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See detailTransition between symmetric and asymmetric flow in rectangular shallow reservoirs — a case of maximum dissipation?
westhoff, Martijn; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2017, April)

Shallow reservoirs are often used in hydraulic engineering as sediment traps or storage basins, Sedimentation within these reservoirs depends on the flow pattern, which in turn depends on the shape of the ... [more ▼]

Shallow reservoirs are often used in hydraulic engineering as sediment traps or storage basins, Sedimentation within these reservoirs depends on the flow pattern, which in turn depends on the shape of the reservoir. For short rectangular reservoirs, the main jet flows straight from the inlet to the outlet with on both sides identical recirculation zones. In longer reservoirs, however, the main jet reattaches to the side of the reservoir leading to a small and a large recirculation zone. Previous studies have found an empirical geometric relation describing the switch between these two different flow patterns. In this study, we demonstrate that this switch in flow pattern coincides with a maximization of energy dissipation in the shear layer between the main jet and the recirculation zones. To show this we described the power received from the jet by the recirculation zone as the product of a fluid-fluid friction coefficient and the square of the velocity difference times the shear velocity of the recirculation zone. This power is balanced by the bottom friction of the recirculation zone. Energy dissipation in the shear layer is then determined as the difference between the power performed by the jet and the power received by the recirculation zone. In this setup, energy dissipation is maximized by optimizing the friction coefficient. We show that for short reservoir lengths, energy dissipation is higher in the case of a symmetric flow pattern, while for longer reservoir the energy dissipation is higher for asymmetric flow patterns. The simulated switch between the two flow patterns appears to be very close to the empirical relation. This suggests that the flow pattem adapts in order to maximize energy dissipation between the jet and recirculation zones. The strength of this approach lies in the fact that no detailed knowledge of small scale processes is needed, while large scale structure formation can still be predicted. [less ▲]

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See detailPrice Discrimination and Dispersion under Asymmetric Profiling of Consumers
Lam, Wing Man Wynne ULg; Belleflamme, Paul; Vergote, Wouter

E-print/Working paper (2017)

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See detailAn investigation into the fraction of particle accelerators among colliding-wind binaries. Towards an extension of the catalogue
De Becker, Michaël ULg; Benaglia, Paula; Romero, Gustavo E. et al

in Astronomy and Astrophysics (2017), 600

Particle-accelerating colliding-wind binaries (PACWBs) are multiple systems made of early-type stars able to accelerate particles up to relativistic velocities. The relativistic particles can interact ... [more ▼]

Particle-accelerating colliding-wind binaries (PACWBs) are multiple systems made of early-type stars able to accelerate particles up to relativistic velocities. The relativistic particles can interact with different fields (magnetic or radiation) in the colliding-wind region and produce non-thermal emission. In many cases, non-thermal synchrotron radiation might be observable and thus constitute an indicator of the existence of a relativistic particle population in these multiple systems. To date, the catalogue of PACWBs includes about 40 objects spread over many stellar types and evolutionary stages, with no clear trend pointing to privileged subclasses of objects likely to accelerate particles. This paper aims at discussing critically some criteria for selecting new candidates among massive binaries. The subsequent search for non-thermal radiation in these objects is expected to lead to new detections of particle accelerators. On the basis of this discussion, some broad ideas for observation strategies are formulated. At this stage of the investigation of PACWBs, there is no clear reason to consider particle acceleration in massive binaries as an anomaly or even as a rare phenomenon. We therefore consider that several PACWBs will be detected in the forthcoming years, essentially using sensitive radio interferometers which are capable of measuring synchrotron emission from colliding-wind binaries. Prospects for high-energy detections are also briefly addressed. [less ▲]

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See detailLes retardateurs de flamme bromés : impact sur l'environnement et la santé des individus exposés
Dufour, Patrice ULg; Charlier, Corinne ULg

in Annales de Biologie Clinique (2017), 75(2), 146-157

Depuis l’antiquité, l’homme utilise des moyens chimiques pour protéger ses biens des incendies. Efficaces et faciles d’emploi, les retardateurs de flamme bromés sont utilisés depuis plusieurs décennies de ... [more ▼]

Depuis l’antiquité, l’homme utilise des moyens chimiques pour protéger ses biens des incendies. Efficaces et faciles d’emploi, les retardateurs de flamme bromés sont utilisés depuis plusieurs décennies de façon massive dans l’industrie du plastique. À l’instar d’autres composés organohalogénés, les retardateurs de flamme bromés sont très persistants dans l’environnement et capables de s’accumuler le long de la chaîne alimentaire. De nombreux auteurs ont mis en évidence leur présence dans notre environnement, chez différentes espèces animales mais également dans le sérum humain. Plus inquiétant encore, l’homme est exposé à ces polluants dès la grossesse et par la suite via le lait maternel. Cette exposition pourrait avoir des conséquences sur notre santé. De nombreuses études in vitro, in vivo ou épidémiologiques ont mis en lumière une influence néfaste des retardateurs de flamme bromés sur notre système endocrinien, principalement au niveau de la fonction thyroïdienne mais également de la reproduction, du neurodéveloppement chez l’enfant et du métabolisme avec un risque accru de développer un diabète. Si une certaine prise de conscience a déjà eu lieu au niveau des autorités et de certaines grandes entreprises, de nouvelles études sont nécessaires pour confirmer les tendances déjà dégagées, élucider les mécanismes sous-jacents et déterminer s’il existe des synergies avec d’autres polluants tels que par exemple les PCB. [less ▲]

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See detailBien raisonner en TSUM (Transition Secondaire-Université en Mathématiques)
Bair, Jacques ULg

E-print/Working paper (2017)

Bien raisonner est assurément une des compétences clés que doivent acquérir et développer les étudiants entrant à l’Université. Nous y consacrons entièrement ce travail illustré par de nombreux exemples ... [more ▼]

Bien raisonner est assurément une des compétences clés que doivent acquérir et développer les étudiants entrant à l’Université. Nous y consacrons entièrement ce travail illustré par de nombreux exemples construits à partir de notre expérience professionnelle. En premier lieu, nous distinguons, à la suite de G. Polya, les raisonnements plausibles des raisonnements démonstratifs. Ensuite, nous nous intéressons à certains éléments de logique qui nous paraissent importants au niveau d’une TSUM. Puis, nous analysons la nature de preuves mathématiques à ce stade de l’apprentissage. Enfin, nous dissertons quelque peu sur l’usage des démonstrations dans l’enseignement. Ce travail se termine par deux annexes techniques, relatives respectivement à différents types de syllogismes et à quelques éléments plus formels de logique mathématique. [less ▲]

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See detailTectonic, human and climate signal over the last 4000 years in the Lake Amik record (southern Turkey)
El Ouahabi, Meriam ULg; Hubert, Aurelia ULg; Vander Auwera, Jacqueline ULg et al

Poster (2017, April)

This study investigates the upper sediments infilling the central part of the Amik Basin in Southern Turkey. The Amik Basin is located in a tectonically active area: it is crossed by the Dead Sea Fault, a ... [more ▼]

This study investigates the upper sediments infilling the central part of the Amik Basin in Southern Turkey. The Amik Basin is located in a tectonically active area: it is crossed by the Dead Sea Fault, a major neotectonic structure in the Middle East extending from the Red Sea in the South to the East Anatolian Fault Zone in the North. Continuous human occupation is attested since 6000-7000 BC in the Amik Basin. The study focuses on the sedimentary record of the Lake Amik occupying the central part of the Basin. Our objective is to constrain major paleo-environmental changes over the last 4000 years. The lake has been drained and progressively dried up since the mid-50s. The absence of water column during the summer season allows to collect lacustrine samples along a 5 meter depth trench with a sampling resolution of 1 to 2 cm. Diverse complementary methods were applied to characterize the sedimentary record: i.e. magnetic susceptibility, grain size, organic and inorganic matter by loss-of-ignition, mineralogy by X-ray diffraction and core scanner X-ray fluorescence (XRF) geochemistry. The age of the record is constrained combining radionuclide and radiocarbon datings. Structural disturbances observed in the lacustrine sediments record are linked with major historical earthquakes from the 6th to the 9th century AD due to the Hasipasa Fault rupture. In addition to the tectonic influence, the sedimentary record clearly shows two periods indicating strong soil erosion in the lake catchment: (1) the most recent erosion phase occurs over the Roman period to Present; (2) the oldest one would have occurred during the Late Bronze period. Such changes are most probably related to change in land use. In term of climate influences, the mineralogical and geochemical results allow to evidence variations in chemical weathering conditions in the watershed and lake water level fluctuations, respectively. The clay mineral assemblages attest for significant pedogenesis transformations, especially during the Islamic/Ottoman period. Based on XRF results, an increase in potassium is attributed to a lake development phase during a wet phase An overflow of the Orontes River would be responsible for clay deposition. By contrast, increased calcium and strontium rather correspond to a low lacustrine level and a drier period. The Bronze and Iron/Hellenistic periods are both characterized by low lake level with limited contribution from the watershed. To conclude, our multiproxy study of the Lake Amik allows to decipher between tectonic, human and climate influences over the last 4000 years. Further step would be to compare the Amik record with other regional archives to evidence local and regional events. [less ▲]

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See detailétude sur l'intolérance à l'incertitude et ses biais cognitifs chez les parents d'un enfant en rémission d'un cancer
Vander Haegen, Marie ULg; Etienne, Anne-Marie ULg; Piette, Caroline

in Revue Médicale de Liège (2017), 72

Résumé : Les études en oncologie pédiatrique décrivent une relativement bonne qualité de vie chez les enfants survivants de cancer. À ce jour, peu d’études se sont intéressées aux parents d’un enfant ... [more ▼]

Résumé : Les études en oncologie pédiatrique décrivent une relativement bonne qualité de vie chez les enfants survivants de cancer. À ce jour, peu d’études se sont intéressées aux parents d’un enfant survivant de cancer. Soixante-et-un parents sont recrutés dans les hôpitaux belges. Trois groupes de parents sont constitués : les parents dont l’enfant est à 4 ans de rémission (groupe 1), à 5 ans de rémission (groupe 2) et à 6 ans de rémission (groupe 3). Des échelles cliniques et une tâche de Stroop émotion sont administrées. Les parents (des 3 groupes) présentent une faible tolérance à l’incertitude, ont des inquiétudes excessives quant à l’évolution de la santé de leur enfant et souffrent de symptômes anxieux. Le Stroop émotion révèle un biais cognitif de l’attention en faveur des stimuli de nature menaçante. L’étude met en exergue l’importance de détecter les parents intolérants à l’incertitude lors du diagnostic d’annonce du cancer et leur suivi psychologique continu une fois les traitements terminés. [less ▲]

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See detailFluvial dike breaching due to overtopping: how different is it from dam breaching?
Rifai, Ismail; Erpicum, Sébastien ULg; Archambeau, Pierre ULg et al

Conference (2017, April)

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See detailUn contrat d'enseignement de la médecine du IIIe siècle avant notre ère : P.Heid. III 226
Ricciardetto, Antonio ULg

in Ricciardetto, Antonio; Marganne, Marie-Hélène (Eds.) En marge du Serment hippocratique : contrats et serments dans le monde gréco-romain. Actes de la Journée d'étude internationale (Université de Liège, 29 octobre 2014) (2017, April)

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See detailThe Case of the Decaying Cadaver
Stefanuto, Pierre-Hugues ULg; Focant, Jean-François ULg

in The Analytical Scientist (2017), 51

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See detailSustainable Transport through Taxation. Analysis of Road Passenger Transport: Constraints, Limits and Prospects
Vanrykel, Fanny ULg

Scientific conference (2017, April)

Présentation du projet de thèse "La fiscalité au service d’un transport durable. Analyse du transport routier de personnes: contraintes, limites et perspectives"

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See detailIntroduction
Ricciardetto, Antonio ULg

in Ricciardetto, Antonio; Marganne, Marie-Hélène (Eds.) En marge du Serment hippocratique : contrats et serments dans le monde gréco-romain. Actes de la Journée d'étude internationale (Université de Liège, 29 octobre 2014) (2017, April)

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See detailEntre Rome et l’Égypte romaine. Pour une étude de la nourrice entre littérature médicale et contrats de travail
Ricciardetto, Antonio ULg; Gourevitch, Danielle

in Ricciardetto, Antonio; Marganne, Marie-Hélène (Eds.) En marge du Serment hippocratique : contrats et serments dans le monde gréco-romain. Actes de la Journée d'étude internationale (Université de Liège, 29 octobre 2014) (2017, April)

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See detailGlobaLex / Update : Research Guide to Belgian Law
Malliet, Christoph; Desseilles, François ULg

Learning material (2017)

1. The Belgian Legal System in a Nutshell 2. Developments in Belgian Legal Documentation 3. Legal Documentation

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See detailOn the identification of paedomorphic and overwintering larval newts based on cloacal shape: review and guidelines
Denoël, Mathieu ULg

in Current Zoology (2017), 63(2), 165-173

Paedomorphosis is an alternative process to metamorphosis in which adults retain larval traits at the adult stage. It is frequent in newts and salamanders, where larvae reach sexual maturity without ... [more ▼]

Paedomorphosis is an alternative process to metamorphosis in which adults retain larval traits at the adult stage. It is frequent in newts and salamanders, where larvae reach sexual maturity without losing their gills. However, in some populations, larvae overwinter in water, while remaining immature. These alternative ontogenetic processes are of particular interest in various research fields, but have different causes and consequences, as only paedomorphosis allows metamorphosis to be bypassed before maturity. It is thus relevant to efficiently identify paedomorphs versus overwintering larvae. In this context, the aim of this paper was threefold: firstly, to perform a meta-analysis of the identification procedures carried out in the literature; secondly, to determine the effectiveness of body size to make inferences about adulthood by surveying natural newt populations of Lissotriton helveticus and Ichthyosaura alpestris, and thirdly, to propose easy guidelines for an accurate distinction between large larvae and paedomorphs based on an external sexual trait, which is essential for reproduction — the cloaca. More than half of the studies in the literature do not mention the diagnostic criteria used for determining adulthood. The criteria mentioned were the presence of mature gonads (10%), eggs laid (4%), courtship behaviour (10%), and external morphological sexual traits (39%) including the cloaca (24%). Body-size thresholds should not be used as a proxy for paedomorphosis, because overwintering larvae can reach a larger size than paedomorphs within the same populations. In contrast, diagnosis based on cloacal external morphology is recommended, as it can be processed by the rapid visual assessment of all caught specimens, thus providing straightforward data at the individual level for both sexes. [less ▲]

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See detailThe ‘male escape hypothesis’: sex-biased metamorphosis in response to climatic drivers in a facultatively paedomorphic amphibian
Mathiron, Anthony; Lena, Jean-Paul; Baouch, Sarah et al

in Proceedings of the Royal Society B : Biological Sciences (2017), 284(1853), 20170176

Paedomorphosis is a major evolutionary process that bypasses metamorphosis and allows reproduction in larvae. In newts and salamanders, it can be facultative with paedomorphs retaining gills and ... [more ▼]

Paedomorphosis is a major evolutionary process that bypasses metamorphosis and allows reproduction in larvae. In newts and salamanders, it can be facultative with paedomorphs retaining gills and metamorphs dispersing. The evolution of these developmental processes is thought to have been driven by the costs and benefits of inhabiting aquatic versus terrestrial habitats. In this context, we aimed at testing the hypothesis that climatic drivers affect phenotypic transition and the difference across sexes because sex-ratio is biased in natural populations. Through a replicated laboratory experiment, we showed that paedomorphic palmate newts (Lissotriton helveticus) metamorphosed at a higher frequency when water availability decreased and metamorphosed earlier when temperature increased in these conditions. All responses were sex-biased, and males were more prone to change phenotype than females. Our work shows how climatic variables can affect facultative paedomorphosis and support theoretical models predicting life on land instead of in water. Moreover, because males metamorphose and leave water more often and earlier than females, these results, for the first time, give an experimental explanation for the rarity of male paedomorphosis (the ‘male escape hypothesis’) and suggest the importance of sex in the evolution of paedomorphosis versus metamorphosis. [less ▲]

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See detailRésultats des enquêtes "Attrait des Sciences" (années académiques 2015–2016 et 2016–2017)
Aerts, Stéphanie ULg; Ernst, Marie ULg

Report (2017)

Lors des rentrées académiques 2015-2016 et 2016-2017, une enquête a été envoyée aux étudiants primants inscrits en Faculté des Sciences. Cette enquête interroge les étudiants sur leur parcours secondaire ... [more ▼]

Lors des rentrées académiques 2015-2016 et 2016-2017, une enquête a été envoyée aux étudiants primants inscrits en Faculté des Sciences. Cette enquête interroge les étudiants sur leur parcours secondaire, leur choix d'étude, leur avenir professionnel et leurs aptitudes. Ce rapport consiste en une analyse descriptive et exploratoire des résultats des deux enquêtes. [less ▲]

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See detailUnexpected diversification of pliosaurid marine reptiles after the Jurassic-Cretaceous boundary
Fischer, Valentin ULg; Benson, Roger; Zverkov, Nikolay et al

Conference (2017, April)

Pliosaurids are iconic marine reptiles that dominated marine ecosystems during the Jurassic and the Cretaceous. These giant predators met their demise during the early Late Cretaceous but the final ... [more ▼]

Pliosaurids are iconic marine reptiles that dominated marine ecosystems during the Jurassic and the Cretaceous. These giant predators met their demise during the early Late Cretaceous but the final chapter of their long evolutionary history remains barely documented. Prompted by the discovery of a peculiar and very well preserved new taxon from Russia, we compute the evolution of pliosaurid disparity from their Early Jurassic radiation to their Late Cretaceous extinction. Despite a patchy Early Cretaceous fossil record, we show pliosaurids reached their maximal disparity during the Hauterivian-Barremian interval, suggesting a strong Early Cretaceous recovery from the apparently low phenotypic disparity of Late Jurassic pliosaurids. By using cladistic and ecomorphological data, we show that pliosaurids have repeatedly evolved slender-snouted polycotylid-like morphologies in each of their temporal radiations (Early Jurassic, Middle Jurassic and Early Cretaceous), demonstrating a more complex evolutionary history than their traditional representation as gigantic apex predators of Mesozoic marine ecosystems suggests. The extinction of pliosaurids during the Turonian (early Late Cretaceous) appears preceded by a late Early Cretaceous contraction of their disparity, the trajectory documented in ichthyosaurs, another successful marine reptile clade that disappeared during the Cenomanian-Turonian interval. [less ▲]

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See detail"La madone et la putain": Quand les stéréotypes de genres influencent la perception de la légalité des violences sexuelles et le traitement de la réaction sociale à l'égard des femmes
Garcet, Serge ULg

in Revue de la Faculté de Droit de l'Université de Liège (2017), 2017/1

Les illégalités liées au traitement différentiel des genres reposent notamment sur la présence de stéréotypes sexistes. L’article illustre comment les attitudes subjectivement positives à l’égard des ... [more ▼]

Les illégalités liées au traitement différentiel des genres reposent notamment sur la présence de stéréotypes sexistes. L’article illustre comment les attitudes subjectivement positives à l’égard des femmes que l’on peut qualifier de stéréotypes sexistes bienveillants influencent tant positivement que négativement la façon dont les femmes sont perçues par le système judiciaire. L’article souligne également au travers des représentations liées aux violences sexuelles l’impact des stéréotypes sexistes hostiles sur la perception de la légalité, de la légitimité perçue du passage à l’acte et du statut des victimes. [less ▲]

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