17 research outputs found
Thermométrie Raman rotationnelle pour la caractérisation du flux d'air au sein d'un banc d'essai turbomachine
International audienceNon-invasive and accurate measurements are essential to study the reactive flows in aeronautical engines. This paper reports the results of a unique measurement campaign providing the temperature flowfield in a large scale facility turbomachine test rig using spontaneous rotational Raman scattering technique. Different planes of interest and operating conditions are probed, showing good agreement with thermocouple measurements. Fast temperature variations (>7.7 kHz) could be probed thanks to synchronization of the laser pulse with the rotor clock. Results outline the performance of in situ Raman technique to investigate steady and unsteady flows in turbine's conditions
Thermométrie par diffusion Raman anti-Stokes Cohérente hybride femto/picoseconde dans les écoulements réactifs.
International audienceNous prĂ©sentons dans cet article le potentiel applicatif du banc de spectroscopie DRASC ro-vibrationelle de lâONERA en rĂ©gime hybride femtoseconde/picoseconde dĂ©veloppĂ© pour la thermomĂ©trie dans les Ă©coulements rĂ©actifs. Lâinvestigation dâune flamme CH4/air ( 2000 K) a Ă©tĂ© rĂ©alisĂ©e avec ce dispositif par des sĂ©ries de mesures en tir unique, moyennĂ©es et Ă diffĂ©rentes hauteurs dans la flamme. Ces rĂ©sultats ont Ă©tĂ© utilisĂ©s pour Ă©valuer la prĂ©cision de la mesure obtenue avec le dispositif hybride. Une Ă©tude montre Ă©galement comment lâajustement des paramĂštres de sonde, de retard temporel et de la polarisation, permet dâoptimiser la mesure en augmentant la plage de tempĂ©ratures mesurables en tir unique, et en rejetant efficacement les contributions non-rĂ©sonantes. Finalement, nous dĂ©montrons que notre montage permet de dĂ©tecter la contribution dâespĂšces minoritaires en exploitant lâeffet dâamplification opĂ©rĂ© sur le signal lorsque les faisceaux excitateurs sont placĂ©s sur une rĂ©sonance Ă©lectronique des molĂ©cule
Thermométrie Raman spontanée pour la caractérisation de l'écoulement d'air dans une turbomachine.
International audienceUn systĂšme de spectroscopie rotationnelle par diffusion Raman spontanĂ©e a Ă©tĂ© dĂ©veloppĂ© et utilisĂ© pour mesurer le champ de tempĂ©rature sur un banc dâessai turbo-machine en diffĂ©rents plans dâintĂ©rĂȘt de lâĂ©coulement et pour plusieurs points de fonctionnement. Les cartographies du champ de tempĂ©rature obtenues en Raman ont Ă©tĂ© comparĂ©es aux mesures effectuĂ©es Ă lâaide dâune sonde 5 trous. Cette campagne dĂ©montre les performances de la technique Raman spontanĂ©e pour la caractĂ©risation dâun Ă©coulement stationnaire et instationnaire dans des conditions expĂ©rimentales synchronisĂ©es sur le rotor
CD36 Deficiency Leads to Choroidal Involution via COX2 Down-Regulation in Rodents
Florian Sennelaub and colleagues show that CD36 deficiency leads to choroidal involution, a key feature of "dry" age-related macular degeneration, via COX-2 down-regulation in the retinal pigment epithelium
Thermométrie par diffusion Raman anti-Stokes Cohérente hybride femto/picoseconde dans les écoulements réactifs.
International audienceNous prĂ©sentons dans cet article le potentiel applicatif du banc de spectroscopie DRASC ro-vibrationelle de lâONERA en rĂ©gime hybride femtoseconde/picoseconde dĂ©veloppĂ© pour la thermomĂ©trie dans les Ă©coulements rĂ©actifs. Lâinvestigation dâune flamme CH4/air ( 2000 K) a Ă©tĂ© rĂ©alisĂ©e avec ce dispositif par des sĂ©ries de mesures en tir unique, moyennĂ©es et Ă diffĂ©rentes hauteurs dans la flamme. Ces rĂ©sultats ont Ă©tĂ© utilisĂ©s pour Ă©valuer la prĂ©cision de la mesure obtenue avec le dispositif hybride. Une Ă©tude montre Ă©galement comment lâajustement des paramĂštres de sonde, de retard temporel et de la polarisation, permet dâoptimiser la mesure en augmentant la plage de tempĂ©ratures mesurables en tir unique, et en rejetant efficacement les contributions non-rĂ©sonantes. Finalement, nous dĂ©montrons que notre montage permet de dĂ©tecter la contribution dâespĂšces minoritaires en exploitant lâeffet dâamplification opĂ©rĂ© sur le signal lorsque les faisceaux excitateurs sont placĂ©s sur une rĂ©sonance Ă©lectronique des molĂ©cule
Subcellular distribution of receptor sites in human brain: differentiation between heavy and light structures of high and low density.
Studies of the subcellular localization of neuroreceptors in the rat brain have shown that most of them are associated with light and low density subcellular fractions. In two human brain areas, quite different subcellular distributions were observed. After fractionation by differential centrifugation of frontal cortex homogenates, benzodiazepine and serotonin 5-HT2 receptors were mainly found in the heavy mitochondrial (M) fraction, whereas mu-opiate and muscarinic cholinergic receptors were mainly concentrated in the microsomal (P) fraction. In human putamen, the presynaptic markers of dopaminergic nerve terminals (neurotensin receptors, dopamine uptake sites and amine vesicular transporter-binding sites), benzodiazepine receptors and serotonin uptake sites were recovered both in the high and low density fractions, whereas the muscarinic, opiate and, to a lesser extent, dopamine D2 receptors were mostly concentrated in the microsomal fraction. In the cerebral cortex, after isopycnic centrifugation in sucrose gradients, neuroreceptors were found in the high density fractions where the peaks of cytochrome oxidase and that of nerve endings, as identified by amine uptake and by means of electron microscopy were also found. A single peak of benzodiazepine receptors was observed in high density (1.15-1.17 g/ml) fractions suggesting that these receptors are much more concentrated in the nerve terminals or dendrites rather than in the dendritic spines or vesicles. The fact that muscarinic and opiate receptors were recovered in the P fraction with plasma membrane constituents and also in M and L fractions, which is confirmed by a bimodal distribution in sucrose gradient, suggests that they are localized in both the nerve terminals or dendrites and in the small vesicles or dendritic spines. In the putamen, much of the specific binding to uptake sites for dopamine and serotonin was recovered in the high density fractions, but the existence of another peak at a lower density indicates the presence of microsomal uptake sites. The results indicate that differential and isopycnic fractionation methods performed on human brain samples, make it possible to separate tissue fractions enriched in nerve endings, dendrites, dendritic spines, plasma membranes or vesicles