Naohiro Shimizu

Sterilization mechanism of nitrogen gas plasma: induction of secondary structural change in protein

The mechanism of action on biomolecules of N2 gas plasma, a novel sterilization technique, remains unclear. Here, the effect of N2 gas plasma on protein structure was investigated. BSA, which was used as the model protein, was exposed to N2 gas plasma generated by short‐time high voltage pulses from a static induction thyristor power supply. N2 gas plasma‐treated BSA at 1.5 kilo pulses per second showed evidence of degradation and modification when assessed by Coomassie brilliant blue staining and ultraviolet spectroscopy at 280 nm. Fourier transform infrared spectroscopy analysis was used to determine the proteins secondary structure. When the amide I region was analyzed in the infrared spectra according to curve fitting and Fourier self‐deconvolution, N2 gas plasma‐treated BSA showed increased α‐helix and decreased β‐turn content. Because heating decreased α‐helix and increased β‐sheet content, the structural changes induced by N2 gas plasma‐treatment of BSA were not caused by high temperatures. Thus, the present results suggest that conformational changes induced by N2 gas plasma are mediated by mechanisms distinct from heat denaturation.

N 2 gas plasma inactivates influenza virus by inducing changes in viral surface morphology, protein, and genomic RNA.

We have recently treated with N2 gas plasma and achieved inactivation of bacteria. However, the effect of N2 gas plasma on viruses remains unclear. With the aim of developing this technique, we analyzed the virucidal effect of N2 gas plasma on influenza virus and its influence on the viral components. We treated influenza virus particles with inert N2 gas plasma (1.5 kpps; kilo pulses per second) produced by a short high-voltage pulse generated from a static induction thyristor power supply. A bioassay using chicken embryonated eggs demonstrated that N2 gas plasma inactivated influenza virus in allantoic fluid within 5 min. Immunochromatography, enzyme-linked immunosorbent assay, and Coomassie brilliant blue staining showed that N2 gas plasma treatment of influenza A and B viruses in nasal aspirates and allantoic fluids as well as purified influenza A and B viruses induced degradation of viral proteins including nucleoprotein. Analysis using the polymerase chain reaction suggested that N2 gas plasma treatment induced changes in the viral RNA genome. Scanning electron microscopy analysis showed that aggregation and fusion of influenza viruses were induced by N2 gas plasma treatment. We believe these biochemical changes may contribute to the inactivation of influenza viruses by N2 gas plasma.

Repetitive Pulsed Power Based on Semiconductor Switching Devices

Static induction thyristor and silicon-carbide junction FET have been studied for applications to high-voltage modulators that are demanded by a new type of high-energy particle accelerator, the induction synchrotron. The switching characteristics of these power semiconductor devices are evaluated in order to assess their applicability to MHz level repetitive operation.

High rep-rate operation of pulsed power modulator using high voltage static induction thyristors

A repetitive pulsed power modulator, which uses high voltage static induction thyristors as main switching devices, has been designed and constructed for application to discharge light source. The main components of the power modulator are a pulse forming network (PFN) and a semiconductor switch. The PFN consists of 100 ceramic capacitors (2000 pF, 30 kV) connected in parallel. The measured impedance and output pulse width of PFN are 0.75 ohm and 427 ns, respectively. The semiconductor switch is made of 3 high voltage static induction thyristors connected in series, which is able to withstand 10 kV. The significant feature of the static induction thyristor is that it has very low ON-state voltage. This feature is especially suitable for high rep-rate operation of pulsed power modulators, since energy loss by switch can be remarkably reduced.

Efficiency of Atmospheric Pressure Nitrogen Gas Remote Plasma Sterilization and the Clarification of Sterilization Major Factors

Experiments reported here were conducted using atmospheric nitrogen gas remote plasma with a pulsed power source. The sterilization efficiency, major sterilization factors and most appropriate sterilization conditions were determined. By varying several factors such as hotplate temperature, relative humidity, water vapor supply location, etc., the most appropriate sterilization conditions were identified. The temperature of the hotplate was varied from 55°C to 75°C and with this 20°C increase in temperature, sterilization was completed in half the time. In this experiment, it was confirmed that the combined effect of a relative humidity (RH) of 0.5% and nitrogen gas was superior to the use of nitrogen gas alone. Furthermore, it was clarified that the optimal humidity was in the range of 0-5 % RH. When RHs of 0, 0.5 and 5% were tested, 0.5% RH was found to be optimal for sterilization. The location of the water vapor supply was changed relative to the hotplate, and use of the most remote port upstream of the reactor resulted in the most efficient sterilization. In addition, the results correlated with the amount of NO radicals generated. The NO radical is the precursor of OONO・(peroxynitrite anion radical). The sterilization factors associated with this experiment were NO radicals, H2O2, OH radicals, O2 ・(superoxide anion radicals) and OONO・only OONO・production correlated with sterilization efficiency. Therefore, OONO・is thought to be the major factor for nitrogen gas plasma sterilization. In addition, as already described, the highest sterilization efficiency was with 0.5% RH and the amount of OONO・produced correlated with the RH. These data support the idea that OONO・is the major contributing factor for nitrogen gas plasma sterilization. The D values for this experiment were approximately 10 min. *Corresponding author: Hideharu Shintani, Department of Science and Engineering, Chuo University, Kasuga Bunkyo 112-0003, Tokyo, Japan, Tel: +81338171733; E-mail: shintani@mail.hinocatv.ne.jp; hshintani@jcom.zaq.ne.jp Citation: Shintani, H., et al. Efficiency of Atmospheric Pressure Nitrogen Gas Remote Plasma Sterilization and the Clarification of Sterilization Major Factors. (2015) J Pharm Pharmaceutics 2(1): 1-7. Efficiency of Atmospheric Pressure Nitrogen Gas Remote Plasma Sterilization and the Clarification of Sterilization Major Factors Hideharu Shintani1*, Naohiro Shimizu2, Shouji Tange2, Nobuo Takahashi2, Akikazu Sakudo3, Akira Mizuno4, Eiki Hotta5 Received date: April 17, 2015 Accepted date: November 18, 2015 Published date: November 24, 2015 DOI: 10.15436/2377-1313.15.004 Journal of Pharmacy & Pharmaceutics www.ommegaonline.com J Pharm Pharmaceutics | volume 2: issue 1 Copyrights:

Compact pulsed power generators for industrial applications

Summary form only given, as follows. Summary form only given as follows. Compact pulsed power generators using high-power semiconductor switches are being developed at Nagaoka University of Technology, in collaboration with partners from Japanese industry. The switching units involved in these studies are the most up-to-date semiconductor switches such as static-induction thyristor (SI-thyristor), insulated gate bipolar transistor (IGBT), high-power metal-oxide-semiconductor field effect transistor (MOSFET), and semiconductor opening switch (SOS). The expected application areas are pulsed gas laser, flue-gas treatment, high-energy accelerator, and biomedical development. A very compact pulsed power generator using a single SI-thyristor as the main switch is developed for output parameters of 15 W, 20 A, 100 ns, and 2 kHz. It is driven by a 12 V DC power supply. It is designed for applications on automobile such as exhaust gas treatment. A stacked MOSFET switch has been developed and tested. Commercially available MOSFET units (1 kV, 10 A) were used to form the stack of 8 in series and 6 in parallel. Each unit is triggered by an optically coupled signal so that all units are controlled simultaneously by a common trigger circuit. Experimental results have shown that such a stacked MOSFET switch is capable of working under the voltage of 5 kV, turning on and off the load current of 100 A in /spl sim/30 ns, at the maximum repetition rate of 2 MHz. It is designed for applications to high-energy accelerators IGBTs and SOSs are used for different types of excimer laser drivers. The IGBT switch is combined with magnetic switches to generate pulsed output voltage of 28 kV at the repetition rate of 6 kHz. The generator using SOS as the main switch is more compact and has a potential for higher repetition rate.

High rep-rate inductive-energy-storage pulsed power modulator using high voltage static induction thyristor

Using a high voltage static induction thyristor (SI-Thy), we made a pulsed power modulator. The pulsed power modulator consists of a Blumlein line and a pulse transformer with amorphous cores. To evaluate the performance of the SI-Thy, the rise time of voltage pulse and the energy transfer efficiency from the pulse forming line to a matched load resistor were measured, changing turn-on gate voltages and charging voltages of the pulse forming line. The rise time of output voltage is decreasing with turn-on gate voltage. When a turn-on gate trigger voltage of 100V was applied, the rise time less than 90ns was attained for the charging voltage of 5000V. The energy transfer efficiency is increasing with turn-on gate trigger voltage and the efficiency higher than 90% was obtained for the charging voltage of 5000V under the condition that the turn-on gate trigger voltage is 100V.A high voltage static induction thyristor (SI Thy) has two significant features. One is that carriers can be quickly pulled out of gate region without applying a high voltage to the gate. The other is that its ON-state voltage is very low. These features make the SI Thy especially suitable for a switch of high rep-rate inductive-energy-storage pulsed power modulators, since the switch can interrupt a current rapidly and energy loss by the switch in a conduction phase can be remarkably reduced. In this research, a high rep-rate inductive-energy-storage pulsed power modulator, which uses a high voltage SI Thy as an opening switch, has been designed and constructed for application to an induction synchrotron. The maximum operating frequency of the modulator is expected to be 1 MHz. The induction synchrotron accelerates bunched charged particle beams using induced electric fields, which is proportional to the time derivative of magnetic flux in a toroidal core. In order to prevent a magnetic flux of the core from saturating, it is necessary to reset the toroidal core after each acceleration pulse. Therefore, a reset circuit independent of an acceleration circuit is needed in general. However, the proposed modulator can supply both the acceleration and the reset pulses without any additional circuit and is especially suitable for an induction synchrotron accelerator.

Switching properties of series connected static induction thyristor stack

In recent years, various semiconductor switches with ability of high voltage and current are researched and developed for electric power devices. Those merits are a long life time, high reliabilities and miniaturization of components. Our goal in this study is to examine switching properties of series connected Static Induction Thyristor (SI-Thy) stack for the purpose of applying to a pulsed power generator with pulse forming line (PFL). As a result, in the case of 3 SI-Thys connected in series, almost the same turn-on time (about 100 nanoseconds) was obtained at higher switch voltage (more than 10 kV). Our empirical result shows that the SI-Thy stack enables us to apply it to switch a pulsed power generator. Furthermore, we compared the characteristics of the stack with a simple.

Pulsed-power switching by power semiconductor devices

Summary form only given. Repetitive pulsed high-voltage modulators have been developed for industrial applications. They have used the most up-to-date power semiconductor devices such as power MOSFETs, silicon carbide JFETs, static-induction thyristors (SIThy), and semiconductor opening switches (SOS). As a new kind of high-energy particle accelerator, induction synchrotron requires pulsed high-voltage modulators with repetition rate on the order of 1 MHz. A test unit of stacked MOSFET has been successfully developed and tested for continuous operation. In the same time, SIThy and SiC-FET are also investigated for their performance as potential substitutes to MOSFET. A pulsed high-voltage generator using SOS has been developed for applications in sterilization. It consists of a primary unit which is switched by an IGBT and a secondary unit where two magnetic switches and an SOS are used. A pulse transformer is used to multiply the voltage between the two units. The output voltage pulses are of 60 kV in peak value and 50 ns in pulse width, with continuous repetition rate of 1 kHz

MHz pulsed power by semiconductor devices

Pulsed power generators with repetition rates on the order of MHz have been developed by using semiconductor opening switch (SOS), static induction thyristor (SIThy), and silicon carbide junction field-effect-transistor (SiC-JFET). A compact SOS circuit based on inductive energy storage has been developed. It uses semiconductor switches for forward and reverse current control of the SOS diodes, instead of commonly used magnetic switch. The repetition rate has reached 500 kHz (burst) for output voltage pulse of 10 kV and pulse width of 15 ns (FWHM). A full-bridge switching unit using SIThy has been developed and tested for bipolar square voltage pulse generation of plusmn 2 kV for a 100-Omega load, at repetition rate of 1 MHz (burst). A stacked SiC-JFET switching unit consists of 4 devices (2S x 2P) has been operated for 2 kV and 20 A at repetition rate up to 5 MHz (burst). Important issues on switching characteristics, such as rise- time, heat loading, and balance between devices have been studied. The MHz-repetitive power modulators are expected to have various applications in the future, especially for high- energy accelerators and biological treatment.