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See detailNovel HDAC/DNMT Twin Inhibitors Interfere with Angiogenesis
Shiva Shankar, Thammadihalli Veerasangaiah ULg; Sulka, Béatrice ULg; Blacher, Silvia ULg et al

Poster (2011)

DNA methylation and histone deacetylation are two key epigenetic modifications that play central role in regulation of gene expression. Several studies have shown that histone deacetylases (HDAC) and DNA ... [more ▼]

DNA methylation and histone deacetylation are two key epigenetic modifications that play central role in regulation of gene expression. Several studies have shown that histone deacetylases (HDAC) and DNA methyltransferases (DNMT) inhibitors are potent anti-angiogenic compounds. Though combination of HDAC and DNMT inhibitors are now being examined in clinical trials of hematological malignancies, little work has been done to understand the effect of this combination on physiological and tumoral angiogenesis. We have designed and tested a family of twin drugs with intrinsic HDAC and DNMT inhibitory activities in relevant models of angiogenesis in vitro (Human Umbilical Vein Endothelial Cells – HUVEC and aortic ring) and in vivo (chick chorioallantoic membrane and Zebrafish). We have identified a lead compound having quantifiable anti-angiogenic effect without cytotoxicity affecting global histone acetylation and DNA methylation levels. In order to elucidate its anti-angiogenic mechanism, we characterized gene expression pattern simultaneously with the methylation profile of HUVEC cells treated with the lead compound and reference epigenetic modulators. This approach based on parallel microarray analyses permitted us to underscore a list of genes exclusively affected by the lead compound but not by other HDAC or DNMT inhibitors. These genes were then analyzed using the Ingenuity Pathway software revealing potential involvement of a subset of genes in angiogenesis. Our present aim is to validate the expression levels of a series of genes with respect to epigenetic mechanisms (histone modifications and DNA methylation). Finally, the biological relevance of the target genes will be explored by RNA silencing. Hence, we are using these novel epigenetic modulators as a tool to understand the regulatory mechanism of angiogenesis and to develop effective approaches to treat cancer. [less ▲]

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See detailULTRASONOGRAPHIC APPEARANCE OF THE CISTERNA CHYLI IN THE DOG
Etienne, Anne-Laure ULg; Cavrenne, Romain ULg; Garcia et al

Poster (2011)

Introduction/Aims The cisterna chyli (CC) is a dilated and bipartite portion of the lymphatic channels coursing intimately along the abdominal aorta in the retroperitoneal space.1 The appearance of the CC ... [more ▼]

Introduction/Aims The cisterna chyli (CC) is a dilated and bipartite portion of the lymphatic channels coursing intimately along the abdominal aorta in the retroperitoneal space.1 The appearance of the CC of the dog has been described on magnetic resonance imaging.2 The aim of this poster is to describe the ultrasonographic appearance of the CC in 2 dogs with chylous ascitis and in 2 healthy dogs. Methods Abdominal ultrasonography was realised with a 7.5MHz microconvex transducer. A right or left lateral dorsal approach was used. The aorta (together with the cranial mesenteric artery in normal dogs) was used as the main landmark to localize the CC. The dogs with chylous ascites were a 4 year old female american cocker spaniel, with immune-mediated hemolytic anemia and thrombocytopenia and a 1 year old, spayed female whippet with recurrent pancreatitis. The 2 healthy dogs were a 7 year old Beagle and a 9 year old Jack Russell. The abdominal ultrasonography was realised within 2 hours after the meal in the healthy dogs. Results The CC was seen as a hypoechoic structure, without detectable flow, dorsal and to the right of the aorta. The CC was easily visible in the 2 dogs with chyloabdomen while it was more difficult to localize in the healthy dogs. The CC was tubular on the longitudinal images. On transverse images, the CC is elliptic or semilunar and may partially surround the aorta. The maximal width of the CC measured on transverse images varied from 2-3mm in the 2 healthy dogs to 4-8mm in the 2 dogs with chyloabdomen. In 3 patients some efferent/afferent lymphatic vessels were seen as thin hypoechoic tubes converging on the CC. Shape and size of the CC in the same animal were seen varying during the same ultrasonography or between different exams. Discussion/Conclusion The CC is visible by ultrasonography in dogs. Its visibility depends on different conditions like disease of the lymphatic system3, quality and distance of the meal. [less ▲]

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See detailDry Season Carbon Dynamics in Savannah Grassland and Rainforest Dominated River Basins of Madagascar
Marwick, T.; van Acker, K.; Darchambeau, François ULg et al

Poster (2011)

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See detailThe glycine receptor is functionally expressed in migratory interneurons and influences early cortical development
Avila Macaya, Ariel Salvatore ULg; Nguyen, Laurent ULg

Poster (2011)

The strychnine-sensitive glycine receptor (GlyR) is a member of the ligand-gated ion channel superfamily. In the adult, the GlyR is known to mediate fast inhibitory neurotransmission in the spinal cord ... [more ▼]

The strychnine-sensitive glycine receptor (GlyR) is a member of the ligand-gated ion channel superfamily. In the adult, the GlyR is known to mediate fast inhibitory neurotransmission in the spinal cord and in the brainstem. The GlyR has also been described in the embryonic cortex after embryonic day 19 (E19) (Flint et al., 1998) where it could participate in developmental processes, but its presence at earlier stages has not been documented. Since other neurotransmitter systems, i.e. GABA and its receptors, are known to be potent signals that control corticogenesis (Nguyen et al., 2001; Ik-Tsen et al., 2007), we wondered if glycine and its GlyR could also fulfill such a function. In this study, we analyze GlyR expression and its physiological function in the early development of the cortex using in vitro cultures of embryonic day 13 slices, patch-clamp, two photon microscopy and immunocytochemistry. [less ▲]

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See detailDisulfide bond assignment and folding characterization of peptide toxins by Ion Mobility Mass Spectrometry
Echterbille, Julien ULg; Quinton, Loïc ULg; Rosu, Frédéric ULg et al

Poster (2011)

Introduction Animal venoms are mainly composed of peptide toxins, which are highly structured by several disulfide bridges. Disulfide bridges are a key feature as (i) they increase the toxins efficiency ... [more ▼]

Introduction Animal venoms are mainly composed of peptide toxins, which are highly structured by several disulfide bridges. Disulfide bridges are a key feature as (i) they increase the toxins efficiency by lowering their immunogenicity; (ii) they provide the adequate conformation for high affinity binding to the biological receptor. The sequencing and the determination of the cysteine pairing is still challenging and therefore an important step in their structure analysis and the understanding of their interactions with receptors. In this work, we present a new strategy to sequence structured toxins and assign S-S bridges using ion mobility resolved MS/MS. Methods The method relies on the analysis of partially reduced multiple-disulfide peptide. The mixture of the different forms is resolved by ion mobility, followed by MS/MS acquisition on each mobility separated species. The proof of concept has been successfully conducted on α-CnI, a toxin purified from the venom of Conus consors marine snail. The toxin sequence is GRCCHPACGKYYSC-NH2. It contains four cysteines linked together with two disulfide bridges. α-CnI was partially reduced by a small excess of tris(carboxyethyl)phosphine (10:1) at 56°C during 30min. The resulting mixture was purified by ZipTip C18 micro columns before analysis by infusion nanoESI-Synapt-G2. Fragmentation was performed after the mobility cell, to obtain specific fragments of each species. Mobilograms and mass spectra were analyzed using MassLynx (v4.1) and Driftscope (v2.1) from Waters. Preliminary data Partial reduction of a-CnI was performed in order to obtain a mixture of oxidized (the two disulfides are formed), reduced (the two disulfides have been reduced) and partially reduced forms (only one of the two disulfides has been reduced). The arrival time distribution of triply charged ions reveals the presence of 4 different species, characterized by a different relative cross sections in the gas-phase. The charge state of the ions influences the ion mobility separation. Mass matching allows identifying the species: the first mobility (the most compact structure) was identified to be the oxidized folded toxin (M=1541.58 Da). The latest peak, corresponding to the larger cross-section, was identified as the fully reduced toxin (M=1545.6 Da). The second and the third mobility peaks were attributed to the two partially reduced forms in which only one disulfide bridge was reduced (M=1543.59 Da). The change in ion mobility depends on which S-S bridge is reduced. Ion mobility separated species give characteristic fragment ions upon fragmentation in the transfer cell (i.e. after ion mobility separator). Interestingly, fragment ions coming from partially reduced species, especially the C-S or S-S bond cleavages, clearly indicates that the disulfide linkage of α-CnI is (Cys1-Cys3) and (Cys2-Cys4) as expected from literature. The method is now being applied with success to more complex systems containing 3 or 4 disulfide bridges. The influence of the charge state on the mobility separation is systematically analyzed in terms of structural implications. Novel aspect Sequencing and disulfide bridges assignment of peptide toxins using ion mobility resolved MS/MS [less ▲]

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See detailElaboration of tantalum oxide and carbon nanotubes composite coatings on titanium for biomaterial applications
Maho, Anthony ULg; Linden, Stéphanie; Arnould, Christelle et al

Poster (2011)

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See detailEarthworms smell microorganisms in soil
Zirbes, Lara ULg; Verheggen, François ULg; Mescher, Mark et al

Poster (2011)

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See detailEffect of prenatal undernutrition of the chicken embryo on growth and metabolism up to day 7
Willems, Els; Willemsen, Hilke; Li, Yue et al

Poster (2011)

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See detailAnalyses biophysiques des interactions peptide-monocouches à l’interface air-eau
Nasir, Mehmet Nail ULg; Benichou, Emmanuel; Brevet, Pierre-François et al

Poster (2011)

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See detailThe Influence of aromatic solvents on CuPc blue pigments
Defeyt, Catherine ULg; Vandenabeele, Peter; Lycke, Sylvia et al

Poster (2011)

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See detailPhysico chemical characterization of biosurfactants micelles or Physico-aggregates produced by B. subtilis during their membrane separation
Coutte, F.; Jauregi, P.; Lecouturier, D. et al

Poster (2011)

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See detailProduction subjective de rêve en milieu carcéral : une hypothèse adaptative
Englebert, Jérôme ULg; Gauthier, Jean-Marie ULg; Jacquemart, Catherine

Poster (2011)

Une étude sur le rêve n’est pas sans poser plusieurs questions épistémologiques et méthodologiques majeures. La première d’entre elles tient à l’essence même du rêve qui est un objet d’étude particulier ... [more ▼]

Une étude sur le rêve n’est pas sans poser plusieurs questions épistémologiques et méthodologiques majeures. La première d’entre elles tient à l’essence même du rêve qui est un objet d’étude particulier, étant strictement subjectif et difficilement objectivable. Le rêve n’existe dans la vie consciente qu’au passé ; il a une conscience uniquement rétrospective. Il existe donc un décalage temporel entre l’activité onirique et le discours sur le rêve. Ce hiatus temporel condamne donc le rêve à nous échapper dans sa finitude et pousse le chercheur à capituler face à la connaissance ultime et globale du monde imaginaire de l’individu. L’étude que nous avons réalisée se veut d’inspiration phénoménologique. Nous avons administré un questionnaire (questionnaire élaboré sous la supervision d’un collège d’experts travaillant en milieu carcéral) à une population de 48 détenus (43 hommes et 5 femmes) et à une population contrôle (appariée pour l’âge et le niveau d’étude). Le questionnaire était scindé en deux parties pour les détenus (rapport aux rêves avant l’enfermement [Gd.0] / rapport aux rêves maintenant [Gd.1]) et celui pour la population contrôle ne comprenait qu’une partie (rapport aux rêves maintenant [Gc]). Enfin, nous avons isolé trois groupes au sein de la population carcérale : Cp : Courte peine effectuée (maximum 90 jours), MP : Moyenne peine effectuée (plus de 90 jours et maximum 2 ans), LP : Longue peine effectuée (plus de 2 ans). Les résultats, qu’il conviendra de discuter dans le détail, mettent en évidence que l’activité onirique serait un mécanisme que le détenu utilise pour s’adapter à l’univers carcéral (la fréquence subjective de rêve et l’intérêt porté à ses rêves sont significativement plus importants pour le Gd.1 que le Gd.0 et le Gc). Mais ce constat tend à diminuer en fonction de la durée de la peine (au-delà de 2 ans d’enfermement [LP]). Nous pouvons expliquer cette diminution significative par un effet d’habituation (le rêve aurait permis un retour à une homéostasie psychique suffisante) ou par une abrasion du mécanisme. En effet, le rêve ne procurerait aucune modification dans le réel puisque le quotidien de l’enfermement reste le même. Privée de boucle de rétroaction, la fonction adaptative du rêve s’essoufflerait. [less ▲]

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See detailMyocardial Dynamic Contrast-enhanced MR: Artifacts and Physiopathological Pitfalls
NCHIMI LONGANG, Alain ULg; RASKINET, B; MORAR, A et al

Poster (2011)

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See detailExpansion of the Magdalenian in Northwest Europe
Miller, Rebecca ULg; Noiret, Pierre ULg

Poster (2011)

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See detailSynthesis and hydrolytic stability of novel 3-[18F]fluoroethoxybis(1-methylethyl)silyl]propanaminebased prosthetic groups
collet, Charlotte; Lamandé-Langle, Sandrine; Balentova, Eva et al

Poster (2011)

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See detailVariability of insulin sensitivity for diabetics and non-diabetics during the first 3 days of ICU stay
Pretty, Christopher G.; Le Compte, Aaron; PREISER, Jean-Charles ULg et al

Poster (2011)

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See detailHuman brucellosis in North-East Ecuador: prevalence, typifying Brucella spp., and risk factors
Ron-Roman, J; Benitez-Ortiz, Washington; Ron-Garrido, L et al

Poster (2011)

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See detailThe effect of insulin injection on the glucose metabolism of the chicken embryo
Franssens, Lies; Willems, Els; Willemsen, Hilke et al

Poster (2011)

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See detailMacropinocytosis of human papillomaviruses in natural killer cells via CD16 induces cytotoxic granule exocytosis and cytokine secretion
Renoux, V; Langers, I; Clémenceau, B et al

Poster (2011)

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See detailCaractérisation des composés volatils des huiles d’olive produites dans des coopératives de la région orientale du Maroc
Tanouti, K.; Serghini-Caid, H.; Sindic, Marianne ULg et al

Poster (2011)

L'objectif principal de cette étude est de faire progresser nos connaissances sur le profil volatil des huiles d’olive produite dans les régions du Maroc oriental. L’identification des composés volatils des ... [more ▼]

L'objectif principal de cette étude est de faire progresser nos connaissances sur le profil volatil des huiles d’olive produite dans les régions du Maroc oriental. L’identification des composés volatils des échantillons d’huiles d’olive provenant des coopératives de la région orientale du Maroc et la comparaison aux profils de volatils d’huiles européennes a été réalisée on utilisant la méthode de la microextraction en phase solide (SPME) couplée à la GC/MS. [less ▲]

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See detailThick and crack-free nanocrystalline mesoporous TiO2 films obtained by capillary coating from aqueous solutions
Krins, Natacha ULg; Faustini, Marco; Louis, Benjamin et al

Poster (2011)

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See detailRelease and innate immune detection of host cell DNA mediate the adjuvant activity of aluminum salts
Marichal, Thomas ULg; Ohata, K; Bedoret, D et al

Poster (2011)

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See detailDéontologie de l'information : journée d'étude
Vanesse, Marc ULg

Poster (2010, December 14)

Journée de réflexion sur la déontologie journalistique avec le bâtonnier de l'Ordre des avocats de Liège, le secrétaire général du Conseil de déontologie, un journaliste d'investigation et le secrétaire ... [more ▼]

Journée de réflexion sur la déontologie journalistique avec le bâtonnier de l'Ordre des avocats de Liège, le secrétaire général du Conseil de déontologie, un journaliste d'investigation et le secrétaire général adjoint de l'Association des journalistes. [less ▲]

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See detailChanges in functional interactions during anaesthesia-induced loss of consciousness
Schrouff, Jessica ULg; Perlbarg, Vincent; Boly, Mélanie ULg et al

Poster (2010, December 12)

Consciousness has been related to the amount of integrated information that the brain is able to generate. In this paper, we tested the hypothesis that the loss of consciousness caused by propofol ... [more ▼]

Consciousness has been related to the amount of integrated information that the brain is able to generate. In this paper, we tested the hypothesis that the loss of consciousness caused by propofol anesthesia is associated with a significant reduction in the capacity of the brain to integrate information. To assess the functional structure of the whole brain, functional integration and partial correlations were computed from fMRI data acquired from 18 healthy volunteers during resting wakefulness and propofol-induced deep sedation. Total integration was significantly reduced from wakefulness to deep sedation in the whole brain as well as within and between its constituent networks (or systems). Integration was systematically reduced within each system (i.e., brain or networks), as well as between networks. However, the ventral attentional network maintained interactions with most other networks during deep sedation. Partial correlations further suggested that functional connectivity was particularly affected between parietal areas and frontal or temporal regions during deep sedation. Our findings suggest that the breakdown in brain integration is the neural correlate of the loss of consciousness induced by propofol. They stress the important role played by parietal and frontal areas in the generation of consciousness. [less ▲]

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See detailA zealous parallel gradient descent algorithm
Louppe, Gilles ULg; Geurts, Pierre ULg

Poster (2010, December 11)

Parallel and distributed algorithms have become a necessity in modern machine learning tasks. In this work, we focus on parallel asynchronous gradient descent and propose a zealous variant that minimizes ... [more ▼]

Parallel and distributed algorithms have become a necessity in modern machine learning tasks. In this work, we focus on parallel asynchronous gradient descent and propose a zealous variant that minimizes the idle time of processors to achieve a substantial speedup. We then experimentally study this algorithm in the context of training a restricted Boltzmann machine on a large collaborative filtering task. [less ▲]

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See detailUse of pure ionic liquids as solvents for the lipase catalyzed synthesis of fatty acid sugar esters
Galonde, Nadine ULg

Poster (2010, December 10)

Sugar fatty acid esters are non-ionic surfactants commonly used in the pharmaceutical, cosmetic and food industries. Their enzymatic synthesis can be hindered by the low solubility of sugars in the ... [more ▼]

Sugar fatty acid esters are non-ionic surfactants commonly used in the pharmaceutical, cosmetic and food industries. Their enzymatic synthesis can be hindered by the low solubility of sugars in the organic solvents commonly used with lipases. Ionic liquids (ILs) have gained attention as particularly attractive “green” alternatives to organic solvents for carbohydrate biotransformation. Indeed, many ILs are good solvents for polar (e.g. carbohydrates) and less polar compounds. Furthermore, their use as reaction media can enhance the enzymatic reactivity, selectivity and stability. In this context, our study focused on the influence of using ILs as reaction medium for the lipase catalyzed synthesis of mannosyl myristate. The effect of the IL nature on the enzymatic reaction initial yield and rate was examined. [less ▲]

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See detailE.coli prpoS::gfp strain as biosensor of glucose heterogeneity inside industrial bioreactors
Brognaux, Alison ULg; Delvigne, Frank ULg; Thonart, Philippe ULg

Poster (2010, December 08)

• OBJECTIVE: Escherichia coli is a microorganism widely used in the industry for the production of recombinant proteins. The performances obtained at the laboratory level are not reproducible at a large ... [more ▼]

• OBJECTIVE: Escherichia coli is a microorganism widely used in the industry for the production of recombinant proteins. The performances obtained at the laboratory level are not reproducible at a large scale. Actually, the mixing operation is not efficient enough: gradients of glucose and oxygen appear when operating in fed-batch mode (addition of glucose during the culture). These gradients cause adverse impacts on the production of biomass and recombinant protein. The aim of this work is to use the microbial population as biocaptor of the encoutered stress inside heterogeneous industrial bioreactors to better scale-up and regulate these reactors. • MATERIALS AND METHODS: A plasmid carrying a stress promoter followed by the coding sequence of the Green Fluorescent Protein (GFP) is introduced in the bacterial host (in our case, the strain E. coli K12 will be considered as a model organism). When the cell is submitted to given stress condition, GFP synthesis is induced and accumulated into the cytoplasm, leading to the increase of the cell's fluorescence. Flow cytometry detection is used in order to quantify the fluorescence at the single cell level. Obtained results are frequency histograms of fluorescenceintensity in the microbial population • RESULTS: The rpoS gene is a gene of the general stress response, mainly induced at the entrance to stationary phase (during a lack of glucose). The tracking of the GFP fluorescence linked to the activation / repression of the rpoS promoter gives good results. Indeed, there is appearance of a segregation at the level of the GFP content among the microbial population. The intensity of the segregation, as well as its time of appearance during the culture can be related to the bioreactor mixing efficiency. • CONCLUSION: prpoS::gfp strains can be used as biosensors of the heterogeneity of glucose encountered inside industrial reactors. • POTENTIAL APPLICATIONS & KEY BENEFITS: These strains could be used to validate a fed-batch regulation (addition of glucose) at the industrial level. [less ▲]

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See detailAzoxystrobin and epoximazole sensitivity profiles of Mycosphaerella graminicola populations from the Grand-Duchy of Luxemburg in 2007 and 2008
Vrancken, Carine; Dubos, Tiphaine; El Jarroudi, Moussa ULg et al

Poster (2010, December 07)

Mycosphaerella graminicola strains were isolated from symptomatic winter wheat (Triticum aestivum) and spelt (Triticum spelta) leaves sampled across the Grand-Duchy of Luxembourg. In total, 484 strains ... [more ▼]

Mycosphaerella graminicola strains were isolated from symptomatic winter wheat (Triticum aestivum) and spelt (Triticum spelta) leaves sampled across the Grand-Duchy of Luxembourg. In total, 484 strains were isolated from winter wheat, and 31 from spelt leaves. The sensitivity profiles of these strains towards azoxystrobin (Amistar®, Syngenta Agro GmbH, Germany) and against epoxiconazole (Opus®, BASF Belgium NV/S A, Brussels, Belgium) were assessed in microplates, allowing to test 10 different concentrations for each active substance (0, 0.00316, 0.01, 0.0316, 0.1, 0.316, 1, 3.16, 10 and 31.6μg/mL). 100μ g/mL of salicylhydroxamic acid (SHAM) was also added to the medium, in order to prevent the strains from using alternative respiration. Results of the sensitivity tests for azoxystrobin showed a dose-dependent decrease of in vitro growth for all the strains. During both years, strains could be divided into two distinct sub-populations in relation to their azoxystrobin sensitivity, thus forming a bimodal distribution commonly reported to be associated with a single gene-mediated resistance. For wheat, the dominant sub-population was the one showing full resistance to azoxystrobin. The results of the sensitivity tests to epoxiconazole in liquid media showed a dose-dependent decrease of fungal growth for all the strains tested. The EC50 values followed an unimodal distribution. When the sensitivity distribution of the strains collected in 2008 (n=379) was compared to that observed in 2007, although the populations have remained unimodal, a minor shift towards less sensitive populations was observed. Compared to strains originating from wheat, the spelt strains were more sensitive towards both fungicides (p ≤ 0.001). [less ▲]

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See detailEvaluating analytical results reliability using a Bayesian probability criterion
Rozet, Eric ULg; Lebrun, Pierre ULg; Boulanger, Bruno ULg et al

Poster (2010, December 02)

In pharmaceutical industries, quantitative analytical methods such as HPLC play a key role. Indeed, the analytical results obtained from them are used to make crucial decisions such as the release of ... [more ▼]

In pharmaceutical industries, quantitative analytical methods such as HPLC play a key role. Indeed, the analytical results obtained from them are used to make crucial decisions such as the release of batches of drugs, the evaluation of safety and efficacy of new drug candidates or the monitoring of patients health. Prior to their routine use, analytical methods are submitted to a stringent validation study where they have to demonstrate that they are fit for their final purpose, i.e. providing accurate result . Typically this demonstration is made by either providing point estimates of systematic error (bias) and random error (variance) or sometimes by providing interval estimates of these statistical parameters at several well defined concentration levels of the target analyte. They are then compared to maximum acceptable levels. More recently, tolerance intervals approaches have been proposed that are evaluated in a similar way at these key concentration levels. However none of these decision approaches allow knowing the probability to obtain accurate results over the whole concentration range of interest. Frequentist approximations have been proposed to estimate this probability but only at the concentration levels experimentally tested and not for the whole range of interest. In this work, a linear hierarchical Bayesian approach is proposed. It takes into account the potential random characteristic of the slope and intercept observed from one analytical run to the other, and also integrates the possible covariance between the parameters. Additionally, heteroscedasticity of the residual variance over the concentration range investigated is taken into account. A situation regularly observed in practice. Finally a reliability profile for the whole concentration range studied is obtained using MCMC sampling. This profile provides the probability (Prel) to obtain accurate results over the full concentration range investigated. This profile is then compared to a minimum reliability probability (Pmin) that will define the valid concentration range of the analytical method. The usefulness of this approach is illustrated through the validation of a bioanalytical method and also compared with a one concentration level at a time frequentist approach derived from tolerance intervals. [less ▲]

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See detailOrgano-mineral imprints in fossil cyanobacterial mats of an Antarctic lake
Javaux, Emmanuelle ULg; Lepot, Kevin ULg; Deremiens, Leo et al

Poster (2010, December)

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See detailA GPS/GNSS dense network used to monitor ionospheric positioning error
Wautelet, Gilles ULg; Lejeune, Sandrine; Warnant, René ULg

Poster (2010, December)

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See detailOPTIMIZACIÓN DE BIOMATERIALES PARA MODIFICACIÓN DE LA SUPERFICIE CELULAR
Cerda-Cristerna, B.I.; Flores, H; Pozos, A et al

Poster (2010, December)

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See detailResearch activities in 3D sound and Auralization (in Intelsig)
Embrechts, Jean-Jacques ULg

Poster (2010, December)

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See detailConservation of endemic plants from the Katanga copper belt (DR Congo)
Lebrun, Julie ULg; Minengo Handjila, Guylain; Weiskopf, Thomas et al

Poster (2010, December)

The Katanga copper belt, where natural outcrops of copper-rich rocks are colonised by highly original plant communities, has been recognised as a hotspot for metallophyte species. The flora comprises more ... [more ▼]

The Katanga copper belt, where natural outcrops of copper-rich rocks are colonised by highly original plant communities, has been recognised as a hotspot for metallophyte species. The flora comprises more than 600 species from which 30 are endemics. These plants represent a valuable phytogenetic resource for revegetation and restoration programs, for the phytostabilisation and for the remediation of heavy metal pollutions. However, the flora of metalliferous soils is threatened by mining activities in Katanga. Actions aiming at preserving these species are therefore urgent. Since 2007, a unique conservation project has been launched by scientists supported by a mining company. The aim is to elaborate a program that allows biodiversity conservation while being compatible with mining activities. The project combines in-situ and ex-situ conservation strategies involving ecosystem reconstruction, species translocations, protected areas designation and the development of seed banks in Belgium and in Katanga. [less ▲]

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See detailNANOTRIBOLOGICAL AND NANOMECHANICAL CHARACTERIZATIONS OF MEMS MATERIALS
Pustan, Marius ULg; Rochus, Veronique; Golinval, Jean-Claude ULg

Poster (2010, December)

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See detailVaccine against human papillomavirus (HPV)-associated lesions induces collaboration between natural killer and dendritic cells in vitro.
Langers, Inge ULg; Reschner, Anca ULg; Renoux, Virginie ULg et al

Poster (2010, December)

Cervical cancer, the second most frequent gynaecological malignancy in the world, is caused by infection with high-risk human papillomaviruses (HPV). HPV16 and/or 18 are detected in more than 70% of these ... [more ▼]

Cervical cancer, the second most frequent gynaecological malignancy in the world, is caused by infection with high-risk human papillomaviruses (HPV). HPV16 and/or 18 are detected in more than 70% of these tumours. Prophylactic HPV-L1 virus like particle (VLP) vaccines are highly efficient to protect against HPV16 and HPV18 infection, but not against established infection. In this context, we study the effect of HPV-VLP on natural killer cells (NK) and on the crosstalk between NK and Dendritic Cells (DC). In order to know if HPV-VLP are able to enter in NK cells, we used fluorescent HPV-VLP with flow cytometry and confocal microscopy. HPV-VLP were internalised more rapidly in NK cells than in DC. They were already detected inside NK cells after 10 min of contact at 37°C. We also observed in CD107 assays, that HPV-VLP induce degranulation of NK cytotoxic granules. Previous works have shown that HPV-VLP were able to activate DC. We confirmed these results and observed an increase of CD69 cell surface expression and IFN-γ production by NK cells in the presence of DC activated by VLP. Interestingly, NK cells seemed to further activate DC in the presence of VLP as shown by an up-regulation of HLA-DR and CD86 on DC. Moreover, NK cells in the presence of HPV-VLP induced the production of IL12p70, but not the immunosuppressive cytokine IL10. Our results suggest that NK cells could play a role in the activation of DC induced by HPV-VLP during the vaccination against cervical cancer. Supported by the Belgian FNRS-Télévie [less ▲]

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See detailUsing 3D to understand human motion
Schwartz, Cédric ULg; Forthomme, Bénédicte ULg; Bruls, Olivier ULg et al

Poster (2010, December)

The understanding and tracking of human motion has been a subject of interest in the scientific community for more than one century. The long history of human motion analysis comes from the large scope of ... [more ▼]

The understanding and tracking of human motion has been a subject of interest in the scientific community for more than one century. The long history of human motion analysis comes from the large scope of applications of such measurement that can be found in medicine, biomechanics, sport, ergonomics, and even civil engineering. More recently, those technologies have also been widely exploited for the development of animation movies and games. Needless to say, the techniques used one century ago significantly differ from those used today. This paper describes in a first part the evolution of the technological capabilities for motion analysis and the actual limitations. From this analysis and in a second part, we describe the experience related to the creation of a motion analysis laboratory at the University of Liège and show how such a platform could be the center of a multidisciplinary research and provide valuable information to various communities. [less ▲]

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See detailRank-constrained linear regression: a Riemannian approach
Meyer, Gilles ULg; Bonnabel, Silvère; Sepulchre, Rodolphe ULg

Poster (2010, December)

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See detailAlternative photosynthetic electron pathways in different clades of Symbiodinium: the Mehler reaction
Roberty, Stéphane ULg; Poulicek, Mathieu ULg; Franck, Fabrice ULg

Poster (2010, December)

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium commonly ... [more ▼]

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium commonly referred to as zooxanthellae. These photosynthetic algae translocate a majority of their photosynthetically fixed carbon to the host and contribute greatly to their metabolic needs (Muscatine, 1990) and the calcification process (Gattuso, 1999). In the natural environment the holobiont have to cope with significant daily variations in light intensities that sometimes exceed Symbiodinium photosynthetic capacity. Fortunately, photosynthetic organisms possess regulatory features that help to ensure that high light intensities can be endured without the accumulation of photodamage. Thus, the regulation of photosynthesis can be viewed as a dynamic balance between photosynthetic efficiency (photochemical quenching) and photoprotection processes (i.e. non-photochemical quenching). Among them, the role of O2 as an alternative electron acceptor within the chloroplast could play a critical role (Ort & Baker, 2002). Under particular environmental conditions when sinks for photosynthetic electrons are scarce, the direct reduction of oxygen by the PSI could sustain significant levels of photosynthetic electron flux by initiating the ΔpH formation and of NPQ, regulating the ratio of ATP/NADPH to match the requirements of carbon reduction. However, this process leads to the formation of reactive oxygen species that are rapidly detoxified by superoxide dismutase and ascorbate peroxidase. An additional electron flux associated with this oxygen pathway is directed to the reduction of monodehydroascorbate (MDA), which is generated as a result of peroxide reduction by ascorbate (Asada, 2000). The present study aimed to highlight the existence of alternative photosynthetic electron pathways and more especially the Mehler ascorbate peroxidase pathway in different clades of Symbiodinium, cultivated at low and high light intensities. -Muscatine L (1990) The role of symbiotic algae in carbon and energy flux in reef corals. In: Dubinsky Z(ed) Ecosystems of the world: coral reefs. Elsevier, Amsterdam, pp 1-9. -Gattuso JP, Allemand D and M Frankignoulle (1999) Photosynthesis and calcification at cellular, organismal and community levels in coral reefs: A review on interactions and control by carbonate chemistry. American Zoologist 39(1): 160-183. -Ort, D. R. and N. R. Baker (2002). A photoprotective role for O2 as an alternative electron sink in photosynthesis? Current Opinion in Plant Biology 5(3): 193-198. -Asada, K. (2000) The water-water cycle as alternative photon and electron sinks. Philosophical Transactions of the Royal Society B-Biological Sciences 355(1402): 1419–1431. [less ▲]

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See detailPattern of early eukaryote evolution in Precambrian oceans
Javaux, Emmanuelle ULg

Poster (2010, December)

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See detailRelating Jupiter's auroral features to magnetospheric sources
Vogt, Marissa F.; Kivelson, Margaret G.; Khurana, Krishan K. et al

Poster (2010, December)

In order to understand the physical processes that produce the various auroral features we must first understand how the auroral emissions are linked to magnetospheric sources. However, magnetic mapping ... [more ▼]

In order to understand the physical processes that produce the various auroral features we must first understand how the auroral emissions are linked to magnetospheric sources. However, magnetic mapping of Jupiter’s polar auroral emissions to equatorial regions in which source currents are plausibly generated is highly uncertain because the available field models are inaccurate beyond ~30 Jovian radii. We have related auroral features to their magnetospheric sources through a flux equivalence calculation, where we require that the magnetic flux in some specified region at the equator equals the magnetic flux in the area to which it links in the ionosphere. This approach is preferred to tracing model field lines for mapping the auroral polar regions, because the latter method is inaccurate at large distances. Here we present our results, highlighting new mappings for the southern hemisphere, and will compare our mapping to auroral observations from both hemispheres. In particular we relate equatorial regions in which reconnection events have been identified with the locations of polar dawn spots and other possible auroral signatures of tail reconnection. We find that the mapping reproduces several other key auroral features. The polar auroral active region maps to just outside the dayside magnetopause, a region that we identify as the Jovian polar cusp. The polar auroral swirl region maps to open tail field lines and is interpreted as the Jovian polar cap. These interpretations are consistent with some earlier predictions based on auroral observations. We identify the boundary between open and closed flux in the ionosphere, which previously was not well defined. We show that the magnetic flux through the regions interpreted as the polar caps in both hemispheres closely matches the estimated flux through the tail lobe, consistent with the suggestion that this area maps to open field lines. [less ▲]

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See detailDiscovery of pulsed polar flares in the Jovian aurorae
Bonfond, Bertrand ULg; Vogt, M~F; Grodent, Denis ULg et al

Poster (2010, December)

The most active part of the aurora at Jupiter is certainly the polar region, i.e. the emissions located poleward of the main auroral oval. This region is known to occasionally show localized but dramatic ... [more ▼]

The most active part of the aurora at Jupiter is certainly the polar region, i.e. the emissions located poleward of the main auroral oval. This region is known to occasionally show localized but dramatic enhancements of its brightness, referred to as polar flares. These emissions have been associated with the polar cusp, based on their location in the polar cap. In summer 2009, right after the refurbishment of the Space Telescope Imaging Spectrograph camera, the Hubble Space Telescope acquired the longest high-time resolution sequence ever of images of the Jovian aurora. We report the first observations of a quasi-periodicity in the occurrence of these flares, with a timescale of ~2-3 minutes. By using a magnetic flux mapping model, we show that these features originate from a region located at a radial distance ranging from 80 to 100 Jovian radii and local times between 10:00 and 15:00. As a consequence, by analogy with similar behaviors observed in the Earth aurora, we suggest that these emissions could be attributed to pulsed reconnections in the dayside magnetopause. [less ▲]

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See detailChitosan nanofiber membranes for tissue engineering - synthesis, characterization and properties
Toncheva, Natalia ULg; Aqil, Abdelhafid ULg; Croisier, Florence ULg et al

Poster (2010, November 29)

This poster was presented by Natalia Toncheva

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See detailNew fluorinated surfactants for nanogels preparation in supercritical CO2
Alaimo, David ULg; Beigbeder, Alexandre; Dubois, Philippe et al

Poster (2010, November 29)

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See detailElectrografting and LbL deposition for the elaboration of antimicrobial coatings
Aqil, Abdelhafid ULg; Cécius, Michaël; Jérôme, Christine ULg

Poster (2010, November 29)

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See detailRoutes for the preparation of advanced polymer/carbon nanoparticles based materials
Vuluga, Daniela ULg; Thomassin, Jean-Michel ULg; Huynen, Isabelle et al

Poster (2010, November 29)

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See detailPMMA/carbon nanotube nanocomposites foams for EMI shielding application
Thomassin, Jean-Michel ULg; Molenberg, Isabel; Huynen, Isabelle et al

Poster (2010, November 29)

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See detailTight Glycemic Control Models for Critically Ill Patients in Intensive Care Units
Penning, Sophie ULg; Le Compte, Aaron; Desaive, Thomas ULg et al

Poster (2010, November 26)

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See detailComputational modelling of calcium mediated bone regeneration
Carlier, Aurélie ULg; Chai, Yoke Chin; Theys, Tina et al

Poster (2010, November 26)

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See detailInfluence of thermoelectric coupling on ectopic beats generated by mechano-electric feedback (MEF) in a one-dimensional cardiac fiber model
Collet, Arnaud ULg; Desaive, Thomas ULg; Pierard, Luc ULg et al

Poster (2010, November 26)

The influence of thermal processes on electrophysiology has clearly been underlined by Bini et al., using a FitzHugh--Nagumo-type (FHN-type) model. When the temperature is raised, the action potential ... [more ▼]

The influence of thermal processes on electrophysiology has clearly been underlined by Bini et al., using a FitzHugh--Nagumo-type (FHN-type) model. When the temperature is raised, the action potential duration (APD) has been shown to shorten, while the action potential (AP) amplitude decreases, and the conduction velocity increases. In this research, we investigate the effects of thermoelectric coupling on mechano-electric feedback (MEF), and more specifically, on ectopic beats generated by MEF. To investigate these effects, thermoelectric coupling is introduced in a one-dimensional electromechanical model of a cardiac fiber, which considers excitation-contraction coupling (ECC), as well as MEF. [less ▲]

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See detailModeling the instantaneous pressure-volume relationship in the left ventricle
Lucas, Alexandra ULg; Dauby, Pierre ULg; Kolh, Philippe ULg et al

Poster (2010, November 26)

Pressure-volume loops are a common modeling tool of the cardiovascular system. They are very useful because they characterize the global function of the cardiac pump and can also be analyzed ... [more ▼]

Pressure-volume loops are a common modeling tool of the cardiovascular system. They are very useful because they characterize the global function of the cardiac pump and can also be analyzed by considering the various phases of the cardiac cycle and marking each point of a cycle with the corresponding time. When several loops are considered, the points corresponding to the same time t in each loop can be joined to define a curve named isochrone. In this work, we are interested in models of the instantaneous pressure-volume relationship, i.e. isochrone models. More precisely, we concentrate on the 6 models considered by Lankhaar et al. [1] and we propose a critical analysis of the work of these authors and suggest some improvement of their procedure. [1] Lankhaar J.W. et al. Annals of Biomedical Engineering, Volume 37, Number 9, 1710-1726, 2009. [less ▲]

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See detailA Boolean network model of the growth plate
Kerkhofs, Johan ULg; Roberts, Scott J; Luyten, Frank P et al

Poster (2010, November 26)

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See detailMultiple Material Mesh Generation For Biomedical Applications
D'Otreppe, Vinciane ULg; Boman, Romain ULg; Ponthot, Jean-Philippe ULg

Poster (2010, November 26)

The finite element (FE) method is commonly used in biomedical applications for the simulation of the behaviour of biological structures. A key component in FE simulation is the creation of a finite ... [more ▼]

The finite element (FE) method is commonly used in biomedical applications for the simulation of the behaviour of biological structures. A key component in FE simulation is the creation of a finite element mesh. In medical applications, the meshes should be directly generated from the medical scans. Moreover, biological structures are usually composed of several inner regions that need to be separately segmented, labelled and meshed to be able to apply different material properties in the finite element model. A procedure to create surface meshes from a multi-valued volume data sets is proposed. Following properties are guaranteed: (1) The generated mesh consists of a set of non manifold triangle meshes that separate each connected component in the labelled data set. These interface meshes join each other consistently along their boundaries, i.e., no T junctions nor gaps may appear. (2) The surface mesh is a geometrically accurate representation of the data represented in the medical scans. However, it is not be tainted by the typical aliasing and staircase artifacts that are due to the discrete nature of the voxels. [less ▲]

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See detailMinimal cardiovascular system model including physiological mitral valve opening
Paeme, Sabine ULg; Moorhead, Katherine ULg; Chase, J. Geoffrey et al

Poster (2010, November 26)

This research describes a new closed-loop cardiovascular system (CVS) model including a model of the left atrium and a model describing the progressive aperture of the mitral valve

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See detailTendon lesion and platelet-rich plasma (PRP) injection
Kaux, Jean-François ULg; Drion, Pierre ULg; Renouf, Julien et al

Poster (2010, November 25)

Introduction: For a few years, the positive effects of platelets on the healing process of different tissues (skin, bones...) were demonstrated. In fact platelets contain lots of growth factors which can ... [more ▼]

Introduction: For a few years, the positive effects of platelets on the healing process of different tissues (skin, bones...) were demonstrated. In fact platelets contain lots of growth factors which can be release locally and enhance the healing process. Thus the aim of our experiment was to ascertain by an original mechanical measure whether the use of PRP was of interest for accelerating the healing process of rats’ Achilles tendons after surgical induced lesion. Methods: A 5mm defect was surgically induced in 90 rats’ Achilles tendon. Rats were divided into 2 groups of 45: (A) control (no treatment) and (B) PRP treatment. Rats of group B received a PRP injection in situ after the surgery. Afterwards, rats of both groups were placed in their cages without immobilization. After 5, 15 and 30 days, 10 traumatized Achilles tendons of each group were dissected and removed. Immediately after sampling, tendons were submitted to a biomechanical tensile test up to rupture, using a “Cryo-jaw”. After that, transcriptomic analyses were made on the tendon samples, to study the expression of type III collagen, matrix metalloproteases and tenomodulin. A hydroxyproline dosage was finally realised to quantify the collagen in the tendon during its healing process. Tendons of the 15 remaining rats of each group were subjected to a histological study, respectively at day 5, 15 and 30 (5 rats for each time). Results: We demonstrated that (1) the stress (F) during biomechanical tensile test up to tendon rupture was significantly greater for tendons which had been submitted to an injection of PRP compared to the control group; (2) the surface (S) area of the section of the tendon was greater in the PRP group during the 15 first days, but this section was similar after 30 days in the 2 groups; (3) the ration F/weight of the rat was significantly greater in the PRP group at each time; (4) constrain was similar after the 15 first days but was significantly greater in the PRP group after 30 days. Histological study showed that PRP could enhance cells proliferation, angiogenesis and collagen organisation. Our biochemical analyses did not explain beneficial effects of PRP. Indeed, there was no significant difference between the expressions of different studied genes. Conclusion: Our animal study demonstrated that an injection of PRP could accelerate the tendons healing process and improve its quality. [less ▲]

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See detailTendon lesion and VEGF-111 injection
Kaux, Jean-François ULg; Drion, Pierre ULg; Libertiaux, Vincent ULg et al

Poster (2010, November 25)

Introduction: Tendon lesion is one of the most frequent pathology in sports and by physical workers. This pathology often becomes chronic. For this reason, it is of interest to develop new treatments ... [more ▼]

Introduction: Tendon lesion is one of the most frequent pathology in sports and by physical workers. This pathology often becomes chronic. For this reason, it is of interest to develop new treatments. Injection of platelet-rich plasma (PRP) seems to be a promising one by releasing growth factors (GF) locally. Among all the GF released by activated platelets, the vascular endothelial growth factor-A (VEGF-A) is known to induce positive effects on vascular function and angiogenesis, and could be implicated in the healing process of tendons. Recently, a novel VEGF-A isoform was identified, the VEGF-111, a biologically active and proteolysis-resistant VEGF-A isoform, also known to present beneficial effects on ischemic diseases. This prompted us to evaluate whether VEGF-111 would have a therapeutic interest within the framework of the tendon pathology. Methods: 60 Rats were divided into 2 groups: A: control (no injection), B: VEGF-111 treatment. A 5mm defect was surgically induced in rat Achilles tendon after resection of plantaris tendon. Rats received a local injection of VEGF-111 (100ng) in situ after the surgery and were placed in their cages without immobilization. After 5, 15 and 30 days, the traumatized Achilles tendons of 10 rats of both groups were removed and dissected during their healing process. Immediately after sampling, tendons were submitted to a biomechanical tensile test up to rupture, using a “Cryo-jaw”. Rats were then euthanized. Statistical analyses were made with an ANOVA. Values are significant when p-value is below 0.05. Results: Our results showed that the developed force necessary to induce tendon rupture during biomechanical tensile test was greater for tendons which had received an injection of 100ng of VEGF-111. These results were already noticed from day 5 onwards. The ratio between force and weight increased with time in both groups, but this ratio was greater for tendons which had been submitted to an injection of VEGF111. The surface area of the section of the tendons increased between 5 and 15 days followed by a stabilization. After 30 days, sections in both groups were similar. Thus, the constraint was similar after 5 and 15 days but was better for VEGF111 group after one month. Discussion - Conclusion: This experimentation has shown that a 100ng injection of VEGF-111 stimulated tendon healing process as suggested by the increased force needed to break tendons during its healing process and the increased of constraint in comparison with the control group. Other experimentations with different concentration of VEGF111 are now in process. Acknowledgement : This experimentation was partially financed by “Standard de Liège 2007” and “Lejeune-Lechien 2008” grants. [less ▲]

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See detailIntrinsic modification of tendon structure after concentric or excentric training
Kaux, Jean-François ULg; Drion, Pierre ULg; Besançon, Benoît et al

Poster (2010, November 25)

Introduction: It is well known that eccentric training is a successful way of treating chronic tendinopathy. Although clinical results are very positive, beneficial morphological and histological effects ... [more ▼]

Introduction: It is well known that eccentric training is a successful way of treating chronic tendinopathy. Although clinical results are very positive, beneficial morphological and histological effects have not yet been elucidated. The aim of our experiment was to determine if there exist any intrinsic modifications in a tendon trained in concentric or eccentric modes, in a rat model, using an original method of measurement (cryo-jaws). Methods: 18 rats were divided into 3 groups: 6 for the control group, without physical restraint; 12 for a training of1 hour, 3 times a week, for 5 weeks, at a speed of 17m/min (1km/h), on a inclined treadmill: 6 rats running uphill at +15° for the concentric effort (group C) and 6 rats running downhill at -15° for the eccentric effort (group E). After this training period, the Achilles, patellar and tricipital tendons of both limbs were surgically removed in all 18 rats. Tendons taken from five rats of each group were subjected to a tensile test up to rupture using a “cryo” jaw. Tendons of the remaining rat of each group were subjected to a histological study. Results: The results showed significant changes in group E only: (1) an increase of the force required to rupture the patellar and tricipital tendons; (2) an improvement of the ratio between the force necessary to rupture the tricipital tendon and the body mass of the rats; (3) an increase of the surface area of the section of the tricipital tendon. No significant change was observed as far as constraint was concerned between groups. Histologically, we saw, in the group E, more peripheral blood vessels and a greater proportion of collagen. Conclusion: This study showed that the mechanical properties of tendon tissue are enhanced by eccentric training. Tendons become stronger, the amount of collagen increases and there is probably more interaction between collagen fibers (mechanotransduction). [less ▲]

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See detailValorisation de la Carte des Sols dans un cadre inattendu - Le tourisme à caractère scientifique
Rekk, Samantha; Legrain, Xavier ULg; Bock, Laurent ULg et al

Poster (2010, November 24)

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See detailInfluence du type de sol et de son occupation sur la distribution des éléments traces métalliques entre les différents compartiments du sol : Stratégie et démarche d’échantillonnage
Lienard, Amandine ULg; Colinet, Gilles ULg

Poster (2010, November 24)

En Région wallonne, les sols contaminés en éléments traces métalliques (ETM) par retombées atmosphériques parsèment les anciennes régions industrielles du bassin sambro-mosan. C’est le cas du paysage ... [more ▼]

En Région wallonne, les sols contaminés en éléments traces métalliques (ETM) par retombées atmosphériques parsèment les anciennes régions industrielles du bassin sambro-mosan. C’est le cas du paysage entourant la réserve de Sclaigneaux (commune d’Andenne) connue pour ses pelouses calaminaires. Celles-ci trouvent leur origine dans les retombées de poussières contaminées provenant des cheminées d’évacuation d’une usine de zinc et plomb durant plus d’un siècle (1856 à 1978). Les cheminées, situées au sommet de la falaise sur la rive gauche de la Meuse, ont été détruites en 1982. Par cette étude, nous souhaitons observer la distribution des ETM dans les différents compartiments du sol et l’influence sur celle-ci du type de sol et de l’occupation du sol. La zone d’étude choisie est une maille circulaire de 3km de rayon centrée sur la zone des cheminées d’évacuation. Ce choix de maille permettra d’étudier l’offre en ETM du sol sur une distance constante dans toutes les directions. Elle est située dans le bassin hydrographique de la Meuse entre la Hesbaye, au nord, et le Condroz, au sud. Un plan d’échantillonnage stratifié par ordre d’importance des facteurs a été mis en place. Tout d’abord, une première sélection de sols a été opérée parmi les principaux types de sols répartis sur la zone sur base de l’ensemble de leur couverture cartographique. Les sols non cartographiés ou artificiels ainsi que les regroupements de complexes de sols pour lesquels les informations en notre possession sont insuffisantes ont ainsi été abandonnés. Une deuxième sélection porte sur les occupations de sols suivantes, cultures - prairies – forêts ; seuls six sols types de sols sont présents sous les trois occupations. Enfin, le choix final se porte sur les sols présents dans les quatre directions suivantes nord, est, ouest et sud. Au final, seulement trois unités de sols satisfont les exigences décrites ci-dessus. Les lieux d’échantillonnage sont répartis pour chaque combinaison sol-occupation sur les quatre directions. En tout, plus de 250 sondages seront réalisés sur cette zone d’environ 2.800ha pour optimiser la représentativité de l’échantillonnage. [less ▲]

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See detailMéthodologie d’acquisition d’une collection d’échantillons de sols liés aux matériaux parentaux en Wallonie
Legrain, Xavier ULg; Renneson, Malorie ULg; Genot, Valérie ULg et al

Poster (2010, November 24)

Malgré l'exiguïté de son territoire, la Wallonie est dotée d’un contexte géologique particulièrement varié et contrasté. Des grandes géostructures aux formations lithostratigraphiques, cette diversité se ... [more ▼]

Malgré l'exiguïté de son territoire, la Wallonie est dotée d’un contexte géologique particulièrement varié et contrasté. Des grandes géostructures aux formations lithostratigraphiques, cette diversité se reflète au niveau des situations pédologiques rencontrées. En effet, l’altération des roches, à l’origine du matériau parental, constitue un des processus majeurs indispensables à la formation d’un sol. Par ailleurs, à travers sa nature et sa composition, ce matériau d’origine est reconnu comme un des facteurs prépondérants influençant la pédogenèse, et de ce fait, les propriétés des sols. Fort de ce constat, l’Unité de Science du Sol de Gembloux Agro-Bio Tech, à travers la collaboration de divers projets, a entrepris la collecte d’échantillons de sols, en relation avec les matériaux parentaux à l’origine de la majorité des sols présents en Wallonie. L’objectif poursuivi est (i) d’acquérir des données à caractère « permanent », intrinsèques à ces matériaux parentaux, afin d’en dégager une signature chimique, physico-chimique, physique et spectrale, et (ii) de mettre en évidence l’influence tant du matériau parental que de l’occupation du sol sur les propriétés des horizons de surface. L’originalité du travail réside en partie dans la stratégie d’échantillonnage, basée sur une stratification pédologique et géographique, par la prise en compte respectivement de la Carte des Principaux Types de Sols de Wallonie et des Unités de l’Espace Rural. Les choix opérés ont conduit à la sélection de 12 matériaux parentaux, chacun faisant l’objet de prélèvements en 10 points (surface et profondeur). La localisation précise de ces points a été déterminée sur base d’une analyse et de la confrontation de documents cartographiques existants, se rapportant essentiellement aux sigles pédologiques, aux formations lithostratigraphiques, au relief et à l’occupation des sols. Un total de 258 échantillons a ainsi été prélevé en 120 points (76 en culture, 15 en prairie temporaire et 29 en prairie permanente). Parmi les analyses déjà réalisées citons, outre le menu d’analyse classique en pédologie (pH H2O et KCl, carbonates, granulométrie, COT, CEC, …), la détermination des formes du phosphore (total, minéral, organique ou disponible), des teneurs totales en éléments traces métalliques, la mesure de paramètres physiques ou hydriques tels que les limites d’Atterberg ou les courbes pF, ainsi que diverses analyses par spectroscopie proche infrarouge. Parmi les mesures envisagées à l’avenir, citons des analyses minéralogiques et des mesures de stabilité structurale. [less ▲]

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See detailEvaluation des risques de compaction des sols en Région wallonne
Rosiere, Charlotte ULg; Verbrugge, Jean-Claude; Destain, Marie-France ULg

Poster (2010, November 24)

Le projet de directive européenne COM(2006)232 établit un cadre général pour la protection des sols. Le projet prévoit que les états membres identifient les zones susceptibles d’être touchées par des ... [more ▼]

Le projet de directive européenne COM(2006)232 établit un cadre général pour la protection des sols. Le projet prévoit que les états membres identifient les zones susceptibles d’être touchées par des processus de dégradation (érosion, compaction, salinisation, …) et qu’ils proposent des mesures afin de réduire les risques. La compaction peut affecter la macroporosité, les mouvements de l’eau et de l’air dans le sol, les mécanismes de croissance racinaire, le développement de la faune du sol. De ce fait, elle est donc souvent à l’origine d’une diminution du rendement des cultures. En Région wallonne, les machines destinées à la récolte de betteraves risquent d’engendrer une compaction du sol car elles sont souvent utilisées alors que le sol est humide et que les charges à l’essieu sont importantes. Les machines d’exploitation forestière présentent également des risques pour la compaction du sol. La contrainte de préconsolidation (Pc) est considérée comme la valeur à ne pas dépasser pour éviter que le sol subisse des dégâts difficilement réversibles. Si les contraintes appliquées sont supérieures à Pc, le sol garde un comportement élastique (état réversible) et il n’y a pas de modification dans l’organisation de la porosité du sol. Par contre, si les contraintes appliquées sont supérieures à Pc, le sol entre en plasticité et ses fonctions naturelles sont perturbées. Dans un premier temps, des cartes de sensibilité du sol à la compaction sont élaborées. Elles évaluent la contrainte de préconsolidation des sols de la Région wallonne, au moyen des fonctions de pédotransfert (FPT) de Lebert et Fleige (2003). L’impact des engins sur le sol est étudié au niveau du ‘subsoil’, sous la couche de labour, là où le sol ne peut pas être régénéré par des outils classiques de travail du sol. Les paramètres des FPT sont accessibles au sein de Aardewerk ou sont trouvés dans la littérature. Les valeurs de Pc sont classées selon 6 niveaux de sensibilité, à deux états hydriques différents. Dans un deuxième temps, la distribution des contraintes verticales générées par le passage d’engins ‘types’, caractérisés par les dimensions des pneus, la charge à l’essieu et la pression de gonflage, est calculée à l’aide du logiciel Soilflex. Les Pc du sol sont alors comparées aux contraintes verticales induites par les engins, pour aboutir à des cartes de risque de compaction. Celles-ci simulent 4 scénarios : deux teneurs en eau et deux types d’engins. Afin de valider ces deux types de cartes, des tests oedométriques destinés à mesurer Pc sont réalisés sur des sols agricoles et forestiers. Pour faciliter la démarche et calculer les FPT de Lebert et Fleige avec une plus faible incertitude, il serait utile que la CNSW comporte des données relatives aux fractions granulométriques, à la matière organique des sols, la cohésion, l’angle de frottement interne, la masse volumique apparente sèche de sol, … [less ▲]

Detailed reference viewed: 127 (33 ULg)
Peer Reviewed
See detailSensitivity of simulated surface wetness duration to meteorological variations in three different regions of Grand-Duchy of Luxembourg
Mahtour, Abdeslam ULg; El Jarroudi, Moussa ULg; Hoffmann, Lucien et al

Poster (2010, November 23)

Surface wetness duration (SWD) is an important factor influencing the occurrence of winter wheat diseases. For this reason, SWD is extremely important for the management of crop protection activities. In ... [more ▼]

Surface wetness duration (SWD) is an important factor influencing the occurrence of winter wheat diseases. For this reason, SWD is extremely important for the management of crop protection activities. In order to understand the SWD variability and its influence on winter wheat disease, the objective of this study was to (i) determine the sensitivity of our model on varying input plant parameters and (ii) to evaluate the influence of simulated SWD to meteorological variations in three different climatic regions of the Grand-Duchy of Luxembourg (EVERLANGE, OBERCORN and SCHIMPACH). In this work, an agrometeorological model known as the Surface Wetness Energy Balance (SWEB) was applied for the simulation of SWD. The model was previously applied in another study for winter wheat cultivars and was adapted for use with agrometeorological data easily available from standard meteorological monitoring stations. Based on weather data and simulated SWD data, sensitivity analyses were performed to compare the effects of relative humidity, air temperature, wind speed and net radiation on wetness duration over one growing season (March-July) at three test sites. The results indicated that the sensitivities were very similar at three sites and there was no spatial trend (i.e. difference between locations) in the sensitivities. However, the model is most sensitive to relative humidity and differences between 0.5 and 25 h (per month) SWD were found when increasing/decreasing relative humidity by 10%. The model was least sensitive to changes in air temperature, showing differences of only 0.5–2 h (per month) in SWD. Intermediate sensitivity is found for rainfall, net radiation and wind speed. Among the input plant parameters values, SWD was most sensitive to the maximum fraction of canopy allowed as wet surface area, leaf area index, maximum water storage per unit area and least sensitive to crop height. The sensitivity to parameter values was less important compared to the sensitivity to the meteorological variable relative humidity. [less ▲]

Detailed reference viewed: 66 (16 ULg)
Peer Reviewed
See detailSensitivity of simulated surface wetness duration to meteorological variations in three different regions of the Grand-Duchy of Luxembourg
Mahtour, Abdeslam; El Jarroudi, Moussa ULg; Hoffmann, Lucien et al

Poster (2010, November 22)

Detailed reference viewed: 15 (2 ULg)
Full Text
See detailA fountain of droplets
Terwagne, Denis ULg; Delon, Giles ULg; Adami, Nicolas ULg et al

Poster (2010, November 21)

A vessel is plunged upside down into a pool of 50 cSt silicone oil. An air bell is then created. This bell is vertically shaken at 60 Hz that leads to the oscillation of the air/oil interface. The edges ... [more ▼]

A vessel is plunged upside down into a pool of 50 cSt silicone oil. An air bell is then created. This bell is vertically shaken at 60 Hz that leads to the oscillation of the air/oil interface. The edges of the immersed vessel generate surface waves that propagate towards the center of the bell. When the amplitude of the oscillation increases, wave amplitude increases. We study the influence of the angle between successive sides on the wave patterns. Two kinds of vessel have been studied: a triangular and a square prism. The shape of the air/oil meniscus depends on the angle between the sides of the considered prism. As the amplitude of the oscillation is increased, the triple line, which is the contact line between the solid and the air/oil interface, moves up and down. Above a given acceleration that depends on the immersion depth and on the shape vessel, wave goes under the corner edge of the bell. During the oscillation, the wave generates at the edges presents a singularity that leads eventually to a jet and a drop ejection. A drop is ejected at each oscillation. More complicated ejection can be produced with further increase of the amplitude. This is a sample arXiv article illustrating the use of fluid dynamics videos. [less ▲]

Detailed reference viewed: 36 (5 ULg)
Full Text
See detailFrozen Splash
Delon, Giles ULg; Terwagne, Denis ULg; Adami, Nicolas ULg et al

Poster (2010, November 21)

We have studied the splashing dynamics of water drops impacting granular layers. Depending on the drop kinetic energy, various shapes are observed for the resulting craters. Experimental parameters that ... [more ▼]

We have studied the splashing dynamics of water drops impacting granular layers. Depending on the drop kinetic energy, various shapes are observed for the resulting craters. Experimental parameters that have been considered are : the size of the millimetric droplets ; the height of the free fall, ranging from 1.5 cm to 100 cm ; and, the diam- eter of the grain. As the drop is impacting the sand layer, energy is dissipated and a splash of sand occurs. Meanwhile, surface tension, in- ertia and viscosity compete, leading to strong deformations of the drop which depend on the experimental conditions. Just after the drop en- ters into contact with the sand, imbibition takes place and increases the apparent viscosity of the fluid. The drop motion is stopped by this phenomenon. Images and fast-video recordings of the impact allowed to find scaling laws for the crater morphology and size. <br />This abstract is related to a fluid dynamics video for the APS DFD gallery of fluid motion 2010. [less ▲]

Detailed reference viewed: 61 (21 ULg)