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GRB 081024B and GRB 140402A: two additional short GRBs from binary neutron star mergers
No full textInternational audienceTheoretical and observational evidences for a two-fold classification of short bursts have been recently obtained: (1) short gamma-ray flashes (S-GRFs), with isotropic energy erg and no black hole (BH) formation, and (2) authentic short gamma-ray bursts (S-GRBs), with isotropic energy erg showing evidence of BH formation in the binary neutron star merging process. The signature for BH formation is the onset of high-energy (0.1–100 GeV) emission, coeval to the prompt emission, in all S-GRBs. No GeV emission is expected nor observed in S-GRFs. In this paper, we present two S-GRBs, GRB 081024B and GRB 140402A, in addition to the already identified S-GRBs, GRB 090227B, GRB 090510, and GRB 140619B. We also return to the absence of GeV emission in the S-GRB 090227B, at an angle of from the Fermi-LAT boresight. All of the correctly identified S-GRBs correlate with high-energy emission, implying no significant presence of beaming in GeV emission. The existence of a common power-law behavior in the GeV luminosities, following the BH formation, when measured in the source rest frame, points to a commonality in the mass and spin of the newly formed BHs in all S-GRBs
Low tech ? Wild tech !
No full textInternational audienceOn ne compte plus aujourd'hui les appels à repenser l'innovation. Il y aurait urgence écologique. Et certains n'hésitent pas à prédire la fin du monde à moins d'une rupture radicale de nos modèles de croissance. Alors que chaque nouvelle génération de téléphone ou d'ordinateur est célébrée comme si elle constituait un progrès décisif pour l'humanité, le low tech à l'inverse, cet ensemble hétérogène de techniques, de modes de composition alternatifs, définis tantôt négativement (pauvreté ou économie de moyens) tantôt positivement (faire beaucoup avec peu de choses, faire avec ce qu'on a, faire plus local et plus participatif, etc.) viendrait partout ébranler la toute puissance du high tech. Avec lui, ce ne sont pas seulement une autre lecture des techniques et d'autres façons de concevoir qui se donnent à voir, mais des population entières d'hommes et de procédés, dont le rôle a bien souvent été sous-estimé, de l'Inde à l'Afrique en passant par l'Asie. L'objectif de ce numéro n'est pas de cataloguer les formes de résistance ou d'invention très diverses que recouvre l'étiquette de low tech, mais plutôt de poser les bases d'une cartographie alternative des modes d'assemblage à l'échelle planétaire, et de donner des outils pour mieux penser des manières de fabriquer qui échappent à toute classification
Modélisation du portage des salmonelles dans un élevage porcin
No full textThis report describes a stochastic simulation model which represents both the pig and sow population dynamics in a farrow-to- finish herd and the indirect Salmonella transmission within this herd. This model was initially developed during Amandine Lurette's PhD thesis . It was then picked up and extended as part of Justine Guillaumont's traineeship to integrate the various batch management systems encountered in Brittany. The effect of batch mixing and management systems were assessed using this model.Ce rapport décrit un modèle de simulation stochastique représentant la dynamique des populations de truies et de porcs dans un troupeau naisseur engraisseur et la transmission indirecte des Salmonelles au sein de ce troupeau. Ce modèle a été initialement développé pendant la thèse de doctorat d'Amandine Lurette Il a ensuite a été repris et étendu dans le cadre du stage de Justine Guillaumont, pour intégrer les différentes conduites en bandes rencontrées en Bretagne. L'effet du mélange de bandes et du type de conduite ont été évalués à partir de ce modèle
A free high resolution land cover on the small Indian Ocean islands, an example of its use with the study of vector-borne diseases
No full textInternational audienceThe southwest of the Indian Ocean comprises numerous islands of less than 3000 sq km (Comoros, Seychelles, Mascarene Islands). These small island territories have very fragmented and diversified environments. Satellite imagery and products at low and medium spatial resolution (usually from 4 kilometers to 250 meters) are not or poorly suited to the study of these areas. This is particularly the case for ecological studies such as the study of vector-borne diseases where the evaluation of interactions at a fine scale is critical to understand their spatial dynamics. To overcome this need, we realized a homogeneous land cover mapping of these small islands, by analysing SPOT 5 satellite images acquired between July 2013 and July 2014 by SEAS-OI Station. We used an object-based image analysis method to identify the 12 major classes of land cover / land use of these tropical islands. This methodology together with a good knowledge of the field has enabled us to achieve an overall accuracy of 85%, making it an operational product. In order to illustrate the importance of this dataset, we present its use in health research to describe thelocation of health observations: whether the place of residence of patients or the points of capture of disease vectors through several examples in Reunion, Mayotte, the Union of the Comoros and the Republic of Seychelles. In these studies, high resolution allows to provide very fine information on the surrounding environment, while little data is usually available at this scale. In the statistical analyzes, these data were mainly used to differentiate between infected and non-infected individuals. This high resolution landcover is available on a web portal to allow a wider distribution to researchers and thematicians using land cover information in their field
Fiber-draw-induced elongation and break-up of particles inside the core of a silica-based optical fiber
No full textInternational audienceParticles in the core of optical fibers are widely studied to tailor or to improve optical properties. The analysis of nanoparticles embedded in silica-based optical fiber allowed new observations of the evolution of amorphous particles during fiber drawing. Even at the nanoscale, competition between viscous stresses and surface tension on the particles induces elongation and even break-up of particles during the process. Indeed, particles between 140 and 200 nm diameter inside the preform can break up in fragments with diameters down to 60 nm inside the drawn fiber. Break-up of particles appears as a new " top-down " strategy to produce small particles. These observations are promising for micro/nanostructured and multiphasic optical fibers
BRC4Env : un réseau de Centres de Ressources Biologiques et de collections dédié aux ressources environnementales
No full textBRC4Env : un réseau de Centres de Ressources Biologiques et de collections dédié aux ressources environnementales. 6ème Séminaire du réseau d’écotoxicologie terrestre et aquatiqu
Cerium redox state in silicate glasses and melts: implications for properties change and structural roles
No full textInternational audienc
Simulation of three-dimensional nanoscale light interaction with spatially dispersive metals using a high order curvilinear DGTD method
No full textIn this work, we present and study a flexible and accurate numerical solver in the context of three-dimensional computational nanophotonics. More precisely, we focus on the propagation of electromagnetic waves through metallic media described by a non-local dispersive model. For this model, we propose a discretization based on a high-order Discontinuous Galerkin time-domain method, along with a low-storage Runge-Kutta time scheme of order four. The semi-discrete stability of the scheme is analyzed for classical numerical fluxes, i.e. centered and upwind.Furthermore, the numerical treatment is enriched with an enhanced approximation of the geometry based on isoparametric curvilinear meshes. We finally assess our approach on several test cases, from academic to more physical ones
Observations of the galaxy cluster CIZA J2242.8+5301 with the Sardinia Radio Telescope
No full textInternational audienceWe observed the galaxy cluster CIZA J2242.8+5301 with the Sardinia Radio Telescope to provide new constraints on its spectral properties at high frequency. We conducted observations in three frequency bands centred at 1.4 GHz, 6.6 GHz and 19 GHz, resulting in beam resolutions of 14, 2.9 and 1 respectively. These single-dish data were also combined with archival interferometric observations at 1.4 and 1.7 GHz. From the combined images, we measured a flux density of for the central radio halo and and for the northern and the southern relic respectively. After the spectral modelling of the discrete sources, we measured at 6.6 GHz and for the northern and southern relic respectively. Assuming simple diffusive shock acceleration, we interpret measurements of the northern relic with a continuous injection model represented by a broken power-law. This yields an injection spectral index and a Mach number , consistent with recent X-ray estimates. Unlike other studies of the same object, no significant steepening of the relic radio emission is seen in data up to 8.35 GHz. By fitting the southern relic spectrum with a simple power-law () we obtained a spectral index corresponding to a Mach number () in agreement with X-ray estimates. Finally, we evaluated the rotation measure of the northern relic at 6.6 GHz. These results provide new insights on the magnetic structure of the relic, but further observations are needed to clarify the nature of the observed Faraday rotation
Radio selection of the most distant galaxy clusters
No full textInternational audienceWe show that the most distant X-ray-detected cluster known to date, Cl J1001 at , hosts a strong overdensity of radio sources. Six of them are individually detected (within ) in deep 0\buildrel{\prime\prime}\over{.} 75 resolution VLA 3 GHz imaging, with . Of the six, an active galactic nucleus (AGN) likely affects the radio emission in two galaxies, while star formation is the dominant source powering the remaining four. We searched for cluster candidates over the full COSMOS 2 deg(2) field using radio-detected 3 GHz sources and looking for peaks in density maps. Cl J1001 is the strongest overdensity by far with , with a simple preselection. A cruder photometric rejection of radio foregrounds leaves Cl J1001 as the second strongest overdensity, while even using all radio sources Cl J1001 remains among the four strongest projected overdensities. We conclude that there are great prospects for future deep and wide-area radio surveys to discover large samples of the first generation of forming galaxy clusters. In these remarkable structures, widespread star formation and AGN activity of massive galaxy cluster members, residing within the inner cluster core, will ultimately lead to radio continuum as one of the most effective means for their identification, with detection rates expected in the ballpark of 0.1–1 per square degree at . Samples of hundreds such high-redshift clusters could potentially constrain cosmological parameters and test cluster and galaxy formation models