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See detailMagnetic shielding with YBCO coated conductors: influence of the geometry on its performances
Wera, Laurent ULg; Fagnard, Jean-François ULg; Levin, G. A. et al

in IEEE Transactions on Applied Superconductivity (2012), 23(3),

A superconducting magnetic shield can be built as a stack of several sections of milled 2G coated conductors. Each section consists of a closed loop where persistent currents can flow and provide a strong ... [more ▼]

A superconducting magnetic shield can be built as a stack of several sections of milled 2G coated conductors. Each section consists of a closed loop where persistent currents can flow and provide a strong attenuation of external dc magnetic fields. The purpose of the present work is to study experimentally several geometries of such magnetic shields made out of YBa2Cu3O7 (YBCO) coated conductors from SuperPower. Our aim is to investigate in detail the influence of the aspect ratio and the number of layers of the assembly on the magnetic shielding properties. In order to do so, the magnetic shield is subjected to an axial quasi-static (“dc”) magnetic field ramped slowly at a fixed sweep rate. A Hall probe is used to measure the local magnetic induction inside the assembly as a function of the appliedmagnetic induction. Results show that the shielding factor, SF, (defined as the ratio between the appliedmagnetic induction and the magnetic induction measured inside the shield) is improved for increasing aspect ratios of the global coated conductor assembly and that the threshold magnetic induction (defined for SF = 10) increases with the number of layers. Using a double layer of 18 sections at T = 77 K, dc magnetic fields up to 56 mT can be shielded by a factor larger than 10. Finally, the effect of an air gap of constant width between coated conductor sections is also characterized.(C) 2012 IEEE [less ▲]

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See detailImpact des services publics et sociaux sur le revenu des ménages belges
Fecher-Bourgeois, Fabienne ULg; Fortemps, Françoise ULg; Sak, Barbara

in D'autres Repères (2012)

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See detailDuration perception: A Developmental Semiology from 2:6 to 13 Years, General Population versus Atypical, Assessment by Parental Questionnaire
SCHOLL, Jean-Marc ULg; Philippe, Paule; Gérard, Paul ULg et al

Conference (2012, December 20)

Introduction Perception of duration has a major impact on the child’s ability to manage everyday life. Usually, the perception of time is considered in its sequential component. To our knowledge, possible ... [more ▼]

Introduction Perception of duration has a major impact on the child’s ability to manage everyday life. Usually, the perception of time is considered in its sequential component. To our knowledge, possible semiological markers for the capacity to apprehend temporal duration have not yet been explored. There are thus no existing tools either for its evaluation (in everyday life) or for the description of its development during childhood. We are thus largely in the dark about how the perception of duration develops during childhood. Hypothesis 1) It is possible to track perception of duration using semiological markers in everyday life; 2) Children with developmental disorders can be expected to develop difficulties in this domain. Method We designed a questionnaire for parents using a Likert scale. The questionnaire was administered to 2 samples from 2:6 to 13 years: 827 in a general population and 297 in a mixed-psychopathological population recruited from the Mental Health Services network. We carried out a multinomial logistic regression and used percentiles curves (P5,50,95). Results In the general population, perception of duration is gradually acquired and full competence is attained by 9 years. The apprehension of sequential time is achieved by 4 years. In the psychopathological sample, mean perception of temporal duration is delayed by 18 months and significant difficulties remain even at 13 years. The apprehension of sequential time is also delayed: even at 13 years it remains low (at percentile 95). We have found no sex-related differences. Discussion Perception of duration is an important developmental feature which has not been taken into account until now. Semiological markers can be used to differentiate typically developing children from clinical populations as to their respective capacities to perceive temporal duration. [less ▲]

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See detailGenomic Association Screening Methodology for High-Dimensional and Complex Data Structures: Detecting n-Order Interactions
Mahachie John, Jestinah ULg

Doctoral thesis (2012)

We developed a data-mining method, Model-Based Multifactor Dimensionality Reduction (MB-MDR) to detect epistatic interactions for different types of traits. MB-MDR enables the fast identification of gene ... [more ▼]

We developed a data-mining method, Model-Based Multifactor Dimensionality Reduction (MB-MDR) to detect epistatic interactions for different types of traits. MB-MDR enables the fast identification of gene-gene interactions among 1000nds of SNPs, without the need to make restrictive assumptions about the genetic modes of inheritance. This thesis primarily focused on applying Model-Based Multifactor Dimensionality Reduction for quantitative traits, its performance and application to a variety of data problems. We carried out several simulation studies to evaluate quantitative MB-MDR in terms of power and type I error, when data are noisy, non-normal or skewed and when important main effects are present. Firstly, we assessed the performance of MB-MDR in the presence of noisy data. The error sources considered were missing genotypes, genotyping error, phenotypic mixtures and genetic heterogeneity. Results from this study showed that MB-MDR is least affected by presence of small percentages of missing data and genotyping errors but much affected in the presence of phenotypic mixtures and genetic heterogeneity. This is in line with a similar study performed for binary traits. Although both Multifactor Dimensionality Reduction (MDR) and MB-MDR are data reduction techniques with a common basis, their ways of deriving significant interactions are substantially different. Nevertheless, effects on power of introducing error sources were quite similar. Irrespective of the trait under consideration, epistasis screening methodologies such as MB-MDR and MDR mainly suffer from the presence of phenotypic mixtures and genetic heterogeneity. Secondly, we extensively addressed the issue of adjusting for lower-order genetic effects during epistasis screening, using different adjustment strategies for SNPs in the functional SNP-SNP interaction pair, and/or for additional important SNPs. Since, in this thesis, we restrict attention to 2-locus interactions only, adjustment for lower-order effects always (and only) implies adjustment for main genetic effects. Unfortunately most data dimensionality reduction techniques based on MDR do not explicitly require that lower-order effects are included in the ‘model’ when investigating higher-order effects (a prerequisite for most traditional, especially regression-based, methods). However, epistasis results may be hampered by the presence of significant lower-order effects. Results from this study showed hugely increased type I errors when main effects were not taken into account or were not properly accounted for. We observed that additive coding (the most commonly used coding in practice) in main effects adjustment does not remove all of the potential main effects that deviate from additive genetic variance. In addition, also adjusting for main effects prior to MB-MDR (via a regression framework), whatever coding is adopted, does not control type I error in all scenarios. From this study, we concluded that correction for lower-order effects should preferentially be done via codominant coding, to reduce the chance of false positive epistasis findings. The recommended way of performing an MB-MDR epistasis screening is to always adjust the analysis for lower-order effects of the SNPs under investigation, “on-the-fly”. This correction avoids overcorrection for other SNPs, which are not part of the interacting SNP pair under study. Thirdly, we assessed the cumulative effect of trait deviations from normality and homoscedasticity on the overall performance of quantitative MB-MDR to detect 2-locus epistasis signals in the absence of main effects. Although MB-MDR itself is a non-parametric method, in the sense that no assumptions are made regarding genetic modes of inheritance, the data reduction part in MB-MDR relies on association tests. In particular, for quantitative traits, the default MB-MDR way is to use the Student’s t-test (steps 1 and 2 of MB-MDR). Also when correcting for lower-order effects during quantitative MB-MDR analysis, we intrinsically maneuver within a regression framework. Since the Student’s t-statistic is the square root of the ANOVA F-statistic. Hence, along these lines, for MB-MDR to give valid results, ANOVA assumptions have to be met. Therefore, we simulated data from normal and non-normal distributions, with constant and non-constant variances, and performed association tests via the student’s t-test as well as the unequal variance t-test, commonly known as the Welch’s t-test. At first somewhat surprising, the results of this study showed that MB-MDR maintains adequate type I errors, irrespective of data distribution or association test used. On the other hand, MB-MDR give rise to lower power results for non-normal data compared to normal data. With respect to the association tests used within MB-MDR, in most cases, Welch’s t-test led to lower power compared to student’s t-test. To maintain the balance between power and type I error, we concluded that when performing MB-MDR analysis with quantitative traits, one ideally first rank-transforms traits to normality and then applies MB-MDR modeling with Student’s t-test as choice of association test. Clearly, before embarking on using a method in practice, there is a need to extensively check the applicability of the method to the data at hand. This is a common practice in biostatistics, but often a forgotten standard operating procedure in genetic epidemiology, in particular in GWAI studies. In addition to the presentation of extensive simulation studies, we also presented some MB-MDR applications to real-life data problems. These analyses involved MB-MDR analyses on quantitative as well as binary complex disease traits, primarily in the context of asthma/allergy and Crohn’s disease. In two of the presented analyses, MB-MDR confirmed logistic regression and transmission disequilibrium test (TDT) results. Part of the aforementioned methodological developments was initiated on the basis of observations of MB-MDR behavior on real-life data. Both the practical and theoretical components of this thesis confirm our belief in the potential of MB-MDR as a promising and versatile tool for the identification of epistatic effects, irrespective of the design (family-based or unrelated individuals) and irrespective of the targeted disease trait (binary, continuous, censored, categorical, multivariate). A thorough characterization of the different faces of MB-MDR this versatility gives rise to is work in progress. [less ▲]

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See detailBrazil in Africa: strategic issues
Santander, Sébastian ULg

in African Geopolitics (2012), 45

Africa seems to be a preferred area of activity for the so-called "emerging countries". Brazil is interested in having closer relations with african countries. It has developed economic, trade, diplomatic ... [more ▼]

Africa seems to be a preferred area of activity for the so-called "emerging countries". Brazil is interested in having closer relations with african countries. It has developed economic, trade, diplomatic and cultural links with Africa. It also tends to develop relations in the field of energy with Nigeria, Angola or even with Algeria as well as a military cooperation with countries like Namibia or South Africa. [less ▲]

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See detailConférence intitulée « Elites, Leadership and Power in Ethnic Communities »
Martiniello, Marco ULg

Scientific conference (2012, December 19)

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See detailAchromatization of nonimaging Fresnel lenses for photovoltaic solar concentration using refractive and diffractive patterns
Languy, Fabian ULg

Doctoral thesis (2012)

In the field of concentrated photovoltaics, the main disadvantage of lenses compared to mirrors lies in their chromaticity: Snell's law is related to the refractive index which is wavelength dependent ... [more ▼]

In the field of concentrated photovoltaics, the main disadvantage of lenses compared to mirrors lies in their chromaticity: Snell's law is related to the refractive index which is wavelength dependent. Consequently, even for purely collimated beams under normal incidence, the maximum concentration achievable with typical lenses made of PMMA is limited to ~1000×. This maximum value becomes even lower when considering Sun's angular aperture. Since the law of reflection is not wavelength dependent, mirrors can theoretically achieve the thermodynamic limit of concentration which is about 46'000×. This thesis aims at the design and the manufacturing of an achromatic Fresnel lens suitable for photovoltaic solar concentration, i.e. combining high concentration, low production cost and tolerance to manufacturing errors. Firstly, we investigated a hybrid lens made of a refractive lens and a diffractive lens. The investigations showed that the concentration ratio could be multiplied by 4. A full chapter is dedicated to the optimisation of blazed diffraction gratings to finally achieve the design of the diffractive lens. Nevertheless, a bilayer diffractive lens is needed to obtain a high diffraction efficiency which makes the diffractive lens highly sensitive to manufacturing errors and consequently not suitable for photovoltaic solar concentration. Purely refractive achromatic Fresnel doublets were then investigated and several designs were compared. They allow for very high concentration ratios in the case of collimated beams under normal incidence, higher than 100'000×. Therefore, contrary to singlets, Fresnel doublets are much more affected by the angular size of the source than by the chromatic aberration. Moreover, it was shown that they are tolerant to manufacturing error, change of temperature and uncertainty on the refractive index. It emerges from this thesis that the concept of achromatic doublets is a tolerant and low-cost production solution to achieve a highly concentrated white flux. Although bilayer diffractive lenses are not suitable for concentrated photovoltaics, the combination of refractive with diffractive structures seems to be promised to a bright future for spectrum splitting applications, including spectrum splitting for concentrated photovoltaics. [less ▲]

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See detailFunctional nanogels as platforms for imparting antibacterial, antibiofilm, and antiadhesion activities to stainless steel
Faure, Emilie ULg; Falentin, Céline ULg; Svaldo Lanero, Tiziana ULg et al

in Advanced Functional Materials (2012), 22(24), 5271-5282

In this work, long-term antibacterial, antiadhesion, and antibiofilm activities are afforded to industrial stainless steel surfaces following a green and bio-inspired strategy. Starting from catechol ... [more ▼]

In this work, long-term antibacterial, antiadhesion, and antibiofilm activities are afforded to industrial stainless steel surfaces following a green and bio-inspired strategy. Starting from catechol bearing synthetic polymers, the film cross-linking and the grafting of active (bio)molecules are possible under environmentally friendly conditions (in aqueous media and at room temperature). A bio-inspired polyelectrolyte, a polycation-bearing catechol, is used as the film-anchoring polymer while a poly(methacrylamide)-bearing quinone groups serves as the cross-linking agent in combination with a polymer bearing primary amine groups. The amine/quinone reaction is exploited to prepare stable solutions of nanogels in water at room temperature that can be easily deposited to stainless steel. This coating provides quinonefunctionalized surfaces that are then used to covalently anchor active (bio) molecules (antibiofi lm enzyme and antiadhesion polymer) through thiol/ quinone reactions. [less ▲]

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See detail« Une ethnographie des ateliers de théâtre-action »
Brahy, Rachel ULg

Scientific conference (2012, December 19)

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See detailEUCAST Where are we Today? What’s New? A difficult road in Belgium.
MELIN, Pierrette ULg

Conference (2012, December 19)

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See detailProfessionalization of human resource management: analytical framework’s proposal
Moreau, Charlotte ULg

Scientific conference (2012, December 18)

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See detailEtude longitudinale des besoins psychosociaux des conjoints de personnes atteintes d'un cancer : hiérarchisation et résolution de problème
Wagener, Aurélie ULg; Jonius, Bénédicte; DEVOS, Martine ULg et al

Poster (2012, December 18)

The existence and importance of psychosocial needs experienced by spouses of cancer patients have been demonstrated repeatedly. In order to reduce these needs, our study assesses the efficacy of the ... [more ▼]

The existence and importance of psychosocial needs experienced by spouses of cancer patients have been demonstrated repeatedly. In order to reduce these needs, our study assesses the efficacy of the combination of two psychotherapeutic methods: psychosocial needs' organisation into a hierarchy and problem solving. Our longitudinal and randomized study comprises three assessment times, separated from three weeks, (T0, T1 and T2) and two groups (experimental and control). At T0, both groups realize the hierarchy of needs. Between T0 and T1, only the experimental group practices problem solving. Then, between T1 and T2, the control group practices this method too. Questionnaires administered at each assessment time are: sociodemographic questionnaire, Hospital Anxiety and Depression Scale (HADS), Psychosocial Needs Inventory (PNI), self-efficacy questionnaire (GSES). Between T0 and T1, a general improvement in scores is expected in both groups: it is expected to be higher in the experimental group who completed the problem solving. Between T1 and T2, scores in the control group should improve to join those obtained by theexperimental group at T1. Thirty-seven people participated: experimental group (N=19, male=12, female=7) and control group (N=18, male=11, female=7). The results confirm our initial hypotheses and emphasize the importance of taking care of cancer patients' spouses. [less ▲]

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See detailDémarches qualité en agro-alimentaire: retour d'expérience des AOP/IGP.
Sindic, Marianne ULg

Conference (2012, December 18)

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See detailClostridium difficile in young farm animals and slaughter animals in Belgium
Rodriguez Diaz, Cristina ULg; Taminiau, Bernard ULg; Vandebroek, Johan et al

in Anaerobe (2012), 18(6), 621-625

Faecal carriage of Clostridium difficile in healthy animals has been reported recently, especially in piglets and calves. However there is limited data about carriage in animals just prior to slaughter in ... [more ▼]

Faecal carriage of Clostridium difficile in healthy animals has been reported recently, especially in piglets and calves. However there is limited data about carriage in animals just prior to slaughter in Europe. The main objective of this study was to determine the presence of C. difficile in pigs and cattle at the slaughterhouse. C. difficile was isolated in 6.9% of the cattle at the slaughterhouse. None of the pig slaughter samples were positive for C. difficile after an enrichment time of 72 h. For complementary data, a short study was conducted in piglets and calves at farms. C. difficile was more prevalent in piglets (78.3%) than in calves (22.2%) on the farms. Regarding the piglet samples, 27.8% of the positive samples were detected without enrichment of stools. The PCR ribotype 078 was predominant in farm animals. Samples isolated from slaughter cattle presented the widest range in PCR-ribotype variety, and the most prevalent PCR ribotype was 118a UCL. The results of this study confirm that C. difficile is present in slaughter animals in Belgium with a large percentage of toxigenic strains also commonly found in humans. [less ▲]

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See detailRisk Horizon and Equilibrium Asset Prices
Hübner, Georges ULg; Lejeune, Thomas ULg

Conference (2012, December 18)

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See detailPhénoménologie des troubles de l'humeur
Englebert, Jérôme ULg

Scientific conference (2012, December 18)

Dans les classifications nosographiques modernes (DSM-IV et CIM-10), comme dans la littérature spécialisée (Akiskal, 2001 ; Akiskal et al., 2006 ; Kasper & Hirschfeld, 2005), la mélancolie et la manie ... [more ▼]

Dans les classifications nosographiques modernes (DSM-IV et CIM-10), comme dans la littérature spécialisée (Akiskal, 2001 ; Akiskal et al., 2006 ; Kasper & Hirschfeld, 2005), la mélancolie et la manie font partie des troubles de l’humeur. Si l’on se met d’accord sur une définition solide de l’humeur , la place de celle-ci, et plus généralement de l’émotion, au sein de ces manifestations psychopathologiques est incontestable. Cependant, doit-on considérer qu’il s’agit de l’« organisateur structurel » de ces deux entités ? Nous pensons que non et tâcherons de démontrer que la mélancolie et la manie sont avant tout des pathologies de l’identité. [less ▲]

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See detailLe ProtiWanze, une alternative économique aux tourteaux de soja et de colza dans l'alimentation des bovins
Lessire, Françoise ULg

Conference given outside the academic context (2012)

Suite à une conscientisation de plus en plus forte de la problématique environnementale, la production de biocarburants s’est développée un peu partout dans le monde. C’est en Wallonie que la plus grande ... [more ▼]

Suite à une conscientisation de plus en plus forte de la problématique environnementale, la production de biocarburants s’est développée un peu partout dans le monde. C’est en Wallonie que la plus grande usine de production de bioéthanol de Belgique, BioWanze, a été inaugurée, en décembre 2008. Le ProtiWanze® est différent des autres co-produits issus de la fabrication de bioéthanol. En effet, il est élaboré à partir d’un substrat unique, le froment alors que le plus souvent les usines de production de biocarburants utilisent comme matières premières le maïs, le seigle, l’orge, la canne à sucre, seuls ou en mélanges en proportions variables suivant les prix du marché. Par conséquent, ces co-produits destinés à l’alimentation animale ont des caractéristiques variant au gré des mélanges sélectionnés alors que le ProtiWanze® est relativement stable. Les principaux atouts du ProtiWanze® sont sa teneur en énergie (1130 VEM) et sa teneur en protéines (280 g Matière azotée totale/kg de matière sèche en moyenne). Il est pauvre en matière sèche (teneur moyenne de 27%) et se présente sous forme liquide, ce qui réduit sa valeur d’encombrement au niveau du rumen. L’incorporation du ProtiWanze® dans l’alimentation des bovins en Wallonie a fait l’objet d’un suivi par l’Université de Liège et a été testé chez les vaches laitières, les vaches allaitantes et les taureaux à l’engrais et ce 2 années consécutives. Les résultats tant zootechniques qu’économiques liées à l’utilisation de cet aliment font l’objet de cette présentation. [less ▲]

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See detailMémoire et Science politique
Jamin, Jérôme ULg

Scientific conference (2012, December 18)

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