Apn1 AP-endonuclease is essential for the repair of oxidatively damaged DNA bases in yeast frataxin-deficient cells

International audienceFrataxin deficiency results in mitochondrial dysfunction and oxidative stress and it is the cause of the hereditary neurodegenerative disease Friedreich ataxia (FA). Here, we present evidence that one of the pleiotrop-ic effects of oxidative stress in frataxin-deficient yeast cells (Dyfh1 mutant) is damage to nuclear DNA and that repair requires the Apn1 AP-endonuclease of the base excision repair pathway. Major phenotypes of Dyfh1 cells are respiratory deficit, disturbed iron homeostasis and sensitivity to oxidants. These phenotypes are weak or absent under anaerobiosis. We show here that exposure of anaerobically grown Dyfh1 cells to oxygen leads to down-regulation of antioxidant defenses, increase in reactive oxygen species, delay in G1-and S-phases of the cell cycle and damage to mitochondrial and nuclear DNA. Nuclear DNA lesions in Dyfh1 cells are primarily caused by oxidized bases and single-strand breaks that can be detected 15-30 min after oxygen exposition. The Apn1 enzyme is essential for the repair of the DNA lesions in Dyfh1 cells. Compared with Dyfh1, the double Dyfh1Dapn1 mutant shows growth impairment, increased mu-tagenesis and extreme sensitivity to H 2 O 2. On the contrary, overexpression of the APN1 gene in Dyfh1 cells decreases spontaneous and induced mutagenesis. Our results show that frataxin deficiency in yeast cells leads to increased DNA base oxidation and requirement of Apn1 for repair, suggesting that DNA damage and repair could be important features in FA disease progression

Solar-like oscillations in a massive star

Seismology of stars provides insight into the physical mechanisms taking place in their interior, with modes of oscillation probing different layers. Low-amplitude acoustic oscillations excited by turbulent convection were detected four decades ago in the Sun and more recently in low-mass main-sequence stars. Using data gathered by the Convection Rotation and Planetary Transits mission, we report here on the detection of solar-like oscillations in a massive star, V1449 Aql, which is a known large-amplitude (b Cephei) pulsator.Comment: Published in Sience, 19 June 2009, vol. 324, p. 154

Radially Polarized Conical Beam from an Embedded Etched Fiber

We propose a method for producing a conical beam based on the lateral refraction of the TM01 mode from a two-mode fiber after chemical etching of the cladding, and for controlling its radial polarization. The whole power of the guided mode is transferred to the refracted beam with low diffraction. Polarization control by a series of azimuthal detectors and a stress controller affords the transmission of a stabilized radial polarization through an optical fiber. A solid component usable for many applications has been obtained

European collaborative efforts to achieve effective, safe, and cost-controlled dismantling of nuclear facilities

This paper aims to give an overview of very recent European coordinate efforts to implement technologies of the “4.0 Industry” in the nuclear deconstruction sector. This objective aims to benefit from the lever of efficiency and reliability represented by innovative technologies on all the value chain of the dismantling, from early characterization to the dismantling operations themselves through engineering studies, waste management, project management and coordination of multiple stakeholders of each project. The outcomes of five projects (INNO4GRAPH, LD-SAFE, PLEIADES, CLEANDEM and INSIDER) are summarized here. They result in a unique data and knowledge common base, as well as in a significant sharing of experience based on dismantling projects already carried out or to come. They also result in designing new tools or methods natively taking into account the needs of a maximum of dismantling operators, as well as new test facilities. This will allow the undertaken joint work and collaboration to be continued. All of this paves the way to further collaborative projects and developments, in order to continue to implement reliable new technologies and processes in European dismantling projects to make future dismantling operations more efficient, safer and more cost-effective

Asteroseismic analysis of the CoRoT \delta-Scuti star HD174936

We present an analysis of the \delta-Scuti star object HD 174936 (ID 7613) observed by CoRoT during the first short run SRc01 (27 days). A total number of 422 frequencies we are extracted from the light curve using standard prewhitening techniques. This number of frequencies was obtained by considering a spectral significance limit of sig = 10 using the software package SigSpec. Our analysis of the oscillation frequency spectrum reveals a spacing periodicity of around 52 \muHz. Although modes considered here are not in the asymptotic regime, a comparison with stellar models confirms that this signature may stem from a quasi-periodic pattern similar to the so-called large separation in solar-like stars.Comment: 7 pages, 7 figures, 2 tables. Accepted for publication in A&A CoRoT Special Featur

Référentiel de connaissances pour un numérique éco-responsable

L’objectif de ce document est de définir un référentiel/socle de connaissances commun pour les enseignements sur le numérique responsable (impacts du numérique et comment les limiter1), à destination de formations en informatique ou d’autres filières incluant des cours d’informatique.Nous cherchons à répondre à la question suivante :Quelles connaissances devrait apporter une formation en informatique à des étudiantes et étudiants pour leur permettre d’apporter des réponses aux enjeux environnementaux et sociétaux dans leur vie professionnelle et citoyenne ?Ce document est donc focalisé sur les impacts du numérique, mais certains aspects plus généraux(enjeux environnementaux, contexte économique...) sont néanmoins abordés car nécessaires à la compréhension des aspects informatiques.Ce référentiel vise à fournir des notions et références utiles, mais n’a pas vocation à remplacer un cours

Semi-empirical dissipation source functions for ocean waves: Part I, definition, calibration and validation

New parameterizations for the spectra dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observation of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is non-zero only when a non-dimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short wave dissipation due to long wave breaking is introduced to represent the dissipation of short waves due to longer breaking waves. Several degrees of freedom are introduced in the wave breaking and the wind-wave generation term of Janssen (J. Phys. Oceanogr. 1991). These parameterizations are combined and calibrated with the Discrete Interaction Approximation of Hasselmann et al. (J. Phys. Oceangr. 1985) for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spectra, and the variability of spectral moments with wind speed and wave height. The wave energy balance is verified in a wide range of conditions and scales, from gentle swells to major hurricanes, from the global ocean to coastal settings. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Some systematic defects are still present, but the parameterizations yield the best overall results to date. Perspectives for further improvement are also given.Comment: revised version for Journal of Physical Oceanograph