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See detailIndirect quadrangular mesh generation and validation of curved finite elements
Johnen, Amaury ULg

Doctoral thesis (2016)

Among the different types of 3D finite element meshes, hexahedral meshes present properties that can be highly desirable, such as alignment with physical features or a lower computational cost. For this ... [more ▼]

Among the different types of 3D finite element meshes, hexahedral meshes present properties that can be highly desirable, such as alignment with physical features or a lower computational cost. For this reason and despite the maturity of the tetrahedral mesh generators, hexahedral mesh generation has always been a prolific research domain. Yet, there exists currently no robust algorithm capable of generating conformal all-hexahedral meshes with prescribed input size field on any arbitrary geometry. One difficulty that remains is that there exists no method to robustly assert that a hexahedron is valid. Indeed, linear hexahedra can be folded (tangled) in the same way than curvilinear tetrahedra. This thesis addresses two subjects. First, two original quadrangular mesh generation techniques are investigated, with the aim to generalize them to 3D. Both are indirect methods and thus consider the problem of combining pairs of triangles of an initial input triangular mesh. The first technique, called Blossom-Quad, computes the optimal solution of this problem with respect to a given quality criterion. As for any indirect method, the quality of the solution strongly depends on the location of the nodes in the initial triangular mesh. The generalization to 3D is however unclear and a second technique is investigated. This one aims at computing a near-optimal solution by using a look-ahead tree technique. The corresponding algorithm allows tuning the quality of the final mesh by choosing the depth of the tree as a parameter. This technique gives a promising way forward, especially as it is directly applicable in 3D. The second subject concerns the development of a method that permits to compute, with respect to any prescribed tolerance, the extrema of Jacobian-based quantities defined on finite elements of any order and type. Applied to the Jacobian determinant, this method allows to assert the validity of any (curvi-)linear finite element. This method is also applied to a quality measure that quantifies the pointwise anisotropy of the elements. Besides being very attractive for hexahedral mesh generation, this method is especially useful for the analysis of curvilinear finite element meshes. It can moreover be an important component of optimization techniques for achieving robustness. [less ▲]

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See detailLarge elasto-optic effect and reversible electrochromism in multiferroic BiFeO3
Sando, D.; Yang, Yurong; Bousquet, Eric ULg et al

in Nature Communications (2016), 7

The control of optical fields is usually achieved through the electro-optic or acousto-optic effect in single-crystal ferroelectric or polar compounds such as LiNbO3 or quartz. In recent years, tremendous ... [more ▼]

The control of optical fields is usually achieved through the electro-optic or acousto-optic effect in single-crystal ferroelectric or polar compounds such as LiNbO3 or quartz. In recent years, tremendous progress has been made in ferroelectric oxide thin film technology—a field which is now a strong driving force in areas such as electronics, spintronics and photovoltaics. Here, we apply epitaxial strain engineering to tune the optical response of BiFeO3 thin films, and find a very large variation of the optical index with strain, corresponding to an effective elasto-optic coefficient larger than that of quartz. We observe a concomitant strain-driven variation in light absorption—reminiscent of piezochromism—which we show can be manipulated by an electric field. This constitutes an electrochromic effect that is reversible, remanent and not driven by defects. These findings broaden the potential of multiferroics towards photonics and thin film acousto-optic devices, and suggest exciting device opportunities arising from the coupling of ferroic, piezoelectric and optical responses. [less ▲]

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See detailLe poète François Jacqmin
Purnelle, Gérald ULg

Conference given outside the academic context (2016)

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See detailMediation analysis to estimate direct and indirect milk losses associated with bacterial load in bovine subclinical mammary infections
Detilleux, Johann ULg; Theron, Léonard ULg; Duprez, Jean-Noël ULg et al

in Animal (2016)

Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e. direct losses) or to effects of the immune response triggered by the presence of mammary pathogens (i.e ... [more ▼]

Milk losses associated with mastitis can be attributed to either effects of pathogens per se (i.e. direct losses) or to effects of the immune response triggered by the presence of mammary pathogens (i.e. indirect losses). Test-day milk somatic cell counts (SCC) and number of bacterial colony forming units (CFU) found in milk samples are putative measures of the level of immune response and of the bacterial load, respectively. Mediation models, in which one independent variable affects a second variable which, in turn, affects a third one, are conceivable models to estimate direct and indirect losses. Here, we evaluated the feasibility of a mediation model in which test-day SCC and milk were regressed toward bacterial CFU measured at three selected sampling dates, 1 week apart. We applied this method on cows free of clinical signs and with records on up to 3 test-days before and after the date of the first bacteriological samples. Most bacteriological cultures were negative (52.38%), others contained either staphylococci (23.08%), streptococci (9.16%), mixed bacteria (8.79%) or were contaminated (6.59%). Only losses mediated by an increase in SCC were significantly different from null. In cows with three consecutive bacteriological positive results, we estimated a decreased milk yield of 0.28 kg per day for each unit increase in log2-transformed CFU that elicited one unit increase in log2-transformed SCC. In cows with one or two bacteriological positive results, indirect milk loss was not significantly different from null although test-day milk decreased by 0.74 kg per day for each unit increase of log2-transformed SCC. These results highlight the importance of milk losses that are mediated by an increase in SCC during mammary infection and the feasibility of decomposing total milk loss into its direct and indirect components. © The Animal Consortium 2016 [less ▲]

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See detailGalectin-1 is involved in osteoclast biology
Muller, Joséphine ULg; Binsfeld, Marilène ULg; DUBOIS, Sophie ULg et al

Poster (2016, February 28)

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See detailMesure de l’efficacité d’un protocole d’entraînement sur l’amélioration de la vitesse chez des joueurs de football
Lombard, Gilles ULg; Clerc, Etienne

Poster (2016, February 27)

Introduction L’organisation défensive des équipes de football et la densité des joueurs ont significativement augmenté depuis 40 ans (Wallace et Norton, 2014). Ceci influence les qualités physiques des ... [more ▼]

Introduction L’organisation défensive des équipes de football et la densité des joueurs ont significativement augmenté depuis 40 ans (Wallace et Norton, 2014). Ceci influence les qualités physiques des joueurs qui se doivent d’être plus rapides pour faire la différence. Aujourd’hui, la filière anaérobie alactique, bien que minoritaire au niveau quantitatif (Mohr et al., 2003), est la déterminante principale de la performance sur le plan physique (Cometti et al., 2001). Etant donné l’importance de cette qualité physique, nous avons voulu examiner si l’introduction d’un travail spécifique de la vitesse durant 8 semaines aurait un impact significatif sur la performance fonctionnelle du joueur de football. Méthodologie L’échantillon de 18 joueurs est réparti dans des groupes contrôle et expérimental. Trois tests de terrain sont utilisés pour mesurer l’évolution du paramètre anaérobique avant et après le protocole de 8 semaines : un test de vitesse sur 10 mètres (Wilson et al., 1993), un test de zigzags sur 20 mètres (Little et Williams, 2005) et un counter movement jump avec les bras (Slinde et al., 2008). Durant 8 semaines, le groupe expérimental bénéficie, en plus de l’entraînement normal, de deux séances hebdomadaire de 30 minutes visant le développement de la vitesse. Resultats L’étude étant toujours en cours, nous ne disposons pas encore de résultats. Nous espérons observer une amélioration significative des performances dans les trois tests grâce à l’amélioration, entre autre, de la vitesse gestuelle et de la force spécifique des appuis (Cometti, 2006). Néanmoins, nous nous attendons à ce que l’amélioration soit plus importante au niveau des tests zigzags et counter movement jump de par l’influence importante des masses musculaires et l’impact réduit du temps de réaction par rapport au sprint sur 10 mètres. Conclusion Nous espérons que ce protocole se révélera efficace dans l’amélioration des performances car il serait intéressant de disposer d’un outil améliorant les qualités de vitesse des joueurs dans une période de temps assez courte pour ne pas empiéter sur l’entraînement technico-tactique. [less ▲]

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See detailL’ACCOUTUMANCE À L’EAU, UN PASSAGE OBLIGÉ AVANT LA NATATION ?
Mornard, Manhattan ULg; Delvaux, Anne ULg; Delsupexhe, Nadège et al

Poster (2016, February 27)

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See detailEDUCATION RACHIDIENNE : DE L’ENFANT AU SPORTIF DE HAUT NIVEAU
Vanderthommen, Marc ULg; GROSDENT, Stéphanie ULg; Fettweis, Tatiana ULg et al

in Livre des Résumés du 2ème Colloque Guy Namurois (2016, February 27)

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See detailIntérêt d’un modèle de compétition adapté aux enfants en athlétisme : le Kid’s Athletics
Jidovtseff, Boris ULg; Wuillaume, Sandrine; Cloes, Marc ULg

Poster (2016, February 27)

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See detailSPÉCIALISATION SPORTIVE PRÉCOCE : QUEL IMPACT SUR LA PERFORMANCE, SUR LE DÉVELOPPEMENT ET SUR LA SANTÉ ET QUELLES PISTES DE SOLUTION ?
Jidovtseff, Boris ULg

in Jidovtseff; Halleux, Philippe; Lambert, Eric (Eds.) Livre des résumés du 2ème colloque Guuy Namurois (de l'éducation physique à la performance sportive) (2016, February 27)

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See detailFrom Valeriana officinalis to cancer therapy: the success of a bio-sourced compound
Hamaïdia, Malik ULg; Barez, Pierre-Yves ULg; Carpentier, Alexandre ULg et al

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment (2016), 20

Over the centuries, bio-sourced compounds isolated from plants, insects and microorganisms have been a potent source of drugs for the treatment of human diseases. In this review, we recapitulate the story ... [more ▼]

Over the centuries, bio-sourced compounds isolated from plants, insects and microorganisms have been a potent source of drugs for the treatment of human diseases. In this review, we recapitulate the story of one of these compounds, 2-propylpentanoic acid, derived from the Valeriana officinalis flowering plant and its path to validation as a cancer treatment. [less ▲]

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See detailDes sœurs et des religieuses au service du corps souffrant, 17e – 18e s.
Henneau, Marie-Elisabeth ULg

Conference given outside the academic context (2016)

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See detailAnnual dynamics of pCO2 within bulk sea ice and related CO2 fluxes at Cape Evans (Antarctica)
Van Der Linden, Fanny ULg; Champenois, Willy ULg; Heinesch, Bernard ULg et al

Poster (2016, February 26)

Sea ice is a biome actively participating in the regional cycling of CO2 as both a source and a sink at different times of the year. In the frame of the YROSIAE project (Year-Round Ocean-Sea-Ice ... [more ▼]

Sea ice is a biome actively participating in the regional cycling of CO2 as both a source and a sink at different times of the year. In the frame of the YROSIAE project (Year-Round Ocean-Sea-Ice-Atmosphere Exchanges), annual dynamics of sea ice pCO2 was compared with CO2 fluxes measured by automated accumulation chambers at Cape Evans (Ross Island, Antarctica). Results confirmed a general trend of brine pCO2 supersaturation with respect to the atmosphere during the late winter (concentration of dissolved inorganic carbon - DIC - in brine and brine expulsion in the brine skim) leading to CO2 degassing, and undersaturation during the spring (carbon-uptake by autotrophs and brine dilution) leading to atmospheric CO2 uptake. Despite high primary production at the bottom of the ice in spring, DIC profiles suggest that sea ice as a whole appears to be net heterotrophic. Still, sea ice absorbs CO2 from the atmosphere, as a result of physical processes. Some variability in the CO2 fluxes (both in magnitude and sign) could not be explained by variability in sea ice pCO2 but rather seemed driven by variability in atmospheric conditions and sea ice surface properties. For instance, in late spring, CO2 fluxes showed a diurnal variability (from CO2 degassing to uptake) related to atmospheric temperature variations. Large and episodic CO2 fluxes were systematically positively correlated with strong wind events, and large CO2 degassing was observed over thin, wet and salty snow cover. [less ▲]

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See detailLower Carboniferous shallow marine sequences from the Central Alborz Basin, Iran (north-eastern margin of Gondwana): sedimentology, biostratigraphy and rock– magnetic studies
Sardar Abadi, Mehrdad ULg

Doctoral thesis (2016)

The Lower Carboniferous Mobarak Formation records the development of a carbonate platform on the southern Paleo-Tethyan passive margin. This pervasive carbonate factory was deposited following the opening ... [more ▼]

The Lower Carboniferous Mobarak Formation records the development of a carbonate platform on the southern Paleo-Tethyan passive margin. This pervasive carbonate factory was deposited following the opening of the Paleo-Tethys Ocean into the Alborz Basin along the northern margin of Gondwana. The depositional facies range from the most proximal to the most distal and include coastal environments, inner ramp peritidal facies, peloidal to crinoidal shoals, storm to fair-weather influenced mid-ramps, proximal to distal shell beds and low energy outer ramps. Storms clearly played a dominant role in the distribution of skeletal and non-skeletal shoals on the carbonate ramp. Sedimentological analyses complemented with foraminiferal biostratigraphy reveal four events which are interpreted to represent the principal factors controlling carbonate platform evolution in the Alborz Basin during the Lower Carboniferous: 1) A transgression linked to global temperature rise in the Early Tournaisian (Middle Hastarain) resulted in the formation of thick-bedded argillaceous limestones. 2) the Hastarian–Ivorian boundary glaciation phase, 3) Upper Ivorian–Lower Viséan? tectonic block faulting. 4) the Viséan- Serpukhovian glaciation phase. The three foraminiferal assemblages encountered in the Tournaisian interval of the Mobarak Formation are restricted to specific periods within the Ivorian. The occurrence of specific foraminiferal taxa in Alborz is tightly governed by transgressions and migration of North Paleo–Tethyan biotic elements as response to the thermal period. We also combined proxies for ambient paleothermometry in addition to the indications for arid conditions and arid conditions and the presence of foraminiferal taxa with a North Paleo-Tethyan affinity in the Lower Carboniferous Mobarak Formation to suggest a paleo-position for the Alborz Basin at lower latitudes than approximately 45  –50  southern paleolatitude reported thus far. Magnetic susceptibility ( in ) was measured and compared with facies from the same sample. There is a clear link between  in and facies, and the average  in values are higher for distal facies than for proximal ones. The  in profile of Lower Carboniferous carbonate sequence reflects stratigraphic variations in response to relative sea level changes and detrital input. In the context of the sequence stratigraphic framework, the average  in values for lowstand and transgressive system tracts deposits are higher than for the highstand system tracts deposits. The clear link between  in and facies points to at least partly preserved primary  in signal, related to detrital inputs. In respect to the hysteresis measurements the in signal is mainly carried by low coercivity ferromagnetic minerals such as magnetite, with a mixture of relatively coarse grains (detrital fraction) and ultra-fine grains (probably formed during diagenesis). [less ▲]

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See detailDen Blick auf den Punkt bringen. Ästhetisch-narrative Betrachtungen zu Christian Schwochows Westen.
Hamers, Jérémy ULg

Scientific conference (2016, February 26)

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See detailNitrous oxide dynamics in sea ice
Kotovitch, Marie ULg; Fripiat, François ULg; Moreau, Sébastien et al

Conference (2016, February 26)

Fluctuations in greenhouse gases (GHGs) concentration alter the energetic budget of the climate system. There is high confidence that natural systems related to snow, ice and frozen ground (including ... [more ▼]

Fluctuations in greenhouse gases (GHGs) concentration alter the energetic budget of the climate system. There is high confidence that natural systems related to snow, ice and frozen ground (including permafrost) are affected. Nitrous oxide (N2O) is one of the potent GHG naturally present in the atmosphere, but witch has seen his concentration growing since industrial era. N2O has a lifetime in the atmosphere of 114 years and a global warming potential (GWP) of 298 to be compared to carbon dioxide that has a GWP of 1. N2O is also describe as the dominant ozone-depleting substance emitted in the 21st Century. Yet, there are still large uncertainties and gaps in the understanding of the cycle of this compound through the ocean and particularly in sea ice. Sources and sinks of N2O are therefore still poorly quantified. The main processes (with the exception of transport processes) involved in the N2O cycle within the aquatic environment are nitrification and denitrification. To date, only one study by Randall et al. present N2O measurements in sea ice. Randall et al. pointed out that sea ice formation and melt has the potential to generate sea-air or air-sea fluxes of N2O, respectively. [less ▲]

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See detailParticipation à la conférence/débat "Conspirationnisme et pensée critique"
Hamers, Jérémy ULg

Conference given outside the academic context (2016)

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See detailUn manuscrit de l’entourage de Noël Bellemare sous le microscope : analyse du ms. W 29 de l’Université de Liège
Oger, Cécile ULg; L'Estrange, Elizabeth; Gilbert, Bernard ULg et al

Conference (2016, February 26)

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