Analyse de la variabilité germinative de la vesce commune sous l’impact d’un stress Ferrique-Cadmique-Salin

Ce travail a pour but de voir l’impact de l’application d’une combinaison de stress abiotique sur la germination des graines de vesce commune ainsi que de visualiser les modifications physiologiques et histologiques au niveau des tissus racinaires sous l’influence de ces contraintes. De ce fait, une conduite de germination a été réalisée avec des graines de vesce commune dans différentes situations de combinaisons entre trois types de stress métallique-cadmique-salin et un suivi a été fait en se basant sur des caractères végétatifs bien déterminés. Les résultats montrent bien une nette différence entre les réponses des graines à l’application de stress séparément et entre les combinaisons de stress ainsi qu’une variabilité intra-espèce énorme vis-à-vis de différentes types de contraintes.Mots-clés : vesce commune, stress métallique-cadmique-salin, caractères végétatifs, modifications physiologiques et histologiques

Cherenkov Telescope Array Data Management

Very High Energy gamma-ray astronomy with the Cherenkov Telescope Array (CTA) is evolving towards the model of a public observatory. Handling, processing and archiving the large amount of data generated by the CTA instruments and delivering scientific products are some of the challenges in designing the CTA Data Management. The participation of scientists from within CTA Consortium and from the greater worldwide scientific community necessitates a sophisticated scientific analysis system capable of providing unified and efficient user access to data, software and computing resources. Data Management is designed to respond to three main issues: (i) the treatment and flow of data from remote telescopes; (ii) "big-data" archiving and processing; (iii) and open data access. In this communication the overall technical design of the CTA Data Management, current major developments and prototypes are presented.Comment: 8 pages, 2 figures, In Proceedings of the 34th International Cosmic Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions at arXiv:1508.0589

Calcium-dependent dephosphorylation of the histone chaperone DAXX regulates H3.3 loading and transcription upon neuronal activation.

Activity-dependent modifications of chromatin are believed to contribute to dramatic changes in neuronal circuitry. The mechanisms underlying these modifications are not fully understood. The histone variant H3.3 is incorporated in a replication-independent manner into different regions of the genome, including gene regulatory elements. It is presently unknown whether H3.3 deposition is involved in neuronal activity-dependent events. Here, we analyze the role of the histone chaperone DAXX in the regulation of H3.3 incorporation at activity-dependent gene loci. DAXX is found to be associated with regulatory regions of selected activity-regulated genes, where it promotes H3.3 loading upon membrane depolarization. DAXX loss not only affects H3.3 deposition but also impairs transcriptional induction of these genes. Calcineurin-mediated dephosphorylation of DAXX is a key molecular switch controlling its function upon neuronal activation. Overall, these findings implicate the H3.3 chaperone DAXX in the regulation of activity-dependent events, thus revealing a new mechanism underlying epigenetic modifications in neurons

The optical system of the H.E.S.S. imaging atmospheric Cherenkov telescopes, Part I: layout and components of the system

H.E.S.S. -- the High Energy Stereoscopic System -- is a new system of large imaging atmospheric Cherenkov telescopes, with about 100 m^2 mirror area for each of four telescopes, and photomultiplier cameras with a large field of view (5 degr.) and small pixels (0.16 degr.). The dish and reflector are designed to provide good imaging properties over the full field of view, combined with mechanical stability. The paper describes the design criteria and specifications of the system, and the individual components -- dish, mirrors, and Winston cones -- as well as their characteristics. The optical performance of the telescope as a whole is the subject of a companion paper.Comment: 28 pages, 20 figure

Observation of an extended VHE gamma-ray emission from MSH 15-52 with CANGAROO-III

We have observed the supernova remnant MSH 15-52 (G320.4-1.2), which contains the gamma-ray pulsar PSR B1509-58, using the CANGAROO-III imaging atmospheric Cherenkov telescope array from April to June in 2006. We detected gamma rays above 810 GeV at the 7 sigma level during a total effective exposure of 48.4 hours. We obtained a differential gamma-ray flux at 2.35 TeV of (7.9+/-1.5_{stat}+/-1.7_{sys}) \times 10^{-13} cm^{-2}s^{-1}TeV^{-1} with a photon index of 2.21+/-0.39_{stat}+/-0.40_{sys}, which is compatible with that of the H.E.S.S. observation in 2004. The morphology shows extended emission compared to our Point Spread Function. We consider the plausible origin of the high energy emission based on a multi-wavelength spectral analysis and energetics arguments.Comment: 9 pages, 9 figures, Accepted in Ap

PseudoGeneQuest – Service for identification of different pseudogene types in the human genome

<p>Abstract</p> <p>Background</p> <p>Pseudogenes, nonfunctional copies of genes, evolve fast due the lack of evolutionary pressures and thus appear in several different forms. PseudoGeneQuest is an online tool to search the human genome for a given query sequence and to identify different types of pseudogenes as well as novel genes and gene fragments.</p> <p>Description</p> <p>The service can detect pseudogenes, that have arisen either by retrotransposition or segmental genome duplication, many of which are not listed in the public pseudogene databases. The service has a user-friendly web interface and uses a powerful computer cluster in order to perform parallel searches and provide relatively fast runtimes despite exhaustive database searches and analyses.</p> <p>Conclusion</p> <p>PseudoGeneQuest is a versatile tool for detecting novel pseudogene candidates from the human genome. The service searches human genome sequences for five types of pseudogenes and provides an output that allows easy further analysis of observations. In addition to the result file the system provides visualization of the results linked to Ensembl Genome Browser. PseudoGeneQuest service is freely available.</p

Discovery of the Binary Pulsar PSR B1259-63 in Very-High-Energy Gamma Rays around Periastron with H.E.S.S

We report the discovery of very-high-energy (VHE) gamma-ray emission of the binary system PSR B1259-63/SS 2883 of a radio pulsar orbiting a massive, luminous Be star in a highly eccentric orbit. The observations around the 2004 periastron passage of the pulsar were performed with the four 13 m Cherenkov telescopes of the H.E.S.S. experiment, recently installed in Namibia and in full operation since December 2003. Between February and June 2004, a gamma-ray signal from the binary system was detected with a total significance above 13 sigma. The flux was found to vary significantly on timescales of days which makes PSR B1259-63 the first variable galactic source of VHE gamma-rays observed so far. Strong emission signals were observed in pre- and post-periastron phases with a flux minimum around periastron, followed by a gradual flux decrease in the months after. The measured time-averaged energy spectrum above a mean threshold energy of 380 GeV can be fitted by a simple power law F_0(E/1 TeV)^-Gamma with a photon index Gamma = 2.7+-0.2_stat+-0.2_sys and flux normalisation F_0 = (1.3+-0.1_stat+-0.3_sys) 10^-12 TeV^-1 cm^-2 s^-1. This detection of VHE gamma-rays provides unambiguous evidence for particle acceleration to multi-TeV energies in the binary system. In combination with coeval observations of the X-ray synchrotron emission by the RXTE and INTEGRAL instruments, and assuming the VHE gamma-ray emission to be produced by the inverse Compton mechanism, the magnetic field strength can be directly estimated to be of the order of 1 G.Comment: 10 pages, 8 figures, accepted in Astronomy and Astrophysics on 2 June 2005, replace: document unchanged, replaced author field in astro-ph entry - authors are all members of the H.E.S.S. collaboration and three additional authors (99+3, see document

Detailed spectral and morphological analysis of the shell type SNR RCW 86

Aims: We aim for an understanding of the morphological and spectral properties of the supernova remnant RCW~86 and for insights into the production mechanism leading to the RCW~86 very high-energy gamma-ray emission. Methods: We analyzed High Energy Spectroscopic System data that had increased sensitivity compared to the observations presented in the RCW~86 H.E.S.S. discovery publication. Studies of the morphological correlation between the 0.5-1~keV X-ray band, the 2-5~keV X-ray band, radio, and gamma-ray emissions have been performed as well as broadband modeling of the spectral energy distribution with two different emission models. Results:We present the first conclusive evidence that the TeV gamma-ray emission region is shell-like based on our morphological studies. The comparison with 2-5~keV X-ray data reveals a correlation with the 0.4-50~TeV gamma-ray emission.The spectrum of RCW~86 is best described by a power law with an exponential cutoff at $E_{cut}=(3.5\pm 1.2_{stat})$ TeV and a spectral index of $\Gamma$~$1.6\pm 0.2$. A static leptonic one-zone model adequately describes the measured spectral energy distribution of RCW~86, with the resultant total kinetic energy of the electrons above 1 GeV being equivalent to $\sim$0.1\% of the initial kinetic energy of a Type I a supernova explosion. When using a hadronic model, a magnetic field of $B$~100$\mu$G is needed to represent the measured data. Although this is comparable to formerly published estimates, a standard E$^{-2}$ spectrum for the proton distribution cannot describe the gamma-ray data. Instead, a spectral index of $\Gamma_p$~1.7 would be required, which implies that ~$7\times 10^{49}/n_{cm^{-3}}$erg has been transferred into high-energy protons with the effective density $n_{cm^{-3}}=n/ 1$ cm^-3. This is about 10\% of the kinetic energy of a typical Type Ia supernova under the assumption of a density of 1~cm^-3.Comment: accepted for publication by A&