Propagation et génération des streamers dans les diélectriques liquides

This study concerns the initiation and propagation of streamers in point-plane geometry. Our experimental set-up has permitted us to show the existence of a close correlation between the shape of the streamer, its propagation velocity, the current shape and the light it emits, whatever are the polarity of the point and the liquid nature. The more filamentary the streamer, the higher its velocity. The propagation velocity has a minimum for a large variety of insulating liquids wheter pure or containing different additives. The amplitude of the velocity depends strongly on the electronic properties of the liquid and additives. The effects of hydrostatic pressure on the streamer appearance for both polarities suggest the existence of a gas phase. It appears that electrohydrodynamically induced cavitation phenomena, resulting from unipolar charge injection, are not responsible for the gas phase.Cette étude concerne la génération et la propagation des streamers en géométrie pointe-plan sous créneau de tension. Un nouveau dispositif expérimental a permis de montrer qu'il existe une relation étroite entre la forme du streamer, sa vitesse de propagation, la forme du courant et la lumière qu'il émet qu'elles que soient la polarité de la pointe et la nature du liquide. Plus le streamer est filamentaire, plus il est rapide et réciproquement. La distribution de vitesse admet un minimum pour un très grand nombre de liquides isolants pur ou renfermant divers additifs. L'amplitude des vitesses dépend d'une manière importante des propriétés électroniques du liquide et des additifs. L'effet de la pression hydrostatique sur l'apparition des streamers dans les deux polarités, indique l'existence d'une phase gazeuse. Il semble que le mécanisme de cavitation induite par des mouvements électrohydrodynamiques résultant d'une injection unipolaire de charges ne soit pas à l'origine de cette phase gazeuse

Determination of the Prime Electrostatic Endothelial Cell Transplantation Procedure for e-PTFE Vascular Prostheses

The purpose of this study was to evaluate the extent of cellular adhesion (density and morphological maturation), cellular membrane damage, and cellular viability after an electrostatic transplantation of human umbilical vein endothelial cells (HUVECs) onto 6-cm segments of 4-mm I.D. e-PTFE (GORE-TEX®) vascular prostheses using a prototype electrostatic endothelial cell transplantation device (EECTD). The electrostatic transplantation parameters evaluated were the apparatus-applied voltage and transplantation time. By our definition, the combination of applied voltage and transplantation time that met the a priori criteria of: 1) maximum transplanted cellular viability, 2) maximum transplantation density, 3) maximum morphological maturation (degree of cellular flattening), and 4) minimal cellular membrane damage would be the prime transplantation procedure. The results of the experimentation indicated that the prime conditions for HUVEC transplantation were obtained when +1.0 V was applied for a transplantation time of 16 min. These conditions achieved an average viable graft surface coverage of 97.4 ± 1.6% with an average transplantation density of 73,540 ± 8,514 HUVECs/cm2. Furthermore, the transplanted HUVECs were morphologically mature (flattened) with minimal apparent cellular membrane damage (lysis or pitting). The overall clinical significance of this study is that viable endothelial cell transplantation to synthetic vascular grafts can be accomplished at high cellular densities and morphological maturation in 16 min using the EECTD. With the promising in vitro transplantation results, the next logical investigations will include additional in vitro evaluations (cellular retention upon shear stress exposure and biochemical assays) followed by in vivo evaluations to examine thromboresistance and influence on intimal/anastomotic hyperplasia