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See detailThe peculiar Of?p stars HD 108 and HD 191612
Nazé, Yaël ULg; Rauw, Grégor ULg; Walborn, N. R. et al

in Massive Stars and High-Energy Emission in OB Associations (2005, November 01)

The Of?p spectral category was introduced by Walborn in 1972 to describe peculiar stars which possess intense emission lines of C III 4647,4650,4651. Recently, two of them, HD 108 and HD 191612, were ... [more ▼]

The Of?p spectral category was introduced by Walborn in 1972 to describe peculiar stars which possess intense emission lines of C III 4647,4650,4651. Recently, two of them, HD 108 and HD 191612, were found to display spectacular line profile variations in the visible domain: these stars apparently alternate between two different spectral states (O6-O8). To discover the origin of this intriguing behaviour, a multiwavelength campaign was undertaken. In this context, the analysis of the X-ray emission is especially important since it provides crucial information for constraining the nature of these peculiar objects and testing conflicting models. We are therefore carrying out high-quality XMM-Newton observations of these stars and we present the results of the data obtained up to now. [less ▲]

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See detailL'astronomie dans le monde
Manfroid, Jean ULg

Article for general public (2005)

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See detailIntestinal effects of long-lasting spermine ingestion by suckling rats
Deloyer, Patricia; Peulen, Olivier ULg; Dandrifosse, Guy ULg

in Experimental Physiology (2005), 90(6), 901-908

Spermine ingestion induces the precocious maturation of the small intestine in suckling rats. Previous observations suggest that spermine-induced intestinal maturation is a two-step phenomenon. The first ... [more ▼]

Spermine ingestion induces the precocious maturation of the small intestine in suckling rats. Previous observations suggest that spermine-induced intestinal maturation is a two-step phenomenon. The first step is the elimination of immature enterocytes (4-10 h post spermine ingestion) and the second step is the replacement of previous immature cells by adult-type enterocytes (2-3 days post initial spermine administration). The spermine-induced maturation is reversible when spermine administration is stopped. This work was undertaken in order to check whether the extension of polyamine administration (for 3-7 days) after the appearance of spermine-induced maturation can retain the mature state of the small intestine. Our results indicate that extension of spermine administration does not prevent some parameters (sucrase and maltase specific activities) reverting to a typical 'immature' value while others remain at a typical 'mature' level (mucosal weight and lactase specific activity). Our results show that there are at least two different mechanisms in required for the control of spermine-induced maturation of the small intestine. [less ▲]

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See detailLine narrowing effect on the retrieval of HF and HCl vertical profiles from ground-based FTIR measurements
Barret, Brice; Hurtmans, Daniel; Carleer, Michel R. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2005), 95(4), 499-519

Collision-induced line narrowing, which has been discovered in the 1950s and investigated thoroughly in the laboratory since then, has yet never been taken into account in the spectroscopic remote sensing ... [more ▼]

Collision-induced line narrowing, which has been discovered in the 1950s and investigated thoroughly in the laboratory since then, has yet never been taken into account in the spectroscopic remote sensing of the atmosphere. This work investigates the effect of collision-induced line narrowing onto the retrieval of HCl and HF vertical profiles from ground-based solar absorption FTIR measurements made at the NDSC station of the Jungfraujoch (46.5 degrees N, 8 degrees E and 3580 m above see level). The retrievals are performed with the Atmosphit software, recently developed at the Universite Libre de Bruxelles. It is presented in this paper for the first time and is validated against the widely used SFIT2 software. The impact of the line narrowing onto the retrieval of HCl and HF vertical profiles is examined relying on careful information content and error budget analyses. We report that the effect is relatively weak for HCl but significant for HF. Confirmation of the need to take the line narrowing into account for the retrieval of vertical profiles from ground-based FTIR spectra is given by comparison with data from the HALOE space borne instrument, rather insensitive to this spectroscopic effect. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailNon-LTE effects on H-3(+) emission in the jovian upper atmosphere
Melin, Henrik; Miller, Steve; Stallard, Tom et al

in Icarus: International Journal of Solar System Studies (2005), 178(1), 97-103

Calculations of column intensities are performed for a number of infrared transitions of the H-3(+) molecular ion, using a model atmosphere recently produced by Grodent et al. [2001. A self-consistent ... [more ▼]

Calculations of column intensities are performed for a number of infrared transitions of the H-3(+) molecular ion, using a model atmosphere recently produced by Grodent et al. [2001. A self-consistent model of the jovian auroral thermal structure. J. Geophys. Res. 106, 12933-12952]. The line intensities integrated along the line of sight through the model atmosphere are first computed assuming that all of the emitting energy levels are in local thermodynamic equilibrium (LTE). These results are compared with those derived from a detailed balance calculation using a method recently proposed by Oka and Epp [2004. Non-thermal rotational distribution of H-3(+). Astrophys. J. In press]. It is shown that the population of excited vibrational levels starts to depart from that derived from LTE at attitudes higher than 500 km (above the jovian cloud tops). This effect has been noted previously by Kim et it. [1992. Densities and vibrational distribution of H-3(+) in the jovian auroral atmosphere. J. Geophys. Res. 97, 6093-6101]. By 2000 km, all of the excited vibrational levels are Populated at less than 10% of the expected LTE value. This has important implications for the jovian upper atmosphere. In particular, the H-3(+) cooling effect will be greatly reduced high in the atmosphere. Modelled LTE line emission is greater than that derived from non-LTE modelling. Comparison of the non-LTE modelling with recent spectral measurements of the jovian auroral/polar regions in the L- and K-infrared windows shows that the Grodent et al. [2001. A self-consistent model of the jovian auroral thermal structure. J. Geophys. Res. 106, 12933-12952] profile overestimates the measured line intensity by similar to 3. Allowing for this, the non-LTE modelling shows that the column densities derived from (quasi-)LTE treatment of the measured line intensities may underestimate the real H-3(+) abundance by a factor of between 6 and 200. This means that attempts to derive important ionospheric properties, such as conductivity and related energy inputs due to magnetosphere-ionosphere coupling, front observed spectra will need to take this into account, if they are not to be seriously in error. (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailAnnular Groove Phase Mask Coronagraph
Mawet, D.; Riaud, Pierre ULg; Absil, Olivier ULg et al

in Astrophysical Journal (2005), 633

We present a new phase mask coronagraph consisting in an optical vortex induced by a space-variant surface relief subwavelength grating. Phase mask coronagraphy is a recent technique aiming at ... [more ▼]

We present a new phase mask coronagraph consisting in an optical vortex induced by a space-variant surface relief subwavelength grating. Phase mask coronagraphy is a recent technique aiming at accommodating both high dynamic and high angular resolution imaging of faint sources around bright objects such as exoplanets orbiting their parent stars or host galaxies of active galactic nuclei. Subwavelength gratings are known to be artificially birefringent. Their unique dispersive characteristics can be controlled through the grating geometry in order to synthesize achromatic phase shifters. We show that implementing them in a ring-shaped way produces a fully symmetric and achromatic coronagraph without any gap or ``dead zone.'' The practical manufacturing of the device is also discussed. [less ▲]

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See detailRadiative parameters for some transitions in the spectrum of Ag-II
Campos, J.; Ortiz, M.; Mayo, R. et al

in Monthly Notices of the Royal Astronomical Society (2005), 363(3), 905-910

Radiative parameters for transitions depopulating the levels belonging to the 4d(8)5s(2), 4d(9)6s and 4d(9)5d configurations of Ag II have been obtained from a combination of theoretical lifetimes and ... [more ▼]

Radiative parameters for transitions depopulating the levels belonging to the 4d(8)5s(2), 4d(9)6s and 4d(9)5d configurations of Ag II have been obtained from a combination of theoretical lifetimes and experimental branching fractions. On the experimental side, a laser-produced plasma was used as a source of Ag+ ions. The light emitted by the plasma was analysed by a grating monochromator coupled with a time-resolved optical multichannel analyser system. Spectral response calibration of the experimental system was performed using a deuterium lamp in the wavelength range from 200 to 400 nm, and a standard tungsten lamp in the range from 350 to 600 nm. The transition probabilities were obtained from measured branching ratios and theoretical radiative lifetimes of the corresponding states calculated with a relativistic Hartree-Fock approach including core-polarization effects and configuration interaction in an extensive way. Theoretical and experimental data have been compared and the new data have also been compared with the few previous results available in the literature. [less ▲]

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See detailStars in the eyes, birth of a vocation ?
Nazé, Yaël ULg

in Astrophysics, and How to Attract Young People into Physics (2005, November 01)

It is generally difficult to interest people to sciences, especially physics. However, astronomy has a great power of fascination, and can thus be used to attract people into the scientific world. Here in ... [more ▼]

It is generally difficult to interest people to sciences, especially physics. However, astronomy has a great power of fascination, and can thus be used to attract people into the scientific world. Here in Liège, we are trying to develop several different aspects of astro-education: they will be detailed in this paper. For example, we organize interactive activities for primary schools, and also help high school students to consider a scientific career. Our undergraduate students also benefit from our experience: for example, they have the possibility to observe at a real observatory, they can train at ESA facilities,... The general public is also invited to discover astronomy and, through it, physics, thanks to several specific events. Finally, media, the links between the public and the researchers, are not forgotten: our astro-news service was specifically created for this purpose. [less ▲]

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See detailNon-adiabatic seismic study of the triple system DG Leo
Grigahcène, A.; Suárez, J. C.; Dupret, Marc-Antoine ULg et al

in Tidal Evolution and Oscillations in Binary Stars (2005, November 01)

The interest in studying multiple systems comes from the fact that they give a good number of constraints on their components. From the multiplicity we have constraints on mass and age. Moreover, if one ... [more ▼]

The interest in studying multiple systems comes from the fact that they give a good number of constraints on their components. From the multiplicity we have constraints on mass and age. Moreover, if one or more components of the system show oscillating properties as the DG Leo triple system, additional constraints provided by seismology can be obtained once the modes are identified. In this work, we consider an equilibrium model of the DG Leo system constrained by its multiplicity properties, we attempt to check our new Time Depending Convection treatment on the modes identification of the DG Leo system. [less ▲]

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See detailOn the potential of extrasolar planet transit surveys
Gillon, Michaël ULg; Courbin, F.; Magain, Pierre ULg et al

in Astronomy and Astrophysics (2005), 442

We analyse the respective benefits and drawbacks of ground-based and space-based transit surveys for extrasolar planets. Based on simple but realistic assumptions about the fraction of lower main sequence ... [more ▼]

We analyse the respective benefits and drawbacks of ground-based and space-based transit surveys for extrasolar planets. Based on simple but realistic assumptions about the fraction of lower main sequence stars harboring telluric and giant planets within the outer limit of the habitable zone, we predict the harvests of fictitious surveys with three existing wide field optical and near-IR cameras: the CFHT-Megacam, SUBARU-Suprime and VISTA-IR. An additional promising instrument is considered, VISTA-Vis, currently under development. The results are compared with the harvests predicted under exactly the same assumptions, for the space missions COROT and KEPLER. We show that ground-based wide field surveys may discover more giant planets than space missions. However, space surveys seem to constitute the best strategy to search for telluric planets. In this respect, the KEPLER mission appears 50 times more efficient than any of the ground-based surveys considered here. KEPLER might even discover telluric planets in the habitable zone of their host star. [less ▲]

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See detailTemps vécu et art contemporain
Hagelstein, Maud ULg

Conference given outside the academic context (2005)

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See detailLes obligations juridiques de cohérence du droit ou comment le droit se protège contre lui-même
Delnoy, Michel ULg

in Biquet, Christine; Deliège, Alain; Lecocq, Pascale (Eds.) et al Liber Amicorum Paul Delnoy (2005)

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See detailActualisation du Résumé Infirmier Minimum et utilisation de la Classification des Interventions en Soins Infirmiers (NIC)
THONON, Olivier ULg; CODOGNOTTO, Jean ULg; GILLET, Pierre ULg et al

in Actes des 15èmes Journées d'Etude Européennes de l'AFEDI (2005, November)

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See detailUne Approche des Musiques Africaines-Américaines (gospel,blues,jazz) et leurs influences sur les musiques occidentales
Sacré, Robert ULg

Conference given outside the academic context (2005)

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See detailEffect of nutritional status on oxidative stress in an ex vivo perfused rat liver
Stadler, M.; Nuyens, V.; Seidel, Laurence ULg et al

in Anesthesiology (2005), 103(5), 978-986

Background: Normothermic ischemia-reperfusion is a determinant in liver injury occurring during surgical procedures, ischemic state, and multiple organ failure. The preexisting nutritional status of the ... [more ▼]

Background: Normothermic ischemia-reperfusion is a determinant in liver injury occurring during surgical procedures, ischemic state, and multiple organ failure. The preexisting nutritional status of the liver might contribute to the extent of tissue injury and primary nonfunction. The aim of this study was to determine the role of starvation on hepatic ischemia-raperfusion injury in normal rat livers. Methods: Rats were randomly divided into two groups: one had free access to food, the other was fasted for 16 h. The portal vein was cannulated, and the liver was removed and perfused in a closed ex vivo system. Two modes of perfusion were applied in each series of rats, fed and fasting. In the ischemia-reperfusion mode, the experiment consisted of perfusion for 15 min, warm ischemia for 60 min, and reperfusion during 60 min. In the nonischemia mode, perfusion was maintained during the 135-min study period. Five rats were included in each experimental condition, yielding a total of 20 rats. Liver enzymes, potassium, glucose, lactate, free radicals, ie., dienes and trienes, and cytochrome c were analyzed in perfusate samples. The proportion of glycogen in hepatocytes was determined in tissue biopsies. Results: Transaminases, lactate dehydrogenase, potassium, and free radical concentrations were systematically higher in fasting rats in both conditions, with and without ischemia. Cytochrome c was higher after reperfusion in the fasting rats. Glucose and lactate concentrations were greater in the fed group. The glycogen content decreased in both groups during the experiment but was markedly lower in the fasting rats. Conclusions: In fed rats, liver injury was moderate, whereas hepatocytes integrity was notably impaired both after continuous perfusion and warm ischemia in fasting animals. Reduced glycogen store in hepatocytes may explain reduced tolerance. [less ▲]

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See detailEvidence for phase-locked X-ray variations from the colliding-wind massive binary Cyg OB2 #8A
De Becker, Michaël ULg; Rauw, Grégor ULg

in Rauw, G.; Nazé, Y.; Blomme, R. (Eds.) et al Massive Stars and High-Energy Emission in OB Associations (2005, November)

We report on preliminary results of a multi-observatory investigation of the X-ray emission from the massive colliding wind binary Cyg OB2 #8A (O6If + O5.5III(f)). On the basis of our new XMM-Newton-EPIC ... [more ▼]

We report on preliminary results of a multi-observatory investigation of the X-ray emission from the massive colliding wind binary Cyg OB2 #8A (O6If + O5.5III(f)). On the basis of our new XMM-Newton-EPIC observations, along with archive ASCA-SIS and ROSAT-PSPC data, we show strong evidence for a significant phase-locked variability of the X-ray emission from Cyg OB2 #8A with the period of 21.9 days determined by De Becker et al. (2004). These results lend further support to the colliding wind scenario that was already suggested by optical data (De Becker & Rauw 2005). We briefly discuss the behaviour of the X-ray emission from this binary system as a function of phase in the context of the colliding wind scenario. [less ▲]

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See detailCampagne de mesure des odeurs sur le CET et la zone de compostage de Habay Estimation des nuisances olfactives
Nicolas, Jacques ULg; Denne, Pierre; Cobut, Pierre

Report (2005)

The study is conducted in the frame of a programme of monitoring of all landfill sites in Wallonia. The "odour" part is assigned to ULg. The present report concerns more particularly the landfill and ... [more ▼]

The study is conducted in the frame of a programme of monitoring of all landfill sites in Wallonia. The "odour" part is assigned to ULg. The present report concerns more particularly the landfill and composting site of Habay. Besides the usual field inspection technique, the research group has used GC-MS to estimate the chemical composition of the atmosphere over the composting area. [less ▲]

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See detailXMM-Newton observations of the Cyg OB2 association
Rauw, Grégor ULg; De Becker, Michaël ULg; Linder, Natacha ULg

in Massive Stars and High-Energy Emission in OB Associations (2005, November)

We present the first results of an observing campaign of the Cyg OB2 association with the XMM-Newton observatory. The brightest OB-type stars exhibit rather hard spectra suggesting that at least part of ... [more ▼]

We present the first results of an observing campaign of the Cyg OB2 association with the XMM-Newton observatory. The brightest OB-type stars exhibit rather hard spectra suggesting that at least part of their X-ray emission arises in a wind-wind interaction. The EPIC images reveal a large number of fainter X-ray sources most of which are probably low-mass pre-main sequence stars belonging to Cyg OB2. [less ▲]

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