Modélisation numérique du transport solide en suspension au cours d'une chasse: de la dynamique du réservoir à la propagation en aval

International audienceDam flushing is often performed to remove sediments of all sizes from reservoirs while minimizing downstream impacts. In this study, the reservoir flushing operation and the downstream transport of suspended sediments are simulated based on a numerical tool. The study site is the Arc River in the French Alps, focussing on two reaches: locally on the Saint Martin la Porte (SMLP) Reservoir and a few metres upstream (reach 1), and downstream the 120 km between the SMLP reservoir and the city of Grenoble (reach 2).The chosen numerical code is COURLIS, developed at EDF RD, and which could be coupled with codes of the open source Telemac-Mascaret system. The model was applied to the 2012 flushing event of the Arc River dams, which are managed by EDF (Electricity of France). The bed erosion and the suspended sediment transport dynamics in the most downstream reservoir (SMLP) were first computed. The initial state of the deposited fine sediment were defined using measured topographic data of the reservoir. The upstream boundary condition for the reach 2 model was set from estimated discharges and suspended sediment concentrations. The downstream study reach is approximately 120 km long, from SMLP dam to the city of Grenoble along the Arc and Isere rivers. Topographic data of the river bed were used to define the downstream river reach, taking into account the vegetated alternate bars. Water discharges and suspended sediment concentrations were also measured at several locations in the rivers downstream of the flushed reservoirs. A new formula is proposed to estimate two mean concentration values in the cross section: one for the main channel and the other for the overbank section. A good agreement with field data is obtained for both the reservoir and downstream reach dynamics. Moreover, the key role of the alternate bars in the fine sediment dynamics is highlighted, quantified and discussed

A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischaemic events (CAPRIE). CAPRIE Steering Committee

Many clinical trials have evaluated the benefit of long-term use of antiplatelet drugs in reducing the risk of clinical thrombotic events. Aspirin and ticlopidine have been shown to be effective, but both have potentially serious adverse effects. Clopidogrel, a new thienopyridine derivative similar to ticlopidine, is an inhibitor of platelet aggregation induced by adenosine diphosphate. METHODS: CAPRIE was a randomised, blinded, international trial designed to assess the relative efficacy of clopidogrel (75 mg once daily) and aspirin (325 mg once daily) in reducing the risk of a composite outcome cluster of ischaemic stroke, myocardial infarction, or vascular death; their relative safety was also assessed. The population studied comprised subgroups of patients with atherosclerotic vascular disease manifested as either recent ischaemic stroke, recent myocardial infarction, or symptomatic peripheral arterial disease. Patients were followed for 1 to 3 years. FINDINGS: 19,185 patients, with more than 6300 in each of the clinical subgroups, were recruited over 3 years, with a mean follow-up of 1.91 years. There were 1960 first events included in the outcome cluster on which an intention-to-treat analysis showed that patients treated with clopidogrel had an annual 5.32% risk of ischaemic stroke, myocardial infarction, or vascular death compared with 5.83% with aspirin. These rates reflect a statistically significant (p = 0.043) relative-risk reduction of 8.7% in favour of clopidogrel (95% Cl 0.3-16.5). Corresponding on-treatment analysis yielded a relative-risk reduction of 9.4%. There were no major differences in terms of safety. Reported adverse experiences in the clopidogrel and aspirin groups judged to be severe included rash (0.26% vs 0.10%), diarrhoea (0.23% vs 0.11%), upper gastrointestinal discomfort (0.97% vs 1.22%), intracranial haemorrhage (0.33% vs 0.47%), and gastrointestinal haemorrhage (0.52% vs 0.72%), respectively. There were ten (0.10%) patients in the clopidogrel group with significant reductions in neutrophils (< 1.2 x 10(9)/L) and 16 (0.17%) in the aspirin group. INTERPRETATION: Long-term administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischaemic stroke, myocardial infarction, or vascular death. The overall safety profile of clopidogrel is at least as good as that of medium-dose aspirin

A highly virulent variant of HIV-1 circulating in the Netherlands.

We discovered a highly virulent variant of subtype-B HIV-1 in the Netherlands. One hundred nine individuals with this variant had a 0.54 to 0.74 log &lt;sub&gt;10&lt;/sub&gt; increase (i.e., a ~3.5-fold to 5.5-fold increase) in viral load compared with, and exhibited CD4 cell decline twice as fast as, 6604 individuals with other subtype-B strains. Without treatment, advanced HIV-CD4 cell counts below 350 cells per cubic millimeter, with long-term clinical consequences-is expected to be reached, on average, 9 months after diagnosis for individuals in their thirties with this variant. Age, sex, suspected mode of transmission, and place of birth for the aforementioned 109 individuals were typical for HIV-positive people in the Netherlands, which suggests that the increased virulence is attributable to the viral strain. Genetic sequence analysis suggests that this variant arose in the 1990s from de novo mutation, not recombination, with increased transmissibility and an unfamiliar molecular mechanism of virulence