Last 7 days
Bookmark and Share    
Peer Reviewed
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 ▲]

Detailed reference viewed: 31 (10 ULg)
Full Text
See detailLogging impact on biodiversity in Central Africa
Doucet, Jean-Louis ULg

Conference (2017, February 07)

Detailed reference viewed: 22 (0 ULg)
Peer Reviewed
See detailPassive (re)translations and active power struggles in "Book of Longing" (Leonard Cohen)
Mus, Francis ULg

Conference (2017, February 07)

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 32 (8 ULg)
Full Text
Peer Reviewed
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),

Detailed reference viewed: 23 (0 ULg)
See detailVieillir avec ou sans maladie d'Alzheimer dans notre société actuelle
Adam, Stéphane ULg

Conference given outside the academic context (2017)

Detailed reference viewed: 32 (1 ULg)
Full Text
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 ▲]

Detailed reference viewed: 58 (10 ULg)
Full Text
Peer Reviewed
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

Detailed reference viewed: 14 (0 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 29 (10 ULg)
Peer Reviewed
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 ▲]

Detailed reference viewed: 24 (1 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 31 (3 ULg)
Full Text
See detail"Il vaut mieux prévenir que guérir", l'adage s'applique également aux plantes
Massart, Sébastien ULg

Article for general public (2017)

Detailed reference viewed: 16 (1 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 49 (4 ULg)
Full Text
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.

Detailed reference viewed: 56 (25 ULg)
Full Text
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.

Detailed reference viewed: 1965 (780 ULg)
Full Text
See detailPredicting the future of an endemic endangered Andean bird species with a niche-based-model nested into a dynamic vegetation model
Hambuckers, Alain ULg; Zuniga, Lilian; Dury, Marie ULg et al

Conference (2017, February 05)

The slopes of the Andes are recognized as supporting the highest avian diversity in the world combined with high endemism rate but also more than 20 % of threatened species. Frugivores birds, even rare ... [more ▼]

The slopes of the Andes are recognized as supporting the highest avian diversity in the world combined with high endemism rate but also more than 20 % of threatened species. Frugivores birds, even rare species, are known as major providers of seed dispersal service. In Bolivia, the large Red-fronted Macaw (Ara rubrogenys Lafresnaye, 1847) is one of the 15 endemic species of this country. Its natural habitat is mainly semi-deciduous dry forest but this habitat is most often severely degraded. Climate change is an additional threat over tropical mountain birds and this particular species, since some scenarios suggest warming as high as 7.5°C by 2080 and significant variations in the precipitation regime and available soil water. To infer the future of bird species under warming climate, many authors use niche-based models (NBM), in which they combine effects of climate variables, alone or in combination with other environmental variables. A more elaborated approach consists in also including biotic interactions, notably the availability of particular plant species. While NBM with climate variables are now considered as a standard method to predict plant species distribution under future climate, this approach fails to consider the effect of increasing CO2 concentration in air on plant physiology. Contrariwise, dynamic vegetation models (DVM) are commonly able to reproduce this effect, although the uncertainties on the CO2 are large. This study assesses the potential impact of climate change on the range of A. rubrogenys, by combining within a NBM climate variables, relief and biotic variables, i.e. plant species resource. Plant resource is computed with a DVM and a NBM to compare the methodologies and to evaluate potential effects of CO2 on plant species distribution and indirect impacts on the bird. [less ▲]

Detailed reference viewed: 45 (5 ULg)
Full Text
See detailQuestions d'argent - Damien Ernst
Sury, Caroline; Ernst, Damien ULg

Article for general public (2017)

Detailed reference viewed: 74 (8 ULg)
See detailLa radiation des tortues marines au Crétacé moyen
Scavezzoni, Isaure ULg

Conference given outside the academic context (2017)

"Turtles" (Testudines) form a successful group of reptiles with several terrestrial, marine and fresh-water species. Their peculiar and somewhat constrained morphology (i. e. : carapace incorporating ribs ... [more ▼]

"Turtles" (Testudines) form a successful group of reptiles with several terrestrial, marine and fresh-water species. Their peculiar and somewhat constrained morphology (i. e. : carapace incorporating ribs, curved limbs, anapsid skull exempt of temporal fenestrae) and ecology has often obscured their relationships and, hence, their evolutionary history, notably in marine turtles (chelonioids). Modern chelonioids are divided in two clades (i. e. : shoft-shelled turtles and hard-shelled turtles) supported by distinct morphological and embryological characters. Their origin is traced back up to the Cretaceous, along with a series of extinct forms, many of which being collectively known as Protostegidae. Fossil evidence show that at least five clades of marine turtles were roaming the seas at the end of the Cretaceous. In fact, chelonioids appeared during the first stages of the Early Cretaceous and quickly exploded to reach a high level of disparity at the lowermost part of the late Cretaceous. Therefore, the Mesozoic radiation of chelonioids must have happened during the "middle" Cretaceous (especially the Aptian-Albian interval). However this radiation is poorly understood as the phylogenetic relationships of marine turtles are not resolved yet. Bringing new data may help resolve these issues, and it is the exact reason why the genus Rhinochelys is being investigated. [less ▲]

Detailed reference viewed: 31 (2 ULg)
Full Text
See detailDroit constitutionnel belge - Dossier de documentation (année académique 2016-2017)
Behrendt, Christian ULg

Learning material (2017)

Le document constitue le Dossier de documentation, à lire par les étudiants en parallèle au cours ex cathedra, de l'enseignement de Droit constitutionnel dispensé à l'Université de Liège en bachelier en ... [more ▼]

Le document constitue le Dossier de documentation, à lire par les étudiants en parallèle au cours ex cathedra, de l'enseignement de Droit constitutionnel dispensé à l'Université de Liège en bachelier en droit et en science politique [less ▲]

Detailed reference viewed: 1011 (285 ULg)