Non-LTE Abundances and Consequences for the Evolution of the alpha elements in the Galaxy

Abundances of alpha-elements such as Ca and Mg in disk and halo stars are usually derived from equivalent widths lines measured on high resolution spectra, and assuming Local Thermodynamic Equilibrium (LTE) . In this paper, we present non-LTE differential abundances derived by computing the statistical equilibrium of CaI and MgI atoms, using high resolution equivalent widths available in the literature for 252 dwarf to subgiant stars. These non-LTE abundances combined with recent determination of non-LTE abundances of iron, seem to remove the dispersion of the [Ca/Fe] and [Mg/Fe] ratios in the galactic halo and disk phases, revealing new and surprising structures. These results have important consequences for chemical evolution models of the Galaxy. In addition, non-LTE abundance ratios for stars belonging to the M92 cluster apparently have the same behavior. More high resolution observations, mainly of globular clusters, are urgently needed to confirm our results.Comment: 15 pages, 3 tables, 7 figure

Du champion national au champion international:Résistance et transformations d’un modèle de concurrence dans le secteur énergétique des années 1990-2000

Cet article s’intéresse aux institutions forgeant le fonctionnement de l’économie. Il prend pour cas d’étude le modèle du champion national, porté dans les années 1990 par la Direction de l’énergie, puis par l’Agence des participations de l’État. Ce modèle, fortement remis en cause par les coups de boutoir de la Commission européenne et la privatisation d’une partie du secteur de l’énergie, a été adapté au cours de ces deux dernières décennies. D’abord considérées comme des outils de politiques publiques, des entreprises sont encouragées dans leur développement pour des raisons financières. Il est par ailleurs montré que la dynamique graduelle de cette institution est largement tributaire des hauts fonctionnaires, qui adaptent le modèle aux exigences de la Commission européenne

Asteroseismology and calibration of alpha Cen binary system

Using the oscillation frequencies of alpha Cen A recently discovered by Bouchy & Carrier, the available astrometric, photometric and spectroscopic data, we tried to improve the calibration of the visual binary system alpha Cen. With the revisited masses of Pourbaix et al. (2002) we do not succeed to obtain a solution satisfying all the seismic observational constraints. Relaxing the constraints on the masses, we have found an age t_alpha Cen=4850+-500 Myr, an initial helium mass fraction Y_i = 0.300+-0.008, and an initial metallicity (Z/X)_i=0.0459+-0.0019, with M_A=1.100+-0.006M_o and M_B=0.907+-0.006M_o for alpha Cen A&B.Comment: accepted for publication as a letter in A&

État et secteur énergétique en France : quels dirigeants pour quelles relations ?

Depuis la fin des années 1980, l’État a engagé un mouvement de retrait de la gestion des entreprises nationalisées. L’environnement institutionnel des firmes industrielles a de ce fait fortement évolué. Elles se sont internationalisées et nombre de marchés ont été libéralisés. Comment ces mouvements se sont-ils traduits dans les relations entre l’État et les grandes entreprises ? On se propose, dans cet article, de répondre à cette question en prenant pour cas le secteur de l’énergie, au sein duquel l’État joue un rôle actionnarial fort au début des années 1990. En considérant les dirigeants des plus grandes firmes de ce secteur comme autant de ressources pour les entreprises, on spécifiera les stratégies mises en œuvre par les firmes, qui révèlent un recours à l’État et notamment à la sphère politique. Les transformations des propriétés sociales des dirigeants énergéticiens ont suivi un double mouvement durant les deux dernières décennies. Jouant sur deux tableaux, les firmes affichent leur indépendance vis-à-vis de l’État via les conseils d’administration, tout en renforçant des liens informels avec la sphère politique via leurs comités exécutifs.Since the end of the 1980s the state has been engaged in a withdrawal from the management of nationalized businesses. The institutional environment for industrial firms has changed considerably as a result. Firms have internationalized and a number of markets have been liberalized. What has been the result of these changes for relations between the state and big business? In this article I set out to respond to this question looking at the case of the energy sector, in which the state has played a large role as a shareholder since the beginning of the 1990s. Considering the managers of the largest firms in this sector to be business resources, I will identify the strategies implemented by these firms, which reveal recourse to the state and notably the political sphere. The changes to the social properties of the energy sector managers have proceeded in two directions during the last two decades. The firms have it both ways, exhibiting both their independence from the state through administrative boards, while reinforcing informal ties with the political sphere through their executive committees

Extensions matérielles pour processeurs embarqués de traitement d'images.

12pLe marché des imageurs embarqués est entré dans une ère nouvelle avec l'avènement des téléphones portables munis d'appareils photographiques et de caméras. Il est attendu qu'à l'horizon 2009, leur nombre dépassera celui de l'ensemble des appareils photos vendus depuis l'invention de la photographie, et ce qu'ils soient numériques ou non. Le marché des imageurs électroniques embarqués est donc un secteur porteur, notamment au travers de la téléphonie et de la visiophonie mobile. Les applications ne sont plus limitées à la simple photographie ou la transmission de vidéo ; les lecteurs de codes matrices, la reconnaissance de visages, la biométrie, ou la vision 3D sont des exemples parmi les très nombreuses applications émergentes. L'implémentation de ces applications au sein de dispositifs mobiles requiert une grande flexibilité des composants que les IP dédiées largement utilisées jusqu'alors ne permettent pas. C'est pourquoi des solutions basées sur de processeurs programmables s'avèrent indispensables. Nous proposons dans ce papier des extensions destinées à améliorer les performances des processeurs dédiés au traitement d'image, nous démontrons que ces extensions apportent des améliorations de 60% sur l'ensemble de la chaîne d'acquisition et d'amélioration d'images utilisées derrière le capteur vidéo, ce qui indique le potentiel de ce type d'unité de calcul pour le support des applications à venir

Synthesis of oligo- and polythiophenes in zeolite hosts

Oligomers and polymers of thiophene derivatives were synthesized in the channels of zeolite Y and mordenite. Intrazeolite oxidation of monomers such as thiophene , 3- methylthiophene , and bithiophene by Fe(lll) or Cu(ll) ions results in formation of insoluble polymers that have spectroscopic properties similar to the corresponding bulk polymers. The zeolites containing the polymers are nonconducting, but when extracted from the host, the polymers show d.c. conductivities typical for t he bulk materials. Oligothiophene species with welldefined electronic transitions could be produced in acidic zeolite Y

Stellar Iron Abundances: non-LTE Effects

We report new statistical equilibrium calculations for Fe I and Fe II in the atmosphere of Late-Type stars. We used atomic models for Fe I and Fe II having respectively 256 and 190 levels, as well as 2117 and 3443 radiative transitions. Photoionization cross-sections are from the Iron Project. These atomic models were used to investigate non-LTE effects in iron abundances of Late-Type stars with different atmospheric parameters. We found that most Fe I lines in metal-poor stars are formed in conditions far from LTE. We derived metallicity corrections of about 0.3 dex with respect to LTE values, for the case of stars with [Fe/H] ~ -3.0. Fe II is found not to be affected by significant non-LTE effects. The main non-LTE effect invoked in the case of Fe I is overionization by ultraviolet radiation, thus classical ionization equilibrium is far to be satisfied. An important consequence is that surface gravities derived by LTE analysis are in error and should be corrected before final abundances corrections. This apparently solves the observed discrepancy between spectroscopic surface gravities derived by LTE analyses and those derived from Hipparcos parallaxes. A table of non-LTE [Fe/H] and log g values for a sample of metal-poor late-type stars is given.Comment: 22 pages, 9 figures, 1 table, ApJ style, accepte

Efficient Tools for Computing the Number of Breakpoints and the Number of Adjacencies between two Genomes with Duplicate Genes

International audienceComparing genomes of different species is a fundamental problem in comparative genomics. Recent research has resulted in the introduction of different measures between pairs of genomes: reversal distance, number of breakpoints, number of common or conserved intervals, etc. However, classical methods used for computing such measures are seriously compromised when genomes have several copies of the same gene scattered across them. Most approaches to overcome this difficulty are based either on the exemplar model, which keeps exactly one copy in each genome of each duplicated gene, or on the maximum matching model, which keeps as many copies as possible of each duplicated gene. The goal is to find an exemplar matching, respectively a maximum matching, that optimizes the studied measure. Unfortunately, it turns out that, in presence of duplications, this problem for each above-mentioned measure is NP-hard. In this paper, we propose to compute the minimum number of breakpoints and the maximum number of adjacencies between two genomes in presence of duplications using two different approaches. The first one is a (exact) generic 0–1 linear programming approach, while the second is a collection of three heuristics. Each of these approaches is applied on each problem and for each of the following models: exemplar, maximum matching and intermediate model, that we introduce here. All these programs are run on a well-known public benchmark dataset of -Proteobacteria, and their performances are discussed

eISP, une architecture de calcul programmable pour l'amélioration d'images sur téléphone portable.

4 pagesToday's smart phones, with their embedded high-resolution video sensors, require computing capacities that are too high to easily meet stringent silicon area and power consumption requirements (some one and a half square millimeters and half a watt) especially when programmable components are used. To develop such capacities, integrators still rely on dedicated low resolution video processing components, whose drawback is low flexibility. With this in mind, our paper presents eISP {--} a new, fully programmable Embedded Image Signal Processor architecture, now validated in {TSMC~65nm} technology to achieve a capacity of {16.8~GOPs} at {233~MHz}, for {1.5~mm$^2$} of silicon area and a power consumption of {250~mW}. Its resulting efficiency ({67~MOPs/mW}), has made eISP the leading programmable architecture for signal processing, especially for {HD~1080p} video processing on embedded devices such as smart phone