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See detailPlaidoyer pour une prospective pour le futur de la grande faune africaine
Vermeulen, Cédric ULg

Scientific conference (2014, October 20)

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See detailInfluence of Morphine on the Rabbit Gastrointestinal Tract
Deflers, Hélène ULg; Bolen, Géraldine ULg; Gandar, Frederic ULg et al

Conference (2014, October 20)

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See detailLa famille isiaque en bords de Vesdre
Winand, Jean ULg

Scientific conference (2014, October 20)

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See detail« Maladie d’Alzheimer : après la retraite?»
Grotz, Catherine ULg

Conference given outside the academic context (2014)

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See detailAnalysis of the interactions of natural elicitor rhamnolipids with plant plasma membranes by in silico methods
Polo Lozano, Damien ULg; Nasir, Mehmet Nail ULg; Deleu, Magali ULg et al

Poster (2014, October 20)

Rhamnolipids are surface active molecules produced mainly by various strains of the bacterium Pseudomonas aeruginosa. These secondary metabolites are composed of one to three fatty acids with various ... [more ▼]

Rhamnolipids are surface active molecules produced mainly by various strains of the bacterium Pseudomonas aeruginosa. These secondary metabolites are composed of one to three fatty acids with various chain lengths linked through a glycosidic bond to one or two rhamnose moieties. The fatty acids are linked together through an ester bond. These molecules have shown several biological activities including plant defense stimulation. It has be suggested that this elicitor activity could be related to an interaction of rhamnolipids with the lipid bilayer of the plant plasma membrane (PPM) and lead to its destabilization, which can activate the plant defense signaling pathways. In this context, interactions of two rhamnolipids (Rha-C10-C10 and Rha-Rha-C10-C10) with membrane models and lipidic constituents of the PPM were investigated using in silico approaches. Most probable chemical structures of the rhamnolipids were determined using the STRUCTURE TREE procedure according to the molecule potential energy. The ability of these rhamnolipid structures to insert within the PPM was assessed using IMPALA simulations. IMPALA uses a membrane model in which phospholipids molecules are implicitly modeled by an empirical function and the membrane properties are modeled by energetic restraints. The ability of each rhamnolipid structure to form an assembly with several PPM constituents (phospholipid (PLPC), sterols (Sitosterol, Stigmasterol, Campesterol) and sphingolipids (GIPC, Glucosylceramide)) was calculated using the HYPERMATRIX procedure, which calculate and minimize the energies of interaction between all molecules of the complex until the lowest energy structure is reached. [less ▲]

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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.

Detailed reference viewed: 24 (6 ULg)
See detail120 ans d'enquête dialectologique en Belgique romane
Baiwir, Esther ULg

Scientific conference (2014, October 20)

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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 detailCharacterization of collagen fibrils after equine suspensory ligament injury: an ultrastructural and biochemical approach
Shikh Al Sook, Mohamad Khir ULg; Gabriel, Annick ULg; Salouci, Moustafa et al

Poster (2014, October 19)

Suspensory ligament (SL) injuries are an important cause of lameness in horses. The mechanical properties of connective tissue in normal and pathological ligaments are mainly related to the fibril ... [more ▼]

Suspensory ligament (SL) injuries are an important cause of lameness in horses. The mechanical properties of connective tissue in normal and pathological ligaments are mainly related to the fibril morphology, as well as the collagen content and types. The purpose of this study was to evaluate, using biochemical and ultrastructural approaches, the alterations in collagen fibrils after injury. Eight Warmblood horses with visible signs of injury in only one forelimb SL were selected and specimens were examined by transmission electron microscope (TEM). Collagen types I, III and V were purified by differential salt precipitation after collagen extraction with acetic acid containing pepsin. TEM revealed abnormal organization as well as alterations in the diameter and shape of fibrils after SL injury. The bands corresponding to types I, III and V collagen were assessed by densitometry after sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Densitometric analysis indicated that the proportions of type III and type V collagen were significantly higher (P <0.001) in damaged tissues compared to normal tissues with a mean increase of 20.9 and 17.3% respectively. Concurrently, a significant decrease (P <0.001) in type I collagen within damaged tissues was recorded with a mean decrease of 15.2%. These alterations could be the hallmark of a decrease in the tissue quality and mechanical properties of the ligament. This provides new insight for subsequent research on tissue regeneration that may lead to the development of future treatment strategies for SL injury. [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 ▲]

Detailed reference viewed: 6 (1 ULg)