References of "Scientific congresses and symposiums"
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See detailToggling a genetic switch using reinforcement learning
Sootla, Aivar; Strelkowa, Natalja; Ernst, Damien ULg et al

in Proceedings of the 9th French Meeting on Planning, Decision Making and Learning (2014, May)

In this paper, we consider the problem of optimal exogenous control of gene regulatory networks. Our approach consists in adapting an established reinforcement learning algorithm called the fitted Q ... [more ▼]

In this paper, we consider the problem of optimal exogenous control of gene regulatory networks. Our approach consists in adapting an established reinforcement learning algorithm called the fitted Q iteration. This algorithm infers the control law directly from the measurements of the system’s response to external control inputs without the use of a mathematical model of the system. The measurement data set can either be collected from wet-lab experiments or artificially created by computer simulations of dynamical models of the system. The algorithm is applicable to a wide range of biological systems due to its ability to deal with nonlinear and stochastic system dynamics. To illustrate the application of the algorithm to a gene regulatory network, the regulation of the toggle switch system is considered. The control objective of this problem is to drive the concentrations of two specific proteins to a target region in the state space. [less ▲]

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See detailToggling a genetic switch using reinforcement learning
Sootla, Aivar; Strelkowa, Natalja; Ernst, Damien ULg et al

in Proceedings of the 9th French Meeting on Planning, Decision Making and Learning (2014, May)

In this paper, we consider the problem of optimal exogenous control of gene regulatory networks. Our approach consists in adapting an established reinforcement learning algorithm called the fitted Q ... [more ▼]

In this paper, we consider the problem of optimal exogenous control of gene regulatory networks. Our approach consists in adapting an established reinforcement learning algorithm called the fitted Q iteration. This algorithm infers the control law directly from the measurements of the system’s response to external control inputs without the use of a mathematical model of the system. The measurement data set can either be collected from wet-lab experiments or artificially created by computer simulations of dynamical models of the system. The algorithm is applicable to a wide range of biological systems due to its ability to deal with nonlinear and stochastic system dynamics. To illustrate the application of the algorithm to a gene regulatory network, the regulation of the toggle switch system is considered. The control objective of this problem is to drive the concentrations of two specific proteins to a target region in the state space. [less ▲]

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See detailFirst prototypes of vortex retarders obtained by polarization holography
Piron, Pierre ULg; Blain, Pascal ULg; Décultot, Marc ULg et al

in Proceedings of SPIE (2014, May), 9099

This paper will present the first prototypes of vortex retarders made of photo-orientable liquid crystals polymers recorded without mechanical action using only polarization holography. Vortex retarders ... [more ▼]

This paper will present the first prototypes of vortex retarders made of photo-orientable liquid crystals polymers recorded without mechanical action using only polarization holography. Vortex retarders are birefringent plates characterized by a uniform phase retard and a rotation of their fast axis along their center. Liquid crystals are anisotropic molecules possessing birefringent properties. They are locally orientable and their orientation defines the fast axis orientation of the retarder. Their alignment depends on the local orientation of the recording electric field. The superimposition of several polarized beams will be used to shape the electric field to achieve the recording of vortex retarders. The mathematical aspects of the superimposition process, as well as several numerical simulations are exposed. Finally, the first prototypes are presented, characterized and compared to the numerical simulations. [less ▲]

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See detailSEDIMENTS OXIDATION BY SEAGRASSES: INFLUENCE ON THE S CYCLE IN POSIDONIA OCEANICA (L.) DELILE INTERMATTES DYNAMIC
Abadie, Arnaud ULg; Lejeune, Pierre; Pergent, Gérard et al

Poster (2014, May)

The Mediterranean seagrass Posidonia oceanica forms meadows and develops a complex of rhizomes, roots and sediment which is called “matte”. P. oceanica meadows show discontinuity patterns in the form of ... [more ▼]

The Mediterranean seagrass Posidonia oceanica forms meadows and develops a complex of rhizomes, roots and sediment which is called “matte”. P. oceanica meadows show discontinuity patterns in the form of sand or dead matte (matte without living shoots) patches, called “intermattes”, which can have natural or anthropogenic origins. Mechanical processes (e. g. currents, anchoring) can initiate intermattes formation but their dynamic after creation seems to be linked with the sediment chemistry, especially with S cycle. P. oceanica plays an important role in controlling coastal belowground biogeochemistry, in particular by oxidizing sediments through the release of O2 by roots. This process allows creating more suitable condition for plant growth and colonization. The lack of H2S oxidation in SO4 2- can lead to limitation of the plant development or its regression. In order to investigate the effect of oxidation condition in sediments on intermattes dynamic and the neighboring meadow, we initiate, in December 2013, a study on six intermattes (three natural, three anthropogenic) at different depths in Calvi Bay, in Corsica (France). We hypothesize that redox potential and H2S concentration in sediments play an important role in the regression of P. oceanica meadows, particularly after a mechanical anthropic impact like anchoring. It also may be possible that two different kinds of processes are involved for each type of intermatte. Regular samplings throughout two years are planed with the aim of evaluating the seasonal variations of physicochemical parameters. [less ▲]

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See detailA hybrid human-computer approach for large-scale image-based measurements using web services and machine learning
Marée, Raphaël ULg; Rollus, Loïc ULg; Stevens, Benjamin ULg et al

in Proceedings IEEE International Symposium on Biomedical Imaging (2014, May)

We present a novel methodology combining web-based software development practices, machine learning, and spatial databases for computer-aided quantification of regions of interest (ROIs) in large-scale ... [more ▼]

We present a novel methodology combining web-based software development practices, machine learning, and spatial databases for computer-aided quantification of regions of interest (ROIs) in large-scale imaging data. We describe our main methodological choices, and then illustrate the benefits of the approach (workload reduction, improved precision, scalability, and traceability) on hundreds of whole-slide images of biological tissue slices in cancer research. [less ▲]

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See detailEffects of two PBDE congeners on the moulting enzymes of the freshwater amphipod Gammarus pulex.
Gismondi, Eric ULg; Thomé, Jean-Pierre ULg

Poster (2014, May)

Polybrominated diphenyl ethers (PBDEs) constitute a class of chemical compounds included to the composition of usual products such as plastics, textiles or electrical equipment, due to their flame ... [more ▼]

Polybrominated diphenyl ethers (PBDEs) constitute a class of chemical compounds included to the composition of usual products such as plastics, textiles or electrical equipment, due to their flame retardants properties. Since 2004, PBDEs were banned in Europe and listed as Priority Substances within the European Union Water Frame Work Directive. Unfortunately, the release of PBDEs always occurs in ecosystems due to their presence in products currently in use and new products manufactured using recycled PBDE-containing material. However, only few studies have investigated their impacts on freshwater invertebrates. This work aimed to study the effects of BDE-47 and BDE-99 congeners on the chitobiase and chitinolytic enzymes activities of the freshwater amphipod Gammarus pulex, according to gender, PBDE concentration and time of exposure. In addition, the bioaccumulation of BDE-47 and BDE-99 were measured. The results revealed that there was a dose-response relationship for the PBDE accumulation in G. pulex, whatever the gender and the PBDE congeners. Female G. pulex bioaccumulated more PBDE than males, and especially BDE-99 which was more accumulated than BDE-47. Moreover, PBDE exposures for 96hrs have caused the inhibition of chitobiase and chitinolytic enzymes activities. This study not only indicate the importance of taking into account various confounding factors (gender, congeners, concentration) to understand the PBDE effects, but underline also disruptions of enzymes activities involved in the molting process. These disturbances suggest effects on the gammarid development and reproduction, and consequently on the gammarid population. [less ▲]

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See detailCorrelation between composition and cold stability of palm liquid fractions.
Danthine, Sabine ULg; Lefebure, Emilie ULg; Dijkmans, Peggy et al

Poster (2014, May)

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See detailAnalyse socio-cognitive des modes de schémas précoces inadaptés et des caractéristiques de personnalité au sein d’une population de femmes victimes de violences conjugales
Garcet, Serge ULg; Perick, Thomas ULg

Conference (2014, May)

La violence à l’égard des femmes fait depuis longtemps débat dans le champ de la victimologie. De la vision historique de la victime « coupable » à la victime « innocente » des mouvements féministes, les ... [more ▼]

La violence à l’égard des femmes fait depuis longtemps débat dans le champ de la victimologie. De la vision historique de la victime « coupable » à la victime « innocente » des mouvements féministes, les enjeux moraux déterminent le plus souvent les arguments des parties dans une dialectique militante, de revendication et de rapport de force. Se plaçant résolument dans une position scientifique, la présente étude analyse au sein d’une population de femmes victimes de violences conjugales rencontrées dans le cadre d’expertises pré-sententielles, l’influence des représentations précoces inadaptées (schémas) selon la classification de J. Young sur la perception de la relation. Dans une perspective sociocognitive, l’étude mesure la prévalence de différents schémas précoces dysfonctionnels et envisage comment ceux-ci contribuent chez la victime adulte au maintien d’une vision dévalorisée d’elle-même et d’un rapport inégalitaire à l’altérité propice à l’émergence de comportements violents. L’étude analyse également l’impact de ces schémas sur la construction de la personnalité adulte et met en évidence la fréquence de certains modes préférentiels de personnalité selon les classifications DSM-IV/V au sein de cette population de femmes victimes. [less ▲]

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See detailExpression of peroxisome-proliferator activated receptor alpha in pituitary tumours
Rotondi, S; Modarelli, A; Rostomyan, Liliya ULg et al

in Endocrine Abstracts (2014, May)

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See detailFemmes auteures d’homicide en détention : des liens d’attachement aux ruptures de liens
Glowacz, Fabienne ULg; Bernardello, Sandrine; Résimont, Isabelle

Poster (2014, May)

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See detailLiens entre le statut socio-économique et la consommation de substances chez les adolescents : Quelles incidences pour les filles et les garçons ?
Mathys, Cécile ULg; Hénin, Tamara; Glowacz, Fabienne ULg

Conference (2014, May)

La consommation de substances à l’adolescence constitue une conduite à risque qui n’en est pas moins populaire chez les jeunes. Ses facteurs explicatifs sont régulièrement examinés, toutefois, les liens ... [more ▼]

La consommation de substances à l’adolescence constitue une conduite à risque qui n’en est pas moins populaire chez les jeunes. Ses facteurs explicatifs sont régulièrement examinés, toutefois, les liens qui unissent le statut socio-économique et la consommation de substances ne sont toujours pas clairs. Par exemple, le concept de statut socio-économique reste difficilement appréhendable du point de vue de l’adolescent et la question de la différence entre les genres demeure. Cette étude se propose d’analyser dans quelle mesure le statut socio-économique peut prédire, directement et par effet d’interaction avec l’estime de soi, autre prédicteur examiné, la consommation d’alcool et de substances illicites au sein des deux sexes. Des mesures auto-rapportées et standardisées ont été administrées à 330 adolescents, âgés de 14 à 17 ans, et provenant de différents types d’enseignement de la Fédération Wallonie-Bruxelles, respectivement 162 filles (moy. âge = 15,6 ans) et 168 garçons (moy. âge = 15,6 ans). A l’aide de statistiques réalisées par SPSS, nous pouvons premièrement montrer une différence significative dans la consommation de substances entre les filles et les garçons (t (328) = 2,21, p= 0,03). Deuxièmement, le statut socio-économique ne serait pas significatif chez les garçons (b = 0,48, 95% CI [-0,59, 1,56], t = 0,89, NS), tandis qu’il expliquerait marginalement la consommation de substances chez les filles (b = 0,11, 95% CI [-0,003, 0,21], t = 1,91, p = 0,06). D’autre part, la relation positive entre le statut socio-économique et la consommation de substances s’avèrerait plus forte lorsque les jeunes filles présentent des niveaux peu élevés d’estime de soi (b = -0,33, 95% CI [-0,06, -0,004], t = -2,27, p = 0,02). Cette étude se conclut par une discussion concernant l’implication de ces résultats, notamment en matière de compréhension des facteurs explicatifs de la consommation d’alcool et de substances illicites chez les filles et chez les garçons. [less ▲]

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See detailProcessing of alloy Ti-6Al-4V and of stainless steel 316L by Laser Beam Melting
Mertens, Anne ULg; Paydas, Hakan ULg; Reginster, Sylvie ULg et al

Conference (2014, May)

Additive manufacturing processes such as Selective Laser Melting (SLM) appear very promising in view of the economic production of near-net-shape, complex and (almost) fully dense parts from metallic ... [more ▼]

Additive manufacturing processes such as Selective Laser Melting (SLM) appear very promising in view of the economic production of near-net-shape, complex and (almost) fully dense parts from metallic materials such as Ti alloys and stainless steels. Practically, in SLM, a metallic powder is deposited layer-by-layer in a powder bed and then molten locally according to the desired shape. An important feature of this process is that the structure undergoes an ultra-fast cooling once the beam leaves the working zone, thus giving rise to strongly out-of-equilibrium microstructures. In the case of Ti alloy Ti-6Al-4V, in particular, the microstructural anisotropy resulting from the epitaxial growth of the newly deposited layer on the material previously solidified has been shown to exert a very strong influence on the mechanical properties [1] In the present work, the thermophysical behaviour of Ti-alloy Ti-6Al-4V and of stainless steel 316L has been characterised in details, in order to reach a better understanding of the phenomena controlling the microstructures and mechanical properties of parts. In particular, the thermal conductivity of Ti-alloy Ti-6Al-4V and of stainless steel 316L at high temperature has been determined by combining dilatometry, Differential Scanning Calorimetry (DSC) and laser flash diffusivimetry based on Laplace’s equation. Since Ti-alloy Ti-6Al-4V and stainless steel 316L exhibit quite different physical behaviours, their careful comparison is shown to shed more light into the role of phenomena such as epitaxial growth, out-of-equilibrium phase transformations and/or internal stresses in the additive manufacturing of metallic materials. [less ▲]

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See detailDesign of a reliable processing pipeline for the non-intrusive measurement of feet trajectories with lasers
Pierard, Sébastien ULg; Azrour, Samir ULg; Van Droogenbroeck, Marc ULg

in International Conference on Acoustics, Speech, and Signal Processing (ICASSP) (2014, May)

Reliable measurements of feet trajectories are needed in some applications, such as biomedical applications. This paper describes the data processing pipeline used in GAIMS, which is a non-intrusive ... [more ▼]

Reliable measurements of feet trajectories are needed in some applications, such as biomedical applications. This paper describes the data processing pipeline used in GAIMS, which is a non-intrusive system that measures feet trajectories based on multiple range laser scanners. Our processing pipeline relies on a new tracking paradigm, and it is based on two innovative algorithms: the first algorithm localizes the feet directly from the observed point cloud without any clustering, and the other algorithm identifies the feet. After reviewing the various types of noise affecting the point cloud, this paper explains the limitations of the classical processing approach and gives an overview of our new pipeline. The effectiveness of the proposed approach is established by discussing the results that have been obtained in several studies based on GAIMS. [less ▲]

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See detailImprovement in non-linear guitar loudspeaker sound reproduction
Schmitz, Thomas ULg; Embrechts, Jean-Jacques ULg

in International Conference on Systems, Signals and Image Processing (2014, May)

This paper proposes a study of the accuracy of a guitar amplifier loudspeaker simulation. The simulation is based on a non-linear convolution of a signal using Volterra kernels, which are measured in ... [more ▼]

This paper proposes a study of the accuracy of a guitar amplifier loudspeaker simulation. The simulation is based on a non-linear convolution of a signal using Volterra kernels, which are measured in anechoic conditions with a sine-sweep technique. In this paper, we propose an evaluation of the method to minimise the cost in CPU load, while keeping the best performance in the sound reproduction. To assess the performance of the method, we measure errors between the simulated and real sounds. Human listening tests are moreover proposed in order to determine the minimum level of accuracy leading to unaudible differences with the real loudspeaker.. [less ▲]

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See detailThiamine and benfotiamine improve memory, decrease depressive-like behavior and reduce brain expression of GSK3 beta in mice
Markova, N; Shevtsova, E; Vignisse, Julie ULg et al

Poster (2014, May)

An increasing body of evidence suggests an implication of altered thiamine metabolism in mental illnesses, including depression and Alzheimer’s disease. Here, we examined the effects of a two-week ... [more ▼]

An increasing body of evidence suggests an implication of altered thiamine metabolism in mental illnesses, including depression and Alzheimer’s disease. Here, we examined the effects of a two-week treatment with thiamine (200 mg/kg/day) or benfotiamine (200 mg/kg/day, a synthetic thiamine precursor of high bioavailability, on learning of C57 mice in step down avoidance (SDA) and fear conditioning (FC) tests and depressive-like behavior in the modified forced swimming test (modFST). In addition, we investigated the effects of these drugs on brain gene expression of Glycogene Synthase Kinase 3beta (GSK3b), a regulatory factor that is involved in both above-mentioned mental conditions. Benfotiamine, but not thiamine significantly increased contextual learning in C57 mice in the step-down paradigm and acquisition of fear conditioning during weak training. Both compounds have improved the extinction of contextual fear conditioning memory and did not alter the acquisition of fear conditioning during strong training. Also, we found that both treatments reduced depressive-like behavior in mice, as shown by diminished duration of floating behavior in the modified forced swim test. With the modified forced swimming test applied here, an additional swimming session was carried out 120 hours after the first trial and resulted in increased mRNA levels of GSK3b in the prefrontal cortex, which correlated with duration of floating in tested mice. Thiamine and benfotiamine reduced GSK3b expression in the prefrontal cortex and the hippocampus that was more pronounced in the animals with low floating, in case of the measurements made in the prefrontal cortex. Together, these data suggest pro-cognitive and antidepressant-like effect of benfotiamine that are partly shared by thiamine and can be mediated by their inhibitory effect on the GSK3b [less ▲]

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See detailGrowth Factors-Induced Angiogenesis Requires uPAR on Endothelial Cells
Paques, Cécile ULg; Herkenne, Stéphanie ULg; Pollenus, Thomas et al

Poster (2014, May)

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See detailConstruire son projet professionnel dès la 1ère année d'étude en logopédie à l'université
Martinez Perez, Trecy ULg; Maillart, Christelle ULg; Peters, Stéphanie ULg

Conference (2014, May)

Le monde du travail contribue à la construction professionnelle, mais dans un contexte spécifique, limitant ainsi l’ampleur du développement de cette identité professionnelle. Au contraire, la formation ... [more ▼]

Le monde du travail contribue à la construction professionnelle, mais dans un contexte spécifique, limitant ainsi l’ampleur du développement de cette identité professionnelle. Au contraire, la formation initiale prépare à un champ professionnel et non à un contexte spécifique, jouant par conséquent un rôle essentiel dans l’amorce du développement professionnel (Beckers, 2007). Dans cette optique, un nouveau cours est désormais inscrit dans le programme des étudiants en 1ère année de bachelier de Psychologie et Sciences de l’Education–Orientation Logopédie à l’Université de Liège. Ce cours, intitulé "Approches des métiers de logopède", a pour but d’accompagner les étudiants dans la construction de leur projet professionnel et de leur représentation du métier de logopède. Plus précisément, il permet aux étudiants (a) d’approcher les différentes compétences du logopède, (b) de découvrir un éventail de réalités professionnelles du logopède, (c) et d’initier une réflexion sur les pratiques professionnelles du logopède. Par ailleurs, ce cours découle de la confrontation entre le programme et le Référentiel de Compétence du Logopède de l’Université de Liège (Maillart, Grevesse, & Sadzot, 2010) : il vise à travailler une série d’apprentissages critiques non abordés par ailleurs dans le cursus des étudiants. Les objectifs du cours sont travaillés à travers une diversité de méthodes : création et appropriation d’une carte heuristique, interventions d’une dizaine de professionnels logopèdes, concertations collectives et en sous -groupes, auto-évaluation par l’étudiant, séances plénières, conférences et lectures. Ce cours concerne la quarantaine d’étudiants inscrits dans l’orientation Logopédie en 1ère année de bachelier. La construction du projet professionnel et de la représentation du métier de logopède étant un processus évolutif, ce cours se répartit sur l’entièreté de l’année académique et une continuité de ce cours en 2ème et 3ème année de bachelier est actuellement à l’étude. Les résultats de ce nouveau dispositif seront présentés et discutés lors du colloque. [less ▲]

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See detailLong-term evolution and seasonal modulation above Jungfraujoch (46.5°N, 8.0°E): Optimisation of the retrieval strategy, comparison with model and independant observations
Bader, Whitney ULg; Stavrakou, J; Muller, J-F et al

Poster (2014, May)

Methanol (CH3OH) is the second most abundant organic compound in the Earth’s atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and ... [more ▼]

Methanol (CH3OH) is the second most abundant organic compound in the Earth’s atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5°N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected 8 band of CH3OH. Two wide spectral intervals have been defined and adjusted in order to maximize the information content. Methanol does not exhibit a significant trend over the 1995-2012 time period, but a strong seasonal modulation characterized by maximum values and variability in June-July, minimum columns in winter and a peak-to-peak amplitude of 130 %. In situ measurements performed at the Jungfraujoch and ACE-FTS occultations give similar results for the methanol seasonal variation. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations. [less ▲]

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See detailQuantitative multi-parameter mapping in parkinson’s disease: preliminary results
Rouillard, Maud ULg; D'Ostilio, Kevin ULg; Albinet, Cedric et al

Poster (2014, May)

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See detailSustainable Resource Availability : Ge, Ni, Al three contrasting stories
Pirard, Eric ULg

Conference (2014, May)

The sustainable availability of raw materials used in manufacturing advanced products is a question that consumers will raise more and more in the future. In order to answer this legitimate request it is ... [more ▼]

The sustainable availability of raw materials used in manufacturing advanced products is a question that consumers will raise more and more in the future. In order to answer this legitimate request it is mandatory to define characterization factors capable of taking into account the geological scarcity of an element but also the social and environmental impact of its exploitation and beneficiation. Recent studies (Vieira et al. 2012; Swart el al. 2013) have focused on decreasing ore grades as rough indicators, but clearly such indicators can be severely biased by breakthrough innovations in mining technologies as well as by high metal prices generated by increasing demand. In this paper, we will briefly review three metals that could technically be extracted from very different social and natural environments: Germanium is nowadays mainly a byproduct of coal burnt in China, but could as well be gained from alternative sources such as zinc sulfides. Aluminium is produced from bauxite with Gallium as a byproduct but could technically be extracted from alternative resources such as regionally available clays. Finally, the world nickel production follows two very different processing routes starting either from silicates (laterite deposits) or from sulfides (ultramafic magmas). By comparing the geological; environmental and social impact of mining operations for these three metals, we will try to show what is hidden behind simple ore grades and what indicators should be taken into account in a more complex analysis of sustainable availability. The intention is to build a geographical information system (GIS) of mineral resources and mining operations to help product manufacturers in properly selecting their raw materials providers. Vieira, M.D.M., Goedkoop, M.J., Storm, P. and Huijbregts, M.A.J., 2012, Ore grade decrease as a life cycle impact indicator for metal scarcity : The case of copper. Environ. Sci. Technol. 46, 12772-12778 Swart, P. and Dewulf, J., 2013, Quantifying the impacts of primary metal resource use in life cycle assessment based on recent mining data. Resources, Conservation and Recycling, 73, 180-187. [less ▲]

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See detailFirst conclusions from the Belgian stakeholder panel: FP 7 PREPARE, WG 3 “Consumer Goods”
Turcanu, Catrinel; Olyslaegers, Geert; Camps, Johan et al

Conference (2014, May)

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See detailWhat you should know before starting minimal invasive liver resection: an overview
DETRY, Olivier ULg

in Acta Chirurgica Belgica (2014, May), 114(3), 117

Laparoscopic liver surgery has evolved over the last 2 decades. Advancements in surgical technology, surgical technique, and postoperative care have aided in lifting barriers to laparoscopic liver ... [more ▼]

Laparoscopic liver surgery has evolved over the last 2 decades. Advancements in surgical technology, surgical technique, and postoperative care have aided in lifting barriers to laparoscopic liver resections (LLR). LLR might decrease morbidity and hospitalisation stay compared to open approach, and importantly in liver surgery, may decrease postoperative costal pain. However, in hepatic surgery as in all abdominal procedures, laparoscopic approach is a mean but not a goal. The possibility of LLR should neither modify indications for surgery nor the type of resection. Physiologic modifications induced by CO2 pneumoperitoneum should be known by the surgical and anaesthetic team involved in LLR. Pneumoperitoneum decreases cardiac output, and this decrease could be worsened by the reverse Trendelenburg position and by hepatic hilar clamping. CO2 pneumoperitoneum decreases hepatic blood flow. This is a clear advantage for limiting blood loss during LLR, but this also might increase liver ischemia during Pringle liver hilum clamping, a manoeuvre that should be avoided in LLR. Low venous pressure might decrease blood loss by the small supra hepatic veins, but may also further decrease cardiac output. Several devices may be used for liver section, without evidence of the superiority of one device compared to others. Endo GIA might be very helpful to control the major liver vessels, as branches of portal vein or suprahepatic veins. Significant CO2 embolism is a rare complication, and conversion to open approach for haemorrhage should be performed only if blood loss is controlled. Up to now, there is no clear scientific evidence that laparoscopic approach provides any advantage compared to open approach. SILS, LESS or even robotic approaches should only considered as purely experimental. Current barriers to LLR will continue to fall in the future. [less ▲]

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See detailLa mineuse de la tomate et ses risques agriculturaux
De Backer, Lara ULg; Verheggen, François ULg

Conference (2014, May)

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See detailAdolescents et délinquance : Quelles représentations de la sexualité et de la pornographie, pour quelle sexualité ?
Puglia, Rosa ULg; Glowacz, Fabienne ULg

Conference (2014, May)

Bien que la pornographie ne soit pas un phénomène nouveau, ses supports, ses modalités d’accès, son public, etc. se sont vus modifiés suite à l’avènement des nouvelles technologies. Ainsi, de nos jours ... [more ▼]

Bien que la pornographie ne soit pas un phénomène nouveau, ses supports, ses modalités d’accès, son public, etc. se sont vus modifiés suite à l’avènement des nouvelles technologies. Ainsi, de nos jours, les adeptes de ce média peuvent d’un simple clic visionner une variété d’images et de films à caractère pornographique de manière anonyme et gratuite. Alors que de nombreuses questions se posent quant à l’influence de ces médias sur le développement psycho-sexuel et sur les conduites des adolescents, peu d’études y ont été consacrées. Avant de considérer la population délinquante, il était important d’évaluer la consommation pornographique dans une perspective développementale auprès d’une population d’adolescents. Nos recherches se sont centrées, d‘une part sur l’impact de l’accessibilité et de la visualisation de ces médias au niveau des représentations de la sexualité et de la pornographie, et d’autre part, sur l’influence de la consommation pornographique au niveau du développement psycho-sexuel et des pratiques sexuelles des adolescents. Une enquête a été menée auprès de 319 jeunes (150 filles) comprenant, en plus des items se rapportant à la sexualité et la pornographie, plusieurs tests évaluant des dimensions du fonctionnement psychologique et social (test de solitude, recherche de sensation, relations aux pairs, délinquance auto-révélée,... ). Des entretiens semi-directifs ainsi que les différents tests ont été proposés à 20 adolescents délinquants judiciarisés. Nos résultats mettent en évidence que la consommation pornographique influence les représentations (et réciproquement) et certains aspects des pratiques sexuelles des jeunes. Il ressort également que les adolescents délinquants (auto-révélés et judiciarisés) apparaissent comme plus vulnérables par rapport aux sollicitations de ces médias. [less ▲]

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See detailEVALUATION OF THE RAPID DETECTION OF ST-17 AND ST-1 GROUP B STREPTOCOCCI USING A MICROFLEX MALDI-TOF MS (BRUKER)
MEEX, Cécile ULg; SACHELI, Rosalie ULg; DESCY, Julie ULg et al

Poster (2014, May)

Objectives Clearly associated to neonatal meningitis, Group B streptococci (GBS) classified as sequence type-17 (ST-17) are defined as the “highly virulent” clone amongst GBS. The aim of this study was to ... [more ▼]

Objectives Clearly associated to neonatal meningitis, Group B streptococci (GBS) classified as sequence type-17 (ST-17) are defined as the “highly virulent” clone amongst GBS. The aim of this study was to evaluate an easy and rapid method, recently described to detect ST-17 and ST-1 GBS, based on distinguishing peak-shifts present on the protein spectrum of these 2 sequence types, using a Microflex (Bruker) matrix-assisted laser desorption/ionization time of flight mass spectrometer (MALDI-TOF MS). Methods This study was performed on 67 multi locus sequence typed (MLST) GBS originated from the Belgian and Czech National Reference Centers, including 18 ST-17 and 16 ST-1. After culture on blood agar, an ethanol/formic acid extraction was performed on each strain. Each extract was spotted once on a target plate, overlaid with 1 µl alpha-cyano-4-hydroxycinnamic acid matrix and further analysed by a Microflex MALDI-TOF MS. One spectrum per isolate was recorded, 240 laser shots being recorded for each spectrum. The spectra were further analysed using a Bruker prototype software, and 2 logarithmic values, one for ST-17 and one for ST-1, calculated from the intensities of the present and absent peaks, were obtained for each strain. If >0, this value indicated the presence of the specific sequence type. In a second step, the test was repeated on each strain with discordant result when compared with MLST. Results Compared with MLST method, the first analysis of the strains gave poor results, leading to very low sensitivities (77.8% for ST-17 and 50% for ST-1) but rather good specificities (85.7% for ST-17 and 98.0% for ST-1). After repeating the analysis on the strains with discordant result, sensitivity, 100% and 93.8%, and specificity, 87.8% and 98.0%, for ST-17 and ST-1 respectively were highly improved. Conclusion Since ST-17 and ST-1 GBS both show distinguishing peak-shifts on their protein spectrum, as described by Lartigue et al., the distinction of these 2 sequence types is now possible by MALDI-TOF MS. To our knowledge, this study is the first describing this application on a Microflex MS using a software to classify the strains. The observed results are promising but, given to the variability of the logarithmic value given by the software, the need to perform several measures on a same strain seems to be essential. After optimization of the analysis procedure, this rapid, easy and cheap method could be used to precociously detect ST-17 among GBS isolated from prenatal screenings, allowing a better follow up of the colonized mothers and a closer monitoring of their newborns. We would like to thank the Bruker Company which allowed us to evaluate the prototype software they have developed. [less ▲]

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See detailWork-home interference and well-being: A cross-lagged analysis.
Babic, Audrey ULg; Stinglhamber, Florence; Barbier, Marie ULg et al

Poster (2014, May)

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See detailEvent justice and social entity justice: A cross-lagged analysis
Marzucco, Laurence ULg; Hansez, Isabelle ULg

Poster (2014, May)

ABSTRACT This study aimed to examine the directionality of the relationship between event justice and social entity justice. Using two samples and a cross-lagged panel analysis with two measurement times ... [more ▼]

ABSTRACT This study aimed to examine the directionality of the relationship between event justice and social entity justice. Using two samples and a cross-lagged panel analysis with two measurement times, social entity justice was found to predict event justice (procedural, distributive, interpersonal and informational justice event), supporting the top-down process. PRESS PARAGRAPH The life of organizations is punctuated by a wide range of managerial decisions (e.g., hiring, performance appraisal or organizational change). Facing such events, employees evaluate the fairness of the situation experienced. However, little is known about how employees develop justice judgments. This study shows that employees’ fairness perceptions about their organization influence their interpretation of the fairness of subsequent events involving the organization. Building and fostering a climate of justice is therefore of primary importance for organizations, since global fairness perceptions about the organization may help employees to perceive a specific event, such as a managerial decision, as being fair. [less ▲]

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See detailPerformances of low-level audio classifiers for large-scale music similarity
Osmalsky, Julien ULg; Van Droogenbroeck, Marc ULg; Embrechts, Jean-Jacques ULg

in International Conference on Systems, Signals and Image Processing (2014, May)

This paper proposes a survey of the performances of binary classifiers based on low-level audio features, for music similarity in large-scale databases. Various low-level descriptors are used individually ... [more ▼]

This paper proposes a survey of the performances of binary classifiers based on low-level audio features, for music similarity in large-scale databases. Various low-level descriptors are used individually and then combined using several fusion schemes in a content-based audio retrieval system. We show the performances of the classifiers in terms of pruning and loss and we demonstrate that some combination schemes achieve a better performance at a minimum computational cost. [less ▲]

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See detailBenfotiamine increases cell proliferation in adult mouse hippocampus
Vignisse, Julie ULg; Caron, Nicolas; Malgrange, Brigitte ULg et al

Poster (2014, May)

Because of the rising prevalence of Alzheimer’s disease (AD), new strategies to slow, halt and prevent the neurodegenerative process are urgently needed. Recently, it has been shown that chronic ... [more ▼]

Because of the rising prevalence of Alzheimer’s disease (AD), new strategies to slow, halt and prevent the neurodegenerative process are urgently needed. Recently, it has been shown that chronic administration of benfotiamine, a thiamine (vitamin B1) - precursor, in a mouse model of AD (APP/PS1 mice) significantly reduced key features of this disease, namely, memory impairment, β-amyloid accumulation and tau hyperphosphorylation [1]. Pyrithiamine, an antimetabolite of thiamine, administered to the same transgenic model has the opposite effects on Alzheimer’s features [2]. However, mechanisms underlying these effects are still unknown. As decreased neurogenesis and consequent cognitive decline have been linked to Alzheimer’s disease [3], we hypothesized that beneficial effects of benfotiamine could be mediated by increased hippocampal neurogenesis. Therefore, we investigated whether benfotiamine (200 mg/kg/day) or thiamine (200 mg/kg/day) orally administered to 3-month old C57BL wild-type mice for 20 days could affect hippocampal neurogenesis. For that purpose, mice were sacrificed 2 h, 24 h and 3 weeks after BrdU injection and immunohistochemistry was performed on brains in order to study cell proliferation, cell cycle exit, neuron survival and integration. Our results show that benfotiamine, but not thiamine treatment, increased both the number of proliferative progenitors (Ki67+ cells) and the number of immature neurons (BrdU+ cells). The difference between thiamine and benfotiamine can be explained by the fact that the latter has a much better bioavailability than thiamine. Indeed, after administration of benfotiamine, blood thiamine concentrations can increase by a factor 100 or more [4]. Further studies will be needed to explain how increased circulating thiamine concentrations can affect neurogenesis. References: 1. Pan X., Gong N., Zhao J., Yu Z., Gu F., Chen J., Sun X., Zhao L., Yu M., Xu Z., Dong W., Qin Y., Fei G., Zhong C., Xu T. L., (2010) Brain 133, 1342-1351. 2. Zhao J., Sun X., Yu Z., Pan X., Gu F., Chen J., Dong W., Zhao L., Zhong C. (2010) Neurotox Res 19, 575-583. 3. Lazarov O. and Marr R.A., (2013) Front. Aging Neurosci. 5, 43. 4. Volvert M.L., Seyen S., Piette M., Evrard B., Gangolf M., Plumier J.C., Bettendorff L. (2008) BMC Pharmacol 8, 10. [less ▲]

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See detailOutplacement adequacy and benefits: The mediating role of retrospective justice
Marzucco, Laurence ULg; Hansez, Isabelle ULg

Poster (2014, May)

ABSTRACT We examined the relationships between perceived outplacement adequacy, retrospective justice and outplacement benefits for redundant employees using outplacement services. Based on an ... [more ▼]

ABSTRACT We examined the relationships between perceived outplacement adequacy, retrospective justice and outplacement benefits for redundant employees using outplacement services. Based on an outplacement experience perceived as adequate, victims formed retrospective justice perceptions about their former organization that in turn, impacted their negative emotions, well-being, future perspectives and job search. PRESS PARAGRAPH The increasing prevalence of organizational downsizing has been matched by growth in the provision of outplacement services over the last decade. Despite this rapid growth and ongoing need for outplacement services, little is yet known about the perceived adequacy and the benefits of these services for redundant employees using them. Our results indicated that an outplacement experience perceived as adequate for redundant employees retrospectively fosters their impressions of justice about the dismissing organization; this leads in turn to satisfactory benefits for them: reduction of negative emotions, enhancement of their perceived well-being, future perspectives, and job-seeking activities. [less ▲]

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See detailEpidemiology of VAP and VAC
LAYIOS, Nathalie ULg; DAMAS, Pierre ULg

Poster (2014, May)

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See detailL'enfant placé au carrefour de ses appartenances
Aubinet, Suzanne ULg

Poster (2014, May)

Michard (2009) nous dit de la loyauté qu’elle est l’armature de l’appartenance et à Neuburger de souligner qu’en plus d’être un socle sur lequel l’identité se structure, l’appartenance contient et limite ... [more ▼]

Michard (2009) nous dit de la loyauté qu’elle est l’armature de l’appartenance et à Neuburger de souligner qu’en plus d’être un socle sur lequel l’identité se structure, l’appartenance contient et limite les effets des relations (2003). Pour Onnis (2008) c’est dans la dialectique entre identité et appartenance que naît l’individualité qui, elle, se réalise dans la relation (Dolto, 1988). Plymackers (2006) insiste sur les notions d’espaces où se nouent ces relations mais aussi de temps où ces dernières se jouent. L’enfant, par des mouvements dialectiques d’allées et venues avec son/ses système(s) d’appartenances tisse pas à pas les prémices de son identité. Ses relations structurent et étayent ce processus et la temporalité constitue le squelette de celui-ci. Mais qu’en est-il de ces enfants placés, maltraités, déplacés ? Qu’en est-il si le conflit ou le clivage de loyauté entre famille(s) et institution(s) rend l’étayage de l’appartenance ardu ? Qu’en est-il si la discontinuité des espaces et des relations prédomine et si le processus d’individuation est suspendu par une séparation arbitraire dictée par un autrui qui « n’appartient pas » ? L’analyse clinique de cas d’enfants aux vécus chaotiques rythmés par de nombreux placements nous permet de décortiquer les particularités de ce processus complexifié par ces ruptures d’espaces, ces loyautés morcelées, ces appartenances diffuses et d’en cerner les impacts. [less ▲]

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See detailOne-year follow-up of platelet-rich plasma to treat chronic upper patellar tendinopathies
Kaux, Jean-François ULg; Croisier, Jean-Louis ULg; Bruyère, Olivier ULg et al

in European Journal of Physical and Rehabilitation Medicine (2014, May), 50(Suppl. 1 to No. 3), 227250-

Introduction: Infiltration of PRP may be used as a recent therapeutic option for chronic tendinopathies The aim of the current study is to evaluate the clinic and the return to sports activities in ... [more ▼]

Introduction: Infiltration of PRP may be used as a recent therapeutic option for chronic tendinopathies The aim of the current study is to evaluate the clinic and the return to sports activities in patients with chronic upper patellar tendinopathies 1 year after 1 infiltration of PRP. Material and methods: The follow-up of 20 subjects who beneficed from 1 infiltration of PRP was made before infiltration, after 3 months and 1 year after infiltration; it was made as follow: VAS, IKDC and VISA-P scores. Moreover, they had to answer an information questionnaire concerning their life and sports activities. Results: Seventy percents of patients reported a favourable evolution with decrease of pain, 10% did never report any improvement and 20% were treated surgically. Eighty-seven percents returned to sports activities without any pain, and 50% of them recovered the same sport level. VAS has significantly (p<0.0001) dropped, IKDC significantly improved (p=0.0007) and VISA-P also significantly increased (p=0.0087) over the follow-up of 1 year. Discussion: This study confirms that a local injection of PRP coupled with a program of eccentric rehabilitation through a chronic Jumper's knee, improves painful symptoms and the functionality of the subjects’ knee up to a follow-up of 1 year. [less ▲]

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See detailTest equipments for characterizing the behavior of materials, bearings and dynamic seals in cryogenic fluid environments
Bozet, Jean-Luc ULg; Servais, Christophe ULg; Duquenne, Marc ULg et al

in Space Propulsion 2014 (2014, May)

Test rigs available at the cryogenic test site of the University of Liège concern quite delicate high rotational speed components of cryogenic rocket engines. That is to say bearings and dynamic seals ... [more ▼]

Test rigs available at the cryogenic test site of the University of Liège concern quite delicate high rotational speed components of cryogenic rocket engines. That is to say bearings and dynamic seals. These rigs gave successfully important results for the understanding and the improvement of the running of the so called components. Until now the test zone is equipped for handling liquid oxygen and liquid nitrogen. [less ▲]

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See detailApprentissage par renforcement bayésien versus recherche directe de politique hors-ligne en utilisant une distribution a priori: comparaison empirique
Castronovo, Michaël ULg; Ernst, Damien ULg; Fonteneau, Raphaël ULg

in Proceedings des 9èmes Journée Francophones de Planification, Décision et Apprentissage (2014, May)

Cet article aborde le problème de prise de décision séquentielle dans des processus de déci- sion de Markov (MDPs) finis et inconnus. L’absence de connaissance sur le MDP est modélisée sous la forme ... [more ▼]

Cet article aborde le problème de prise de décision séquentielle dans des processus de déci- sion de Markov (MDPs) finis et inconnus. L’absence de connaissance sur le MDP est modélisée sous la forme d’une distribution de probabilité sur un ensemble de MDPs candidats connue a priori. Le cri- tère de performance utilisé est l’espérance de la somme des récompenses actualisées sur une trajectoire infinie. En parallèle du critère d’optimalité, les contraintes liées au temps de calcul sont formalisées rigoureusement. Tout d’abord, une phase « hors-ligne » précédant l’interaction avec le MDP inconnu offre à l’agent la possibilité d’exploiter la distribution a priori pendant un temps limité. Ensuite, durant la phase d’interaction avec le MDP, à chaque pas de temps, l’agent doit prendre une décision dans un laps de temps contraint déterminé. Dans ce contexte, nous comparons deux stratégies de prise de déci- sion : OPPS, une approche récente exploitant essentiellement la phase hors-ligne pour sélectionner une politique dans un ensemble de politiques candidates et BAMCP, une approche récente de planification en-ligne bayésienne. Nous comparons empiriquement ces approches dans un contexte bayésien, en ce sens que nous évaluons leurs performances sur un large ensemble de problèmes tirés selon une distribution de test. A notre connaissance, il s’agit des premiers tests expérimentaux de ce type en apprentissage par renforcement. Nous étudions plusieurs cas de figure en considérant diverses distributions pouvant être utilisées aussi bien en tant que distribution a priori qu’en tant que distribution de test. Les résultats obtenus suggèrent qu’exploiter une distribution a priori durant une phase d’optimisation hors-ligne est un avantage non- négligeable pour des distributions a priori précises et/ou contraintes à de petits budgets temps en-ligne. [less ▲]

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See detail25KDa-Thiamine triphosphatase is essential for spermatozoid development in mice
Kohn, Grégory ULg; Ectors, Fabien ULg; Lakaye, Bernard ULg et al

Poster (2014, May)

For many years, our laboratory has been interested in thiamine triphosphate (ThTP), a vitamin B1 derivative whose metabolism and physiological role remain unclear. Regarding its production, we have shown ... [more ▼]

For many years, our laboratory has been interested in thiamine triphosphate (ThTP), a vitamin B1 derivative whose metabolism and physiological role remain unclear. Regarding its production, we have shown that in E. coli and in rat brain mitochondria, ThTP is synthesized from thiamine diphosphate and inorganic phosphate through a chemiosmotic mechanism involving the FoF1- ATP synthase [1, 2]. In mammalian cells, its concentration is maintained at a low level through hydrolysis by a very specific cytosolic 25-kDa thiamine triphosphatase (ThTPase) [3]. In order to gain insight in the role of ThTP and ThTPase in mammalian tissues, we decided to generate a mouse strain invalidated in 25kDa-ThTPase with the hope that these mice will accumulate ThTP in their tissues. We obtained genetically modified embryonic stem (ES) cells from the Knockout Mouse Project (KOMP) repository. In those cells, one of the 25kDa-ThTPase alleles was replaced by a construction containing the lacZ and the neomycin resistance genes. Those ES cells were microinjected in blastocysts and the chimeric blastocysts were injected in a mouse uterus to generate chimerae. However, when we bred those mice with wild type mice, the construction was never transmitted to the pups. To explain this result, we selected those chimerae that presented a sex-reversal. In those mice, all the spermatozoids derive from the injected embryonic stem cells, so that half of the spermatozoids are expected to harbor the construction. However, after qPCR analysis, we observed that the spermatozoids with the construction were outnumbered by a factor of thousand. These results strongly suggest that the 25kDa-ThTPase is required for spermatozoid development. 1. Gangolf, M., Wins, P., Thiry, M., El Moualij, B. & Bettendorff, L. (2010) J. Biol. Chem. 285, 583-94. 2. Gigliobianco, T., Gangolf, M., Lakaye, B., Pirson, B., von Ballmoos, C., Wins, P. & Bettendorff, L. (2013) Scientific reports. 3, 1071. 3. Lakaye, B., Makarchikov, A. F., Antunes, A. F., Zorzi, W., Coumans, B., De Pauw, E., Wins, P., Grisar, T. & Bettendorff, L. (2002) J. Biol. Chem. 277, 13771-7. [less ▲]

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See detail« La flexicurité : une politique des idées ? Regards croisés d’acteurs institutionnels belges en 2013 »
Beuker, Laura ULg; Gérard, Julie ULg; Orianne, Jean-François ULg

Conference (2014, May)

Cette communication porte sur la traduction, en Belgique, d’une politique européenne de l’emploi – la flexicurité – par différents acteurs institutionnels. À partir d’une analyse documentaire et d’une ... [more ▼]

Cette communication porte sur la traduction, en Belgique, d’une politique européenne de l’emploi – la flexicurité – par différents acteurs institutionnels. À partir d’une analyse documentaire et d’une vingtaine d’entretiens semi-directifs, nous étudierons la manière dont ces acteurs s’approprient et interprètent la flexicurité. Nous nous appuierons principalement sur les apports récents de la sociologie de l’action publique, en particulier l’approche cognitive des politiques publiques (Surel, 2000 ; Muller et Surel, 1998) et l’européanisation des politiques d’emploi (Palier et Surel, 2007 ; 2010). Nous montrerons que cette appropriation a donné lieu, en Belgique, à une transformation de sens conféré à la sécurité, celle-ci étant dorénavant substitué à celui de la flexibilité. [less ▲]

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See detailEulerian Formulation of the Torque and Drag Problem
Huynen, Alexandre ULg; Detournay, Emmanuel; Denoël, Vincent ULg

in Detournay, Emmanuel; Denoël, Vincent; van de Wouw, Nathan (Eds.) Third International Colloquium on Nonlinear Dynamics and Control of Deep Drilling Systems (2014, May)

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See detailDioxins and PCBs in eel and Chinese mitten crabs in the Rhine-Meuse estuary
van Hattum, B; Nijssen, P; Focant, Jean-François ULg et al

Poster (2014, May)

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See detailEviter la tour d'ivoire, éviter les allées du pouvoir
Jacquemain, Marc ULg

in Delchambre, Jean-Pierre (Ed.) Le sociologue comme médiateur ? Accords, désaccords et malentendus (2014, May)

L'article s'interroge sur la nature de l'expertise en sciences sociales. En partant de la définition de l'expertise en général par Philippe Roqueplo, on défend que la sociologie ne peut prétendre à une ... [more ▼]

L'article s'interroge sur la nature de l'expertise en sciences sociales. En partant de la définition de l'expertise en général par Philippe Roqueplo, on défend que la sociologie ne peut prétendre à une connaissance scientifique que dans le cadre des questions qu'elle pose elle-même en tant que discipline. Cela ne la dispense pas de répondre aux questions que se pose la société et, en particulier, les pouvoirs publics, mais les réponses n'ont pas le statut de réponses scientifiques. [less ▲]

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See detailSeeking for causes of recent methane increase: comparison between GEOS-Chem tagged simulations and FTIR column measurements above Jungfraujoch
Bader, Whitney ULg; Bovy, Benoît ULg; Wecht, K et al

Poster (2014, May)

Atmospheric CH4 reached 260% of the pre-industrial level (~700 ppb) due to increased emissions from anthropogenic sources. Globally averaged CH4 reached a new high of 1819 ± 1 ppb in 2012, an increase of ... [more ▼]

Atmospheric CH4 reached 260% of the pre-industrial level (~700 ppb) due to increased emissions from anthropogenic sources. Globally averaged CH4 reached a new high of 1819 ± 1 ppb in 2012, an increase of 6 ppb with respect to the previous year (WMO, Greenhouse gas Bulletin N.9, 2013). CH4 above Jungfraujoch increases at 0.53±0.19%/year during the late 90s to stabilize and reach a non significant trend from 2000 to 2005. Since 2006, atmospheric methane has been continuously increasing with a rate of 0.19±0.05 %/year. The attribution of this increase to any CH4 source is difficult since the current network is insufficient to characterize emissions by region and source process, emphasizing the need for source-tagged model simulations as it should provide us information on processes causing the increase of atmospheric methane since 2005/2006. [less ▲]

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See detailThree North American Mystery Tales
Dechêne, Antoine ULg

Conference (2014, May)

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See detailLe redoublement scolaire rend-il les élèves plus agressifs? Etude quasi-expérimentale sur le redoublement scolaire en début de secondaire et ses conséquences sur l’agressivité
Mathys, Cécile ULg; Véronneau, Marie-Hélène; Lecocq, Aurélie

Conference (2014, May)

Le taux de redoublement scolaire est particulièrement élevé en Belgique. Bien que ses effets concernant les performances académiques soient régulièrement étudiés, les conséquences du redoublement scolaire ... [more ▼]

Le taux de redoublement scolaire est particulièrement élevé en Belgique. Bien que ses effets concernant les performances académiques soient régulièrement étudiés, les conséquences du redoublement scolaire sur l’adaptation psychosociale des élèves fait encore peu l’objet de recherches rigoureuses, notamment concernant le niveau d’agressivité des élèves qui ont vécu un redoublement. Par ailleurs, l’entrée en enseignement secondaire coïncide avec l’affirmation de nouveaux statuts sociaux pour les élèves et l’agressivité peut être une façon d’établir une hiérarchie au sein des groupes de pairs. L’objectif de cette étude est d’examiner si le redoublement scolaire affecte à court terme le niveau d’agressivité d’élèves se situant au début de leur cursus d’enseignement secondaire. Un protocole quasi-expérimental a été utilisé et deux groupes d’élèves comparables (doublants et promus) ont pu être crées grâce à des scores de propension sur base de 26 variables collectées. Des mesures auto-rapportées et standardisées ont été administrées sur deux semestres et un échantillon de 72 élèves provenant d’un établissement secondaire typique de la Fédération Wallonie-Bruxelles (moy. âge = 12.9 ans, 47.2% de filles, 70% d’origine belge) a été identifié. Des analyses univariées réalisées par SPSS (F (1,67) = 6,98, p = 0,01) révèlent que durant l’année suivant le redoublement scolaire, les élèves ayant doublé ne montrent pas de diminution de leur niveau d’agressivité (t (35) = 0,50, ns), contrairement aux élèves ayant été promus (t (32) = 3,32, p = 0,01). En outre, ces résultats sont significativement « palpables » comme l’indique la taille de l’effet plutôt élevée (d = .64). Ces résultats sont discutés en termes d’implications, notamment concernant l’importance de continuer à maintenir un statut social pour les élèves ayant vécu une expérience de redoublement au début de leur cursus en enseignement secondaire, contrairement aux élèves qui ont été promus. [less ▲]

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See detailRetrieval of HCHO from MAX-DOAS measurements at the high-altitude alpine station of Jungfraujoch (46.5°N, 8.0°E)
Hendrick, François; Fayt, Caroline; Franco, Bruno ULg et al

Conference (2014, April 30)

Formaldehyde (HCHO) plays an important intermediate role in the atmospheric photo-oxidation pathways. It is produced during the oxidation of methane and many non-methane volatile organic compounds (NMVOCs ... [more ▼]

Formaldehyde (HCHO) plays an important intermediate role in the atmospheric photo-oxidation pathways. It is produced during the oxidation of methane and many non-methane volatile organic compounds (NMVOCs) which participate to the formation of tropospheric ozone and secondary organic aerosols. HCHO is also directly released by biomass burning and fossil fuel combustion and to a lesser extent by vegetation. Measuring this species is therefore of major importance for air quality and climate change monitoring. In this presentation, HCHO near-surface concentrations and vertical column densities are retrieved from MAX-DOAS measurements performed at the high-altitude station of Jungfraujoch (3580m asl) in the Swiss Alps from July 2010 till December 2012. Although being most of the time located in the free troposphere, this station can be temporarily affected by pollution events originating from the valley, leading to a local increase of air pollutant concentrations. The capability of the MAX-DOAS technique to retrieve HCHO in such high-altitude location is investigated. The spatial representativeness and the impact of cloud cover on the measurements is also discussed. For verification purpose, our retrievals are compared to collocated FTIR observations, taking into account the difference in vertical resolution between both techniques. Simulations from the 3D-CTM IMAGES are also used to further assess the observed seasonal and diurnal cycles of HCHO surface concentration and vertical column. [less ▲]

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See detailRecords of human activity during the late-Holocene in the soils of the African dense humid forest
Morin-Rivat, Julie ULg; Biwolé, Achille; Bourland, Nils ULg et al

Conference (2014, April 30)

Recently, several authors gathered data about the presence of past human populations in tropical regions covered by dense forest nowadays. In central Africa, there is a growing body of evidence for past ... [more ▼]

Recently, several authors gathered data about the presence of past human populations in tropical regions covered by dense forest nowadays. In central Africa, there is a growing body of evidence for past human settlements along the Atlantic coast, but very little information is available further inland. In this perspective, soil records seem to be the most appropriated so as to appraise the spatial and temporal extent of human activity in the African dense humid forest. In this paper, we thus aimed to present a synthesis of the archaeological and archaeobotanical data obtained during several fieldwork campaigns in an archaeologically unexplored area of 200,000 km² located in southern Cameroon and the northern Republic of Congo. A total of 275 test pits, among them 30 pedological pits up to 150 cm deep, were excavated in the study area. So as to get a long temporal scale as well as a fine resolution spatial scale, we quantified wood charcoal and charred endocarps in soil samples by layers of 10 cm taken for 100 pits located along transects of systematic sampling. Spatial projections were performed using statistics together with multivariate analyses. AMS radiocarbon dating allowed interpreting the temporal framework. Evidence of past human activities through either artifacts or charred botanical remains was observed in all pits, in particular with the ubiquitous presence of charcoal at each site. Main charcoal peaks were interpreted as fields (slash-and-burn agriculture) in the vicinity of ancient villages, the later marked by the presence of both potsherds and oil palm endocarps. The dichotomy of these kinds of activities may have impacted differentially the environment during the past. The set of 73 radiocarbon dates extending from 15,000 BP to the present time provided more dates in the late-Holocene showing a bimodal distribution which was interpreted as two phases of human expansion with an intermediate phase of population crash. The 2300–1300 BP phase is correlated with the migrations of supposed farming populations from northwestern Cameroon. Between 1300 and 670 BP, less material could be dated. Following that population collapse, the 670–20 BP phase corresponds to a new period of human expansion known as the Late Iron Age. The dates obtained support the established chronology reported for whole central Africa. This study underlines the necessity of fieldwork efforts and of the usefulness of archives sealed in soil records so as to bring new, extensive and precise evidence of human activities in the Congo Basin. [less ▲]

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See detailA new analysis of the optical polarisation alignments of quasars
Pelgrims, Vincent ULg

Poster (2014, April 30)

Introduction of a new statistical method dedicated to the analysis of polarisation orientations and presentation of some results of its application to the sample of optical polarisation measurements of ... [more ▼]

Introduction of a new statistical method dedicated to the analysis of polarisation orientations and presentation of some results of its application to the sample of optical polarisation measurements of 355 quasars. [less ▲]

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See detailTRAPPIST detection of the light from a bloated hot Jupiter at the edge of tidal disruption
Delrez, Laetitia ULg; Gillon, Michaël ULg; Lendl, Monika ULg et al

Poster (2014, April 30)

Abstract : We present here the discovery by the WASP-­South survey, in close collaboration with the Euler and TRAPPIST telescopes, of the transiting planet WASP-­121b as well as the measurement of its ... [more ▼]

Abstract : We present here the discovery by the WASP-­South survey, in close collaboration with the Euler and TRAPPIST telescopes, of the transiting planet WASP-­121b as well as the measurement of its thermal emission at 0.9 microns. WASP-­121b is a very inflated (1.76 RJup) Jupiter-­mass (1.02 MJup) planet that transits every 1.27 days a bright F6V star. It is remarkable as its orbital radius is only ~10% larger than its Roche limit, suggesting that it might experience mass loss through Roche-­lobe overflow. Thanks to its large size and extreme irradiation (~7 10^9 erg s-1 cm-­2), it was predicted to display a thermal emission of ~0.1% of the stellar flux in the near-­infrared. Using the TRAPPIST robotic telescope, we could detect this thermal emission signal at ~5 sigma in the z'-­band. This measurement, a first for a ground-­based 60cm telescope, allows to place preliminary constraints on the atmospheric properties of this very special hot Jupiter. [less ▲]

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Peer Reviewed
See detailSpatio-Temporal Analysis of Equatorial Ionospheric Scintillations in the Frame of Absolute GNSS Positioning Algorithms
Lonchay, Matthieu ULg; Cornet, Yves ULg; Aquino, Marcio et al

Conference (2014, April 30)

The ionosphere has always been a major limitation for GNSS positioning applications. Free electrons in the ionosphere perturb the propagation of GNSS radio signals involving both refraction and ... [more ▼]

The ionosphere has always been a major limitation for GNSS positioning applications. Free electrons in the ionosphere perturb the propagation of GNSS radio signals involving both refraction and diffraction effects. The ionospheric refraction mainly results in a modification of the propagation speed of the GNSS electromagnetic signals, inducing an error (propagation delay or phase advance depending on the observable) in GNSS measurements. In the frame of absolute positioning techniques, single-frequency algorithms usually exploit an ionospheric model to mitigate the ionospheric error while dual-frequency algorithms, such as the well-known Precise Point Positioning (PPP), take the benefit of the availability of two frequencies and the fact that the ionosphere is a dispersive medium to construct an ionosphere-free mathematical model. But these two strategies are not able to counteract the effect of the ionospheric diffraction which is due to small-scale irregularities in the free electron density. By scattering GNSS signals, these irregularities generate rapid fluctuations (scintillations) in the amplitude and phase of GNSS signals with critical consequences for GNSS applications: cycle slips, signal power fading, receiver loss of lock and poor resulting satellite geometry. The goal of our research is to develop a strategy to mitigate the effect of ionospheric scintillations on absolute GNSS positioning techniques, in particular the SPP (Standard Point Positioning) and the PPP (Precise Point Positioning). The strategy is based on the adjustment of the stochastic model. In order to construct the stochastic model (diagonal and non-diagonal elements) and study the correlation between observables, we adopted a “spatial” and an “empirical” approach. The spatial approach consists in a study of the spatial autocorrelation existing in scintillations effects on GNSS signals. The spatial autocorrelation is detected by using specific spatial analysis techniques applied on data from a network of ISMR (Ionospheric Scintillation Monitoring Receiver) stations located at equatorial and polar latitudes, where scintillations effects are most severe. The knowledge of how scintillation effects are spatially correlated is helpful for determining a coherent stochastic model. The empirical approach does not take into account the phenomenon spatiality and the locations of the measurements but only the observation data. Its objective is to determine the statistical correlation which exists between GNSS measurements during a scintillation event by using a moving filter applied on GNSS observation and scintillation data. The spatial approach exploits data and data locations while the empirical approach is based only the data itself. [less ▲]

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See detailQuasi-periodic flares in Jupiter's aurora : new results
Bonfond, Bertrand ULg; Grodent, Denis ULg; Badman, Sarah et al

Conference (2014, April 29)

Two recent Hubble Space Telescope observation campaigns have been dedicated to the Jovian Far-UV aurora (GO 12883 – PI: D. Grodent and GO 13035 – PI: S. Badman). Both of them made use of the Time-Tag mode ... [more ▼]

Two recent Hubble Space Telescope observation campaigns have been dedicated to the Jovian Far-UV aurora (GO 12883 – PI: D. Grodent and GO 13035 – PI: S. Badman). Both of them made use of the Time-Tag mode of the Space Telescope Imaging Spectrograph (STIS), a high time resolution mode which allows to observe temporal variations on timescales of tens of seconds. In the present study, we focus on sudden and spectacular bursts of auroral emissions taking place in the active region located poleward of the main emissions and called “flares”. A previous study, based on only two image sequences acquired with rather unfavorable viewing angles, showed that these flares could reappear quasi-periodically on time scales of 2-3 minutes. Phenomena with similar timescales have been identified by in-situ spacecraft in relativistic electron and radio data as well as in reconnection signatures, for example. But the physical mechanism behind these ubiquitous signatures remains to be unveiled. Here we make use of the most recent and much larger data set to study in further details the occurrence rate, the period, the location, the extent and the motion of these quasi-periodic flares and to compare their behavior in both hemispheres. Quantifying these parameters allows us to narrow down the possibilities among likely explanations and provide a tentative scenario for these short timescale quasi-periodic features. [less ▲]

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See detailVadose zone studies at an industrial contaminated site: the vadose zone monitoring system and cross-hole geophysics
Fernandez de Vera, Natalia ULg; Beaujean, Jean ULg; Jamin, Pierre ULg et al

Poster (2014, April 29)

Poster presented at the European Geoscience Union General Assembly 2014. In this poster, the installation of the vadose zone experimental set up is presented along with first results

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See detailTowards deep changes for a more resilient farming system: Examining roles farmers, science and citizens can play in transition
Klaedtke, Stephanie ULg

Conference (2014, April 29)

This lecture considers the complexity of challenges of the agricultural transition from the perspective of farmers, who act at the intersection between the ecology, economy and policy. The lecture will ... [more ▼]

This lecture considers the complexity of challenges of the agricultural transition from the perspective of farmers, who act at the intersection between the ecology, economy and policy. The lecture will start by providing an overview on the resource requirements for our global production chains of life stock and meat, grain and legume farming and say some words on the human diet, and food and feed conversion efficiency of energy-intake through food. This lecture also places a fresh emphasis on the development of local knowledge and locally specific arming and nutrition practices that are adapted to local environments, as a necessary complement to agricultural science striving to make universal claims. This leads on to basic insights on needs for knowledge production in agriculture, and merits and limitations of action research and engaged research, raising questions on how farmers, scientists and citizens might better collaborate to inform choices in food production and consumption. For the future there are some indications on a new trend on new more decentralised governance of the food system including citizen’s involvement in French organic certification and Community based Auditing and citizens science in communities in Australia to work with farmers on reducing environmental impacts and address ensuing trade-offs for farmers as a community. [less ▲]

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See detailDynamique des forêts irrégulières et mélangées: de la modélisation aux recommandations sylvicoles
Ligot, Gauthier ULg

Conference (2014, April 29)

Close-to-nature management of forests has been increasingly advocated and practiced. However forest managers often face difficulties in maintaining the mixture of species with different shade tolerance ... [more ▼]

Close-to-nature management of forests has been increasingly advocated and practiced. However forest managers often face difficulties in maintaining the mixture of species with different shade tolerance. We studied this issue in uneven-aged acidophile medio-European beech forests. In these forests, while forest management has achieved regular timber production, it has rarely succeeded in promoting a diversified natural regeneration. In view of this, our objective is to refine our knowledge about the dynamic of uneven-aged mixed forests using a modelling approach. A set of consistent models were carried out to describe stand dynamic with, in particular, models of regeneration growth and light interception. The models were then implemented in a simulator in order to perform prospective analysis. In contrast to expectations, we found that saplings of beech, the shade-tolerant species, had the highest height growth rate at all light levels. Beech saplings reached an optimum growth at transmittance of 10%, whereas oak saplings needed more than 20%. These results indicate that oak saplings are systematically outcompeted by beech saplings across the light gradient. Thus, the control of canopy opening is not sufficient to promote the natural regeneration of oak beneath a stand also containing beech. Taking into account these latter results, we compared cutting strategies varying in type and intensity. Creating gaps of about 500 m² provided adequate light for small regeneration clumps. Cutting from below, species-specific cutting and uniform cutting were also appropriate but uniform cutting required higher harvest intensity. Cutting from above weakly increased understory light and promoted rather shade tolerant species. Finally we provided indications on different strategies that promote the regeneration of less-shade tolerant species, depending on the spatial aggregation of saplings, and the desired post-harvest stand structure and composition. [less ▲]

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See detailLD-based haplotype encoding scheme with iterative pruning principal component analysis (ipPCA) to retrieve population substructures
Chaichoompu, Kridsadakorn ULg; Fouladi, Ramouna ULg; Wangkumhang, Pongsakorn et al

Poster (2014, April 29)

Objective To identify and differentiate between subpopulations using a rich set of genetic markers, as using reduced sets of genetic markers for these purposes can become challenging, especially when ... [more ▼]

Objective To identify and differentiate between subpopulations using a rich set of genetic markers, as using reduced sets of genetic markers for these purposes can become challenging, especially when similar geographic regions are involved or when spurious patterns are likely to exist. Method Single Nucleotide Polymorphisms (SNPs) are commonly used to capture variations between populations and often genome-wide SNP data are pruned based on linkage disequilibrium (LD) patterns. Notably, haplotype composition and the pattern of LD between markers may vary between larger populations but may also play a role within more confined geographic regions. Indeed, knowledge about haplotypes in unrelated individuals can reveal useful information about genetic ancestry. Here, we use iterative pruning principal component analysis (ipPCA) [1] to identify and characterize subpopulations in an unsupervised way. As input data, either pruned genome-wide SNP data are used (using PLINK 1.9 with the "indep-pairwise" option, window size = 100k, r2 < 0.25) or multilocus haplotype information derived from the genome-wide SNP panel (using BEAGLE 3.3.2 to infer haplotype). These approaches are applied to real-life data from 992 Thai individuals [2]. Result Preliminary results indicate that ipPCA applied to pruned SNP data or ipPCA that explicitly uses multilocus information (haplotypes) give complementary information about population substructure for geographically confined populations such as the Thai samples in this study. Both methods address different aspects of population structure. Detailed simulation studies are needed to identify the optimal scenarios for haplotype-based ipPCA. Conclusion In this work, we propose to combine an LD-based haplotype encoding scheme with the ipPCA machinery to retrieve fine population substructures. Despite the complexities that are associated with haplotype inference, added value can be obtained when the LD structure between SNPs is exploited in the search for relevant population strata. References 1. Intarapanich, A., et al., Iterative pruning PCA improves resolution of highly structured populations. BMC Bioinformatics, 2009. 10: p. 382. 2. Wangkumhang, P., et al., Insight into the peopling of Mainland Southeast Asia from Thai population genetic structure. PLoS One, 2013. 8(11): p. e79522. [less ▲]

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See detailIntermediaries, transport costs and interlinked transaction
Tharakan, Joseph ULg

Conference (2014, April 29)

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Peer Reviewed
See detailDecoding implicit information from the soil map of Belgium and implications for spatial modelling and soil classification
Dondeyne, Stefaan; Legrain, Xavier ULg; Colinet, Gilles ULg et al

Conference (2014, April 29)

A systematic soil survey of Belgium was conducted from 1948 to 1991. Field surveys were done at the detailed scale of 1:5000 with the final maps published at a 1:20,000 scale. Soil surveyors were ... [more ▼]

A systematic soil survey of Belgium was conducted from 1948 to 1991. Field surveys were done at the detailed scale of 1:5000 with the final maps published at a 1:20,000 scale. Soil surveyors were classifying soils in the field according to physical and morphogenetic characteristics such as texture, drainage class and profile development. Mapping units are defined as a combination of these characteristics but to which modifiers can be added such as parent material, stoniness or depth to substrata. Interpretation of the map towards predicting soil properties seems straight forward. Consequently, since the soil map has been digitized, it has been used for e.g. hydrological modelling or for estimating soil organic carbon content at sub-national and national level. Besides the explicit information provided by the legend, a wealth of implicit information is embedded in the map. Based on three cases, we illustrate that by decoding this information, properties pertaining to soil drainage or soil organic carbon content can be assessed more accurately. First, the presence/absence of fragipans affects the soil hydraulic conductivity. Although a dedicated symbol exits for fragipans (suffix “...m”), it is only used explicitly in areas where fragipans are not all that common. In the Belgian Ardennes, where fragipans are common, their occurrence is implicitly implied for various soil types mentioned in explanatory booklets. Second, whenever seasonal or permanent perched water tables were observed, these were indicated by drainage class “.h.” or “.i.”, respectively. Stagnic properties have been under reported as typical stagnic mottling – i.e. when the surface of soil peds are lighter and/or paler than the more reddish interior – were not distinguished from mottling due to groundwater gley. Still, by combining information on topography and the occurrence of substratum layers, stagnic properties can be inferred. Thirdly, soils with deep anthropogenic enriched organic matter (Anthrosols) are distinguished for their specific profile development (code “..m”). Obviously, when assessing soil organic carbon content these soil types need particular consideration. Soils in the Campine region with anthropogenic layers only 30 to 40 cm thick, not being Anthrosols, got a specific suffix code (“. . . 3”). Still, as these soils may have a buried Ah horizon of up to 20 cm, their soil organic carbon content can be comparable to those of Anthrosols. The buried Ah horizon is however not explicitly mapped; its presence needs to be inferred from other environmental information. In conclusion, conventional soil maps convey more information than what transpires from just the explicit legend’s semantics. Although a challenge, decoding the implicit information should be particularly useful for spatial modeling. The cases also point to the importance of classifying soil characteristics explicitly, wherever possible, and in particularly when soil maps are integrated into geographical information systems. [less ▲]

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See detailApplication of multi-scale variography for inferring the spatial variability of the hydraulic conductivity of a sandy aquifer
Rogiers, Bart; Vienken, Thomas; Gedeon, M et al

Poster (2014, April 28)

In the framework of the disposal of short-lived low- and intermediate-level radioactive waste in a near-surface disposal facility in Dessel (Belgium), extensive characterization of the hydraulic ... [more ▼]

In the framework of the disposal of short-lived low- and intermediate-level radioactive waste in a near-surface disposal facility in Dessel (Belgium), extensive characterization of the hydraulic conductivity (K) in the shallow Neogene aquifer has been performed at a regional scale. In the last few years the small-scale heterogeneity has been additionally characterized by outcrop analogue, hydraulic direct push, and borehole core air permeameter studies. The gathered data now include a) more than 350 hydraulic conductivity measurements on samples from 8 cored boreholes, mostly reaching depths of 50 m and data at 2 m intervals, b) more than 5000 air permeability measurements on the same borehole cores, c) more than 250 cone penetration tests (CPTs) with depths down to 40 m and data at 2 cm intervals, d) over 100 dissipation tests performed during the CPT campaigns, e) 17 direct push injections loggings, 6 hydraulic profiling tool logs, and 6 direct push slug tests, f) several hundreds of air permeability measurements on outcrop analogues of the aquifer sediments, and g) numerous grain size analyses. The current study aims to quantify the heterogeneity of K from the centimetre- to the kilometre-scale and to check the compatibility of the spatial variability revealed by the different datasets. This is achieved through gathering all K values (either direct measurements, calibrated relative K values, or K estimates from secondary data), and the use of variography to quantify spatial variability in terms of two-points geostatistics. The results are discussed, and the main differences between the different data sources are explained. In a final step, different multi-scale variogram models are proposed for capturing the main characteristics of multi-scale variability within the shallow Neogene aquifer in Belgium. [less ▲]

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Peer Reviewed
See detailContribution of a new active faults map and sedimentary cores to the characterization of seismogenic sources in an interdisciplinary approach (Western Gulf of Corinth, Greece)
Beckers, Arnaud ULg; Hubert, Aurelia ULg; Beck, Christian et al

Conference (2014, April 28)

The Corinth rift is one of the fastest spreading rifts on Earth. 5 earthquakes of magnitude greater than 5.8 occurred during the last 40 years. The question of seismic hazard is consequently particularly ... [more ▼]

The Corinth rift is one of the fastest spreading rifts on Earth. 5 earthquakes of magnitude greater than 5.8 occurred during the last 40 years. The question of seismic hazard is consequently particularly relevant. Despite a long earthquake catalogue, estimations of earthquake hazard remain problematic because of the difficulty to associate each historical event to one of the many active faults mapped in the area. Consequently, combining seismology, history and paleoseismology in an interdisciplinary approach is here necessary and is the goal of the ANR-SISCOR project. In this framework, we investigated the offshore sediments in order to (1) better constraint the length of the active offshore faults, and (2) look for sedimentary signature of historical earthquakes. 600 km of high resolution seismic reflexion data have been acquired during two surveys and 12 short gravity cores have been retrieved. The latters are 0.5 to 1 m long, allowing us to analyze about 500 yrs of sedimentation. Two new faults potentially able to trigger M>5.5 earthquakes have been mapped in the northern part of the gulf based on seismic data. Sedimentary events (turbidites and mud flows) have been identified in some cores, essentially in the deep basin and in a 180m-deep sub-basin close to the northern coast. The comparison with the critically reviewed historical records shows that some of these events could have been triggered by historical earthquakes. The link between these potential earthquakes sedimentary signatures, historical events and active faults is discussed based on intensity maps and our new active fault map. [less ▲]

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See detailThermal tracer tests for characterizing a shallow alluvial aquifer
Wildemeersch, Samuel ULg; Klepikova, Maria ULg; Jamin, Pierre ULg et al

in Geophysical Research Abstracts (2014, April 28)

Using heat as an active tracer in different types of aquifers is a topic of increasing interest [e.g. Vandenbohede et al.; 2008, Wagner et al., 2013; Read et al., 2013]. In this study, we investigate the ... [more ▼]

Using heat as an active tracer in different types of aquifers is a topic of increasing interest [e.g. Vandenbohede et al.; 2008, Wagner et al., 2013; Read et al., 2013]. In this study, we investigate the potential interest of coupling heat and solute tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in nine monitoring wells located according to three transects with regards to the main groundwater flow direction. The breakthrough curves measured in the recovery well showed that heat transfer in the alluvial aquifer is slower and more dispersive than solute transport. Recovery is very low for heat while in the same time it is measured as relatively high for the solute tracer. This is due to the fact that heat diffusion is larger than molecular diffusion, implying that exchange between groundwater and the porous medium matrix is far more significant for heat than for solute tracers. Temperature and concentrations in the recovery well are then used for estimating the specific heat capacity with the energy balance approach and the estimated value is found to be consistent with those found in the literature. Temperature breakthrough curves in other piezometers are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. By means of a numerical heat transport model, we provide a preliminary interpretation of these temperature breakthrough curves. Furthermore, these data could be included in the calibration of a complex heat transfer model for estimating the entire set of heat transfer parameters and their spatial distribution by inverse modeling. [less ▲]

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See detailCharcoal records reveal past occurrences of perturbations in the forests of the Kisangani region(RDC): vegetation history of the semi-deciduous rainforest
Tshibamba Mukendi, John; Hubau, Wannes; Morin-Rivat, Julie ULg et al

Poster (2014, April 28)

Introduction. Past disturbances have modified the structure and the floristic composition of Central African rainforests. These perturbations represent a driving force for forest dynamics and they are ... [more ▼]

Introduction. Past disturbances have modified the structure and the floristic composition of Central African rainforests. These perturbations represent a driving force for forest dynamics and they are presumably at the origin of present-day forest mosaics. Fire is a prominent forest disturbance, leaving behind charcoal as a witness of past forest dynamics. The question arises whether quantification, dating and botanical identification of ancient charcoal fragments found in soil layers (pedoanthracology) allows a detailed reconstruction of forest history, including the possible occurrence of past disturbances. Material & methods. We organized pedoanthracological excavations in 6 regrowth sites and 48 sites of primary forests of Yangambi, Yoko, Masako and Kole in the Kisangani (RDC). We performed a detailed sampling in different vegetation types of a semi -deciduous rainforest (Yoko). Charcoal sampling was conducted in pit intervals of 10 cm. The charcoal was quantified whereby pottery fragments were also registered. A selection of charcoal fragments has been dated through AMS 14C measurement. Floristic identifications were conducted using. former protocols based on wood anatomy, which is largely preserved after charcoalification. Results. Charcoal was found in most pit intervals. The anthracomass in the soil of regrowth forests (secondary forests) is much higher than in the primary forest: 27,59 mg/kg for secondary forests et 2,53 mg/kg for primary forests. The specific soil anthracomass of the primary forest of the Yoko reserve is higher (7,7 mg/kg) than in Yangambi (1,9 mg/kg) , Masako (1,7 mg/kg) and Kole (0,8 mg/kg). No systematic differences have been found between soil charcoal content of the different forest type representing different forest histories. Gilbertiodendron dewevrei (De Wild.) J. Leonard forests showed surprisingly a higher concentration of soil charcoal. Discussion. Forest disturbances in the Kisangani region appear to be more recent than those in the Mayombe forest in Western RDC ( 3000-2000 calBP (Hubau, 2013)) and those of the Cameroon forest (2300-1300 calBP) (Morin-Rivat, J et al., 2014). Stratified charcoal conserved in the soil is a useful indicator of past forest disturbances. [less ▲]

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See detailCode du développement territorial et politique foncière
Fontaine, Pierre; Halleux, Jean-Marie ULg

Conference (2014, April 28)

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See detailApplication of multiple-point geostatistics on modelling pumping tests and tracer tests in heterogeneous environments with complex geological structures
Huysmans, Marijke; Dassargues, Alain ULg

in Geophysical Research Abstracts (2014, April 28)

In heterogeneous environments with complex geological structures, analysis of pumping and tracer tests is often problematic. Standard interpretation methods do not account for heterogeneity or simulate ... [more ▼]

In heterogeneous environments with complex geological structures, analysis of pumping and tracer tests is often problematic. Standard interpretation methods do not account for heterogeneity or simulate this heterogeneity introducing empirical zonation of the calibrated parameters or using variogram-based geostatistical techniques that are often not able to describe realistic heterogeneity in complex geological environments where e.g. sedimentary structures, multi-facies deposits, structures with large connectivity or curvi-linear structures can be present. Multiple-point geostatistics aims to overcome the limitations of the variogram and can be applied in different research domains to simulate heterogeneity in complex environments. In this project, multiple-point geostatistics is applied to the interpretation of pumping tests and a tracer test in an actual case of a sandy heterogeneous aquifer. This study allows to deduce the main advantages and disadvantages of this technique compared to variogram-based techniques for interpretation of pumping tests and tracer tests. A pumping test and a tracer test were performed in the same sandbar deposit consisting of cross-bedded units composed of materials with different grain sizes and hydraulic conductivities. The pumping test and the tracer test are analyzed with a local 3D groundwater model in which fine-scale sedimentary heterogeneity is modelled using multiple-point geostatistics. To reduce CPU and RAM requirements of the multiple-point geostatistical simulation steps, edge properties indicating the presence of irregularly-shaped surfaces are directly simulated. Results show that for the pumping test as well as for the tracer test, incorporating heterogeneity results in a better fit between observed and calculated drawdowns/concentrations. The improvement of the fit is however not as large as expected. In this paper, the reasons for these somewhat unsatisfactory results are explored and recommendations for future applications of multiple-point geostatistics on pumping tests and tracer tests are formulated. [less ▲]

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See detailDisproportionate contribution of riparian inputs to organic carbon in freshwater systems
Marwick, TR; Van Acker, K; Darchambeau, François ULg et al

Conference (2014, April 27)

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See detailInorganic and organic carbon spatial variability in the Congo River during high waters (December 2013)
Borges, Alberto ULg; Bouillon, S; Teodoru, C et al

Poster (2014, April 27)

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See detailMicrofossils’ diversity from the Proterozoic Taoudeni Basin, Mauritania
Beghin, Jérémie ULg; Javaux, Emmanuelle ULg; Houzay, Jean-Pierre et al

in European Geosciences Union General Assembly 2014 Vienna, Austria, 27 April – 02 May 2014 (abstract book) (2014, April 27)

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See detailEutrophication counteracts ocean acidification effects on DMS emissions
Gypens, N; Borges, Alberto ULg

Poster (2014, April 27)

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See detailTemporal variability and spatial distribution of suspended matter and organic C pool in the Zambezi River
Teodoru, C; Bouillon, S; Borges, Alberto ULg et al

Poster (2014, April 27)

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See detailAnaerobic methane oxidation in two tropical freshwater systems
Roland, Fleur ULg; Darchambeau, François ULg; Crowe, SA et al

Poster (2014, April 27)

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See detailThe age of river-transported carbon: new data from African catchments and a global perspective
Marwick, TR; Tamooh, F; Teodoru, C et al

Conference (2014, April 27)

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See detailProduction of dissolved organic matter by phytoplankton and its uptake by heterotrophic prokaryotes in large tropical lakes
Morana, C; Sarmento, H; Descy, J-P et al

Poster (2014, April 27)

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See detailTemporal variability and spatial dynamics of CO2 and CH4 concentrations and fluxes in the Zambezi River system
Teodoru, C; Borges, Alberto ULg; bouillon, S et al

Conference (2014, April 27)

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See detailDrivers on carbon dioxide emissions from the Scheldt river basin
Gypens, N; Passy, P; Garnier, J et al

Poster (2014, April 27)

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