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See detailThe first three billion years of life Evolution
Javaux, Emmanuelle ULg

Conference (2013, June)

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See detailFirst trends towards a field odour detector for environmental applications
Nicolas, Jacques ULg; Romain, Anne-Claude ULg; Wiertz, V. et al

in Weimar, Udo (Ed.) Proceedings of ISOEN 99 (1999)

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See detailFirst unambiguous asteroseismologic modelling of a gamma Doradus star
Moya, A.; Grigahcene, A.; Suárez, J. C. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2006), 77

An asteroseismologic model of the gamma Dor star 9 Aurigae is discussed in this work. This is the first time a complete asteroseismologic scheme for analyzing gamma Dor stars is applied. From standard ... [more ▼]

An asteroseismologic model of the gamma Dor star 9 Aurigae is discussed in this work. This is the first time a complete asteroseismologic scheme for analyzing gamma Dor stars is applied. From standard photometric observations (at least three oscillation frequencies, a photometric error box in the HR diagram and multicolor photometric observations, in this case in the Strömgren system) we can reduce the possible theoretical models for this star, providing constraints to the stellar parameters as mass, overshooting, metallicity, MLT parameter alpha , Brunt-Väiälä integral (I[SUB]th[/SUB]), etc. Simultaneously, an estimate of the modal identification of the observed frequencies is also obtained. This can be possible by the application, for the first time, of a complete procedure where different theoretical and computational techniques, recently developed, are linked and compared with photometric observations. The Frequency Ratio Method (FRM) and the Time Dependent Convection (TDC) theory are the basis of this complete procedure. [less ▲]

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See detailThe first Upper Paleolithic human remains from Belgium: Aurignacian, Gravettian and Magdalenian fossils at the “troisième caverne” of Goyet
Rougier, H.; Crevecoeur, I.; Beauval, C. et al

Poster (2013)

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See detailFirst vortex entry into a perpendicularly magnetized superconducting thin film
Gutierrrez, Joffre; Raes, Bart; Van de Vondel, Joris et al

in Physical Review. B : Condensed Matter (2013), 88

In type-II superconductors, the flux-free state (Meissner state) may be invaded by vortices bearing quantized flux once H is above the lower critical field Hc1. However, the actual first flux penetration ... [more ▼]

In type-II superconductors, the flux-free state (Meissner state) may be invaded by vortices bearing quantized flux once H is above the lower critical field Hc1. However, the actual first flux penetration does not occur at Hc1 due to the presence of a surface barrier and the fact that the Meissner state may also exist as a metastable state up to a larger (superheating) field. In this work we determine the field for the first vortex penetration in superconductors, by directly imaging the first vortex threading a superconducting Pb film with antidots. We find that the first vortex penetration occurs when the surface superconducting currents reach the depairing current, locally breaking superconductivity and allowing a vortex to nucleate. [less ▲]

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See detailThe first X-ray survey of Galactic Luminous Blue Variables
Nazé, Yaël ULg; Rauw, Grégor ULg; Hutsemekers, Damien ULg

in Astronomy and Astrophysics (2012), 538

Aims: The X-ray emission of massive stars has been studied when these objects are in their main-sequence phase, as well as in their Wolf-Rayet phase. However, the X-ray properties of the transitional ... [more ▼]

Aims: The X-ray emission of massive stars has been studied when these objects are in their main-sequence phase, as well as in their Wolf-Rayet phase. However, the X-ray properties of the transitional Luminous Blue Variable (LBV) phase remain unknown. Methods: Using a dedicated but limited XMM survey as well as archival XMM and Chandra observations, we performed the first X-ray survey of LBVs: about half of the known LBVs or candidate LBVs are studied. Results: Apart from the well known X-ray sources eta Car and Cyg OB2 #12, four additional LBVs are detected in this survey, though some doubt remains on the association with the X-ray source for two of these. For the other LBVs, upper limits on the flux were derived, down to $\log[L_{\rm X}/L_{\rm BOL}]-9.4$ for PCyg. This variety in the strength of the X-ray emission is discussed, with particular emphasis on the potential influence of binarity. [less ▲]

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See detailFirst year prognosis after myocardial infarction assassed from simple clinical findings
Smeets, J. P.; Foidart, G.; Dubois, Christophe ULg et al

Poster (1982, September)

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See detailFirst ‘in situ’ determination of gas transport coefficients (DO2, DAr and DN2 ) from bulk gas 2 concentration measurements (O2, N2, Ar) in natural sea ice
Crabeck, O.; Delille, Bruno ULg; Rysgaard, S. et al

in Marine Chemistry (in press)

We report bulk gas concentrations of O2, N2 and Ar, as well as their transport coefficients, in natural landfast subarctic sea ice in southwest Greenland. The observed bulk ice gas composition was 27.5 ... [more ▼]

We report bulk gas concentrations of O2, N2 and Ar, as well as their transport coefficients, in natural landfast subarctic sea ice in southwest Greenland. The observed bulk ice gas composition was 27.5% O2, 71.4% N2 and 1.09% Ar. Most previous studies suggest that convective transport is the main driver of gas displacement in sea ice and have neglected diffusion processes. According to our data, brines were stratified within the ice, so that no convective transport could occur within the brine system. Therefore, diffusive transport was the main driver of gas migration. By analysing the temporal evolution of an internal gas peak within the ice, we deduced the bulk gas transport coefficients for oxygen (DO2), argon (DAr) and nitrogen (DN222 ). The values fit to the few existing estimates from experimental work, and are close to the diffusivity values in water (10-5 cm2 s-124 ). We suggest that gas bubbles escaping from the brine to the atmosphere - as the ice gets more permeable during melt could be responsible for the previously reported high transport coefficients. These results underline that when there is no convective transport within the sea ice, the transport of gas by diffusion through the brines, either in the liquid or gaseous phases, is a major factor in controlling the ocean–atmosphere exchange. [less ▲]

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See detailFirst- and multi-swing transient stability limits of the Hydro-Québec system using the SIME method
Zhang, Y.; Wehenkel, Louis ULg; Rousseaux, Patricia ULg et al

in Proceedings of the Melecon'96 Conference (1996)

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See detailFirst- and second-order Fermi acceleration in thick relativistic shocks
Meli, Athina ULg

in AIP Conference Proceedings (2012)

Shocks in relativistic jets are regions where cosmic ray acceleration takes place mainly via two kinds of Fermi acceleration mechanism: The first-order and the second-order Fermi acceleration. Moreover ... [more ▼]

Shocks in relativistic jets are regions where cosmic ray acceleration takes place mainly via two kinds of Fermi acceleration mechanism: The first-order and the second-order Fermi acceleration. Moreover, the back-reaction of accelerated particles in astrophysical shock fronts leads to the formation of a precursor (thick) shock with a length scale which can correspond to the diffusive scale of the energetic particles. Our scope here is to investigate the properties of particle shock acceleration, using test-particle simulation studies, assuming stochastic and diffusive acceleration mechanisms, in thick parallel and perpendicular relativistic shocks. The role of the above parameters in the acceleration efficiency and generated cosmic ray spectra, is important to understanding further the favourable subject of the cosmic ray shock acceleration in relativistic astrophysical environments. [less ▲]

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See detailFirst-choice treatment for post menopausal osteoporotic patients
Reginster, Jean-Yves ULg

in Osteoporosis International (2007, March), 18(Suppl.1), 178

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See detailFirst-generation versus third generation comprehensive geriatric assessment instruments in the acute hospital setting: a comparison of the Minimum Geriatric Screening Tools (MGST) and the interRAI Acute Care (interRAIAC)
WELLENS, N. L.; DESCHODT, M.; FLAMAING, J. et al

in Journal of Nutrition, Health & Aging (The) (2011), 15(8), 638-644

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See detailA first-order energy-dissipative momentum-conserving scheme for elasto-plasticity using the variational updates formulation
Noels, Ludovic ULg; Stainier, Laurent ULg; Ponthot, Jean-Philippe ULg

in Computer Methods in Applied Mechanics & Engineering (2008), 197(6-8), 706726

In a previous paper [L. Noels, L. Stainier, J.-P. Ponthot, An energy momentum conserving algorithm using the variational formulation of visco-plastic updates, Int. J. Numer. Methods Engrg. 65 (2006) 904 ... [more ▼]

In a previous paper [L. Noels, L. Stainier, J.-P. Ponthot, An energy momentum conserving algorithm using the variational formulation of visco-plastic updates, Int. J. Numer. Methods Engrg. 65 (2006) 904-942] the authors demonstrated the efficiency of the variational formulation of elasto-plastic updates to develop energy-momentum conserving time integration algorithms. Indeed, within such a framework, the stress tensor always derives from an incremental potential, even when plastic behavior is considered. Therefore the verification of the conservation of energy in the non-linear range can easily be demonstrated: the sum of the reversible stored energy and irreversible dissipated energy exactly corresponds to the work of the external forces applied to the structure. Although this formulation was shown to be accurate and robust, the introduction of numerical dissipation for high-frequency numerical modes can be necessary to simulate complex phenomena. In this work, we propose a modification of the variational updates framework to introduce this numerical property, leading to a new energy-dissipative momentum-conserving time-integration algorithm for elasto-plasticity. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailFirst-principle study of crystals exhibiting an incommensurate phase transition
Gonze, X.; Caracas, R.; Sonnet, R. et al

in AIP Conference Proceedings (2000), 535

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See detailFirst-principles and experimental studies of hexagonal YMnO3 single crystals and epitaxial films
Prikockyte, Alina ULg

Doctoral thesis (2012)

Multiferroic materials have attracted much interest during the recent years. Our study is devoted to a prototypic system: yttrium manganite. In particular, we focus on the ferroelectric properties in bulk ... [more ▼]

Multiferroic materials have attracted much interest during the recent years. Our study is devoted to a prototypic system: yttrium manganite. In particular, we focus on the ferroelectric properties in bulk and in thin film forms. Yttrium manganite belongs to the class of ABO3 compounds. Most theoretical studies of ferroelectricity to date were concentrated on cubic perovskite ABO3. Yttrium manganite is hexagonal and is an improper ferroelectric. We were interested to study theoretically and experimentally how these two features behave in thin film form. Our study is organized as follows. [less ▲]

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See detailFirst-principles calculation of kinetic barriers and metastability for the corundum-to-Rh/sub 2/O/sub 3/(II) transition in Al/sub 2/O/sub 3/
Xu, Bin ULg; Stokes, Harold; Dong, Jianjun

in Journal of Physics: Condensed Matter (2010), 22(31), 3154036-3154036

We demonstrate that the rhombohedral corundum crystal and the orthorhombic Rh/sub 2/O/sub 3/ (II) crystal are structurally related by a diffusionless monoclinic common subgroup pathway, along which the ... [more ▼]

We demonstrate that the rhombohedral corundum crystal and the orthorhombic Rh/sub 2/O/sub 3/ (II) crystal are structurally related by a diffusionless monoclinic common subgroup pathway, along which the intermediate structures have the space group P2/c symmetry. This transformation pathway is energetically favored because the majority of Al-O bonds are preserved during the transition. Only 1/3 of the four-coordinated anions and 1/2 of the six-coordinated cations break and reform a single bond. No other bonds are broken in the transformation. Our calculated forward (corundum-to-Rh/sub 2/O/sub 3/ (II)) enthalpy barrier (about 140 meV/atom) in Al/sub 2/O/sub 3/ is not pressure-sensitive at least up to 160 GPa, which is consistent with the observed metastability of the corundum phase around room temperature. In contrast, we predict a significantly decreasing backward (Rh/sub 2/O/sub 3/ (II)-to-corundum) enthalpy barrier on decompression, which suggests that the high-pressure Rh/sub 2/O/sub 3/ (II) phase of Al/sub 2/O/sub 3/ is unlikely to be recoverable at ambient conditions. In addition, we propose a general, common subgroup-based approach to compare elastic properties of two phases with different Bravais lattices. By treating both rhombohedral and orthorhombic phases with common monoclinic P2/c unit cells (non-primitive for the corundum phase), we show that the elastic properties of the high-pressure Rh/sub 2/O/sub 3/ (II) phase are very comparable to those of the ambient corundum phase. [less ▲]

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