The Experts below are selected from a list of 43803 Experts worldwide ranked by ideXlab platform
Hao Zhang - One of the best experts on this subject based on the ideXlab platform.
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roles of membrane protein damage and intracellular protein damage in death of bacteria induced by atmospheric pressure Air Discharge plasmas
RSC Advances, 2018Co-Authors: Hao Zhang, Jie Shen, Shulou Qian, Yan Lan, Lili Ding, Weidong XiaAbstract:Although plasma sterilization has attracted much attention, the underlying mechanisms and biochemical pathways are still not fully understood. In this work, we investigate the molecular mechanism pertaining to the inactivation of Escherichia coli (E. coli) by Air Discharge plasmas. The membrane protein YgaP and intracellular protein swc7 are over-expressed in E. coli by genetic recombination and gene inducible expression techniques and plasma exposure is demonstrated to alter the structures of YgaP and swc7 in E. coli. The plasma-induced damage of YgaP and swc7 involves changes in the secondary and tertiary structures instead of the primary structure and the modification effectiveness depends on the storage time after the plasma treatment. Owing to the unique structure of E. coli, YgaP is more susceptible to the plasma treatment than intracellular swc7. Within 1 h after plasma exposure, YgaP is modified but not swc7, but after 1 h or longer, both YgaP and swc7 proteins are indeed modified. By analyzing the plasma-induced antimicrobial efficacy and modification of YgaP and swc7, plasma-induced modification of the membrane proteins is the major cause of bacterial death but there is no identifiable relationship with modification of the intracellular protein. The new results provide insights into the mechanism of multiple plasma-induced damage to bacteria and cells as well as the disinfection mechanism.
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genetic effects of an Air Discharge plasma on staphylococcus aureus at the gene transcription level
Applied Physics Letters, 2015Co-Authors: Jun Wei, Hao Zhang, Jie Shen, Yuan Liu, Zelong Zhang, Shulou Qian, Yan Lan, Ying Zhao, Weidong Xia, Qiang SunAbstract:The dynamics of gene expression regulation (at transcription level) in Staphylococcus aureus after different doses of atmospheric-pressure room-temperature Air plasma treatments are investigated by monitoring the quantitative real-time polymerase chain reaction. The plasma treatment influences the transcription of genes which are associated with several important bio-molecular processes related to the environmental stress resistance of the bacteria, including oxidative stress response, biofilm formation, antibiotics resistance, and DNA damage protection/repAir. The reactive species generated by the plasma Discharge in the gas phase and/or induced in the liquid phase may account for these gene expression changes.
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spectroscopic diagnostics of rotating gliding arc plasma codriven by a magnetic field and tangential flow
IEEE Transactions on Plasma Science, 2014Co-Authors: Ang Jian Wu, Sheng Yong Lu, Xiaodong Li, Hao Zhang, Chang Ming DuAbstract:Rotating gliding arc (RGA) Discharge, codriven by a magnetic field and tangential flow, has recently received increasing attention as an innovative technique for generating nonthermal equilibrium plasma at atmospheric pressure. To understand further the mechanism of RGA plasma applied in antipollution and the syngas production industry, optical emission spectroscopy, as a diagnostic technique, was applied to characterize the major active species (radicals, ions, atoms, and excited molecules) and energetic electrons in an RGA plasma. Nitrogen, Air, and argon were selected as carrier gases. The electron excitation temperature of the argon plasma was derived from a Boltzmann plot by analyzing the atomic spectral lines of argon and determined to be approximately 1.5 eV as a function of operating conditions. The active species generated in the Air and nitrogen Discharges were identified. The results indicated that the bands of the second positive system of N2 and the bands of the first negative system of N2+ were dominant in the nitrogen Discharge, whereas additional bands of the NO $\gamma $ system and OH(A–X) appeared in the Air Discharge. The variation trends of the emission intensities of the selected spectral bands, such as those of NO(259.5 nm), N2+(391.4 nm), N2(337 nm), and OH(309 nm), were investigated by varying the applied voltage and gas flow rate. The effects of these variations on the abovementioned active species were investigated in terms of the relative intensity of spectral emission to deduce the kinetic mechanism governing the observed reactions.
V I Oreshkin - One of the best experts on this subject based on the ideXlab platform.
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simulation of a runaway electron avalanche developing in an atmospheric pressure Air Discharge
Physics of Plasmas, 2015Co-Authors: E V Oreshkin, S A Barengolts, Stanislav A Chaikovsky, V I OreshkinAbstract:To gain a better understanding of the operation of atmospheric pressure Air Discharges, the formation of a runaway electron beam at an individual emission site on the cathode has been numerically simulated. The model provides a description of the dynamics of the fast electrons emitted into an Air gap from the surface of the emission zone by solving numerically two-dimensional equations for the electrons. It is supposed that the electric field at the surface of the emission zone is enhanced, providing conditions for continuous acceleration of the emitted electrons. It is shown that the formation of a runaway electron beam in a highly overvolted Discharge is largely associated with avalanche-type processes and that the number of electrons in the avalanche reaches 50% of the total number of runaway electrons.
Osamu Fujiwara - One of the best experts on this subject based on the ideXlab platform.
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Specific Dependence on Absolute Humidity and Saturation Deficit of Air Discharge Currents from Electrostatic Discharge Generator with Different Approach Speeds
2019 IEEE International Symposium on Electromagnetic Compatibility Signal & Power Integrity (EMC+SIPI), 2019Co-Authors: Takeshi Ishida, Osamu FujiwaraAbstract:The International Electro-technical Commission (IEC) specifies Air Discharge immunity testing for electronic equipment in the standard 61000-4-2 under the climatic conditions of relative humidity from 30 to 60 % and ambient temperature from 15 to 35 degrees Celsius. For aiming to improve the testing reproducibility, to clarify effects of the above climate parameters on Air Discharge testing, we previously measured Air Discharge currents from an electrostatic Discharge (ESD) generator with an approach speed of 80 mm/s under 6 combinations of relative humidity and temperature. The result showed that the same absolute humidity provides almost similar waveforms of the Discharge currents despite different relative humidity and temperature. In this study, to further examine such combined effects, we measure Air Discharge currents from the ESD generator at a test voltage of 15 kV with three different approach speeds of 20 mm/s, 50 mm/s and 80 mm/s under 9 combinations of relative humidity and temperature inside and outside the IEC specified climate ranges. As a result, Air Discharge current behavior is affected by not only absolute humidity (AH) but also saturation deficit (SD) or the difference between the AH and the saturated water vapor amount. The humidity dependence differs according to the IEC specified and non-specified climate ranges, while it can well be explained by the SD. Under the IEC specified conditions, at faster approach speeds, the peak currents of Air Discharges have maximum values at AH7.70 g/m3 and SD15.36 g/m3, whereas they are 1.2 to 1.4 times larger compared to those at almost the same AH7.71 g/m3 and smaller SD5.14 g/m3, respectively. In the IEC non-specified climate range, however, regardless of the approach speeds, the current peaks noticeably reach maximum values at AH3.81 g/m3 and SD19.26 g/m3, which are 3.6 to 5.2 times larger than those at roughly the same AH3.96 g/m3 and larger SD35.64 g/m3, respectively.
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further effects of test voltages relative humidity and temperature on Air Discharge currents from electrostatic Discharge generator
International Symposium on Electromagnetic Compatibility, 2019Co-Authors: Takeshi Ishida, Osamu FujiwaraAbstract:Air Discharge immunity testing for electronic equipment is specified in the standard 61000-4-2 of the International Eelectrotechnical Commission (IEC) under the climatic conditions of relative humidity from 30 to 60 % and temperature from 15 to 35 degrees Celsius. This implies that the Air Discharge testing is likely to provide significantly different test results due to a wide climate range. To clarify effects of the above climate conditions on Air Discharge testing, we previously measured Air Discharge currents from an electrostatic Discharge (ESD) generator with test voltages from 2 kV to 15kV at an approach speed of 80 mm/s under 6 combinations of relative humidity and temperature in the IEC specified and non-specified climate range. The result showed that the same absolute humidity provides almost the identical waveforms of the Discharge currents despite different relative humidity and temperature, and also that the current peaks at higher test voltages decrease as the absolute humidity increases. In this study, we further examine the effects of Air Discharges on test voltages, relative humidity and temperature with respect to two different approach speeds of 80 mm/s and 20 mm/s. As a result, the approach speed of 80 mm/s is confirmed to provide the same results as the previous ones under the identical climate conditions, while at a test voltage of 15 kV in the IEC specified climate range 20 mm/s approach speed causes the current waveforms entirely different from those at 80 mm/s despite the same absolute humidity, and the peaks are not affected by the absolute humidity, however, under the IEC non-specified climate conditions, likewise the case at 80 mm/s, the peaks decrease at higher test voltages as the absolute humidity increases.
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waveform comparison and difference factors in Discharge currents for Air Discharges from different esd generators
Electrical Engineering in Japan, 2017Co-Authors: Yoshinori Taka, Takeshi Ishida, Osamu FujiwaraAbstract:SUMMARY Electrostatic Discharge (ESD) generators must be calibrated for contact Discharges with the current waveform specified in International Electro-technical Commission (IEC)61000-4-2; however, there are no requirements in current waveforms due to their bad reproducibility for Air Discharges in the IEC standard. Nevertheless, the Air Discharge immunity testing is under obligation in the present standard. This implies that different ESD generators are likely to provide significantly different test results for Air Discharge testing. In this study, two types of different ESD generators were used to measure Discharge currents both for contact and Air Discharges with respect to charge voltages from 2 kV to 8 kV under the same conditions of experimental environment. As a result, we confirmed that the measured waveforms were almost identical for contact Discharges regardless of charge voltages, while we found that they are quite different for Air Discharges with the same approaching speed when the charge voltages are increased. The latter result is because the generator has different impedance characteristics deriving from its structure, and because the spark lengths from the generators with the same charge voltage are different. A formula for calculating the Discharge current from an ESD generator through an ideal switch in lieu of a spark, which was previously derived by us, was also employed to obtain the current waveform peculiar to the generator, in order to reveal that the formula provides the different upper limit of Air Discharge current peaks according to the generator.
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a measurement on electromagnetic noises from esd generator just before and after esd testing
International Symposium on Electromagnetic Compatibility, 2014Co-Authors: Takeshi Ishida, Osamu Fujiwara, Yukihiro Tozawa, Mutsumu Takahashi, Shuichi NittaAbstract:It is widely recognized that electrostatic Discharge (ESD) generators cause electromagnetic (EM) noises even before and after ESD immunity testing specified in the International Electrotechnical Commission (IEC) standard. This may provide inconsistent test results, whereas its mechanism is not well understood. To explain the mechanism qualitatively, the authors investigated a generation modeling of EM noises from an ESD generator in conjunction with the functional sequences of built-in relay switches and a DC high voltage power supply. To validate this model, using a magnetic field probe, the authors measure the induced noise voltages from an ESD generator just before and after ESD testing for contact and Air Discharges to an IEC recommended current injection target. As a result, it is confirmed that the EM noises are generated when the relay switches operate before and after ESD tests. In addition, the authors find that the noises amplitude for low voltages (Types C, D and F) are relatively smaller than the ones (Types A&B, E) induced at the testing in both the contact and Air Discharge modes, while these peak noises increase with charging voltages and especially the noise peaks induced after the testing reach almost the same level as the case for 4 kV ESD test in the Air Discharge mode. A new sequence of the built-in relay switch is also proposed for reducing the noise voltages generated after ESD testing.
F H L R Clemens - One of the best experts on this subject based on the ideXlab platform.
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experimental study of Air water flow in downward sloping pipes
International Journal of Multiphase Flow, 2011Co-Authors: I W M Pothof, F H L R ClemensAbstract:This paper presents results from seven experimental facilities on the co-current flow of Air and water in downward sloping pipes. As a function of the Air flow rate, pipe diameter and pipe slope, the required water Discharge to prevent Air accumulation was determined. In case the water Discharge was less than the required water Discharge, the Air accumulation and additional gas pocket head loss were measured. Results show that volumetric Air Discharge as small as 0.1% of the water Discharge accumulate in a downward sloping section. The experimental data cover all four flow regimes of water-driven Air transport: stratified, blow-back, plug and dispersed bubble flow. The analysis of the experimental results shows that different dimensionless numbers characterise certain flow regimes. The pipe Froude number determines the transition from blow-back to plug flow. The gas pocket head loss in the blow-back flow regime follows a pipe Weber number scaling. A numerical model for the prediction of the Air Discharge as a function of the relevant system parameters is proposed. The novelty of this paper is the presentation of experimental data and a numerical model that cover all flow regimes on Air transport by flowing water in downward inclined pipes.
Weidong Xia - One of the best experts on this subject based on the ideXlab platform.
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roles of membrane protein damage and intracellular protein damage in death of bacteria induced by atmospheric pressure Air Discharge plasmas
RSC Advances, 2018Co-Authors: Hao Zhang, Jie Shen, Shulou Qian, Yan Lan, Lili Ding, Weidong XiaAbstract:Although plasma sterilization has attracted much attention, the underlying mechanisms and biochemical pathways are still not fully understood. In this work, we investigate the molecular mechanism pertaining to the inactivation of Escherichia coli (E. coli) by Air Discharge plasmas. The membrane protein YgaP and intracellular protein swc7 are over-expressed in E. coli by genetic recombination and gene inducible expression techniques and plasma exposure is demonstrated to alter the structures of YgaP and swc7 in E. coli. The plasma-induced damage of YgaP and swc7 involves changes in the secondary and tertiary structures instead of the primary structure and the modification effectiveness depends on the storage time after the plasma treatment. Owing to the unique structure of E. coli, YgaP is more susceptible to the plasma treatment than intracellular swc7. Within 1 h after plasma exposure, YgaP is modified but not swc7, but after 1 h or longer, both YgaP and swc7 proteins are indeed modified. By analyzing the plasma-induced antimicrobial efficacy and modification of YgaP and swc7, plasma-induced modification of the membrane proteins is the major cause of bacterial death but there is no identifiable relationship with modification of the intracellular protein. The new results provide insights into the mechanism of multiple plasma-induced damage to bacteria and cells as well as the disinfection mechanism.
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genetic effects of an Air Discharge plasma on staphylococcus aureus at the gene transcription level
Applied Physics Letters, 2015Co-Authors: Jun Wei, Hao Zhang, Jie Shen, Yuan Liu, Zelong Zhang, Shulou Qian, Yan Lan, Ying Zhao, Weidong Xia, Qiang SunAbstract:The dynamics of gene expression regulation (at transcription level) in Staphylococcus aureus after different doses of atmospheric-pressure room-temperature Air plasma treatments are investigated by monitoring the quantitative real-time polymerase chain reaction. The plasma treatment influences the transcription of genes which are associated with several important bio-molecular processes related to the environmental stress resistance of the bacteria, including oxidative stress response, biofilm formation, antibiotics resistance, and DNA damage protection/repAir. The reactive species generated by the plasma Discharge in the gas phase and/or induced in the liquid phase may account for these gene expression changes.