PPH dendrimers grafted on silica nanoparticles: surface chemistry, characterization, silver colloids hosting and antibacterial activity

Polyphosphorhydrazone (PPH) dendrimers have been grafted on silica nanoparticles, and the surface functions of the dendrimers have been derivatized to phosphonates with lateral poly(ethyleneglycol) (PEG) chains. All materials have been thoroughly characterized by MAS NMR, FT-IR, electron microscopy, TGA and elemental analysis. These materials successfully hosted silver and silver oxide nanoparticles. The resulting composites exhibit antibacterial activity

Les réseaux sociaux virtuels : un relais à la sociabilité et au capital social?

International audienceLe rôle du soutien social sur le bien-être au travail fait l'objet de recherches depuis de nombreuses années. Cette aide est souvent assimilée à un capital social que l'individu saurait plus ou moins bien manager. Si les modèles classiques prenaient généralement en compte les personnes physiquement proches du salarié étudié et les qualités de sociabilité de l'individu, leurs résultats sont désormais bien connus. Il s'agit pour nous d'aller plus loin en montrant que ce sont les individus les moins bien dotés en capital social et en qualités de sociabilité qui bénéficient le plus de leur comportement dans les réseaux virtuels. A travers une méthode quantitative (121 questionnaires collectés auprès d'utilisateurs des réseaux sociaux d'aide professionnelle), nous mettons en évidence le rôle des nouvelles formes de soutien. Nos résultats rendent justice à un nouveau modèle plus comportementaliste adapté aux salariés disposant de la sociabilité et du capital social les plus faibles

The spatio-temporal dynamics of neutral genetic diversity

International audienceThe notions of pulled and pushed solutions of reaction-dispersal equations introduced by Garnier et al. (2012) and Roques et al. (2012) are based on a decomposition of the solutions into several components. In the framework of population dynamics, this decomposition is related to the spatio-temporal evolution of the genetic structure of a population. The pulled solutions describe a rapid erosion of neutral genetic diversity, while the pushed solutions are associated with a maintenance of diversity. This paper is a survey of the most recent applications of these notions to several standard models of population dynamics, including reaction-diffusion equations and systems and integro-differential equations. We describe several counterintuitive results, where unfavorable factors for the persistence and spreading of a population tend to promote diversity in this population. In particular, we show that the Allee effect, the existence of a competitor species, as well as the presence of climate constraints are factors which can promote diversity during a colonization. We also show that long distance dispersal events lead to a higher diversity, whereas the existence of a nonreproductive juvenile stage does not affect the neutral diversity in a range-expanding population

Hydrogéologie des zones de faille du socle cristallin (implications en terme de ressources en eau pour le Massif Armoricain)

Les régions de socle cristallin, pourtant largement représentées à l'échelle mondiale, sont réputées pour leurs modestes ressources en eaux souterraines. La valorisation des eaux souterraines dans les régions de socle est majoritairement limitée aux formations altérées et fissurées de sub-surface. Cependant, ces ressources sont souvent négligées au profit des eaux de surface en raison de leurs faibles débits d'exploitation et de leurs vulnérabilités aux polluants anthropiques. De récentes études de prospection et de recherche ont révélé la présence de ressources souterraines importantes, au delà des horizons superficiels classiquement exploités. Cependant peu d'informations spécifiques à ces ressources profondes sont disponibles, notamment concernant la structure des systèmes aquifères et leurs particularités hydrogéologiques. Par cette étude nous mettons clairement en évidence la présence de ressources en eau conséquentes dans le socle cristallin profond du Massif Armoricain. Ces ressources sont associées à des systèmes de failles assurant des capacités de drainage des réservoirs de stockage connectés. Les réservoirs de stockage superficiels et bordiers assurent l'alimentation en eau du réseau de fracture principal. Cette capacité de drainage est dépendante de la géométrie du plan de faille perméable. Les failles sub-horizontales sont les structures les plus efficaces dans cette fonction. Le stockage dans les formations bordières au système de faille apparaît déterminant pour assurer un débit d'exploitation conséquent. Cette étude permet d'établir une conceptualisation générale de ces systèmes de faille, tant d'un point de vue hydrodynamique que géochimique, et apporte des pistes de réflexions pour la gestion et la protection de telles ressources en eau.Crystalline basement regions, although largely represented at continental scale, are characterized by a low groundwater resources availability. Groundwater in crystalline areas appear to be mostly limited to weathered and fractured reservoirs at sub-surface depths. But these resources are often disregarded in favor of surface water because of low yields and their vulnerability to anthropogenic contaminants. Recent specific studies have revealed the presence of significant groundwater resources beyond the superficial reservoirs traditionally exploited. However, only few specific information is available concerning these type of resources, especially concerning their structural aquifer morphology and their hydrogeological properties. This study demonstrates the presence of substantial groundwater resources in the Armorican Massif crystalline basement. These resources are associated to fault systems providing drainage capacity of connected reservoir storage. Water supply of the main permeable fault domain during pumping is ensured by sub-surface and burdened reservoir storage. The drainage capacity is dependent on the geometry of the main permeable fault. Sub-horizontal faults are the most efficient structures to warrant this function. Storage in burdened formations of the fault system appears to ensure high groundwater yield. This study establishes hydrodynamic and geochemical conceptualization of a fault system, and provides thinking points in term of management and protection to ensure groundwater resources availability.RENNES1-Bibl. électronique (352382106) / SudocSudocFranceF

Flow Induced Pulsations (FLIP) in 6-inch rough bore gas flexible pipes Test

International audienceSince the beginning of the 21 st century FLow-Induced Pulsations (FLIP) has been more and more experienced. The phenomenon is characterized by an acoustic wave that is created inside of the flexible pipe and that may lead to significant fatigue failure of the adjacent equipment. Flexible pipe integrity is not called into question regarding this phenomenon. In this context, a FLIP joint test involving an Oil Company, a Flexible Pipe supplier and a French research center was conducted end of 2016 at French laboratory in Poitiers. The test was performed in a 6'' internal diameter and 18-meter-long flexible pipe. Both flow directions were tested to assess the influence of the rounded edges of the carcass. On the one hand, this paper presents the experimental test setup and the main results that came out of the test. On the other hand, this paper also presents the comparison between tests results and analytical model outcome. Moreover, combining experiments and theoretical point of view enabled reproducing the phenomenon. A better understanding of the phenomenon will allow flexible pipes suppliers to propose mitigations or cancellation of FLIP to companies

Experimental analysis of the whistling of an industrial riser

International audienceThe acoustic field induced by a flow in a corrugated pipe has been studied for a long time. There has been renewed interest in the development of offshore gas exploitation using long riser lengths for gas transport. On such installations, the phenomenon can lead to a failure of the equipment adjacent to the risers. In this context, a Flow-Induced Pulsations (FLIP) test was performed in a 6" internal diameter and 18-meter-long flexible pipe. This riser was equipped with upstream and downstream measuring couplers on which were fixed hot wire velocity sensors, pressure sensors and microphones. A series of tests was conducted for various internal pressures and flow rates. We present a time-frequency analysis of the signals resulting from these tests as well as a correlation study between the various sensors. We observed that the signals measured in the whistling condition showed significant temporal and frequency fluctuations. We were able to show that the frequency fluctuations were related to the geometry of the riser. In addition, these analyses made it possible to show that the whistling exists at transverse acoustic frequencies of the riser while propagating at the convective velocity of the flow

INSTRUMENTED FLIP TEST AND STATIC PRESSURE INFLUENCE ON THE ONSET VELOCITY AND FREQUENCY ON AN INDUSTRIAL SCALE

International audienceSince the early 2000, Flow Induced Pulsations (FLIP) has been more and more encountered on platforms. This phenomenon generates high acoustic pressure pulsations that may cause noises up to one hundred and ten dB and significant fatigue stress levels in small piping either at topside or subsea equipment. The source of the phenomenon is inside of the flexible pipe but FLIP has no effect on it. Nevertheless, in case of FLIP experience companies may have to reduce their flow rate. Therefore, FLIP must be understood in order for the companies to avoid this constraint. In this frame, a FLIP test was performed with protagonists who are involved in the understanding of this phenomenon. The test was done in 2016 at CESAME Poitiers (France) in an eighteen meter-long and six-inch flexible pipe on an air open loop. The prototype was fully instrumented and pressures up to forty bars were tested and mass flow rates up to 6 kg.s-1 to reproduce the FLIP phenomenon. The test setup and signals analysis are presented in this paper. Moreover, FLIP onset velocities and frequencies are compared with TechnipFMC models. As a conclusion of this paper pressure influence for the six-inch tested on the FLIP initiation will be presented

Antiretroviral Treatment Start-Time during Primary SIVmac Infection in Macaques Exerts a Different Impact on Early Viral Replication and Dissemination

BACKGROUND: The time of infection is rarely known in human cases; thus, the effects of delaying the initiation of antiretroviral therapy (ART) on the peripheral viral load and the establishment of viral reservoirs are poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: Six groups of macaques, infected intravenously with SIV(mac251), were given placebo or antiretroviral therapy to explore reservoir establishment; macaques were treated for 2 weeks, with treatment starting 4 hours, 7 or 14 days after infection. Viral replication and dissemination were measured in the gut (rectum), in the lung and in blood and lymphoid tissues (peripheral lymph nodes), by quantifying viral RNA, DNA and 2LTR circles. We used immunohistochemistry (CD4 and CD68) to assess the impact of these treatments on the relative amount of virus target cells in tissue. Treatment that was started 4 hours post-infection (pi) decreased viral replication and dissemination in blood and tissue samples, which were assessed on day 14 (RNA/DNA/2LTR circles). The virus remained detectable and lymphoid tissues were activated in LN and the gut in both placebo- and ART-treated animals. Viral RNA in plasma continued to be lower in macaques treated seven days after infection; however, this was not the case for viral DNA in peripheral blood mononuclear cells. There was a small but significant difference in RNA and DNA levels in tissues between placebo- and ART-treated animals on day 21. When started 14 days after infection, treatment resulted in a limited decrease in the plasma viral load. CONCLUSIONS: Treatment that was started 4 hours after infection significantly reduced viral replication and dissemination. When started 7 days after infection, it was of slight virological benefit in peripheral blood and in tissues, and treatment was even less effective if started 14 days pi. These data favor starting ART no longer than one week after intravenous SIV(mac251) exposure