scales, good processability, lighter weight, flexibility, and, most importantly, cost-effectiveness and non-toxicity. Current rechargeable batteries are made of traditional metal-based (i.e., Fe, Co, Ni, Sn, Mn, V, Ta, Ru, etc.) active materials. Some of them show a high toxicity leading to serious environmental issues related to production and wastes. To solve these drawbacks, scientists investigate innovative and challenging approaches based on organic redox-active materials. As an example, nitroxides are a versatile class of stable free radicals that have long established themselves in a wide range of applications. Their incorporation into macromolecular architectures has added a further dimension to their use beyond their initial limitations and has led to several remarkable breakthroughs in energy storage applications. Organic-based radical batteries have several advantages over conventional batteries, such as increased safety, adapt- ability to wet fabrication processes, easy disposability, and capability of fabrication from less-limited resources, which are described along the fashion of green chemistry. The focus of the current work was the synthesis of polymers with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) redox moieties and their applicability as energy storage materials. A series of new monomers with pendant TEMPO moieties were successfully obtained by synthetic approach at the hydroxy function at fourth position of the TEMPO-OH. The controlled radical polymerizations were also investigated to afford well-defined polymers with controlled and tunable molar masses, functionalities, and high radical density. These novel organic materials show promising prospect for lithium ion batteries as active cathode materials. [less ▲]

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See detailInterfacial behavior of colored protein fractions from Spirulina platensis
Barka, Abakoura ULiege

Doctoral thesis (2018)

ABSTRACT This study is carried out to evaluate the interfacial activity of different fractions of Spirulina soluble proteins. Before the experimental steps, a broad literature review is highlighted to ... [more ▼]

ABSTRACT This study is carried out to evaluate the interfacial activity of different fractions of Spirulina soluble proteins. Before the experimental steps, a broad literature review is highlighted to point out the global microalgae potential, with particular emphasis on Spirulina sp. The protein content of different microalgae species is presented, together with the nutritional quality of these proteins. Out of this investigation, it clearly appeared that micro algae present a higher productivity per unit area when compared to high plants. They are able to thrive and survive in drastic climatic conditions. Spirulina platensis particularly presents high protein content with good nutritional characteristics. The first experimental assessment is the extraction of the colored Spirulina soluble protein fractions from dry Spirulina powder and evaluation of their physicochemical properties. Three fractions, including the blue soluble (BSSP), the green soluble (GSSP), and the total soluble (TSSP) Spirulina protein fractions are obtained. Investigations on their behavior at air/water interface are carried out, using dynamic methods of drop volume (TVT1), automated drop (tracker), and bubble pressure (BP100) tensiometers. Evaluation of their monolayer films mechanical behavior is done via compression isotherms using Langmuir film balance. The protein contents of the fractions are 82.76%; 82.29%; 74.53% for the blue, the green and the total fractions, respectively. Surface tension decay increases with increasing concentration for all the fractions. The tension decay is less important at pH 3 for all the fractions. The total fraction and the blue fraction appeared to form more elastic films than the green fraction. The blue soluble fraction also presented the highest collapse pressure and initial area. The second experimental evaluation is focused on the performances of colored Spirulina soluble protein fractions as surfactants at water/n-dodecane interface. Evaluation of their interfacial activities is carried out using different methods as for the air/water interface. Different concentrations (0.1%; 0.3% and 0.5% (w/w)) and pH levels (3, 5, and native pH) are tested. Results show that, the interfacial tension decay increased with increased protein concentration. At 0.3% (weight/weight) colored protein concentration in the aqueous phase, the surface tension decay is greater at pH 5 compared to pH 3 and native pH. The interfacial elastic moduli of the fractions suspensions decrease with concentration unlike viscosity moduli. Investigations on the emulsifying and foaming properties make the third experimental task. Emulsions at pH 3 are very susceptible to destabilization phenomena such as coalescence, and creaming. The emulsifying properties of the three fractions follow the same trends. However, the BSSP fraction shows a better emulsifying effect. Fractions present higher foaming capacities at their native pH, but foams are more stable at pH 3. The foaming behavior at pH 5 is close to that at the native pH. Despite the undoubted link between Spirulina protein surface activity and foaming and emulsifying properties, it should be beard in mind that the best properties are not always only obtained by the conditions of greater ability of the protein to reduce surface or interfacial tension but also to its solubility. Nevertheless the surface activity of the proteins remains the prerequisite to foaming or emulsifying properties. It should also be emphasized that the fractionation method developped in this work, unlike the methods so far available in the literature, is industrially feasible and could allow for large production of the Spirulina protein fractions. One of the obtained fractions (BSSP) presents better emulsifying ptoperties. All the three fractions present interfacial activities, and can provide foaming and emulsifying properties that would allow for their industrial use as emulsifiers in lieu and place of conventional proteins. Their color may be an asset for their use in some specific applications. [less ▲]

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See detailRevealing and Characterizing MPLS Networks
Vanaubel, Yves ULiege

Doctoral thesis (2018)

The Internet is a wide network of computers in constant evolution. Each year, more and more organizations are connected to this worldwide network. Each of them has its own structure and administration ... [more ▼]

The Internet is a wide network of computers in constant evolution. Each year, more and more organizations are connected to this worldwide network. Each of them has its own structure and administration that are not publicly revealed for economical, political, and security reasons. Consequently, our perception of the Internet structure, and more specifically, its topology, is incomplete. In order to balance this lack of knowledge, the research community relies on network measurements. Most of the time, they are performed based on the well-known tool traceroute. However, in practice, an operator may privilege other technologies than IP to forward packets inside its network. MultiProtocol Label Switching (MPLS) is one them. Even if it is heavily deployed by operators, it has not been really investigated by researchers. Prior to this thesis, only two studies focused on the identification of MPLS tunnels in traceroute data. Moreover, while one of them does not take all possible scenarios into account, the other lack of precision in some of its models. In addition, MPLS tunnels may hide their content to traceroute. Topologies inferred from such data may thus contain false links or nodes with an artificially high degree, leading so to biases in standard graph metrics used to model the network. Even if some researchers already tried to tackle this issue, the revelation of hidden MPLS devices in traceroute data is still an open question. This thesis aims at characterizing MPLS in two different ways. On the one hand, at an architectural level, we will analyze in detail its deployment and use in both IPv4 and IPv6 networks in order to improve its state-of-the-art view. We will show that, in practice, more than one IPv4 trace out of two crosses at least one MPLS tunnel. We will also see that, even if this protocol can simplify the internal architecture of transit networks, it also allows some operators to perform traffic engineering in their domain. On the other hand, MPLS will be studied from a measurement point of view. We will see that routers from different manufacturers may have distinct default behaviors regarding to MPLS, and that these specific behaviors can be exploited to identify MPLS tunnels during traceroute measurements. More precisely, we will focus on new methods able to infer the presence of tunnels that are invisible in traceroute outputs, as well as on mechanisms to reveal their content. We will also show that they can be used in order to improve the inference of Internet graph properties, such as path lengths and node degrees. Finally, these techniques will be integrated into Trace the Naughty Tunnels (TNT), a traceroute extension able to identify all types of MPLS tunnels along a path towards a destination. We will prove that this tool can be used in order to get a detailed quantification of MPLS tunnels in the worldwide network. TNT is publicly available, and can therefore be part of many future studies conducted by the research community. [less ▲]

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See detailCombining ecological niche models and dispersal simulations to predict bryophytes dynamic response to climate changes
Zanatta, Florian ULiege

Doctoral thesis (2018)

Despite a growing number of climate change mitigation policies, anthropogenic greenhouse gas emissions have continued to increase over 1970 to 2010, with larger absolute increases between 2000 and 2010 ... [more ▼]

Despite a growing number of climate change mitigation policies, anthropogenic greenhouse gas emissions have continued to increase over 1970 to 2010, with larger absolute increases between 2000 and 2010. Indeed, the period from 1983 to 2012 has been identified as the warmest 30-year period of the last 1400 years in the Northern Hemisphere. As a result, climate changes have been identified as one of the major biodiversity threats, with the worst-case scenarios leading to extinction rates that would qualify as the sixth mass extinction in the history of the earth. Species distribution models (SDMs) have been the most widely used tool to assess the impact of future climate changes on biodiversity patterns, using spatial information to infer species ecological niches from climatic conditions that prevail today across the distribution range occupied by the species. One of the main assumptions of these models is, however, that species live at equilibrium with their environment, as if they had no dispersal limitations. Such an assumption is critical if we aim at projecting these modeled ecological niches under future climatic conditions. The main goal of the present thesis was to develop an integrative, spatially explicit model to make predictions of range shifts in wind-dispersed organisms in a context of climate changes. More precisely, we calibrated a Wald analytical long distance dispersal model with species intrinsic biomechanical features (i.e., the settling velocity of diaspores and their release height) and environmental variables (i.e., canopy height, wind intensity and turbulence), through direct observations of diaspore deposition patterns. We then integrated this dispersal model combined with habitat suitability maps into a modified version of MigClim’s cellular automaton that allows migration simulation of species across the landscape, while implementing environmental change scenarios. Initially, MigClim assumed an isotropic colonization probability around a source population with a single constant dispersal kernel across the landscape. This was challenging its use for wind-dispersed organisms because (i) wind movements are directional and (ii) wind velocity varies widely from an area to another across the landscape. We therefore developed this method to (i) allow the integration of asymmetrical dispersal depending on wind parameters and (ii) render the dispersal kernel spatially-explicit by sampling pixel-specific wind speed and canopy structure along the migration simulations. We applied this method to predict how climate changes will impact future distribution ranges in bryophytes, which are particularly sensitive to climatic variations due to their poïkilohydry. We started by measuring bryophytes spores settling velocities using a high-speed camera experiment and produced a predictive model as a function of spore size. The non-sphericity and particular ornamentation patterns of the outer spore wall caused some mismatch between observed and predicted settling velocities, raising questions on how these striking variations in shape and texture affect their dispersal capacity. However, we globally identified a significant relationship between spore9 settling velocity and size. Based on these spore fall speed estimates and a set of SDM derived maps of habitats suitability at present time and in predicted 2050 climatic conditions in Europe, we ran a sensitivity analysis on a modified version of MigClim to test the impact of differences in spores release height and horizontal mean wind speed. Variation in predicted colonization success was significantly driven by release height but not by differences in horizontal mean wind speed, suggesting that, in small-sized wind-dispersed organisms like bryophytes, there is a strong evolutionary pressure for elevating the sporophyte above ground. The implementation of the combined model on three species of contrasted distribution across Europe reveals much higher extinction than colonization rates, even for the most optimistic climatic scenarios and the most successful wind dispersal kernels. Although additional models need to be produced to forecast climate changes impacts on a wide range of bryophyte species, our preliminary results point to a much more severe impact of climate warming for bryophytes as compared to vascular plants. This highlights the primary role of bryophytes as indicators of climate changes. [less ▲]

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See detailDevelopment of new tools to detect, characterize and quantify quantum entanglement in multipartite systems
Neven, Antoine ULiege

Doctoral thesis (2018)

Quantum entanglement is a key property of quantum information theory, that is at the heart of numerous promising applications in fields such as quantum cryptography, quantum computing or quantum sensing ... [more ▼]

Quantum entanglement is a key property of quantum information theory, that is at the heart of numerous promising applications in fields such as quantum cryptography, quantum computing or quantum sensing. In the past decades, the advent of such innovative technologies has reinforced the need for a better understanding of entanglement. The aim of this thesis is to contribute to this effort through the development of new tools targeting the characterization of several features of entanglement. Concerning the issue of entanglement detection, we present an optimization of the approach that exploits the concept of generalized concurrences to solve the separability problem for pure states. We then reformulate the separability question of mixed states into a matrix analysis problem, from which we obtain general separability criteria for multipartite states of ranks two and three. We also briefly discuss some properties of separable states. In particular, we characterize optimal separable decompositions of symmetric (i.e. permutation invariant) states of two and three qubits with maximal rank properties. Regarding the quantification of entanglement, we propose a function to quantify the entanglement of symmetric multiqubit states within classes of entangled states gathering states that are stochastically equivalent through local operations assisted with classical communication. This function establishes a link between the amount of entanglement of a symmetric state and the distribution of its Majorana points on the Bloch sphere. We finally investigate the robustness of entanglement with respect to particle loss and provide a full description of all multiqubit states that are fragile for the loss of one of their qubits. For symmetric states, the fragility for the loss of one qubit is shown to be related to a particular symmetry of the Majorana points. [less ▲]

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See detailTactical Planning on Freight Transport Networks: Service Design and Pricing
Tawfik, Christine Maher Fouad ULiege

Doctoral thesis (2018)

Freight transport plays an essential role in economic and societal development. In particular, consolidation-based systems, using several transport modes, are crucial to the realization of world trade ... [more ▼]

Freight transport plays an essential role in economic and societal development. In particular, consolidation-based systems, using several transport modes, are crucial to the realization of world trade activities. Also, on the environmental side in Europe, policy makers and researchers are increasingly interested in endorsing sustainable forms of transport and diverting freight flows from the heavily dominating road. New challenges are, however, identified at the decision-making level, in order to efficiently handle the complexity of the underlying network and the related high costs. During the course of this work, tactical planning issues are discussed within the view of intermodal transport management, as a relevant application context. First, service network design models are presented from the carrier’s perspective, involving long-corridor aspects. Second, pricing decisions are integrated so as to account for the reaction of the shippers, within a bilevel program. The model is enriched in different ways that encompass a level-of-service assessment. Real-world case studies are considered based on the implemented frameworks, in order to provide managerial insights into intermodal transport and evaluate EU-intended policy levers. Finally, the algorithmic aspects of the developed bilevel model are investigated within two heuristic procedures that extend classical frameworks and provide new methodological advancements. [less ▲]

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See detailStudy of microbial and physicochemical factors determining the long-term preservation of chilled fresh beef at subzero temperatures
Didimo Imazaki, Pedro Henrique ULiege

Doctoral thesis (2018)

Fresh meat is a highly nutritious but extremely perishable food, and its preservation is a significant challenge since early civilisations. In the past decades, food trade has become more globalised ... [more ▼]

Fresh meat is a highly nutritious but extremely perishable food, and its preservation is a significant challenge since early civilisations. In the past decades, food trade has become more globalised, forcing supply chains to become larger and more complex. As such, meat, which typically has a short shelf life, is required to stay fresh for longer. Extended shelf life in beef may be achieved through strict control of the product hygiene associated with vacuum packaging and subzero chilling. The research presented in this thesis was designed to investigate the effect of microbial and physicochemical factors, namely the growth of spoilage bacteria and oxidation of myoglobin and lipids, on the long-term preservation of chilled fresh beef at temperatures above the freezing point of meat (−2°C) but below 0°C. This research was divided into the following main topics: (1) the study of the preservation of chilled fresh meat with extremely long shelf life, (2) the study of the preservation of chilled fresh meat from the Belgian Blue breed and (3) the study of Carnobacterium maltaromaticum as a protective culture for meat. This study provided evidence that the use of sub-zero temperatures during vacuum storage is essential in meat shelf life extension since it retards meat deterioration, preventing the oxidation of myoglobin (discolouration) and growth of spoilage bacteria. Intrinsic factors including the metmyoglobin reducing activity as well as the activity of antioxidant enzymes, such as catalase, superoxide dismutase and glutathione peroxidase, can be associated, in varying degrees of importance, with the retardation of oxidation reactions in meat. Carnobacterium maltaromaticum was the dominant bacteria in meats with extremely long shelf life. Selected C. maltaromaticum isolates obtained from these meats showed an antilisterial activity in vitro, which was optimised at low temperatures. When studied directly in raw meat with the natural indigenous microbiota, C. maltaromaticum showed an antimicrobial effect against Enterobacteriaceae. Further research on the antioxidant mechanisms and microbial ecosystems associated with meats with extremely long shelf life will be a key to understand and improve the extension of the shelf life of fresh meat. [less ▲]

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See detailImprovement of the Indoor Air Quality in Housings of Ho Chi Minh City (Vietnam) by Adapting the Ventilation System to Minimize the Pollutants Concentrations
Tran Thi Thu, Thuy ULiege

Doctoral thesis (2018)

We spend about 90% of our time inside buildings, where we could control the quality of the environment for health, thermal comfort, security and productivity. The quality of the indoor environment is ... [more ▼]

We spend about 90% of our time inside buildings, where we could control the quality of the environment for health, thermal comfort, security and productivity. The quality of the indoor environment is affected by many factors including design of the building, ventilation, thermal insulation, energy provision and use. It is evident from preliminary studies that Indoor Air Quality (IAQ) in Vietnam housing is under-researched and there is a clear lack of awareness among housing occupants of the harmful effects of chemicals that exist inside housings. Houses in warm-humid regions depend on large openings and through ventilation for thermal comfort. Openings allow air pollution and noise to penetrate these houses easily, thereby affecting the health, comfort and well-being of residents. Closing all openings and changing from natural ventilation to air conditioning is not however a practical solution for low cost housing. As a result, the study was set out to review the previous related research studies in the field of IAQ, identify the current status of IAQ in HCMC, and find solutions to implement IAQ best practice in three sample houses as a pilot for achieving good IAQ. Through this study, we found evidences that residents of rental houses were exposed to slightly high levels of CO2 during the night-time or at anytime when the occupants closed the door for sleeping or for personal activities. The indoor CO concentrations were over 20 ppm in rush hours in some houses which located nearby streets and opened the entrance doors for sale. We found that housing residents might be disproportionately exposed to high levels of PM2.5 and TVOC due to the presence of many indoor sources. Poor thermal comfort was also found to be a prevalent issue in most of sample houses, but there was not enough data on comparable indoor and outdoor to make a definitive statement about relative prevalence. Indoor air quality is influenced by location of the house, opening design, and opening behavior. Air quality in residential buildings, especially in the living-rooms, was generally poorer with the houses having no outlets to outside and no exhaust fans and this was true for both houses near or far from a road. Lastly, the study indicated that there were feasible and practical solutions to the reduction of indoor air pollution in such housings by changing opening design, changing opening habits and applying local ventilation. The renovations were found high efficiency to reduce indoor CO and TVOC in hot and humid condition. Based on low cost development, this application can be applied with natural ventilation system in housings in big cities of Vietnam. [less ▲]

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See detailHousehold risk management strategies in coastal aquaculture in Vietnam: The case of clam farming in Thaibinh province
Ngo Thi Thu Hang, ULiege

Doctoral thesis (2018)

With over 3,260 kilometers of coastal line and 112 estuaries, 226,000 square kilometers of internal waters and territorial waters, the exclusive economic zone of more than 1 million square kilometers, and ... [more ▼]

With over 3,260 kilometers of coastal line and 112 estuaries, 226,000 square kilometers of internal waters and territorial waters, the exclusive economic zone of more than 1 million square kilometers, and more than 4,000 islands, forming 12 bays and lagoons with a total area of 1,160 square kilometers, Vietnam has high potentials for aquaculture development. Vietnam's seafood output has been growing steadily in recent years (since 2000 up to 2016) with an average increase of 9% per year. Despite its advantages and positive development trends, Vietnam aquaculture has faced several issues including asymmetric information and high demand for quality products. The main cause of these issues is risks, from production to market risks. This study has explored the main risks faced by the coastal clam farming sector in Thaibinh province located in northern Vietnam. The risks can be classified into two types in term of the nature of their cause: man-made and natural ones, and three types in term of their impact: production, market and financial risks. The causes of these risks include extreme weather events, wasted water flows, production technics; market access or financial capacity. However, man-made risks are more severe and more difficult to cope with than natural ones. These above risks have serious consequences for clam farming. For the three communes examined in this study, less than half of the farmers were yet recovered from the loss caused by several shocks although majority of them had mobilized capital to restart clam farming. About one third of the farmers had to sell their fixed assets to pay debts related to their clam investment, and ten households had left their villages under the pressure of debts. However, in such risky clam farming environments and increased market difficulties, not all farmers were seriously impacted. Indeed, it is surprising that one fifth of the surveyed farmers succeeded in all their clam raising cycles so far, and another quarter remained well resilient after the shocks. Different household risk management strategies applied in clam farming are thus discussed in the comparative analysis and discriminant analysis. In general, the tactics related to increasing farm size, applying technical innovation and accessing financial sources with no or a lower interest rate, provided better conditions for clam growth, reducing clam farming losses. They also facilitated speedier recovery from shocks. There are many internal and external factors in the application of risk management strategies and tactics. Of the internal factors identified, include households’ financial capacity and the experiences of the head of households had more impact while the education level and the job of the head of household seemed to have little influence on the choice and application of households’ risk management strategies. External factors refer to the policy factors and the knowledge capacity enhancing activities in the clam farmers community. Among these activities, those of “groups for experience sharing” were found to have significantly greater impact than the training courses and activities of farmer’s union. Besides, the government had played a role in directing farmers in clam farming practices, but not much in risk management. Given that the tactics addressed the capital issues, land uses, and clam farming techniques had positively contributed to the result of household risk management strategies whilst experience gaining and sharing activities strongly impacted the application of these tactics. The intervention and policies of government in all levels to the farmers should therefore focus more on these issues. It is vital that the government’s support policies, extension programs, training courses and farmer’s union activities be practically oriented and suit farmers’ desires. Furthermore, the addition of policies/interventions in market issues (for both input and output) should be taken into account because those risks were considered as meso level, which farmers cannot solve by themselves and thus definitely need the support from the government, from local to the state level. To support farmers in managing risks, several government interventions are needed: (1) improving the support system to household in clam farming such as increasing farm size, promoting linkages to market and training technic; (2) increasing investment in the treatment of the water management issue and protecting the ecosystem; and (3) promoting participatory policy formulation and its enforcement. [less ▲]

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See detailNano-engineering superconducting junctions by atomic migration
Baumans, Xavier ULiege

Doctoral thesis (2018)

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See detailEssays on Long-Term Care
Schoenmaeckers, Jérome ULiege

Doctoral thesis (2018)

In the last decades, life expectancy at birth has sharply risen in all European countries and North America. This increasing life expectancy is definitely accompanied by an improvement of the health state ... [more ▼]

In the last decades, life expectancy at birth has sharply risen in all European countries and North America. This increasing life expectancy is definitely accompanied by an improvement of the health state of elderly people. But an ageing population also leads to an increase in the number of dependent people. Dependence is defined as the partial or total impossibility for a person to perform without help some essential activities of daily living. The first chapter shows that poor people are more likely to die and become dependent than the rich. The second chapter explores the motives of help between children and parents. Long-term care seems to be driven by moderate altruism or by family norm. The third chapter demonstrates the presence of strategic spend-down in the US allowing elderly people to benefit from the public aid even though they would have the financial means to buy this care on the market with their own resources. Finally, the fourth chapter establishes the determinants of the individual insurance purchase decision in a context where the individual's future health and income evolution is uncertain. We estimate that the less educated value less the long term care insurance than the educated. A multitude of questions are still unresolved and the dependence, a state that all will face one day (with a grandparent, a parent, a sibling, a friend or oneself) is a field of exalting research. [less ▲]

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See detailCooperative dynamics and self-propulsion of active matter at interfaces
Hubert, Maxime ULiege

Doctoral thesis (2018)

Active particles, and more generally active matter, are known for their ability to move in a given medium by harnessing energy in their surrounding or by carrying their own energy reservoir. A large field ... [more ▼]

Active particles, and more generally active matter, are known for their ability to move in a given medium by harnessing energy in their surrounding or by carrying their own energy reservoir. A large field of interest regarding active particles is their collective behaviour due to the interactions between individual components of the active system. Examples can be found in biology, medicine, microfluidic or chemistry. In this thesis, the role of individuals in active matter is investigated in two peculiar systems: walking droplets and magnetocapillary microswimmers. Each system lies at an liquid-air interface and relies on the deformation of the liquid surface in their dynamics. Walking droplets are known to propel themselves thanks to the standing capillary waves they generate at each impact on the liquid interface. The persistence time of those waves can be controlled which allows to keep images of the droplet on the interface and to alter the particle motion. This is the memory of the walking droplets. Changing this persistence time allows to change the number of images of the droplet and to explore different dynamics. The limit of extremely large persistence time is considered in this manuscript. In free space, this unique wave memory dynamics allows to generate the first example of deterministic run and tumble dynamics widely encountered in biology. This behaviour finds its origin in the wavefield which traps temporarily the walking droplets. The properties of this run and tumble dynamics are shown to by directly related to the memory stored in the wavefield. If placed in an harmonic potential, the walking droplet is forced to continuously interact with this own wavefield. It is shown that the waves self-organise. In this case, the energy stored in the wavefield mimics an equipartition of energy as well as a minimisation principle. Magnetocapillary microswimmers use the liquid interface in order to self-assemble and the liquid underneath in order to move thanks to hydrodynamic interactions and non-reciprocal deformation. This thesis models two different experimental microswimmers: the linear microswimmer better known as the NajafiGolestanian microswimmer and the triangular magnetocapillary microswimmer. In each case, the non-reciprocal deformation required for the swimming dynamics is at the centre of the discussion. For the linear structure, non-reciprocity is produced by breaking the spatial symmetry of the swimmer. We also discuss the importance of the particles inertia in this low Reynolds dynamics. For the triangular structure, a new swimming mechanism is highlighted where the particles rotation and the structure deformation act cooperatively to generate the translation of the swimmer along the interface. This findings constitute the first step towards the modelisation of larger structures and more efficient swimmers for application in microfluidic. [less ▲]

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See detailDes régions qui comptent. La reconfiguration néolibérale de la Belgique fédérale saisie par les finances publiques
Piron, Damien ULiege

Doctoral thesis (2018)

This PhD studies the process of neoliberalization of Belgium and its regions through the lens of public finance. From a theoretical perspective, it aims to contribute to the development of the emerging ... [more ▼]

This PhD studies the process of neoliberalization of Belgium and its regions through the lens of public finance. From a theoretical perspective, it aims to contribute to the development of the emerging sociology of public finance. To do so, it connects existing theories with governmentality studies, mixed with insights from the sociology of accounting, science and technology studies and human geography. In the second part of the thesis, this original theoretical framework is put to the test of five case studies, which relate to two broader programmes of government in the field of public finance: Belgian fiscal federalism (i.e. the distribution of tax and fiscal powers between federal and regional authorities) and European Fiscal Governance (i.e. European quantified indicators imposing debt- and deficit-to-GDP ceilings). Each of this case study tackles a controversial dimension of the complex and changing relationship between regions, the federal authority and the European Union: a long-lasting controversy about the calculation of interregional fiscal flows between Flanders and Wallonia; the reform of the Special Finance Act of Communities and Regions during the sixth state reform (2010-2011); the creation of a European statistical apparatus built around Eurostat in order to permanently monitor national public finance; the competing conventions of equivalence underlying the calculation of the Walloon public debt; and, lastly, the statistical treatment of Public-Private Partnerships (PPPs). The discussion stresses the fundamental role played by the two programmes of government under study in the diffusion of the so-called neoliberal rationality in Belgium and its regions. In other words, Belgian fiscal federalism and European fiscal governance strongly incentivize, each in their own way, Wallonia and Flanders to pursue policies simultaneously aiming at strengthening fiscal consolidation and fostering competition – be it between public administration and private companies or among (inter)national political authorities. It is shown that one of the main contradictions associated with this process of ‘economization’ of Belgian regions lies in the field of investment policy: does it remain possible to effectively conduct ambitious public investment projects in an ever more decentralized federation committed to fiscal discipline? The ‘solution’ currently implemented to solve this paradox – namely an increased utilization of hybrid investment schemes such as PPPs – de facto reinforces the neoliberal logic of (quasi-)privatization of public service delivery in Belgium. [less ▲]

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See detailFirst-principles study of piezoelectric (Ba,Ca)TiO3-Ba(Ti,Zr)O3 solid solutions
Amoroso, Danila ULiege

Doctoral thesis (2018)

High-performance piezoelectrics are key components of various smart devices and, recently, it has been discovered that (Ba,Ca)(Ti,Zr)O 3 (BCTZ) solid solutions show appealing electromechanical properties ... [more ▼]

High-performance piezoelectrics are key components of various smart devices and, recently, it has been discovered that (Ba,Ca)(Ti,Zr)O 3 (BCTZ) solid solutions show appealing electromechanical properties. Nevertheless, the microscopic mechanisms leading to such features are still unclear and theoretical investigations of BCTZ remain very limited. Accordingly, this thesis analyzes the properties of various compositions of (Ba,Ca)TiO3-Ba(Ti,Zr)O3 solid solutions by means of first-principles calculations, with a focus on the lattice dynamics and the competition between different ferroelectric phases. We first analyze the four parent compounds BaTiO3, CaTiO3, BaZrO3 and CaZrO3 in order to compare their properties and their different tendency towards ferroelectricity. Then, the core of our study is a systematic characterization of the binary systems (Ba,Ca)TiO3 and Ba(Ti,Zr)O3 within both the virtual crystal approximation (VCA) and direct supercell calculations. When going from BaTiO3 to CaTiO3 in (Ba,Ca)TiO3, the main feature is a gradual transformation from B-type to A-type ferroelectricity due to steric effects that largely determine the behavior of the system. In particular, for low Ca-concentration we found out an overall weakened B-driven ferroelectricity that produces the vanishing of the energy barrier between different polar states and results in a quasi-isotropic polarization. A sizable enhancement of the piezoelectric response results from these features. When going from BaTiO3 to BaZrO3 in Ba(Ti,Zr)O3, in contrast, the behavior is dominated by cooperative Zr-Ti motions and the local electrostatics. In particular, low Zr-concentration produces the further stabilization of the R3m-phase. Then, the system shows the tendency to globally reduce the polar distortion with increasing Zr-concentration. Nevertheless, ferroelectricity can be locally preserved in Ti-rich regions. We also found out an unexpected polar activation of Zr as a function of specific atomic ordering explained via a basic electrostatic model based on BaZrO3/mBaTiO3 superlattice. A microscopic factor behind the enhanced piezoelectric response in BCTZ, at low concentration of Ca and Zr, can thus be the interplay between weakened Ti-driven and emerging Ca-driven ferroelectricity, which produces minimal anisotropy for the polarization. In addition, our comparative study reveals that the specific microscopic physics of these solid solutions sets severe limits to the applicability of the virtual crystal approximation (VCA) for these systems. [less ▲]

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See detailCharacterization of neurodegenerative diseases with tree ensemble methods: the case of Alzheimer's disease
Wehenkel, Marie ULiege

Doctoral thesis (2018)

For the last decade, the neuroscience field has observed the emergence of machine learning methods for the analysis of neuroimaging data. Unlike univariate methods that consider voxels one per one, these ... [more ▼]

For the last decade, the neuroscience field has observed the emergence of machine learning methods for the analysis of neuroimaging data. Unlike univariate methods that consider voxels one per one, these techniques analyse relationships between several voxels and are able to detect multivariate patterns. In the context of neurodegenerative diseases, such as Alzheimer’s disease (AD), they can be used to design a diagnosis system and to find in neuroimages the patterns responsible for the disease. The context of the work presented here is thus the field of pattern recognition with neuroimaging. Our objective is to explore the possibilities that tree ensemble methods, such as Random Forests, offer in this domain in general, and in particular in the context of AD research. These methods suit very well the needs of this domain, as they combine very good predictive performances and provide interpretable results in the form of variable importance scores. Our contributions include both methodological developments around tree ensemble methods and applications of these methods on real datasets. The methodological part of the thesis focuses on the analysis and the improvement of Random Forests variable importances for neuroimaging problems. Typical datasets in this domain are of very high dimensionality (hundreds of thousands of voxels) and contain comparatively very few samples (tens or hundreds of patients). Our first contribution is a theoretical and empirical analysis of how importance scores behave in such extreme settings, depending on the method parameters. We then propose several improvements of importance scores in such settings that take advantage of either the spatial structure between the features or a pre-defined partitioning of these features into groups. Finally, we address an issue with Random Forests importances, which is to find a threshold between truly relevant and irrelevant variables. For this purpose, we adapt several statistical methods proposed in the bioinformatics literature. These methods are extended to compute a statistical score for groups of features instead of individual features. This adaptation at the group level has been raised from our expectation to find groups of voxels explaining a disease instead of isolated voxels. We show that working at the group level leads to a higher statistical power than working at the feature level. The approach is applied on a real dataset for the prognosis of AD, where it is shown to highlight brain regions that are consistent with results in the literature. In the second part of the thesis, we show different applications of Random Forests for AD research. First, we use tree-based ensemble methods in order to clinically characterize two different metabolic profiles observed in PET scans of AD patients. Second, we carry out an empirical comparison that shows that Random Forests are competitive with linear methods, in terms of accuracy and interpretability, on different real datasets related to three research questions about AD: the diagnosis of demented patients, the prognosis of mild cognitively impaired (MCI) patients, and the differentiation of MCI and AD patients. [less ▲]

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See detailPassive magnetic shielding with bulk high temperature superconductors under a non-uniform magnetic field
Hogan, Kevin ULiege

Doctoral thesis (2018)

The goal of this thesis is to comprehend the influence of the inhomogeneity of the magnetic field distribution on the low frequency shielding performances of passive bulk high-temperature superconducting ... [more ▼]

The goal of this thesis is to comprehend the influence of the inhomogeneity of the magnetic field distribution on the low frequency shielding performances of passive bulk high-temperature superconducting magnetic shields. We aim at gaining a better understanding of the magnetic field penetration, of the shape of the flux front and of the shielding current distribution within the superconducting shield. We also seek to locate spots where the local magnetic flux density is the strongest, i.e. corresponding to the location of the easiest “flux entry gates”. The inhomogeneity of the magnetic field distribution is characterized using two parameters - its gradient and the curvature of flux lines - which are interdependent because of Gauss law. For our investigation we consider three shielding problems of increasing complexity in terms of loss of symmetry between the magnetic screen and the field distribution, thus increasing the inhomogeneity of the magnetic field and the distribution of shielding currents. Each configuration corresponds to a given magnetic field source for which the magnetic field experienced by the superconducting shield is characterized and analyzed. The superconductors investigated experimentally are all made of bulk Bi-based high-temperature superconductors (either Bi2Sr2CaCu2O8 [Bi-2212] produced by melt-cast process or polycrystalline Bi2Sr2Ca2Cu3O10 [Bi-2223]). With the first problem, we consider a bulk superconducting tube subjected to the inhomogeneous magnetic field generated by a coil placed inside the shield, which corresponds de facto to an “emission” problem configuration. We show, in the axisymmetric situation where the source coil is placed coaxially to the tube and at its center, that the maximum applicable magnetic field that can be shielded can be approximated analytically with a simple 1D model based on magnetic flux conservation, and is in remarkably good agreement with the experimental data. This model predicts and quantifies the phenomenon of magnetic flux concentration occurring between the source coil and the inner surface of the superconductor and originating from the diamagnetic behavior of the superconductor. Unlike a superconducting magnetic shield placed in a uniform external field, for which the maximum field to be screened depends primarily on the wall thickness, our results show therefore it is necessary to take into account the total volume of the shield for an optimal design in an “emission” configuration. The second problem involves a magnetic shield subjected to the inhomogeneous stray field of a solenoidal coil placed at moderate distance (of the order of the height of the coil) and such that the field is quasi-axial. We show that the magnetic field experienced by the superconductor can be approximated as the field generated by an equivalent magnetic dipole at the center of the coil, thus generalizing our results to situations where the dipolar approximation stands valid. We compare this situation to that of a tube subjected to an oblique homogeneous magnetic field and observe similarities in the shielding current distribution. Our results give evidence that the characteristics of the shielding currents in an inhomogeneous field are primarily related to the orientation of the local applied field. Moreover, we observe that, when considering oblique fields, portions of the magnetic shield act to reduce the magnetic flux density within the superconductor but not necessarily within the inner space delimited by the shield. The third investigated configuration involves the magnetic field generated by a pancake coil placed at very short distance of the magnetic shield. In this situation the superconductor is subjected to a quasi-transverse magnetic field. We show how the inhomogeneity of the magnetic field affects the shielding current distribution within the superconductor by comparing our results to those obtained when considering a similar shield subjected to an uniform transverse field. We also observe how the location of the strongest magnetic flux density points is affected. In this configuration the temperature dependence of the shielding performances is also examined thanks to a bespoke variable temperature measurement system. We point out the difficulty to analyze the superconductor behavior using a creep exponent as the measured properties result from two effects acting together: the temperature dependence of the creep exponent and the effective volume of the magnetic shield penetrated by the magnetic flux lines, which is directly related to the degree of inhomogeneity of the magnetic field. Two finite element models are developed: a 2D axisymmetric model based on an A formulation and a 3D model using an H-φ formulation. Both offer results in agreement with analytical results and results obtained with the Brandt method. Moreover, they are in good agreement with the experimental results and provide relevant information regarding the flux penetration and the shielding current distribution. In particular, the 3D model permits the treatment of the general case of a superconducting shield which can be multiply connected, i.e. containing holes, subjected to inhomogeneous magnetic fields. Finally, we carry out a magnetic shield topology analysis for the design of a magnetic shield for a real practical application: an ultra-sensitive particle detector operating at very low temperature. [less ▲]

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See detailA Comparative Study of Labeling Algorithms within the Branch-and-Price Framework for Vehicle Routing with Time Windows
Michelini, Stefano ULiege

Doctoral thesis (2018)

The Vehicle Routing Problem with Time Windows (VRPTW) is a well-known extension of the Vehicle Routing Problem, one of the oldest and most studied problems in combinatorial optimization. The VRPTW ... [more ▼]

The Vehicle Routing Problem with Time Windows (VRPTW) is a well-known extension of the Vehicle Routing Problem, one of the oldest and most studied problems in combinatorial optimization. The VRPTW consists in finding an optimal set of routes for a fleet of vehicles based in a single depot in order to service a set of customers. Each customer is associated with a time window, which specifies the earliest and the latest possible service start times. Time windows are a natural feature of a number of applications, such as postal deliveries, grocery deliveries, or school bus routing. In addition to the VRPTW, we consider a variant of this problem where the aim is to minimize the total route duration, instead of just the total travel time. Thus, the waiting times that are incurred by vehicles before they can service a customer are taken into account in the objective function of the problem. This aspect is relevant in applications where waiting times bear an implicit cost, such as when the vehicles are rented by the distribution company, or when they consume energy during idle times, as in the case of refrigerated trucks delivering perishable goods. Branch-and-Price (BP) is one of the most effective and commonly used exact methodologies for solving routing problems. In recent years, several studies have investigated advanced labeling algorithms to solve the related pricing problem, which is usually a variant of the elementary shortest path problem with resource constraints. Being able to solve this subproblem efficiently is crucial, since it is a major bottleneck for the performance of the BP procedure. Each of these methods uses a certain strategy to relax the elementarity constraints of the pricing problem in order to accelerate its solution. In this study, we investigate the performances of several such methods within a BP framework. In order to perform rigorous comparisons, we first parametrize several algorithmic components. Then, we search for good parameter configurations for each algorithm with a tool for automated parameter tuning. Finally, we run the best configuration found for each algorithm on benchmark instances and analyze the results with statistical tests. Our results show in particular that a class of hybrid algorithms, where multiple customer sets are used to control the relaxation of the elementarity conditions, rather than a single one, outperforms all the others. [less ▲]

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See detailÉvaluation des potentialités de l'imagerie hyperspectrale proche infrarouge et de la chimiométrie dans l'étude de systèmes racinaires.
Eylenbosch, Damien ULiege

Doctoral thesis (2018)

Roots play a vital role in plant development. First organ appearing at plant installation, they provide plant anchorage and absorb water and nutrients in the surrounding soil. Roots play also a role in ... [more ▼]

Roots play a vital role in plant development. First organ appearing at plant installation, they provide plant anchorage and absorb water and nutrients in the surrounding soil. Roots play also a role in relations between plants, from the same species or not, and with soil microorganisms. Furthermore, by their exudates and their decay, roots bring large amount of carbon in soils. Their study is therefore essential in order to face the present challenges in agronomy and with climate changes: decrease of water and nutrient resources, interspecific competition, intercropping and carbon storage in soils. This study is even more interesting when it is conducted in natural plant growing conditions. All root studies conducted in natural conditions face to the same problem: the soil presence which hinder roots and do not allow direct observations. Root studies are therefore based on estimations and a compromise between observation quality and number of feasible observations. Among existing techniques for root study, soil coring seems to be the most used. This technique, which is easy to use, allows rapid acquisitions of large number of soil samples containing roots. This ability to acquire a large number of samples allow the sampling replication in time and space and allow therefore to study root development dynamic and root distribution in soils. This technique is therefore often used as a reference. In order to observe, measure and quantify roots acquired with this method, soil cores have to be washed to extract roots from soil. These roots have then to be separated from the other elements present in the cores: dead roots, roots from other species, crop residues, soil particles, macro organisms… These washing and sorting steps are time consuming and tedious, depend on operator ability and are therefore the main limitation in observation replication. Moreover, some elements extracted from soil cores are hardly separable on their visual aspect. In order to facilitate, objectify and reduce the time needed for the manual sorting step, a new method, based on near infrared hyperspectral imaging and chemometrics, was proposed. Near infrared hyperspectral imaging is a chemical analysis technique combining imagery and spectroscopy and allowing the acquisition of one single near infrared spectrum for each pixel of an image. This spectrum is a signature linked to the physicochemical nature of the pixel on which it is acquired. Chemometrics is the science allowing the extraction of relevant information from spectra. This method was first used to discriminate roots, soil particles and crop residues extracted by washing soil cores. The developed chemometric models allowed the classification, in predefined classes, of each pixel of hyperspectral images acquired on soil samples. The composition of studied samples was therefore known. By linking the number of pixels classified as root to a root mass, it was then possible to predict the root mass in a sample without having to sort it manually and to weight it. Based on their spectral signature, this method also allowed discrimination and quantification of roots from different species and study on root composition. As part of the research conducted in this thesis, near infrared hyperspectral imaging was used to study root development of winter wheat cultivated after contrasted tillage practices, to quantify roots from winter wheat and pea crops cultivated together and to measure leghaemoglobin content, a protein involved in nitrogen fixation by legumes, in pea nodules. Research also aimed to study the quality of several discriminant models, to characterize hyperspectral image acquisition system stability and to identify error sources when this method was used to quantify root masses. Although these research showed the potentialities of near infrared hyperspectral imaging in root studies (sorting and weighting steps suppression, opportunities in quantification of roots from several species and of root compounds), they also highlighted the limits of this method. These limits in precise root mass quantification are due to image acquisition system instability, image resolution, overlapping of roots and crop residues during image acquisition and difficulties to classify some spectra. Moreover, developed models are only usable in discrimination of spectral classes for which they were- built. They are therefore not useable on new elements like roots from other crops. With their advantages and limitations, near infrared hyperspectral imaging and chemometrics can therefore be used to estimate roughly root masses but is currently not usable for precise measurements. They seem to be particularly interesting to study leghaemoglobin content in single nodules and to study the distribution of these contents on legume root systems. [less ▲]

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See detailComment une innovation organisationnelle radicale devient-elle la référence dans l’administration publique ? NMP et NWoW dans la fonction publique fédérale belge
Vandenbergh, Jean-Marc ULiege

Doctoral thesis (2018)

Depuis quelques années, de nouvelles formes d’organisation du travail inspirées du « New Ways of Working » se mettent en place dans la fonction publique fédérale belge. Il s’agit d’une véritable réforme ... [more ▼]

Depuis quelques années, de nouvelles formes d’organisation du travail inspirées du « New Ways of Working » se mettent en place dans la fonction publique fédérale belge. Il s’agit d’une véritable réforme organisationnelle des administrations publiques qui fait suite au changement radical que le « Ministère », administration pionnière, a mis en place. Ce dernier a introduit un modèle organisationnel innovant dans lequel le travailleur décide lui-même comment, où et quand il travaille. Ce changement organisationnel innovant et radical n’est pas un fait banal. Il l’est d’autant moins que l’initiative de ce changement fut prise par des leaders de services publics. Ceci alors que la littérature reconnait que les décisions stratégiques concernant les administrations publiques sont habituellement le fait de l’autorité politique. Les leaders de notre étude ont, en quelque sorte, dépassé leur marge d’autonomie pour initier un changement organisationnel stratégique de grande ampleur. Nous avons donc cherché à comprendre comment un tel changement fut possible. A cette fin, nous avons mobilisé pas moins de trois cadres théoriques : la Sociologie de l’Acteur Réseau (SAR), la Théorie de la Régulation Sociale (TRS) et les Théories Institutionnelles (TI). Nous avons articulé notre étude sur un méta-cadre d’analyse que constitue le cadre Contextualiste de Andrew Pettigrew. Cette thèse présente les résultats de nos analyses et les contributions théoriques et managériales que celles-ci impliquent. Elle nous aide à comprendre comment une innovation organisationnelle radicale devient la référence dans l’administration publique. Finalement, elle présente les conditions dans lesquelles une réforme organisationnelle initiée par un leader public s’est réalisée dans l’administration publique fédérale belge. [less ▲]

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See detailLe corps féminin à l'agenda de la transition tunisienne : de la lutte féministe à la colonialité du genre. La construction des problèmes publics autour du corps de la femme à partir de trois cas d'étude.
Luceno Moreno, Marta ULiege

Doctoral thesis (2018)

The woman’s body offers a breeding ground for ideological battles, political quarrel and power struggle. Since the early days of the transition in Tunisia, women condition was put at the heart of the ... [more ▼]

The woman’s body offers a breeding ground for ideological battles, political quarrel and power struggle. Since the early days of the transition in Tunisia, women condition was put at the heart of the public debate dealing with the remodelling of the country, often through women body issues. This research work analyses the process of social construction of problems and how women issues are put on the agenda, following three different bodies: the veiled body of munaqabas, from Manouba University, who vindicate the right to clothing; the outraged body of Meriem Ben Mohamed, raped by two policemen, who faces legal actions for outraging public decency; lastly the exhibited body of Amina – confined for abusing the sanctity of cemetery – who bared her breasts with feminists claims. On the basis of these three case studies, the research notes that feminine corporeality operates like a catalyst for the construction of public problems in postcolonial and transitional context, narrowly understood like a window political opportunity. This context goes through a political and social bipolarization – between islamists and progressives’ policies – and under the influence of neocolonialism, more specifically the coloniality of power, gender and media. [less ▲]

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See detailOCCUPÉS ET OCCUPANTS. LA POPULATION LUXEMBOURGEOISE ET LES TROUPES ALLEMANDES 1914-1918.
Seiwerath, Richard ULiege

Doctoral thesis (2018)

Our thesis deals with the occupation of the Grand Duchy of Luxembourg during the First World War. Our main concern was to show the organisation of this occupation and the life of the population during ... [more ▼]

Our thesis deals with the occupation of the Grand Duchy of Luxembourg during the First World War. Our main concern was to show the organisation of this occupation and the life of the population during this period. We focus on the following topics: neutrality, military aspects and administrative organization, confiscations, daily life, Pan-German policy and the evolution of the economy. [less ▲]

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See detailCrashworthiness of offshore wind turbine jackets based on the continuous element method
Pire, Timothée ULiege

Doctoral thesis (2018)

Nowadays, the offshore wind industry is expanding fast and many wind farms will be built in the near future. For every new project, a complete collision risk analysis is required. Usually, the ... [more ▼]

Nowadays, the offshore wind industry is expanding fast and many wind farms will be built in the near future. For every new project, a complete collision risk analysis is required. Usually, the crashworthiness of an offshore structure is assessed with nonlinear finite element simulations that provide accurate results but are time-demanding. Such approach is relevant in the final design but is not suitable at pre-design stage for which hundreds or sometimes thousands of collision scenarios have to be investigated. The purpose of this PhD thesis is thus to develop simplified semi-analytical formulations to compute quickly the resistance of an offshore wind turbine jacket impacted by a ship. [less ▲]

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See detailModel and parameter identification through Bayesian inference in solid mechanics
Rappel, Hussein ULiege

Doctoral thesis (2018)

Predicting the behaviour of various engineering systems is commonly performed using mathematical models. These mathematical models include application-specific parameters that must be identified from ... [more ▼]

Predicting the behaviour of various engineering systems is commonly performed using mathematical models. These mathematical models include application-specific parameters that must be identified from measured data. The identification of model parameters usually comes with uncertainties due to model simplifications and errors in the experimental measurements. Quantifying these uncertainties can effectively improve the predictions as well as the performance of the engineering systems. Bayesian inference provides a probabilistic framework for quantifying these uncertainties in parameter identification problems. In a Bayesian framework, the user's initial knowledge, which is represented by a probability distribution, is updated by measurement data through Bayes' theorem. In the first two chapters of this thesis, Bayesian inference is developed for the identification of material parameters in elastoplasticity and viscoelasticity. The effect of the user's prior knowledge is systematically studied with respect to the number of measurements available. In addition, the influence of different types of experiments on the uncertainty is studied. Since all mathematical models are simplifications of reality, uncertainties of the model itself may also be incorporated. The third chapter of this thesis presents a Bayesian framework for parameter identification in elastoplasticity in which not only the uncertainty of the experimental output is included (i.e. stress measurements), but also the uncertainty of the model and the uncertainty of the experimental input (i.e. strain). Three different formulations for describing the model uncertainty are considered: (1) a random variable which is taken from a normal distribution with constant parameters, (2) a random variable which is taken from a normal distribution with an input-dependent mean, and (3) a Gaussian random process with a stationary covariance function. In the fourth chapter of this thesis, a Bayesian scheme is proposed to identify material parameter distributions, instead of material parameters. The application in this chapter are random fibre networks, in which the set of material parameters of each fibre is assumed to be a realisation from a material parameter distribution. The fibres behave either elastoplastically or in a perfectly brittle manner. The goal of the identification scheme is to avoid the experimentally demanding task of testing hundreds of constituents. Instead, only 20 fibres are considered. In addition to their material randomness, the macroscale behaviours of these fibre networks are also governed by their geometrical randomness. Another question aimed to be answered in this chapter is therefore is `how precise the material randomness needs to be identified, if the geometrical randomness will also influence the macroscale behaviour of these discrete networks'. [less ▲]

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See detailEffects of tree species diversity and drought on ecosystem functioning in a young forest
Rahman, Md Masudur ULiege

Doctoral thesis (2018)

Warmer and drier conditions are expected globally and regionally in the future due to climate change. In Belgium, a 50% decrease in summer precipitations and an increase in winter precipitations are ... [more ▼]

Warmer and drier conditions are expected globally and regionally in the future due to climate change. In Belgium, a 50% decrease in summer precipitations and an increase in winter precipitations are expected. The drier conditions have the potential to influence forest ecosystem functioning, both aboveground and belowground. Further, more drought events could result in more frequent soil drying-rewetting events, which could influence the CO2 emissions (“Birch effect”). Mature forests are already experiencing adverse effects of climate change on tree growth, tree mortality and species composition. Studies suggested that ecosystems with higher tree species diversity could be more resistant and resilient to stress conditions, such as drought. Therefore, mixed planting may be an option to mitigate drought effects to forest ecosystems. The overall objective of this thesis was to assess the combined effects of tree species admixture and drought on different above- and belowground processes in a young forest plantation. In this study, combined effects of mixed planting and precipitation reduction (hereafter “drought”) on different above- and belowground processes around central oak (Quercus robur. L.) and beech (Fagus sylvatica L.) trees were investigated in 6-7 years old plantations (FORBIO). Oak and beech were planted in monocultures or admixed with 1-3 other functionally dissimilar tree species (tree species admixture gradient from 1 to 4). Three drought and three control plots (3 m × 3 m) around oak and beech trees were established at every admixture levels. Rainout shelters were installed in drought plots to intercept about 50% of the precipitation. Different aboveground variables such as plant growth, leaf traits, crown damage and belowground variables such as soil organic matter decomposition, nutrient availability, microbial biomass, C and N mineralization were measured over two growing seasons. Further, tree species admixing and drought legacy effects on soil microbial biomass and activity were measured under oak. Tree species admixing influenced different variables but the effects were not consistent between oak and beech. Tree species admixing reduced the height and increased the specific leaf area of beech, but did not influence any of the belowground variables measured. For oak, reduced crown damage from pests and pathogens, decreased leaf Al, Na and Zn contents, and increased soil N and total exchangeable cations were observed with higher tree species admixture level. Further, tree species admixing to oak influenced soil microbial community composition, and drought legacy reduced soil microbial biomass, soil respiration and bacterial growth but not fungal growth rates. Upon soil drying and rewetting, tree species admixing to oak did not influence bacterial growth and soil respiration rates but drought legacy reduced both bacterial growth and soil respiration. There were significant interactions between tree species admixing and drought for several variables such as organic matter decomposition, leaf Cu and N contents, net nitrification, potential respiration, MBC, metabolic potential of bacteria, qmic fungal to bacterial growth ratio etc. These interactions were mainly driven by the drought effects on monocultures and two species mixtures, indicating that tree species admixtures had offset the drought effects in three and four tree species mixture. Results from this study suggest that both tree species admixing and drought have the potential to influence ecosystem processes in young forests. Results also indicate that tree species admixing could offset the effects of drought on different ecosystem processes, thus stabilize ecosystem process under drought. Further, drought and drought legacy may reduce soil microbial activity, hence drought followed by precipitation (drying-rewetting) would not increase the CO2 emissions from soils. Overall, both oak and beech could benefit from admixing of functionally dissimilar tree species. Therefore, planting oak and beech in mixtures could be an option for forest management in the face of climate change. [less ▲]

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See detailDes doigts et des nombres. Utilisation d'outils d'analyse du mouvement pour étudier le rôle des doigts dans l'apprentissage de la cardinalité : une étude pilote.
Neveu, Maëlle ULiege

Master's dissertation (2018)

Contexte : Partout dans le monde, des milliers d’enfants utilisent leurs doigts pour compter. C’est à partir de ce constat que de nombreux professionnels ont questionné leur rôle dans les habiletés ... [more ▼]

Contexte : Partout dans le monde, des milliers d’enfants utilisent leurs doigts pour compter. C’est à partir de ce constat que de nombreux professionnels ont questionné leur rôle dans les habiletés numériques précoces telles que la cardinalité. A notre tour, nous avons exploré cette problématique à travers trois questions de recherches. Tout d’abord, nous avons questionné le rôle que joue le symbole digital sur la réalisation d’une tâche cardinale en production. Puis, nous avons interrogé la valeur prédictive des habiletés digitales sur la cardinalité ainsi que sur les autres habiletés numériques précoces. Enfin, nous avons étudié la présence de microactivations dans les muscles de la main des enfants, lors de tâches numériques au cours desquelles leurs mains étaient immobilisées volontairement. Méthodologie : Pour répondre à ces questions, nous avons rencontré, par deux fois, 16 enfants âgés de 3 à 5 ans. La première rencontre a été consacrée à l’évaluation de leurs habiletés numériques. Les compétences digitales des enfants ont été évaluées, lors d’une seconde séance, au moyen d’un outil d’analyse du mouvement en 3 dimensions (3D). Au cours de cette même séance nous avons relevé, par l’intermédiaire de capteurs de pression, les micro-pressions exercées par les enfants lors de tâches numériques réalisées alors que leurs mains étaient immobilisées. Résultats et discussion : Les résultats relatifs à notre première question de recherche ne nous ont pas permis de mettre en évidence le rôle facilitateur du symbole digital dans la réalisation d’une tâche cardinale en production. Il semble cependant difficile d’adopter une position ferme dans le débat qui anime la littérature à ce sujet sans avoir investigué davantage cette question. L’évaluation préalable de l’outil 3D, utilisé pour répondre à notre seconde question de recherche, a montré les apports qu’il assurait en comparaison aux protocoles papiers légitimant ainsi son utilisation dans cette étude. Par cet outil, la valeur prédictive des habiletés motrices fines sur les compétences cardinales et arithmétiques des enfants a pu être mise en exergue, une fois l’influence de l’âge contrôlé. Les compétences de coordination digitales semblent montrer la valeur prédictive la plus importante ce qui laisse à penser que le comptage digital jouerait un rôle non négligeable dans le développement de ces compétences. Enfin, les résultats relatifs à notre troisième question de recherche n’ont pas permis de souligner la présence de micropressions lors des tâches numériques proposées. Ces derniers résultats ont été discutés au regard des limites méthodologiques relevées. [less ▲]

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See detailLes chutes et la peur de tomber selon une perspective longitudinale chez les personnes âgées de 65 ans et plus
Léonard, Christina ULiege

Master's dissertation (2018)

Introduction : Dans la population âgée, les chutes et la peur de tomber constituent, tous deux, des problèmes prééminents de santé publique. Effectivement, ces deux phénomènes, de nature multi-déterminée ... [more ▼]

Introduction : Dans la population âgée, les chutes et la peur de tomber constituent, tous deux, des problèmes prééminents de santé publique. Effectivement, ces deux phénomènes, de nature multi-déterminée, sont fréquents chez les personnes âgées et entraînent diverses conséquences négatives (tant sur le plan physique que psychologique) ainsi que des coûts corollaires. Objectifs : Analyser les relations entre différentes variables explicatives (de nature sociodémographique, psychologique et cognitive) et les chutes, d’une part ainsi que la peur de tomber d’autre part. Design : Étude longitudinale d’une durée de 2 années auprès de 92 personnes âgées de 65 ans et plus vivant à domicile. Méthode : Un recensement rétrospectif des chutes portant sur un intervalle de 12 mois a été entrepris au commencement de l’étude (temps 0) ainsi qu’un suivi téléphonique trimestriel durant le follow-up. La peur de tomber a fait l’objet d’une évaluation aux temps 0 et 2 (fin de l’étude) par le biais de la FES-I. Les participants ont également effectué plusieurs épreuves neuropsychologiques aux temps 0 et 2 (Mémoire des chiffres, « RI-24 », Trail Making Test, test de Stroop, fluences verbales à induction phonémique et sémantique). Ils ont complété différents questionnaires d’auto-évaluation de l’humeur (GDS- 15 items et STAI-Y-B) ainsi que des mesures renvoyant au concept supra-ordonnant de vieillissement subjectif (AAQ, tâche de fluence verbale – 5 mots – et âge subjectif relatif à la santé physique et mentale). Des régressions logistiques binaires univariées et multivariées ont été effectuées. Conclusions : Premièrement, les résultats de notre étude laissent entendre que les chutes et la peur de tomber constituent chacun un facteur de risque pour l’autre (relations longitudinales). Certaines de nos hypothèses ont été corroborées (cf. supra) ou partiellement corroborées (par exemple : relations entre les variables ayant trait à l’humeur et les deux phénomènes d’intérêt) tandis que d’autres pas (par exemple : effet de l’âge sur les deux phénomènes d’intérêt) mais ont fait l’objet d’une réflexion dans le cadre de ce mémoire. Les apports originaux de notre étude concernent d’une part, notre tentative de mettre en relation le concept de vieillissement subjectif avec les deux phénomènes en question et d’autre part, celle de mettre en relation le fonctionnement cognitif avec la peur de tomber. Notre réflexion relative à des résultats (qui n’ont pas, pour une majorité, permis de corroborer nos hypothèses) invite à la réalisation de futures études à leur sujet. [less ▲]

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See detailLes conditions qualitatives d'un dispositif de formation intégrant le portfolio - Document de synthèse
Ignelzi, Audrey ULiege

Master's dissertation (2018)

Soutenir le développement de compétences des étudiants dans le contexte de l’alternance est un défi majeur ; les institutions scolaires et les institutions professionnelles sont souvent cloisonnées et le ... [more ▼]

Soutenir le développement de compétences des étudiants dans le contexte de l’alternance est un défi majeur ; les institutions scolaires et les institutions professionnelles sont souvent cloisonnées et le déficit de synergies entre ces « deux univers » n’est pas propice à l’apprentissage en profondeur. Pour relever ce défi, les coordinateurs du Master en alternance en Facility Management, avec le soutien d’une équipe de conseillers pédagogiques issus du LabSET, ont conçu et implémenté un portfolio en ligne destiné à soutenir le développement de compétences des étudiants tout en renforçant le lien entre l’enseignement et les entreprises. Mais à quelles conditions ce portfolio et le dispositif dans lequel il s’insère peut-il soutenir ce développement de compétences des étudiants ? Cette recherche qualitative a pour ambition de répondre à cette question à partir de l’analyse du dispositif tel qu’il a été aménagé dans le Master en Facility Management ainsi que des réflexions et des expériences partagées par six étudiants lors d’entretiens individuels semi-dirigés effectués bimensuellement durant trois mois et demi. Somme toute, 43 entretiens semi-dirigés ont été menés (30 entretiens au sens classique du terme et 13 entretiens d’explicitation) à propos de deux thématiques principales : les difficultés rencontrées et les perceptions de l’utilité. Cinq conditions que le dispositif de formation intégrant le portfolio doit satisfaire pour soutenir le développement de compétences ont été extraites de la littérature scientifique. L’évaluation de ces conditions, à partir des données empiriques, a abouti sur l’affinement et l’opérationnalisation de ces conditions ainsi que sur la formalisation et la conceptualisation de recommandations à l’intention des acteurs de la formation en alternance : superviseurs en entreprise, personnes de référence en milieu scolaire, équipe encadrante et conseillers pédagogiques. Comment orienter le programme de formation vers le développement de compétences ? Comment optimiser l’accompagnement des étudiants ? Comment définir les modalités d’évaluation du portfolio ? Comment soutenir la construction de la vision du métier et la démonstration du développement de compétences ? Les réponses à ces questions, ancrées dans des données de terrain, offriront des pistes aux acteurs pour soutenir le développement de compétences de leurs étudiants à travers la mise en œuvre d’un dispositif de formation intégrant le portfolio. [less ▲]

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See detailIdentification de nouvelles fonctions des métalloprotéases par détermination de leur répertoire de substrats : Applications aux aminoprocollagène peptidases
Leduc, Cédric ULiege

Doctoral thesis (2018)

Manuscrit de thèse + Tableaux supplémentaires au manuscrit .

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See detailEffet des caractéristiques pédologiques et des pratiques agricoles sur la disponibilité du phosphore dans les sols de Wallonie
Renneson, Malorie ULiege

Doctoral thesis (2018)

Essential element for plant growth, phosphorus (P) is also a problematic element, due to the limitation of mineral resources but also the environmental problems which can be caused, as eutrophication. For ... [more ▼]

Essential element for plant growth, phosphorus (P) is also a problematic element, due to the limitation of mineral resources but also the environmental problems which can be caused, as eutrophication. For several years, scientific studies have focused on finding other sources of P and making this element more available for plants. However, improving the bioavailability of P involves a better knowledge of the stocks present in Walloon soils but also a better identification of factors governing its mobility for plants and the environment. This thesis focused on knowing P content and behaviour in Walloon soils and the impact of agricultural practices but also evaluating the P indicators. The first part of the thesis characterized the geochemical background and agricultural practices on soil P stocks and its mobility. Homogeneous and specific groups of soils have been defined. It permitted to characterize the geopedochemical signature of the main Walloon parent materials as well as the influence of the land use. P management should be reflected on the basis of these soil groups. Regression equations have been defined to estimate soil total P, a parameter that is rarely analyzed but necessary. In a second step, the influence of organic and inorganic inputs on the mobility of P was evaluated in the short-term under controlled conditions but also in the long-term thanks to experimental plots. A comparable effect of these different inputs has been observed in silty soils and the potentiality of organic matter in phosphate fertilization demonstrated. Moreover, it permitted to observe release kinetics of P in these soils. Finally, agricultural and environmental indicators that can be used in the Walloon Region have been evaluated according a lot of parameters. The efficiency of the available P indicator currently used as an agronomic indicator in Walloon soils has been demonstrated. This indicator has a good benefit / disadvantage ratio. In addition, it is well correlated with the degree of phosphorus saturation, an environmental indicator expressing the risk of P loss to the environment. Developed in acidic sandy soils, this indicator can also be used in the Walloon soils, but only after adaptations to the Walloon pedological context. To conclude, in view of the important differences between the geopedological regions, it is essential to take into account these specificities in the management of the P in the Walloon territory. In addition, reflections must be carried out to improve the use of organic matters and better enhance soil organic P, which is important in some soils. [less ▲]

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See detailCrise de microfinance et Scoring de crédit : application de la régression logistique au risque de contrepartie des microentreprises dans le système financier décentralisé du Nord-Kivu.
Kambale Kapitene, Marcel Héritier ULiege

Master's dissertation (2018)

La microfinance congolaise a connu une ascension fulgurante en début des années 2000. Beaucoup plus rependue à l’Est du pays, et notamment dans le Nord-Kivu, elle connaît une chute brutale que d’aucuns ... [more ▼]

La microfinance congolaise a connu une ascension fulgurante en début des années 2000. Beaucoup plus rependue à l’Est du pays, et notamment dans le Nord-Kivu, elle connaît une chute brutale que d’aucuns ont très vite qualifié de « crise de la microfinance en RDC », la liant, par concomitance de survenance, à la grande crise financière qui a secoué les marchés financiers entre 2007 et 2008, voire 2009. Au fond, les institutions de microfinance étaient en déphasage des époques et des pratiques. Nombreuses d’entre elles avaient – par effet de concurrence, de course obstinée à la rentabilité, d’inexpérience en matière de gestion des risques – multiplié les agences et des volumes massifs d’octrois de crédits ; sans en avoir préalablement mesuré l’impact, en terme de risque, sur leur portefeuille. La boite à pandore a vite explosé, entraînant des dizaines d’entre elles à disparaitre. Outre le faible encrage en terme de gestion des risques propres aux institutions de microfinance, l’épine dans l’œil de cette autre forme de business de la misère au Nord-Kivu aura aussi été son décalage d’avec le cadre règlementaire et une forte concentration en plein « économie de la guerre », octroyant des crédits à des microentreprises et individus, parfois très peu maîtrisés. Elles n’ont pas tardé à faire défaut, par effet de contagion ou tout simplement par déphasage vis-à-vis des normes prudentielles et volumes importants d’encours irrécouvrables. Pour comprendre les faits et pouvoir suggérer une des voies de sortie, cette étude aborde une double échelle : une description analytique des causes internes de la crise dite de microfinance et propose un modèle de prédiction de défaut de crédit sur base des scores générés par la régression logistique. Les résultats montrent que les vraies causes de la crise ont été plutôt internes et surtout liées à la distorsion réglementaire. [less ▲]

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See detailIdentifying primate parasites in the Ecuadorian Amazon: A tool for Public Health and Conservation
Martin, Sarah ULiege

Doctoral thesis (2018)

Non-human primates (NHPs) have coevolved with parasites. However factors such as loss and fragmentation of habitat, pet trade or bushmeat hunting have changed the diversity and intensity of these ... [more ▼]

Non-human primates (NHPs) have coevolved with parasites. However factors such as loss and fragmentation of habitat, pet trade or bushmeat hunting have changed the diversity and intensity of these parasites and exposed NHPs to novel parasites from humans, livestock and wildlife. This study focused on gastrointestinal parasites in New World monkeys. Indeed, gastrointestinal parasites can heavily impact the health and behavior of NHPs, and most studies on NHPs’ parasites have focused on Old World primates. Therefore, our study aimed to fill some gap of this research topic on New World monkeys. In order to accomplish this, we used two techniques to determine the diversity of gastrointestinal parasites in the Western Amazon of Ecuador, and see if they are a potential reservoir of zoonotic parasites.After reviewing the various classes of parasites affecting NHPs, we studied two groups of Capuchins (Cebus albifrons), one captive and one free-ranging, where we looked how parasitism is affected by host-intrinsic and extrinsic factors. We found microscopically 6 genera of gastrointestinal parasites, the most prevalent being Strongyloides sp. (76.9%), followed by Hymenolepis sp. (38.5%) and Prosthenorchis elegans (11.5%). Zoonotic parasites such as Entamoeba histolytica/nuttalli/dispar/moskovskii/ and Capillaria sp. where found only in a minority of the animals tested (3.8%). Adults (6) showed higher parasite richness than the subadults (5) and juveniles (3). Faecal egg/cyst counts were not significantly different between captive and free-ranging individuals, or between sexes or age groups. The free-ranging group had a little higher prevalence than the captive group, but this difference was not significant, maybe due to limited sampling. Additionally, our study demonstrated that a serial sampling of 3 samples per individual significantly increased the test sensitivity. Secondly, we tried to correlate parasites richness and intensity with behaviour as an intrinsic factor. For this, we focused on two captive groups of Woolly monkeys (Lagothrix lagotricha), one living in a small enclosure (SE) and the other in a large one (LE). We correlated the size of the enclosure, parasite transmission and social contact through social network analysis. In both groups, an increased number of social contacts per individual and a higher clustering coefficient were associated with a higher parasite richness. Adults (2.3), subadults (3) and juveniles (2.5) did not differ in number of parasites harboured (F = 3.321, p = 0.078), but between sexes, females (3) harboured more parasites than males (2) (F = 17.481, p = 0.002). The SE group harboured slightly more parasites (6) than the LE group (5), but this difference was not statistically significant (F = 4.601, p = 0.058). However the FEC for Strongyloides sp. was significantly higher in the SE group (range 1 to 477) than in the LE group (range 0 to 12) (F = 6867.753, p < 0.001). Thus a smaller enclosure seems to be consistent with a higher number of parasites in individuals. As for the first study with capuchins, if we increase sampling maybe parasite richness can increase as well. We also found that parasite richness of central adult individuals increased the parasite load within the group. Therefore, maintaining the health of central individuals may be an obvious and practical method to increase group health. Finally, we evaluated the presence of gastrointestinal parasites in two populations of NHPs (captive and free-ranging) including ten NW monkey species: Alouatta seniculus, Ateles belzebuth, Callicebus discolor, Callicebus luficer, Cebuella pygmaea, Cebus albifrons, Cebus apella, Lagothrix lagotricha, Saguinus fuscicollis, and Saimiri sciureus). We then focused on the molecular identification of Entamoeba histolytica in these ten species to assess the role of these primate populations as potential reservoirs of zoonotic parasites. Microscopic identification allowed the identification of 10 parasites of gastrointestinal parasites and molecular identification (conventional PCR) pointed two individual woolly monkeys who had Entamoeba histolytica. We also identified Entamoeba nuttalli (the NHP Entamoeba), again in a woolly monkey. In our study, in accordance with other studies, we found that host biology (such as age, sex, and primate species) may influence the parasite diversity harboured. Most parasites found in our study where also found in OW monkeys, but some were specific to the neotropical area. Most parasites in our study are widely distributed and have numerous hosts, while others are restricted to some NHPs. Host age and sex may influence parasite richness, but their effect varies depending on the parasite species and on the NHP host. The sensitivity to parasite infestation of NHPs captive or in close contact with humans is related to several extrinsic factors (home range overlap, disturbed habitat, human contact, poor environmental enrichment, contaminated food, among others) and intrinsic factors (social contacts) that increase the diversity and prevalence of parasites. However, free-ranging NHPs have developed strategies such as self-medication to decrease the number of parasites or alleviate their effect. Although we did not observe this kind of behaviour, we observed ad libitum in captive Cebus albifrons and Ateles belzebuth sequences of rubbing onions and eating sand, which is also considered as self-medication behaviour. Our study also demonstrated the importance of a serial sampling, which allows to find a higher number of parasite species per NHP species. However, we did not find some of the regular parasites found in other studies, maybe because of the microscopic technique employed. Molecular identification also increased the prevalence of Entamoeba sp., from 14.7 % to 57.5 %. As a contribution to regulation perspectives, we proposed a series of strategies such as environmental education for tourists and local population itself, or such as technical training for caretakers, or basic health major procedures such as treatment administration to implement in NHPs facilities or in communities in close contact with NHPs. Finally, one general recommendation should be essential for Ecuador, and this is to establish a national network for wildlife diseases’ surveillance to enhance the detection of infectious and zoonotic diseases and protect wildlife populations, domestic animals and humans. [less ▲]

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See detailEarly life programming of piglets' microbiota and gut health by maternal dietary fibre supplementation
Leblois, Julie ULiege

Doctoral thesis (2018)

Post-weaning diarrhoea (PWD) is a widespread disease causing loss of weight and mortality of the piglets. To cure or prevent PWD, the treatment of pigs with antibiotics is frequent. The overuse of these ... [more ▼]

Post-weaning diarrhoea (PWD) is a widespread disease causing loss of weight and mortality of the piglets. To cure or prevent PWD, the treatment of pigs with antibiotics is frequent. The overuse of these substances led to the appearance of multi-resistant bacteria, raising public health issues. Thus, finding sustainable alternatives to antibiotics for PWD curation is of major importance. Most research focusses on the use of substances like prebiotics able to affect the microbiota of the piglets, as gut microbiota is responsible for the maturation of the intestinal immune system. Promoting a beneficial microbiota as early in life as possible is a good strategy for a better future health and a lower prevalence of PWD. Our hypothesis was that using dietary fibres (wheat bran and resistant starch) in the diet of sows would alter their microbiota and in turn affect their piglets’ microbiota and future health. In addition, the ability of the two fibre sources to alter milk composition, also affecting piglets’ performances and health, was tested. This hypothesis was challenged with two animal experiments. Results indicated that wheat bran (WB) and resistant starch (RS) had the ability to alter sows’ microbiota during gestation but not anymore during lactation, possibly limiting a differential microbial transfer to their offspring. These two dietary fibre slightly altered milk composition. Maternal wheat bran had the ability to increase the villus height and villus to crypt ratio in the small intestine of the progeny, while resistant starch increased the gene expression of tight junction proteins at weaning. These two fibre sources included in a high level in sows’ diets did not affect their performance or their piglets’, making their use in animal diets realistic. A second objective of the thesis was to unravel whether the diet of sows could program the metabolism of piglets for later life, using them as model for human. For this, piglets were challenged with a high fat diet in order to induce low-grade inflammation and/or obesity symptoms. After 7 weeks on a high fat diet, piglets had an increased backfat thickness and higher serum cholesterol levels. The main findings are that feeding sows resistant starch increased the total sum of short-chain fatty acids (SCFA) production in the caecum and colon of their progeny, which is beneficial but did not affect the microbiota of the pigs. Moreover, maternal RS diet seemed to increase the barrier function of the colon due to a higher gene expression of tight junction proteins while the maternal effects on intestinal inflammation were contradictory for TNF-α and IFN-γ. It seems thus that the maternal diet had the ability to decrease gut permeability. However, the high fat diet did not alter the microbiota of the pigs, nor was it affected by the maternal diet. In conclusion, using dietary fibre in sows’ diet had the ability to alter their own microbiota during gestation and milk composition, but the impact on the piglet’s microbiota was rather limited. It could be thus interesting to use these diets on piglets’ themselves after birth to promote the establishment of beneficial bacteria. Although effects on the microbiota were limited, the maternal diet seemed to affect some aspects of the health of their progeny in later life. [less ▲]

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See detailCONTRIBUTION TO EPISTASY MAPPING METHODS THROUGH THE USE OF NON-PARAMETRIC METHODOLOGY
Abo Alchamlat, Sinan ULiege

Doctoral thesis (2018)

Introduction These last years have seen the emergence of a wealth of genetic information at the molecular level. Some of the main recent breakthroughs in biology originate from this new knowledge ... [more ▼]

Introduction These last years have seen the emergence of a wealth of genetic information at the molecular level. Some of the main recent breakthroughs in biology originate from this new knowledge, allowing application of new strategies in many fields of the biological research. Although approaches targeting the association between phenotypic characteristics and DNA variations have been successful, many elements in the genetic landscape of the studied traits are still unknown and uncharacterized. A track to new findings, potentially useful for a better understanding of complex determinisms, is the detection of interactions between genomic regions affecting the traits of interest rather than single locus associations. While the detection of such interactions has been the focus of many methods, and despite some successes of these methods to solve difficult problems and to detect some of these genetic interactions, there is currently no gold standard method able to detect interactions in all situations, and the relative performances of these methods remain largely unclear. This thesis is a contribution to this field of interactions mapping:in the first study, we propose a novel approach combining K-Nearest Neighbors (KNN) and Multi Dimensional Reduction (MDR) methods for the detection of gene-gene interactions as a possible alternative to existing algorithms, especially in situations where the number of involved determinants is high. In the second study, we propose another strategy based on the principle of the aggregation of experts, where the experts would be a set of popular published methods. Results The results obtained in the first study on both simulated data and real genome-wide data demonstrate some of the features that make KNN-MDR interesting in terms of accuracy and power: in many cases, it significantly outperforms its recent competitors. More specifically, the analyses on a real large dataset demonstrate the feasibility of scans using a large number of markers, as opposed to MDR where the computer burden explodes with the number of markers (when it simply increases linearly with KNN-MDR). This might for example allow highlighting interactions between markers far apart on the genomic map (trans-interactions), while some strategies propose to restrict the scans to close-by markers (cis-interactions) or to markers with significant marginal effects to reduce the amount of computations. For the second study, we also show that aggregating methods results is a strategy with interesting features for detecting epistatic interactions. Experimental results, based again on simulated and real genome-wide data, show that the aggregated predictor can produce better performances, in terms of statistical power and false positive rates, than each individual predictor to detect genetic interactions. It is consequently a useful addition to the various methods available to tackle this complicated problem. Conclusion and Perspectives In this dissertation, we focused on investigating and developing non-parametric statistical methods aiming at the detection of genetic interactions. We have shown that our novel methods complement, and sometimes improve, existing approaches used to detect genetic interactions in simulated and real datasets. The presented methodologies (KNN-MDR and aggregation of experts) are valuable in the context of loci and interaction mapping and can enhance the understanding of the biological mechanism underlying traits of interest, including diseases. More precisely, the new knowledge gained using these methodologies can assist in the prediction of clinical diseases and can contribute to provide new therapeutic opportunities. To take further steps to these appealing perspectives, a first objective could be to implement a better version of the KNN-MDR software. The improvements could be on the overall performance of the software (optimization of the time-consuming parts of the program, parallelization), but also on the improvement of the “user-friendliness” of the program. This would involve an easier (and maybe automated) tuning of the parameters allowing an optimal detection power. These parameters include: the optimal sizes of the windows - which are dependent on the studied population, the markers density, the LD pattern, the optimal size of the neighborhoods to be considered, the pre-selection of markers in the early phase of large dataset analyses, the used distance measure or the adaptative selection scheme for the selection of markers in large studies, among others, the use of other types of genomic variants (microsatellites, copy number variations, sequencing data). Another potential track would be to use a priori information on the interactions: this could be by using the results of previous studies, or by exploiting the known information on gene networks.   [less ▲]

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See detailSoil structure exploration and measurement of its macroscopic behavior for a better understanding of the soil hydropedodynamic functionalities
Smet, Sarah ULiege

Doctoral thesis (2018)

Air permeability and water conductivity are fundamental physical properties when it comes to the soil functions across the environment. The water conductivity and the air permeability as functions of the ... [more ▼]

Air permeability and water conductivity are fundamental physical properties when it comes to the soil functions across the environment. The water conductivity and the air permeability as functions of the soil’s degree of saturation (K(θ) and ka(ɛ), respectively) are only discretely measurable, and the use of models is necessary to obtain continuous expressions of these functions. Most models however consider the soil pore network structure as a fitting parameter although it is public knowledge that K(θ) and ka(ɛ) depend mostly on the soil microstructure, which is, none the less, unique between samples with homogeneous texture. New ways of studying K(θ) and ka(ɛ) are needed. The direct soil pore space visualization is a promising avenue to lead us to objectifying soil physics. The X-ray microtomographic technique (X-ray µCT) is now widely used by soil scientists and delivers 3D grayscale images of objects composed by materials of different densities. When dealing with a porous medium such as the natural soil, the X-ray µCT images need to be cautiously and expertly processed to obtain realistic feature quantification. A parallel, but however perquisite, objective of this dissertation is to statistically compare the effects of various image processing on the final X-ray µCT image features quantification. We simulated grayscale images to be processed to conclude about the image processing methodology we applied in our research. The overall objective of this dissertation is to explore the relationships between one microscopic soil structure (the volume of the smallest visible pore is 0.0004 mm³) and its macroscopic functionalities, such as its water conductivity and air permeability. More specifically, we confirmed that the use of 3D X-ray µCT data enables a better estimation of the soil water retention curve near saturation through the identification of the largest soil pores. These are indeed often by-passed with pressure plate’s laboratory measurements because of various artefacts. We also identified microscopic pore space morphological parameters that explained the soil saturated hydraulic conductivity, and microscopic porosity distribution measures that explained the soil air permeability. The final X-ray µCT image features quantification depends on the applied image processing, as stated, but also, clearly, on the image resolution. We concluded that working with a higher resolution would not necessarily lead to a higher degree of knowledge because resolution is sample-size dependent, and one pore size distribution could moreover be sufficiently visible at low resolution. We however observed that the pore network morphological and topological connectivity increases with resolution. Finally, we highlighted the imperfections of the capillary theory applied to soil through scanning the same soil samples at various water contents. As hypothesized, the pore network connectivity seems to play an important role in the pore accessibility to draining. After having studied the effects of the soil pore network structure on the soil hydrodynamic properties, we turned the question around and evaluated the effects of the chemical soil composition (organic carbon and free forms of iron) on the very same soil pore network structure. This dissertation therefore discusses the advantages and limitations of the use of X-ray microtomography to study soils for a more realistic understanding of the soil hydropedodynamic processes. [less ▲]

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See detailThe human factor in the energy performance assessments for renovation strategies of existing urban houses in Wallonia
Monfils, Stéphane ULiege

Doctoral thesis (2018)

In order to reach energy efficiency at any level, the importance of the human factor has to be acknowledged. On one hand, efficient solutions (regarding, for example, building energy consumptions) have to ... [more ▼]

In order to reach energy efficiency at any level, the importance of the human factor has to be acknowledged. On one hand, efficient solutions (regarding, for example, building energy consumptions) have to be implemented by an authority who understands the complexity of the urban context and its impacts on the environment; on the other hand, it is important to improve citizens’ awareness of their environmental impact and to lead them to use available solutions to their full potential. In the field of residential use of energy, people are therefore a crucial parameter of both the problem and its solution. The EPC has been designed by authorities to “provide clear information about the energy performance of a building”, in order to influence the real-estate market, promote energy performance improvements and help build up comprehensive benchmarking databases, fundamental for shaping strategies on a local or regional level. The EPC, however, offers in return of a 200€ visit, results that are often too distant from reality and difficult to understand for the lay person. “Consumers do not understand CO2 or kWh”. They do not understand “primary energy” either, given that their only knowledge of their energy consumption are the final energy bills. The procedure might be necessary, but the general picture shows a great opportunity remaining underexploited, a potential driver to reducing energy consumption and CO2 emissions, surrounded by barriers and obstacles that render its use all the more difficult. While appreciating the necessity of presenting a “legal” result as a comparison base, following the approved standardized calculation method, it is believed that the input data used in the quasi-steady state calculation method could be used to display complementary results. Additional data on the household’s composition, their practices and behaviours related to energy consumption, as well as a more accurate search in the description of the energy system, could help close the gap between real and theoretical consumptions, allowing future owners to better understand and appropriate the EPC results, foresee a rough monthly energy bill, and make better decisions for their real-estate renovation ambitions. This PhD-thesis therefore first sets the context of residential energy use in Wallonia, before questioning the uncertainty parameters of the certification procedure. A questionnaire, built for this research, allowed the interview of 16 case studies, and the collection of their energy-related behaviours and practices. Based on the existing inputs, protocol and global philosophy of the EPC procedure, a modification of the calculation method is suggested in order to integrate the answers to the questionnaire. The results of the many simulations, and those of the sensitivity analysis on the modifications, are presented in the second part of this thesis, followed by conclusions and perspectives for the future. [less ▲]

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See detailAdvancing agricultural monitoring for improved yield estimations using SPOT-VGT and PROBA-V type remote sensing data
Durgun, Yetkin Özüm ULiege

Doctoral thesis (2018)

Accurate and timely crop condition monitoring is crucial for food management and the economic development of any nation. However, accurately estimating crop yield from the field to global scales is a ... [more ▼]

Accurate and timely crop condition monitoring is crucial for food management and the economic development of any nation. However, accurately estimating crop yield from the field to global scales is a challenge. According to the global strategy of the World Bank, in order to improve national agricultural statistics, crop area, crop production, and crop yield are key variables that all countries should be able to provide. Crop yield assessment requires that both an estimation of the quantity of a product and the area provided for that product should be available. The definition seems simple; however, these measurements are time consuming and subject to error in many circumstances. Remote sensing is one of several methods used for crop yield estimation. The yield results from a combination of environmental factors, such as soil, weather, and farm management, which are responsible for the unique spectral signature of a crop captured by satellite images. Additionally, yield is an expression of the state, structure, and composition of the plant. Various indices, crop masks, and land observation sensors have been developed to remotely observe and control crops in different regions. This thesis focuses on how much low spatial resolution satellites, such as Project for On Board Autonomy Vegetation (PROBA V), can contribute to global crop monitoring by aiding the search for improved methods and datasets for better crop yield estimation. This thesis contains three chapters. The first chapter explores how an existing product, Dry Matter Productivity (DMP), that has been developed for Satellites Pour l’Observation de la Terre or Earth observing Satellites VeGeTation (SPOT VGT), and transferred to PROBA V, can be improved to more closely relate to yield anomalies across selected regions. This chapter also covers the testing of the contribution of stress factors to improve wheat and maize yield estimations. According to Monteith’s theory, crop biomass linearly correlates with the amount of Absorbed Photosynthetically Active Radiation (APAR) and constant Radiation Use Efficiency (RUE) downregulated by stress factors such as CO2, fertilization, temperature, and water stress. The objective of this chapter is to investigate the relative importance of these stress factors in relation to the regional biomass production and yield. The production efficiency model Copernicus Global Land Service Dry Matter Productivity (CGLS DMP), which follows Monteith’s theory, is modified and evaluated for common wheat and silage maize in France, Belgium, and Morocco using SPOT VGT for the 1999–2012 period. The correlations between the crop yield data and the cumulative modified DMP, CGLS DMP, Fraction of APAR (fAPAR), and Normalized Difference Vegetation Index (NDVI) values are analyzed for different crop growth stages. The best results are obtained when combinations of the most appropriate stress factors are included for each selected region, and the modified DMP during the reproductive stage is accumulated. Though no single solution can demonstrate an improvement of the global product, the findings support an extension of the methodology to other regions of the world. The second chapter demonstrates how PROBA V can be used effectively for crop identification mapping by utilizing spectral matching techniques and phenological characteristics of different crop types. The study sites are agricultural areas spread across the globe, located in Flanders (Belgium), Sria (Russia), Kyiv (Ukraine), and Sao Paulo (Brazil). The data are collected for the 2014–2015 season. For each pure pixel within a field, the NDVI profile of the crop type for its growing season is matched with the reference NDVI profile. Three temporal windows are tested within the growing season: green up to senescence, green up to dormancy, and minimum NDVI at the beginning of the growing season to minimum NDVI at the end of the growing season. In order of importance, the crop phenological development period, parcel size, shorter time window, number of ground truth parcels, and crop calendar similarity are the main reasons behind the differences between the results. The methodology described in this chapter demonstrates the potentials and limitations of using 100 m PROBA V with revisiting frequency every 5 days in crop identification across different regions of the world. The final chapter explores the trade off between the different spatial resolutions provided by PROBA V products versus the temporal frequency and, additionally, explores the use of thermal time to improve statistical yield estimations. The ground data are winter wheat yields at the field level for 39 fields across Northern France during one growing season 2014–2015. An asymmetric double sigmoid function is fitted, and the NDVI values are integrated over thermal time and over calendar time for the central pixel of the field, exploring different thresholds to mark the start and end of the cropping season. The integrated NDVI values with different NDVI thresholds are used as a proxy for yield. In addition, a pixel purity analysis is performed for different purity thresholds at the 100 m, 300 m, and 1 km resolutions. The findings demonstrate that while estimating winter wheat yields at the field level with pure pixels from PROBA V products, the best correlation is obtained with a 100 m resolution product. However, several fields must be omitted due to the lack of observations throughout the growing season with the 100 m resolution dataset, as this product has a lower temporal resolution compared to 300 m and 1 km. This thesis is a modest contribution to the remote sensing and data analysis field with its own merits, in particular with respect to PROBA V. The experiments provide interesting insight into the PROBA V dataset at 1 km, 300 m, and 100 m resolutions. Specifically, the results show that 100 m spatial resolution imagery could be used effectively and advantageously in agricultural crop monitoring and crop identification at local – field level – and regional – the administrative regions defined by the national governments – levels. Furthermore, this thesis discusses the limitations of using a low resolution satellite, such as the PROBA V 100 m dataset, in crop monitoring and identification. Also, several recommendations are made for space agencies that can be used when designing the new generation of satellites. [less ▲]

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