La mise en ligne des informations liées aux risques : véritable outil de prévention ou alibi ?

International audienceCet article fait le point sur la mise en ligne des informations liées à deux types de risques (technologiques -inondations), à caractère industriel ou naturel, afin de déterminer si cette mise à disposition des informations peut constituer un véritable outil de prévention ou si elle ne représente, en fait, qu'un simple alibi pour les pouvoirs publics

Exocomets in the circumstellar gas disk of HD 172555

The source HD172555 is a young A7V star surrounded by a debris disk with a gaseous component. Here, we present the detection of variable absorption features detected simultaneously in the Ca II K and H doublet lines (at 3,933 and 3,968 Angstrom). We identified the presence of these absorption signatures at four different epochs in the 129 HARPS high-resolution spectra gathered between 2004 and 2011. These transient absorption features are most likely due to Falling Evaporating Bodies (FEBs, or exocomets) that produce absorbing gas observed transiting in front of the central star. We also detect a stable Ca II absorption component at the star's radial velocity. With no corresponding detection in the Na I line, the resulting very low upper limit for the NaI/CaII ratio suggests that this absorption is due to circumstellar gas.Comment: Accepted for publication in Astronomy&Astrophysics Letter

Detection of seismic site effects: Development of experimental methods and application to the city of Nice

Les effets de site représentent un enjeu important pour la prévention parasismique, puisqu’ils peuvent aggraver considérablement les dommages lors d’un séisme. La connaissance de la réponse des sols aux séismes permet d’adapter la réglementation parasismique à ces contraintes lors de l’élaboration de microzonages et de Plan de Prévention des risques. Les méthodes expérimentales de détermination des effets de site visent à obtenir les paramètres de l’amplification sismique par la mesure de séismes ou de bruit de fond sismique. Cet article présente les principaux résultats obtenus jusqu’en 2005 par l’ERA « Risque sismique » dans la mise au point de ces techniques et leur application comparée sur la ville de Nice. Cette ville a effectivement constitué le principal chantier d’application grâce à de multiples campagnes d’enregistrements sismiques. De nombreux séismes ont d’abord été analysés par la méthode des fonctions de transfert. La méthode « H/V bruit de fond » a été appliquée sur plus de 600 points et les résultats interpolés spatialement. Un modèle géotechnique du sous-sol a ensuite permis de comparer les résultats obtenus avec la géologie et des simulations numériques de la propagation des ondes. La complémentarité des méthodes et leurs atouts respectifs sont mis en valeur sur ce territoire à fort enjeu.Site effects represent a critical challenge in the field of earthquake prevention since these effects are capable of seriously exacerbating damage whenever an earthquake strikes. Knowledge of the soil response to seismic activity allows adapting earthquake protection regulations to better incorporate these constraints during the process of defining microzones and producing the Risk Prevention Plan. The experimental methods employed to determine site effects seek to obtain seismic amplification parameters by means of measuring earthquakes or seismic background noise. This article presents the main set of results derived until 2005 by the “Seismic risk” ERA research team during development of these techniques as well as their comparative application to Nice, a city that has constituted the main field application site thanks to its hosting of multiple seismic recording campaigns. For starters, many earthquakes have been analyzed according to the transfer function method. The “Horizontal/Vertical background noise” method was in particular applied to over 600 points, with results being spatially interpolated. A geotechnical model of the subsoil then served to compare the results output with both the geology and numerical simulations of wave propagation. The complementarity of methods and their respective advantages are highlighted in this seismically-active setting

Postnatal development of the astrocyte perivascular MLC1/GlialCAM complex defines a temporal window for the gliovascular unit maturation

International audienc

Does the pension system’s income statement really matter? A proposal for an NDC scheme with disability and minimum pension benefits

This paper develops an accounting model for monitoring the solvency of a notional defined contribution (NDC) pension scheme with disability and minimum pension benefits. Using the annual report of the Swedish pension system as a benchmark, the “Swedish” actuarial balance is extended by adding an income statement fully explaining the reasons behind the changes in the system’s solvency by type of benefit. In line with the reference model, assets and liabilities are measured at present value at each reporting date, and in each period, included as income or expenses on the Income statement. This accounting framework integrates both contributory and social aspects of public pensions and discloses the real cost of the disability contingency and the redistribution through minimum pensions. Apart from Sweden, this proposal could be especially interesting for improving the reporting of public pensions in countries such as Poland, Italy, Latvia and Norway