1,721,072 research outputs found
La présence humaine aux Escoyères dans l’Antiquité : quelques observations sur l’inscription de la chapelle de Sainte Marie-Madeleine
No full textLa fréquentation du Queyras dans les temps anciens doit remonter au moins à l’Âge des Métaux, et ceci en raison de l’existence de la mine de cuivre de Saint-Véran, au lieu-dit Clausis, laquelle, selon les plus récentes datations au radiocarbone, a été exploitée à partir de 2 300-2 000 ans avant J.-C. (fin Néolithique-Bronze Ancien). À part la mine de Saint-Véran, nous avons de rares émoignages d’une présence humaine de l’Âge des Métaux. On ne peut signaler que de sporadiques trouvailles d’objets en bronze (y compris le mobilier d’une sépulture au Musée de Gap) faites à Saint-Véran au xixe siècle. Néanmoins ce matériel assez tardif a été daté surtout du Bronze Final-Âge du Fer (environ viie siècle avant J.-C.), alors qu’une autre trouvaille citée par Tivollier, celle de La Monta (commune de Ristolas) en 1834, demeure douteuse, le mobilier ayant disparu. Il faut arriver aux temps de l’Empire romain pour avoir d’autres témoignages de la présence humaine dans le Queyras, à savoir les deux inscriptions de Sainte Marie-Madeleine aux Escoyères et d’Aiguilles (cette dernière étant conservée au Musée de Gap), de sépultures à incinération, quelques pièces de monnaie, etc. Il faut dire que, à part les recherches faites à la mine de cuivre, aucune campagne archéologique n’a été menée dans le Queyras, et le peu de matériel dont nous disposons n’arrive que de trouvailles fortuites, et le plus souvent mal documentées. Pour ce qui regarde le plateau des Escoyères, localité qui, longtemps, a dû être un important lieu de passage entre le bassin de Guillestre et la plaine du Piémont, on dispose de témoignages (petits objets en bronze) qui attestent d’une présence humaine au moins à partir du premier Âge du Fer ou, de toute façon, contemporaine de la civilisation de «Guillestre-Peyre Haute». Puis la présence des Romains a dû devenir importante vers le ier siècle avant J.-C. Un victoriatus en bon alliage d’argent et en bon état de conservation (diamètre 15 mm) nous semble le plus ancien témoignage de la présence romaine aux Escoyères. Mais, l’importance des Escoyères comme carrefour ou passage obligé de la voirie antique est attesté surtout par la célèbre inscription de SainteMarie-Madeleine (C.I.L. XII, 0080). La dalle des Escoyères a été signalée au monde académique vers les années 1870 et répertoriée par le C.I.L. en 1888. Les savants de l'époque se sont vite aperçus que les deux fragments pouvaient être accolés. L’inscription, à partir d’un calque, a fait récemment l’objet (A. Roth Congès, 1994) d’une étude soignée. Dans mon article je présente quelques observations directes qui se rapportent à la lecture de Roth Congès et aux explications qu’elle a données
Comparison between PIV measurements with high-speed and cross-correlation cameras in a jet
No full textIn this paper, a comparison between two particle image velocimetry (PIV) systems, one based on a standard cross-correlation charge coupled device (CCD) camera with pulsed laser and another using high-speed complementary metal oxide semiconductor (CMOS) camera with continuous laser is performed. The objective of the paper is to point out advantages and disadvantages of the two systems when computing large and small flow scale statistics. The comparison is performed on velocity measurements in the near and far fields of a circular water jet: on this flow several experimental data and empirical selfsimilarity laws are available for comparisons. The results show that both systems are suitable for measurements with a preference for the standard one when investigating smallscale statistics. This result depends on the lower number of effectively independent samples acquired by a high-speed system and on the higher noise levels of CMOS sensors in comparison to CCDs
Comparison between PIV measurements from high-speed (CMOS) and cross-correlation (CCD) systems in a jet flow
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Passive scalar mixing in a turbulent jet
No full textThe present work investigates passive scalar turbulent mixing by means of experimental optical techniques capable to simultaneously measure the instantaneous velocity and scalar fields in a non-intrusive way. In particular, passive scalar mixing of a water jet ejected from a pipe duct onto the surrounding quiescent pure fluid is studied by simultaneously using Particle Image Velocimetry for the velocity field and Planar-Laser Induced Fluorescence for the scalar field. The Reynolds numbers (Re) of the jet flow, based on the jet diameter and exit maximum velocity, is 23700 so a fully turbulent jet emerges from the pipe allowing investigating the mixing mechanisms driven by velocity fluctuations. In order to avoid diffusion to be important compared to advection, a scalar substance, Fluorescein sodium salt, with a Schmidt number equal to 2050 has been employed. This ensures turbulent transport to be investigated focussing on Reynolds fluxes, , whose measure is the main aim of this work. A detailed and accurate description of these quantities is given, unveiling some new interesting features in the pipe jet near field, 0<x/D<17, where few experimental data are available for the scalar concentration field. At the end of the investigated region, the present data approach the Literature data for the self-similar region. © 2009 TSFP4 Symposium. All Rights Reserved
Experimental study on vortex rings dynamics in a pulsed jet using Particle Image Velocimetry
No full textIn this work, an experimental study on vortex rings dynamics has been performed using digital particle image velocimetry (PIV); in particular, vortex rings at the exit of a circular orifice in a pulsed jet configuration are investigated. The relevance of such a study is related both to the fundamental fluid-mechanics involved in the generation, growing and evolution of vortex rings and simultaneously to the practical applications of the pulsed jet configuration; in particular attention is given to the pulsed jet condition which appears at the outlet of prosthetic heart valves. Different input signals and different stroke volumes have been studied obtaining great differences in the fluid dynamic fields, in particular in the number and in the dynamics of the generated vortices; Reynolds and viscous stresses calculations have been performed. For this particular experimental set-up, results show a great dependency from the input signal imposed at the piston by the linear motor used, both in the waveform, and in stroke volume
Evaluation of carnitine, acetylcarnitine and isovalerylcarnitine on immune function and apoptosis
No full textThe pool of different carnitine derivatives is formed by carnitine, acetylcarnitine, propionylcarnitine and isovalerylcarnitine. Isovalerylcarnitine is a compound performing activities that differ from those of the other carnitine esters. Its activity on proteolytic enzymes and on the calpain system has been demonstrated in the past. Both the calpain and the caspase systems belong to the protease family and lead to cytochrome activation and apoptosis. The two systems can interact to promote apoptosis. In view of this proapoptotic activity of isovalerylcarnitine, studies were carried out to ascertain whether this carnitine derivative influences cell-reaction processes associated with apoptosis. U937 leukemic cells were selected for these studies because they are a well-established model for the assessment of cellular immune responses. In addition to nuclear morphologic alterations produced by apoptosis that can be detected by specific histochemical and microscopic methods, we also took other cell functions into consideration, such as phagocytosis, cell killing and cell growth, which are indices of immune function related to apoptosis. Unlike reference carnitine forms, isovalerylcarnitine produced an early and marked increase in phagocytosis and also an increase in cell killing. Cell proliferation was reduced. The hypothesis is set forth that isovalerylcarnitine may be a caspase-activating, proapoptotic factor that resembles various anticancer agents, which induce early apoptosis that coincides with early activation of caspase. This hypothesis is supported by the ability of isovalerylcarnitine to induce early phagocytosis and cell killing
Investigation on vortex dynamics downstream moving leaflets by means of Robust Image Velocimetry
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