DC Breakdown Voltage of Carbon Dioxide Medium under Needle to Plane Electrode

This paper reports the experimental results on thecorona onset voltage and breakdown voltage by positiveand negative dc discharges in carbon dioxide mediumwithin the pressure range of 0.1 to 15MPa under theneedle to plane electrode. From the experimental resultsof dc discharge, negative corona discharges are observedmore clearly in liquid and supercritical phase than in gasphase of carbon dioxide. However, in our experimentalcondition, positive corona discharge was not found for dcdischarges. The breakdown mechanism in liquid can beclassified into two categories on account of the bubbletriggeredformation

Release of Shiga toxin by membrane vesicles in Shigella dysenteriae serotype 1 strains and in vitro effects of antimicrobials on toxin production and release

Effects of various antimicrobials on in vitro Shiga toxin production and release by Shigella dysenteriae serotype 1 was investigated in this study with particular reference to the role of outer membrane vesicles in toxin release by the organism. Five antimicrobials, namely nalidixic acid, ciprofloxacin, norfloxacin, fosfomycin and mitomycin C, were chosen for the study and the toxin titre was measured by the reverse passive latex agglutination (RPLA) method using an available kit. Only mitomycin C was found to induce production of Shiga toxin in the bacteria and its release by outer membrane vesicles. The highest titre of toxin was obtained in vesicle fraction suggesting that the vesicles play an important role in the release of Shiga toxin from periplasmic space by the organism

Pulsed and DC discharges in supercritical carbon dioxide

This paper reports the experimental results on thebreakdown voltage and phenomena in carbon dioxidemedium at 298, 304 and 373 K and within the pressurerange of 0.1 to 12.0/20.0 MPa under the point-to-planeelectrode using negative dc and pulsed discharge. Fromthe experimental results of negative dc discharge, coronadischarges with preceding as well as complete breakdownare observed more clearly in liquid and in supercriticalphase than in gas phase of carbon dioxide. The calculatedelectric field intensity on the tip of point electrode at thecorona onset voltage is about 450 MV/m; it suggests thatcorona is triggered by the field emission of electron. Thebreakdown mechanism of liquid phase can be classifiedinto two categories in comparison with critical pressure ofmedium. On the other hand, in the experimental result ofpulse electric discharge, the time delay of pulse formingand the relevance of the medium density were found