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

Doctoral thesis (2015)

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

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

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See detailHistoire Evolutive de Rongeurs Holarctiques: Approche micro- & macroévolutive
Pisano, Julie ULg

Doctoral thesis (2015)

La biodiversité n’est pas stable dans le temps et l’espace. Elle évolue en réponse à différents facteurs. A l’échelle macroévolutive, les moteurs de diversité sont essentiellement les changements ... [more ▼]

La biodiversité n’est pas stable dans le temps et l’espace. Elle évolue en réponse à différents facteurs. A l’échelle macroévolutive, les moteurs de diversité sont essentiellement les changements tectoniques majeurs, climatiques globaux et environnementaux. Ils sont connus pour avoir façonné les patrons évolutifs de groupes d’espèces sur de grandes échelles spatiales et temporelles. A l’échelle microévolutive, les moteurs de diversité sont majoritairement liés à des forces évolutives telles que la mutation, la dérive génétique, la sélection ou la dispersion. Ils rythment l’évolution de la biodiversité populationnelle à une plus petite échelle spatiale et temporelle. Dans le cadre de cette thèse, le but a été de construire un cadre évolutif stable permettant de nous éclairer sur les processus évolutifs et/ou les facteurs qui ont rythmé l’histoire évolutive d’espèces et de populations de rongeurs. Pour étudier l’évolution de la biodiversité à l’échelle macroévolutive, nous avons pris comme modèle biologique la superfamille des Dipodoidea (Rongeurs : Myodonta). Groupe frère des Muroidea, la superfamille des Dipodoidea comprend trois grands groupes d’organismes : les sicistes (Sicistinae), les souris-sauteuses (Zapodinae) et les gerboises (Allactaginae, Cardiocraniinae, Dipodinae et Euchoreutinae). Dans la littérature, la superfamille des Dipodoidea comprend 51 espèces réparties dans 16 genres de six sousfamilles, toutes de la famille des Dipodidae mais cette classification basée essentiellement sur des données morphologiques est très controversée. Avant cette thèse, aucune phylogénie moléculaire des Dipodoidea n’avait été reconstruite. De plus, les Dipodoidea sont particulièrement intéressants pour tester divers scénarios biogéographiques étant donné certaines distributions disjointes dans l’Holarctique et les nombreuses espèces réparties dans les déserts d’Asie et d’Afrique. Il est donc intéressant de comprendre comment ces patrons de distribution disjoints sur l’Holarctique (e.g. Afrique du Nord, Amérique du Nord) ont été mis en place et ‘quand et où’ ces différents groupes sont apparus. Lors de cette thèse, pour la première fois, une phylogénie moléculaire comprenant 20 des 51 espèces de Dipodoidea a été reconstruite à partir de quatre gènes nucléaires (BRCA1, GHR, IRBP, RAG1). Cette phylogénie moléculaire a ensuite été comparée à une phylogénie morphologique reconstruite sur base des caractères de la dentition, de la bulle auditive, du gland du pénis et des glandes reproductives accessoires. Cela a permis de comprendre que les nombreuses controverses autour de la taxonomie et de la systématique des Dipodoidea étaient dues à des homologies qui brouillaient le signal phylogénétique. Ainsi, une nouvelle taxonomie des Dipodoidea a pu être proposée. La superfamille des Dipodoidea est dorénavant constituée de 3 familles (Sminthidae, Zapodidae, Dipodidae) et de 19 genres. Ensuite, pour étudier l’histoire évolutive biogéographique de la superfamille des Dipodoidea, l’échantillonnage taxonomique a été augmenté. La phylogénie moléculaire la plus complète à ce jour incluant 34 espèces de Dipodoidea a pu ainsi être reconstruite sur base du gène mitochondrial du cytochrome b et des mêmes gènes nucléaires utilisés précédemment. Lors de cette seconde étude, nous avons pu montrer que la radiation des Dipodoidea modernes a L eu lieu au Paléocène supérieur dans la région d’Asie Centrale et de l’Himalaya-Plateau Tibétain et que, de façon générale, leur histoire évolutive a été rythmée par les grands bouleversements climatiques et environnementaux engendrés par la surrection de l’Himalaya et du Plateau Tibétain. Pour étudier l’évolution de la biodiversité à l’échelle microévolutive, nous avons pris comme modèle biologique le campagnol roussâtre (Myodes glareolus). Les populations de campagnol roussâtre sont réparties en plusieurs lignées mitochondriales distribuées sur une large zone de la région Paléarctique. L’une d’elles, caractérisée par le génome mitochondrial du campagnol de la Taïga (Myodes rutilus), se distribue de la moitié supérieure de la Suède à travers la Finlande jusqu’au centre de la Russie. En Finlande, cette lignée introgressée (mitotype RUT) vient au contact d’une autre lignée du campagnol roussâtre (mitotype GLA). Il a été proposé que cette zone de contact en Finlande soit le résultat d’un contact secondaire. Cependant, étant donné qu’aucune différenciation nucléaire n’a été observée entre les mitotypes GLA et RUT, il n’est pas clair si cette zone de contact résulte bien d’un contact secondaire (deux évènements de recolonisation de la Finlande). Une autre hypothèse suggérant un seul événement de recolonisation de la Finlande pourrait également expliquer ce patron de discordance mito-nucléaire. Lors de cette thèse, nous avons étudié la zone de contact entre les mitotypes GLA et RUT située au centre de Finlande sur base de 17 marqueurs microsatellites et du cytochrome b. Notre but était d’estimer si la Finlande a connu un ou deux évènements de recolonisation postglaciaire et donc, de mieux comprendre si la zone de contact résulte ou non d’un contact secondaire entre les deux mitotypes. Les approches classiques de génétique des populations et de « clustering » ne nous ont pas permis de valider l’une ou l’autre des hypothèses du fait que la dispersion était limitée dans l’espace et que la différenciation génétique nucléaire entre les campagnols de Finlande était faible. Par conséquent, pour valider définitivement une des deux hypothèses, nous avons dû utiliser des analyses de clines de fréquences alléliques de marqueurs neutres. Celle-ci a montré que le cytb et 16 des 17 microsatellites présentaient des changements de fréquences alléliques entre les mitotypes GLA et RUT et que, par conséquent, la zone de contact entre les mitotypes GLA et RUT correspondait bien à une zone de contact secondaire résultant de deux évènements de recolonisation indépendants. En conclusion, cette thèse m’a permis de mieux comprendre comment la biodiversité évolue en réponse à différents facteurs. Etudier la biodiversité en utilisant des approches macroévolutives et microévolutives est très intéressant car cela permet d’avoir un regard large sur la manière avec laquelle les espèces, les populations et leurs génomes évoluent. [less ▲]

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

Doctoral thesis (2015)

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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See detailEtude de la mise en place du cytosquelette dans les cellules de l'organe de l'audition au cours du développement chez le rat
Johnen, Nicolas ULg

Doctoral thesis (2015)

An increasing number of people are affected by auditory deficiency. Several genes associated with deafness encode for cytoskeleton proteins that are expressed in cells of the inner ear. However, our ... [more ▼]

An increasing number of people are affected by auditory deficiency. Several genes associated with deafness encode for cytoskeleton proteins that are expressed in cells of the inner ear. However, our knowledge of cytoskeleton dynamics inside the inner ear is still incomplete. Up to now, most studies have principally focused on cytoskeleton organization at adult stages and not on its arrangement during development. In this work, we studied the development of the dynamic cytoskeleton structure in various cells of the rat organ of Corti, from its appearance at the 18th embryonic day (E18), to its functional state at the 25th post-natal day (P25). We used an indirect immunofluorescence method, which involves specific antibodies directed against different proteins from the three main types of cellular filaments: intermediate filaments (cytokeratines, vimentine), microtubules (βI–V-tubulin) and microfilaments (βcytoplasmic- and γcytoplasmic-actin). The labelling was performed on cryosections and then visualized through a laser scanning confocal microscope. A complementary ultrastructural analysis using transmission electronic microscopy was performed on select developmental timepoints. Our results clearly show that the cytoskeleton of the supporting cells plays a greater role in the development of the organ of Corti than that of the sensory hair cells. We observed an increase in the cytoskeletal organization of the supporting cells up to P6. We have shown that the cytoskeleton of supporting cells is highly developed during the deep disruptions of the auditory organ morphology appearing between P8 and P12. During this short period, we observed a partial epithelial-to-mesenchymal transition, which is marked by the temporary appearance of vimentine and a partial loss of cellular adhesion on the lateral face. At the same time, we also found a correlation between the onset of βV-tubulin expression and the formation of non-centrosomal microtubules arrays. Finally, the morphologically mature organ of Corti is characterized by a decrease of the cytoskeleton in some key regions of the cells. These observations underline the essential importance of the cytoskeleton in the maturation of the organ of Corti. [less ▲]

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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See detailRelative positioning with Galileo E5 AltBOC code measurements
Deprez, Cécile ULg

Master's dissertation (2015)

Depuis une dizaine d’années, l’Europe développe son propre système de positionnement par satellites (ou Global Navigation Satellites System (GNSS) en anglais), connu sous le nom de Galileo. À la pointe de ... [more ▼]

Depuis une dizaine d’années, l’Europe développe son propre système de positionnement par satellites (ou Global Navigation Satellites System (GNSS) en anglais), connu sous le nom de Galileo. À la pointe de la technologie, les horloges atomiques embarquées à bord de ses satellites ainsi que les signaux transmis par ces derniers sont extrêmement prometteurs dans beaucoup de domaines. Bien que toujours en phase de test à l’heure actuelle, ce système a déjà conduit à de premières mesures, notamment en matière de positionnement. Parmi ces nouvelles technologies, un signal en particulier semble très prometteur : Galileo E5, aussi appelé Galileo E5a+b ou encore Galileo E5 AltBOC. Ce signal permet d’effectuer des mesures de code et de phase plus précises. Il est également moins sensible au multi-trajet. Grâce à ses caractéristiques innovantes, Galileo E5 devrait permettre d’estimer des positions avec une précision supérieure à tous les autres signaux utilisés aujourd’hui. Une étude comparative des positions estimées avec les systèmes GPS (américain) et Galileo (européen) sur leurs différentes fréquences émises (GPS L1, GPS L2, GPS L5 pour GPS et Galileo E1, Galileo E5a, Galileo E5b et Galileo E5 AltBOC pour Galileo) a été menée dans ce mémoire. Pour ce faire, une combinaison d’observations appelée double différence (DD) est utilisée sous différentes configurations (ligne de base nulle (ZB), courte (SB) et moyenne (MB)) de récepteurs GNSS. Les récepteurs utilisés appartiennent à l’Université de Liège (2 récepteurs Trimble NetR9, 1 récepteur Septentrio XS et un récepteur Septentrio X4). Il ressort de cette étude que Galileo E5 AltBOC présente les observations les plus précises (en ZB, toutes sources d’erreurs éliminées). L’analyse démontre également qu’une précision de l’ordre de quelques décimètres sur la position à déterminer peut être atteinte avec les codes transmis par le signal Galileo E5, et ce jusqu’à 25 kilomètres de distance. [less ▲]

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See detailLe Circuit de l'ipséité sartrien. Conception, histoire, enjeux
Recchia, Fabio ULg

Master's dissertation (2015)

Ce mémoire interroge la thématique de la personnalisation chez Sartre. L'objectif est d'y faire le point sur un angle mort des études sartriennes : le concept de circuit de l’ipséité mis au point par ... [more ▼]

Ce mémoire interroge la thématique de la personnalisation chez Sartre. L'objectif est d'y faire le point sur un angle mort des études sartriennes : le concept de circuit de l’ipséité mis au point par Sartre dans L’être et le néant. Cette recherche est construite en trois parties. La première partie vise à inscrire le circuit de l’ipséité dans la théorie de l’intentionnalité du premier Sartre. L'on montre ainsi la manière dont L’être et le néant approfondit l’impersonnalité de la conscience de La Transcendance de l’Ego dans la direction d’une théorie de la personnalisation du pour-soi, indexée à la méthode de psychanalyse existentielle. La deuxième partie consiste à retracer la généalogie du concept de circuit de l’ipséité. Par un travail d’histoire de la philosophie, on reconstruit l’anthropologie sartrienne, qui s’articule aux concepts de personnalité et de socialité, au croisement de Heidegger, Bergson et Mauss. Cette reprise débouche sur un enjeu majeur : la nécessité d’élargir l’horizon ouvert par la compréhension phénoménologique de l’ipséité par une exploration méthodique des sciences humaines. S’inscrivant dans cette thématique de recherches, la troisième partie de ce mémoire consiste à souligner la persistance du thème de la personnalisation dans la philosophie du second Sartre. Partant, l'on interroge le rapport que celle-ci entretient avec les sciences humaines. [less ▲]

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See detailUnité de recherche universitaire CHU-ULg : Pour une expertise des implants dentaires et des biomatériaux de régénération tissulaire. Une étude de marché et un positionnement de produit
ROBERT, Marine ULg

Master's dissertation (2015)

« Science to make you smile »: this very catchy slogan best describes the corporate strategy of the Dental Biomaterials Research Unit (d-BRU) of the University of Liège that focus on industrial company ... [more ▼]

« Science to make you smile »: this very catchy slogan best describes the corporate strategy of the Dental Biomaterials Research Unit (d-BRU) of the University of Liège that focus on industrial company satisfaction by offering a wide range of expertise in dental biomaterials from the bench to the clinic. The current business plan thesis about the research unit’s strategy and its strategy for industry-cooperation development aims to identify the opportunities and threats in the biomaterial market for regenerative and implantable devices. The growing perspectives for implantable device companies are due to the fast-growing old age population and the evolution of technologies. Consequently, the industry demand for characterization, development and improvement of dental biomaterials is high and provides opportunities for company-university collaborative research project through clinical trials project initiation. We conducted a market demand analysis to measure the attractiveness and the dynamics of the dental biomaterials industry market. Among the 15 interviews with representatives of the dental industry, more than a half companies showed a positive reaction to our expertise presentation, which confirmed the demand trends. Few european acadmic centers behave like US universities in terms of industry-oriented marketing ; although the dental industry experienced favourable supply conditions for leading European clinical trials, d-BRU seized the opportunity to positioning as a modern research unit and taking advantage of a competitive edge. The market we aim is divided into 3 distinctive segment. We defined and implemented a distinctive strategic and marketing direction to reach the target market. The d-BRU differenciates itself by providing a Premium all-in-one service from in vitro/in silico tests to clinical performance for the dental industry in the field of biomaterials and implants. Articles published in top-tier scientific journals reflect the well-established scientific expertise of the d-BRU. The research team fulfils its academic goals with strength, conviction and dynamism and devotes the necessary technological and human resources to create the optimum conditions for collaborative research. The financial sustainability of d-BRU is guaranteed by recent existing agreement which assure regular revenue for the next 3 years. Moreover, our revenue forecast show a positive increase from 2016 to 2020. The high-added value of this project stems from a differentiated market positioning and innovative customized service process supported by skilled and highly motivated team of searchers. [less ▲]

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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See detailLes carrières en fin d'activités: un potentiel paysager?
Joris, Alicia ULg

Master's dissertation (2015)

The present study focuses on the landscape concept and evaluations and is based on some issues related to the impact, restoration and ecological potential of the abandoned quarries. It proposes a ... [more ▼]

The present study focuses on the landscape concept and evaluations and is based on some issues related to the impact, restoration and ecological potential of the abandoned quarries. It proposes a landscape character assessment for non active limestone quarries resulting from the spontaneous succession. Taking into account the guidelines of the European Landscape Convention (Conseil de l'Europe, 2000) , this work has for objectives (1) to describe these landscape areas and (2) to assess the landscape aesthetic quality. To achieve these goals, two methods inspired by the Landscape Character Assessment (LCA) were tested. The first one is a field sheet and the second one a landscape perception survey with stakeholders. The results have emphasized the natural, harmonious and unique character of these landscapes. The key characteristics are the visual importance of cliffs, water bodies, vegetation forms and the landform in bleachers. Furthermore, color contrast and textures from vegetation, rock and water were also relevant. An apparent aesthetic landscape quality was perceived and the study showed that respondents are feeling good in the site surveyed. The quarryscape can be characterized of challenging, attractive, wild with an important degree of naturality but not really safe. Cultural, historic, symbolic and ecological values were also highlighted as a potential. These later observations take part in a landscape dynamic and allow to open the debate concerning the need for landscape interventions within these sites and the profit we could benefit from if security issues were well-managed. [less ▲]

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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See detailModeling of aerodynamic forces in flapping flight with the Unsteady Vortex Lattice Method
Lambert, Thomas ULg

Master's dissertation (2015)

This thesis concerns the extensive study and comparison of two approaches commonly used to compute the aerodynamic forces with the unsteady vortex lattice method. The first approach was introduced by Katz ... [more ▼]

This thesis concerns the extensive study and comparison of two approaches commonly used to compute the aerodynamic forces with the unsteady vortex lattice method. The first approach was introduced by Katz and Plotkin and is based on Bernoulli's equations, the second approach was based Joukowski's equations for the computation of forces. This report is divided in two main sections: the study of one wing undergoing simple movements (steady, pure harmonic pitching and pure harmonic plunging) and the study of two separate wings undergoing a combination of flapping and pitching such as seen in avian flight. For the simple test cases, the results obtained with both methods of computation were first compared to an analytical solution for a (quasi) 2D case. Then the comparison of both methods was made for finite wings. For the 3D problem a convergence study was done with respect to the chordwise discretisation of the airfoils. This section showed that for all the cases, the two methods give almost the same answer and therefore they could be considered as equivalent. The convergence study realised for finite wings showed however that Joukowski's method converges quicker than Katz's for symmetric airfoils, but it is the other way around when it comes to cambered airfoils. The study of the flapping and pitching motion is based on the work of N. Abdul Razak. The influence of pitch leading was extensively studied as this phenomenon presents a flow attached at all time, so these kinematics are well suited for the vortex lattice method. Both pure flapping and pitch lagging were also discussed but more briefly. For pitch leading, the study showed that in general both methods give the same results for the drag and the lift. Moreover, the UVLM solutions were very close to the experimental ones, especially for the drag. The convergence showed a small advantage for the Katz method for the coarser meshes, but in the end both methods appear to reach convergence for the same discretisation. [less ▲]

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See detailStudy of the recent disappearance of a tropical glacier in the Bolivian Andes with the help of the high resolution regional climate model MAR
Scholzen, Chloé ULg

Master's dissertation (2015)

This study provides a first evaluation of the MAR (Modèle Atmosphérique Régional) model over the Bolivian tropical Andes. MAR is currently developed at the ULg and allows dynamical downscaling up to 5 km ... [more ▼]

This study provides a first evaluation of the MAR (Modèle Atmosphérique Régional) model over the Bolivian tropical Andes. MAR is currently developed at the ULg and allows dynamical downscaling up to 5 km of horizontal resolution. The purpose of this work is to model the recent changes in the climatic parameters which are thought to control the mass and energy balance of mountain glaciers in the outer tropics. We focus on the recently vanished Chacaltaya Glacier (16°S), which by virtue of its location and its environmental context is representative of many small-sized glaciers of the Bolivian Andes. To evaluate our model, we first examine simulated precipitation and near-surface temperature against in situ observations from ground weather stations. Since observational data is very scarce in this part of the world, we also refer to qualitative information provided by the scientific literature. We compare the performance of the model forced with two different reanalyses, and with several corrections applied to the lateral boundary conditions (LBCs) impacting on temperature and humidity. MAR forced with the ERA-Interim reanalysis yields better results than with the NCEP/NCAR-v2 reanalysis. We then use the best ERA-driven simulation to assess the long-term climate change over 1960-2014 in the region of the Chacaltaya Mountain. The regional atmospheric circulation is adequately simulated by MAR, which reproduces the prevailing seasonal features of the lower, middle and upper troposphere. The climatic anomalies associated to the El Niño Southern Oscillation (ENSO) events are also properly recreated. Remaining model biases include an overall year-round dry bias over the Altiplano region, due to the strong corrections applied to the LBCs (-15% for humidity). Over the highest elevations of the Andes, both precipitation and cloud cover are probably overestimated by MAR. The sporadic spatial distribution of convective rainfall also suggests numerical instability in the convective parameterization scheme. Modeled temperatures match very well the observations, but the reliability of the observed time series is highly questionable. Between 1960 and 2014, the most significant trends concern precipitation and cloud cover which both decreased of about 35%. The surface radiation budget also changed as a result of the reduced cloudiness. Near-surface temperature increased by about 1.5°C. Those trends are believed to have been enhanced by the more frequent and more intense El Niño events during the warm Pacific Decadal Oscillation (PDO) phase between 1977 and 1999. The combination of the repeated droughts and the enhanced incoming short-wave radiation due to reduced low-level cloudiness are probably the main factors responsible for the acceleration of the Chacaltaya Glacier recession. Nevertheless, the ENSO signal is not always clear in the Bolivian Andes, because of the interference with strong local climatic processes. Moreover, additional forcings of non climatic nature may also be responsible for the rapid demise of the Chacaltaya Glacier. [less ▲]

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

Doctoral thesis (2015)

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

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

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See detailMiliter pour et sur Internet. L'adhésion au Parti Pirate belge
Macq, Hadrien ULg

Master's dissertation (2015)

Suède, le 7 juin 2009. Aux élections européennes, un parti politique vient de créer la surprise. Il s’agit du Piratpartiet, fondé à peine trois ans plus tôt et qui vient de récolter sept pourcents des ... [more ▼]

Suède, le 7 juin 2009. Aux élections européennes, un parti politique vient de créer la surprise. Il s’agit du Piratpartiet, fondé à peine trois ans plus tôt et qui vient de récolter sept pourcents des suffrages, obtenant de la sorte un élu au Parlement. Ce parti, créé avant tout pour défendre une autre idée de la propriété intellectuelle, fait rapidement plusieurs dizaines d’émules à travers le monde, y compris en Belgique. La base de leurs revendications est invariable : réforme du droit d’auteur, abolition du brevet sur le vivant et le logiciel, meilleure défense des données privées. Les partis pirates se distinguent également par une utilisation intensive des nouvelles technologies de l’information et de la communication, tant dans leur communication vers l’extérieur que dans leur gestion interne. L’apparition de tels partis sur la scène politique peut être mise en perspective avec deux tendances plus larges au sein des sociétés occidentales. D’une part, Internet s’est petit à petit constitué en tant qu’enjeu politique à part entière, questionnant le système politique sur son mode de gouvernance et son degré de régulation. D’autre part, les pratiques d’engagement se sont progressivement transformées jusqu’à inciter les organisations politiques traditionnelles à s’adapter aux volontés des supposés néo-militants. Dans ce cadre, les partis politiques ont notamment pu s’appuyer sur Internet pour offrir un mode de participation plus souple et plus à même d’attirer de nouveaux adhérents. Cette tendance serait d’ailleurs arrivée à son zénith avec l’émergence de « cyber-partis », basant une grande partie de leur structure sur l’usage des réseaux télématiques. C’est dans cette optique que s’inscrit cette étude, avec pour objectif plus particulier d’interroger les impacts d’Internet sur la dynamique d’adhésion partisane. La question posée est la suivante : quel rôle Internet joue-t-il dans l’adhésion au Parti Pirate belge ? A partir de ce cas, ce sont les perspectives plus larges de l’adhésion aux cyber-partis et des pratiques contemporaines d’engagement qui peuvent être envisagées. De cette manière, il est possible d’apporter certaines réponses au renouvellement des questionnements en science politique engendré par le Web, concernant notamment la participation politique et l’organisation des partis. [less ▲]

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See detailL'estétrol et le développement tumoral
Gallez, Anne ULg

Master's dissertation (2015)

A l’heure actuelle, le risque augmenté de troubles thromboemboliques et de cancer du sein chez les femmes sous hormonothérapie est un problème majeur de santé publique. La découverte de nouvelles ... [more ▼]

A l’heure actuelle, le risque augmenté de troubles thromboemboliques et de cancer du sein chez les femmes sous hormonothérapie est un problème majeur de santé publique. La découverte de nouvelles molécules procurant une sécurité sanitaire accrue aux utilisatrices est donc nécessaire. L’estétrol (E4) est proposé comme candidat potentiel. L’E4 est une hormone stéroïdienne, de type « œstrogène », retrouvée naturellement chez l’humain et synthétisée uniquement par le foie fœtal durant la grossesse. Sa grande biodisponibilité orale et son temps de demi-vie de 28 heures chez l’humain le rendent intéressant en tant qu’hormonothérapie de substitution (ERT/HRT). L’E4 est capable de traiter efficacement les symptômes principaux de la ménopause (les bouffées de chaleur, l’atrophie vaginale et l’ostéoporose) et ce, dès une concentration de 0,3 mg/kg/jour. L’étude de son impact sur le cancer du sein est au centre de ce mémoire, puisque c’est l’une des conséquences majeures de l’utilisation prolongée d’œstrogènes et que les données de la littérature restent controversées Des résultats préliminaires obtenus au laboratoire ont montré que l’E4 (3 mg/kg/jour) augmentait le poids des tumeurs dans le modèle murin de carcinogenèse mammaire MMTV-PyMT, contrairement à l’ovariectomie et au traitement au Tamoxifène. Au terme de ce mémoire, nos recherches démontrent que l’E4 utilisé aux doses 0,3 et 7 mg/kg/jour n’influence pas significativement la croissance tumorale. Par contre, l’E4 à 3 mg/kg/jour majore le poids tumoral et la dissémination métastatique chez des animaux ovariectomisés et intacts. De plus, l’E4 délivré à 3 mg/kg/jour est capable d’augmenter l’angiogenèse et de diminuer la nécrose et l’hypoxie intra-tumorale, de manière similaire à l’oestradiol (E2) alors que la dose de 0,3mg/kg/jour n’est pas suffisante pour observer cet effet. En conclusion, les travaux menés pendant mon mémoire de Master ont permis de caractériser les effets de l’E4 sur la carcinogenèse mammaire hormonodépendante, la dissémination métastatique et l'angiogenèse tumorale. Au vu de nos résultats, nous ne pensons pas qu'il soit judicieux d'utiliser l'E4 comme traitement anti-tumoral, comme cela a été suggéré par certains auteurs. Au contraire, nos données suggèrent que pour éviter un effet de l’E4 sur la croissance tumorale et l’angiogenèse, il est nécessaire de privilégier le développement d’un traitement clinique de la ménopause avec de faibles concentrations d’E4. [less ▲]

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See detailEtude de l'évolution des conditions climatiques dans la région du Kilimandjaro, à l'aide du modèle MAR, sur la période 1951-2014
Flachat, Alexia ULg

Master's dissertation (2015)

Kilimanjaro glaciers appear among the most famous tropical glaciers. Even if they represent only 5% of the moutain glaciers, tropical glaciers are very interesting witnesses of the global warming. Indeed ... [more ▼]

Kilimanjaro glaciers appear among the most famous tropical glaciers. Even if they represent only 5% of the moutain glaciers, tropical glaciers are very interesting witnesses of the global warming. Indeed, their time of answer and their sensibility to climatic variations are more important than those of higher latitudes glaciers. Moreover, tropical climate is a very stable climate, which doesn’t present strong annual amplitudes of temperature. Thereby, the temperature is constantly negative at the top of the Kilimanjaro, what induces that the melting is essentially made by sublimation : ice passes from the solid state to the gaseous one, without passing by the liquid state. If we refer to the studies led since the half of the 19th, the climate change had for consequences to intensify the melting of Kibo ice cap, making spend its surface from 12,06 km² in 1912, to 2,36 km² in 2011. Hence, we decided to study by using the Regional Atmospheric Model (MAR), the evolution of climatic conditions in the region of the Kilimanjaro, over the period 1951-2014. We were thus able to put forward, firstly, that the decrease in cloudiness and precipitation, as well as the increased solar radiation, have played an important role in the melting of these glaciers. On the other hand, we also demonstrated that the NCEP and ERA-Interim reanalyses on Africa are not reliable, and consequently, the model presents difficulties to represent in a correct way the climate in our zone. To finish, we analyzed if we found the El Niño and La Niña events, of which the impact on the East African climate has been shown, in the model outputs. [less ▲]

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See detailEcologie de reproduction du doussié, Afzelia bipindensis Harms, en forêt dense humide tropicale gabonaise.
Evrard, Quentin ULg

Master's dissertation (2015)

The species Afzelia bipindensis is a precious woody tree known for its wood quality and considered vulnerable by the IUCN. In order to improve the current knowledge gaps about its reproductive ecology ... [more ▼]

The species Afzelia bipindensis is a precious woody tree known for its wood quality and considered vulnerable by the IUCN. In order to improve the current knowledge gaps about its reproductive ecology, the goals of this study are: (1) identify animal dispersers/predators of the seeds with direct and indirect observation methods, (2) quantify the dispersion/predation, (3) test the germination dynamics of those seeds under some circumstances that are likely to influence it, (4) model the growth of juveniles depending upon the access to light. This study was carried out in the forest concession attributed to the Precious Woods society and situated in evergreen forests in East Gabon. After more than 100 hours of direct observation and 3.000 hours of image capture by camera-trap, only four species (Cricetomys emini, Epixerus wilsoni, Protoxerus stangeri and some undetermined Muridae) would be the main animal species to get interested to Afzelia seeds. Those would take more than 90 % of the seeds and would be essentially predators. The results of the germination test revealed a significant influence of the aril on the germination rate. The conservation time and the volume of the seed had also a significant influence over its fitness. Finally, the modeling of growth showed a very low average growth value over time compared to equivalent data collected in Cameroon and a very high mortality rate, probably due to a high predation rate by duikers. [less ▲]

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See detailContribution au monitoring de populations d'hippopotame commun (Hippopotamus amphibius L.) par l'utilisation de la technologie drone (Parc National de la Garamba, République Démocratique du Congo)
Lhoest, Simon ULg

Master's dissertation (2015)

In an era of indisputable decline in populations of large wildlife species, setting up regular and efficient monitoring methods is essential. Because of the difficulties associated with conventional ... [more ▼]

In an era of indisputable decline in populations of large wildlife species, setting up regular and efficient monitoring methods is essential. Because of the difficulties associated with conventional pedestrian and aerial survey procedures, the development of UAV technology turns out to be a potentially interesting alternative. This work focuses on monitoring common hippopotamus (Hippopotamus amphibius L.) with the use of this innovative tool. The search for flight parameters optimization to maximize detection and visibility of animals showed a very small decrease in detection rate and certainty of counts with an increasing flying height and a high variability linked to operators realizing observations. It is recommended to fly at a height of 140 meters above ground level, between 6:30 and 8:45 am at the end of the dry season, with cloud cover and wind as low as possible. Three counts correction methods are proposed to estimate the total population from the only emerged observed animals. The average overall correction factor is 1.252. An attempt to describe the demography of a group by individuals length measurements was also implemented. It allowed to obtain a mean distribution of hippos in three age classes, even if results are not extremely accurate. Finally, an algorithm for the semi-automatic count of hippos on thermal infrared imagery was developed, and brought to a mean error of +3.9%. Taking into account the recommendations proposed in this study for the development of inventories protocols would help dealing with the practical constraints of conventional monitoring methods. [less ▲]

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

Doctoral thesis (2015)

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

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

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

Doctoral thesis (2015)

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

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

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See detailMise en place d’un système de mesure par covariance de turbulence des flux de N2O sur une parcelle agricole
Lognoul, Margaux ULg

Master's dissertation (2015)

Nitrous oxide (N2O) is a greenhouse gas responsible for 8% of anthropogenic radiative forcing. It is also a major contributor to stratospheric ozone depletion. Agricultural soils represent its main source ... [more ▼]

Nitrous oxide (N2O) is a greenhouse gas responsible for 8% of anthropogenic radiative forcing. It is also a major contributor to stratospheric ozone depletion. Agricultural soils represent its main source. N2O is produced by microorganisms through nitrification and denitrification processes. Both depend on oxygenation conditions and nitrogen and labile carbon availability, which are driven by soil and climate conditions and by farming practices. Yet there remain science gaps concerning the understanding of emission mechanisms and dynamics. The eddy covariance technique allows studying a whole ecosystem with a half-hourly temporal resolution, opening up for long-term monitoring and precise greenhouse gas budget calculation. However, this technique requires a specific expertise. In order to install such a system to measure N2O exchanges by a production crop at the Terrestrial Observatory of Lonzée (Belgium), we set the following goals : (1) establishing the state of knowledge concerning N2O fluxes exchanged by crops and identifying gaps, (2) setting up a N2O analyzer at the experimental site and providing operating procedures, and (3) building and adjusting the first data processing and calculation procedures. As a result of this work, scientific gaps were identified and avenues for further research are suggested. Monitoring and data acquisition routines as well as first data processing procedures were implemented. Numerous questions still remain regarding the adaptation of classical methods (created to study CO2) to N2O, and they constitute the investigation prospects of this work. [less ▲]

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See detailEtude de la biodégradation anaérobie des feuilles de Mangifera indica (manguier) et de Manihot utilissima (manioc)
Mambanzulua Ngoma, Philippe ULg

Doctoral thesis (2015)

The population growth of these last two decades leaded to an increase of waste in the City Province of Kinshasa (VPK), capital of the Democratic Republic of Congo. Deprived by an effective management ... [more ▼]

The population growth of these last two decades leaded to an increase of waste in the City Province of Kinshasa (VPK), capital of the Democratic Republic of Congo. Deprived by an effective management system, the VPK produces essentially vegetal wastes that are constituted for the greater part of dead leaves. These wastes bother and pollute the environment. On another point of view, the Kinshasa households meet enormous difficulties for soil fertilization and to collect wood for energy. Its overexploitation of the wood entails the deterioration of the ecosystems and the public health. Therefore in order to contribute to the reduction of all these difficulties simultaneously, the aim of this thesis was to investigate the methanization of these wastes since this technique is relatively simple, fast and non expensive. So, the methanation was performed at 30°C on the leaves of Mangifera indica (MU, mango) and of Manihot utilissima (MI, cassava) that are the most accessible of the VPK. The biochemical methane potentials of the MU and MI leaves demonstrated that the MU leaves were favorable to the methanation due to their low content in bioactive substance (secondary metabolites) and their low C/N ratio. In addition, their digestates would be an effective fertilizing. By contrast, the MI leaves were unfavorable to the methanation since the methanogenesis was inhibited, probably because of their composition rich in carbon and secondary metabolites (lignine, polyphenols, saponines and anthraquinones). However, these metabolites would be beneficial for the methanation in lower contents than 0.3 g/l in the culture medium. The anaerobic co-digestion improved the daily methane yields of these two leaves. The biogas produced with this process would represent about 28 % of the wooden annual domestic consumption and its digestate would cover annually the all agricultural and forest degraded areas. So, the domestic methanation or on site or near the site of waste generation would be favored to avoid the cost of their transport and their industrial treatment. A promising pilot essay has been achieved. [less ▲]

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See detailA Feasibility Study of Direct Injection Spraying Technology for Small Scale Farms: Modeling and Design of A Process Control System
El Aissaoui, Abdellah ULg

Doctoral thesis (2015)

El Aissaoui Abdellah (2015). A feasibility study of direct injection spraying technology for Small Scale Farming: Modeling and design of a process control system. University of Liege-Gembloux Agro-Bio ... [more ▼]

El Aissaoui Abdellah (2015). A feasibility study of direct injection spraying technology for Small Scale Farming: Modeling and design of a process control system. University of Liege-Gembloux Agro-Bio Tech. Belgium. 175p., 11 tabl., 75 fig. The study aims to develop a process controller of direct injection spraying system (DIS) that can fit to carry out precise chemical application using variable rate application based on speed sensing in the context of small scale farming. It has the specific objectives of studying the feasibility of DIS by optimizing the hydraulic system and the process control designs as the main requirements for the best system reactivity and performance. The final design of DIS assessed to implement hydraulic system (hardware) and process controller (software) of a sprayer framework mounted on a rolling chariot propelled by walker operator. A logical approach is used of reviewing the state of art and formulating a specification book to develop a cost effective prototype to eventually adapt DIS expertise to the context of small scale farming. The demarche consists on giving low cost solution of variable rate technology to solve the technical problems related to usage and inefficiency of pesticide application mainly done by portable sprayers. The state of art gives a light on the development process of direct injection spraying technology (DIS) within the scope of precision agriculture progress. It also deals with technical options, advantages and problems related to DIS and control engineering solutions developed for improving spraying application efficiency and safety measures for human and environment. After that we have specified requirements of the researched DIS prototype by referring to existing art of DIS technologies and by diagnosing problems of chemical application in the context of small scale farming. It concerns specifically the technical requirements, setting values and performance of DIS process controller according to the working conditions of intensive cropping in small farming. The materials and methods consist on presenting the approach used for modeling the DIS prototype (splitting the problematic to the two main design aspects of hydraulic system and process control system) and evaluating it in laboratory conditions using simulated velocity data input. The data acquisition system is implemented for assessing the performance of DIS hydraulic and process controller performances. After that, the process controller is implemented in a cost effective electronic kit (box) to be mounted on a small sprayer framework propelled by worker. The hydraulic modeling of DIS served for optimizing the lag transport task as main problem of system reactivity performance and concentration process change. An algorithm is implemented in VB program to assess effect of hydraulic serial boom design (diameter and number of mounted nozzles in serial scheme) on flow dynamic to find compromise between lag transport, mixing ability (turbulence) and friction loss tasks that yield lateral and longitudinal uniformities application of standard boom layout. The modeling results showed lag transport and uniformity of respectively 2 s and 96 % for optimal conventional boom of 6 mm inner diameter having ten tip nozzles (ISO11003, 1.2 L/min~3bars). To solve systematic problem of lateral miss uniformity of serial boom layout (standard scheme), improved parallel boom layout (equidistant tubing lines of 4 mm diameter) is adopted for obtaining an even lag transport between nozzles. The test of parallel boom layout showed even lag transport approximating 1.5 s for ten mounted nozzles. The total response time of DIS is optimally improved to be within 2.5 s by installing electrical pumps close to boom and injecting chemical in suction side to the carrier pump assumed to perform online mixing without use of static mixer. The PID feedback controller is modeled in MATLABTM software. The process is considered as a first order process having a time constant of 0.2 s and a delay transport less than 2 s. Two control strategies of constant carrier flow control (CCFC) and total flow control (TFC) are modeled and implemented for test in laboratory conditions. Both strategies were tested and evaluated on the basis of different solicitations of variable speed input within the range of 0 - 2 m/s as a field working condition of walker operating a rolling sprayer chariot. Finally, on the basis of the results of modeling and experimental assessment, an affordable kit of PLC process controller and PWM modules for actuating carrier pump and metering pump is performed in compact electronic box for potential usage on small sprayer framework to be propelled by walker operator in agricultural field. The controller is based on a PLC microcontroller implemented for carrying out a constant carrier flow rate and a variable chemical injection rate proportionally to the operating speed. The prototype is tested for applying variable rate application using simulated step solicitations within the range of the operator working conditions of 0 - 2 m/s. The study showed the feasibility of implementing a cost effective process controller design for applying variable rate chemical in small farming context. The controller is adaptable for sprayer mounted on wheeled chariot to be propelled by worker assumed to walk at variable velocity. [less ▲]

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See detailDÉTECTION ET QUANTIFICATION DES RACINES ET DES RÉSIDUS DE CULTURE DE FROMENT D’HIVER (TRITICUM AESTIVUM L.) PAR IMAGERIE HYPERSPECTRALE PROCHE INFRAROUGE
Fraipont, Guillaume ULg

Master's dissertation (2015)

On the basis of 384 soil samples collected at 4 different dates during the 2011-2012 crop season in the 0-30 cm soil horizon, this master thesis allowed the study of crop residues evolution and the ... [more ▼]

On the basis of 384 soil samples collected at 4 different dates during the 2011-2012 crop season in the 0-30 cm soil horizon, this master thesis allowed the study of crop residues evolution and the development of winter wheat root system throughout the crop season by the means of NIR-HSI technology and chemometric tools. [less ▲]

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See detailCases remémorées, redessinées. Mémoire de la bande dessinée, détournement et traces graphiques dans 'Au travail' d'Olivier Josso Hamel
Crucifix, Benoît ULg

Master of advanced studies dissertation (2015)

In his autobiographical comic Au travail, published at L’Association in 2012, Olivier Josso Hamel remembers his childhood readings of classic Franco-Belgian bandes dessinées by redrawing panels and ... [more ▼]

In his autobiographical comic Au travail, published at L’Association in 2012, Olivier Josso Hamel remembers his childhood readings of classic Franco-Belgian bandes dessinées by redrawing panels and sequences from these comics into the texture of his own graphic novel. This citational practice works as a détournement of the original material based on the author’s memories of specific images. Embedded in an autobiographical perspective, this appropriative technique sustains a retrospective reflection on what it means to be marked by an image. In this sense, Au travail offers a compelling ground to rethink the “case mémorable” (or ‘remembered panel’) a concept put forward by Pierre Sterckx to refer to comics panels remembered from childhood because of their visual impact. Through an analysis of Josso Hamel’s graphic novel, this paper argues that the remembered panel is not stictly mental but implies an active remembrance linked to the desire to share those personal images. As such, it is an intimate act of canonization based on the collective sharing of a personal history of comics. Expanding on Sterckx’s concept, this paper further seeks to show how the détournement of Franco-Belgian comics – as well as other graphic materials – in Au travail compels the author to reconsider his approach to drawing, reinventing his own style through the ‘graphic traces’ of his childhood. In turn, this carries further weight on the concept of the remembered panel: Josso Hamel’s practice of citation foregrounds the fragmentation of the narrative into fetishized images that become rooted in a personal history. In this way, Au travail highlights how non-narrative reading practices can break up the narrative into fragments that are reorganized into new combinations: not only in the author’s memory, but also and foremost in an ever-changing collective memory of the past of comics. [less ▲]

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See detailStudies of nebulae ejected from massive stars based on observations with the Herschel space observatory
Vamvatira-Nakou, Chloi ULg

Doctoral thesis (2015)

This PhD thesis is devoted to the study of the nebulae ejected by the luminous blue variable (LBV) stars WRAY 15-751 and AG Car as well as by the Wolf-Rayet star WR 124. It is based on new infrared data ... [more ▼]

This PhD thesis is devoted to the study of the nebulae ejected by the luminous blue variable (LBV) stars WRAY 15-751 and AG Car as well as by the Wolf-Rayet star WR 124. It is based on new infrared data taken by the Herschel Space Observatory. These data were complemented by optical data as well as by archived infrared observations. In the first chapter, a general introduction to the subject is given along with a description of the methods used for the data analysis. The three following chapters contain the study of each one of the three nebulae separately. This led to the determination of the physical parameters of the dust and gas components, with the aim to shed a new light on the mass-loss history of the central stars. In particular, the new Herschel infrared images provide a detailed mapping of the nebular dust distribution and of the circumstellar environment at different scales, revealing multiple shells and cavities linked to previous mass-loss events. Moreover, the combination of Herschel photometric results along with archival data was used to model dust with the help of a two-dimensional publicly available radiative transfer code. This model provided us with the dust mass, temperature and composition. The Herschel infrared spectra of all nebulae revealed forbidden nebular emission lines coming not only from an ionized gas region but also from a region where the gas is neutral. Based on the emission line flux measurements, the gas mass and the abundance ratios were estimated. These results, combined with the theoretical models of stellar evolution, were then used to constrain the evolutionary stage of the star at which each nebula was ejected. This study underlines the importance of the Herschel infrared observations for these nebulae. Thanks to them, a better understanding of these objects has been achieved. In particular, a second bigger and fainter dust shell was discovered around WRAY 15-751. In addition, all nebulae were found lying in empty cavities, probably formed during a previous evolutionary phase of their central star. The dust models indicated the necessity to include large grains in all nebulae to reproduce the data. This study showed that for the LBV WRAY 15- 751, with an initial mass of 40 M sun, the nebular ejection took place during a red supergiant phase, while for the LBV AG Car, with an initial stellar mass of 55 M sun, the ejection happened during a cool LBV phase. For the nebula M1-67 around the star WR 124, with an initial mass of 60 M sun, the ejection also took place during a LBV phase. These results are in agreement with the current evolutionary models with little stellar rotation. [less ▲]

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See detailCHARACTERIZATION OF STONY SOILS’ HYDRAULIC PROPERTIES AND REPRESENTATIVE ELEMENTARY VOLUME USING FIELD, LABORATORY AND NUMERICAL EXPERIMENTS
Pichault, Mathieu ULg

Master's dissertation (2015)

Determining soil hydraulic properties is of major concern in various fields of study such as soil physics, hydrology, ecology and agronomy. Though stony soils are widespread across the globe, most studies ... [more ▼]

Determining soil hydraulic properties is of major concern in various fields of study such as soil physics, hydrology, ecology and agronomy. Though stony soils are widespread across the globe, most studies deal with gravel-free soils so that the literature describing the impact of stones on a soil’s hydraulic characteristics is still rather scarce. The aim of this study is to assess, through a case study of a clayey soil in Thailand, the effect of rock fragments on the main hydraulic characteristics, i.e. hydraulic conductivity and retention curves, and on related physical properties of the soil. This was done by means of field, laboratory and numerical experiments involving different amounts and types of coarse fragments. Results were compared with those predicted by several models assuming that stones are non-porous and only reduce the cross-sectional area available for water flow. These models further consider that the shape parameters of the retention and hydraulic conductivity curves are not dependent on the stoniness. We tested the validity of such assumptions. We did not find evidence against the assumption stating that stones might be considered as non-porous. However, our results suggest that the shape parameters of the retention curve vary according to the stone content. Furthermore, considering that stones only reduce the cross-sectional area available for water flow might also be ill-founded. We pointed out several significant drivers of the saturated hydraulic conductivity which are not considered by these models. First of all, the effect due to the creation of voids at the fine earth-stone interface combined with an increased difficulty to repack the fine earth can counteract and even overcome the effect of a reduced cross-sectional area in some cases. Moreover, the shape and the size of inclusions may also affect substantially hydraulic conductivity. Finally, we developed a code destined to quantify the representative elementary volume of soils containing different amounts of stones of various diameters. [less ▲]

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See detailAdvanced numerical framework to simulate Incremental Forming Processes
Velosa De Sena, José ULg

Doctoral thesis (2015)

The framework of the present work supports the numerical analysis of the Single Point Incremental Forming (SPIF) process resorting to a numerical tool based on adaptive remeshing procedure based on the ... [more ▼]

The framework of the present work supports the numerical analysis of the Single Point Incremental Forming (SPIF) process resorting to a numerical tool based on adaptive remeshing procedure based on the FEM. Mainly, this analysis concerns the computation time reduction from the implicit scheme and the adaptation of a solid-shell finite element type chosen, in particular the Reduced Enhanced Solid Shell (RESS). The main focus of its choice was given to the element formulation due to its distinct feature based on arbitrary number of integration points through the thickness direction. As well as the use of only one Enhanced Assumed Strain (EAS) mode. Additionally, the advantages include the use of full constitutive laws and automatic consideration of double-sided contact, once it contains eighth physical nodes. Initially, a comprehensive literature review of the Incremental Sheet Forming (ISF) processes was performed. This review is focused on original contributions regarding recent developments, explanations for the increased formability and on the state of the art in finite elements simulations of SPIF. Following, a description of the numerical formulation behind the numerical tools used throughout this research is presented, summarizing non-linear mechanics topics related with finite element in-house code named LAGAMINE, the elements formulation and constitutive laws. The main purpose of the present work is given to the application of an adaptive remeshing method combined with a solid-shell finite element type in order to improve the computational efficiency using the implicit scheme. The adaptive remeshing strategy is based on the dynamic refinement of the mesh locally in the tool vicinity and following its motion. This request is needed due to the necessity of very refined meshes to simulate accurately the SPIF simulations. An initially mesh refinement solution requires huge computation time and coarse mesh leads to an inconsistent results due to contact issues. Doing so, the adaptive remeshing avoids the initially refinement and subsequently the CPU time can be reduced. The numerical tests carried out are based on benchmark proposals and experiments purposely performed in University of Aveiro, Department of Mechanical engineering, resorting to an innovative prototype SPIF machine. As well, all simulations performed were validated resorting to experimental measurements in order to assess the level of accuracy between the numerical prediction and the experimental measurements. In general, the accuracy and computational efficiency of the results are achieved. [less ▲]

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See detailMultiscale modelling of the hydromechanical behaviour of argillaceous rocks
van den Eijnden, Abraham Pieter ULg

Doctoral thesis (2015)

Feasibility studies for deep geological radioactive waste disposal facilities have led to an increased interest in the geomechanical modelling of its host rock. In France, a potential host rock is the ... [more ▼]

Feasibility studies for deep geological radioactive waste disposal facilities have led to an increased interest in the geomechanical modelling of its host rock. In France, a potential host rock is the Callovo-Oxfordian claystone. The low permeability of this material is of key importance, as the principle of deep geological disposal strongly relies on the sealing capacity of the host formation. The permeability being coupled to the mechanical material state, hydromechanical coupled behaviour of the claystone becomes important when mechanical alterations are induced by gallery excavation in the so-called excavation damaged zone (EDZ). In materials with microstructure such as the Callovo-Oxfordian claystone [Robinet et al., 2012], the macroscopic behaviour has its origin in the interaction of its micromechanical constituents. In addition to the coupling between hydraulic and mechanical behaviour, a coupling between the micro (material microstructure) and macro scale will be made. By means of the development of a framework of computational homogenization for hydromechanical coupling, a doublescale modelling approach is formulated, for which the macroscale constitutive relations are derived from the microscale by homogenization. An existing model for the modelling of hydromechanical coupling based on the distinct de nition of grains and intergranular pore space [Frey, 2010] is adopted and modi ed to enable the application of rst order computational homogenization for obtaining macroscale stress and uid transport responses. This model is used to constitute a periodic representative elementary volume (REV) that allows the representation of the local macroscopic behaviour of the claystone. As a response to deformation loading, the behaviour of the REV represents the numerical equivalent of a constitutive relation at the macroscale. For the required consistent tangent operators, the framework of computational homogenization by static condensation [Kouznetsova et al., 2001] is extended to hydromechanical coupling. The theoretical developments of this extension are implemented in the nite element code Lagamine (Li ege) as an independent constitutive relation. For the modelling of localization of deformation, which in classical FE methods su ers from the well-known mesh dependency, the doublescale approach of hydromechanical coupling is combined with a local second gradient model [Collin et al., 2006] to control the internal length scale of localized deformation. By accepting the periodic boundary conditions as a regularization of the microscale deformation, the use of the multiscale model in combination with the local second gradient model can be used for modelling localization phenomena in HM-coupled settings with material softening. The modelling capacities of the approach are demonstrated by means of simulations of oedometer tests and biaxial compression tests. The approach is demonstrated to be a powerful way to model anisotropy in the mechanical as well as the hydraulic behaviour of the material both in the initial material state and as an e ect of hydromechanical alterations. For the application to the modelling of Callovo-Oxfordian claystone, microstructural REVs are calibrated to geometrical characteristics of the inclusion that form the microstructure under consideration and to macroscale experimental results of the mechanical behaviour. The calibrated constitutive relation is used in the simulation of gallery excavation processes. These computations give a proof of concept of the doublescale assessment of the hydromechanical behaviour of the excavation damaged zones around galleries in the context of nuclear waste disposal. [less ▲]

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See detailGénétique et biologie de la conservation du desman des Pyrénées (Galemys pyrenaicus) en France
Gillet, François ULg

Doctoral thesis (2015)

The Pyrenean desman (Galemys pyrenaicus) is a semi-aquatic mammal endemic to the Iberian Peninsula and the Pyrenees and classified as “vulnerable” by the IUCN. The aims of this PhD thesis, part of a ... [more ▼]

The Pyrenean desman (Galemys pyrenaicus) is a semi-aquatic mammal endemic to the Iberian Peninsula and the Pyrenees and classified as “vulnerable” by the IUCN. The aims of this PhD thesis, part of a National Action Plan, were to improve the knowledge on this species by the development of molecular tools (species identification by sequencing of a fragment of the cytochrome b gene and by RFLP, creation and amplification of polymorphic microsatellites). A genetic structure of three populations associated with low levels of genetic diversity has been evidenced in the French Pyrenees. In addition, the molecular analysis of its diet (COI gene) has allowed to identify its foraging areas and an individual survey on a stretch of river has revealed long distance movements unsuspected before. These results may direct conservation measures for this species. [less ▲]

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See detailEvaluation of the promethazine and acepromazine sedative and hemodynamic effects and norepinephrine reversal of acepromazine induced hemodynamic alterations in the standing horse
De Araujo Pequito, Manuel ULg

Doctoral thesis (2015)

Some phenothiazine derivates, such as acepromazine (ACP), have beneficial properties that could be interesting in equine patients with systemic inflammatory diseases where neutrophil activation and ROS ... [more ▼]

Some phenothiazine derivates, such as acepromazine (ACP), have beneficial properties that could be interesting in equine patients with systemic inflammatory diseases where neutrophil activation and ROS production are implicated. Besides, ACP’s vasodilatatory properties can also be of clinical importance in conditions such as acute laminitis or in anaesthetic protocols. However, the vasodilation induced by ACP is contraindicated in horses suffering from hypotension, a typical complication of systemic inflammatory diseases in horses. The sedative effect of ACP can also have an impact on the correct evaluation of the mental state of a horse in intensive care. Hence, it could be important either to select another phenothiazine derivate with the same beneficial effects as ACP, but with fewer undesirable effects, or to create a medication protocol, in which ACP is associated to another molecule, with the purpose of diminishing its undesired effects. Therefore, this work focused on the comparison of the sedative and peripheral hemodynamic effects of ACP and promethazine (PTZ) as well as on the evaluation of the hemodynamic effects of the administration of ACP followed by a norepinephrine (NOR) infusion in the standing healthy horse. To achieve this objective, 3 different studies were designed. The first one focused on the comparison between ACP and PTZ and the two other ones focused on the study of the association between ACP and NOR. In the first experimental protocol, 9 healthy Warmblood horses randomly received either intravenous ACP at 0.1 mg/kg or PTZ at 0.1, 0.2 or 0.3 mg/kg. A sedation score based on clinical examination was recorded, and systolic arterial blood pressure (SAP) was noninvasively evaluated using a Doppler flow detector at the tail, just before and every 15 minutes until 60 minutes after drug injection. Hemodynamics of the median artery of the left forelimb was studied using Doppler ultrasonography just before and 45 minutes after injection of the drug, which allowed calculation of surface (SURF), diameter (DIAM), and circumference (CIRC) of the vessel, as well as peak systolic velocity (PSV), end diastolic velocity (EDV), mean velocity (MV), volumetric flow (VF), and resistivity index (RI) of the blood flow. In the second experimental protocol, an infusion of NOR at a constant rate of 1 μg/kg/minute for 15 minutes was administered to 5 standing healthy horses 45 minutes (TACP+45) after intravenous injection of ACP at 0.1 mg/kg. Non-invasive SAP and the same hemodynamic parameters than in study 1 were evaluated on the median artery. The SAP was evaluated before, 15, 30, 45 and every 5 minutes during the NOR infusion (TNORa, TNORb, TNORc) from TACP+45 to 60 minutes (TACP+60) after ACP administration and at 5 (TACP+65), 15 (TACP+75), 30 (TACP+90) and 45 (TACP+105) minutes after stopingt the NOR infusion. In the third experimental protocol, 45 minutes after ACP intravenous injection at 0.1 mg/kg, a continuous NOR infusion was performed during 10 minutes at 0.3 μg/kg/min, then 10 minutes at 0.5 μg/kg/min, and finally 10 minutes at 1 μg/kg/min in 5 standing healthy horses. Cardiac output (CO), stroke volume (SV) and systemic vascular resistance (SVR) were measured using lithium dilution (LiDCO). The mean (MAP), systolic and diastolic (DAP) systemic arterial pressures were measured invasively using an anesthesic monitoring system, that also automatically calculated the heart rate (HR). All parameters were measured immediately before ACP administration, 45 minutes after, at the end of each incremental 10 minutes NOR continuous infusion rate (TNOR0.3, TNOR0.5 and TNOR1) and ten minutes after terminating the NOR infusion. Regardless of the used dose, PTZ had lesser sedative and hypotensive effects than ACP at 0.1 mg/kg and did not induce significant variations in SURF, DIAM, CIRC, PSV, EDV, MV, VF, and RI of the studied standing horses. Conversely, the vasodilatory and hypotensive properties of ACP were illustrated by a significant increase in SURF, DIAM, CIRC, PSV, EDV, MV, and VF and a significant reduction of the RI and SAP. Unlike ACP, PTZ did not induce alterations on the morphology of the Doppler waveform. All the ACP-induced hemodynamic alterations, with the exception of PSV and MV were significantly counteracted by the NOR infusion at a constant 1 μg/kg/minute rate, from TNORa to TNORc for EDV, VF, MV and RI, and to TACP+65 for SAP, from TNORb to TACP+90 for CIRC and SURF and to TNORc for DIAM. Besides, although the ACP induced hypotension, no significant changes were observed in the CO, SV, SVR and HR. NOR infusion at incremental doses counteracted the decrease of SAP, from TNOR0.3 to TNOR1, of MAP at TNOR0.3 and TNOR1 and of DAP at TNOR1. After the ending of the infusion, the arterial pressure again dropped significantly, the CO and HR increased non significantly, and the SVR decreased non significantly. PTZ appears to have less sedative and peripheral vasodilator effects than ACP, thus it could be safer than ACP in patients suffering from hypotension. The results also demonstrate that a NOR infusion can reverse ACP’s vasodilatory effects, restoring hemodynamic parameters and blood pressure in horses. The studied NOR infusion proved hence to be useful in horses suffering from vasodilation and hypotension, as it reverted the hemodynamic alterations induced by ACP. [less ▲]

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See detailLa Musique silencieuse de José Muñoz et Carlos Sampayo : déconstruction des normes et lecture émotionnelle
Dejasse, Erwin ULg

Doctoral thesis (2015)

Cette thèse met en lumièredans l'oeuvre de José Muñoz et Carlos Sampayo les mécanismes de déconstruction des normes issues de la bande dessinée de genre fondée sur le principe de l’illusion référentielle ... [more ▼]

Cette thèse met en lumièredans l'oeuvre de José Muñoz et Carlos Sampayo les mécanismes de déconstruction des normes issues de la bande dessinée de genre fondée sur le principe de l’illusion référentielle. Cette entreprise de dislocation des standards graphiques et narratifs vise à substituer à la lecture traditionnelle fondée sur la consommation du récit, une lecture émotionnelle. [less ▲]

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See detailIntégration de la continuité spatiale dans la structure multidimensionnelle d’un entrepôt de données - SOLAP raster
Kasprzyk, Jean-Paul ULg

Doctoral thesis (2015)

Technological advances in recent decades have created a massive acquisition of digital data whose volume grows exponentially. To efficiently extract the information they contain, powerful tools have been ... [more ▼]

Technological advances in recent decades have created a massive acquisition of digital data whose volume grows exponentially. To efficiently extract the information they contain, powerful tools have been developed to collect, store and analyze these data. These tools are gathered in a discipline called “business intelligence”. Among them, data warehouses are responsible for archiving data by structuring them in a multidimensional way (time, space or others). They are called data hypercubes or data cubes when they are limited to three dimensions. Hypercubes can supply OLAP (On Line Analytical Processing) systems that aim at quickly synthesizing information in interactive tables and charts for decision-makers from various fields: marketing, environment, criminology, etc. Thus, users can navigate into hypercubes using OLAP operations such as slicing on dimension members (e.g. data aggregation for the month of January in the time dimension), or drilling into hierarchies (e.g. switching from the “year” level to the “month” level in the time dimension). When OLAP is coupled with spatial analysis techniques supplied by geographic information systems (GIS), a map interface then improves the exploration of data: OLAP operations can be applied to dimensions defined in the geographical space (spatial drilling or spatial slicing). This kind of tool is called SOLAP (Spatial OLAP). SOLAP tools currently available on the market all suffer from the same deficiency: they are unable to represent spatial dimensions (X, Y) in a continuous way. This representation is nevertheless essential for the management of spatially continuous phenomena (temperature, pollution, etc.) but also for visualizing spatially discrete events (product sales, crimes, etc.) while minimizing the Modifiable Areal Unit Problem (MAUP). This kind of visualization is used especially by the police to predict the location of future crimes through hotspot maps which are generated by the Kernel Density Estimation (KDE) method. In the field of GIS, raster data (as opposed to vector data) enable effective representation of spatial continuity through digital georeferenced grids. Whereas current SOLAP tools only consider vector data, our research uses the raster model to integrate spatial continuity into the multidimensional structure of a data warehouse feeding a SOLAP ("raster SOLAP"). Despite its underutilization in the SOLAP literature, the raster model has many similarities with a particular kind of data cube: the MOLAP cube (Multidimensional OLAP). Like a satellite image (raster) representing the two planimetric spatial dimensions and one "spectral band" dimension, a MOLAP cube is a three dimensional array whose cells’ coordinates (similar to raster pixels) enable an efficient indexation of dimensions’ members (describing the analyzed facts). In a first original model that we call "raster cube" we define the bases for a three-dimensional raster SOLAP, starting from the definition of a MOLAP cube. Unlike vector SOLAP - where spatiality is attached to a semantic dimension through pointers to geometries - our model directly integrates spatial dimensions (X, Y) in the multidimensional structure of the data warehouse. With this original feature, any geographical entity (country, building, road, etc.) can be imported on the fly as a member in the analysis of the user, which is hardly possible with conventional vector SOLAP tools. An extension of this SOLAP model, called "raster hypercube", is then developed by entrusting the management of extra non-spatial dimensions to a relational database management system (Relational OLAP or ROLAP). The raster hypercube is then populated by KDE raster fields representing crime densities, which are defined in a continuous space (raster dimensions) through time and crime types (ROLAP dimensions). Our model is able to combine the production of hotspot maps at different scales of analysis with SOLAP navigation operations: slicing on spatial or non-spatial members, and drilling into the hierarchy of spatial or non-spatial dimensions. Our raster hypercube model is validated by an operating prototype which is based on open source tools only. Several datasets are integrated through KDE fields, including crime data from London and Seattle. At the end of our work, the results of a comparative study between raster SOLAP and vector SOLAP demonstrate that hybrid vector/raster SOLAP architectures present the same interest for spatial data as hybrid ROLAP/MOLAP architectures do for purely semantic data (management of detailed hypercubes [less ▲]

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See detailExploiting Interspecific Genetic Variability for Improving Common bean for higher productivity on soils presenting biotic and abiotic stresses
Butare, Louis ULg

Doctoral thesis (2015)

Biotic and abiotic stresses often occur in the same field of rural poor farmer households in tropical countries resulting in heavy losses of common bean yields. To improve resistance of common beans ... [more ▼]

Biotic and abiotic stresses often occur in the same field of rural poor farmer households in tropical countries resulting in heavy losses of common bean yields. To improve resistance of common beans, sensitive Phaseolus vulgaris (SER16) was crossed to resistant P. coccineus (G35346-3Q) to create 94 F5:6 recombinant inbred lines (RILs) of the pedigree SER16♀ x (SER16♀ x G35346-3Q♂). The objectives of this study were to (i) identify potential parents for resistance to Al, drought and Fusarium root rot among 11 bean genotypes, (ii) to evaluate 94 F5:6 Recombinant Inbred Lines (RILs) of the cross SER 16♀ x (SER 16♀ x G35346-3Q♂) both for their resistance to Al and /or drought, (iii) to evaluate RILs for resistance to Fusarium root rot, and (iv) to identify QTL for resistance to these stresses. RILs were characterized in greenhouse for resistance to Al using a hydroponic screening employing a nutrient solution with or without 20 μM Al , to Al-toxic acid soil with high Al (HAl) and low Al (LAl) saturation, to terminal drought simulation with and without progressive soil drying, to combined stresses of Al and terminal drought in 80 cm long soil cylinder system, and to Fusarium root rot using inoculated perlite soil and sand (2:1). Two field studies were also carried on in Colombia under rainfed and irrigated conditions in Palmira, and high Al saturated acid soil in Santander of Quilichao. Our studies confirmed the superiority in Al response of Andean common beans in greenhouse trials compared to Middle American type for several root traits. Each screening method of our Al greenhouse experiments permitted an evaluation of different aspects of root traits. The two parents were virtually equal for tap root elongation rate at 24 h in the 20 μM Al treatment at about 1.4 mm h-1 while progenies ranged from less than 1-1.75 mm h-1. The correlation between leaf area and total root length was highly significant under high Al saturation (r = 0.70***) for HAl-acid soil. Two genotypes (ALB88 and ALB 91) emerged as strong multiple trait lines for the two abiotic stresses. Fusarium root rot induced root growth inhibition as high as 80.8% for the susceptible ALB 5, while resistant RILs (ALB45, ALB41, ALB126, ALB84, ALB49, ALB34, ALB88 and ALB85) didn`t show any inhibition . Seed yield under drought stress conditions was positively associated to 100-seed weight both under irrigated field (r = 0.28**) and rainfed field (r = 0.36***), and negatively associated to days to maturity (DTM) (r = - 0.36***) in field evaluation in Al-toxic acid soil in Quilichao (Colombia). QTLs for important traits including root characteristics under high Al , grain yield and yield components for drought and high Al saturation soil were identified. The use of both soil and hydroponic system, and field could contribute to evaluation of breeding materials to identify genotypes that combine Al resistance with acid soil tolerance, drought and root rot tolerance. [less ▲]

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See detailPerturbations de l'épissage des ARN pré-messagers par les agents chimiothérapeutiques: mécanismes d'action du cisplatine et impact sur la mortalité des cellules cancéreuses
Gabriel, Maude ULg

Doctoral thesis (2015)

L’épissage alternatif est un processus qui concerne plus de 90% des pré-ARN messagers et qui contribue largement à la diversité protéique. Il est régulé par une série de facteurs d’épissage qui se lient ... [more ▼]

L’épissage alternatif est un processus qui concerne plus de 90% des pré-ARN messagers et qui contribue largement à la diversité protéique. Il est régulé par une série de facteurs d’épissage qui se lient sur des séquences situées sur les transcrits primaires. L’activité de ces facteurs d’épissage est régulée, entre autres, par divers signaux externes et voies de signalisation.  Les agents chimiothérapeutiques peuvent altérer la régulation de l’épissage et, ainsi, modifier la séquence d’un grand nombre d’ARN messagers et, éventuellement, la fonction des protéines qui en résultent. Cependant, l’implication de ces mécanismes dans la thérapie anticancéreuse demeure mal connue en termes d’efficacité thérapeutique, de diagnostic, de pronostic, de développement de résistances aux traitements et d’induction d’effets secondaires. L’objectif principal de cette étude est d’évaluer si la régulation de l’épissage par le cisplatine est critique pour son activité anticancéreuse. L’analyse du transcriptome de cellules mammaires cancéreuses traitées avec du cisplatine a permis d’identifier de nombreuses altérations d’épissage induites par la chimiothérapie. Parmi les 700 évènements observés, un grand nombre touche des transcrits impliqués dans le cycle cellulaire et dans la régulation de l’épissage lui-même.   Bien que le cisplatine induise des dommages au niveau de l’ADN, nous avons exclu la participation des membres de la voie des dommages à l’ADN, tels que ATM, ATR, DNA-PK et p53, dans les altérations d’épissage induites par le cisplatine. Les PI3K de class I (p110) et la voie MEK/ERK sont , en revanche, requises.  L’utilisation d’une banque de plus de 50 siRNA ciblant des protéines se liant à l’ARN, en particulier des facteurs d’épissage, nous a permis d’évaluer l’implication de ces facteurs dans les modifications d’épissage observées après le traitement au cisplatine. Il est apparu que la réduction de l’expression de certains facteurs dont SF3A1, RBM39, U2AF1 et snRNP70 mime les effets du cisplatine. A l’inverse, l’inhibition de SRSF4 réprime ces effets.  Par co-immunoprécipitation, nous avons observé un lien physique entre le facteur de transcription c-Jun et les facteurs d’épissage SF3A1 et RBM39. Alors que cette liaison ne semble pas être affectée par le cisplatine, des modifications du statut de phosphorylation de c-Jun ont été observées après traitement au cisplatine. La déplétion de c-Jun et l’inhibition d’AP-1 corrigent en partie l’effet du cisplatine sur l’épissage, suggérant leur implication dans le processus.   Finalement, nous avons montré que la déplétion en SRSF4 réduit la mortalité cellulaire induite par le cisplatine, alors que la déplétion en SF3A1 et RBM39 l’augmente. Ces résultats montrent une corrélation entre épissage et mort cellulaire et suggèrent que la modulation de l’épissage pourrait être utilisée comme thérapie adjuvante afin d’augmenter l’efficacité de la chimiothérapie.   [less ▲]

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See detailBilan bactériologique des mammites dans les troupeaux Zébu Azawak à la station expérimentale sahélienne de Toukounous (Niger) et épidémiologie moléculaire des Staphylococcus aureus isolés entre 2009 et 2012
Issa Ibrahim, Abdoulkarim ULg

Doctoral thesis (2015)

L’élevage est la seconde activité principale après l’agriculture au Niger. Cependant, ce secteur est confronté à d’énormes problèmes, notamment la faible productivité des animaux, le faible investissement ... [more ▼]

L’élevage est la seconde activité principale après l’agriculture au Niger. Cependant, ce secteur est confronté à d’énormes problèmes, notamment la faible productivité des animaux, le faible investissement, des problèmes d’alimentation et d’accès aux points d’eau, et divers problèmes sanitaires récurrents. Depuis l’indépendance du pays en 1960, plusieurs politiques ont été mises en œuvre pour améliorer la productivité des espèces et races domestiques locales. C’est ainsi que, la station expérimentale sahélienne de Toukounous a vu le jour, avec comme objectifs la sélection et la diffusion de la race Zébu Azawak auprès des producteurs ruraux. Les efforts de sélection ont abouti à l’obtention d’un animal standard bien adapté au contexte sahélien avec un niveau de production en lait acceptable. Le bétail laitier à travers le monde souffre énormément des problèmes sanitaires liés aux infections de la glande mammaire. La situation est la même à Toukounous malgré la proximité de services vétérinaires et para-vétérinaires. Cependant, au Niger de manière générale, les données sur les mammites sont rares et très peu de publications scientifiques sont disponibles. Une des possibles explications est la prévalence élevée de mammites sub-cliniques, mais faible de mammites cliniques. La présente étude est dès lors centrée sur les problèmes de mammites au sein de la station sahélienne expérimentale de Toukounous afin d’identifier : (i) les vaches souffrant de mammites cliniques et/ou subcliniques ; (ii) les principales bactéries pathogènes responsables ; et (iii) les virulotypes et profils de résistance aux antibiotiques des souches de Staphylococcus (S.) aureus isolées ; et afin de démontrer l’impact positif de l’application de mesures simples d’hygiène lors de la traite manuelle sur la prévalence de vaches avec mammite. De 2009 à 2012, l’ensemble des vaches en lactation des trois troupeaux de la station, à savoir « élites », « non-élites » et « primipares » ont été testées avec le « California Mastitis Test » (CMT). Ensuite, le lait de tous les quartiers des vaches ayant réagi positivement au test CMT a été prélevé pour réaliser des analyses bactériologiques au Niger. Les espèces bactériennes pré-identifiées au Niger ont ensuite été importées en Belgique (ULg-FMV) afin de procéder à une identification complète par des galeries API®. Les souches confirmées de S. aureus ont par la suite été étudiées pour leurs virulotypes (i) phénotypiquement pour la production de biofilm par mesure de la densité optique après croissance en milieu liquide en plaque de microtitration et pour la synthèse d’une capsule par un test ELISA ; et (ii) génétiquement par PCR ciblant des gènes codant pour différentes propriétés de virulence (adhésines, leucotoxines, entérotoxines, biofilm, et capsule) ; ainsi que pour leurs profils de résistance aux antibiotiques par le test de diffusion en gélose, ou antibiogramme. Ces mêmes souches ont été comparées par leurs empreintes génétiques après « Pulsed Field Gel Electrophoresis » (PFGE), ou pulsotypes, pour en étudier la clonalité au cours des 4 années de l’enquête et dans les 3 troupeaux. Enfin, l’impact de mesures d’hygiène (lavage et désinfection du pis, des trayons et des mains des trayeurs avant et/ou après chaque traite) a été évalué en 2011 et en 2012, en comparant la prévalence de vaches positives au test CMT et l’identité des bactéries isolées en présence ou en absence de ces mesures. Au cours de la première étude en 2009 sur la prévalence des vaches positives au test CMT et l’identité des bactéries mammopathogènes, 104 des 265 vaches (39%) testées dans l’ensemble des 3 troupeaux étaient positives au test CMT, bien qu’aucune mammite clinique n’ait été diagnostiquée. Les analyses bactériologiques ont identifié 55 souches bactériennes: la moitié (51%) appartient au genre Staphylococcus, essentiellement à l’espèce S. aureus (42%). Les autres bactéries identifiées appartiennent à la famille des Enterobacteriaceae (26%) et aux genres Enterococcus (13%), Bacillus (9%) et Acinetobacter (2%). Des résultats similaires ont été obtenus en 2010, 2011 et 2012, bien que les pourcentages respectifs puissent varier selon l’année et le troupeau. Les résultats des tests phénotypiques et génétiques du virulotypage (études 1 et 3) des 122 souches de S. aureus isolées de 2009 à 2012 dans les trois troupeaux n’ont permis d’effectuer aucun regroupement. Par contre, les résultats des empreintes génétiques par PFGE sur ces mêmes souches ont montré qu’elles appartiennent à 16 pulsotypes différents, dont trois sont plus fréquents, A (33%), D (23%) et B (21%). Ces différents pulsotypes se distinguent, dans une certaine mesure, par la présence plus fréquentes des gènes icaA, spa et cap5H dans les souches des pulsotypes A et B ; des gènes cap8H, seg, sei et seb dans celles du pulsotype D ; et du gène luks-PV dans celles des pulsotypes B et D. Pour ce qui concerne les antibiogrammes des mêmes 122 souches (études 1 et 2 + résultats non publiés), des pourcentages élevés de souches résistantes de S. aureus, particulièrement aux -lactamines, ont été relevés. Ainsi, 41% des souches testées étaient résistantes à la pénicilline et 7%, à l’oxacilline. Mais, aucune souche résistante à la méticilline (SARM) ne possède le gène mecA. Les pourcentages de souches résistantes atteignaient 11% pour la tétracycline et la gentamicine, mais restaient inférieurs à 5% pour la clindamycine, l’association trimétoprime-sulfaméthoxazole et l’enrofloxacine. Pour la 4ème étude en 2011 et 2012, les mesures d’hygiène ont été appliquées pendant 6 mois : lavage du pis avant la traite, trempage des trayons avec de la chlorhexidine après la traite, et lavage et désinfection des mains des trayeurs avec une solution antiseptique à base d’hypochlorite de sodium. L’application de ces mesures a diminué de manière statistiquement significative les pourcentages de vaches positives au test CMT en comparaison avec les résultats dans les troupeaux et au cours des années sans application de ces mêmes mesures d’hygiène. En 2012, par exemple, les pourcentages de vaches positives au CMT dans les troupeaux « élite » et « non-élite » ont diminué de 65% et 62%, à 44% et 41% après trois mois d’application, puis à 20% et 24% après 6 mois d’application, respectivement. Par contre, ces mesures d’hygiène n’ont eu aucun effet statistiquement significatif sur les pourcentages relatifs des différents pathogènes identifiés. En conclusion, les mammites bovines sévissent essentiellement sous forme sub-clinique à la station sahélienne de Toukounous. Le genre Staphylococcus et l’espèce S. aureus sont les bactéries mammopathogènes les plus fréquemment identifiées. Les souches de S. aureus appartiennent à différents virulotypes et pulsotypes, bien que trois de ces derniers soient plus fréquents dans les trois troupeaux et au cours des quatre années de l’étude. Ces mêmes souches présentent différents profils de résistance aux antibiotiques, avec près de la moitié d’entre elles résistantes à des membres de la famille de -lactames. Enfin, l’application de mesures d’hygiène (lavage et désinfection du pis, des trayons et des mains des trayeurs) avant et/ou après la traite manuelle permet de réduire la prévalence des vaches positives au test CMT de manière statistiquement significative, mais n’a pas d’influence sur les fréquences relatives des bactéries pathogènes identifiées dans les laits. [less ▲]

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See detailWild boar movement ecology across scales: Insights from a population expanding into agroecosystems of Southern Belgium
Morelle, Kevin ULg

Doctoral thesis (2015)

Over the time, ungulates have seen their populations continuously changing under the e ect of direct, i.e. hunting pressure, and indirect, i.e. land-use changes, human activities. Under control until ... [more ▼]

Over the time, ungulates have seen their populations continuously changing under the e ect of direct, i.e. hunting pressure, and indirect, i.e. land-use changes, human activities. Under control until recently, ungulates have progressively adapted to these modi cations and are now able to cope with human-shaped environments, consequently their number and range have greatly and worryingly increased. More particularly, among ungulates species, the wild boar Sus scrofa raises important concerns due to its environmental, economic and social impacts on modern societies. Understanding the ecology of ungulates species and their ability to survive within highly dynamic and seasonal ecosystems, such as agricultural environment, is thus necessary to better mitigate their negative impacts and to sustainably manage growing and expanding populations. Although only recently studied, movement ecology of animal is an important species trait that allows animal to adapt to rapid environmental changes. Considering movement as the resulting interaction of the animal’s internal state, navigation and motion capacity as well as of the e ect of the surrounding environment (“external factors”), provides a clear conceptual framework enabling to study patterns, mechanisms and processes, such as coping with land-use changes. In this thesis, we study the case of an expanding wild boar population in Southern Belgium and consider the movement ecology of the species to understand how wild boar colonize and ourish in agroecosystems. More speci cally, the thesis aims at i) reviewing quantitatively and qualitatively the scienti c literature about wild boar movement ecology, and ii) analyzing the spatial response of wild boar to agroecosystems in terms of movement and habitat selection across three spatial and temporal scales. The literature review highlights that wild boar is the least studied ungulates species in terms of movement ecology.We suggest that this is likely due i) to the relative complexity of tting tracking devices to this species, and ii) to its generalist diet making the species not suitable to test foraging hypotheses. Among existing studies, a large part focuses on the role of external factors (e.g. hunting, landscape features) on movement while others components of the movement ecology framework (internal state, navigation and motion capacity) remain poorly studied. However, when assuming behavioral similarity between wild and domestic boars, experimental studies on captive animals show how wild boar can develop complex movement strategies by using their highly developed cognitive and sensory abilities, and spatial memory. The spatio-temporal analysis suggests a scale-speci c response of wild boar to agricultural habitat. At the intermediate scale (landscape, seasonal), wild boar uses seasonal habitat shift strategies towards agricultural areas, while at broader scale (regional, decades), wild boar avoids this habitat, preferring the forest habitat to spread and extend its occupancy range. This results in a contradiction with our preliminary hypothesis that increased area of cultivations providing cover (maize, rapeseed, cereals) facilitates wild boar population expansion. Furthermore, we show that besides the use of forest habitat, high population density is a major driving factor of the colonization of agroecosystems by wild boar. The ne-scale analysis (home range, daily), highlights the large variety of spatial behaviors (area restricted search, central place foraging, nomadism, dispersing) wild boar is able to use to cope with heterogeneous environments. In terms of management of the species, the results of this thesis suggest that it is required to lower the population density in order to limit the population spread into agroecosystems, not only at the margin of expansion but all over the species’ range. Furthermore, we recommend developing more exible control strategies taking into account both the spatial abilities of the species and the complexity and dynamics of the environment. For example, the creation of a seasonal landscape of fear could be promoted, i.e. reducing attractivity of agricultural lands by increasing risk sensation (e.g. hunting with dogs all along the growing season). However, in our opinion, the success of any management strategy requires rst to tackle the issue of the decreasing number of hunters observed in large part of Europe and to improve communication among the di erent stakeholders (hunting associations, farmers, public administration). Indeed, while ungulates have progressively adapted to human-induced changes, the capacity of humans to adapt to this new human-ungulate relation is questionable. [less ▲]

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See detailEtude du potentiel des sous produits de la filière vinicole pour des applications à haute valeur ajoutée
Berchem, Thomas ULg

Master's dissertation (2015)

Nowadays, there is no longer any doubt about the future fossil fuels rarefaction. It is necessary to find more sustainable ways to produce everyday consumer products faced to an increasing population. Bio ... [more ▼]

Nowadays, there is no longer any doubt about the future fossil fuels rarefaction. It is necessary to find more sustainable ways to produce everyday consumer products faced to an increasing population. Bio-based chemistry and bio-refining are alternative solutions deserving a particular attention. The large amount of green waste produced all around the world represents energy and chemical resources with an under-exploited potential. Wine-making byproducts come from grape growing which is one of the largest crop around world. It seems to be an interesting source of bio-based molecules but, despite this potential, these byproducts are untapped. Their uses are limited to poor value added applications like composting, agricultural spreading or bioethanol. This work focuses on the high value added valorization possibilities of the wine-making byproducts. It takes part in the current trend of using natural bioactive molecules in pharmaceutical, parapharmaceutical or food industry. This study is built around three main objectives: a characterization of the raw material and the development of a method to extract polyphenols. The results shown in this work tend to indicate a high valorization potential of grape pomace thank to the identification of interesting compounds like bioactive molecules and especially polyphenols as well as high concentrations of other molecules of which the valorization potential from wine-making byproducts needs to be explored. [less ▲]

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See detailCaractérisation et étude du potentiel de valorisation des polyphénols de miels monofloraux
Istasse, Thibaut ULg

Master's dissertation (2015)

Honey is a natural sweet substance mainly produced by Apis mellifera L. from flowers nectar or honeydew. It is consumed by humans and used as sweetening agent since ancient times. Nowadays, its main ... [more ▼]

Honey is a natural sweet substance mainly produced by Apis mellifera L. from flowers nectar or honeydew. It is consumed by humans and used as sweetening agent since ancient times. Nowadays, its main valorization is in the food sector. Besides its sweetness, honey also has other interesting properties like an antibacterial action. The origins of this antibacterial action are manifold because although honey contains mainly sugars, it is nonetheless a very complex mixture comprising more than one hundred different components. Factors usually involved in honey antibacterial effect are hydrogen peroxide, the high concentration in sugars, the acidic pH, antimicrobial peptides secreted by bees and polyphenols which are secondary metabolites from plants visited by the bees. Among these factors, polyphenols are of particular interest because they represent a market of hundreds of millions of dollars in the world and exhibit different biological activities: antioxidants, antibacterial, anticancer, antifungal, anti-inflammatory, etc… These observations lead to a question: could honey polyphenols be extracted for high value-added applications? The purpose of this work is to give a beginning of answer. That’s why an extraction method for honey polyphenols was developed. These compounds were sought in six different honey samples: acacia, chestnut, eucalyptus, thyme, sunflower and wild carrot honeys. After the extraction, samples were analyzed by high performance liquid chromatography coupled with UV detection and mass spectrometry. Several polyphenols were identified and quantified in honeys. If the extraction method isn’t recommended at industrial level at this stage of the project, it can, however, be used for analytical purposes. Further development of the method could allow to link honeys to their floral sources. [less ▲]

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See detailDétection des sauts de cycles en mode multi-fréquence pour le système Galileo
Van de Vyvere, Laura ULg

Master's dissertation (2015)

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See detailTime-domain simulation of large electric power systems using domain-decomposition and parallel processing methods
Aristidou, Petros ULg

Doctoral thesis (2015)

Dynamic simulation studies are used to analyze the behavior of power systems after a disturbance has occurred. Over the last decades, they have become indispensable to anyone involved in power system ... [more ▼]

Dynamic simulation studies are used to analyze the behavior of power systems after a disturbance has occurred. Over the last decades, they have become indispensable to anyone involved in power system planning, control, operation, and security. Transmission system operators depend on fast and accurate dynamic simulations to train their personnel, analyze large sets of scenarios, assess the security of the network in real-time, and schedule the day ahead operation. In addition, those designing future power systems depend on dynamic simulations to evaluate proposed reinforcements, whether these involve adding new transmission lines, increasing renewable energy sources, or implementing new control schemes. Even though almost all computers are now parallel, power system dynamic simulators are still based on monolithic, circuit-based, single-process algorithms. This is mainly due to legacy code, written in the 80's, that is still today in the core of the most important commercial tools and does not allow them to fully exploit the parallel computational resources of modern computers. In this thesis, two parallel algorithms belonging to the family of Domain Decomposition Methods are developed to tackle the computational complexity of power system dynamic simulations. The first proposed algorithm is focused on accelerating the dynamic simulation of large interconnected systems; while, the second algorithm aims at accelerating dynamic simulations of large combined transmission and distribution systems. Both proposed algorithms employ non-overlapping decomposition schemes to partition the power system model and expose parallelism. Then, “divide-and-conquer” techniques are utilized and adapted to exploit this parallelism. These algorithms allow the full usage of parallel processing resources available in modern, inexpensive, multi-core machines to accelerate the dynamic simulations. In addition, some numerical acceleration techniques are proposed to further speed-up the parallel simulations with little or no impact on accuracy. All the techniques proposed and developed in this thesis have been thoroughly tested on academic systems, a large real-life system, and a realistic system representative of the continental European synchronous grid. The investigations were performed on a large multi-core machine, set up for the needs of this work, as well as on two multi-core laptops computers. [less ▲]

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See detailHölder Continuity and Wavelets
Simons, Laurent ULg

Doctoral thesis (2015)

There exist a lot of continuous nowhere differentiable functions, but these functions do not have the same irregularity. Hölder continuity, and more precisely Hölder exponent, allow to quantify this ... [more ▼]

There exist a lot of continuous nowhere differentiable functions, but these functions do not have the same irregularity. Hölder continuity, and more precisely Hölder exponent, allow to quantify this irregularity. If the Hölder exponent of a function takes several values, the function is said multifractal. In the first part of this thesis, we study in details the regularity and the multifractality of some functions: the Darboux function, the Cantor bijection and a generalization of the Riemann function. The theory of wavelets notably provides a tool to investigate the Hölder continuity of a function. Wavelets also take part in other contexts. In the second part of this thesis, we consider a nonstationary version of the classical theory of wavelets. More precisely, we study the nonstationary orthonormal bases of wavelets and their construction from a nonstationary multiresolution analysis. We also present the nonstationary continuous wavelet transform. For some irregular functions, it is difficult to determine its Hölder exponent at each point. In order to get some information about this one, new function spaces based on wavelet leaders have been introduced. In the third and last part of this thesis, we present these new spaces and their first properties. We also define a natural topology on them and we study some properties. [less ▲]

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See detailLearning Artificial Intelligence in Large-Scale Video Games: A First Case Study with Hearthstone: Heroes of Warcraft
Taralla, David ULg

Master's dissertation (2015)

Over the past twenty years, video games have become more and more complex thanks to the emergence of new computing technologies. The challenges players face now involve the simultaneous consideration of ... [more ▼]

Over the past twenty years, video games have become more and more complex thanks to the emergence of new computing technologies. The challenges players face now involve the simultaneous consideration of many game environment variables — they usually wander in rich 3D environments and have the choice to take numerous actions at any time, and taking an action has combinatorial consequences. However, the artificial intelligence (AI) featured in those games is often not complex enough to feel natural (human). Today's AI is still most of the time hard-coded, but as the game environments become increasingly complex, this task becomes exponentially difficult. To circumvent this issue and come with rich autonomous agents in large-scale video games, many research works already tried and succeeded in making video game AI learn instead of being taught. This thesis does its bit towards this goal. In this work, supervised learning classification based on extremely randomized trees is attempted as a solution to the problem of selecting an action amongst the set of available ones in a given state. In particular, we place ourselves in the context where no assumptions are made on the kind of actions available and where action simulations are not possible to find out what consequences these have on the game. This approach is tested on the collectible card game Hearthstone: HoW, for which an easily-extensible simulator was built. Encouraging results were obtained when facing Nora, the resulting Mage agent, against random and scripted (medium-level) Mage players. Furthermore, besides quantitative results, a qualitative experiment showed that the agent successfully learned to exhibit a board control behavior without having been explicitly taught to do so. [less ▲]

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See detailEnquêter auprès des sourds. Implications éthiques, méthodologiques et statistiques de l’adaptation d’enquêtes d’opinion au public sourd.
Fontaine, Sébastien ULg

Doctoral thesis (2015)

For technical and logistical reasons, disabled people (and especially deaf people) are excluded from opinion surveys. This leads to the situation that deaf people remain unrepresented in the statistical ... [more ▼]

For technical and logistical reasons, disabled people (and especially deaf people) are excluded from opinion surveys. This leads to the situation that deaf people remain unrepresented in the statistical tendencies emerging from such quantitative opinion surveys. This observation is at the heart of the research presented in this work. This thesis consists of four chapters, each one tackling specific aspects of the implications of this lack of representation of deaf people in opinion surveys. The first chapter gives a short description of the situation of deaf people, from a sociological point of view. The second chapter discusses the moral and ethical issues raised by the lack of representation of deaf people in opinion surveys, in a more philosophical perspective. In the third chapter, we present new adapted methods making it possible to conduct opinion surveys among deaf people. Thanks to a new type of electronic questionnaire including sign language videos, we more specifically show how deaf people can be surveyed for different purposes. On the basis of these new techniques, the final chapter offers a commented statistical analysis of the deaf people situation in French-speaking Belgium. [less ▲]

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See detailDiscrete Element Method Modeling of Ball Mills - Liner Wear Evolution
Boemer, Dominik ULg

Master's dissertation (2015)

Ball mills, i.e. rotating cylindrical drums filled with a feed material and metal balls, also known as the charge, are a major category of grinding devices in mineral processing and cement production ... [more ▼]

Ball mills, i.e. rotating cylindrical drums filled with a feed material and metal balls, also known as the charge, are a major category of grinding devices in mineral processing and cement production. Since the grinding process is excessively energy-intensive and aggressive in terms of wear, a profiled and wear-resistant liner is installed in the mill to transfer energy to the grinding charge more efficiently and to protect the mill shell. Because of the harsh environment inside of the mill and the relatively long lifespan of its liner, the optimization of the liner by the classical way, i.e. experimental testing, is a difficult and slow process. In this thesis, a procedure for predicting the charge motion and the power draw of a ball mill based on the discrete element method (DEM) is calibrated and validated by means of photographs of the charge, and power draw measurements of a 1:5-scale laboratory mill, which were kindly provided by the company Magotteaux International S.A. . This computational method essentially renders future experimental testing unnecessary with respect to these characteristics. Based on this first method, a generic process for predicting the wear distribution and the progressive shape evolution of liner surfaces is developed and validated by the wear profiles of the shell liner in the first chamber of a 5.8 m diameter cement mill monitored during a decade by Magotteaux International S.A. . The energy dissipated by tangential damping defined by the linear spring-slider-damper DEM contact law was found to be the best fitting wear model with respect to the real wear data. The progressive update of the liner geometry by a multi-step procedure delivers relatively accurate results for liners without axial height variation while further investigations are still required for almost fully variable geometries. Nevertheless, detailed phenomena, like the creation of grooves in the liner, were for the first time numerically modeled in this thesis. [less ▲]

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See detailModel polyQ proteins based on the beta-lactamase BlaP: How non-polyQ regions influence the polyQ length-dependent aggregation process
Huynen, Céline ULg

Doctoral thesis (2015)

Neurodegenerative amyloid diseases are fatal disorders representing an important human health and economic burden. Amongst them, nine disorders are classified as polyglutamine (polyQ) diseases, for which ... [more ▼]

Neurodegenerative amyloid diseases are fatal disorders representing an important human health and economic burden. Amongst them, nine disorders are classified as polyglutamine (polyQ) diseases, for which no treatment is yet available. They are all characterized by the pathological expansion of a poly(CAG) sequence, above a specific threshold, within the coding sequence of nine unrelated genes, translated in nine polyQ proteins. The polyQ expansion, the only common point, is the critical determinant for polyQ disease development by triggering protein aggregation into amyloid fibrils. More recent studies however indicate that the protein context modulates the polyQ-induced aggregation process and the disease phenotype. The objectives of my thesis are to deeper investigate the molecular determinants of the complex interplay between the propensity of the polyQ tract to trigger protein aggregation and the modulating role of non-polyQ regions in order to allow the identification of strategies to interfere with the pathological aggregation process. For that purpose, model polyQ proteins, referred to as BlaP-polyQ chimeras, based on the β-lactamase BlaP and polyQ sequences (23 – 79Q) inserted at two positions (197, in between or not unstructured peptides, or 216), are used and their aggregation properties are characterized under several conditions. We first observe that the polyQ length is determinant for BlaP-polyQ chimera aggregation. Indeed, there is a Q-threshold for the aggregation into amyloid fibrils and for fibril elongation. Above this threshold, the aggregation in solution and the elongation rate increase with the length of the polyQ tract, with an exponential rise-to-maximum and a linear regression, respectively, independently of the conformation of the BlaP moiety, and of the position of the polyQ tract within BlaP. Longer polyQ tracts are likely to have a larger conformational flexibility allowing them to more easily adopt an amyloid-aggregation prone conformation. However, the Q-threshold for fibril elongation is much lower than for fibril formation in solution: the polyQ tract requires a larger conformational flexibility to nucleate the formation of fibrils than to elongate them. Secondly, the Q-threshold for fibril formation is lower once the BlaP moiety is unfolded, and BlaP-polyQ chimeras aggregate faster into amyloid fibrils under conditions favoring the unfolding of the BlaP moiety. The native structure of BlaP is likely to impose conformational constraints to moderate and long polyQ tracts that block and decrease, respectively, their propensity to form fibrils. The effects of constraints decrease with the polyQ length. Thirdly, BlaP chimeras with the polyQ tract in position 216 have an increased propensity to trigger the nucleation and the elongation of amyloid fibrils compared to chimeras with the polyQ in position 197. Advanced studies confirm that the propensity of the polyQ tract to aggregate into amyloid fibrils is linked to the conformational flexibility of the polyQ tract, which depends on (i) the polyQ length, (ii) the location of the polyQ tract within BlaP, i.e., a terminal location or embedded within a protein domain, and (iii) the structural properties of the polyQ flanking regions. Finally, we observe that the whole region flanking the polyQ tract in position 197 at its N-terminus has an anti-aggregating property that fully counterbalances the pro-aggregating property of that flanking at the C-terminus. The former imposes strong conformational constraints to the polyQ tract that reduce its conformational flexibility and hence its aggregation propensity. Moreover, these regions are likely to differently affect the solubility of the polyQ protein and hence the driving force for insoluble aggregation. Altogether, our data also suggest that BlaP chimeras aggregate via the commonly described nucleation-dependent polymerization mechanism during which the aggregation is first triggered by polyQ-polyQ interactions, and then a subsequent slight reorganization of the BlaP moiety is required for conversion of aggregates into amyloid fibrils. Based on these results, we should allow the development of therapeutic strategies, targeting specifically the molecular features of the complex interplay between the polyQ and non-polyQ regions during the nucleation and/or elongation of the pathological aggregation of polyQ proteins. [less ▲]

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See detailDevelopment of a new design method for the cross-section capacity of steel hollow sections
Nseir, Joanna ULg

Doctoral thesis (2015)

The cross-sectional behaviour of steel sections can be shown to be influenced by two extreme behaviors: the resistance and the instability. These boundaries are accounted for in current standards through ... [more ▼]

The cross-sectional behaviour of steel sections can be shown to be influenced by two extreme behaviors: the resistance and the instability. These boundaries are accounted for in current standards through a classification system consisting on rules depending on the cross-section dimensions. For example, in EN 1993-1-1, classes are defined spanning from stocky sections (class 1) able to develop their full plastic capacity, to slender sections (class 4) for which the effective properties are used with the use of the effective width method (EWM). However, for cold-formed steel sections, characterized by a non-linear material law, the cross-section resistance can go beyond its plastic capacity due to strain hardening effects. Moreover, with the emergence of high strength steel (i.e. cross-sections falling into class 4) and more complex cross-section shapes, the effective width method is becoming too complicated. Many other reasons and discrepancies are making the cross-section classification too complex and inconsistent. The Overall Interaction Concept (OIC) stands as a new design approach that aims at a straightforward design check of the stability and resistance of steel cross-sections. Based on the use of a generalized relative slenderness and so-called interaction curves, it can be applied to any type of cross-section, further includes potential non-linear material behaviour and covers combined loading cases. The main aim of this thesis is to develop and propose OIC interaction curves dedicated to steel hollow sections subjected to various load cases. A test program was carried out as a part of a European project named ‘HOLLOPOC’ to investigate the cross-sectional behavior of cold-formed hot-finished and hot-rolled square, rectangular and circular sections. 57 cross-sections tests including simple and combined load cases were performed. Besides, a finite element model was developed and calibrated on the basis of the tests, and its accuracy was seen to be sufficient to subsequently undergo an extensive numerical parametric study for hot-rolled and cold-formed cross-sections, leading to over than 40 000 numerical results. Based on these computations, design proposals were made within the context of the Overall Interaction Concept, using an extension of the Ayrton-Perry approach. Finally, a validation of the proposed formulae was made through a comparison with existing approach and worked examples were presented, in order to illustrate (i) the application of the method and (ii) its benefits in comparison to application of current EC3 rules. [less ▲]

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See detailModelling of the response of a slender structure to vortex shedding in the atmospheric boundary layer
Wertz, Freddy ULg

Master's dissertation (2015)

This work is about modelling vortex induced vibrations on a 100 m height generic reinforced concrete pylon with a square cross-section and a 20 height/width ratio, vibrating in its first across-wind ... [more ▼]

This work is about modelling vortex induced vibrations on a 100 m height generic reinforced concrete pylon with a square cross-section and a 20 height/width ratio, vibrating in its first across-wind bending mode at a frequency of 0.35 Hz for a critical wind speed of 14.6 m/s. An equivalent aeroelastic model made of a copper spline modelling the dynamic behaviour and a foam blocks skin modelling the external geometry and adjusting the mass is realized. Similitude laws are discussed based on their relevance in the simulation. The model is validated through experimental modal analysis and is tested in wind tunnel uniform and boundary layer winds. 3 turbulence levels and 4 incidence angles are tested. Measured amplitudes are small (around 5 cm in full scale). The influence of turbulence is qualitatively visible in experimental results. Analytical and numerical estimation procedures are also implemented and discussed: The Eurocode norm, a harmonic load model and the spectral model of Vickery and Clark. The Eurocode approach gives the most conservative estimations and is followed by estimations from the harmonic load model having the correlation length as parameter. The spectral model gives estimations of the order of magnitude of experimental measurements in the wind tunnel for a spectral bandwidth of 0.2 and a correlation length comprised between 1 and 3 times the width of the cross-section. [less ▲]

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See detailOrigine et dynamique des populations d’arbres des forêts denses humides d’Afrique Centrale, le cas de Lophira alata Banks ex Gaertn C.F. (Ochnaceae)
Biwole, Achille ULg

Doctoral thesis (2015)

The canopy of Central African rainforests is characterized by the abundance of light-demanding trees belonging to several species, suggesting that favorable conditions for their regeneration once ... [more ▼]

The canopy of Central African rainforests is characterized by the abundance of light-demanding trees belonging to several species, suggesting that favorable conditions for their regeneration once prevailed. Today this isn’t the case in light of the demographic structure of their populations, which shows a lack of regeneration. The appearance of such species in rainforests is the result of significant and sustainable openings in the forest canopy. Such events may have occurred with climatic changes and / or large-scale anthropogenic disturbances. The risk of their populations decline is increased by the fact that most of them are timber species. This is typically the case of Lophira alata Banks ex Gaertn C.F., which is one of the most important Central African trees harvested, and is considered vulnerable by the IUCN. In the current context where the preservation of the biodiversity and the integrity of the forest cover is a major concern, the present PhD aims to understand the history and ecological requirements of L. alata in order to propose the sustainable management strategies. The history of L. alata has been studied using an approach integrating both anthracology and archeology. We found a large body of evidences (pottery fragments, palm nuts and charcoal) in the forests soil of southern Cameroon indicating human occupation and widespread fires over two periods : 2200 - 1500 years BP, and around 300 years BP. The age of the most recent events coincides with the probable age of the tallest specimens of L. alata. To determine the light requirements of the species and to better define its regeneration strategy, a quantitative study on the guild of juveniles was conducted for two years. The results show that L. alata has both the characteristics of a pioneer species and those of a non-pioneer species. Indeed, at low irradiances (1% of full sunlight), the plants mortality rate was very low and their biomass showed no signs of decline, a behavior observed in all non-pioneer species. By contrast, the response of leaf traits, patterns of biomass allocation, and the maximum growth of plants in the intermediate (23-43% of the relative irradiance) and high (100%) irradiance levels, according to the population origins, are typical of all pioneer species. These results emphasize the importance of the population origins when studying the response to light and the need to define a more encompassing classification system. In terms of the dynamics of mature populations, environmental conditions affect the diameter growth of trees, with better growth being realized in the evergreen forest. Nevertheless, even under these favorable conditions, simulations of the exploitable stocks and their recovery rates indicated a significant decline during the first three cutting cycles, which could lead to a decline in economic activity associated with this species. Our results allowed us to suggest a set of recommendations for the sustainable management of L. alata. [less ▲]

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See detailL'activité de la NADPH oxydase : une nouvelle cible pour la curcumine ?
Derochette, Sandrine ULg

Doctoral thesis (2015)

La NADPH oxydase (Nox2) des neutrophiles (PMNs) est une enzyme multi-protéique responsable de la production d'espèce activées de l'oxygène (ROS) pour la destruction des pathogènes. L'activation excessive ... [more ▼]

La NADPH oxydase (Nox2) des neutrophiles (PMNs) est une enzyme multi-protéique responsable de la production d'espèce activées de l'oxygène (ROS) pour la destruction des pathogènes. L'activation excessive des PMNs est souvent associée à des pathologies mortelles chez le cheval, faisant de l'activité de la Nox2 une cible thérapeutique privilégiée. Le premier but de ce travail, a été de développer une méthode appelée "cell-free system" (CSF) pour mesurer l'activité in vitro de la Nox2 équine. Un inconvénient de cette technique sont les interférences possibles entre les inhibiteurs et la sonde utilisée pour la mesure de l'activité. Sur base de notre CFS, nous avons créé l'EquiNox2, un nouvel outil pharmacologique, pour étudier les interactions entre des inhibiteurs et la Nox2 et leurs effets sur l'assemblage et l'activité de l'enzyme. Cette méthode consiste en la mesure in vitro de l'activité de la Nox2 fixée sur un support solide, ce qui permet d'éliminer les inhibiteurs avant la mesure de l'activité et réduit les interférences citées pour le CFS. Le CFS et l'EquiNox2 ont été validés avec le diphénylène iodonium et le Gp91ds-tat, deux inhibiteurs connus de la Nox2 humaine. Le deuxième but de ce travail, était l'étude du NDS27, un complexe de lysinate de curcumine avec l'hydroxypropyl-β-cyclodextrine (HPβCD) sur la réponse oxydante des PMNs. Le NDS27, n'est pas toxique et est capable d'entrer et d'interagir avec les membranes des PMNs et d'inhiber l'activité de la myéloperoxydase, la Nox2 et la PKCδ (un activateur de Nox2) impliquées dans la production de ROS. Nous avons montré en CFS et EquiNox2 que le NDS27 se fixe fortement à la Nox2 pour empêcher son assemblage et que l'HPβCD, l'excipient du NDS27, en plus de solubiliser et transporter la curcumine, augmente l'action de celle-ci sur les activités de la PKC et la Nox2. L'effet modulateur du NDS27 sur l'activation de la Nox2 ouvre des perspectives thérapeutiques pour traitement des pathologies accompagnées de réactions inflammatoires excessives. [less ▲]

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See detailEtude de la sémaphorine virale codée par le gène A3 de l’herpèsvirus alcélaphin 1
Myster, Françoise

Doctoral thesis (2015)

Among gammaherpesvirus, the Macavirus genus is composed of viruses associated to malignant catarrhal fever (MCF) and other phylogenetically related viruses. MCF is a frequently fatal lymphoproliferative ... [more ▼]

Among gammaherpesvirus, the Macavirus genus is composed of viruses associated to malignant catarrhal fever (MCF) and other phylogenetically related viruses. MCF is a frequently fatal lymphoproliferative disease. Three macaviruses inducing MCF have been entirely sequenced: alcelaphine herpesvirus 2 (AlHV-2), ovine herpesvirus 2 (OvHV-2) and alcelaphine herpesvirus 1 (AlHV-1). Sheep carries OvHV-2 asymptomatically while wildebeest is infected with AlHV-1 without developing any clinical signs or lesions. Both viruses represent the most studied macaviruses. In susceptible ruminants, OvHV-2 and AlHV-1 induce the sheep-associated form and the wildebeest-derived form of MCF (WD-MCF), respectively. Economic consequences of WD-MCF are significant in sub-Saharan Africa. WD-MCF is characterized by the proliferation and infiltration of lymphoblastoid T cells surrounding blood vessels and can be considered as a model for peripheral T cell lymphoma caused by a virus. Rabbits are used as experimental model to study MCF. This species develops clinical signs and lesions that they are indistinguishable from those observed in other susceptible species. Until recently, available data on WD-MCF pathogenesis were limited to the simple description clinical signs and lesions. Recently, it was demonstrated that CD8+ T cells proliferate and that this cellular expansion is associated with a severe increase of the viral load in PBMC and lymphoid organs (Dewals et al., 2008). The cloning of the AlHV-1 genome as an infectious and pathogenic bacterial artificial chromosome (BAC) has greatly facilitated the study of individual gene of AlHV-1 (Dewals et al., 2006). Among herpesviruses, viral semaphorins can only be found in members of the Macavirus genus. OvHV 2 encodes Ov3, and AlHV-2 and AlHV-1 encode A3, both genes encoding a semaphorin homolog. Semaphorins are proteins characterized by a conserved amino-terminal domain, the SEMA domain. The roles of the semaphorins on cytoskeleton dynamics have been widely studied. Viral semaphorins could mediate immune evasion mechanisms or viral dissemination and could be involved in specific properties of macaviruses. The first study of the present thesis was dedicated to the investigation of the pathogenesis of WD-MCF and the role of latency. We investigated the distribution of the AlHV-1 infection in the lesions and demonstrated that the infiltration of CD8+ T cells in different lymphoid and non-lymphoid organs and tissues is directly associated with a non-productive viral infection. The second study focused on the A3 gene of AlHV-1 and its potential functions during WD-MCF. We showed that the A3 gene is expressed during the early phase of the viral infection and encodes a functional semaphorin that was termed AlHV-sema. AlHV-sema was able to induce cell retraction. Despite the observed independent acquisition of pox- and herpesvirus semaphorins, AlHV-sema inhibited phagocytosis by dendritic cells and migration to the draining lymph node through mechanisms similar to poxvirus semaphorin. AlHV-sema could also facilitate viral dissemination or confer immune evasion functions. Next, we investigated whether AlHV-sema could affect WD-MCF induction. We did not observe any effect of the absence of AlHV-sema expression during the development of WD-MCF after rabbit nasal infection. Macaviruses are swine and ruminant gammaherpesviruses responsible for a latent asymptomatic infection in their natural species. The development of MCF in other ruminant susceptible species is due to cross-species transmission. During evolution, the gene selection in susceptible species is certainly reduced due to the fact that these species are dead-end hosts. Thus, it is difficult to address the role of AlHV-1 specific genes in MCF as these genes have evolved in other species. Nevertheless, we brought in this work important insight for our understanding of the pathogenesis of WD-MCF and we identified AlHV-sema as a potential immunoevasion factor. DEWALS B., MYSTER F., PALMEIRA L., GILLET L., ACKERMANN M., VANDERPLASSCHEN A. Ex vivo bioluminescence detection of alcelaphine herpesvirus 1 infection during malignant catarrhal fever. J. Virol., 2011, 85, 6941-6954. MYSTER F., PALMEIRA L., SOREL O., BOUILLENNE F., DEPAUW E., SCHWARTZ-CORNIL I., VANDERPLASSCHEN A., DEWALS B.G. Viral semaphorin inhibits dendritic cell phagocytosis and migration but is not essential for gamma-herpesvirus-induced lymphoproliferation in malignant catarrhal fever. J. Virol., 2015. [less ▲]

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