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See detailSensitivity of Greenland Ice Sheet surface mass balance to perturbations in sea surface temperature and sea ice cover: a study with the regional climate model MAR
Noel, Brice; Fettweis, Xavier ULg; van de Berg, W.J. et al

in Cryosphere (The) (2014), 8

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North ... [more ▼]

During recent summers (2007–2012), several surface melt records were broken over the Greenland Ice Sheet (GrIS). The extreme summer melt resulted in part from a persistent negative phase of the North Atlantic Oscillation (NAO), favoring warmer atmospheric conditions than normal over the GrIS. Simultaneously, large anomalies in sea ice cover (SIC) and sea surface temperature (SST) were observed in the North Atlantic, suggesting a possible connection. To assess the direct impact of 2007–2012 SIC and SST anomalies on GrIS surface mass balance (SMB), a set of sensitivity experiments was carried out with the regional climate model MAR forced by ERA-Interim. These simulations suggest that perturbations in SST and SIC in the seas surrounding Greenland do not considerably impact GrIS SMB, as a result of the katabatic wind blocking effect. These offshore-directed winds prevent oceanic near-surface air, influenced by SIC and SST anomalies, from penetrating far inland. Therefore, the ice sheet SMB response is restricted to coastal regions, where katabatic winds cease. A topic for further investigation is how anomalies in SIC and SST might have indirectly affected the surface melt by changing the general circulation in the North Atlantic region, hence favoring more frequent warm air advection towards the GrIS. [less ▲]

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See detailAdvances in the synthesis of degradable polymers for biomedical applications
Lecomte, Philippe ULg

Conference (2014, October 20)

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See detailInsights upon the adsorption mechanism of KAX on malachite
Kanda, Jean-Marie; Kongolo, Mukendi; Gaydardzhiev, Stoyan ULg et al

in Yianatos, Juan (Ed.) Proceedings of the XXVII International Mineral Processing Congress (2014, October 20)

The adsorption patterns of potassium amylxanthate on the surface of high purity malachite subjected to prior sulfidization with NaSH have been followed and elucidated. DRIFTS spectroscopy has been used to ... [more ▼]

The adsorption patterns of potassium amylxanthate on the surface of high purity malachite subjected to prior sulfidization with NaSH have been followed and elucidated. DRIFTS spectroscopy has been used to trace the associated physicochemical alterations as well as the chemical species present on the mineral surface. Varying the collector concentration from 5.10-4 to 1.10-2 mol/L has led to different degree of surface coverage of the alkyl groups in combination with formation of organometallic hydrophobic complexes of CuX and CuX – X2 type. The results reveal that the CuX complex formed on the malachite surface without sulfidizing agent is more unstable and prone to dissolution-precipitation phenomena. Based upon the constructed adsorption isotherms and upon the degree of statistical coverage, different zones of mineral-reagent interactions could be distinguished. They correspond respectively to the monolayer, bi-layer and tridimensional condensation domains. In each of the identified zones mono or double layer adsorption patterns of the collector are proposed leading respectively to formation of surface compounds with different degree of hydrophobicity. [less ▲]

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See detailPhysicochemical observations during process water reuse in flotation of oxide copper-cobalt ore
Shengo, Michel; Gaydardzhiev, Stoyan ULg; Kalenga, Pierre

in Yianatos, Juan (Ed.) Proceedings of the XXVII International Mineral Processing Congress (2014, October 20)

Lab-scale flotation of copper and cobalt oxidized ore from the Luiswishi deposit in the Katanga province (DRC) has been done focusing on the influence of the degree of process water recycling on metals ... [more ▼]

Lab-scale flotation of copper and cobalt oxidized ore from the Luiswishi deposit in the Katanga province (DRC) has been done focusing on the influence of the degree of process water recycling on metals recovery. Results have shown that at 20 % recycling rate, the recovery of copper and cobalt in the cleaner stage have been respectively reduced to 23 % and 45 % in comparison to 53 % Cu and 63 % Co if process water has not been recycled. At 10 % recycling rate however, the system could still tolerate the effect from recycling, since Cu and Co recovery has remained respectively at acceptable levels of 52 % and 60 %. In order to explain the reasons for the observed worsening of flotation results if process water was recycled at rate higher than 20 %, electrochemical investigation of the pulp has been performed. It has been established that the chemical compounds formed in the pulp when process water was recycled, do influence the sulfidization of malachite and heterogenite and impact further collector adsorption. To confirm these assumptions, the effect from thiosulphate ions presence during the sulfidization of high purity malachite has been studied. It has been found, that thiosulphate ions depending on their concentration in water induce variations in pulp properties such as DO content, pH, Es and contribute to formation of undesirable chemical compounds on mineral surface as identified by DRIFT spectroscopy. [less ▲]

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See detailArchitectures implicites, pouvoirs invisibles : le libertinage érudit
Decoster, Sara ULg

Conference (2014, October 20)

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See detailProbabilistic Assessment of Lifetime of Low-Earth-Orbit Spacecraft: Uncertainty Propagation and Sensitivity Analysis
Dell'Elce, Lamberto ULg; Kerschen, Gaëtan ULg

in Journal of Guidance Control & Dynamics (2014)

This paper is devoted to the probabilistic uncertainty quantification of orbital lifetime estimation of low-altitude satellites. Specifically, given a detailed characterization of the dominant sources of ... [more ▼]

This paper is devoted to the probabilistic uncertainty quantification of orbital lifetime estimation of low-altitude satellites. Specifically, given a detailed characterization of the dominant sources of uncertainty, we map this input into a probabilistic characterization of the orbital lifetime through orbital propagation. Standard Monte Carlo propagation is first considered. The concept of drag correction is then introduced to facilitate the use of polynomial chaos expansions and to make uncertainty propagation computationally effective. Finally, the obtained probabilistic model is exploited to carry out stochastic sensitivity analyses, which in turn allow gaining insight into the impact uncertainties have on orbital lifetime. The proposed developments are illustrated using one CubeSat of the QB50 constellation. [less ▲]

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See detailA Riemannian approach to large-scale constrained least-squares with symmetries
Mishra, Bamdev ULg

Doctoral thesis (2014)

This thesis deals with least-squares optimization on a manifold of equivalence relations, e.g., in the presence of symmetries which arise frequently in many applications. While least-squares cost ... [more ▼]

This thesis deals with least-squares optimization on a manifold of equivalence relations, e.g., in the presence of symmetries which arise frequently in many applications. While least-squares cost functions remain a popular way to model large-scale problems, the additional symmetry constraint should be interpreted as a way to make the modeling robust. Two fundamental examples are the matrix completion problem, a least-squares problem with rank constraints and the generalized eigenvalue problem, a least-squares problem with orthogonality constraints. The possible large-scale nature of these problems demands to exploit the problem structure as much as possible in order to design numerically efficient algorithms. The constrained least-squares problems are tackled in the framework of Riemannian optimization that has gained much popularity in recent years because of the special nature of orthogonality and rank constraints that have particular symmetries. Previous work on Riemannian optimization has mostly focused on the search space, exploiting the differential geometry of the constraint but disregarding the role of the cost function. We, on the other hand, propose to take both cost and constraints into account to propose a tailored Riemannian geometry. This is achieved by proposing novel Riemannian metrics. To this end, we show a basic connection between sequential quadratic programming and Riemannian gradient optimization and address the general question of selecting a metric in Riemannian optimization. We revisit quadratic optimization problems with orthogonality and rank constraints by generalizing various existing methods, like power, inverse and Rayleigh quotient iterations, and proposing novel ones that empirically compete with state-of-the-art algorithms. Overall, this thesis deals with exploiting two fundamental structures, least-squares and symmetry, in nonlinear optimization. [less ▲]

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See detailQuelles aides proposer aux victimes d’infractions ?
Garcet, Serge ULg

Article for general public (2014)

L'article propose un panorama de l'offre en matière d'aide aux victimes.

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See detailThe Airline Container Loading Problem with Pickup and Delivery
Lurkin, Virginie ULg; Schyns, Michael ULg

Conference (2014, October 19)

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at ... [more ▼]

The present paper looks into the problem of optimizing the loading of a set of containers and pallets into cargo aircraft serving multiple airports. Due to the pickup and delivery operations occurring at intermediate airports, this problem is simultaneously a weight and balance problem and a sequencing problem. Our objective is to minimize fuel and handling operations costs. This problem is shown to be NP-hard. We resort to a mixed integer linear program. On the basis of a professional partner's real-world data, TNT Airways, we perform numerical experiments using a standard B&C library. This approach yields better solutions than traditional manual planning, which results in substantial cost savings. [less ▲]

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See detailSeasonal variations of wild boar Sus scrofa distribution in agricultural landscapes: a species distribution modelling approach
Morelle, Kevin ULg; Lejeune, Philippe ULg

in European Journal of Wildlife Research (2014)

Seasonal changes in the distribution of animals can have an important impact on the ecosystem. In agricultural landscapes, the seasonal movement of the wild boar Sus scrofa towards field crops often ... [more ▼]

Seasonal changes in the distribution of animals can have an important impact on the ecosystem. In agricultural landscapes, the seasonal movement of the wild boar Sus scrofa towards field crops often results in damages and makes control of the population difficult. The plasticity of the species to cope with different habitats is largely proven, but the environmental and human drivers of this seasonal habitat shift at the population scale remain largely unknown. Using MaxEnt and two seasonally distinct presence datasets, we contrasted the distribution of wild boar in southern Belgium during the growing and hunting seasons to (i) analyse seasonal drivers of the distribution and (ii) forecast the potential spread of the species north to its current distribution. We demonstrated that during the growing season, wild boar range almost double, owing to the cover and food provided by agricultural areas, thereby enhancing the movement and spread of the species. We found that the seasonal distribution of wild boar in agricultural lands is mostly influenced by the search for cover and food provided alternatively by forest and field crops. Interestingly, it seems that this search for cover operates under the constraint of a threshold distance. Our results indeed reveal an increased probability of presence not only in the vicinity of forests but also above a threshold distance of 865 m from the forest edge, suggesting that wild boar can overcome the dependence to forest cover. The forecast distribution of wild boar highlighted a potential increase of the current range into suitable habitat between 63 and 168 km2. To counteract the potential spread of the species into agricultural habitats and the consecutive damages, we insist on the need for the development of integrated management strategies, combining land use spatial configuration and wild boar spatial behaviour. [less ▲]

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See detailRole of non-polyQ regions on the aggregation process by polyQ proteins into amyloid fibrils
Huynen, Céline ULg; Willet, Nicolas ULg; Buell, Alexander K et al

Poster (2014, October 18)

Nine neurodegenerative disorders, referred to as polyglutamine diseases and including Huntington’s disease, are associated with the abnormal expansion of a polyglutamine tract inside nine unrelated ... [more ▼]

Nine neurodegenerative disorders, referred to as polyglutamine diseases and including Huntington’s disease, are associated with the abnormal expansion of a polyglutamine tract inside nine unrelated proteins. This polyQ expansion is thought to be the major determinant in the development of neurotoxicity, triggering protein aggregation into amyloid fibrils. A large body of evidence however indicates that non-polyQ regions modulate the aggregation process triggered by polyQ expansions. The interplay between the polyQ tract and non-polyQ regions is complex and still not fully understood. In order to better understand it, we previously designed and characterized model polyQ proteins made of the beta-lactamase BlaP and a 23, 30, 55 or 79Q tract inserted in position 197 or 216. These chimeras recapitulate the aggregation properties of polyQ disease-associated proteins: there is a Q-threshold for the formation of amyloid fibrils, and above the threshold, the longer the polyQ, the faster the aggregation. Moreover, the structure of BlaP (native or unfolded) and the position of insertion of the polyQ tract (197 versus 216) influence their aggregation properties. In this work, (i) we discuss the role of the conformation of the host protein, BlaP, and of the location of the polyQ within BlaP on the different phases of amyloid fibril formation, the nucleation and elongation steps, using mainly quartz crystal microbalance (QCM), atomic force microscopy (AFM). Our results highlight a linear dependence of the polyQ length on the elongation rate whatever the insertion site and the conformation of BlaP. These two parameters however drastically influence the ability of a polyQ tract to trigger the nucleation and the elongation steps of amyloid fibril formation. (ii) Finally, we investigate the precise aggregation threshold and the modulating role of the N- and C-terminal polyQ flanking sequences in position 197 of BlaP by creating and characterizing new chimeras containing intermediate length polyQ tracts in position 197, or polyQ tracts inserted between two cleavage sites in position 197, respectively. We observe that the propensity to trigger the full process of amyloid fibril formation and its rate seems to be largely dependent on the polyQ length and on the polyQ flanking sequences. Altogether our results contribute to identify the important species and elements (polyQ or non-polyQ regions, monomers, oligomers or fibrils) during the aggregation process into amyloid fibrils to interfere with the latter associated with neurotoxicity. [less ▲]

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See detailDetermination of COBALT in patients with metal hip prosthesis
MISTRETTA, Virginie ULg; Charlier, Corinne ULg

Poster (2014, October 18)

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See detailA novel mutation of the luteinizing hormone/choionic gonadotrophin receptor gene leading to Leydig cell hypoplasia type I
Potorac, Iulia ULg; Rivero-Müller, Adolfo; Pintiaux, Axelle ULg et al

in Abstract book - 24th Meeting of the Belgian Endocrine Society (2014, October 18)

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See detailFamilial hypocalciuric hypercalcemia : a rare cause of recurrent pancreatitis
Daniel, Sara ULg; Potorac, Iulia ULg; MALAISE, Olivier ULg et al

in Abstract book - 24th Meeting of the Belgian Endocrine Society (2014, October 18)

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See detailCharacterization of paragangliomas : a single center cohort study
VROONEN, Laurent ULg; Maiga, Ibrahima ULg; PETROSSIANS, Patrick ULg et al

in Abstract book - 24th Meeting of the Belgian Endocrine Society (2014, October 18)

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See detailCase report : Rhabdomyolysis following acute alcohol intoxication
HALENG, Jeanine ULg; CAVALIER, Etienne ULg

Poster (2014, October 18)

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See detailLien entre représentation du vieillissement chez le personnel de MR/MRS et la qualité de vie de résidents déments: Intérêt de l’enquête FIH
Missotten, Pierre ULg

Conference (2014, October 17)

A l’heure actuelle, la vision prégnante du vieillissement est négative, teintée des phénomènes d’âgisme et de jeunisme. Cette vision est objectivée dans diverses enquêtes récentes (ex : l’Eurobaromètre ... [more ▼]

A l’heure actuelle, la vision prégnante du vieillissement est négative, teintée des phénomènes d’âgisme et de jeunisme. Cette vision est objectivée dans diverses enquêtes récentes (ex : l’Eurobaromètre des statistiques de discrimination en Europe) qui soulignent que le motif de discrimination le plus souvent cité en Europe est l’âge (correspondant ici au fait d’avoir plus de 55 ans ; 4 % en 2012, 6 % en 2009), suivi seulement par la race (3 %). Si la personne vieillissante est déjà stigmatisée en général, il n’est pas étonnant de constater que le fait d’être atteint d’une pathologie démentielle accroît encore ce phénomène : les individus souffrant de démence sont considérés comme faisant partie du groupe le plus marginalisé et stigmatisé dans la société (Graham et al., 2003). Les personnes qui en sont atteintes sont souvent perçues comme n’ayant plus une bonne qualité de vie (Qdv) ni la capacité d’éprouver du plaisir (Garand et al., 2009). En ce sens, ces personnes font donc l’objet d’une double stigmatisation (stigmatisation liée au fait d’être âgé et d’être atteint de démence). Sur base de ce constat, cette présentation s’axera sur les liens qui peuvent exister entre nos représentations du vieillissement (et de la démence) et le concept de Qdv. Tout d’abord, nous aborderons les résultats des recherches dans le vieillissement « normal ». A côté des études de Levy (cf. Levy, 2009 pour une synthèse) ayant démontré l’impact délétère d’une vision négative du vieillissement sur la santé mentale et physique des aînés, diverses études récentes (ex : Bodner et al., 2011) ont montré qu’une vision négative du vieillissement était liée à une moindre Qdv. Plus encore, le niveau de Qdv peut en partie s’expliquer par la vision du vieillissement (ex : Top et al., 2012). Ces constations nous amènent à nous questionner sur la situation dans le cadre des pathologies démentielles. A ce niveau, il s’avère nécessaire de recourir à une hétéro-évaluation de la Qdv pour toute personne souffrant d’une démence sévère. En ce sens, ce n’est pas le patient lui-même qui fournit des réponses mais un aidant (professionnel ou familial). Sur base de cet élément, nous avons mis au point un protocole de recherche destiné à évaluer la Qdv de personnes souffrant de pathologies démentielles vivant en MR ou MRS, en y incluant des mesures d’âgisme des aidants. Ce protocole a été élaboré dans le cadre d’une collaboration avec l’ASBL Fédération des Institutions Hospitalières (FIH). Nous faisons l’hypothèse que la perception d’une même réalité (un même patient est évalué sur base d’un même outil) c.à.d. la qualité de vie, serait en partie tributaire de la vision que chaque soignant a du vieillissement et de la démence. Dans le prolongement de la présentation de cette étude, nous aborderons le fait qu’avoir une vision négative du vieillissement et de la démence nous amène à avoir des attitudes différentes (souvent bienveillantes mais pas toujours positives) à l’égard des personnes âgées. Ces attitudes ont un impact délétère sur la santé mentale et physique des personnes âgées et donc aussi sur leur qualité de vie (ex : Mandelblatt et al., 2003). Ces conséquences de l’âgisme sont donc susceptibles de confirmer la vision négative véhiculée à l’égard des personnes âgées (ex. : les personnes âgées sont vulnérables, dépendantes et ont une mauvaise qualité de vie) et ainsi d’alimenter un cercle vicieux. Biblio 1. Eurobaromètre 57.0 - mai 2012 - http://europa.eu.int/comm/public_opinion/ 2. Graham et al., 2003 Int J Geriatr Psychiatry, 18(8), 670-678. 3. Garand et al. (2009). Res Gerontol Nurs, 2(2), 112-121. 4. Levi (2009). Curr Dir Psychol Sci; 18, 332-6 5. Bodner et al. (2011). Int Psychogeriatr,23(8),1197–1204 6. Top et al. (2012). Research on Aging, 35(5), 533-562 7. Mandelblatt et al. (2003). J Clin Oncol, 21, 855-863. [less ▲]

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