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See detailAllelic variation contributes to bacterial host specificity
Yue, Min; Han, Xiangan; De Masi, Leon et al

in Nature Communications (2015)

Understanding the molecular parameters that regulate cross-species transmission and host adaptation of potential pathogens is crucial to control emerging infectious disease. Although microbial pathotype ... [more ▼]

Understanding the molecular parameters that regulate cross-species transmission and host adaptation of potential pathogens is crucial to control emerging infectious disease. Although microbial pathotype diversity is conventionally associated with gene gain or loss, the role of pathoadaptive nonsynonymous single-nucleotide polymorphisms (nsSNPs) has not been systematically evaluated. Here, our genome-wide analysis of core genes within Salmonella enterica serovar Typhimurium genomes reveals a high degree of allelic variation in surface-exposed molecules, including adhesins that promote host colonization. Subsequent multinomial logistic regression, MultiPhen and Random Forest analyses of known/suspected adhesins from 580 independent Typhimurium isolates identifies distinct host-specific nsSNP signatures. Moreover, population and functional analyses of host-associated nsSNPs for FimH, the type 1 fimbrial adhesin, highlights the role of key allelic residues in host-specific adherence in vitro. Together, our data provide the first concrete evidence that functional differences between allelic variants of bacterial proteins likely contribute to pathoadaption to diverse hosts. [less ▲]

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See detailLyot-plane phase masks for improved high-contrast imaging with a vortex coronagraph
Ruane, Garreth J.; Huby, Elsa ULg; Absil, Olivier ULg et al

in Astronomy and Astrophysics (2015), 583

The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial ... [more ▼]

The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial capability for direct detection and characterization of exoplanets and circumstellar disks. Telescopes with aperture obstructions, such as secondary mirrors and spider support structures, require advanced coronagraph designs to provide adequate starlight suppression. We introduce a phase-only Lyot-plane optic to the vortex coronagraph that offers improved contrast performance on telescopes with complicated apertures. Potential solutions for the European Extremely Large Telescope (E-ELT) are described and compared. Adding a Lyot-plane phase mask relocates residual starlight away from a region of the image plane thereby reducing stellar noise and improving sensitivity to off-axis companions. The phase mask is calculated using an iterative phase retrieval algorithm. Numerically, we achieve a contrast on the order of $10^{-6}$ for a companion with angular displacement as small as $4~\lambda/D$ with an E-ELT type aperture. Even in the presence of aberrations, improved performance is expected compared to either a conventional vortex coronagraph or optimized pupil plane phase element alone. [less ▲]

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See detailFlexible multibody system modelling: A geometric local frame approach on SE(3)
Sonneville, Valentin ULg

Scientific conference (2015, October 30)

In order to improve computational costs in the frame of flexible multibody system modelling, we propose a geometrically exact framework relying on a local frame description. Thanks to this framework ... [more ▼]

In order to improve computational costs in the frame of flexible multibody system modelling, we propose a geometrically exact framework relying on a local frame description. Thanks to this framework, geometric non-linearities are strongly reduced for two reasons. Firstly, the equations of motion can be solved without introducing a global parametrization of the motion, which also leads to a naturally singularity-free description of large rotations. Secondly, the equations of motion are expressed in a local frame, both at position and rotation level, leading to intrinsic equations. Accordingly, these equations are insensitive to large amplitude motions, such that the geometric non-linearities are naturally filtered. The mathematical developments are carried out in a Lie group setting which, albeit more abstract than classical treatments, provides generic and powerful well established tools. So far, several elements have been formulated in this framework: rigid body, kinematic joints and a flexible beam finite element. A shell finite element and a super-element are also under development. Some interesting numerical advantages are observed following the reduction of geometric non-linearities, e.g., the iteration matrix depends on relative motion within the elements only and is thus invariant under rigid body motions. [less ▲]

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See detailCorps-pour-autrui et anorexie mentale : présentation d’une étude belgo-suisse
Englebert, Jérôme ULg; Minguet, Eugénie

Scientific conference (2015, October 30)

Detailed reference viewed: 33 (0 ULg)
See detailRenewable and non-renewable intermittent energy sources: Friends and foes?
Jacqmin, Julien ULg

Scientific conference (2015, October 30)

Detailed reference viewed: 12 (1 ULg)
See detailL'être-au-monde borderline
Englebert, Jérôme ULg

Scientific conference (2015, October 30)

Detailed reference viewed: 33 (3 ULg)
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See detailIdentification of the bacterial symbionts of the banana aphid Pentalonia nigronervosa and characterization of their roles
De Clerck, Caroline ULg

Doctoral thesis (2015)

Les insectes sont caractérisés par une incroyable capacité d’adaptation à de nombreux environnements et modes d’alimentation, qui est liée au fait que la majorité des insectes (voire tous) hébergent des ... [more ▼]

Les insectes sont caractérisés par une incroyable capacité d’adaptation à de nombreux environnements et modes d’alimentation, qui est liée au fait que la majorité des insectes (voire tous) hébergent des symbiontes intra ou extracellulaires. Ces associations symbiotiques sont très diverses et peuvent aller d’un mutualisme obligatoire à un parasitisme facultatif. Les pucerons, en particulier, sont connus pour vivre en symbiose avec au moins une bactérie obligatoire qui leur fournit les nutriments essentiels absents du phloème dont ils se nourrissent : Buchnera aphidicola. La plupart des symbiontes d’insectes étant incultivables, les technologies moléculaires modernes se sont avérées des outils puissants dans la compréhension des interactions hôte-microorganisme et la caractérisation du rôle joués par ces symbiontes. Les études génomiques ont mené à la découverte des plus petits génomes bactériens jamais observés, et ont permis une étude plus poussée des symbiontes secondaires et de leur évolution. Pentalonia nigronervosa, le puceron noir du bananier, lest le vecteur principal du virus des sommets touffus du bananier, l’un des virus les plus dommageables en culture bananière. Très peu d’études sont néanmoins disponibles sur ce vecteur et rien n’était connu sur la population symbiotique hébergée par cet insecte jusqu’à cette étude. Dans cette thèse, nous avons découvert que le puceron du bananier contient deux symbiontes : B. aphidicola (BPn) et Wolbachia sp. (wPn); et cela dans tous les pucerons testés, quelle que soit leur origine géographique. La présence de Buchnera était attendue (99,9% de toutes les espèces de pucerons contiennent ce symbionte), mais la détection systématique de Wolbachia nous fait nous interroger sur le rôle que cette bactérie pourrait jouer pour l’insecte hôte, ainsi que sur la raison de sa présence. Wolbachia n’est en effet que rarement détectée chez les pucerons et est surtout connue pour être un parasite qui manipule le système reproducteur de ces hôtes. Malgré tout, des études ont montré que cette bactérie pouvait agir comme mutualiste pour certains insectes, ce qui pourrait expliquer sa présence dans le puceron du bananier. Le second objectif de cette étude a donc été de mieux comprendre le rôle joué par les deux symbiontes de P. nigronervosa. Pour ce faire, différentes techniques complémentaires ont été utilisées. La microinjection d’antibiotiques a été utilisée afin d’éliminer sélectivement wPn et de voir l’effet de cette élimination sur l’hôte. Nous avons observé que l’élimination de wPn donnait systématiquement lieu à la mort du puceron. Un séquençage haut débit de l’hémolymphe (contenant des bacteriocytes) d’un puceron a été réalisé et nous a permis d’identifier et d’annoter 587 et 250 gènes pour wPn et BPn respectivement. L’analyse de ces gènes nous permet d’émettre l’hypothèse que les deux bactéries collaborent pour la production de plusieurs nutriments essentiels pour l’hôte. La situation est surtout frappante dans le cas de la lysine et de la riboflavine, qui sont habituellement produits uniquement par Buchnera chez les autres espèces de pucerons. Dans le cas du puceron du bananier, les gènes impliqués dans les voies de production de ces métabolites sont répartis entre les génomes des deux bactéries, les rendant ainsi toutes les deux essentielles à la survie du puceron hôte. Enfin, une localisation par fluorescence in situ des deux symbiontes a montré qu’ils étaient tous deux localisés dans les bacteriocytes, rendant les échanges de précurseurs et métabolites possibles. En conclusion, nos résultats suggèrent que le puceron du bananier héberge une co-symbiose obligatoire entre B. aphidicola et Wolbachia, les deux bactéries agissant de concert dans l’approvisionnement de l’hôte en nutriments essentiels. [less ▲]

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See detailFaculty engagement with blended learning - A study based on the Theory of Planned Behavior
Huart, Johanne ULg; Detroz, Pascal ULg; Verpoorten, Dominique ULg

Conference (2015, October 29)

The paper presents the methodology and results of a survey research conducted at the University of Liege (Belgium) about blended learning (Garrison & Vaughan, 2012). It investigates the level of use of ... [more ▼]

The paper presents the methodology and results of a survey research conducted at the University of Liege (Belgium) about blended learning (Garrison & Vaughan, 2012). It investigates the level of use of this instructional practice and elicits determinants that predict or prevent its implementation. [less ▲]

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See detailInfusing SoTL components in staff training - A faculty development continuum at the university of Liège
Verpoorten, Dominique ULg; Jérôme, Françoise ULg; Delfosse, Catherine ULg et al

Conference (2015, October 29)

This presentation documents the attempt of the University of Liège (Belgium) to establish a "pedagogical development continuum" by offering three nested programs, each likely to be credited in the next ... [more ▼]

This presentation documents the attempt of the University of Liège (Belgium) to establish a "pedagogical development continuum" by offering three nested programs, each likely to be credited in the next one, thanks to a single overarching competency framework (the CREER model). At a proper level of intensity, each program builds upon components of SoTL, defined after Potter & Kustra (2011) as: "the systematic study of teaching and learning, using established or validated criteria of scholarship, to understand how teaching (beliefs, behaviours, attitudes, and values) can maximize learning, and/or develop a more accurate understanding of learning, resulting in products that are publicly shared for critique and use by an appropriate community". [less ▲]

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See detailAssessment of Non-Lethal Projectile Head Impacts
Oukara, Amar ULg

Doctoral thesis (2015)

Anti-personnel Non-Lethal Weapons (NLW) are used to impart sufficient effect onto a person in order to deter uncivil, suspect or hazardous behaviour with a low prob- ability of permanent or fatal injury ... [more ▼]

Anti-personnel Non-Lethal Weapons (NLW) are used to impart sufficient effect onto a person in order to deter uncivil, suspect or hazardous behaviour with a low prob- ability of permanent or fatal injury. They appear to be suitable for many law enforcement missions and to a certain extent to the military forces. In fact, in many situations of conflict, where the army and civil police are involved, the use of such weapons can ensure a minimal risk of collateral damage. The most used NLW are Kinetic Energy Non-Lethal Weapons (KENLW) that involve the shooting of a de- formable or breakable projectile with masses between 5 g to 140 g at initial velocities between 70 m/s and 160 m/s. Practically, KENLW are not used without risk for the targeted persons. The head zone represents the most critical part of the human body regarding non-lethal projectile impacts. The inflicted injuries can be severe and sometimes lead to death. The experts in the field should identify the limits in which KENLW should be effective without causing permanent or fatal injuries. Therefore, assessment methods should be developed in order to predict the injury risk of non-lethal head impacts. The present thesis proposes the development of three different approaches allowing the assessment of the non-lethal head impacts. The first approach named FW (Force wall) method has been developed at DGA (Direction Générale de l’Armement) - France. For a benchmark projectile, this method links the maximum impact head force to the maximum impact force mea- sured on a supposedly infinitely rigid structure, equipped with a piezoelectric force sensor. Three lesional thresholds: unconsciousness, meningeal damage and bone damage with coma are used. The FW method proposes the extension of the bench- mark projectile results to other projectiles using the assumption: two different pro- jectiles producing the same force on a rigid structure, will have the same effects on the head. This method is applied in the present thesis for different projectiles using a specific experimental setup. Different improvements have been achieved regarding the frequency analysis of the rigid structure and the quantification of uncertainties of the FW method. These improvements represent some original contributions of the present thesis.The second approach concerns the use of a mechanical surrogate in order to predict the maximum impact head force. The mechanical surrogate involved in the present study is BLSH (Ballistics Load Sensing Headform). Different tests have been performed using no less than eight commercial projectiles. The third approach uses numerical simulations with a validated FEHM (Fi- nite Element Head Model). SUFEHM (Strasbourg University Finite Element Head Model) is considered in the present thesis. The model offers the possibility to pre- dict head injuries using other parameters than the maximum impact head force: the strain energy and the Von Mises stress. A specific method is proposed in order to develop the FE (Finite Element) models of non-lethal projectiles. Six FE models of projectiles are used for the numerical simulations. Results show a good agreement between the three methods for the benchmark projectile. The extension of the FW method for other projectiles can be performed with some limitations mentioned in the present document. Moreover, there is a good agreement between BLSH and SUFEHM for all studied projectiles. Different correlations between the maximum impact head force and other criteria are also proposed in order to include them in the non-lethal head impact injury prediction. Ultimately, the present work proposes assessment methods for non-lethal projec- tile head impacts. The different details of these methods are given in the present document. [less ▲]

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See detailRevealed preference tests of collectively rational consumption behavior
Crama, Yves ULg

Scientific conference (2015, October 29)

To verify the empirical adequacy of a particular household consumption model, it is important to develop efficient tests did can be applied to real-world data. These tests check whether the observed ... [more ▼]

To verify the empirical adequacy of a particular household consumption model, it is important to develop efficient tests did can be applied to real-world data. These tests check whether the observed household behavior is "rational" in the sense that it is consistent with the predictions of the model. In this talk, we present different approaches based on revealed preferences to test collective models of household consumption. Testing collective rationality is computationally difficult (NP-hard). In order to overcome this negative result, we introduce mixed-integer programming formulations which can be used for medium-sized datasets. Next, we propose simulated annealing heuristics, which allow for efficient testing of the collective model on large datasets. We present the results of computational experiments with our approaches. Joint work with: Fabrice Talla Nobibon, Laurens Cherchye, Thomas Demuynck, Bram De Rock and Frits CR Spieksma. [less ▲]

Detailed reference viewed: 21 (0 ULg)
See detailThe potential of OpenStreetMap for land use/land cover mapping
Minet, Julien ULg; Robert, Brieuc; Tychon, Bernard ULg

Conference (2015, October 29)

Land use and land cover (LULC) maps are important tools for the management of the environment, in particular for the modelling of biogeochemical cycles and climate. LULC maps are typically produced using ... [more ▼]

Land use and land cover (LULC) maps are important tools for the management of the environment, in particular for the modelling of biogeochemical cycles and climate. LULC maps are typically produced using supervised classification of satellite images supported by expert knowledge. Nowadays, the advance of the crowdsourced project OpenStreetMap (OSM) offers an alternative to official LULC maps. In OSM, LULC is usually mapped by manual digitalisation of satellite imagery and/or by the import of existing databases. We explored the potential of OSM to contribute to the improvement of an existing LULC map, Corine Land Cover (CLC), by comparing forest cover in Southern Belgium and Luxembourg. We focused on three forest types that were common to the two databases: coniferous, deciduous and mixed forest. Confusion matrices showed that the two databases differed in terms of classes over about one quarter of the forest area. Moreover, 9.9% and 8.0% of the forest area in OSM and CLC, respectively, were unmapped as forest area compared to the other database. Compared to CLC data, small patches of forest areas are mapped in OSM data. This study is a first attempt to show the potential of a crowdsourced project, i.e., OSM, to contribute to an official geodatabase. While current drawbacks of OSM such as the lack of completeness may limit its application in some operational applications, we claim that its large accessibility and its potentially high reactiveness makes OSM a serious alternative to existing geodatabase. [less ▲]

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See detailGood OA practices from Funders: FRS/FNRS, Belgium
Rentier, Bernard ULg

Scientific conference (2015, October 29)

The FRS/FNRS is the major funding agency for basic research in the French-speaking Community of Belgium. In 2013, it passed an internal regulation mandating, for researchers receiving salaries and/or ... [more ▼]

The FRS/FNRS is the major funding agency for basic research in the French-speaking Community of Belgium. In 2013, it passed an internal regulation mandating, for researchers receiving salaries and/or grant money fron the Fund, the deposit in their institutional OA repository of all their scientific production in full text. The FRS/FNRS supports APCs, up to 500 € per article, but not in "hybrid" journals. [less ▲]

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See detailOpen Access: where do we go from here: Bernard Rentier's personal reflexions on the future of OA
Rentier, Bernard ULg

Scientific conference (2015, October 29)

Detailed reference viewed: 23 (3 ULg)
See detailHistoire et mémoire : quelle relation au XXIe siècle ?
Grandjean, Geoffrey ULg

Speech/Talk (2015)

Detailed reference viewed: 16 (1 ULg)
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See detailStudy of the Direct Borohydride Fuel Cell anode
Olu, Pierre-Yves ULg

Doctoral thesis (2015)

Detailed reference viewed: 68 (6 ULg)