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The physical processes following the electrical breakdown of water between planar and hemispherical electrodes separated by a sub-millimeter gap have been studied using electrical and optical diagnostics. The expanding plasma column after breakdown generates first shockwaves and at a later stage a vapor bubble which expands for about 200 [micro]s and then decays with a time constant of 1 ms. The bubble decay time determines the dielectric recovery of the switch as has been shown with pulse-probe experiments. Index Terms--Water, electrical breakdown, pulsed power switching, shockwaves, dielectric recovery.

A one-dimensional formulation for the current density-electric field (J-E) characteristic for pure water has been developed which includes a self-consistent boundary condition, the auto-dissociation process, and electro-chemical kinetics at the electrodes. Our model results in a relatively simple form for the J-E characteristic. The predictions are shown to be in agreement with experimental data. The resulting J-E characteristics have an initial linear shape, followed by a super-linear increase. A saturating behavior is predicted based on the details of field-dependent variations in electro-chemical kinetic rates. Strong auto-dissociation would finally cause non-linear increases at much higher applied voltages. Based on the present theory, pertinent suggestions for improving the performance of water-based gaps for pulsed power applications have been made. These include water circulation, employing surface coatings, and optical/ laser excitation at the electrodes. Index Terms--Water breakdown, boundary effects, nonlinear conduction.

Background: In recent years, there has been an increasing number of cases of early gastric cancer (TI NX) with intramucosal invasion, which are untreatable by surgical or endoscopic mucosal resection [...]

By using a tungsten wire with 75-[micro]m diameter, 2 cm apart from a plane cathode, and applying a 600-ns, 120-kV square wave pulse, we were able to obtain a pulsed-water corona discharge (PWC). The effect of these discharges on bacteria was studied using water contaminated with Escherichia coli or Bacillus subtilis, the latter in both the vegetative and spore state. The strongest effect was obtained on E. coli. The concentration of E. coli could be reduced by three orders of magnitude after applying eight corona discharges to the water. The corresponding energy expenditure is 10 J/[cm.sup.3]. The decontamination rate had the largest values at the beginning, and decreased considerably after 15 electrical discharges, reaching a constant residual concentration value of [10.sup.-4] of the initial concentration. For B. subtilis in the vegetative state, it took almost 30 discharges to reach the same result, corresponding to an energy expenditure of 40 J/[cm.sup.3]. There was no effect on B. subtilis spores. Comparisons with the pulsed-electric field (PEF) method indicate that the decontamination efficiency of the PWC method is slightly higher than that of the PEF method. Index Terms--Bacterial decontamination, corona discharge, pulsed power, streamers, water.

The propagation features of a streamer discharge in water have been investigated. based on the experimental data obtained in the study of water discharges in a non-uniform electric field, the propagation of streamers is explained as the evaporation of water at the tip of the streamer and around it. The energy balance in the process of the streamer propagation is calculated for a sub-microsecond discharge in distilled water It is shown that the energy released in the prebreakdown process is sufficient to evaporate the liquid in the streamer channels. Similar velocity of the streamer propagation in both tap and distilled water substantiates negligible effect of ionic current density onto the streamer propagation process. These estimations based on the experiment have relevance to the discussion on the nature of the dielectric breakdown of water.

A study was conducted to characterize a mechanism that supports the destruction of heterogeneous solid dielectrics with high intrinsic inhomogeneity. Two types of heterogeneous natural rocks were utilized in the study, namely granite and tuff. The products of destruction were then determined by measuring the volume between the electrodes. Experimental results indicated that the mechanism effectively determined the nature of solids breakdown at low electric fields.

Augmentation of the magnetic field for electro-magnetic railguns is a quite effective method to suppress the ablation of bore materials since it allows to decrease the plasma armature current without a decrease of the Lorentz force for the acceleration. Another constructive effect of the augmentation on a plasma armature was observed in our experiment, that is to say, an external magnetic field for the augmentation compresses the plasma armature in the axial direction and suppresses the broadening of the plasma armature. In this paper, the behavior of plasma armature in the augmented railgun using a permanent magnet is investigated in comparison with that in the railgun without the augmentation.

Preacceleration of a projectile is quite important to reduce the erosion of the bore surface in a railgun. Gas guns, electrothermal guns and other railguns have been used to preaccelerate the projectile. Here, the new method using Plasma Initiation Separated from the Projectile (PISP method) is proposed, and its effectiveness is confirmed experimentally. A thin copper wire is placed near the edge of the railgun, which explodes and forms a plasma that has a fast flow velocity due to the Lorentz force. This fast flowing plasma collides with the projectile which obtains an initial velocity mainly by the momentum transfer. Since the current increases while only the plasma is accelerated, the driving force of the projectile just after the collision of the plasma with the projectile is large. In other words, the PISP method works as an inductive energy storage circuit with an opening switch.

Energy efficient generation of ozone is very important because ozone is being used increasingly in a wide range of industrial applications. Ozonizers usually use dielectric barrier discharges and employ alternating current (ac) with consequent heat generation, which necessitates cooling. In the present study, very short duration pulsed voltage is employed resulting in reduced heating of the gas and discharge reactor A comparison of ozone generation in dry air using a coaxial concentric electrode system with and without a solid dielectric layer is reported. Two types of dielectric layers were employed, ceramic and polyvinylchloride (PVC). The effects of peak pulsed voltage (12.5 to 62 kV), reactor length (0.1 to 1 m), pulse repetition rate (25 to 400 pulses per second, pps), gas flow rate (1.5 to 3.0 1/min) and variation of the pitch length of the spiral wire forming the central electrode (5 to 10 mm) on the concentration and production yield of ozone (g/kWh) are reported. A comparison is made between the performance of discharge reactors with (ceramic reactor Type IIC and PVC reactor Type IIP) and without (reactor Type I) a dielectric layer, using the same electrode gap separation (15 mm) and reactor lengths (0.157 and 1 m). High production yields of ozone in dry air of ~ 122, 52 and 60 g/kWh were obtained when using, respectively ceramic, PVC, and no dielectric layer, for a fixed pulse rate of 100 pps, 1.5 1/min flow rate and for a relatively short length of the reactor of 157 mm.

The production of ozone was investigated using a dielectric barrier discharge in oxygen, and employing short-duration pulsed power. The dependence of the ozone concentration (parts per million, ppm) and ozone production yield (g([O.sub.3])/kWh) on the peak pulsed voltage (17.5 to 57.9 kV) and the pulse repetition rate (25 to 400 pulses/s, pps) was investigated. In the present study, the following parameters were kept constant: a pressure of 1.01x[10.sup.5] Pa, a temperature of 26 [+ or -] 4 [degrees] C, a gas flow rate of 3.0 1/min and a gaseous gap length of 11 mm. A concentric coaxial cylindrical reactor was used. A spiral copper wire (1 mm in diameter) was wound on a polyvinylchloride (PVC) cylindrical configuration (26 mm in diameter) and placed centrally in a concentric coaxial electrode system with 4 mm thick PVC dielectric layer adjacent to a copper outer electrode of 58 mm in internal diameter. HV and current pulses were provided by a magnetic pulse compressor power source.

Experimental investigation of HV short pulsed streamer discharges in dry air-fed ozonizers under various operating conditions are reported. Ozone concentration, energy input and ozone production yield (efficiency) were measured at various voltages (14 to 37 kV), pulse repetition rates (25 to 400 pulses per second, pps), flow rates (1.5 to 3.0 l/min) and different gap spacings (10 to 20 mm) at a pressure of 1.01x[10.sup.5] Pa in dry air. A spiral copper wire (1 mm in diameter) made to a cylindrical configuration (18 to 38 mm in diameter) in a concentric coaxial electrode system of various dimensions was employed. A magnetic pulse compressor provided the HV and current pulses. Higher voltage and higher repetition rates yielded higher concentrations of ozone at a fixed air flow rate. The present investigation was extended to assess the performance of this pulsed ozone generator using dry air under desired conditions of high concentration and high yield of ozone for industrial applications.

SUMMARY: We discuss the death process of human cervical cancer cells HeLa S3 induced by two types of nonthermal intense electrical pulses of different durations and amplitudes, 120 ns‐long, 12.5 kV/cm and 5 ns‐long, 250 kV/cm. WST‐8 Caspase 3, ASK1 and BAX, were analyzed by using the antibody assay and flow cytometry. Apoptosis activity was evaluated by means of the TUNEL assay and flow cytometry. Also, Ca2+ dependence of the death process and the protein expression were explored by using the metal ion chelating agent, EDTA. Our experiments demonstrated that 5 ns and 120 ns pulses give quite different biological stresses leading to the different death process and the protein expressions. The cell death induced by 120 ns pulses are dependent on the presence of Ca2+ and accompanied by expression of proteins associated with apoptosis and stress response. Conversely, the protein expression induced by 5 ns pulses was independent of the presence of Ca2+, whereas the death was dependent on Ca2+. [ABSTRACT FROM AUTHOR]

SUMMARY This paper describes the pasteurization of liquid whole egg (LWE) using intense pulsed electric fields (PEF) combined with mild heat. Four kinds of liquids as solvents including carboxymethyl cellulose (CMC) solution, CMC solution with adding lipoproteins extracted from LWE (CMC+), LWE, and centrifuged LWE for reducing lipoproteins (LWE−) were compared for the effectiveness of the PEF pasteurization. The liquids including Enterobacter aerogenes (107 /mL) were subjected to a number of PEF with an amplitude of 30 kV/cm or 50 kV/cm. Pre- and post-PEF thermal treatments with a temperature below 55 °C were used to enhance the killing effect. Our experiments show that the bacteria logarithmic reduction ratio of the pasteurization using 30 kV/cm PEF for CMC, CMC+, LWE, and LWE− were 6.6, 2.4, 1.4, and 1.6, respectively, whereas the reduction ratios were all more than 6 when the increased field of 50 kV/cm. Only bacteria in CMC solution were effectively killed compared to other liquids, which include lipoproteins, more or less. Numerical analysis of the electric field indicates the presence of lipoproteins in the vicinity of bacteria lessens the bacterial membrane potential, which results in weakening the killing effect. [ABSTRACT FROM AUTHOR]