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See detailFundamental Limitations of High Contrast Imaging Set by Small Sample Statistics
Mawet, D.; Milli, J.; Wahhaj, Z. et al

in Astrophysical Journal (2014), 792

In this paper, we review the impact of small sample statistics on detection thresholds and corresponding confidence levels (CLs) in high-contrast imaging at small angles. When looking close to the star ... [more ▼]

In this paper, we review the impact of small sample statistics on detection thresholds and corresponding confidence levels (CLs) in high-contrast imaging at small angles. When looking close to the star, the number of resolution elements decreases rapidly toward small angles. This reduction of the number of degrees of freedom dramatically affects CLs and false alarm probabilities. Naively using the same ideal hypothesis and methods as for larger separations, which are well understood and commonly assume Gaussian noise, can yield up to one order of magnitude error in contrast estimations at fixed CL. The statistical penalty exponentially increases toward very small inner working angles. Even at 5-10 resolution elements from the star, false alarm probabilities can be significantly higher than expected. Here we present a rigorous statistical analysis that ensures robustness of the CL, but also imposes a substantial limitation on corresponding achievable detection limits (thus contrast) at small angles. This unavoidable fundamental statistical effect has a significant impact on current coronagraphic and future high-contrast imagers. Finally, the paper concludes with practical recommendations to account for small number statistics when computing the sensitivity to companions at small angles and when exploiting the results of direct imaging planet surveys. [less ▲]

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See detailL'organisation spatiale des pôles de compétitivité en Wallonie. Vers une nouvelle géographie économique du territoire wallon ?
Wilmotte, Pierre-François ULg

Master of advanced studies dissertation (2014)

The aim of this work is to present the spatial organization of the six Walloon clusters. Their spatial structure is considered under two approaches: first the proximity question between the actors of R&D ... [more ▼]

The aim of this work is to present the spatial organization of the six Walloon clusters. Their spatial structure is considered under two approaches: first the proximity question between the actors of R&D projects and then the question of Walloon territorial division. The methodology rests on statistics and cartography of the localization of clusters actors. The results reveal the competitive area of Wallonia and the weight of geographic proximity between the actors of innovative projects. [less ▲]

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See detailAssessing the operation rules of a reservoir system based on a detailed modelling-chain
Bruwier, Martin ULg; Erpicum, Sébastien ULg; Pirotton, Michel ULg et al

in Natural Hazards & Earth System Sciences Discussion (2014), 2

According to available climate change scenarios for Belgium, drier summers and wetter winters are expected. In this study, we focus on two muti-purpose reservoirs located in the Vesdre catchment, which is ... [more ▼]

According to available climate change scenarios for Belgium, drier summers and wetter winters are expected. In this study, we focus on two muti-purpose reservoirs located in the Vesdre catchment, which is part of the Meuse basin. The current operation rules of the reservoirs are first analysed. Next, the impacts of two climate change scenarios are assessed and enhanced operation rules are proposed to mitigate these impacts. For this purpose, an integrated model of the catchment was used. It includes a hydrological model, one-dimensional and two-dimensional hydraulic models of the river and its main tributaries, a model of the reservoir system and a flood damage model. Five performance indicators of the reservoir system have been defined, reflecting its ability to provide sufficient drinking, to control floods, to produce hydropower and to reduce low-flow condition. As shown by the results, enhanced operation rules may improve the drinking water potential and the low-flow augmentation while the existing operation rules are efficient for flood control and for hydropower production. [less ▲]

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See detailMultiscale Finite Element Modeling of Nonlinear Quasistatic Electromagnetic Problems
Niyonzima, Innocent ULg

Doctoral thesis (2014)

The effective use of composite materials in the technology industry requires the development of accurate models. Typical such materials in electrotechnical applications are lamination stacks and soft ... [more ▼]

The effective use of composite materials in the technology industry requires the development of accurate models. Typical such materials in electrotechnical applications are lamination stacks and soft magnetic composites, used in the so-called magnetoquasistatic (low frequency) regime. Current homogenization models (e.g. the classical homogenization method, mean field homogenization, ...) fail to handle all the difficulties raised by the modeling of these materials, particularly taking into account the complexity of their microstructure and their nonlinear/hysteretic behaviour. In this thesis we develop a multiscale computational method which allows to effectively solve multiscale magnetoquasistatic problems. The technique is inspired by the HMM (heterogeneous multiscale method), which involves the resolution of two types of problems: a macroscale problem that captures slow variations of the overall solution, and many mesoscale problems that allow to determine the constitutive laws at the macroscale and to construct accurate local fields. Macroscale and mesoscale weak, b-conform and h-conform formulations, are derived starting from the two-scale convergence and the periodic unfolding methods. We also use the asymptotic homogenization method for deriving the homogenized linear material laws and, in the end, we derive scale transitions for bridging the scales. Numerical tests carried out in the two-dimensional case allow to validate the models. In the case of b-conform formulations, it is shown that the macroscale solution approximates well the average of the reference solution and that the resolution of the mesoscale problems allows to reconstruct accurate local fields and to compute accurate Joule losses and this, for materials with (non)linear and hysteretic behavior. Similar findings were obtained for the h-conform formulations. In both cases, the deterioration of the accuracy for mesoscale problems located near the boundary of the computational domain could be treated by defining suit- able mesoscale problems near such boundaries. The extension of the model to three-dimensional problems, to multiphysical problems and the inclusion of the mesoscale domains with a stochastic distribution of phases are also some of the possible prospects for improving this work. [less ▲]

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See detailBioRefine Project: Detection of bioavailability of Metallic Trace Elements in soils by the use of microbial biosensors
Tarayre, Cédric ULg; Hurdebise, Quentin ULg; Fischer, Christophe ULg et al

Poster (2014, September 09)

Zinc, lead and cadmium are the main Metallic Trace Elements (MTEs) found in soils contaminated by the mining industry in Europe. MTEs are spread in the environment because of the disruption of ... [more ▼]

Zinc, lead and cadmium are the main Metallic Trace Elements (MTEs) found in soils contaminated by the mining industry in Europe. MTEs are spread in the environment because of the disruption of biogeochemical cycles caused by human activities. Due to their low mobility and biodegradability, they accumulate in soils where they are strongly bound to particles. It has become necessary to understand interactions between MTEs and the environment and to implement remediation actions. This work is focused on remediation monitoring techniques by using whole cell microbial biosensors able to detect zinc, lead and cadmium. Biosensors provide a signal in response to the bio-available concentration in MTEs, which are valuable for the design of efficient techniques involving bioremediation. Whole cell biosensors used in this work are based on Escherichia coli strains carrying a fluorescent reporter system. The reporter element contains a promoter sensitive to MTEs and a gene coding for the Green Fluorescent Protein (GFP). MTEs activate the synthesis of GFP, which is a very stable protein, causing the accumulation of GFP inside the cells. Then, fluorescence can be measured by flow cytometry. In this study, two biosensors were investigated: E. coli pPzraPgfp and E. coli pPzntAgfp. The last strain provided a linear response to zinc up to 20 mg/l and a curvilinear response to cadmium up to 0.15 mg/l. No detection was highlighted regarding lead. In practical cases, soils and wastes are contaminated by several types of MTEs. Consequently, combined contaminations were also tested. This work allowed highlighting that the strain E. coli pPzntAgfp can be used to assess the bioavailability of cadmium in soils, although the experimental procedure must be improved. This work is supported by the BioRefine Project, a European project in which various member states focus on recovery of inorganics from organic wastestreams. We gratefully acknowledge the INTERREG IVB NWE programme, which financed the BioRefine Project (ref. 320J-BIOREFINE). [less ▲]

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See detailAGE-RELATED MACULAR DEGENERATION (AMD): FROM METABOLOMICS APPROACH TO THE INHIBITION OF PDK AS A NEW THERAPEUTIC TARGET
Arslan, Deniz ULg; Pirotte, Bernard ULg; De Tullio, Pascal ULg et al

Poster (2014, September 09)

Age-related Macular Degeneration (AMD) is a leading cause of vision loss in the western world among people aged 50 or older. 90% of all vision loss due to AMD results from the exudative form, which is ... [more ▼]

Age-related Macular Degeneration (AMD) is a leading cause of vision loss in the western world among people aged 50 or older. 90% of all vision loss due to AMD results from the exudative form, which is characterized by choroidal neovascularization (CNV). Age-related changes that induce pathologic CNV are incompletely understood. A successful application of anti-VEGF approaches in the clinic is obviously a turning point in AMD treatment. Nevertheless, despite such important advances, critical issues remain to be addressed. To better understand the aetiology of this pathology, we used and improved a murine model of laser-induced choroidal neovascularization and applied a 1H NMR metabolomics study. This approach leads to the emergence of different putative biomarkers and to the validation of the CNV model for an experimental study of AMD. Among these “biomarkers”, lactate appears to be clearly involved in the development of AMD. The modulation of their plasma concentration by treatment of the animals with synthetic compounds and more specifically Pyruvate Dehydrogenase Kinase inhibitors (PDK) significantly decrease the impact of laser induced CNV. Starting from these results, the development of new PDHK inhibitors could open the way to innovative treatment opportunities in AMD disease [less ▲]

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See detailDéveloppement de nouvelles méthodes de marquage au fluor-18 pour peptides et oligonucléotides en vue de leur études par tomographie par émission de positons
Flagothier, Jessica ULg

Doctoral thesis (2014)

Positron Emission Tomography is a highly sensitive imaging technique currently available in nuclear medicine for diagnostic. In regard to his physical and nuclear characteristics, fluorine-18 appears ... [more ▼]

Positron Emission Tomography is a highly sensitive imaging technique currently available in nuclear medicine for diagnostic. In regard to his physical and nuclear characteristics, fluorine-18 appears often as the radionuclide of choice for the preparation of short-lived positron-emitter radiotracers for PET studies. The fluorine-18 labelling reaction for biomolecules requires very mild conditions. The current method for highly efficient fluorine-18 labelling of biomolecules is the conjugation of a [18F]prosthetic group with a reactive function on the organic compound. During this thesis, two techniques were developed to label biomolecules via a [18F]prosthetic group: the first one to label tyrosine-containing peptides and the second one to label a siRNA. The first part of this work present the synthesis of the [18F]F-PTAD which is a agent for specific radiolabelling of tyrosine. [18F]F-PTAD was coupled with a tyrosine with a global radiochemical yield (synthesis, coupling, purification) of 20% (DC) and the synthesis lasts 2h30. During the second part of this work, two alkyne-bearing linkers were synthesized. These linkers were ligated with siRNA and then reacted with azide-bearing [18F]prosthetic group via a Huisgen cycloaddition reaction. The [18F]siRNA is then obtained with an global radiochemical yield of 12% (DC) and the synthesis lasts 2h00. In conclusion, two methods for labeling biomolecules have been developed. [less ▲]

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See detailGestión por los actores locales de los recursos físicos, vegetales y animales, para el desarrollo sostenible y la calidad de vida. Una experiencia interdisciplinaria en el valle del Draa, Marruecos
Hornick, Jean-Luc ULg

Scientific conference (2014, September 08)

In 2001, an interdisciplinary team, composed of 22 scientists, developed a methodology aiming at analyzing problems of water resources in Vallée du Draa (Morocco). The issue was studied through 4 points ... [more ▼]

In 2001, an interdisciplinary team, composed of 22 scientists, developed a methodology aiming at analyzing problems of water resources in Vallée du Draa (Morocco). The issue was studied through 4 points of view: (i) disponibility of water, according to a hydrogeological evaluation of the region, (ii) mechanic, technic and physic access to water, taking into account political, cultural and financial sovereign, allowing to guarantee access to water at the levels of nation, region, locality, family and individual, (iii) quality of water and its evolution – rainy, superficial, underground, residual water, water for agriculture and breeding, (IV) efficiency and profitability of water. Water needs appeared to be higher that available resources. Rainy and superficial water supplies appeared to be weak and poorly distributed in time. Strong seasonal change in the level of phreatic layer suggested an overexploitation of aquifers. Valleys were characterized by sedimentation of irrigation canals, exploitation of underground water, remoteness and dispersion of agricultural areas. Social and gender equitability in water distribution and access were poor, leading to desertion and emigration. Water quality was considered as poor. It can be concluded that palm groves allows populations to maintain in an area. Sustainability of the system depend on water access, water quality and profitability. Survival of the system depends on irrigation, rights to water access, and presence of water of quality. [less ▲]

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See detailFamily from afar: Moroccan migration, family practices and the transnational social space
Zickgraf, Caroline ULg

Doctoral thesis (2014)

This dissertation is situated at the crossroads of migration, family and transnational studies. It explores families that span multiple cities and countries due to the migration of one or more relatives ... [more ▼]

This dissertation is situated at the crossroads of migration, family and transnational studies. It explores families that span multiple cities and countries due to the migration of one or more relatives and analyzes their subsequent construction and reconstruction of familyhood across national borders. Through a multi-sited qualitative study into Moroccan family networks with residential nodes in Liège, Belgium and Oujda, Morocco, but also several other destinations, Caroline Zickgraf considers both the material and non-material functions of transnational family practices that together produce and inflate transnational social spaces. She treats both the social and physical geographies of these networks in order to understand how the circulation of people affects the circulation of care but also treats the tensions and asymmetries that characterize their multi-directional cross-border exchanges. [less ▲]

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See detailDesign of a fungal biofilm reactor for recombinant protein production from Aspergillus oryzae
Zune, Quentin ULg; Delepierre, Anissa ULg; Bauwens, Julien ULg et al

Poster (2014, September 07)

Fungi are microorganisms exhibiting high secretive power of various metabolites and have the ability to perform post-translational modifications during protein synthesis. In the field of fermentation ... [more ▼]

Fungi are microorganisms exhibiting high secretive power of various metabolites and have the ability to perform post-translational modifications during protein synthesis. In the field of fermentation industry, they are ideal hosts for secondary metabolites and recombinant protein production. At the industrial-scale, equipments usually required for solid-state or submerged fermentation of filamentous fungi have demonstrated their limitations in terms of productivity, mass transfers or products recovery (1, 2). Recently, fungal biofilm reactors were designed to combine advantages from submerged and solid-state culture and reveal their usefulness for greater secondary metabolites production relative to submerged culture conditions (3). In our work, we propose the design of a fungal biofilm reactor for a recombinant protein production from an Aspergillus oryzae strain containing a GFP reporter gene system under the control of a promoter specifically induced in solid-state conditions. The fungal biofilm reactor is composed of a metal structured packing, having the function of inert support for biofilm growth, immerged or aspersed by a liquid medium. Whereas recombinant protein production is not significantly different at the flask-scale between submerged and biofilm conditions, productivity is higher in the submerged conditions at the bioreactor-scale. Presence of recombinant proteins entrapped in the biofilm matrix highlights a diffusion constraint and a lower mass transfer in our fungal biofilm reactor. However, persistence of a free liquid biomass of low viscosity and fungal biomass retention on the support are attractive for the implementation of a continuous process in our fungal biofilm reactor. Further studies will consider a 2-D proteomic comparison of the extracellular medium from fungal biofilm reactor and submerged culture conditions in order to better understand proteins secretion and identify over-expressed proteins in biofilm conditions. [less ▲]

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See detailStudy of the conditions of conidiation for the bio-fungicide Pseudozyma flocculosa
ZAKI, Omran

Poster (2014, September 07)

Pseudozyma flocculosa is a useful fungus and is used in biological control of mildew. The reproduction of this fungus seems to be exclusively asexual by conidia’s production. The latter physiological form ... [more ▼]

Pseudozyma flocculosa is a useful fungus and is used in biological control of mildew. The reproduction of this fungus seems to be exclusively asexual by conidia’s production. The latter physiological form seems to be resistant to downstream process and storage conditions. Therefore, it represents the most commonly form used in agriculture as Fungicide. However, production of conidia in submerged culture is usually uncertain, often with very low yield. Despite the advantages that P. flocculosa offers in biological control, its use remains largely limited compared with that of chemical fungicides. This is probably due to the difficulty to produce mature conidia with high yields. In this work, our aim is to decipher developmental phases of conidia by this useful strain. We start by conidia production in submerged and semisolid fermentation. We then focus on comparative study of different kinds of obtained conidia. [less ▲]

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See detailRANS and Large Eddy Simulation of the hydrodynamics inside mini-bioreactors designed for stem cell culture
Collignon, Marie-Laure ULg; Martin, Céline; Blanchard, Fabrice et al

Conference (2014, September 07)

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See detailCARACTÉRISATION DE LA DIVERSITÉ GÉNÉTIQUE DE CULTIVARS D’OIGNON (ALLIUM CEPA L.) DU NIGER EN VUE DE LEUR CONSERVATION IN SITU ET DE LEUR AMÉLIORATION
Abdou, Rabiou ULg

Doctoral thesis (2014)

Plante monocotylédone, allogame, entomophile, avec un cycle cultural annuel pour la production des bulbes, bisannuel pour celle des graines, l’oignon est l’un des légumes le plus important au Niger en ... [more ▼]

Plante monocotylédone, allogame, entomophile, avec un cycle cultural annuel pour la production des bulbes, bisannuel pour celle des graines, l’oignon est l’un des légumes le plus important au Niger en raison de son utilisation en alimentation et en médecine. Le semis en pépinière suivi d’un repiquage des planches est le mode de culture le plus fréquent chez les producteurs nigériens. Cette étude explore la diversité génétique des cultivars d’oignon du Niger. La diversité est à comprendre ici au sens de la diversité nommée, la diversité morphologique et la diversité moléculaire. Cette thèse se propose d’utiliser ces trois approches complémentaires pour identifier et caractériser les variétés et écotypes selon la perception des producteurs, de caractériser la diversité morphologique et agronomique à partir des descripteurs du genre Allium établis par Bioversity International, et d’analyser la diversité moléculaire des variétés et écotypes d’oignon du Niger à partir des marqueurs moléculaires microsatellites. Cinquante-deux écotypes nommés ont été inventoriés, mais après analyse et regroupement des synonymes, il ressort que dix-sept écotypes sont cultivés au Niger. Les principaux critères des paysans pour caractériser un écotype local sont la couleur des bulbes et la zone de provenance. Les variables quantitatives et qualitatives les plus distinctives entre les écotypes d’oignon sont la longueur et le diamètre des feuilles, le poids des bulbes, la couleur des feuilles, la forme et la couleur des bulbes, l’uniformité de la forme et de la couleur des bulbes. La distance génétique est plus grande, d’une part, entre les écotypes les plus éloignées géographiquement, et d’autre part, entre les écotypes les plus différents au niveau des caractères morphologiques. Le nombre de morphotypes varie de un à neuf par écotype testé. Les analyses moléculaires confirment la forte variabilité à l’intérieur des écotypes et les conclusions relatives à la distance génétique observée à partir des données morphologiques. A l’issue de ces travaux de caractérisation génétique de l’oignon, il est donc utile de combiner des stratégies de conservation in situ et ex situ, et l’exploitation de ces ressources génétiques pour améliorer la production et la rusticité des cultivars d’oignon du Niger. [less ▲]

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See detailRegards sur la "Wallonie prussienne" et la Première Guerre mondiale
Brüll, Christoph ULg

Conference given outside the academic context (2014)

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See detailCannabis use initiation among adolescents: the predictive role of peers, alcohol, expectancies and internalizing factors.
Schmits, Emilie ULg; Mathys, Cécile ULg; Quertemont, Etienne ULg

Conference (2014, September 05)

Theoretical background: Cannabis is the most commonly used illicit drug among teenagers. Initiation is influenced by environmental factors and personal characteristics, events or experiences. An early ... [more ▼]

Theoretical background: Cannabis is the most commonly used illicit drug among teenagers. Initiation is influenced by environmental factors and personal characteristics, events or experiences. An early initiation increases the risks of problems related to cannabis use (e.g. negative psychosocial effects, delinquent behaviors, mental disorders). Prevent initiation, through the identification of risk/protective factors and their interaction, seems crucial in terms of public health. Research question and significance: This study aimed to examine the progression of use, to identify protective and risk factors of cannabis initiation (including peers, alcohol, expectancies and internalizing factors) and to specifically focus on the influence of social anxiety and its moderators/mediators. Methods: A questionnaire was administered twice to 877 teenagers (49.94% female, M=15.61) with one year interval. Sex, age, demographic variables, peer cannabis use, cannabis-related variables (lifetime, frequency, problems and expectancies), alcohol use, social anxiety, trait-anxiety and depression were assessed through validated scales. Logistic regressions, mediation and moderation analyzes were performed. Results: During the follow-up period, 12.89% of the young participants initiated cannabis use. Several factors significantly predict initiation: alcohol use, peer users, perceptual enhancement and craving effect expectancies. Others factors significantly protect from initiation: negative behavioral effect expectancies and social anxiety. Gender, age, relaxation/social facilitation and cognitive impairment effect expectancies, trait-anxiety and depression do not significantly influence cannabis use initiation. In moderated mediation model, after controlling for relevant variables, social anxiety protected from initiation trough the mediating role of perceptual enhancement and craving effect expectancies. The number of peer users and alcohol use do not moderate this mediation. Negative behavioral effect expectancies do not significantly mediate the relation between social anxiety and cannabis initiation. Interpretation of findings: Through low positive expectancies, adolescents with social anxiety symptoms are less likely to initiate cannabis use than the others, whatever the number of peer users and the alcohol use. Findings are discussed in terms of risk and protective characteristics of relevant factors, in an overall and evolutionary approach including internalizing factors. Results support the identification of internalizing profile of adolescents concerned by prevention or treatment and the importance of social anxiety and expectancies in intervention. [less ▲]

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