Compétences sur l'internet : adaptation, résistance des utilisateurs de P2P et mobilisation des internautes pour intervenir dans le débat public

International audienceThis communication aims to present collaboratives practices, share of information, exchanges between netsurfers, networks of training and capacities of organization, mobilization and debates on the Internet.Cette communication vise à présenter des pratiques collaboratives, de partage d'information, d'échanges entre internautes, des réseaux d'apprentissage et des capacités d'organisation, de mobilisation et de débats sur l'internet

An Impedance Investigation of the Mechanism of Pure Magnesium Corrosion in Sodium Sulfate Solutions

The corrosion behavior of pure magnesium in sodium sulfate solutions was investigated using voltammetry and electrochemical impedance spectroscopy with a rotating disk electrode. The analysis of impedance data obtained at the corrosion potential was consistent with the hypothesis that Mg corrosion is controlled by the presence of a very thin oxide film, probably MgO, and that the dissolution occurs at film-free spots only. This hypothesis was substantiated both by the superposition of the EIS diagrams, obtained for different immersion times and for two Na2SO4 concentrations once normalized, and by use of scanning electrochemical microscopy in the ac mode to sense the local conductivity of the material. On the basis of the electrochemical results, a model was proposed to describe magnesium corrosion at the open-circuit potential. Simulation of the impedance diagrams was in good agreement with the experimental results

Phénotypage métabolique du coeur sain et malade basé sur l'analyse d'isotopomères de masse marqués au carbone 13 : implications du citrate

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Avignon 1976 – Se souvenir des belles choses

Avignon Eté 1976. Einstein on the Beach. Montpellier Hiver 2012. Einstein au Corum. Barbara m’a demandé de me souvenir, ça fait 35 ans que j’ai vu cet Opéra. Hier soir un savant a dit que c’était l’été des Beach Boys et que c’était pour ça qu’Einstein était sur la plage. Se souvenir des belles choses Avignon 26 Juillet 1976 Il fait chaud c’est l’année de canicule. Quelques jours après mon anniversaire le 21 Juillet J’ai 21 ans, j’écoute Barbara en boucle J’ai passé mon bac chez les Jésu..

Mobile Antibiotic Resistance Encoding Elements Promote Their Own Diversity

Integrating conjugative elements (ICEs) are a class of bacterial mobile genetic elements that disseminate via conjugation and then integrate into the host cell genome. The SXT/R391 family of ICEs consists of more than 30 different elements that all share the same integration site in the host chromosome but often encode distinct properties. These elements contribute to the spread of antibiotic resistance genes in several gram-negative bacteria including Vibrio cholerae, the agent of cholera. Here, using comparative analyses of the genomes of several SXT/R391 ICEs, we found evidence that the genomes of these elements have been shaped by inter–ICE recombination. We developed a high throughput semi-quantitative method to explore the genetic determinants involved in hybrid ICE formation. Recombinant ICE formation proved to be relatively frequent, and to depend on host (recA) and ICE (s065 and s066) loci, which can independently and potentially cooperatively mediate hybrid ICE formation. s065 and s066, which are found in all SXT/R391 ICEs, are orthologues of the bacteriophage λ Red recombination genes bet and exo, and the s065/s066 recombination system is the first Red-like recombination pathway to be described in a conjugative element. Neither ICE excision nor conjugative transfer proved to be essential for generation of hybrid ICEs. Instead conjugation facilitates the segregation of hybrids and could provide a means to select for functional recombinant ICEs containing novel combinations of genes conferring resistance to antibiotics. Thus, ICEs promote their own diversity and can yield novel mobile elements capable of disseminating new combinations of antibiotic resistance genes

Basaltic calderas: Collapse dynamics, edifice deformation, and variations of magma withdrawal

International audienceThe incremental caldera collapses of Fernandina (1968), Miyakejima (2000), and Piton de la Fournaise (2007) are analyzed in order to understand the collapse dynamics in basaltic setting and the associated edifice deformation. For each caldera, the collapse dynamics is assessed through the evolution of the (1) time interval T between two successive collapse increments, (2) amount of vertical displacement during each collapse increment, and (3) magma outflow rate during the whole collapse caldera process. We show from the evolution of T that Piton de la Fournaise and Fernandina were characterized by a similar collapse dynamics, despite large differences in the caldera geometry and the duration of the whole collapse caldera process. This evolution significantly differs from that of Miyakejima where T strongly fluctuated throughout the whole collapse process. Quantification of the piston vertical displacements enables us to determine the magma outflow rates between each collapse increment. Displacement data (tiltmeter and/or GPS) for Piton de la Fournaise and Miyakejima are used to constrain the edifice overall deformation and the edifice deformation rates. These data reveal that both volcanoes experienced edifice inflation once the piston collapsed into the magma chamber. Such a deformation, which lasts during the first collapse increments only, is interpreted as the result of larger volume of piston intruded in the magma chamber than magma withdrawn before each collapse increment. Once the effect of the collapsing rock column vanishes, edifice deflates. We also determine for each caldera the critical amount of magma evacuated before collapse initiation and compare it to analog models. The significant differences between models and nature are explained by the occurrence of preexisting weak zones in nature, i.e., the ring faults, that are not taken into account in analog models. Finally, we show that T at Piton de la Fournaise and Fernandina was equally controlled by the frictional resistance along the ring faults and the magma outflow rate. In addition to these two parameters, the collapse dynamics of Miyakejima was also influenced by variations of the magma bulk modulus, which changed after the influx of deep gas-rich magma into the collapse-related magma chamber. Altogether, our results show that the dynamics of caldera collapse in basaltic volcanoes proceeds in two phases: Phase 1, starting with the first collapse, is characterized by the largest collapse amplitude, an incremental edifice inflation, and a step-by-step increase of the rate of magma outflow. Phase 2 shows a rapid decrease of the magma discharge rate to a low level concomitant with the continuous edifice deflation. If deep magma is injected into the magma chamber, as at Miyakejima, an additional phase occurs (phase 3)

Le trésor de deniers mérovingiens de Rodez (Aveyron). Circulation et diffusion des monnayages d'argent dans le Sud de la France au milieu du VIIIe siècle

International audienceIn 2002, a small hoard comprising nine Merovingian deniers has been discovered in a burial at Rodez (Aveyron, France). The combination of numismatic study and elementary analysis seems to indicate a concealment date circa 750-760 which is the transitional period between the Merovingians and the Carolingians.En 2002, un petit trésor de neuf deniers mérovingiens a été découvert dans une sépulture à Rodez (Aveyron, France). L'étude numismatique et les analyses élémentaires de composition des alliages permettent d'envisager son enfouissement dans les années 750-760, soit une date charnière entre la fin du pouvoir mérovingien et l'avènement du pouvoir carolingien