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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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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 ▲]

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See detailQuestions d'argent - Damien Ernst
Sury, Caroline; Ernst, Damien ULg

Article for general public (2017)

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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 ▲]

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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 ▲]

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See detailY a-t-il eu un impérialisme linguistique romain ?
Rochette, Bruno ULg

Scientific conference (2017, February 03)

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See detailDNA Labeling at Electron Microscopy
Thelen, Nicolas ULg; Thiry, Marc ULg

in Carlo, Pellicciari; Marco Biggiogera, Biggiogera (Eds.) Histochemistry of Single Molecules (2017)

Here, we describe a method for locating DNA on ultrathin sections. This technique is compatible with all usual fixation and embedding procedures and can be combined with cytochemical methods. Ultrathin ... [more ▼]

Here, we describe a method for locating DNA on ultrathin sections. This technique is compatible with all usual fixation and embedding procedures and can be combined with cytochemical methods. Ultrathin sections are incubated in a medium containing terminal deoxynucleotidyl transferase (TdT) and various non-isotopic nucleotide analogs. The labeled nucleotides bound to the surface of ultrathin sections are then visualized by an indirect immunogold labeling technique. This high-resolution method provides a powerful tool for pinpointing the precise location of DNA within biological material, even where DNA is present in very low amounts. [less ▲]

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See detailC'est la faute à l'Europe !
Grandjean, Geoffrey ULg

Conference given outside the academic context (2017)

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See detailLa voix dans tous ses états.
Morsomme, Dominique ULg

Conference given outside the academic context (2017)

La voix occupe une place prépondérante dans notre vie. Elle fait partie de notre identité. Sur un simple « allo », nous identifions aisément son propriétaire, plus encore nous sommes capables de détecter ... [more ▼]

La voix occupe une place prépondérante dans notre vie. Elle fait partie de notre identité. Sur un simple « allo », nous identifions aisément son propriétaire, plus encore nous sommes capables de détecter son humeur. Si elle s’enraye, elle perturbe non seulement notre capacité à communiquer, mais elle influence également la perception que l’auditeur a de nous. Elle fait l’objet de recherche au carrefour de domaines aussi variés que la médecine, la psychologie, la logopédie et la pédagogie. Nous débuterons cette conférence par voyager dans le monde de la voix via différents échantillons vocaux provenant des 4 coins du monde. Cette expérience auditive nous permettra de prendre conscience des nombreuses capacités de notre système vocale. Ensuite, nous tâcherons de comprendre son fonctionnement et ses caractéristiques. Nous discuterons des professionnels de la voix, ceux que vous croisez tous les jours, les enseignants, les orateurs, les présentateurs. Nous parlerons de la charge vocale et de ce qu’implique un métier à voix. Le concept de dysphonie, trouble de la voix parlée, sera abordé et nous verrons comment la médecine et la logopédie peuvent répondre aux plaintes de patients dysphoniques. Nous terminerons cet exposé par des extraits de films de rééducation afin que vous compreniez mieux en quoi consiste une rééducation vocale. Nous espérons ainsi rendre à la voix la place qu’elle mérite dans notre système social et humain. [less ▲]

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See detailDe quelles(s) mémoire(s) parlons-nous ? Monopole et concurrence mémoriels
Grandjean, Geoffrey ULg

Conference given outside the academic context (2017)

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See detailLocutifs et énoncés non verbaux en ancien français
Mazziotta, Nicolas ULg

Conference (2017, February 02)

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See detailLe behaviorisme logique en question
Dony, Arthur ULg

in Bulletin d'Analyse Phénoménologique (2017), XIII(1), 1-19

Dans une démarche inspirée des sciences de la nature, le behaviorisme logique se présente comme une théorie philosophique visant à rendre compte des états mentaux de façon « objective », en réduisant ceux ... [more ▼]

Dans une démarche inspirée des sciences de la nature, le behaviorisme logique se présente comme une théorie philosophique visant à rendre compte des états mentaux de façon « objective », en réduisant ceux-ci au comportement observable. Comme l’énonçait déjà Hempel, il s’agit de traduire tout énoncé psychologique en un énoncé où ne figurent plus que des concepts physiques de façon à faire l’économie de la dimension subjective de l’expérience, laquelle ne constituerait rien de plus qu’un simple rouage à vide, inessentiel à l’état mental lui-même. Dans cet article, je propose d’examiner les principaux arguments, désormais jugés classiques, avancés par Wittgenstein, Ryle et Dennett en faveur de cette théorie. Mon but est non seulement de mettre au jour les déficiences de l’argumentation et les présupposés problématiques qui la guident, mais plus fondamentalement de montrer en quoi cette doctrine, en dépit de la popularité qu’elle s’est acquise en philosophie contemporaine, s’avère à l’analyse inconsistante. [less ▲]

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