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The wavefront time T f of lightning impulse plays an important role in the detection of insulation defects in metal enclosed gas insulated switchgear (GIS). Usually, a rod-plane electrode system with different geometric parameters is adopted to simulate local field enhancements in GIS. But, for GIS, the defects may occur on the high-voltage electrode which can not be properly simulated by a rod-plane electrode. To research the influence of waveform parameters on actual defects in GIS, cylinder-plane, coaxial cylinder, and basin-type insulator with a conductive protrusion, were used in this study. A generating system of double-exponential impulses with wavefront times in the range of 0.08 to 15 μs and wave tail times of approximately 50 μs was used to simulate different impulse test waveforms based on a fully enclosed oil-immersed Marx generator. The results show that for the cylinder-plane gap with a protrusion, when the gap distance of the needle tip to the plane is constant, increasing the length of the needle decreases the 50% breakdown voltage. Comparing with the insulation characteristics of rod-plane gap, the U 50 %-T f curves of the cylinder-plane electrode with needle defects thereafter no longer show a U shape as the rod-plane electrode, but increase with an increase in the wavefront time. The difference can be explained by the shielding effect of the cylinder electrode on the defect, which changes the electric field distribution of the gap. The U 50 %-T f curves of GIS bus with different voltage levels and basin-type insulator with surface conductive defect also show the similar increase trend. For V-t characteristics of GIS bus with different voltage levels, we find that the higher the voltage level, the more obvious the trend of the V-t characteristic bathtub curve.

Lightning impulse (LI) test is an effective means to detect insulation defects in gas-insulated metal-enclosed switchgear (GIS) equipment. However, the LI test wavefront time Tf will exceed the standard value of 1.2 μs ± 30% for large test load capacitance. Whether extending the Tf will influence defect detection effectiveness should be a concern. In this study, a generating system of impulses with different wavefront parameters was established. The insulation characteristics of a coaxial cylinder structure with an SF6 gas gap with conductive protrusion in a bus under impulses with different wavefront parameters were studied. Experimental results show that the voltage–time curve of the gap shows a bathtub trend that has a flat part in the range of 1 μs to 5 μs. With a Tf increase, the 50% breakdown voltage increases. Whether extending the Tf will influence defect detection effectiveness is analyzed from the standpoint of the different meaning of the breakdown voltage in voltage-time curve and 50% breakdown voltage. The essence of detection effectiveness under impulse voltages with different wavefront parameters is a comparison of the probability of detecting the same insulation defect. Based on the discharge probability distribution, a new quantitative method to evaluate the insulation defect detection effectiveness of impulse voltages for GIS equipment is proposed. The method, based on the 90% discharge voltage value of an insulation defect under a standard LI, normalizes the discharge probability under different wavefront parameters.

The appearance of streamer discharge in the coaxial electrode was studied using nanosecond pulse power. It is important to investigate the characteristics of the streamer discharge in the coaxial electrode in order to improve the performance of the nitrogen oxide treatment. The dependence of the streamer discharge on the electric field strength at the inner electrode and the tail of the pulse was investigated by using the simulated electrode as a reactor. The number of streamers increased with the electric field strength on the inner-electrode surface by changing the charging voltage. On the other hand, under these experimental conditions, the number of streamers little changed by changing the diameter of the inner electrode. An experiment excluding tail of pulse, to suppress the occurrence of secondary streamers, was conducted. Only primary streamer discharges were generated and the developing length of the primary streamer was related to the electric field strength on the surface of the inner electrode. In the development of coaxial reactors for gas treatment using nanosecond pulsed power, the reactor electrode should be designed so as to utilize the primary streamer discharge. The selection of a thin inner electrode leads to the concentration of streamer discharges near the internal electrode, and the thin external electrode utilizes the streamer concentration.

The standard lightning impulse (LI), defined as a smooth full lightning impulse voltage having a front time of 1.2 μs and a time to half-value of 50 μs, obtained from field observation, has remained unchanged from IEC Ed. 1 in 1962 through to Ed. 3 in 2010. LI test plays an important role in the equipment design and insulation defects detection. In order to evaluate the reasonability of the standard LI waveform from the point of insulation characteristics, breakdown characteristics of GIS under LI with different wavefront times Tt and wavetail times Tt were studied. Those experimental results show that the LI waveform parameters have little influence on the breakdown characteristics of a sound GIS equipment, but have great influence on the GIS equipment with defects. For a highly inhomogeneous electric field, with the wavefront time increasing, the 50% breakdown voltages U50% have remarkable change and the U50%−Tt curve tends to be U-shaped. The 50% breakdown voltages decrease significantly with the increase of impulse wavetail time, especially when wavetail time is in the range of 1.5 to 15 μs, but the difference of the values decreases after 15 μs. Ignoring the generating possibility in the field for the large series inductance and load capacitance, a LI with wavefront time in the range of 0.2 to 0.7 μs is proposed in the field for it may increase the probability of detecting insulation defects. Finally, the polarity reversion phenomenon and critical radius phenomenon, observed from the breakdown characteristics, can be explained by the migration and diffusion of space charges.

The integrated stress response (ISR) is one of the most important cytoprotective mechanisms and is integrated by phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α). Four eIF2α kinases, heme-regulated inhibitor (HRI), double-stranded RNA-dependent protein kinase (PKR), PKR-like endoplasmic reticulum kinase (PERK), and general control nonderepressible 2 (GCN2), are activated in response to several stress conditions. We previously reported that nanosecond pulsed electric fields (nsPEFs) are a potential therapeutic tool for ISR activation. In this study, we examined which eIF2α kinase is activated by nsPEF treatment. To assess the responsible eIF2α kinase, we used previously established eIF2α kinase quadruple knockout (4KO) and single eIF2α kinase-rescued 4KO mouse embryonic fibroblast (MEF) cells. nsPEFs 70 ns in duration with 30 kV/cm electric fields caused eIF2α phosphorylation in wild-type (WT) MEF cells. On the other hand, nsPEF-induced eIF2α phosphorylation was completely abolished in 4KO MEF cells and was recovered by HRI overexpression. CM-H2DCFDA staining showed that nsPEFs generated reactive oxygen species (ROS), which activated HRI. nsPEF-induced eIF2α phosphorylation was blocked by treatment with the ROS scavenger N-acetyl-L-cysteine (NAC). Our results indicate that the eIF2α kinase HRI is responsible for nsPEF-induced ISR activation and is activated by nsPEF-generated ROS.

The application of pulsed power technology is spreading to biotechnology and medical fields. Pulse electric fields yield various influences on cells. Endoplasmic reticulum (ER) stress which is due to accumulation of unfolded proteins has been considered as one of disorder such as diabetes and Alzheimer. Unfolded protein response (UPR) is a built-in avoiding function of ER stress and conduct reactions as promotion and pausing of folding. The activation of UPR by application of nsPEFs on cells was studied. Here, proper conditions to activate UPR were explored in experiments. Eukaryotic translation initiation factor 2 subunit a (eIF2a) is phosphorylated and translation of protein is inhibited when cells are stressed. Transportations of protein before folding to ER are accordingly inhibited and the process is UPR. In this experiment, phosphorylated eIF2a (P-eIF2a) was observed to estimate the induction of UPR. Electric fields pulses of 14 ns and 70 ns in pulse width were applied on MEF and HeLa cells and expression of P-eIF2a was evaluated by Western blotting. First, relatively high electric fields pulses: over 120 kV/cm were applied. Second, under 70 kV/cm pulses were applied. Thapsigargin was used for positive control. The P-eIF2a expression of high electric field pulse applied samples was smaller than that of low electric field samples. The cell death and the P-eIF2a dephosphorylation was considered as the reason.

Ozone has been used an oxidation agent in various fields, and production of ozone with high efficiency and high concentration is required. In this study, ozone is produced in coaxial reactors using nanosecond pulsed power discharges. The ozone production with pulsed power discharges is efficient but relatively low-concentrated. In our previous studies, the ozone concentration increased with decrease of the diameter of the coaxial reactor. However, ozone concentration decreased in reversal by further decrease of the diameter of reactor. The surplus energy of applied pulse on the reactor is not consumed and causes long and large wave tail of applied voltage pulse. The wave tail can accelerate occurrence of spark discharges which are inefficient for discharge-chemical reaction. A control of the pulse wave tail on the reactor was investigated by using a winding resistor. Ozone concentration of 14-mm reactor became higher than 17-mm reactor. The effect of applied voltage between reactor electrodes was investigated by changing of charging voltage. Ozone concentration of 14-mm reactor was even or higher than 17-mm reactor. Additionally, the influence of mixed gas including nitrogen gas was investigated. Ozone concentration of 14-mm reactor increased with increase of nitrogen gas ratio from 0 % to 6%. Although spark discharge was prevented, ozone concentration was not sufficiently improved at all experiment.

In recently years, malignant neoplasm (cancer) occupies the extremely high percentage of cause of death, there are disadvantages to current cancer therapy. It has been confirmed nanosecond pulsed electric fields (nsPEFs) application induced apoptosis on cancer cells; many studies applying it to a cancer therapy have been started. We applied nsPEFs to mouse melanoma cells: B16-F10 in a cuvette. In addition, we combine nsPEFs application and anticancer drug (Adriamycin) administration, and cancer surviving fraction was measured by Crystal Violet Assay. The nsPEFs application or anticancer drug (Adriamycin) administration significantly decreased the cell surviving fraction. The cell survival fraction by combinational treatment of nsPEFs application and Adriamycin administration was significantly smaller than the unilateral treatment. Apoptosis ratio was higher in the combinational treatment. NsPEFs application might make nanoscale holes in the cell membrane, and the anticancer drug could work more effective.

Gas-insulated metal-enclosed switchgear (GIS) was developed in the mid-1960s [1]–[5]. Compared with traditional air-insulated switchgear, the GIS concentrates the bus, isolating switch, circuit breaker, lightning arrester, transformer, and many other devices in an enclosed grounding metal case. It has many advantages such as reliability, compactness, long maintenance cycle, and low environmental impact, which have led to it being widely used in electrical power systems [6]–[16]. However, increased operating voltages and more extensive power grids have given rise to increased GIS failure rates [17], [18].

NO and NO x decomposition in a coaxial reactor using nanosecond pulsed power were investigated. NO and NO x removal ratio decreased with the increasing treatment time. In the case of 50 pps, spark-discharge occurrence attracted the inner wire electrode to the outer electrode in the coaxial reactor. When the electrode separation in coaxial reactor became short, the spark discharges occurred more frequently in the center of reactor. Then, the volume of streamer discharges reduced. When an inner wire electrode was tensed by a spring was introduced in the coaxial reactor, the spark discharges were controlled and the narrowing of electrode separation was not observed. Accordingly, NO and NO x removal ratios did not decrease and became steady. The tensioned inner wire electrode worked out the potential of the coaxial reactor in using nanosecond pulsed powers.

The ozone production was studied using nanosecond pulsed-power systems and a coaxial reactor. Concentration of produced ozone decreased temporally when spark discharges were observed in the coaxial reactor due to curved inner wire electrode. At the same time, the reactor voltage fell down. In order to solve this problem, the tensioned inner wire electrode was adopted to be constant of electrode separation. As a result, the ozone concentration did not decrease and was kept as the peak concentration during pulse application. It was suggested that streamer discharges occurred stably due to restraining spark discharges caused by curve of inner wire electrode. Then, the ozone production efficiencies became constant on energy density because ozone concentrations increased proportionally with increasing energy density. Therefore, in order to obtain higher ozone concentration and stable ozone production, tensioned inner wire electrode of coaxial reactor was required.

The treatment of a surfactant aqueous solution, including nonylphenol ethoxylate NPE, which is one of the persistent pollutants, was investigated using nanosecond pulsed power system. The surfactant treatment using a nanosecond pulsed power system was compared with that using an external ozonizer. The surfactant was not sufficiently treated with the ozonizer. It was suggested that the water treatment using only ozone would decompose persistent pollutants insufficiently. Even when ozone concentration was the same in the water treatment reactor, more hydroxyl radical was produced by using pulsed discharges than an ozonizer. Therefore, the direct effects of discharges, such as ultraviolet rays and shockwaves, on the solution would contribute to the production of hydroxyl radical. The pH value and the electric conductivity of the solutions influenced the production amount of hydroxyl radical. For faster and stronger treatment, nanosecond pulsed power system, which generated more hydroxyl radical should be applied to the water treatment.

In the biological and medical fields, sterilization using pulsed electric fields or discharges and electroporation have been studied actively in recent years. It is clear that a pulsed electric field has some sort of effect on an organism. At present, however, it is not sufficiently clear what effect occurs and how the mechanism of a pulsed electric field acts on the organism. The effects of pulsed electric fields on ribonucleic acid RNA expression in biological cells were studied with the objective of elucidating the bioelectric mechanism. A pulsed electric field was applied to Vibrio parahaemolyticus, a pathogenic bacteria, and the expression of RNAs, specifically thermostable direct hemolysin TDH, VP1680, and VP1699, which represent pathogenic agents, were analyzed using the polymerase chain reaction PCR method. The level of expression of VP1680 increased when a pulsed electric field was applied, and the effect was at a peak when the electric field strength was 14i¾?kV/cm. The electric field strength barely affected the expression of TDH and VP1699. It was found that the effects of the electric field were different among the RNAs. The expression level varied with time when expression was analyzed. These results suggest the possibility of selective control of gene expression by using pulsed electric fields and possible new applications such as the development of functional foods.

Recently, improvements of drainage water treatment technology have been required. The streamer discharges generated by nanosecond pulsed power was applied to treat surfactant solution as a persistent chemical. Radicals with a high redox potential, as especially hydroxyl radical, is expected for degradative treatment of the persistent chemical. In using a coaxial cylindrical reactor, streamer discharges were generated in gas phase and progressed towards the liquid surface. Oxygen gas was used as a surrounding gas, and ozone was generated in gas phase. Treatment was carried out by a combined effect of direct action of streamer discharge on the water surface and ozone generated in the air. In comparison with a system using external ozonizer, an effect of streamer discharges was investigated. The voltage pulses of 1.5-ns pulse-width were applied on treatment of 1-L solution of purified water dissolved with 0.1 g of sodium dodecyl benzene sulfonate (DBS) as an anionic surfactant for 80 minutes. The concentration of anionic surfactant was evaluated with a methylene blue visual colorimetric method. The concentration of the surfactant decreased with treatment time in both systems. Treatment by pulsed power system decomposed the surfactant faster than treatment by external ozonizer system, especially for first 20 minutes of treatment. Dissolved ozone was confirmed from spectral absorbance change. The characteristic absorbance spectrum of DBS didn’t change with treatment by external ozonizer system but decreased with treatment by pulsed power system. It was suggested that the decomposition intermediates having a benzene ring was formed and could not be decomposed by ozone treatment alone. It was considered that ozone was decomposed by effect of streamer discharge, generation of radicals as hydroxyl radical was promoted, and a benzene ring of intermediates was opened.

Utilization of nanosecond pulsed electric fields (nsPEFs) has been widely studied as a novel approach to induce cellular stress for biological and medical applications. Endoplasmic reticulum (ER) stress has become to be considered as a cause of diseases as diabetes mellitus, Parkinson's disease, and so on. The objective of this study is to activate the ER stress response, which is a built-in function in cell to avoid ER stress, by applying pulsed high electric fields. Eventually, we aim to establish therapy and prevention methods for the diseases. Therefore, nsPEFs were applied on suspended solution of cultured cells to investigate adequate condition to activate stress response in this study. The nsPEFs of 14-ns and 70-ns pulse-width were applied on suspended solution of HeLa and MEF cells. It is well known that eIF2α phosphorylation is induced by various cellular stress, especially ER stress. Western blotting was used to analyze the nsPEFs-induced eIF2α phosphorylation. The cell viability after nsPEFs exposure was measured with WST-8 assay. It was confirmed that 14-ns and 70-ns pulses activated ER stress response. The 14-ns pulses activated a little response. The 70-ns pulses activated stress response as large as thapsigargin treatment. It was confirmed that 70-ns pulses could activate sufficiently large stress response even when most cells survived.

Ozone has been used for several applications as sterilization and deodorization because of the strong oxidizing power with low environmental load. The efficient and high-concentrated ozone-generation technology has been required. Ozone generation using nanosecond pulsed power has a feature of high efficiency but not high concentration. We have adopted a thin reactor in the ozone generation to improve the ozone concentration. The thin outer cylindrical electrode selectively utilizes high-density streamer discharges near the inner wire electrode in coaxial reactor. The dependence of the state of streamer discharges in the reactor on the generated ozone was discussed. On the basis of preliminary observation of streamer discharges in using a simulated electrodes as a reactor, the applied voltage waveform on reactor was controlled by introduction of a winding resistor connecting to the coaxial reactor. The ozone concentration increased with decreasing the diameter of the reactor. However, the ozone concentration was much lower than when the winding resistor was not connected. The reactor configuration might not match with the applied voltage waveform. Control of the applied voltage waveform and appropriate reactor configuration and system has to be considered.

Gas-insulated metal-enclosed switchgear (GIS) is an important switching equipment in modern power system. The lightning impulse (LI) test is particularly sensitive to abnormal field configurations and is recommended in IEC 62271-203 and GB 7674-2008 for voltage classes of 245 kV and above. Usually, the rod-plane electrodes system with different geometric parameters are adopted to simulate local field enhancement in GIS. But for GIS, the defects may occur in the high voltage bus. In this situation, it's not just the rod-plane electrode can be represented. In order to research the shielding effect of background electric field for GIS bus with a conductive protrusion under impulses, coaxial cylinder structure with conductive protrusion electrodes was used. Meanwhile, the classical rod-plane gap was also used to make a comparison. A generating system of double-exponential impulses with front times in the range of 0.08∼15 μs and wave tail times around 50 μs was established to simulate different impulse test waveforms based on a fully enclosed oil-immersed Marx generator. The results show that when the gap distance is fixed, with the length of the needle increase, the 50% breakdown voltage decreases. Discharge characteristics under different electrode configurations are compared. It is found that the shielding effect of the bus on the defect changes the electric field distribution of the gap. The U50%-Tf curves of the bus with needle defects thereafter no longer show the U-shaped as the rod-plane electrode, but increase with the increase of wavefront time.

Water pollution is a major environmental issue around the world. We have studied water treatment using nanosecond pulsed power. Discharge plasmas generated by the nanosecond pulsed power efficiently produce active species that are applicable to water treatments. In this study, device with a dielectric barrier was compared with that without a dielectric barrier. Indigo carmine solution was treated by two systems with nanosecond pulsed power. The treatment efficiency of the system with a dielectric barrier was lower than that without a dielectric barrier, although spark discharges were suppressed in the reactor. Considering the energy transfer ratio to discharges and the configuration of thinner reactor and smaller volume, the treatment efficiency using a dielectric barrier would not be low. According to absorbance at 288 nm, which is the specific absorbance wavelength of indigo carmine solution, the absorbance in using an oxygen working gas decreased faster than that using nitrogen.

Nowadays, water pollution is one of the environmental problems. We have studied a sewage treatment using nanosecond pulsed power discharges. The water treatment utilizes not only active species such as hydroxyl radical produced by electric discharges but also direct actions of discharges such as ultraviolet rays, shock wave and so on. In order to reduce the costs for treatment, treatment using air gas as a discharge gas was studied. The treatments using streamer discharges in simulated air gas, consisting of 20 % oxygen and 80 % nitrogen, and oxygen gas were evaluated. The surfactant treatment was assessed by the height of foam in the reservoir, which was one of the characteristics. The treatment by oxygen as discharge gas continued to reduce the height of foam in reservoir for 80 minutes treatment. On the other hand, the foam decreased rapidly for 0–20 minutes treatment. Under the presence of NO2, height of foam decreased rapidly because of increasing OH radical production. However, after 20 minutes, decrease of height of foam became slow because OH radical was consumed oxidizing NO2.

NOx treatment using streamer discharges generated by nanosecond pulsed powers was studied. The streamer discharges are generated in the reactor using nanosecond pulse power would treat NOx gas efficiently by plasma-chemical reactions. A tensioned inner wire electrode was introduced in the coaxial reactor by using a spring system. As a result, the temporal decrease in removal ratio was not observed and the removal ratio was righted. In order to obtain a more efficient removal treatment, adoption of thinner coaxial reactor was considered. Because streamer discharges distribute thickly around the inner wire electrode in the coaxial reactor driven by pulsed powers, the thinner coaxial reactor could utilize dense streamer discharges in the vicinity of the inner wire electrode. While the removal ratio was improved with decreasing the reactor diameter until 14 mm, the removal ratio decreased in using reactor of 10 mm. To discuss the phenomena, discharges in reactor were observed through an aperture on the outer electrode of an experimentally produced reactor. The appearance of discharges at downstream end of reactor in 10 mm reactor differed from 14 mm reactor. The removal ratio didn't increased in case of thinner inner wire electrode.

In recent years, treatment approach of malignant neoplasm (cancer), which has high death ratio, has been actively studied. There are several current cancer therapy as radiation therapy, surgical therapy, and chemotherapy (anticancer drugs), but these therapy have some disadvantages. The purpose of this study was to establish a new cancer therapy, using nanosecond pulsed electric fields (nsPEFs), with the less disadvantages. The pulse-application experiments were carried out with mouse melanoma cells: B16-F10. 2ns-PEFs and 14ns-PEFs were applied on cell suspension in an electroporation cuvette. The 2ns-PEFs-applied cancer cells surviving fraction in suspension measured with WST-1 assay was not different to that of controls. The surviving fraction of 14ns-PEFs-applied cancer cells was measured with WST-1 assay and crystal violet assay. The cancer cells surviving fraction decreased as the number of pulses increased in comparison with controls. In addition, 2ns-PEFs were applied on solid tumors obtained by embryonic chick assay. Although the weight of 15000-pulses-applied tumor was smaller than that of control, weight of 300-pulses-applied tumor was larger than control.

Gas-insulated metal-enclosed switchgear (GIS) is an important switching equipment in modern power system. Since GIS equipment has a fully enclosed structure, once failure occurs, it will always be followed by a huge economic loss and an adverse social impact. On-site lightning impulse (LI) test is very important to improve the quality of the GIS equipment since it is particularly sensitive to some fixed insulation defects formed in the transportation and installation process. The on-site LI waveform, restricted by the large load capacitance and impulse generator inherent inductance, has a long wavefront time T f compared with standard LI, called non-standard LI. The non-standard LI test has been carried out in the field. But its insulation defect detecting effectiveness is not clear. In this paper, a generating system of impulses with different waveform parameters, including double-exponential impulses with different wavefront times in the range of 0.08 ∼ 23.5 μs and an oscillating LI with wavefront time around 10 μs, was established. The insulation characteristics of SF 6 gas gap with highly inhomogeneous electric field under impulses with different waveform parameters were investigated. Experimental results showed that the insulation defects detecting effectiveness of oscillating LI with long T f around 10 μs is lower than that of standard LI. According to the voltage-time characteristic, it can be inferred that the T f plays an important role in the insulation defect detection. Prospective voltage is introduced to evaluate the insulation defects detecting effectiveness first. The insulation defect detecting effectiveness using the impulse test is reflected in the value of the prospective voltage. The prospective voltage-time characteristics confirm the conclusion that with the increase of impulse voltage T f , the detection effectiveness for GIS insulation is reduced. Consequently the standard or impulse LI test with T f < 1.56 μs is to be preferred for installation detection, because it offers a greater probability of detecting insulation defects.

The decolorization of the indigo carmine solution was performed by argon dielectric barrier discharge (DBD) excited on a target solution and the effect of the gap distance on the water treatment characteristics were investigated for the gap distance between 1.0 and 2.5 mm. The argon DBD was excited by the 3-kHz sinusoidal voltage with the fixed discharge power between 1.72 and 1.76 W for any gap distance. Voltage and current waveforms and Lissajous figures were acquired to investigate the electrical characteristics of the DBD. Compared with fixing the discharge energy, the higher decolorization rate was obtained with the shorter gap distance. Therefore, shortening gap distance could lead to increased decolorization efficiency of the indigo carmine solution. The mechanism of the higher efficiency with the shorter gap distance was discussed on the basis of the electrical characteristics and possible plasma chemical reactions in the argon DBD on the solution surface.

Many studies have tested the application of pulsed electric fields to tumors during cancer therapy. In this study, we used an embryonic chick assay to test the effects of nanosecond pulsed electric fields (nsPEFs) on a solid tumor. Our experiments used the embryonic chick assay, which is classified as in vivo experiment, because it has several advantages. Mouse breast adenocarcinoma cell line EMT6/KU was used to produce tumor cells for the experiment. The cells were inoculated for several days before the test and nsPEFs were applied using needle electrodes to solid tumors formed on the chorioallantoic membrane of eggs. A pulsed power generator with a pulse output length of 1.5 ns was used in this experiment. The tumors were dissected from the eggs after several days of nsPEF application and weighed. The mean weight of tumors treated with pulses was less than that of the control. The difference between the weight of the tumor after nsPEF application and that of the control was significant. The difference increased with the charging voltage of the pulsed power generator, with significant different observed when the charging voltage of the pulsed power generator was >2.85 kV. The mean tumor weight of the group that experienced discharges infrequently occurred on or under CAM was significantly smaller than that of the group that did not experience.

In ozone production using streamer discharges by pulsed power, the concentration of ozone is not high although ozone is produced with high efficiency. To improve ozone concentration, we studied the effects of electrode separation in a coaxial reactor using nanosecond pulsed power. We found that ozone concentration and yield increase with decreasing inside diameter of the outer electrode in the reactor. This occurs because dense plasma forms in a small-diameter reactor that has a small electrode separation. As the repetition rate of applied pulses was increased, the ozone yield remained nearly constant, while the ozone concentration increased proportionally. However, in a reactor having a small diameter of 17 mm, the tendency for the concentration to saturate and reductions in the ozone concentration were found to depend on pulse repetition rate. In such a small-diameter reactor, spark discharges occurred owing to the reduced separation of electrodes; these discharges cause the temperature of electrodes and gases to increase. Consequently, ozone molecules thermally dissociated and ozone concentration decreased. The occurrence of spark discharges was affected by not only the small separation of electrodes but also other factors. Potential of a small-diameter coaxial reactor for ozone production were presented and a control of occurrence of spark discharges was paramount.

The measurement of ozone concentration based on the visible photo absorption method is investigated. An LED having an emission peak at 609 nm and a photo diode sensitive at visible light frequencies are used as the light source and the photo detector, respectively. The transmittance is measured as a function of ozone concentration, which is in reasonable agreement with the Beer–Lambert relationship. The effective absorption cross-section can therefore be estimated from the fitting procedure. The concentrations determined by both the UV and visible photo absorptions agree well with each other in the range from 7.1 to 68.4 g/m3(N). The relative error in these concentrations is discussed on the basis of the Twyman–Lothian curve. The ozone measurement for the air-fed ozone generation is also investigated. The effect of photo absorption due to NOx species is unavoidable. The present results provide useful data if the ozone measurement based on the visible photo absorption method is applied to ozone monitoring ...

Development of the treatment technology of household effluent and industrial wastewater is imperative for environment conservation. In this study, a solution of persistent surfactant: nonylphenol ethoxylate was treated by using streamer discharges generated with nanosecond pulsed powers. The effects of configuration of water treatment system and of electric conductivity of the surfactant solution on the treatment were investigated. The conductivity was changed by amount of KCl (potassium chloride) added in the surfactant solution. Decolorization of indigo carmine solution with eight inner electrodes system was faster than one inner electrode system. In the treatment experiment, the dependence of the surfactant treatment on the conductivity was not definite. Because a chemical reaction would happen with potassium hydroxide and a surfactant, the effects of solution conductivity on treatment was studied for indigo carmine solution instead of surfactant solution. Decolorization of indigo carmine solution became slow as the conductivity increased. However, the difference of decolorization ratio of indigo carmine solution on conductivity was small. This result shows that this treatment method was hardly affected by the conductivity. Therefore, in practical treatment for drainage water, this method would be more effective than the treatment method using underwater discharges which is easily influenced by the solution conductivity.

Pulsed electric fields (PEFs) were applied on solid tumors obtained by embryonic chick assay. The mean weight of the pulse-treated tumors was significantly smaller than that of controls; tumor growth was constricted by nsPEFs application. The nsPEFs were applied to the tumor cell suspension to examine the effect of nsPEFs application in detail. The viability of tumor cells was measured by the WST-1 assay (water soluble tetrazolium salts) in advance. In increasing the charging voltage and the number of applied pulses, the viability of pulse-treated cells was significantly smaller than that of controls which were not exposed to nsPEFs. By using a flow cytometry with Apoptotic/Necrotic/Healthy Cells Detection Kit, it was confirmed that apoptosis was induced and necrosis slightly occurred in cell by nsPEFs application. In addition, it was confirmed that equal or more apoptosis in cells were induced by nsPEFs application than anisomycin application as a positive control. In other words, it was also confirmed that apoptosis was induced. In the same way, an ex vivo assay was performed on pulse-applied solid tumors obtained by embryonic chick assay. Apoptosis was induced and necrosis hardly occurred in ex vivo. It was also confirmed that the number of apoptosis induced cells by nsPEFs was equal or more than control as with in vitro. Therefore, application of nsPEFs is a potential measure of anti-tumor effect by apoptosis.

The NOx treatment using streamer discharges generated by nanosecond pulsed powers was studied. The streamer discharges were produced in the treatment reactor by adopting nanosecond pulsed powers. In the previous study, temporal decrease in NO removal ratio was observed as pulse repetition rate increased. This was because the inner wire electrode of coaxial treatment reactor curved during pulse application and spark discharges occurred between the electrodes. A tensioned inner wire electrode was introduced in the coaxial reactor by using a spring system. As a result, the temporal decrease in removal ratio was not observed and the removal ratio was righted. To utilize denser streamer discharges near the inner wire electrode, the diameter of external cylindrical electrode was made smaller. The thinning of reactor improved the NO removal ratio with the tensioned inner wire electrode. When the initial NO concentration was 100 ppm, the removal ratio reached up to approximately 100 %. However, the NO removal ratio decreased when the inner diameter of the external cylindrical electrode was decreased from 14 mm to 10 mm. This might be because spark discharges would occur in the reactor by excessively shortened electrode separation. In addition, the energy deposited in reactor might decrease with decrease of reactor volume.

Nanosecond pulsed power has been introduced to produce ozone efficiently and we attempted to increase concentration by adopting a thin coaxial reactor with a short electrode separation. However, temporal downturn of ozone concentration had been observed. This was because the inner wire electrode of coaxial reactor was curved and spark discharges frequently occurred around where the electrodes separation narrowed. Two approaches were employed to suppress this phenomenon. One was an adoption of tensioned inner wire electrode by a spring. The curvature of inner electrode was constrained and the downturn of ozone concentration was not observed. As a result, the concentration increased and steadily stayed. Another was an adoption of a thicker inner electrode, of which diameter was 1, 8, or 14 mm. Although the curvature of inner electrode was constrained, ozone concentration decreased. This would be because electric field strength on the electrode surface reduced occurrence of streamer discharges on the electrode surface. There was, however, a room of study because decreasing of ozone concentration was small in spite of the low electric field in using 8-mm electrode.

An excimer lamp constructed using a piezoelectric transformer (PT) has been developed and studied in our laboratory. The excimer lamp is based on the excitation of a dielectric barrier discharge (DBD) generated by a PT surface that induces a high voltage due to the piezoelectric effect. Spectroscopic measurement in the vacuum ultraviolet (VUV) region was performed for the excimer lamp filled with a He-Xe mixture and Ar. Emission spectra having a peak at 172 and 126 nm were found, which were respectively radiated from the and excimers returning to their ground states. A self-organization phenomenon (SOP) was also recognized in the He and Ar DBD. Static and time-resolved observations of the self-organized patterns were performed using single reflex and ICCD cameras, respectively. The formation of self-organized patterns in argon requires a small amount of air as an additive. In time-resolved observation, we found dark spots arrayed hexagonally in a weak emission on the PT surface, whose arrangement coincides well with that of bright hexagonal filaments. The dark spots are considered as the traces of accumulated charges on the dielectric electrode, which interrupt the hexagonally filamentary discharges. © 2012 Wiley Periodicals, Inc. Electron Comm Jpn, 95(10): 44–53, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10397

We found that the inclusion complexes composed of amylose and poly(glycolic acid-co-ɛ-caprolactone) (P(GA-co-CL)) of a biodegradable polyester were prepared by phosphorylase-catalyzed polymerization of α-D-glucose 1-phosphate from maltoheptaose as a primer in the presence of P(GA-co-CL) (vine-twining polymerization). In addition, it was found that lipase-catalyzed hydrolysis of P(GA-co-CL) in the inclusion complex was partly inhibited.

Nitrogen oxides (NOx) are one of the air pollutants that cause acid rain. Although utilization of catalysts is a typical established method of treatment to remove NOx, the catalyst is expensive so that the total cost of treatment is high. The efficient treatments using pulsed power, which utilize the pulse streamer discharges, have been studied. We have brought the nanosecond pulsed power to the NOx treatment. More efficient treatment is expected with the high electric fields with a nanosecond pulse width. In using the nanosecond pulsed power, the issue of design and modification of reactors configuration becomes important. Coaxial reactors consisting of wire-cylinder electrodes are adopted here and three types of electrical connecting methods between a generator and reactor chambers and gas tubing methods were investigated. The deposited energy density of 150 J/L yielded approximately 100% NO removal ratio for initial NO gas of 100 ppm. The three types of electrical connections were parallel, straight and serial. The parallel and straight connections yielded a higher removal ratio and efficiency in this experiment. Distribution of voltage in the reactors affects the removal ratio and efficiency since the production and development of streamer discharges depends of the amplitude of voltage. While propagating voltage pulses will decay in the reactors, reflections of voltage pulse at the open end of the reactors multiply the voltage distribution. Although impedance matching between the pulsed power generator and the reactors should be important, a multiplication of the transparent voltage pulse into the reactors by mismatching may improve the treatment.

Industrial application of pulsed power for water treatment has several advantages. Electrical discharges produced in atmosphere involve a variety of high energy phenomena which might be effective for water treatment. A water treatment system consisting of a coaxial cylinder reactor was constructed. The reactor consisted of a wire inner electrode and an outer cylinder electrode. A water layer was formed on the inner surface of the cylinder by water injection. By applying nanosecond pulse to the wire electrode, streamer discharges were developed from the wire to the water layer. Decolorization of indigo carmine solution was carried out by using the system. The indigo carmine solution was decolorized after treatment for 8 minutes with 50 pulses per second (pps) and then the decolorization efficiency at 80%-decolorization was determined to be about 5 mg/kJ. Increasing the pulse repetition rate shortened the treatment time but decreased the efficiency. The charging voltage of the storage capacitor of the pulse power generator influenced not only the decolorization time but also the efficiency of decolorization. When the charging voltage was 3.13 kV, the efficiency was 126.5 mg/kJ. Since ozone has a beneficial effect on decolorization, a sealed reactor confining the ozone enhances the effect of decolorization. The ozone produced by the same nanosecond pulsed power generator was injected into the Indigo carmine solution for comparison with the discharge reactor with water. The efficiency of decolorization using the discharge reactor was higher than that using ozone produced by the pulsed power.

A pulsed power generator with a nanosecond pulsewidth has been developed and applied to ozone production. Coaxial reactors connected in parallel are used in the experiment. The system ozone production yield, which is evaluated from the initial energy in the primary storage capacitors, is approximately 190 g/kWmiddoth when dry oxygen is used as the ingredient gas. A four-parallel chamber reactor gives higher concentrations of ozone and higher yields in the experimental conditions. This reactor seems to be most suitable to obtain the proper streamer corona volume and also to match the impedance of the generator. The connection between the generator and the reactor also affects the efficiency.

A review of mainly the past two years is undertaken of the industrial applications of pulsed power. Repetitively operated pulsed power generators with a moderate peak power have been developed for industrial applications. These generators are reliable and have low maintenance. Development of the pulsed power generators helps promote industrial applications of pulsed power for such things as food processing, medical treatment, water treatment, exhaust gas treatment, ozone generation, engine ignition, ion implantation and others. Here, industrial applications of pulsed power are classified by application for biological effects, for pulsed streamer discharges in gases, for pulsed discharges in liquid or liquid- mixture, and for material processing.

Recently, pulsed power technology has been applied to biological and medical fields. In particular, nanosecond pulsed electric fields (nsPEFs) have been expected to cause various biological reactions. This study explored to induction of endoplasmic reticulum (ER) stress response by nsPEFs in vivo and in vitro experiments. The ER stress is considered cause of disorders, such as diabetes and obesity. The control of ER stress response by nsPEFs can establish a new prevention and therapy for the disorders. A Blumlien-type pulse forming network (B-PFN) applied 14 ns-width voltage pulses on samples. The phosphorylation of eIF2α (P-eIF2α) was analyzed by western blotting and expression of mRNA related to P-eIF2α were evaluated by RT-PCR analysis. In vivo experiments, skeletal muscles of mice were exposed to the nsPEFs. The amount of Atf3, Atf4, CHOP, and Gadd34 which were ER stress sensor, was evaluated. The nsPEFs application induced the P-eIF2α, but other stress than ER stress response might be included. In vitro experiments adopted cultured cells as HeLa cells, HEK293 cells, and MEF cells. In HeLa cells, the P-eIF2α was confirmed and it depended on the number of applied pulses and the applied electric field. In western blotting for HEK293 and MEF cells, the P-eIF2α might occurred but consistent responses was not confirmed. The sensitivity for the nsPEFs would depend on cell species.

It is known empirically that the lightning stimulates plant growth in realm of agriculture. Furthermore, growth stimulations of pulsed power for mushrooms have been reported as well. Therefore, the application of pulsed power technology could enhance the growth of agricultural crops easily. This study examined the effects of electrical stimulation on mycelium of a fungus. Sparassis crispa. S. crispa contains a large amount of β-1, 3-glucan which has anticancer action. While there have been several experimental studies producing fruit body of fungi, we selected an experiment for mycelium of S. crispa. In case of mycelium cultivation, the culture period is shorter than fruit body and, the culture operation is relatively facile. A Blumlein-type pulse forming network (B-PFN) was used to generate electrical pulsed discharges of approximately 20 kV and 450 ns on the surface of the culture solution containing the mycelium of S. crispa. The length of discharges was approximately 14 mm. During the 10 day culture period, electrical pulse discharge treatment was applied on the second, fourth, and sixth day. The mycelium pellets were observed and metabolites were evaluated with a high-performance liquid chromatography (HPLC). The observed amount of β-1, 3-glucan in pulse-treated samples was significantly 1.22 times higher than in control samples.

Ozone has a very strong oxidizability. Generally, the method using dielectric barrier discharges is used for ozone production, but efficiency of the ozone production is not sufficient. In this study, streamer discharges generated with nanosecond pulsed powers were utilized for the ozone production. In our previous studies, it was found that an inner wire electrode in coaxial reactor curved during pulse operation. Then, spark discharges were frequently observed near the approximating point of the inner wire electrode to the outer electrode. The phenomena were considered as a cause of decay of produced ozone concentration. Here, we introduced reactors whose inner electrode wire was constrained so as not to be distorted. A tungsten wire as an inner electrode in a coaxial reactor prevented the distortion with slacking of the wire by its strength. Also stainless wires as inner electrode were wound around a glass rod to obtain the same effect. Additionally, increase in streamer discharges was expected owing to an increase in total length of four wires. In the experiments using these reactors, spark discharges were hard to occur and decay of ozone concentration with spark discharges was suppressed.

Recently, water pollution is one of environment issues around the world. We have studied a water treatment using nanosecond pulsed powers. The water treatment utilizes not only active species such as hydroxyl radical produced by electric discharges but also direct actions of discharges such as ultraviolet rays, shock wave and so on. In treatment for surfactant solution using pulsed power system, purified water and tap water was used as solvents of the solution. As a result, when purified water was used as solvent of solution, foaming which is a typical property of surfactants disappeared faster than in the case of using tap water as solvent. To investigate reasons of this result, disodium terephthalate was added to the solution. Disodium terephthalate was used to evaluate production of hydroxyl radical. Disodium terephthalate in purified water would react with more hydroxyl radical than in tap water. When an external ozonizer was used for water treatment instead of pulsed power system, production of hydroxyl radical in purified water was as much as in tap water. This is considered that more hydroxyl radical was generated by electric discharge in purified water because the conductivity of purified water was lower than that of tap water. On the other hand, in case of using external ozonizer without electric discharge, water treatment was unaffected by the conductivity of solution. Consequently, it seemed that electric discharges and lower conductivity of solution contributed treatment of organic compounds such as surfactant.

Nitrogen oxides (NOx) is one of atmospheric pollutants. We have studied removal of NOx from simulated flue gases using nanosecond pulsed powers. Non-thermal discharge plasma, as streamer discharges by nanosecond pulsed power, is efficient for NOx removal. Coaxial reactors, which consist of a stainless wire as an inner electrode and a stainless pipe as an outer electrode, have been used to generate streamer discharges in the experiment. In the experiment using the coaxial reactor, after when application of voltage pulses started, removal ratio of NOx increased and reached to the peak value, and then it decreased immediately. In order to investigate cause of the decrease in NOx removal ratio, discharges inside the reactor were observed. Spark discharges occurred near center of the coaxial reactor and the inner wire electrode was gradually attracted to the outer electrode. A reactor having a tensioned inner wire electrode by a weight was introduced to consider this phenomenon. In the reactor, the inner wire electrode did not slant regardless of occurrence of spark discharge when some tension was given to the inner electrode. The streamer discharges were distributed evenly around the wire electrode and the removal ratio was upheld at arriving peak ratio.

Induction of apoptosis by application of nanosecond pulsed electric fields (nsPEFs) on eukaryotic cells has been confirmed, and then the cancer treatment using the nsPEFs has been investigated. In this study, in vivo experiments have employed embryonic chick assay to apply nsPEFs to solid tumors. The embryonic chick assay can prepare a large number of samples with facility, in comparison to unexceptional animal experiments. The tumor cells: EMT6/KU (mouse breast adenocarcinoma cells), were planted on chorioallantoic membrane (CAM) in chicken egg from an aperture of the shell. The 2ns-PEFs were applied on the formed solid tumor by using a pulsed power generator. The solid tumors were dissected from the CAM and weighted three days after the nsPEFs application. The mean weight of the pulse-treated tumors was significantly smaller than that of controls which were not exposed nsPEFs. To understand the phenomena in the solid tumor, the apoptotic test using the florescence activated cell sorting (FACS) based on flow cytometry was performed on cell suspension applied nsPEFs in cuvette (in vitro). The viability of tumor cells was measured by the WST-1 assay (water soluble tetrazolium salts) in advance. The viability of pulse-treated samples was significantly smaller than that of controls. When the apoptosis test was performed for the samples obtained on this condition, it was found with the FACS that apoptosis was induced and necrosis would occur simultaneously in cells with nsPEFs.

To replace paper-based textbooks with web-based textbooks has caused several available features. The textbooks which are provided on the internet can always keep the latest information, and it is facile to include not only texts but also contents using multimedia and special functions. The web-based textbook on pulsed power, which is one of technical and science fields, has been prepared. In the textbook, the parts of pulsed power bases are described in classic text style and the chapter of pulsed power applications is provided by lectures with slides and vocal audios. Specialized calculators on pulsed power and virtual pulsed power laboratory consisting of several simulators are served through the web interface. A function of “Who's Who" is a database of the authors, researchers of pulsed power and users of this textbook in order to provide their communication by e-mails. A formation of the community for pulsed power researchers as well as learners is anticipated by using the database. This textbook will be beneficial to the education in graduate schools and to the COE program as a self-learning material.

Education has become more and more important in Japanese institutes of higher education. Under such circumstances, societies of the study of frontiers in education have been held since the first society at September 20, 2002. The valuable 158 presentations have been carried out during 11 societies till March, 2006. These presentations are classified according to the topics of subjects. The topics are the improvement of education methods, IT aided education, cooperation with elementary school, junior high school, high school and companies, hands-on training (manufacturing), JABEE and others. Some distinct presentations are summarized.

We developed a method for optimizing lighting design using the genetic algorithm. The floor illuminance of a room was obtained by superimposing the distributions that each light source produced. The illuminance distribution of each light source was calculated using the Monte Carlo Simulation and was stored in a database. The desirable illuminance distribution is obtained by selecting the light sources from the database by genetic algorithm. An optimization condition is represented by the fitness function of a genetic algorithm. To obtain a uniform illuminance distribution, we used the standard deviation of the floor illuminance. The standard deviation of the floor illuminance can be used as an index that represents the uniformity of the illuminance distribution. The lighting design in a simple cubic room is shown as an example. The illuminace distribution yielded by the location of the light sources that were selected using this technique was compared with that of evenly-spaced light sources on the ceiling plane. Although the room that we used was simple, the illuminace distribution obtained by using the technique almost corresponded to the target condition. This technique is practical for optimizing the arrangement of light sources inside a room. Moreover, this technique has various applications such as daylighting by choosing and constructing an applicable fitness function.