VST - VLT Survey Telescope Integration Status

The VLT Survey Telescope (VST) is a 2.6m aperture, wide field, UV to I facility, to be installed at the European Southern Observatory (ESO) on the Cerro Paranal Chile. VST was primarily intended to complement the observing capabilities of VLT with wide-angle imaging for detecting and pre-characterising sources for further observations with the VLT.Comment: 2 pages, 2 figures, conferenc

Milestones in the discovery of Budd-Chiari syndrome

In 1845, George Budd published a brief report regarding three patients who developed an obstruction of the hepatic veins. The condition has never been reported before, and was related to sepsis and alcoholism. Fifty-three years later, Hans Chiari postulated that syphilis was causing the obstruction of the hepatic veins, and enriched the debate with clinical and pathological correlations. Following the hypothesis on the ‘phlebitis obliterans’, several authors proposed other pathophysiological explanations including congenital causes, chronic trauma and exogenous toxins. RG Parker, in 1959, first recognized the relationship between obstruction of hepatic veins and thrombophilic conditions such as polycythaemia vera, pregnancy and hormonal therapy. Based on that, anticoagulant treatment was attempted, but with unsatisfactory outcome. We need to wait until the mid 1980s to see a widespread adoption of anticoagulants, with a consequent improvement of patients' survival. The fear of haemorrhagic events in patients with liver disease discouraged this therapeutic approach, and other surgical interventions (mainly port-systemic shunts) were conceived, but with high morbidity and mortality. The first liver transplantation in 1976 and the first trans-jugular intra-hepatic porto-systemic shunt in 1993 represented two major cornerstones in the management of Budd-Chiari syndrome (BCS). Such progresses allowed modifying the treatment of BCS until the modern concept of stepwise therapy. The present review thoroughly reviews the major landmarks in the discovery, treatment and clinical management of patients with BCS

Hydrodynamic cavitation in microsystems. II. Simulations and optical observations

International audienceNumerical calculations in the single liquid phase and optical observations in the two-phase cavitating flow regime have been performed on microdiaphragms and microventuris fed with deionized water. Simulations have confirmed the influence of the shape of the shrinkage upon the contraction of the jet, and so on the localisation of possible cavitating area downstream. Observations of cavitating flow patterns through hybrid silicon-pyrex microdevices have been performed either via a laser excitation with a pulse duration of 6 ns, or with the help of a high-speed camera. Recorded snapshots and movies are presented. Concerning microdiaphragms, it is confirmed that very high shear rates downstream the diaphragms are the cause of bubbly flows. Concerning microventuris, a gaseous cavity forms on a boundary downstream the throat. As a consequence of a microsystem instability, the cavity displays a high frequency pulsation. Low values Strouhal numbers are associated to such a sheet cavitation. Moreover, when the intensity of the cavitating flow is reduced, there is a mismatch between the frequency of the pulsation of the cavity and the frequency of shedded clouds downstream the channel. That may be the consequence of viscous effects limiting the impingement of a re-entrant liquid jet on the attached cavity

Cavitation Induced Damage: FEM Inverse Modeling of the Flow Aggressiveness

International audienc

Hydrodynamic cavitation in microsystems. I. Experiments with deionized water and nanofluids

International audienceAn experimental study of hydrodynamic cavitation downstream microdiaphragms and microventuris is presented. Deionized water and nanofluids have been characterized within silicon-Pyrex micromachined devices with hydraulic diameters ranging from 51 μm to 104 μm. The input pressure could reach up to 10 bars, and the flow rate was below 1 liter per hour. The output pressure of the devices was fixed at values ranging from 0.3 bar to 2 bars, so that it was possible to study the evolution of the cavitation number as a function of the Reynolds number in the orifice of the diaphragms or in the throat of the venturis. A delay on the onset of cavitation has been recorded for all the devices when they are fed with deionized water, because of the metastability of the liquid and because of the lack of roughness of the walls. For the first time, hydrodynamic cavitation of nanofluids (nanoparticles dispersed into the liquid) has been considered. The presence of nano-aggregates in the liquid does not exhibit any noticeable effect on the cavitation threshold through the venturis. However, such a presence has a strong influence on the cavitation onset in microdiaphragms: above a critical volume solid concentration of ≈10−5, the metastability is broken and the nanofluids behave as tap water filled up with large nuclei. These microdevices, where a low amount of fluid is required to reach cavitating flows, appear to be useful tools in order to study cavitating phenomena in localized area with specific fluids

Cavitation in microchannels

International audienc

Il mutismo cerebellare transitorio: tre casi e revisione della letteratura

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