A ~6 Mpc overdensity at z = 2.7 detected along a pair of quasar sight lines: filament or protocluster?

Simulations predict that gas in the intergalactic medium (IGM) is distributed in filamentary structures that connect dense galaxy clusters and form the cosmic web. These structures of predominantly ionized hydrogen are difficult to observe directly due to their lack of emitting regions. We serendipitously detected an overdensity of log N(HI) > 18.0 absorbers at z = 2.69 along the lines of sight toward a pair of background quasars. Three main absorption regions spanning ~2000 km/s (corresponding to 6.4 (h_70)^(-1) Mpc proper) are coincident in the two lines of sight, which are separated by ~90 (h_70)^(-1) kpc transverse proper distance. Two regions have [Fe/H] < -1.9 and correspond to mild overdensities in the IGM gas. The third region is a sub-DLA with [Fe/H] = -1.1 that is probably associated with a galaxy. We discuss the possibility that the lines of sight probe along the length of a filament or intercept a galaxy protocluster

Extended Lyα\alpha emission around quasars with eclipsing damped Lyα\alpha systems

We present spectroscopic observations of six high redshift ($z_{\rm em}$ $>$ 2) quasars, which have been selected for their Lyman $\alpha$ (Ly$\alpha$) emission region being only partially covered by a strong proximate ($z_{\rm abs}$ $\sim$ $z_{\rm em}$) coronagraphic damped Ly$\alpha$ system (DLA). We detected spatially extended Ly$\alpha$ emission envelopes surrounding these six quasars, with projected spatial extent in the range 26 $\le$ $d_{\rm Ly\alpha}$ $\le$ 51 kpc. No correlation is found between the quasar ionizing luminosity and the Ly$\alpha$ luminosity of their extended envelopes. This could be related to the limited covering factor of the extended gas and/or due to the AGN being obscured in other directions than towards the observer. Indeed, we find a strong correlation between the luminosity of the envelope and its spatial extent, which suggests that the envelopes are probably ionized by the AGN. The metallicity of the coronagraphic DLAs is low and varies in the range $-$1.75 $<$ [Si/H] $<$ $-$0.63. Highly ionized gas is observed to be associated with most of these DLAs, probably indicating ionization by the central AGN. One of these DLAs has the highest AlIII/SiII ratio ever reported for any intervening and/or proximate DLA. Most of these DLAs are redshifted with respect to the quasar, implying that they might represent infalling gas probably accreted onto the quasar host galaxies through filaments.Comment: Accepted for publication in MNRAS, 27 pages, 19 figures, 6 table

Le médecin du travail face au harcèlement moral au travail : constats et prespectives

peer reviewedL'article de D. Faulx et C. Geuzaine, paru dans le numéro 3-2000 de cette revue, aborde l'étendue du phénomène du harcèlement moral ainsi que les aspects juridiques de la définition, la description du processus, ses conséquences médicales et les facteurs de risque. Dans la suite de cette étude, nous présentons ici les résultats d'une enquête menée auprès des médecins du travail, en tant que témoins et intervenants privilégiés dans le domaine du harcèlement. Cette enquête vise à apporter des informations descriptives originales concernant les attitudes, les opinions et représentations des médecins du travail par rapport au phénomène de harcèlement moral. En outre, elle est l'occasion de tester une série d'hypothèses sur les facteurs pouvant influencer l'attitude des médecins du travail vis-à-vis du harcèlement moral

Revue sur l’état actuel des connaissances des procédés utilisés pour l’élimination des cyanobactéries et cyanotoxines lors de la potabilisation des eaux

Les toxines cyanobactériennes sont des contaminants importants des écosystèmes aquatiques et constituent un risque pour la santé humaine. Les cyanobactéries peuvent libérer des toxines dans l’eau, particulièrement lors de la lyse des cellules qui se produit souvent au moment de leur passage à travers la filière conventionnelle de potabilisation des eaux. Dans cet article de revue de la littérature, les normes sur la qualité de l’eau concernant les toxines ainsi que les principales méthodes de détection des toxines sont d’abord présentées. Les méthodes d’élimination des cyanobactéries et des cyanotoxines sont ensuite décrites et leur performance discutée. Les procédés conventionnels présentés sont la coagulation/floculation, la clarification, la filtration sur sable, l’utilisation du charbon actif ainsi que l’oxydation chimique par chloration ou par le permanganate de potassium. Les méthodes alternatives présentement en développement pour optimiser les systèmes actuels de potabilisation des eaux ou remplacer les technologies conventionnelles trop peu efficaces pour l’élimination des polluants émergents (par ex., les procédés d’oxydation avancée et la filtration membranaire) sont également présentées. Des procédés conventionnels tels que la chloration peuvent s’avérer inadéquats, notamment par leur manque de fiabilité pour l’oxydation des cyanotoxines et par le risque encouru suite à la formation de sous-produits toxiques (par ex., les organochlorés). Des méthodes alternatives telles que la combinaison d’ozone et de peroxyde d’hydrogène permettent une oxydation fiable des cyanotoxines en assurant un effet rémanent à la sortie du contacteur. Ce type de traitement peut être facilement mis en oeuvre dans les usines de potabilisation des eaux possédant déjà une unité d’ozonation. L’utilisation du charbon actif, notamment sous forme de poudre, peut être efficace lors de contaminations ponctuelles par les fleurs d’eau de cyanobactéries. Ce document fait ainsi une synthèse de ces procédés chimiques, physiques ou physico-chimiques contribuant à l’élimination des cyanotoxines et des cyanobactéries lors de la potabilisation des eaux.Cyanobacterial toxins are important contaminants of aquatic ecosystems and present a risk for human health. Cyanobacteria can release toxins in water, particularly following cell lysis, which often happens during their passage through a conventional water treatment plant. In this literature review, water quality guidelines for the elimination of cyanotoxins and major detection methods of cyanotoxins are briefly presented. The processes used for cyanobacteria and cyanotoxin removal from drinking water are then reviewed and their performance discussed. The conventional methods presented are: coagulation/flocculation, clarification, sand filtration, activated carbon and chemical oxidation with chlorination or potassium permanganate. Alternative methods that are presently developed to enhance existing treatment plants or to replace conventional technologies that are less effective in removing emergent pollutants (e.g., advanced oxidation processes and membrane filtration) are also presented. Conventional methods such as chlorination can be inappropriate, notably because of their inability to fully oxidize cyanotoxins and the associated risk of formation of toxic by-products (e.g., organochlorinated compounds). Alternative methods such as the combination of ozone and hydrogen peroxide are more reliable to eliminate cyanotoxins, with a residual effect downstream from the treatment contactor. In addition, this type of treatment can be easily implemented in water treatment plants that are already using ozonation. The use of activated carbon, notably in the form of powder, can be efficient in the case of point contamination by cyanobacterial blooms. This document aims to synthesize these chemical, physical and physico-chemical methods to eliminate cyanotoxins and cyanobacteria during the treatment of drinking water

Detection of emission lines from z ~ 3 DLAs towards the QSO J2358+0149

Using VLT/X-shooter we searched for emission line galaxies associated to four damped Lyman-$\alpha$ systems (DLAs) and one sub-DLA at 2.73<=z<=3.25 towards QSO J2358+0149. We detect [O III] emission from a "low-cool" DLA at z_abs = 2.9791 (having log N(HI)=21.69+\-0.10, [Zn/H] = -1.83+\-0.18) at an impact parameter of, $\rho$ ~12 kpc. The associated galaxy is compact with a dynamical mass of (1-6)x10^9 M_solar, very high excitation ([O III]/[O II] and [O III]/[H$\beta$] both greater than 10), 12+[O/H]<=8.5 and moderate star formation rate (SFR <=2 M_solar yr^{-1}). Such properties are typically seen in the low-z extreme blue compact dwarf galaxies. The kinematics of the gas is inconsistent with that of an extended disk and the gas is part of either a large scale wind or cold accretion. We detect Ly$\alpha$ emission from the z_abs = 3.2477 DLA (having log N(HI)=21.12+\-0.10 and [Zn/H]=-0.97+\-0.13).The Ly$\alpha$ emission is redshifted with respect to the metal absorption lines by 320 km s^{-1}, consistent with the location of the red hump expected in radiative transport models. We derive SFR ~0.2-1.7 M_solar yr^{-1} and Ly$\alpha$ escape fraction of >=10 per cent. No other emission line is detected from this system. Because the DLA has a small velocity separation from the quasar (~500 km s^{-1}) and the DLA emission is located within a small projected distance ($\rho<5$ kpc), we also explore the possibility that the Ly$\alpha$ emission is being induced by the QSO itself. QSO induced Ly$\alpha$ fluorescence is possible if the DLA is within a physical separation of 340 kpc to the QSO. Detection of stellar continuum light and/or the oxygen emission lines would disfavor this possibility. We do not detect any emission line from the remaining three systems.Comment: 13 pages, 7 figures, 4 tables (3 pages, 5 figures, 5 tables in Appendix). Accepted for publication in MNRA

Comprehensive investigation of Ge-Si bonded interfaces using oxygen radical activation

In this work, we investigate the directly bonded germanium-silicon interfaces to facilitate the development of high quality germanium silicon hetero integration at the wafer scale. X-ray photoelectron spectroscopy data is presented which provides the chemical composition of the germanium surfaces as a function of the hydrophilic bonding reaction at the interface. The bonding process induced long range deformation is detected by synchrotron x-ray topography. The hetero-interface is characterized by measuring forward and reverse current, and by high resolution transmission electron microscopy. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3601355

Diversity of citron (Citrus medica) and phylogenetic analysis of related citron hybrids using molecular markers and essential oil composition

Citrus diversity is known to be essentially supported by three essential basic species, mandarin, pummelo and citron, which are at the origin of quite all the cultivated citrus. Based on studies of phenotype, the citron group (Citrus medica) is supposedly low in genetic diversity compared to mandarins and pummelos. To assess the diversity of the citron group we analyzed the molecular polymorphism of nuclear and cytoplasmic genetic markers and the variation in composition of essential oils from leaves and peels of 24 varieties of citron or apparent hybrids of citron. Our results demonstrate that the citron group has a relatively high allelic diversity, probably due to multiple introductions of different varieties. Self-fertilization was the mode of reproduction which most frequently led to the development of commercial varieties with specific aromas and flavors, such as the cultivar 'Corsican', a putative 'Common Poncire' self-crossed hybrid. However, some varieties appeared to be interspecific hybrids related to citron but only by the male parent. This varietal diversity was probably favored by spreading seeds to extend the cultivation of citron in Mediterranean countries. The chemical diversity does not always correspond to genetic diversity but nevertheless reveals specific profiles associated with some genotypes. (Résumé d'auteur