Loi du 23 février 2005, colonisations, indigènes, victimisations. Evocations binaires, représentations primaires

International audienceLoi du 23 février 200

Présidentielles maliennes : l'enracinement démocratique ?

International audienceLe 12 mai 2002, le général Amadou Toumani Touré, « tombeur » en 1991 du général-dictateur Moussa Traoré, a été élu Président de la République du Mali, après une décennie au pouvoir de l'ADEMA et d'Alpha Oumar Konaré. Ces élections présidentielles, qui inaugurent la première alternance malienne, marquent-elles une nouvelle étape de l'enracinement démocratique malien ? Les rumeurs persistantes d'arrangements occultes et les nombreuses irrégularités en révèlent-elles au contraire le dévoiement

Fusion Hindrance in the Heavy Ion Reactions -- Border Between the Normal and Hindered Fusions

The fusion hindrance in heavy ion collisions is studied in the framework of the two-center liquid drop model. It appears that the neck and the radial degrees of freedom might both be hampered by an inner potential barrier on their path between the contact configuration to the compound nucleus. Heavy ion reactions with and without the two kinds of fusion hindrance are classified through systematic calculations. It is found that the number of reactions without radial fusion hindrance is much smaller than that without neck fusion hindrance, and for both kinds of fusion hindrance the number of reactions without fusion hindrance at small mass-asymmetry parameter $\alpha$ is smaller than that at large $\alpha$. In the formation of a given compound nucleus, if a reaction with $\alpha_c$ is not hindered, then other reactions with $\alpha > \alpha_c$ are also not hindered as it is well known experimentally.Comment: 14 pages, 7 figure

Introduction aux incertitudes de mesures

Les incertitudes évaluées en utilisant les normes internationales sont entrées dans les programmes de terminales scientifiques. Les livres de physique, destinés aux élèves, sont un peu justes pour les enseignants. Cet article a pour objectif de présenter les notions nécessaires à une bonne application des formules utiles

Comparison between meteorological re-analyses from ERA-Interim and MERRA and measurements of daily solar irradiation at surface

International audienceThis paper compares the daily solar irradiation available at surface estimated by the MERRA (Modern-Era Retrospective Analysis for Research and Applications) re-analysis of the NASA and the ERA-Interim re-analysis of the European Center for Medium-range Weather Forecasts (ECMWF) against qualified ground measurements made in stations located in Europe, Africa and Atlantic Ocean. Using the clearness index, also known as atmospheric transmissivity or transmittance, this study evidences that the re-analyses often predict clear sky conditions while actual conditions are cloudy. The opposite is also true though less pronounced: actual clear sky conditions are predicted as cloudy. This overestimation of occurrence of clear sky conditions leads to an overestimation of the irradiation and clearness index by MERRA. The overall overestimation is less pronounced for ERA-Interim because the overestimation observed in clear sky conditions is counter-balanced by underestimation in cloudy conditions. The squared correlation coefficient for clearness index, also known as atmospheric transmissivity, ranges between 0.38 and 0.53, showing that a very large part of the variability in irradiation is not captured by the re-analyses. Within an irradiation homogeneous area, the variability of the bias, root mean square error and correlation coefficient are surprisingly large. MERRA and ERA-Interim should only be used in solar energy with proper understanding of the limitations and uncertainties. In regions where clouds are rare, e.g. North Africa, MERRA or ERA-Interim may be used to provide a gross estimate of monthly or yearly irradiation. Satellite-derived data sets offer less uncertainty and should be preferred

200 ans après Laplace, l’essor des méthodes bayésiennes d’analyse des données

International audienceInitiée par Pierre-Simon de Laplace il y a deux cents ans, l’analyse bayésienne des données expérimentales est en plein essor. Elle a fait son entrée dans certaines normes internationales de métrologie. Le but de cet article est d’introduire simplement le changement philosophique sous-jacent.Des applications à différents types de mesurages sont présentées

What can we learn from the fission of super-heavy elements?

The conference proceedings will be published by World Scientific PublishingNuclear shell model calculations predict the existence of super-heavy elements (SHE) that are tentatively synthesized through heavy-ion collisions. A complete description of the reaction to synthesize super-heavy elements is necessary to bridge these predictions with the experimental results on the fission time and residue cross sections. In this contribution, we will present the constraints that can be given on the shell correction energy from experimental data and the developments that are needed for the dynamical models. We will especially focus on the fission time of heavy elements and on the role of the isomeric potential pockets

Synthesis of superheavy elements: Uncertainty analysis to improve the predictive power of reaction models

13 pages, 13 figures, submitted for publication in PRCInternational audienceBackground: Synthesis of super-heavy elements is performed by heavy-ion fusion-evaporation reactions. However , fusion is known to be hindered with respect to what can be observed with lighter ions. Thus some delicate ambiguities remain on the fusion mechanism that eventually lead to severe discrepancies in the calculated formation probabilities coming from different fusion models. Purpose: In the present work, we propose a general framework based upon uncertainty analysis in the hope of constraining fusion models. Method: To quantify uncertainty associated with the formation probability, we propose to propagate uncertainties in data and parameters using the Monte-Carlo method in combination with a cascade code called KEWPIE2, with the aim of determining the associated uncertainty, namely the 95% confidence interval. We also investigate the impact of different models or options, which cannot be modeled by continuous probability distributions, on the final results. An illustrative example is presented in detail and then a systematic study is carried out for a selected set of cold-fusion reactions. Results: It has been rigorously shown that, at the 95% confidence level, the total uncertainty of the empirical formation probability appears comparable to the discrepancy between calculated values. Conclusions: The results obtained from the present study provide a direct evidence for predictive limitations of the existing fusion-evaporation models. It is thus necessary to find other ways to assess such models for the purpose of establishing a more reliable reaction theory, which is expected to guide future experiments on the production of super-heavy elements