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Plasma Science, IEEE Transactions on

Issue 4 • Date Aug. 2006

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  • Table of contents

    Publication Year: 2006 , Page(s): c1 - 1249
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    Freely Available from IEEE
  • IEEE Transactions on Plasma Science publication information

    Publication Year: 2006 , Page(s): c2
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  • Special Issue on Nonthermal Medical/Biological Applications Using Ionized Gases and Electromagnetic Fields

    Publication Year: 2006 , Page(s): 1250 - 1252
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  • Spores Survivability After Exposure to Low-Temperature Plasmas

    Publication Year: 2006 , Page(s): 1253 - 1256
    Cited by:  Papers (7)
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    To date, research on the inactivation of microorganisms by nonequilibrium atmospheric pressure plasmas has mainly been concerned by the killing efficiency and/or with the study of the roles played by various plasma agents (ultraviolet, radicals, ions, etc.) in the inactivation process. In this paper, the authors look at the problem from the cells' side. More specifically, the following questions are asked: What part of the spore structure plays a crucial role in its defense against the unfavorable plasma environment, and if the cells do survive plasma treatment, do they emerge the same or do they undergo some kind of noticeable changes? Although complete and comprehensive answers to these questions are not at the authors' grasp at this time, this paper presents convincing preliminary data that show that the integrity of the proteins of a spore's coat plays a major role in its survivability and that cells that survive air plasma exposure emerge with a changed metabolism View full abstract»

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  • Bactericidal Action of the Reactive Species Produced by Gas-Discharge Nonthermal Plasma at Atmospheric Pressure: A Review

    Publication Year: 2006 , Page(s): 1257 - 1269
    Cited by:  Papers (17)
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    Biological decontamination using a nonthermal gas discharge at atmospheric pressure in air is the subject of significant research effort at this time. The mechanism for bacterial deactivation undergoes a lot of speculation, particularly with regard to the role of ions and reactive gas species. Two mechanisms have been proposed: electrostatic disruption of cell membranes and lethal oxidation of membrane or cytoplasmic components. Results show that death is accompanied by cell lysis and fragmentation in Gram-negative bacteria but not Gram-positive species, although cytoplasmic leakage is generally observed. Gas discharges can be a source of charged particles, ions, reactive gas species, radicals, and radiation (ultraviolet, infrared, and visible), many of which have documented biocidal properties. The individual roles played by these in decontamination are not well understood or quantified. However, the reactions of some species with biomolecules are documented otherwise in the literature. Oxidative stress is relatively well studied, and it is likely that exposure to gas discharges in air causes extreme oxidative challenge. In this paper, a review is presented of the major reactive species generated by nonthermal plasma at atmospheric pressure and the known reactions of these with biological molecules. Understanding these mechanisms becomes increasingly important as plasma-based decontamination and sterilization devices come closer to a wide-scale application in medical, healthcare, food processing, and air purification applications. Approaches are proposed to elucidate the relative importance of reactive species View full abstract»

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  • Plasma Lysis for Identification of Bacterial Spores Using Ambient-Pressure Nonthermal Discharges

    Publication Year: 2006 , Page(s): 1270 - 1274
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    Atmospheric-pressure nonthermal plasmas have demonstrated rapid lysis of bacterial spores such as Bacillis subtilis after a few minutes of ionized-gas exposure. This paper is focused on comparing the ionized-gas treatment of spores on a surface (or dry lysis) with typical sonication of spore suspensions. Surprisingly, the deoxyribonucleic acid (DNA) recovered by plasma processing was larger and intact compared with conventional sonication processes used to disrupt spores. Most importantly, the ionized-gas lysis technique recovered only the DNA from the interior of the spore, rendering any nucleic acids found on the spore coat unavailable for replication processes used for identification. Plasma processing behaved as the controllable electronic equivalence of DNAse-an enzyme that consumes DNA. The rapid lysis of bacterial spores and other cells by ionized gases has led to incorporating plasma pretreatment with pathogen detection instruments such as mass spectrometers. To this end, the identification by mass spectrometry of the extracted proteins from plasma-lysed spores facilitated the discovery of a novel detection approach. Unique identifiable proteins and nucleic acids associated with each Bacillus specie are made available by plasma treatment to facilitate detection View full abstract»

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  • Killing of Bacterial Spores Contained in a Paper Envelope by a Microwave Plasma Torch

    Publication Year: 2006 , Page(s): 1275 - 1280
    Cited by:  Papers (3)
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    The air plasma effluent of an arc-seed microwave torch is used to kill bacterial spores contained inside an envelope. The torch is operated at a 60-Hz periodic mode (with about 40% duty cycle) and runs stably at a low airflow rate (e.g., 0.393 l/s). The images of plasma torch plumes show that the arc loop of the discharge prolongs from the electrodes by nearly 3 cm and microwave energizes the charge particles along the arc loop considerably. The emission spectroscopy of the torch indicates that the plasma effluent contains an abundance of reactive atomic oxygen. Bacillus cereus is chosen for the biological agent in the decontamination experiment. The experiment and the decontamination efficacy of this torch are presented. The averaged temperature inside the envelope is measured to be less than 40degC, thus ruling out the thermal decontamination mechanism View full abstract»

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  • Scanning Electron and Atomic Force Microscopy to Study Plasma Torch Effects on B. cereus Spores

    Publication Year: 2006 , Page(s): 1281 - 1289
    Cited by:  Papers (4)
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    The occurrence of scanning electron microscopy (SEM) and atomic force microscopy (AFM) side-by-side is becoming increasingly common in analytical research. This article shows microscopy techniques to image Bacillus spores, to measure spore dimensions, and to demonstrate how these methods provide supplementary information to study plasma torch effects. This paper demonstrates that observed morphologies of spores before and after exposure to a plasma torch are remarkably different. The use of SEM and AFM as a tool complex enables examination of spore morphology and dimensions as well as their alterations during decontamination using plasma torch View full abstract»

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  • Bacterial Inactivation Using an RF-Powered Atmospheric Pressure Plasma

    Publication Year: 2006 , Page(s): 1290 - 1296
    Cited by:  Papers (3)
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    Cells of Escherichia coli were exposed to a downstream plasma afterglow plume emitted from a slotted plasma device operating in open air at atmospheric pressure. Various feed-gas mixtures were capacitively excited, as they flowed into open air past radio frequency-powered electrodes. To estimate the underlying inactivation pathways, various experimental conditions were tested by incorporating ultraviolet filters, varying parameters such as electrical power and frequency, feed-gas composition and flow rates, and the distance of the samples from the electrode. Experimental results demonstrated a colony-forming unit reduction of well over five logs with less than 2 s of exposure per unit area. These results offer a promising means of wide-area inactivation of harmful microbes in a practical environment, where the sample is neither a part of the electrical circuit nor placed in an enclosure. The device is electrically grounded and could be held like a wand applicator View full abstract»

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  • Modeling the Inactivation Kinetics of Bacillus subtilis Spores by Nonthermal Plasmas

    Publication Year: 2006 , Page(s): 1297 - 1303
    Cited by:  Papers (1)
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    The inactivation performances of different nonthermal plasmas are often compared with each other in terms of their decimal reduction values, typically obtained by linearizing selected segments of their inactivation curves. However, this approach is subjective and can result in uncertainties in the prediction of this parameter. To overcome this, in this paper, the application of models capable of describing inactivation curves in their entirety is considered. The authors employ the Baranyi and Weibull models, both commonly used for microbial inactivation by heat. An empirical model based on a third-order polynomial to seek greater accuracy is further proposed. Using these three inactivation models, predictions of decimal reduction values for 11 plasma inactivation studies of Bacillus subtilis spores are obtained and compared with their reported values. Although the agreement obtained between these different approaches is generally fair, the current practice of segmented linearization is shown to be overly simplistic. A rigorous model is therefore critical to capture the essentially nonlinear character of plasma inactivation kinetics and hence allow for an objective comparison of the performances of similar biocidal nonthermal plasmas View full abstract»

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  • Biofilm Destruction by RF High-Pressure Cold Plasma Jet

    Publication Year: 2006 , Page(s): 1304 - 1309
    Cited by:  Papers (7)  |  Patents (1)
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    Biofilms are bacterial communities embedded in a glue-like matrix mostly composed of exopolysaccharides and a small amount of proteins and nucleic acids. Conventional disinfection and sterilization methods are often ineffective with the biofilms since microorganisms within the biofilm show different properties from those in free planktonic life. The use of the gas discharge plasmas is a novel alternative since the plasmas contain a mixture of charged particles, chemically reactive species, and UV radiation. The four-day-old single-species biofilms were produced using Chromobacterium violaceum, a gram-negative bacterium commonly present in soil and water. The gas discharge plasma was produced by using an Atomflo 250 reactor (Surfx Technologies), and the bacterial biofilms were exposed to it for different periods of time. Our results show that a 10-min plasma treatment is able to kill almost 100% of the cells. The results show a rapid initial decline in the colony forming units per milliliter (phase one) that is followed by a much slower subsequent decline (phase two) of the D-values that are longer than the inactivation of the planktonic organisms, suggesting a more complex inactivation mechanism for the biofilms. Two hypotheses are offered to explain this biphasic behavior. Optical emission spectroscopy was used to study the plasma composition, and the role of the active species is discussed. These results indicate the potential of plasma as an alternative way for biofilm removal View full abstract»

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  • Physical Mechanisms of Inactivation of Bacillus subtilis Spores Using Cold Atmospheric Plasmas

    Publication Year: 2006 , Page(s): 1310 - 1316
    Cited by:  Papers (19)  |  Patents (4)
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    This paper presents a detailed study of the potential physical mechanisms of the microbial inactivation by cold atmospheric plasmas. With the Bacillus subtilis spores as a model microorganism and an atmospheric-plasma plume in helium flow, optical emission spectroscopy and inactivation kinetics are used to demonstrate the dominating role played by the reactive oxygen species (e.g., atomic oxygen and OH) as well as the minor contributions of the UV photons, heat, charged particles, and electric fields. To differentiate the concentrations of the reactive oxygen species, an atmospheric helium-oxygen plasma is also used for the spore inactivation. Results with the helium and the helium-oxygen plasmas are contrasted to highlight how the production of the spore-killing oxygen species may be enhanced View full abstract»

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  • Killing of S. mutans Bacteria Using a Plasma Needle at Atmospheric Pressure

    Publication Year: 2006 , Page(s): 1317 - 1324
    Cited by:  Papers (10)  |  Patents (31)
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    Streptococcus mutans (S. mutans) bacteria were killed using a low-power millimeter-size atmospheric-pressure glow-discharge plasma or plasma needle. The plasma was applied to a culture of S. mutans that was plated onto the surface of an agar nutrient in a Petri dish. S. mutans is the most important microorganism for causing dental caries. A spatially resolved biological diagnostic of the plasma is introduced, where the spatial pattern of bacterial colonies in the sample was imaged after plasma treatment and incubation. For low-power conditions that would be attractive for dentistry, images from this biological diagnostic reveal that S. mutans was killed within a solid circle with a 5-mm diameter, demonstrating that site-specific treatment is possible. For other conditions, which are of interest for understanding plasma transport, images show that bacteria were killed with a ring-shaped spatial pattern. This ring pattern coincides with a similar ring in the spatial distribution of energetic electrons, as revealed by Abel-inverted images of the glow. The presence of the radicals OH and O was verified using optical-emission spectroscopy View full abstract»

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  • Plasma-Needle Treatment of Substrates With Respect to Wettability and Growth of Escherichia coli and Streptococcus mutans

    Publication Year: 2006 , Page(s): 1325 - 1330
    Cited by:  Papers (1)  |  Patents (52)
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    In this paper, surface modification of various materials exposed to a nonthermal atmospheric plasma is investigated. The used source is the plasma needle: a radio-frequency-driven nonthermal atmospheric microplasma. A number of substrates (Perspex and polystyrene) were treated with the plasma needle. The modification of materials was subsequently identified as hydrophilization of the surface and was experimentally validated by water-contact-angle measurements. Furthermore, the effect of this modification on the growth of two bacterial species, which are the Escherichia coli and Streptococcus mutans, is studied. The bacteria were cultured on treated and nontreated polystyrene 96-well plates; the growth of E. coli on the treated substrates was enhanced, while for S. mutans, it was reduced. An explanation of these effects is provided View full abstract»

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  • Reattachment and Apoptosis After Plasma-Needle Treatment of Cultured Cells

    Publication Year: 2006 , Page(s): 1331 - 1336
    Cited by:  Papers (8)  |  Patents (50)
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    Nonthermal plasmas can be used to locally influence cell adhesion: cells can be removed from their surroundings without causing necrosis. In fact, cells remain alive and can reattach within hours. This phenomenon may, in the future, be used for microsurgical procedures. Another method to remove cells is to induce apoptosis or programmed cell death. This type of cell death is preferred above necrosis, which may cause inflammation reactions. When the detached cells are allowed to reattach and grow, it is important to know their condition. Therefore, long-term effects of plasma-needle treatment were assessed, with special focus on reattachment and apoptosis. The cells were treated using a plasma needle. This device generates a small (1-mm diameter) plasma at atmospheric pressure. To avoid any heat effects, it is important that the plasma temperature is at or below physiological temperature. This is the case for the plasma needle View full abstract»

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  • Surgical Instrument Decontamination: Efficacy of Introducing an Argon:Oxygen RF Gas-Plasma Cleaning Step as Part of the Cleaning Cycle for Stainless Steel Instruments

    Publication Year: 2006 , Page(s): 1337 - 1344
    Cited by:  Papers (1)
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    The decontamination of a range of "in-use" stainless steel surgical instruments by conventional hospital reprocessing techniques was studied, using scanning electron microscopic (SEM) and energy dispersive X-ray spectroscopic (EDX) analyses, with results obtained when an Ar:O2 RF gas-plasma treatment step was added to the cleaning cycle. In some cases, protein contaminants were still retained on instruments subjected to conventional cleaning and sterilization after seven cleaning cycles. No retention of contamination was evident on the surfaces of instruments that were subjected to gas-plasma cleaning. The efficacy of the plasma decontamination is significantly improved by hydration of the tissue residues immediately before exposure to the plasma. The reasons for this are not known, but it is suggested that the production of excited OH radicals and H atoms within the tissue matrix may play some part. Deposition of fluorescently labeled protein from physiological saline solution shows that protein is incorporated into salt crystals formed on stainless steel surfaces. This protein is resistant to plasma etching, but it is shown that water treatment results in improved cleaning. A combination of effects including physical "cracking" of the salt crystals under vacuum and dissolution of the inorganic matrix, which could possibly be accelerated by dipolar heating of the aqueous phase, may be responsible View full abstract»

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  • Research on Air Purification Efficiency by Nonthermal Plasma Along With the Application of Magnetic Field

    Publication Year: 2006 , Page(s): 1345 - 1350
    Cited by:  Papers (2)
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    Nonthermal plasma created by high-voltage dc power supply can be used to collect precharged suspended particulates, whereas nonthermal plasma generated by high-voltage pulsed power supply is used to remove harmful gases in the air, but how to increase the efficiency is not clear. In this paper, it is novel to apply magnetic field to air purification to increase the purification efficiency. Effect of magnetic field is analyzed. It can be concluded that purification efficiency can be improved significantly along with the application of magnetic field View full abstract»

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  • The Effect of Inhaled Air Ions Generated by Technical Ionizers and a Bioionizer on Rat Trachea Mucosa and the Phagocytic Activity of Blood Cells

    Publication Year: 2006 , Page(s): 1351 - 1358
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    It was shown for the first time that inhaling negative air ions (NAI) leads to changes in the functional state of the rat trachea mucosa, which in turn affects the phagocytic activity of blood cells. The effect depends on the concentration of the NAI, the duration of their action, and the sources of the NAI generation. For air ionization, technical ionizers and a bioionizer (a plant electrified through soil) developed by the Diod Company, Moscow, Russia were used. It was shown that the NAI at high doses (600 000 ion/cm3), generated by an Elion 131M device, induce a damage to the rat trachea mucosa, an inhibition of the activity of its antioxidant enzymes, and a decrease in the phagocytic activity of whole blood cells. Low doses of the NAI from the same source (25 000-50 000 ion/cm3) and high doses of the NAI from devices Elion 132S and 132R (320 000-500 000 ion/cm3), and a bioionizer (500 000 ion/cm3) produced a milder effect, activating the secretion of goblet cells of the trachea mucosa without its damage. A possible mechanism of the effect of inhaled NAI as exogenous reactive oxygen species (ROS) on internal processes in the organism is discussed. The involvement of the ROS in the action of ionized air found in the study is probably the general property of different electrical influences on biological objects. Therefore, the result of the investigation may be of interest for a wide circle of specialists dealing with ElectroMed influences View full abstract»

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  • UV Excimer Lamp Irradiation of Fibroblasts: The Influence on Antioxidant Homeostasis

    Publication Year: 2006 , Page(s): 1359 - 1364
    Cited by:  Papers (5)  |  Patents (51)
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    UV excimer lamps are efficient and economical narrowband sources of UVB and UVC radiation. Potentially, these lamps may be used in bacterial disinfection or in minor cosmetic procedures, but safety tests are necessary. For this purpose, cellular damage induced by the UV radiation is assessed. 3T3 mouse fibroblasts are used as a model system. It is found that lethal damage occurs above a certain wavelength-dependent threshold dose. Furthermore, the antioxidant balance of the cells is influenced; glutathione levels are usually depleted, both under and above the lethal threshold. A striking increase of glutathione level is observed after UVC irradiation. This is attributed to an enhanced repair activity as a response to acute oxidative stress induced by UVC. In contrast to UVC, low-power irradiation with UVB seems to induce very little cellular damage View full abstract»

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  • Comparative Research of Efficiency of Water Decontamination by UV Radiation of Cold Hollow Cathode Discharge Plasma Versus That of Low- and Medium-Pressure Mercury Lamps

    Publication Year: 2006 , Page(s): 1365 - 1369
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    In this paper, the results of experimental studies of peculiarities of Escherichia coli water suspension inactivation by ultraviolet radiation of hollow cathode discharge plasma in different gaseous media are presented. It is shown that efficiency of the inactivation by the discharges on oxygen, mixtures of oxygen with deuterium, and water vapor is essentially higher than that by the discharge on air, as well as the discharges of low- and medium-pressure mercury lamps View full abstract»

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  • Bacterial Decontamination of Water by Bipolar Pulsed Discharge in a Gas–Liquid–Solid Three-Phase Discharge Reactor

    Publication Year: 2006 , Page(s): 1370 - 1374
    Cited by:  Papers (4)
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    Inactivation of Escherichia coli by bipolar pulsed discharge in an air-liquid-solid three-phase discharge reactor has been investigated. The effect of several operating parameters on the inactivation efficiency has also been studied. Experimental results showed that bipolar pulsed discharge in the three-phase discharge plasma reactor had good performance in the inactivation of E. coli. Power intensity and gas flow rate had a positive effect on the inactivation, while the initial solution conductivity had little effect. An alkaline solution condition was favorable for the inactivation of E. coli in the reactor. In addition, possible mechanisms of the inactivation were also discussed View full abstract»

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  • Water Treatment by Fast Oxygen Radical Flow With DC-Driven Microhollow Cathode Discharge

    Publication Year: 2006 , Page(s): 1375 - 1381
    Cited by:  Papers (2)
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    Water treatment with ozone has been utilized, but a higher oxidation technology is required to decompose persistent substances such as dioxin. In this paper, water treatment by a direct O radical injection method with dc-driven atmospheric microplasma and fast oxygen gas flow was examined. O radicals and OH radicals are able to realize stronger oxidation processes than those of the ozone method. The effect of water treatment by radical injection was observed by measurement of the acetic-acid (CH3COOH) decomposition. This was examined while varying the discharge current and oxygen gas flow rates. The acetic acid was successfully decomposed by a direct radical flow into the solution; meanwhile, no decomposition was observed with ozone injection. A clear correlation was found between the decomposition rate and the gas-flow velocity estimated by the gas-flow rates. This result indicates that the rapid radical injection is crucial at the gas-liquid interface because a key radical, which is thought to be O, has a very short lifetime in atmospheric oxygen View full abstract»

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  • Generation of Two Successive Shock Waves Focused to a Common Focal Point

    Publication Year: 2006 , Page(s): 1382 - 1385
    Cited by:  Papers (4)
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    A generator of two successive shock waves focused on a common focal point has been developed. Cylindrical pressure waves created by multichannel electrical discharges on two cylindrical composite anodes are focused by a metallic parabolic reflector-cathode. Near the common focus, the waves are transformed into strong shock waves. The anodes are energized from separate power supplies. This allows us to vary the time interval between the discharges and stagger the waves' arrival to the focal point. Schlieren photographs of the focal region show that mutual interaction of the two waves results in generation of a large number of secondary short wavelength shocks. Measurements of the shock waveforms at the focus demonstrate that the second (i.e., later arriving) wave is strongly attenuate due to the medium inhomogeneity produced by the first wave. Localized injury of a rabbit's liver induced by the shock waves has been demonstrated by the method of magnetic resonance imaging. Histological examination of the liver samples taken from the injured region revealed a very sharp boundary between the injured and healthy tissues View full abstract»

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  • Microbial Inactivation in Water Using Pulsed Electric Fields and Magnetic Pulse Compressor Technology

    Publication Year: 2006 , Page(s): 1386 - 1393
    Cited by:  Papers (13)
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    Pulsed electric field (PEF) disinfection is a promising technology for the nonthermal disinfection of water. Magnetic pulse compressors due to their high repetition rates and lifetimes, appear to be a promising alternative to the existing pulse forming circuits used for sterilization applications. The application of these systems for the purification of water has yet to be explored. The use of the short duration electrical pulses from the magnetic pulse compressor for inactivation of spores, bacteria (Escherichia coli) and viruses in drinking water is being investigated at the University of Missouri, Columbia. The test cell designed herein allows flowing tests for pulsewidths of 130-500 ns. The coupling of the magnetic modulator with the test cell and the inactivation protocols that aim at effective inactivation under optimal conditions are discussed. A 4 log reduction was seen for (Escherichia coli) E. coli at field strengths of 110 kV/cm and 70 pps, with a total energy consumption of 40 J/cm3. A comparative study of different parameters, e.g., pulsewidth, electrode gap, frequency, and electric field, which effect the microbial inactivation are also presented View full abstract»

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  • The Spatially Distributed Dynamic Transmembrane Voltage of Cells and Organelles due to 10 ns Pulses: Meshed Transport Networks

    Publication Year: 2006 , Page(s): 1394 - 1404
    Cited by:  Papers (17)
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    The authors describe two versions of a two-dimensional (2-D) cell model that contains three circular membranes representing the plasma membrane (PM) and single bilayer approximations to both the nuclear envelope and the mitochondrial membrane. The first version uses a Cartesian transport network, which respects topology but approximates geometry. The second version uses a meshed transport network, which respects both. The asymptotic electroporation model is assigned to all local membrane sites in order to assess the electrical response of the membranes. The predictions of these two models are presented for 10-ns trapezoidal pulses with 1.5 ns rise and fall times. The applied field magnitudes range from 1 to 100 kV/cm, corresponding to recent experiments. The spatially distributed electroporation models exhibit a supraelectroporation for the larger pulses with a maximum transmembrane voltage of Um~1.5 V for both the PM and organelle membranes. For the larger fields, the PM and organelle membranes electroporate essentially simultaneously. The meshed version of the transport network eliminates numerical artifacts and is more computationally efficient View full abstract»

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IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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Editor-in-Chief
Steven J. Gitomer, Ph.D.
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Guest Scientist, Los Alamos National Laboratory
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