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See detailThe influence of mineral and organic long-term fertilization upon the floristic composition of Festuca rubra L.-Agrostis capillaris L. grassland in Apuseni mountains, Romania
Pacurar, Florin; Rotar, Ioan; Bogdan, Anca Dorina et al

in Journal of Food, Agriculture & Environment (2012), 10(1), 866-879

The semi-natural grasslands in Apuseni Mountains are particularly important for the sustainable development of this region. The future development strategies must take into consideration the conservation ... [more ▼]

The semi-natural grasslands in Apuseni Mountains are particularly important for the sustainable development of this region. The future development strategies must take into consideration the conservation of grassland plant diversity. In Apuseni Mountains there are numerous caves and a traditional landscape, these forming the area’s wealth. Their joining with agro-tourism and performing a sustainable agriculture would significantly level up the wellbeing of the local population, who are in need of new income sources considering that the wood resources are more and more reduced. In Gârda de Sus there are considerable areas of semi-natural grasslands which lately have been traditionally used. Nowadays, some of them have been abandoned and others irrationally intensified. Therefore, the objective of this paper was to evaluate the effects of mineral and organic fertilization upon the sward in order to recommend certain versions which have minor repercussions upon the plant diversity. The research was carried out in Apuseni Mountains, in an experimental field with two experiences: one with mineral fertilizers (T1 control, T2 50N25P25K, T3100N50P50K, T4 150N75P75K) and the other with organic fertilizers (T1 control, T2 10 t ha-1 manure, T3 20 t ha-1 manure, T4 30 t ha-1 manure). Administrating mineral fertilizers on the Festuca rubra L.- Agrostis capillaris L. grassland induced the installation of Festuca rubra L. and Trisetum flavescens L. at 50N25P25K treatment, whereas 100N50P50K and 150N75P75K treatments induced the installation of Agrostis capillaris L. and Trisetum flavescens L. grassland subtype. The plant diversity decreased as the system was intensified, especially at the treatment with 100N50P50K and 150N75P75K. Administrating 50N25P25K did not induce any significant changes in plant diversity. Giving organic fertilizers caused installation of Festuca rubra L. and Trisetum flavescens L. at the treatment using 10 t ha-1 manure and Trisetum flavescens L. at using 20 and 30 t ha-1 manure. The treatment with 10 t ha-1 manure induced a growth of the plant diversity and by raising the manure quantity did not cause important changes with respect to the species’ number. For future management actions that are meant to maintain the plant diversity in Apuseni Mountains, the organic fertilization with 10 t ha-1 manure quantities annually administrated or once in two years is recommended first of all, and, secondly, the fertilization with 50N25P25K performed annually or once in two years. [less ▲]

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See detailÉnonciation visuelle et négation en image : des arts aux sciences
Dondero, Maria Giulia ULg

in Nouveaux Actes Sémiotiques (2012)

Ce travail part du constat que l’image peut prédiquer et vise à démontrer qu’elle possède la capacité de nier. Nous examinons différentes grandeurs discursives (image-texte, série, intertextualité, genre ... [more ▼]

Ce travail part du constat que l’image peut prédiquer et vise à démontrer qu’elle possède la capacité de nier. Nous examinons différentes grandeurs discursives (image-texte, série, intertextualité, genre, statut) où peut se manifester la négation d’un point de vue tensif et méréologique et nous essayons d’en caractériser les différents fonctionnements dans deux domaines d’interprétation variés : les domaines artistique et scientifique. Il s’agit en premier lieu de voir comment l’image met en scène des dispositifs métadiscursifs qui nient la fonction principale de l’image : celle d’être regardée. L’image peut moduler ce qu’elle met en scène par soustraction, diminution, détournement, etc. ou représenter quelque chose d’interdit au regard, en construisant des simulacres d’observateurs en espions ou en voyeurs. En deuxième lieu nous étudions des cas de détournement de la fonction générique du portrait en nature morte via un parcours de dé-singularisation du visage humain, et en troisième lieu nous examinons des images scientifiques visualisant des objets non expérimentables qui posent la question de la représentation de la disparition de la lumière (trous noirs) ou des mirages topologiques (selon la théorie de l’univers chiffonné de J-P. Luminet). [less ▲]

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See detailClimwat 2.0 & Cropwat 8.0
Debauche, Olivier ULg; Tadrist, Nassima ULg

Learning material (2012)

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See detailNew Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary
Fischer, Valentin ULg; Maisch, Michael; Naish, Darren et al

in PLoS ONE (2012), 7(1), 29234

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events ... [more ▼]

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic–Cretaceous boundary (JCB), and one (resulting in total extinction) at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in the Cretaceous. However, the record of ichthyosaurs from the Berriasian–Barremian interval is extremely limited, and the effects of the end-Jurassic extinction event on ichthyosaurs remains poorly understood. Methodology/Principal Findings Based on new material from the Hauterivian of England and Germany and on abundant material from the Cambridge Greensand Formation, we name a new ophthalmosaurid, Acamptonectes densus gen. et sp. nov. This taxon shares numerous features with Ophthalmosaurus, a genus now restricted to the Callovian–Berriasian interval. Our phylogenetic analysis indicates that Ophthalmosauridae diverged early in its history into two markedly distinct clades, Ophthalmosaurinae and Platypterygiinae, both of which cross the JCB and persist to the late Albian at least. To evaluate the effect of the JCB extinction event on ichthyosaurs, we calculated cladogenesis, extinction, and survival rates for each stage of the Oxfordian–Barremian interval, under different scenarios. The extinction rate during the JCB never surpasses the background extinction rate for the Oxfordian–Barremian interval and the JCB records one of the highest survival rates of the interval. Conclusions/Significance There is currently no evidence that ichthyosaurs were affected by the JCB extinction event, in contrast to many other marine groups. Ophthalmosaurid ichthyosaurs remained diverse from their rapid radiation in the Middle Jurassic to their total extinction at the beginning of the Late Cretaceous. [less ▲]

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See detailDetecting and modelling the magnetic field of the β Cephei star V 2052 Ophiuchi
Neiner, C.; Alecian, E.; Briquet, Maryline ULg et al

in Astronomy and Astrophysics (2012), 537

<BR /> Aims: Following the indirect detection of a magnetic field in the β Cephei star <ASTROBJ>V 2052 Oph</ASTROBJ> by Neiner and collaborators in 2003 with the Musicos spectropolarimeter, we remeasured ... [more ▼]

<BR /> Aims: Following the indirect detection of a magnetic field in the β Cephei star <ASTROBJ>V 2052 Oph</ASTROBJ> by Neiner and collaborators in 2003 with the Musicos spectropolarimeter, we remeasured the magnetic field of this star to attempt to directly confirm the detection of a magnetic field and study its configuration in greater detail. <BR /> Methods: We used the Narval spectropolarimeter installed at TBL (Pic du Midi, France), which is about 20 times more efficient than the Musicos spectropolarimeter. We applied the least-squares deconvolution (LSD) technique to various groups of lines to measure the circular polarisation of the light coming from <ASTROBJ>V 2052 Oph</ASTROBJ>. We synthesized the measured Stokes V profiles with a centred and off-centred dipole model. <BR /> Results: For the first time, we clearly detect the Zeeman signature in the Stokes V profiles of <ASTROBJ>V 2052 Oph</ASTROBJ> and thus directly prove the presence of a magnetic field in this star. The modulation with the rotation period is also confirmed and reflects an oblique dipole field. Thanks to the small error bars on the measurements, we are able to study the behaviour of different groups of lines and the centring of the dipole in the star. We find that the dipole is most likely off-centred along the magnetic axis and that He spots are present at the surface next to the magnetic axis. <BR /> Conclusions: We conclude that <ASTROBJ>V 2052 Oph</ASTROBJ> is a magnetic He-strong β Cep star, with a dipole field, probably off-centred, with B[SUB]pol[/SUB] ~ 400 G and He patches close to the magnetic poles. Based on observations obtained with the Narval spectropolarimeter at the Télescope Bernard Lyot, Observatoire du Pic du Midi, France. [less ▲]

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See detailModelling the huge, Herschel-resolved debris ring around HD 207129
Löhne, T.; Augereau, J.-C.; Ertel, S. et al

in Astronomy and Astrophysics (2012), 537

Debris disks, which are inferred from the observed infrared excess to be ensembles of dust, rocks, and probably planetesimals, are common features of stellar systems. As the mechanisms of their formation ... [more ▼]

Debris disks, which are inferred from the observed infrared excess to be ensembles of dust, rocks, and probably planetesimals, are common features of stellar systems. As the mechanisms of their formation and evolution are linked to those of planetary bodies, they provide valuable information. The few well-resolved debris disks are even more valuable because they can serve as modelling benchmarks and help resolve degeneracies in modelling aspects such as typical grain sizes and distances. Here, we present an analysis of the HD 207129 debris disk, based on its well-covered spectral energy distribution and Herschel/PACS images obtained in the framework of the DUNES (DUst around NEarby Stars) programme. We use an empirical power-law approach to the distribution of dust and we then model the production and removal of dust by means of collisions, direct radiation pressure, and drag forces. The resulting best-fit model contains a total of nearly 10[SUP]-2[/SUP] Earth masses in dust, with typical grain sizes in the planetesimal belt ranging from 4 to 7 μm. We constrain the dynamical excitation to be low, which results in very long collisional lifetimes and a drag that notably fills the inner gap, especially at 70 μm. The radial distribution stretches from well within 100 AU in an unusual, outward-rising slope towards a rather sharp outer edge at about 170-190 AU. The inner edge is therefore smoother than that reported for Fomalhaut, but the contribution from the extended halo of barely bound grains is similarly small. Both slowly self-stirring and planetary perturbations could potentially have formed and shaped this disk. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. [less ▲]

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See detailPulsations of rapidly rotating evolved stars
Ouazzani, Rhita-Maria ULg; Roxburgh, I. W.; Dupret, Marc-Antoine ULg

in proceedings of the 20th Stellar Pulsation Conference Series, Granada sept 2011 (2012), 1301

A new two dimensional non-perturbative code to compute accurate oscillation modes of rapidly rotating stars is presented. The 2D calculations fully take into account the centrifugal distorsion of the star ... [more ▼]

A new two dimensional non-perturbative code to compute accurate oscillation modes of rapidly rotating stars is presented. The 2D calculations fully take into account the centrifugal distorsion of the star while the non perturbative method includes the full influence of the Coriolis acceleration. This 2D non-perturbative code is used to study pulsational spectra of highly distorted evolved models of stars. 2D models of stars are obtained by a self consistent method which distorts spherically averaged stellar models a posteriori. We are also able to compute gravito-acoustic modes for the first time in rapidly rotating stars. We present the dynamics of pulsation modes in such models, and show regularities in their frequency spectra. [less ▲]

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See detailVADE-MECUM des mammites bovines
Durel, Luc; Guyot, Hugues ULg; Theron, Léonard ULg

Book published by MED'COM (2012)

La mammite demeure la pathologie la plus préjudiciable à l'élevage des bovins laitiers. C'est une maladie multifactorielle fortement pénalisante pour l'éleveur: baisse de production, baisse de prix d ... [more ▼]

La mammite demeure la pathologie la plus préjudiciable à l'élevage des bovins laitiers. C'est une maladie multifactorielle fortement pénalisante pour l'éleveur: baisse de production, baisse de prix d'achat du lait, réformes anticipées, frais médicaux... Le lait étant par ailleurs au coeur de l'industrie alimentaire, la question de sa qualité reste primordiale et le vétérinaire a un rôle important à jouer. Ce Vade-Mecum des mammites bovines a pour vocation d'être un outil à la disposition du vétérinaire sur le terrain. Il aidera le praticien à analyser la situation pour laquelle il a été appelé, à proposer des solutions adaptées, tout en communiquant les connaissances nécessaires à l'éleveur pour emporter son adhésion et faire évoluer ses pratiques. L'ouvrage est divisé en 11 chapitres interdépendants explorant de façon approfondie chaque aspect du contrôle de la maladie, en s'appuyant sur les données les plus récentes: caractéristiques des mammites, approche clinique du troupeau, bâtiments, système de traite, alimentation et troubles métaboliques, traite, diagnostic étiologique, traitement en lactation, traitement hors lactation, réformes et gestion du troupeau, ou encore biosécurité. Ce livre raisonné et pragmatique trouvera sa place dans tous les véhicules des praticiens. [less ▲]

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See detailNew constraints on very light pseudoscalars
Payez, Alexandre ULg; Cudell, Jean-René ULg; Hutsemekers, Damien ULg

in Zioutas, K. (Ed.) 7th Patras Workshop on Axions, WIMPs and WISPs (2012, January 01)

Nearly massless axion-like particles are of interest for astrophysical observations, and some constraints on their parameter space do exist in the literature. Here, we propose to put new constraints on ... [more ▼]

Nearly massless axion-like particles are of interest for astrophysical observations, and some constraints on their parameter space do exist in the literature. Here, we propose to put new constraints on these particles using polarisation and, in particular, the polarisation differences observed between different quasar classes. [less ▲]

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See detailAngular correlation functions of X-ray point-like sources in the full exposure XMM-LSS field
Elyiv, Andrii ULg; Clerc, N.; Plionis, M. et al

in Astronomy and Astrophysics (2012), 537

<BR /> Aims: Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. <BR /> Methods: We measure the two-point angular correlation function of 5700 and ... [more ▼]

<BR /> Aims: Our aim is to study the large-scale structure of different types of AGN using the medium-deep XMM-LSS survey. <BR /> Methods: We measure the two-point angular correlation function of 5700 and 2500 X-ray point-like sources over the 11 sq. deg. XMM-LSS field in the soft (0.5-2 keV) and hard (2-10 keV) bands. For the conversion from the angular to the spatial correlation function we used the Limber integral equation and the luminosity-dependent density evolution model of the AGN X-ray luminosity function. <BR /> Results: We have found significant angular correlations with the power-law parameters γ = 1.81 ± 0.02, θ[SUB]0[/SUB] = 1.3'' ± 0.2'' for the soft, and γ = 2.00 ± 0.04, θ[SUB]0[/SUB] = 7.3'' ± 1.0'' for the hard bands. The amplitude of the correlation function w(θ) is higher in the hard than in the soft band for f[SUB]x[/SUB] ≲ 10[SUP]-14[/SUP] erg s[SUP]-1[/SUP] cm[SUP]-2[/SUP] and lower above this flux limit. We confirm that the clustering strength θ[SUB]0[/SUB] grows with the flux limit of the sample, a trend which is also present in the amplitude of the spatial correlation function, but only for the soft band. In the hard band, it remains almost constant with r[SUB]0[/SUB] ≃ 10h[SUP]-1[/SUP] Mpc, irrespective of the flux limit. Our analysis of AGN subsamples with different hardness ratios shows that the sources with a hard-spectrum are more clustered than soft-spectrum ones. This result may be a hint that the two main types of AGN populate different environments. Finally, we find that our clustering results correspond to an X-ray selected AGN bias factor of 2.5 for the soft band sources (at a median <inline-formula>bar{z} ≃ 1.1) and 3.3 for the hard band sources (at a median <inline-formula>bar{z} ≃ 1), which translates into a host dark matter halo mass of 10[SUP]13[/SUP]h[SUP]-1[/SUP]M[SUB]&sun;[/SUB] and 10[SUP]13.7[/SUP]h[SUP]-1[/SUP]M[SUB]&sun;[/SUB] for the soft and hard bands, respectively. This paper is dedicated to the memory of Olivier Garcet who has initiated the present work just before his sudden death. [less ▲]

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See detailSpectral modelling of circular massive binary systems. Towards an understanding of the Struve-Sahade effect?
Palate, Matthieu ULg; Rauw, Grégor ULg

in Astronomy and Astrophysics (2012), 537

Context. Some secondary effects are known to introduce variations in spectra of massive binaries. These phenomena, such as the Struve-Sahade effect and the difficulties in determining properly the ... [more ▼]

Context. Some secondary effects are known to introduce variations in spectra of massive binaries. These phenomena, such as the Struve-Sahade effect and the difficulties in determining properly the spectral type have been reported and documented in the literature. <BR /> Aims: We simulate the spectra of circular massive binaries at different phases of the orbital cycle and account for the gravitational influence of the companion star on the shape and physical properties of the stellar surface. <BR /> Methods: We use the Roche potential to compute the stellar surface, von Zeipel theorem, and reflection effects to compute the surface temperature. We then interpolate in a grid of non-local thermodynamic equilibrium (NLTE) plan-parallel atmosphere model spectra to obtain the local spectrum at each surface point. We finally sum all the contributions, accounting for the reflection, Doppler shift, and limb-darkening to obtain the total spectrum. The computation is done for different orbital phases and for different sets of physical and orbital parameters. <BR /> Results: Our models reproduce the Struve-Sahade effect for several lines. Another effect on the surface temperature distribution is visible but the distribution predicted by our current model is not yet consistent with observations. <BR /> Conclusions: In some cases, the Struve-Sahade effect as well as more complex line intensity variations could be linked to blends of intrinsically asymmetric line profiles that are not appropriately treated by the deblending routine. Systematic variations in the lines of (nearly) contact systems are also predicted by the model. [less ▲]

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See detailFast core rotation in red-giant stars as revealed by gravity-dominated mixed modes
Beck, Paul G; Montalban Iglesias, Josefa ULg; Kallinger, Thomas et al

in Nature (2012), 481

When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much ... [more ▼]

When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidence supports this. Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected `mixed modes'. By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior. [less ▲]

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See detailLow-Flow, Low-Gradient Severe Aortic Stenosis Despite Normal Ejection Fraction Is Associated With Severe Left Ventricular Dysfunction as Assessed by Speckle-Tracking Echocardiography: A Multicenter Study.
Adda, J.; Mielot, C.; Giorgi, R. et al

in Circulation: cardiovascular imaging (2012)

Background- Low-flow low-gradient (LFLG) is sometimes observed in severe aortic stenosis (AS) despite normal ejection fraction, but its frequency and mechanisms are still debated. We aimed to describe the ... [more ▼]

Background- Low-flow low-gradient (LFLG) is sometimes observed in severe aortic stenosis (AS) despite normal ejection fraction, but its frequency and mechanisms are still debated. We aimed to describe the characteristics of patients with LFLG AS and assess the presence of longitudinal left ventricular dysfunction in these patients. Methods and Results- In a multicenter prospective study, 340 consecutive patients with severe AS and normal ejection fraction were studied. Longitudinal left ventricular function was assessed by 2D-strain and global afterload by valvulo-arterial impedance. Patients were classified according to flow and gradient: low flow was defined as a stroke volume index ≤35 mL/m(2), low gradient as a mean gradient ≤40 mm Hg. Most patients (n=258, 75.9%) presented with high-gradient AS, and 82 patients (24.1%) with low-gradient AS. Among the latter, 52 (15.3%) presented with normal flow and low gradient and 30 (8.8%) with LFLG. As compared with normal flow and low gradient, patients with LFLG had more severe AS (aortic valve area=0.7±0.12 cm(2) versus 0.86±0.14 cm(2)), higher valvulo-arterial impedance (5.5±1.1 versus 4±0.8 mm Hg/mL/m(2)), and worse longitudinal left ventricular function (basal longitudinal strain=-11.6±3.4 versus -14.8±3%; P<0.001 for all). Conclusions- LFLG AS is observed in 9% of patients with severe AS and normal ejection fraction and is associated with high global afterload and reduced longitudinal systolic function. Patients with normal-flow low-gradient AS are more frequent and present with less severe AS, normal afterload, and less severe longitudinal dysfunction. Severe left ventricular longitudinal dysfunction is a new explanation to the concept of LFLG AS. [less ▲]

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See detailAssessing the accuracy of the surface gravity determination in late-type stars with solar-like pulsators
Morel, Thierry ULg; Miglio, Andrea ULg

in Monthly Notices of the Royal Astronomical Society (2012), 419

The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An ... [more ▼]

The frequency of maximum oscillation power measured in dwarfs and giants exhibiting solar-like pulsations provides a precise, and potentially accurate, inference of the stellar surface gravity. An extensive comparison for about 40 well-studied pulsating stars with gravities derived using classical methods (ionization balance, pressure-sensitive spectral features or location with respect to evolutionary tracks) supports the validity of this technique and reveals an overall remarkable agreement with mean differences not exceeding 0.05 dex (although with a dispersion of up to ˜0.2 dex). It is argued that interpolation in theoretical isochrones may be the most precise way of estimating the gravity by traditional means in nearby dwarfs. Attention is drawn to the usefulness of seismic targets as benchmarks in the context of large-scale surveys. [less ▲]

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See detailThe spectral variability and magnetic field characteristics of the Of?p star HD 148937
Wade, G. A.; Grunhut, J.; Gräfener, G. et al

in Monthly Notices of the Royal Astronomical Society (2012), 419

We report magnetic and spectroscopic observations and modelling of the Of?p star HD 148937 within the context of the Magnetism in Massive Stars (MiMeS) Large Program at the Canada-France-Hawaii Telescope ... [more ▼]

We report magnetic and spectroscopic observations and modelling of the Of?p star HD 148937 within the context of the Magnetism in Massive Stars (MiMeS) Large Program at the Canada-France-Hawaii Telescope. 32 high signal-to-noise ratio circularly polarized (Stokes V) spectra and 13 unpolarized (Stokes I) spectra of HD 148937 were acquired in 2009 and 2010. A definite detection of a Stokes V Zeeman signature is obtained in the grand mean of all observations [in both least-squares deconvolved (LSD) mean profiles and individual spectral lines]. The longitudinal magnetic field inferred from the Stokes V LSD profiles is consistently negative, in contrast to the essentially zero field strength measured from the diagnostic null profiles. A period search of new and archival equivalent width measurements confirms the previously reported 7.03 d variability period. The variation of equivalent widths is not strictly periodic: we present evidence for evolution of the amount or distribution of circumstellar plasma. Interpreting the 7.03 d period as the stellar rotational period within the context of the oblique rotator paradigm, we have phased the equivalent widths and longitudinal field measurements. The longitudinal field measurements show a weak sinusoidal variation of constant sign, with extrema out of phase with the Hα variation by about 0.25 cycles. From our constraint on v sin i≤ 45 km s[SUP]-1[/SUP], we infer that the rotational axis inclination i≤ 30°. Modelling the longitudinal field phase variation directly, we obtain the magnetic obliquity β= 38[SUP]+17[/SUP][SUB]-28[/SUB]° and dipole polar intensity B[SUB]d[/SUB]= 1020[SUP]-380[/SUP][SUB]+310[/SUB] G. Simple modelling of the Hα equivalent width variation supports the derived geometry. The inferred magnetic configuration confirms the suggestion of Nazé et al., who proposed that the weaker variability of HD 148937 as compared to other members of this class is a consequence of the stellar geometry. Based on the derived magnetic properties and published wind characteristics, we find a wind magnetic confinement parameter η[SUB]*[/SUB]≃ 20 and rotation parameter W= 0.12, supporting a picture in which the Hα emission and other line variability have their origin in an oblique, rigidly rotating magnetospheric structure resulting from a magnetically channelled wind. [less ▲]

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See detailAsteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819
Miglio, A.; Brogaard, K.; Stello, D. et al

in Monthly Notices of the Royal Astronomical Society (2012), 419

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K ... [more ▼]

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K giants in open clusters with Kepler, we can now directly determine stellar masses for a statistically significant sample of stars in the old open clusters NGC 6791 and 6819. The aim of this work is to constrain the integrated RGB mass-loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB [i.e. stars with L≲L(RC)]. Stellar masses were determined by combining the available seismic parameters ν[SUB]max[/SUB] and Δν with additional photometric constraints and with independent distance estimates. We measured the masses of 40 stars on the RGB and 19 in the RC of the old metal-rich cluster NGC 6791. We find that the difference between the average mass of RGB and RC stars is small, but significant [? (random) ±0.04 (systematic) M[SUB]&sun;[/SUB]]. Interestingly, such a small ? does not support scenarios of an extreme mass-loss for this metal-rich cluster. If we describe the mass-loss rate with Reimers prescription, a first comparison with isochrones suggests that the observed ? is compatible with a mass-loss efficiency parameter in the range 0.1 ≲η≲ 0.3. Less stringent constraints on the RGB mass-loss rate are set by the analysis of the ˜2 Gyr old NGC 6819, largely due to the lower mass-loss expected for this cluster, and to the lack of an independent and accurate distance determination. In the near future, additional constraints from frequencies of individual pulsation modes and spectroscopic effective temperatures will allow further stringent tests of the Δν and ν[SUB]max[/SUB] scaling relations, which provide a novel, and potentially very accurate, means of determining stellar radii and masses. [less ▲]

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See detailThe remarkable surface homogeneity of the Dawn mission target (1) Ceres
Carry, Benoît; Vernazza, Pierre; Dumas, Christophe et al

in Icarus (2012), 217

Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that will be studied by the NASA Dawn spacecraft via imaging, visible and near-infrared spectroscopy, and gamma-ray and neutron ... [more ▼]

Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that will be studied by the NASA Dawn spacecraft via imaging, visible and near-infrared spectroscopy, and gamma-ray and neutron spectroscopy. While Ceres' visible and near-infrared disk-integrated spectra have been well characterized, little has been done about quantifying spectral variations over the surface. Any spectral variation would give us insights on the geographical variation of the composition and/or the surface age. The only work so far was that of Rivkin and Volquardsen ([2010], Icarus 206, 327) who reported rotationally-resolved spectroscopic (disk-integrated) observations in the 2.2-4.0 μm range; their observations showed evidence for a relatively uniform surface.Here, we report disk-resolved observations of Ceres with SINFONI (ESO VLT) in the 1.17-1.32 μm and 1.45-2.35 μm wavelength ranges. The observations were made under excellent seeing conditions (0.6″), allowing us to reach a spatial resolution of ˜75 km on Ceres' surface. We do not find any spectral variation above a 3% level, suggesting a homogeneous surface at our spatial resolution. Slight variations (about 2%) of the spectral slope are detected, geographically correlated with the albedo markings reported from the analysis of the HST and Keck disk-resolved images of Ceres (Li et al. [2006], Icarus 182, 143; Carry et al. [2008], Astron. Astrophys. 478, 235). Given the lack of constraints on the surface composition of Ceres, however, we cannot assert the causes of these variations. [less ▲]

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See detailGestion de la diversité: nouveaux enjeux
Cornet, Annie ULg

Conference (2012, January)

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See detailThe Values of the European Union : Elements of a European Identity
Michel, Quentin ULg

Learning material (2012)

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See detailThe CphAII protein from Aquifex aeolicus exhibits a metal-dependent phosphodiesterase activity
Kupper, Michaël; Bauvois, Cédric; Frère, Jean-Marie ULg et al

in Extremophiles : Life Under Extreme Conditions (2012), 16(1)

The CphAII protein from the hyperthermophile Aquifex aeolicus shows the five conserved motifs of the metallo-β-lactamase (MBL) superfamily and presents 28% identity with the Aeromonas hydrophila subclass ... [more ▼]

The CphAII protein from the hyperthermophile Aquifex aeolicus shows the five conserved motifs of the metallo-β-lactamase (MBL) superfamily and presents 28% identity with the Aeromonas hydrophila subclass B2 CphA MBL. The gene encoding CphAII was amplified by PCR from the A. aeolicus genomic DNA and overexpressed in Escherichia coli using a pLex-based expression system. The recombinant CphAII protein was purified by a combination of heating (to denature E. coli proteins) and two steps of immobilized metal affinity chromatography. The purified enzyme preparation did not exhibit a β-lactamase activity but showed a metal-dependent phosphodiesterase activity versus bis-p-nitrophenyl phosphate and thymidine 5'-monophosphate p-nitrophenyl ester, with an optimum at 85°C. The circular dichroism spectrum was in agreement with the percentage of secondary structures characteristic of the MBL αββα fold. [less ▲]

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