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See detailContribution expérimentale à l’étude des désordres du couplage ventriculo-aortique
Kolh, Philippe ULiege

Post doctoral thesis (2006)

Detailed reference viewed: 16 (2 ULiège)
See detailContribution fondamentale et clinique à l'exploration musculaire isocinétique
Croisier, Jean-Louis ULiege

Post doctoral thesis (2002)

Detailed reference viewed: 143 (18 ULiège)
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See detailContribution functions and the depths of formation of spectral lines
Magain, Pierre ULiege

in Astronomy and Astrophysics (1986), 163

A rigorous expression is derived for the contribution function to the spectral line depression in a stellar atmosphere; this, in effect, gives the contribution of the different atmospheric layers to the ... [more ▼]

A rigorous expression is derived for the contribution function to the spectral line depression in a stellar atmosphere; this, in effect, gives the contribution of the different atmospheric layers to the formation of the line depression. This contribution function is the solution of the transfer equation for the line depression. It is the only appropriate distribution function for the computation of the depths of formation of spectral lines. It indicates, in contrast to some earlier contribution functions, that a faint spectral line is not necessarily formed in the same layers as the continuum. The response function of the line depression to a given perturbation is briefly discussed. [less ▲]

Detailed reference viewed: 27 (5 ULiège)
See detailContribution future du bilan de masse de surface Antarctique au niveau des mers par la modélisation régionale
Agosta, Cécile ULiege; Fettweis, Xavier ULiege; Gallée, Hubert

Scientific conference (2013, October 15)

Le bilan de masse de surface (BMS) Antarctique est encore mal connu, bien qu’on sache qu’il contribue de façon significative à l’évolution actuelle du niveau des mers et que sa contribution soit ... [more ▼]

Le bilan de masse de surface (BMS) Antarctique est encore mal connu, bien qu’on sache qu’il contribue de façon significative à l’évolution actuelle du niveau des mers et que sa contribution soit supposée s’intensifier au cours des prochains siècles. Outre son effet direct sur le niveau des mers, le BMS est également un champs de forçage primordial pour les modèles de calotte. Enfin, alors qu’il existe des mesures directes de l’écoulement de la glace vers l’océan et des variations de masse totales (surface+écoulement) de la calotte, il n’existe pas de mesure directe du bilan de masse de surface à l’échelle du continent. La climatologie actuelle du BMS Antarctique est donc estimée principalement à partir de résultats de modélisation. Par ailleurs, le BMS est le résultat de processus complexes. Afin de le modéliser correctement, il est nécessaire de bien représenter la circulation atmosphérique et les processus physiques spécifiques aux régions polaires. Or les modèles de circulation générale présentent une résolution trop grossière et une physique peu adaptée pour modéliser correctement ces processus. Nous présentons ici des résultats de simulations réalisées le modèle atmosphérique régional MAR, qui fait référence pour la modélisation de l’atmosphère et des processus de surface en région polaire, à une résolution de 50 km pour la fin du 20ème et du 21ème siècle. Nous connaissons la qualité du modèle MAR, cependant, comme tout modèle atmosphérique régional, ses performances sont fortement liées à la qualité des forçages aux limites provenant des Modèles de Circulation Générale (MCG). Nous avons donc sélectionné le MCG le plus apte à simuler le climat présent parmi la nouvelle génération des MCGs provenant de la base de données CMIP5 (http://cmip- pcmdi.llnl.gov/cmip5/), qui seront utilisés dans le prochain rapport du GIEC. Cela est une étape cruciale car les MCGs ne représentant pas correctement le climat présent ne pourront pas donner de résultats probants pour les simulations futures. Nous nous penchons enfin sur l’épineux problème de l’évaluation du BMS modélisé à partir de données de terrain. En effet, un effort important a été réalisé pour répertorier les données de BMS de qualité en Antarctique, cependant nous montrons que ces données ne permettent pas d’évaluer les performances des modèles de façon suffisamment contraignante. L’utilisation d’autres types de données, satellites ou aéroportées par exemple, semble nécessaire, ce qui constitue un volet important de mes recherches en cours. [less ▲]

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See detailContribution méthodologique à l'évaluation de la qualité des eaux des revières à l'aide des macrophytes aquatiques(spermatophytes et bryophytes) - Application au réseau hydrographique luxembourgeois-
Sossey Alaoui, Khadija ULiege

Doctoral thesis (2006)

La répartition des Macrophytes aquatiques (Phanérogames et Bryophytes) a été étudiée sur l’ensemble des cours d’eau luxembourgeois. Des prospections macrophytiques ont été réalisées pour 340 stations ... [more ▼]

La répartition des Macrophytes aquatiques (Phanérogames et Bryophytes) a été étudiée sur l’ensemble des cours d’eau luxembourgeois. Des prospections macrophytiques ont été réalisées pour 340 stations entre 2000 et 2003. Dans chacune d’entre elles, des paramètres mésologiques ont été mesurés et des analyses physico-chimiques des eaux ont été effectuées dans 63% des stations. La relation macrophytes-habitat a été envisagée selon deux approches : multidimensionnelle d’une part et par des profils écologiques d’autre part. Les principales espèces aquatiques et semi-aquatiques des rivières luxembourgeoises ont été classées en différents groupes par une Analyse Factorielle Multiple (AFM) sur base des descripteurs physico-chimiques et morpho-métriques impliqués dans la dispersion, l’établissement et la persistance des espèces aquatiques. Basée sur l’abondance de ces groupements, une typologie floristique des cours d’eau a conduit à l’individualisation de différents groupes de stations : 1 les têtes de bassins ardennais caractérisées par Chiloscyphus pallescens et C. polyanthos ainsi que par un éclairement faible et un substrat grossier ; 2 les cours principaux de l’Oesling à Ranunculus penicillatus, R. peltatus ; 3 Berula erecta et Veronica beccabunga caractérisent les zones amonts du Gutland dont les eaux montrent des teneurs élevées en nitrates ; 4 les cours principaux lorrains dont les eaux sont plus minéralisés et riches en SO42- sont caractérisés par P. crispus, E. canadensis, P. natans et Z. palustris ; 5 et finalement les zones fortement eutrophisées (rithrons) caractérisées par un grand nombre d’espèces (Potamogeton pectinatus, P. perfoliatus, Sparganium emersum….) et par des critères morpho-métriques très importants (profondeur, éclairement, largeur et température). Des profils écologiques et des cartes de distributions des principales espèces rencontrées (Phanérogames et Bryophytes) nous ont permis de délimiter leurs comportements vis a vis de l’eutrophisation et de la minéralisation. Les différences observées par rapport à la littérature témoignent d’une prolifération des espèces polluo-tolérantes d’une part et d’une pression anthropique importante le long du réseau hydrographique luxembourgeois d’autre part. Une méthode indicielle a été appliquée afin d’évaluer la qualité des rivières sur base des espèces inventoriées. Néanmoins, la faible occurrence des espèces et la non prise en compte des algues ont diminué l’acuité de la méthode. L’importance des formations végétales riveraines au seins des écosystèmes aquatiques et plus particulièrement dans le domaine de la bioindication a été étudiée également. Le pouvoir bioindicateur pour les facteurs acidité, azote, humidité, et lumière (ELLENBERG et al., 1992) a été précisé pour 220 espèces rivulaires inventoriées le long des sites de l’Oesling et du Gutland. Une typologie des biotopes riverains a été dégagée sur base de ces valeurs bioindicatrices. Le déterminisme de la richesse des sols riverains a été envisagé dans sa composante naturelle Oesling-Gutland, ainsi que dans sa composante anthropique. [less ▲]

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See detailContribution of "click chemistry" to the macromolecular engineering of aliphatic polyesters
Riva, Raphaël ULiege; Schmeits, Stephanie ULiege; Croisier, Florence ULiege et al

Poster (2010, July 13)

In this work, click chemistry was sucessfully applied to the chemical modification of aliphatic polyesters with the purpose to tailor their physical properties. The developped strategy was then applied to ... [more ▼]

In this work, click chemistry was sucessfully applied to the chemical modification of aliphatic polyesters with the purpose to tailor their physical properties. The developped strategy was then applied to the synthesis of materials, such as smart partially degradable hydrogels or antibacterial polyesters. Last, the synthesis of amphiphilic star-shaped copolyester was investigated. [less ▲]

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See detailContribution of "click chemistry" to the synthesis of antimicrobial aliphatic copolyester
Riva, Raphaël ULiege; Lussis, Perrine ULiege; Lenoir, Sandrine ULiege et al

in Polymer (2008), 49(8), 2023-2028

A straightforward strategy is proposed to impart antimicrobial properties to biodegradable poly(oxepan-2-one) (poly(epsilon-caprolactone) or PCL), which is based on the grafting of pendant ammonium salts ... [more ▼]

A straightforward strategy is proposed to impart antimicrobial properties to biodegradable poly(oxepan-2-one) (poly(epsilon-caprolactone) or PCL), which is based on the grafting of pendant ammonium salts by "click" chemistry. First, statistical copolymerization of 3-chlorooxepan-2-one (alpha-chloro-epsilon-caprolactone or alpha Cl epsilon CL) with oxepan-2-one (epsilon-caprolactone or epsilon CL) was initiated by 2,2-dibutyl-2-stanna-1,3-dioxepane (DSDOP). In a second step, pendant chlorides were converted into azides by reaction with sodium azide (NaN3). Finally, quaternary ammonium containing alkynes were quantitatively added to the pendant azide groups of PCL by the copper-catalyzed Huisgen's 1,3-dipolar cycloaddition, which is a typical "click" reaction. An alternative two-step strategy based on the cycloaddition of the amine containing alkyne onto the pendant azides, followed by quaternization turned out to be less efficient. The antimicrobial activity was analyzed by the "shaking flask method" in the presence of Escherichia coli [less ▲]

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See detailContribution of "click" chemistry to the functionalization of aliphatic polyesters
Schmeits, Stephanie ULiege; Riva, Raphaël ULiege; Zednik, Jiri et al

Poster (2007, August 31)

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See detailThe contribution of 211 particles to the mechanical reinforcement mechanism of 123 superconducting single domains
Mathieu, Jean-Philippe; Cano, I. G.; Koutzarova, T. et al

in Superconductor Science and Technology (2004), 17(1), 169-174

Hardness and fracture toughness of Dy-123 single domains were studied by Vickers in micro-indentation. A significant anisotropy of the mechanical properties was observed. Hardness tests give higher values ... [more ▼]

Hardness and fracture toughness of Dy-123 single domains were studied by Vickers in micro-indentation. A significant anisotropy of the mechanical properties was observed. Hardness tests give higher values when performed in (001) planes rather than in planes parallel to the c-axis. Moreover, the cracks pattern around the indentation follows preferential orientation in planes parallel to the c-axis whereas a classical 'four-cracks' pattern is observed in the (001) planes. It has been possible to show the crucial role played by the 211 particles in the deviating mechanism of cracks and the relevance of the high homogeneity of 211-particle distribution in the material. [less ▲]

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See detailContribution of a Dense Population of the Brittle Star Acrocnida brachiata (Montagu) to the Biogeochemical Fluxes of CO2 in a Temperate Coastal Ecosystem
Davoult, D.; Harlay, Jérôme ULiege; Gentil, F.

in Estuaries and Coasts (2009), 32(6), 1103-1110

The production of organic matter and calcium carbonate by a dense population of the brittle star Acrocnida brachiata (Echinodermata) was calculated using demographic structure, population density, and ... [more ▼]

The production of organic matter and calcium carbonate by a dense population of the brittle star Acrocnida brachiata (Echinodermata) was calculated using demographic structure, population density, and relations between the size (disk diameter) and the ash-free dry weight (AFDW) or the calcimass. During a 2-year survey in the Bay of Seine (Eastern English Channel, France), organic production varied from 29 to 50 g(AFDW) m(-2) year(-1) and CaCO3 production from 69 to 104 g(CaCO3) m(-2) year(-1). Respiration was estimated between 1.7 and 2.0 mol(CO2) m(-2) year(-1). Using the molar ratio (psi) of CO2 released: CaCO3 precipitated, this biogenic precipitation of calcium carbonate would result in an additional release between 0.5 and 0.7 mol(CO2) m(-2) year(-1) that represented 23% and 26% of total CO2 fluxes (sum of calcification and respiration). The results of the present study suggest that calcification in temperate shallow environments should be considered as a significant source of CO2 to seawater and thus a potential source of CO2 to the atmosphere, emphasizing the important role of the biomineralization (estimated here) and dissolution (endoskeletons of dead individuals) in the carbon budget of temperate coastal ecosystems. [less ▲]

Detailed reference viewed: 28 (3 ULiège)
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See detailContribution of a new active faults map and sedimentary cores to the characterization of seismogenic sources in an interdisciplinary approach (Western Gulf of Corinth, Greece)
Beckers, Arnaud ULiege; Hubert, Aurelia ULiege; Beck, Christian et al

Conference (2014, April 28)

The Corinth rift is one of the fastest spreading rifts on Earth. 5 earthquakes of magnitude greater than 5.8 occurred during the last 40 years. The question of seismic hazard is consequently particularly ... [more ▼]

The Corinth rift is one of the fastest spreading rifts on Earth. 5 earthquakes of magnitude greater than 5.8 occurred during the last 40 years. The question of seismic hazard is consequently particularly relevant. Despite a long earthquake catalogue, estimations of earthquake hazard remain problematic because of the difficulty to associate each historical event to one of the many active faults mapped in the area. Consequently, combining seismology, history and paleoseismology in an interdisciplinary approach is here necessary and is the goal of the ANR-SISCOR project. In this framework, we investigated the offshore sediments in order to (1) better constraint the length of the active offshore faults, and (2) look for sedimentary signature of historical earthquakes. 600 km of high resolution seismic reflexion data have been acquired during two surveys and 12 short gravity cores have been retrieved. The latters are 0.5 to 1 m long, allowing us to analyze about 500 yrs of sedimentation. Two new faults potentially able to trigger M>5.5 earthquakes have been mapped in the northern part of the gulf based on seismic data. Sedimentary events (turbidites and mud flows) have been identified in some cores, essentially in the deep basin and in a 180m-deep sub-basin close to the northern coast. The comparison with the critically reviewed historical records shows that some of these events could have been triggered by historical earthquakes. The link between these potential earthquakes sedimentary signatures, historical events and active faults is discussed based on intensity maps and our new active fault map. [less ▲]

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See detailContribution of a Trunk Accelerometer System to the Characterization of Gait in Patients With Mild-to-Moderate Parkinson’s Disease
Demonceau, Marie ULiege; Donneau, Anne-Françoise ULiege; CROISIER, Jean-Louis ULiege et al

in IEEE Journal of Biomedical and Health Informatics (2015)

OBJECTIVE: Gait disturbances like shuffling and short steps are obvious at visual observation in patients with advanced Parkinson's disease (PD). However, quantitative methods are increasingly used to ... [more ▼]

OBJECTIVE: Gait disturbances like shuffling and short steps are obvious at visual observation in patients with advanced Parkinson's disease (PD). However, quantitative methods are increasingly used to evaluate the wide range of gait abnormalities that may occur over the disease course. The goal of this study was to test the ability of a trunk accelerometer system to quantify the effects of PD on several gait features when walking at self-selected speed. METHODS: We recruited 96 subjects split into three age-matched groups: 32 healthy controls (HC), 32 PD patients at Hoehn and Yahr stage < II (PD-1), and 32 patients at Hoehn & Yahr stage II-III (PD-2). The following outcomes were extracted from the signals of the tri-axial accelerometer worn on the lower back: stride length, cadence, regularity index, symmetry index and mechanical powers yielded in the cranial-caudal, antero-posterior and medial-lateral directions. Walking speed was measured using a stopwatch. RESULTS: beside other gait features, the PD-1 and the PD-2 groups showed significantly reduced stride length normalized to height (p<0.02) and symmetry index (p<0.009) in comparison to the HC. Regularity index was the only feature significantly decreased in the PD-2 group as compared with the two other groups (p<0.01). The clinical relevance of this finding was supported by significant correlations with mobility and gait scales (r is around -0.3; p<0.05). CONCLUSION: Gait quantified by a trunk accelerometer may provide clinically useful information for the screening and follow-up of PD patients. [less ▲]

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See detailContribution of a tyrosine-based motif to cellular trafficking of wild-type and truncated NPY Y(1) receptors.
Lecat, Sandra; Ouedraogo, Moussa; Cherrier, Thomas ULiege et al

in Cellular Signalling (2011), 23(1), 228-38

The human NPY Y(1) receptor undergoes fast agonist-induced internalization via clathrin-coated pits then recycles back to the cell membrane. In an attempt to identify the molecular determinants involved ... [more ▼]

The human NPY Y(1) receptor undergoes fast agonist-induced internalization via clathrin-coated pits then recycles back to the cell membrane. In an attempt to identify the molecular determinants involved in this process, we studied several C-terminal truncation mutants tagged with EFGP. In the absence of agonist, Y(1) receptors lacking the last 32 C-terminal amino acids (Y(1)Delta32) are constitutively internalized, unlike full-length Y(1) receptors. At steady state, internalized Y(1)Delta32 receptors co-localize with transferrin, a marker of early and recycling endosomes. Inhibition of constitutive internalization of Y(1)Delta32 receptors by hypertonic sucrose or by co-expression of Rab5aS34N, a dominant negative form of the small GTPase Rab5a or depletion of all three isoforms of Rab5 indicates the involvement of clathrin-coated pits. In contrast, a truncated receptor lacking the last 42 C-terminal amino acids (Y(1)Delta42) does not constitutively internalize, consistent with the possibility that there is a molecular determinant responsible for constitutive internalization located in the last 10 amino acids of Y(1)Delta32 receptors. We show that the agonist-independent internalization of Y(1)Delta32 receptors involves a tyrosine-based motif YXXPhi. The potential role of this motif in the behaviour of full-length Y(1) receptors has also been explored. Our results indicate that a C-terminal tyrosine-based motif is critical for the constitutive internalization of truncated Y(1)Delta32 receptors. We suggest that this motif is masked in full-length Y(1) receptors which do not constitutively internalize in the absence of agonist. [less ▲]

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See detailThe contribution of air-fluidization to the mobility of rapid flowslides
Stilmant, Frédéric; Dewals, Benjamin ULiege; Archambeau, Pierre ULiege et al

Conference (2016, April)

Air-fluidization can be the origin of the long runout of gravitational flows involving fine particles such as ash. An excessive air pore pressure dramatically reduces the friction angle of the material as ... [more ▼]

Air-fluidization can be the origin of the long runout of gravitational flows involving fine particles such as ash. An excessive air pore pressure dramatically reduces the friction angle of the material as long as this pressure has not been dissipated, which occurs during the flow. This phenomenon can be modelled thanks to the 2D depth-averaged equations of mass and momentum conservation and an additional transport equation for basal pore pressure evolu- tion (Iverson and Denlinger, 2001). ln this contribution, we discuss the application of this model in relation to recent experimental results on air- fluidized flows by Roche et al. (2008) and Roche (2012). The experimental results were used to set a priori the value of the diffusion coefficient in the model, taking into account the diference of scale between the experiments and real-world applications. We also compare the model predictions against detailed observations of a well-documented historical event, the collapse of a fly-ash heap in Belgium (Stilmant et al., 2015). In particular, we analyse the influence of the different components of the model on the results (pore pressure dissipation vs. pore pressure generation). The diffusion coefficient which characterizes the dissipation of air pore pressure is found sufficiently low for maintaining a fluidized flow over hundreds of meters. The study concludes that an air-tluidization theory is consistent with the field observations. These findings are particularly interesting as they seem not in line with the mainstream acceptation in landslide modelling that air generally plays a secondary role (e.g., Legros, 2002). [less ▲]

Detailed reference viewed: 50 (1 ULiège)