Experimental parametric study of energy dissipater design in natural rivers

Water retention in river plains is a common measure for flood routing. Discharge control is easily achieved by structures combining openings and weirs. Energy dissipation at the outlet is required to ensure the transition from supercritical to subcritical flow and to protect the downstream reach from scouring and erosion. Experimental investigations were carried out in a hydraulic flume at the Laboratory for Applied Hydraulics of hepia-Geneva with various patterns of alternate blocks on the ground sheet downstream of an adjustable sluice gate. The most relevant geometrical parameters of sharp edged blocks, width, height, longitudinal and lateral spacing and also the upstream and downstream flow conditions were systematically investigated. The main goal of the first order research was to provide a new easy-to-use formula for river engineers to estimate energy dissipation achieved by alternate immersed blocks downstream of an outlet and thus to design the most relevant arrangement of the blocks

Selective melanocortin MC4 receptor agonists reverse haemorrhagic shock and prevent multiple organ damage

Background and purpose: In circulatory shock, melanocortins have life-saving effects likely to be mediated by MC4 receptors. To gain direct insight into the role of melanocortin MC4 receptors in haemorrhagic shock, we investigated the effects of two novel selective MC4 receptor agonists. Experimental approach: Severe haemorrhagic shock was produced in rats under general anaesthesia. Rats were then treated with either the non-selective agonist [Nle(4), D-Phe(7)]alpha-melanocyte-stimulating hormone (NDP-alpha-MSH) or with the selective MC4 agonists RO27-3225 and PG-931. Cardiovascular and respiratory functions were continuously monitored for 2 h; survival rate was recorded up to 24 h. Free radicals in blood were measured using electron spin resonance spectrometry; tissue damage was evaluated histologically 25 min or 24 h after treatment. Key results: All shocked rats treated with saline died within 30-35 min. Treatment with NDP-alpha-MSH, RO27-3225 and PG-931 produced a dose-dependent (13-108 nmol kg(-1) i.v.) restoration of cardiovascular and respiratory functions, and improved survival. The three melanocortin agonists also markedly reduced circulating free radicals relative to saline-treated shocked rats. All these effects were prevented by i.p. pretreatment with the selective MC4 receptor antagonist HS024. Moreover, treatment with RO27-3225 prevented morphological and immunocytochemical changes in heart, lung, liver, and kidney, at both early (25 min) and late (24 h) intervals. Conclusions and Implications: Stimulation of MC4 receptors reversed haemorrhagic shock, reduced multiple organ damage and improved survival. Our findings suggest that selective MC4 receptor agonists could have a protective role against multiple organ failure following circulatory shock