MESURE DE LA TEMPÉRATURE RÉSIDUELLE DES MATÉRIAUX SOUMIS À UN CHOC INTENSE

We describe an experimental measurement technique which permits to evaluate the free surface temperature of a shock loaded metallic sample. The radiative infrared emission is carried over from the firing chamber to the pyrometer by a fluoride glass fiber. The pyrometer and the measurement technique are described. The free surface temperature of a shock loaded polished aluminum sample is measured and discussed

Politiques de synchronisation dans les systèmes multi-agents distribués parallèles

National audienceParmi les méthodes de modélisation/simulation, les systèmes multi-agents présentent un intérêt particulier pour simuler les systèmes complexes. Lorsque la taille des modèles croît, le recours aux systèmes multi-agents parallèles est nécessaire mais pose de nombreux problèmes. Dans cet article, nous nous intéressons à l'impact de la synchronisation sur la définition des modèles et leur exécution. Nous mettons en évidence des problématiques de synchronisation à travers des instances de modèles puis nous analysons expérimentalement l'impact des politiques de synchronisation sur des exécutions de grande taille

Local distribution of macrophytes and consequences for sampling methods in large rivers

During the years 2003 and 2004, the distribution of macrophytes was studied at eight sites in two large rivers in the southwest of France (the Dordogne and Garonne). Using a pinpoint method, we obtained 7,083 observations and recorded physical parameters such as depth, distance from bank, water velocity, and substrate type. By using logistic regressions, we showed that a combination of these factors significantly influences the distribution of macrophytes. This enabled us to highlight transversal distribution patterns. Helophyte spermatophytes, free-floating taxa, and most of the nonanchored algae were characteristic of the shallow areas located near the banks. The deepest areas were characterized by a reduced number of species with a majority of submerged spermatophytes which are resistant to high velocity, anchored algae, and bryophytes. These results can be used to implement the Macrophyte Biological Index for Rivers (IBMR) for large rivers

Zoom sur les communautés phytoplanctoniques et sur la faune benthique d’un tronçon court-circuité du Bas-Rhône (espèces ordinaires ou invasives?)

International audienceEcological monitoring of the French Rhône River, around the nuclear power plant on the Montélimar dam (CNPE Cruas-Meysse), provides an estimate of interannual change in several physical-chemical and biological parameters (phytoplankton and benthic fauna). This study presents hydrobiological monitoring results since 2007, an integral part of the long-term time series data collected since the initial studies. Algae communities upstream and downstream from Cruas are mainly composed of diatoms, as in most European rivers. Since 2010, the proportion of Chlorophyceae and Cyanobacteria has been increasing. For benthic fauna, there has been a significant change in the population since 2004, with the appearance and settlement of more than ten exotic taxa, some of them invasive, such as the crustacean Amphipodes Dikerogammarus, or very abundant, such as Isopodes Jaera istri. Others show very considerable interannual variations in their abundance (Corophium, Hypania invalida, Hemimysis anomala), which is a sign that environmental conditions often change, in particular temperatures. Nevertheless, the population of native macroinvertebrates seems to have been declining sharply in recent years.La surveillance écologique du fleuve Rhône, au droit du Centre Nucléaire de Production Électrique (CNPE Cruas-Meysse) implanté sur la retenue de Montélimar, permet d'évaluer l'évolution interannuelle d'un certain nombre de paramètres physico-chimiques et biologiques (phytoplancton et faune benthique). Cette étude présente les résultats du suivi hydrobiologique depuis l’année 2007, partie intégrante de la chronique à long terme entreprise depuis les études initiales. Les communautés algales en amont et en aval de Cruas sont composées majoritairement de diatomées comme la plupart des fleuves européens. Depuis 2010, la proportion des Chlorophycées et des Cyanobactéries est en forte augmentation. Pour la faune benthique, un changement de peuplement est important depuis 2004, avec l’apparition et l’installation de plus d’une dizaine de taxons exotiques, certains devenus envahissants, comme les Crustacés Amphipodes Dikerogammarus, ou très abondants comme les Isopodes Jaera istri. D’autres ont des variations interannuelles d’abondances très importantes (Corophium, Hypania invalida, Hemimysis anomala), signes d’une forte variabilité des conditions environnementales, notamment thermiques. En revanche, les invertébrés autochtones semblent eux en forte régression depuis quelques années

Hypercholesterolemia increases coronary endothelial dysfunction, lipid content, and accelerated atherosclerosis after heart transplantation

Hyperlipidemia may increase endothelial damage and promote accelerated atherogenesis in graft coronary vasculopathy. To study the effects of hypercholesterolemia on coronary endothelial dysfunction, intimal hyperplasia, and lipid content, a porcine model of heterotopic heart transplantation, allowing nonacute rejection without immunosuppressive drugs, was used. A high cholesterol diet was fed to donor and recipient swine 1 month before and after transplantation. The endothelial function of coronary arteries of native and transplanted hearts from cholesterol-fed animals was studied in organ chambers 30 days after implantation and compared with endothelial function in arteries from animals fed a normal diet. The total serum cholesterol increased 3-fold in donors and recipients. Endothelium- dependent relaxations to serotonin, to the α2-adrenergic agonist UK14,304, and to the direct G-protein activator sodium fluoride were decreased significantly in allografted hearts compared with native hearts from both groups. Relaxations to the calcium ionophore A23187 and bradykinin were decreased significantly in allografts from animals fed the high cholesterol diet. The prevalence of intimal hyperplasia was significantly increased in coronary arteries from hypercholesterolemic swine. There was a significant increase in the lipid content of allograft arteries of hypercholesterolemic recipients. Hypercholesterolemia causes a general coronary endothelial dysfunction, increases the prevalence of intimal hyperplasia, and augments the incorporation of lipids in the vascular wall after heart transplantation. Hyperlipidemia accelerates graft coronary atherosclerosis through its effects on the endothelium.link_to_subscribed_fulltex

Zoom sur les communautés phytoplanctoniques et sur la faune benthique d’un tronçon court-circuité du Bas-Rhône (espèces ordinaires ou invasives?)

International audienceEcological monitoring of the French Rhône River, around the nuclear power plant on the Montélimar dam (CNPE Cruas-Meysse), provides an estimate of interannual change in several physical-chemical and biological parameters (phytoplankton and benthic fauna). This study presents hydrobiological monitoring results since 2007, an integral part of the long-term time series data collected since the initial studies. Algae communities upstream and downstream from Cruas are mainly composed of diatoms, as in most European rivers. Since 2010, the proportion of Chlorophyceae and Cyanobacteria has been increasing. For benthic fauna, there has been a significant change in the population since 2004, with the appearance and settlement of more than ten exotic taxa, some of them invasive, such as the crustacean Amphipodes Dikerogammarus, or very abundant, such as Isopodes Jaera istri. Others show very considerable interannual variations in their abundance (Corophium, Hypania invalida, Hemimysis anomala), which is a sign that environmental conditions often change, in particular temperatures. Nevertheless, the population of native macroinvertebrates seems to have been declining sharply in recent years.La surveillance écologique du fleuve Rhône, au droit du Centre Nucléaire de Production Électrique (CNPE Cruas-Meysse) implanté sur la retenue de Montélimar, permet d'évaluer l'évolution interannuelle d'un certain nombre de paramètres physico-chimiques et biologiques (phytoplancton et faune benthique). Cette étude présente les résultats du suivi hydrobiologique depuis l’année 2007, partie intégrante de la chronique à long terme entreprise depuis les études initiales. Les communautés algales en amont et en aval de Cruas sont composées majoritairement de diatomées comme la plupart des fleuves européens. Depuis 2010, la proportion des Chlorophycées et des Cyanobactéries est en forte augmentation. Pour la faune benthique, un changement de peuplement est important depuis 2004, avec l’apparition et l’installation de plus d’une dizaine de taxons exotiques, certains devenus envahissants, comme les Crustacés Amphipodes Dikerogammarus, ou très abondants comme les Isopodes Jaera istri. D’autres ont des variations interannuelles d’abondances très importantes (Corophium, Hypania invalida, Hemimysis anomala), signes d’une forte variabilité des conditions environnementales, notamment thermiques. En revanche, les invertébrés autochtones semblent eux en forte régression depuis quelques années