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See detailDesign optimization of Rankine cycle systems for waste heat recovery from passenger car engines
Lemort, Vincent ULg; Legros, Arnaud; Dumont, Olivier ULg et al

Conference (2017, February 07)

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See detailHow to extract the oscillating components of a signal? A wavelet-based approach compared to the Empirical Mode Decomposition
Deliège, Adrien ULg

Scientific conference (2017, February 07)

Researchers are often confronted with time series that display pseudo-periodic tendencies with time-varying amplitudes and frequencies. In that framework, a classic Fourier analysis of the data may be of ... [more ▼]

Researchers are often confronted with time series that display pseudo-periodic tendencies with time-varying amplitudes and frequencies. In that framework, a classic Fourier analysis of the data may be of limited interest, especially if the objective is to derive components from the signal that capture the non-stationary behaviour of the oscillating factors. In this talk, we present two powerful tools designed to extract amplitude modulated-frequency modulated (AM-FM) components from a given signal. The first one is the renowned Empirical Mode Decomposition (EMD); we explain the technique, its main benefits, limitations and major practical uses. Then, we introduce the continuous wavelet transform and the equations that justify its relevance in the present context. We propose an algorithm based on the wavelet-induced time-frequency representation of a signal to extract its main components. The performances of this method are compared with the EMD on various AM-FM signals exhibiting different particularities. After briefly broaching the problem of edge effects, we investigate whether the wavelet-based procedure can be used in the domain of time series forecasting. For that purpose, we study the El Nino Southern Oscillation index and develop a model aimed at predicting the long-term trends of the signal. Its predictive skills are tested in several ways and exposed in the final part of the talk. [less ▲]

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See detailComparison of two laboratory-scale ensiling methods to assess effect of reducing sugars
Herremans, Sophie ULg; Decruyenaere, Virginie; Beckers, Yves ULg et al

Poster (2017, February 07)

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See detailThe prosumers and the grid
Gautier, Axel ULg; Jacqmin, Julien ULg; poudou, jean-christophe

Conference (2017, February 07)

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See detailLe jeu vidéo à l'université? Recherches sur un objet culturel
Dozo, Björn-Olav ULg

Conference given outside the academic context (2017)

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See detailQuantification of natural estrogens in aqueous matrices as pyridine-3-sulfonyl derivatives by UHPLC-ESI-MS/MS
Glineur, Alex ULg; Ronkart, Sébastien; Nott, Kathérine et al

Conference (2017, February 07)

Natural estrogens (estrone: E1, 17-β-estradiol : E2, estriol : E3) and synthetic estrogen (17-α-ethinylestradiol: EE2) are powerful endocrine disruptors. They may have deleterious effects on aquatic ... [more ▼]

Natural estrogens (estrone: E1, 17-β-estradiol : E2, estriol : E3) and synthetic estrogen (17-α-ethinylestradiol: EE2) are powerful endocrine disruptors. They may have deleterious effects on aquatic wildlife and also humans even at extremely low concentrations. For this reason, these molecules have been included in a watch list from the European Commission regarding emerging aquatic pollutants. The maximum detection limits are set at 0.035 and 0.40 ng/L for EE2 and E1, E2 respectively. Reaching such low levels of concentration of estrogenic compounds is a challenge, even using state-of-the-art analytical methods. In this study, we developed a UHPLC-ESI-MS/MS method allowing the quantification of E1, E2, E3 and EE2 residues in aqueous matrices. Studies commonly used ESI in negative mode albeit the poor ionization efficiency of native estrogenic compounds in this mode. In this study, the molecules were derivatised using a sulfonyl chloride reagent (pyridine-3-sulfonyl, P-3-S). The resulting response in the positive mode was significantly enhanced. Similarly to other dansyl derivatives, the product ion spectra of the P-3-S derivatives indicate ions originating from the derivatization reagent moiety. Moreover, several other ions were included in the product ion spectra of the P-3-S derivatives. Their specificity was assessed by a qualitative approach implying the analysis of different types of water samples (groundwater, surface water). Some product ions were found to be noticeably better for quantification and confirmation of the analytes. The developed analytical method was validated according to the NF T90-210 norm which is suitable to assess the performances of a method in the water quality field. The limits of quantification were 0.04, 0.05, 0.10 and 0.02 ng/L in groundwater and 0.89, 0.79,4.42 and 0.29 ng/L in surface water for E1, E2, E3 and EE2 respectively. [less ▲]

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See detailLogging impact on biodiversity in Central Africa
Doucet, Jean-Louis ULg

Conference (2017, February 07)

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See detailPerineuronal nets and vocal plasticity in songbirds: a proposed mechanism to explain the difference between closed-ended and open-ended learning
Cornez, Gilles ULg; Madison, F.N.; Van der Linden, A. et al

in Developmental Neurobiology (2017)

Perineuronal nets (PNN) are aggregations of chondroitin sulfate proteoglycans surrounding the soma and proximal processes of neurons, mostly GABAergic interneurons expressing parvalbumin. They limit the ... [more ▼]

Perineuronal nets (PNN) are aggregations of chondroitin sulfate proteoglycans surrounding the soma and proximal processes of neurons, mostly GABAergic interneurons expressing parvalbumin. They limit the plasticity of their afferent synaptic connections. In zebra finches PNN develop in an experience-dependent manner in the song control nuclei HVC and RA (nucleus robustus arcopallialis) when young birds crystallize their song. Because songbird species that are open-ended learners tend to recapitulate each year the different phases of song learning until their song crystallizes at the beginning of the breeding season, we tested whether seasonal changes in PNN expression would be found in the song control nuclei of a seasonally breeding species such as the European starling. Only minimal changes in PNN densities and total number of cells surrounded by PNN were detected. However, comparison of the density of PNN and of PNN surrounding parvalbumin-positive cells revealed that these structures are far less numerous in starlings that show extensive adult vocal plasticity, including learning of new songs throughout the year, than in the closed-ended learner zebra finches. Canaries that also display some vocal plasticity across season but were never formally shown to learn new songs in adulthood were intermediate in this respect. Together these data suggest that establishment of PNN around parvalbumin-positive neurons in song control nuclei has diverged during evolution to control the different learning capacities observed in songbird species. This differential expression of PNN in different songbird species could represent a key cellular mechanism mediating species variation between closed-ended and open-ended learning strategies. [less ▲]

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See detailInteractive family dynamics and Non-Suicidal Self-Injury in psychiatric adolescent patients: a single case study
Gatta, Michela; Miscioscia, Marina ULg; Sisti, Marta et al

in Frontiers in Psychology (2017), 8(46),

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See detailVieillir avec ou sans maladie d'Alzheimer dans notre société actuelle
Adam, Stéphane ULg

Conference given outside the academic context (2017)

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See detailAERODYNAMIC AND AEROELASTIC MODELING OF HORIZONTAL AXIS WIND TURBINES USING PANEL METHODS
Prasad, Chandra Shekhar ULg

Doctoral thesis (2017)

Wind energy is one of the most reliable renewable energy sources and constitutes a viable alternative to fossil and nuclear fuels for the generation of electricity. Over the last couple of decades the ... [more ▼]

Wind energy is one of the most reliable renewable energy sources and constitutes a viable alternative to fossil and nuclear fuels for the generation of electricity. Over the last couple of decades the increasing demand for wind energy has resulted in increasingly large and sophisticated wind turbines. Accurate but efficient aerodynamic and aeroelastic modelling at the design stage has become a key issue. The surface panel and vortex lattice methods are efficient aerodynamic modelling tools that are routinely employed in design calculations by the aerospace industry. They constitute a good compromise between fidelity and computational cost in the preliminary design and optimization phase. However, these approaches have not been widely adopted for wind turbine modelling due to their inability to represent separated flow. The main objective of this thesis is the development of a 3D unsteady viscous-inviscid interaction technique that couples panel methods to a boundary layer solution and can be used to model separated flow over the blades of a wind turbine rotor. The technique is based on a quasi-3D, quasi-steady integral boundary layer solution, coupled to a 3D unsteady surface panel method by means of a two-way interaction scheme. The boundary layer solution results in an estimate of the separation line on the suction surface of the blade. A separated shear layer made up of doublet panels is shed from this line and allowed to propagate freely at the local flow velocity, exactly like the wake shed at the trailing edge. Aerodynamic pressure and load predictions obtained from this method are validated through comparison to experimental measurements from the NREL phase VI wind turbine. The thesis also describes the development of a complete methodology for the unsteady aeroelastic and aeroservoelastic modeling of horizontal axis wind turbines at the design stage. The methodology is based on the implementation of unsteady aerodynamic modeling, advanced control strategies and nonlinear finite element calculations in the Siemens LMS Samcef for Wind Turbines design package. The aerodynamic modelling is carried out by means of the unsteady Vortex Lattice Method. The complete methodology is used to perform full aeroservoelastic simulations of a 2MW prototype wind turbine model. [less ▲]

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See detailNumerical study of Balearic meteotsunami generation and propagation under synthetic gravity wave forcing
Matjaž, Ličer; Mourre, Baptiste; Troupin, Charles ULg et al

in Ocean Modelling (2017), 111

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See detailCrystal structure and biochemical characterization of the transmembrane PAP2 type phosphatidylglycerol phosphate phosphatase from Bacillus subtilis.
El Ghachi, Meriem ULg; Howe, Nicole; Auger, Rodolphe et al

in Cellular and Molecular Life Sciences : CMLS (2017)

Type 2 phosphatidic acid phosphatases (PAP2s) can be either soluble or integral membrane enzymes. In bacteria, integral membrane PAP2s play major roles in the metabolisms of glycerophospholipids ... [more ▼]

Type 2 phosphatidic acid phosphatases (PAP2s) can be either soluble or integral membrane enzymes. In bacteria, integral membrane PAP2s play major roles in the metabolisms of glycerophospholipids, undecaprenyl-phosphate (C55-P) lipid carrier and lipopolysaccharides. By in vivo functional experiments and biochemical characterization we show that the membrane PAP2 coded by the Bacillus subtilis yodM gene is the principal phosphatidylglycerol phosphate (PGP) phosphatase of B. subtilis. We also confirm that this enzyme, renamed bsPgpB, has a weaker activity on C55-PP. Moreover, we solved the crystal structure of bsPgpB at 2.25 A resolution, with tungstate (a phosphate analog) in the active site. The structure reveals two lipid chains in the active site vicinity, allowing for PGP substrate modeling and molecular dynamic simulation. Site-directed mutagenesis confirmed the residues important for substrate specificity, providing a basis for predicting the lipids preferentially dephosphorylated by membrane PAP2s. [less ▲]

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See detailHydraulic and wood traits of two congeneric tropical tree species in their core habitat
Gorel, Anaïs ULg; Steppe, kathy; Beeckman, Hans et al

Conference (2017, February 06)

Background: Strong niche partitioning across rainfall gradients has been identified for several tropical tree genera. The link between hydraulic and wood anatomical traits, associated with drought ... [more ▼]

Background: Strong niche partitioning across rainfall gradients has been identified for several tropical tree genera. The link between hydraulic and wood anatomical traits, associated with drought tolerance, however remains to be explored, in order to identify the mechanisms shaping the range limits of tropical tree species. Aim: In this study, we aimed to identify the differences in hydraulic and wood traits between two congeneric tree species with contrasting distributions in moist and wet tropical forests. Location: Central African moist and wet forests Methods: In the core habitat of Erythrophleum ivorense (wet forest) and of E. suaveolens (moist), we collected branches to construct vulnerability curves and measure hydraulic capacitance, and both stem and branch wood samples to link the hydraulic traits to wood anatomy. Major results: E. suaveolens, which is characteristic of drier forests, is clearly more resistant to cavitation than E. ivorense, and also possess a greater hydraulic capacitance (i.e. the capacity that species have to mitigate periods of water storage by using internally stored water). In agreement with this great drought tolerance for E. suaveolens, wood anatomy revealed a high number of small vessels associated with small intervessel pits, features minimizing cavitation risk but also reducing water transport. Main conclusions: Drought tolerance, as indicated by both hydraulic and wood traits, strongly differed between the closely related species and explained their contrasting distribution, and affinity for moist (E. ivorense) and wet (E. suaveolens) forests. However, phenotypic plasticity in hydraulic and wood traits remained to be addressed to examine the extent of water use differences between the two species. [less ▲]

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See detailVLT/SPHERE robust astrometry of the HR8799 planets at milliarcsecond-level accuracy. Orbital architecture analysis with PyAstrOFit
Wertz, Olivier; Absil, Olivier ULg; Gómez González, Carlos ULg et al

in Astronomy and Astrophysics (2017), 598

HR8799 is orbited by at least four giant planets, making it a prime target for the recently commissioned Spectro-Polarimetric High-contrast Exoplanet REsearch (VLT/SPHERE). As such, it was observed on ... [more ▼]

HR8799 is orbited by at least four giant planets, making it a prime target for the recently commissioned Spectro-Polarimetric High-contrast Exoplanet REsearch (VLT/SPHERE). As such, it was observed on five consecutive nights during the SPHERE science verification in December 2014. We aim to take full advantage of the SPHERE capabilities to derive accurate astrometric measurements based on H-band images acquired with the Infra-Red Dual-band Imaging and Spectroscopy (IRDIS) subsystem, and to explore the ultimate astrometric performance of SPHERE in this observing mode. We also aim to present a detailed analysis of the orbital parameters for the four planets. We report the astrometric positions for epoch 2014.93 with an accuracy down to 2.0 mas, mainly limited by the astrometric calibration of IRDIS. For each planet, we derive the posterior probability density functions for the six Keplerian elements and identify sets of highly probable orbits. For planet d, there is clear evidence for nonzero eccentricity ($e \simeq 0.35$), without completely excluding solutions with smaller eccentricities. The three other planets are consistent with circular orbits, although their probability distributions spread beyond $e = 0.2$, and show a peak at $e \simeq 0.1$ for planet e. The four planets have consistent inclinations of about $30\deg$ with respect to the sky plane, but the confidence intervals for the longitude of ascending node are disjoint for planets b and c, and we find tentative evidence for non-coplanarity between planets b and c at the $2 \sigma$ level. [less ▲]

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See detail"Il vaut mieux prévenir que guérir", l'adage s'applique également aux plantes
Massart, Sébastien ULg

Article for general public (2017)

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See detailHow tree architecture varies across coexisting tropical tree species and relates to functional traits?
Loubota Panzou, Grâce Jopaul ULg; Ligot, Gauthier ULg; Loumeto, Jean-Joël et al

Conference (2017, February 06)

Architecture refers to the overall shape of a tree and the spatial position of its components. Tree height determines the position in the forest canopy and access to light, while the amount and spatial ... [more ▼]

Architecture refers to the overall shape of a tree and the spatial position of its components. Tree height determines the position in the forest canopy and access to light, while the amount and spatial distribution of the foliage depend on the depth and the width of the crown. The aim of this study is to understand how tree architecture varies across coexisting tropical tree species and relates to functional traits. Forty five coexisting tree species were sampled in the semi-deciduous forests of Northern Congo. Species were classified according to ecological strategies, specifically regeneration guilds: shade bearers (27 species), non-pioneers light demanding (14 species) and pioneers (4 species). For each species, 14–72 trees (968 trees in total) were measured over a large range of diameter (10–162 cm). At the tree level, we measured the diameter (D in cm), height (H in m), crown radius (Cr in m) and crown depth (Cd in m) and crown exposure index (CEI) was visually estimated. At species level, architectural traits (Dmax, Hmax, Crmax and Cdmax), life history traits (dispersal mode, phenology and guild) and functional traits (wood density and light requirement) were obtained. We investigates the H-D, Cr-D and Cd-D allometric relationships at the tree level using linear mixed models on log-transformed data with species as a random effect on both slope and intercept. We used the multivariate analysis to quantify the relationship between architectural, functional traits and life history traits. Based on AIC, we found that the best linear mixed model was the one with two species random parameters (intercept and slope) for H-D and Cr-D allometries, while the best model for Cd-D allometry was the one with only a random intercept. Thus, our results showed a significant variation in tree allometry between coexisting species. The interspecific variation in H-D allometry was related to light requirement while Cr-D and Cd-D allometries were more related to dispersal mode and wood density, respectively. The confirmed the existence of three ecological strategies (shade bearers, non-pioneers light demanding and pioneers) in tropical forests, specifically in Central Africa. Architectural traits were the main traits that differentiate between ecological strategies. Architectural traits are therefore strong predictors of ecological strategies of coexisting tropical tree species. [less ▲]

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See detailDroit parlementaire et électoral - Plan général du cours 2016-17
Bouhon, Frédéric ULg

Learning material (2017)

Ce document présente le plan général du cours de Droit parlementaire et électoral pour l'année 2016-17.

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See detailIntroduction au droit - Partim droit public - Plan général du cours 2016-17
Bouhon, Frédéric ULg

Learning material (2017)

Ce document présente le plan détaillé du partim droit public du cours d'Introduction au droit destiné aux étudiants de bachelier HEC-ULg. Il s'agit de la version 2016-17.

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