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See detailStructure des communautés de plantes herbacées sur les Grands Causses : Stratégies fonctionnelles des espèces et interactions interspécifiques
Fayolle, Adeline ULg

Doctoral thesis (2008)

Plant community response to grazing management was studied on the INRA La Fage experimental station, Larzac Causse. Land use practices were considered as a disturbance and resource filter that remove ... [more ▼]

Plant community response to grazing management was studied on the INRA La Fage experimental station, Larzac Causse. Land use practices were considered as a disturbance and resource filter that remove species. The integrated approach of community structure used in this study was centred on plant functional traits. Continuous variations of plant traits associated with resource acquisition and early phenology indicated the replacement of stress tolerant species by ruderals along the gradient of land use intensity (grazing avoidance). Graminoids were particularly abundant in these communities. Changes in species identity and species functional identity were consistent with the grazing tolerance strategy. At the community scale, the strong functional convergence among dominant species confirmed the filtering effect of grazing management on these traits. Species richness reached its maximum at intermediate grazing. Maximal richness was associated with the coexistence of many growth forms and an important functional richness. These results are interpreted as an extension of the intermediate disturbance hypothesis to the traits of coexisting species. Finally, plant interaction dynamics experienced by five target species allowed us to identify the tendency of facilitated survival and intensely depressed biomass. The effect of communities was roughly similar although huge differences in specific and functional structure. The response to the least from competition and benefited the most from facilitation. [less ▲]

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See detailComparison of 2D turbulence models for steady flows computation in a macro-rough channel
Erpicum, Sébastien ULg; Meile, Tobias; Dewals, Benjamin ULg et al

in 2nd International Symposium on Shallow Flows (2008, December 11)

A 2D numerical flow model, developed at the Laboratory of Hydrology, Applied Hydrodynamics and Hydraulic Constructions (HACH) at ULg, has been applied to flows in a macro-rough channel using three ... [more ▼]

A 2D numerical flow model, developed at the Laboratory of Hydrology, Applied Hydrodynamics and Hydraulic Constructions (HACH) at ULg, has been applied to flows in a macro-rough channel using three different approaches to compute the turbulence effects. Both the first and second ones are based on algebraic expressions of the turbulent viscosity, and the third one uses a depth-integrated k- type model involving two additional partial differential equations. Data for the comparison have been provided by experiments conducted at the Laboratory of Hydraulic Constructions (LCH) at EPFL, showing different two-dimensional flow characteristics in varied configurations of large scale cavities in depressions at the side walls of the flume. Despite the strongly different modeling approaches used in the three models to handle the turbulence effects, the numerical models give generally similar and satisfactory agreement between experimental and numerical results regarding backwater curves. [less ▲]

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See detailComment aider au redémarrage des entrepreneurs de seconde chance ?
Van Caillie, Didier ULg; Crutzen, Nathalie ULg

Scientific conference (2008, December 10)

This document presents key elements to understand the context in which restarting entrepreneurs are operating and to identify some measures Public Authorities may launch for assisting and sustaining ... [more ▼]

This document presents key elements to understand the context in which restarting entrepreneurs are operating and to identify some measures Public Authorities may launch for assisting and sustaining restarters. [less ▲]

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See detailApproche physiopathologique du nouveau-né et de l'enfant en soins intensifs
Battisti, Oreste ULg

Scientific conference (2008, December 10)

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See detailOUFTI-1, the first student nanosatellite of Belgium
Pisane, Jonathan ULg

Speech/Talk (2008)

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See detailImpact of cyclic hypoxia on HIF-1a regulation in endothelial cells: new insights for anti-tumor treatments
Martinive, Philippe ULg

in FEBS Journal (2008)

Impact of cyclic hypoxia on HIF-1alpha regulation in endothelial cells - new insights for anti-tumor treatments.Martinive P, Defresne F, Quaghebeur E, Daneau G, Crokart N, Grégoire V, Gallez B, Dessy C ... [more ▼]

Impact of cyclic hypoxia on HIF-1alpha regulation in endothelial cells - new insights for anti-tumor treatments.Martinive P, Defresne F, Quaghebeur E, Daneau G, Crokart N, Grégoire V, Gallez B, Dessy C, Feron O. Unit of Pharmacology and Therapeutics, Université catholique de Louvain, Brussels, Belgium. Heterogeneities in tumor blood flow are associated with cyclic changes in pO(2) or cyclic hypoxia. A major difference from O(2) diffusion-limited or chronic hypoxia is that the tumor vasculature itself may be directly influenced by the fluctuating hypoxic environment, and the reoxygenation phases complicate the usual hypoxia-induced phenotypic pattern. Here, we determined the cyclic hypoxia-driven pathways that modulate hypoxia inducible factor (HIF)-1alpha abundance in endothelial cells to identify possible therapeutic targets. We found that exposure of endothelial cells to cycles of hypoxia/reoxygenation led to accumulation of HIF-1alpha during the hypoxic periods and the phosphorylation of protein kinase B (Akt), extracellular regulated kinase (ERK) and endothelial nitric oxide synthase (eNOS) during the reoxygenation phases. We identified stimulation of mitochondrial respiration and activation of the phosphoinositide-3 kinase (PI3K)/Akt pathway during intervening reoxygenation periods as major triggers of the stabilization of HIF-1alpha. We also found that the NOS inhibitor nitro-l-arginine methyl ester further stimulated the cyclic hypoxia-driven HIF-1alpha accumulation and the associated gain in endothelial cell survival, thereby mirroring the effects of a PI3K/Akt inhibitor. However, combination of both drugs resulted in a net reduction in HIF-1alpha and a dramatic in decrease in endothelial cell survival. In conclusion, this study identified cyclic hypoxia, as reported in many tumor types, as a unique biological challenge for endothelial cells that promotes their survival in a HIF-1alpha-dependent manner through phenotypic alterations occurring during the reoxygenation periods. These observations also indicate the potential of combining Akt-targeting drugs with anti-angiogenic drugs, in particular those interfering with the NO pathway. PMID: 19077164 [PubMed - as supplied by publisher [less ▲]

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See detailComment évaluer les effets de l'éducation ?
Vandoorne, Chantal ULg

in Eduquer les mangeurs ? De l'éducation nutritionnelle à l'éducation alimentaire (2008, December 09)

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See detailLa Commune de 1871 comme forme (du) politique. Autour de L’État et la révolution (Lénine, 1917)
Bolmain, Thomas ULg

Scientific conference (2008, December 06)

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See detailBehavior of Deep Reinforced Concrete Beams under Monotonic and Reversed Cyclic Load
Mihaylov, Boyan ULg

Doctoral thesis (2008)

Non-slender reinforced concrete beams find extensive application in cases where heavy loads need to be transferred over a given span. The safety of this kind of structural elements is often critical for ... [more ▼]

Non-slender reinforced concrete beams find extensive application in cases where heavy loads need to be transferred over a given span. The safety of this kind of structural elements is often critical for the safety of the structure as a whole. The research described in this thesis is devoted to studying the behaviour of lightly-reinforced non-slender beams under monotonic and reversed cyclic loads, as particular consideration is given to the load-bearing mechanisms which occur in moderately-deep beams. The choice of this topic was motivated in part by verification studies which show that the current code procedures for shear design of members without web reinforcement are least accurate in the range of transition from deep to slender beams. Furthermore, the issue of cyclic response of lightly-reinforced deep beams is of great importance for seismic assessment of existing structures, especially if the similarity between the load-bearing mechanisms in deep beams and those in other non-slender components such as coupling beams, squat shear walls, and frame joints is recognized. An experimental program consisting of ten tests of large non-slender reinforced concrete beams has been performed. All specimens failed in shear after transition from beam load-bearing mechanism to arch action (specimens without stirrups) or truss actions (specimens with stirrups). A suggested kinematic model was successfully used for interpretation of the various deformation measurements. The results showed that part of the ultimate shear was carried in the cracked concrete. It was concluded that load reversals had little effect on the overall response. A test of deep beam provided with single bar #18 demonstrated that anchorage by anchor heads is effective even when the biggest ASTM reinforcing bar is used. Comparison between experimentally-obtained and calculated shear strengths showed that the CSA code rendered reasonably conservative predictions compared to the mostly unconservative results of the ACI and EC2 codes. Theoretical work resulted in a derivation of an improved strut-and-tie model (ISTM) which is based on the CSA shear provisions but accounts for shear carried under the critical diagonal cracks of non-slender beams without web reinforcement. Verification against a large number of tests showed that the new model is consistent with physical observations and explains the transition from deep to slender beams. Furthermore, it was shown that the ISTM can be used in combination with the above-mentioned kinematic model for estimation of the ultimate displacement and deformed shape of non-slender beams. [less ▲]

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See detailHigh Pathogenic Avian Influenza in Poultry Production Systems in Vietnam: Tentative Approach for an HACCP-like Risk Scoring Methodology
Le Bas, Cedric; Phan Dang, Thang ULg; Desvaux, Stéphanie et al

Scientific conference (2008, December 04)

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See detailFirst asteroseismic results from CoRoT
Michel, Eric; Baglin, A.; Weiss, W. W. et al

in Communications in Asteroseismology (2008), 156

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first ... [more ▼]

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first results to illustrate how these data of unprecedented quality shed a new light on the field of stellar seismology. [less ▲]

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See detailA sharp look at the gravitationally lensed quasar SDSS J0806+2006 with laser guide star adaptive optics at the VLT
Sluse, Dominique ULg; Courbin, F.; Eigenbrod, A. et al

in Astronomy and Astrophysics (2008), 492

We present the first VLT near-IR observations of a gravitationally lensed quasar, using adaptive optics and laser guide star. These observations can be considered as a test bench for future systematic ... [more ▼]

We present the first VLT near-IR observations of a gravitationally lensed quasar, using adaptive optics and laser guide star. These observations can be considered as a test bench for future systematic observations of lensed quasars with adaptive optics, even when bright natural guide stars are not available in the nearby field. With only 14 min of observing time, we derived very accurate astrometry of the quasar images and of the lensing galaxy, with 0.05´´ spatial resolution, comparable to the Hubble Space Telescope (HST). In combination with deep VLT optical spectra of the quasar images, we use our adaptive optics images to constrain simple models for the mass distribution of the lensing galaxy. The latter is almost circular and does not need any strong external shear to fit the data. The time delay predicted for SDSS J0806+2006, assuming a singular isothermal ellipsoid model and the concordance cosmology, is Δ t ≃ 50 days. Our optical spectra indicate a flux ratio between the quasar images of A/B = 1.3 in the continuum and A/B = 2.2 in both the Mg ii and in the C iii] broad emission lines. This suggests that microlensing affects the continuum emission. However, the constant ratio between the two emission lines indicates that the broad emission line region is not microlensed. Finally, we see no evidence of reddening by dust in the lensing galaxy. Based on observations collected at the European Southern Observatory, Paranal, Chile, ESO Program 079.A-0588(A). [less ▲]

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See detailPreliminary seismic study of the gamma Doradus COROT target HD 49434
Bouabid, M.-P.; Uytterhoeven, K.; Miglio, Andrea ULg et al

in Communications in Asteroseismology (2008), 157

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See detailModeling stochastic excitation of acoustic modes in stars: present status and perspectives
Samadi, R.; Belkacem, Kevin ULg; Goupil, M*-J et al

in Communications in Asteroseismology (2008), 157

Solar-like oscillations have now been detected for more than ten years and their frequencies measured for a still growing number of stars with various characteristics (e.g. mass, chemical composition ... [more ▼]

Solar-like oscillations have now been detected for more than ten years and their frequencies measured for a still growing number of stars with various characteristics (e.g. mass, chemical composition, evolutionary stage ...). Excitation of such oscillations is attributed to turbu- lent convection and takes place in the uppermost part of the convective envelope. Since the pioneering work of Goldreich & Keely (1977), more sophisticated theoretical models of stochastic excitation were developed, which differ from each other both by the way turbulent convection is modeled and by the assumed sources of excitation. We briefly review here the different underlying approximations and assumptions of those models. A second part shows that computed mode excitation rates crucially depend on the way time-correlations between eddies are described but also on the surface metal abundance of the star. [less ▲]

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See detailProblems and prospects in stellar physics
Dupret, Marc-Antoine ULg

in Communications in Asteroseismology (2008), 157

Main difficulties and uncertainties in stellar physics originate in the modelling of convection, microscopic and macroscopic transport mechanisms and rotation. I consider each of these physical aspects ... [more ▼]

Main difficulties and uncertainties in stellar physics originate in the modelling of convection, microscopic and macroscopic transport mechanisms and rotation. I consider each of these physical aspects, with a particular attention to their possible probe by asteroseismology. Another important question about opacities is considered by Montalban & Miglio (2008). [less ▲]

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