Risque environnemental et action collective : l’exemple de la gestion du risque d’érosion à Wissant (Côte d’Opale)

Cet article vise à mettre en question les rapports qui s’établissent entre les risques environnementaux, leur perception par les acteurs et les mesures qui sont effectivement prises face à ces risques. Il interroge donc le risque environnemental sous l’angle de sa mesure, de sa définition et de sa perception. Il envisage ensuite les modalités de réponse engagées par les acteurs sous le prisme des théories et des pratiques de l’action collective. Pour analyser plus en détails les rapports qui s’établissent entre risque environnemental et action collective, nous proposons de revenir tout d’abord sur les ambiguïtés soulevées par la notion de risque environnemental afin d’en mieux saisir les enjeux problématiques. Ceci nous permet de nous concentrer ensuite sur la thématique de l’action collective, qui émerge comme une des questions récurrentes lorsque l’on traite de la gestion des risques environnementaux. Nous proposons alors une méthodologie d’étude de l’action collective qui permet d’interroger plus particulièrement le rôle des politiques publiques dans les mécanismes de prévention et de gestion des risques environnementaux. Enfin, en nous focalisant sur le risque d’érosion sur le littoral de la Côte d’Opale (France), nous présentons une analyse de l’action publique menée ces dernières années pour faire face à ce risque.This article aims at appraising the relationships between environmental risks, their perception by the actors and the measurements which are really taken faced with these risks. It questions environmental risk therefore under the angle of its measure, definition and perception. It confronts then the answers proposed by the actors with theories and practices of collective action. To analyse more in details the relationships between environmental risk and collective action, we first come back on the ambiguities raised by the notion of environmental risk to better understand the problems at stake. This better understanding allows us to focus on the theme of collective action, which reappears again and again when studying environmental risk management. We propose a methodology for studying collective action, which focuses on the role of public policy in the mechanisms of environmental risk prevention and management. Finally, we present our analysis of the public action with respect to this risk over the last several years, concentrating on the erosion risks along the Opal Coast (France)

Bit-rate allocation for Multi-view video plus depth

International audienceThe efficient compression of multi-view-video-plus-depth (MVD) data raises the bit-rate allocation issue for the compression of texture and depth data. This question has not been solved yet because not all surveys reckon on a shared framework. This paper studies the impact of bit-rate allocation for texture and depth data relying on the quality of an intermediate synthesized view. The results show that depending on the acquisition configuration, the synthesized views require a different ratio between the depth and texture bit-rate: between 40\% and 60\% of the total bit-rate should be allocated to depth

How cracks are hot and cool: a burning issue for paper

International audienceMaterial failure is accompanied by important heat exchange, with extremely high temperature – thousands of degrees – reached at crack tips. Such temperature may subsequently alter the mechanical properties of stressed solids, and finally facilitate their rupture. Thermal runaway weakening processes could indeed explain stick-slip motions and even be responsible for deep earthquakes. Therefore, to better understand catastrophic rupture events, it appears crucial to establish an accurate energy budget of fracture propagation from a clear measure of the various energy dissipation sources. In this work, combining analytical calculations and numerical simulations, we directly relate the temperature field around a moving crack tip to the part α of mechanical energy converted into heat. Monitoring the slow crack growth in paper sheets with an infrared camera, we measure a significant fraction α = 12% ± 4%. Besides, we show that (self-generated) heat accumulation could weaken our samples with microfibers combustion, and lead to a fast crack/dynamic failure/ regime

Cost-efficient optical network architectures

Abstract We conduct a throughput-cost study of several (hybrid) multi-tiered optical network architectures comprising two large groups of users, each in a distinct MAN, which wish to communicate over a WAN. Introduction We address the question of how to best use traditional electronic and emergent optical technology to create a terrestrial network with desirable scalability properties: a decreasing cost per user, per unit of traffic, as the number of users and individual user bandwidth demand increase. We conduct a throughput-cost comparison of several prominent network architectures, and hybrids of these architectures: optical flow switching (OFS), Tell-andGo (TaG), Electronic Packet Switching (EPS), and Generalized MultiProtocol Label/Lambda Switching (EPS/GMPLS). The context for comparison is two large groups of users, located in different MANs, which communicate over a WAN. Our network model, though simple in that it only considers the communication of two sets of users across a WAN, is a building block for more complex network topologies, and more importantly, captures the essence of the throughput-cost tradeoffs of more complex networks

3D coding tools final report

Livrable D4.3 du projet ANR PERSEECe rapport a été réalisé dans le cadre du projet ANR PERSEE (n° ANR-09-BLAN-0170). Exactement il correspond au livrable D4.3 du projet. Son titre : 3D coding tools final repor

Databases of homologous gene families for comparative genomics

International audienceBackground: Comparative genomics is a central step in many sequence analysis studies, from gene annotation and the identification of new functional regions in genomes, to the study of evolutionary processes at the molecular level (speciation, single gene or whole genome duplications, etc.) and phylogenetics. In that context, databases providing users high quality homologous families and sequence alignments as well as phylogenetic trees based on state of the art algorithms are becoming indispensable. Methods: We developed an automated procedure allowing massive all-against-all similarity searches, gene clustering, multiple alignments computation, and phylogenetic trees construction and reconciliation. The application of this procedure to a very large set of sequences is possible through parallel computing on a large computer cluster. Results: Three databases were developed using this procedure: HOVERGEN, HOGENOM and HOMOLENS. These databases share the same architecture but differ in their content. HOVERGEN contains sequences from vertebrates, HOGENOM is mainly devoted to completely sequenced microbial organisms, and HOMOLENS is devoted to metazoan genomes from Ensembl. Access to the databases is provided through Web query forms, a general retrieval system and a client-server graphical interface. The later can be used to perform tree-pattern based searches allowing, among other uses, to retrieve sets of orthologous genes. The three databases, as well as the software required to build and query them, can be used or downloaded from the PBIL (Pôle Bioinformatique Lyonnais) site at http://pbil.univ-lyon1.fr/

Neofunctionalization in Vertebrates: The Example of Retinoic Acid Receptors

Understanding the role of gene duplications in establishing vertebrate innovations is one of the main challenges of Evo-Devo (evolution of development) studies. Data on evolutionary changes in gene expression (i.e., evolution of transcription factor-cis-regulatory elements relationships) tell only part of the story; protein function, best studied by biochemical and functional assays, can also change. In this study, we have investigated how gene duplication has affected both the expression and the ligand-binding specificity of retinoic acid receptors (RARs), which play a major role in chordate embryonic development. Mammals have three paralogous RAR genes—RARα, β, and γ—which resulted from genome duplications at the origin of vertebrates. By using pharmacological ligands selective for specific paralogues, we have studied the ligand-binding capacities of RARs from diverse chordates species. We have found that RARβ-like binding selectivity is a synapomorphy of all chordate RARs, including a reconstructed synthetic RAR representing the receptor present in the ancestor of chordates. Moreover, comparison of expression patterns of the cephalochordate amphioxus and the vertebrates suggests that, of all the RARs, RARβ expression has remained most similar to that of the ancestral RAR. On the basis of these results together, we suggest that while RARβ kept the ancestral RAR role, RARα and RARγ diverged both in ligand-binding capacity and in expression patterns. We thus suggest that neofunctionalization occurred at both the expression and the functional levels to shape RAR roles during development in vertebrates