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Plasma Science, IEEE Transactions on

Issue 4  Part 1 • Date Aug 2002

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  • Nonthermal decontamination of biological media by atmospheric-pressure plasmas: review, analysis, and prospects

    Publication Year: 2002 , Page(s): 1409 - 1415
    Cited by:  Papers (235)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (455 KB)  

    Although the use of an electrical discharge to disinfect water was suggested and applied more than a hundred years ago, basic and applied research on the interaction of plasmas with biological media was extensively carried out only relatively recently. In this context, a review of various works on the germicidal effects of atmospheric pressure, "cold" plasmas, is presented. The nonequilibrium discharge devices discussed in this review, which have been used in biological applications by various investigators, are the corona discharge, the diffuse dielectric-barrier discharge, the resistive barrier discharge, and the atmospheric-pressure plasma jet. Analysis of the inactivation kinetics for various bacteria seeded in (or on) various media and exposed to the plasma generated by these devices, showed that three types of survivor curves exist, depending on the type of micro-organism, the type of medium, and the type of exposure (direct versus remote). Insights into the roles of UV radiation, active species, and charged particles has led to the conclusion that chemically reactive species, such as free radicals, play the most important role in the inactivation process. In addition, recent results suggesting that biomanipulation of the cells of micro-organisms with nonequilibrium plasmas is possible are highlighted. View full abstract»

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  • Reduction of Bacillus Subtilis and Aspergillus Niger spores using nonthermal atmospheric gas discharges

    Publication Year: 2002 , Page(s): 1416 - 1423
    Cited by:  Papers (25)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1620 KB) |  | HTML iconHTML  

    Nonthermal gas discharges at atmospheric pressure, such as dielectric barrier discharges are currently investigated for low-temperature packaging sterilization in order to reach the conditions required for aseptic food packaging. In particular, understanding the basic sterilization mechanisms and the enhancement of the main bacterial reduction pathways are the goals of our investigations. For this purpose, germ reduction experiments were carried out with Bacillus Subtilis and Aspergillus Niger spores using different gas mixtures and plasma conditions with the direct and the indirect influence of barrier discharges. In order to analyze the contribution of UV radiation during plasma germ deactivation, experiments with different excimer UV lamps, also driven by barrier discharges in special UV-emitting gas mixtures, have been carried out. Results of germ reduction experiments using barrier discharges and prospects for atmospheric discharge systems, suitable for industrial packaging sterilization, are presented in this paper. View full abstract»

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  • Bacterial decontamination of water by means of pulsed-corona discharges

    Publication Year: 2002 , Page(s): 1449 - 1453
    Cited by:  Papers (50)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (427 KB)  

    By using a tungsten wire with 75-μm diameter, 2 cm apart from a plane cathode, and applying a 600-ns, 120-kV square wave pulse, we were able to obtain a pulsed-water corona discharge (PWC). The effect of these discharges on bacteria was studied using water contaminated with Escherichia coli or Bacillus subtilis, the latter in both the vegetative and spore state. The strongest effect was obtained on E. coli. The concentration of E. coli could be reduced by three orders of magnitude after applying eight corona discharges to the water. The corresponding energy expenditure is 10 J/cm3. The decontamination rate had the largest values at the beginning, and decreased considerably after 15 electrical discharges, reaching a constant residual concentration value of 10-4 of the initial concentration. For B. subtilis in the vegetative state, it took almost 30 discharges to reach the same result, corresponding to an energy expenditure of 40 J/cm3. There was no effect on B. subtilis spores. Comparisons with the pulsed-electric field (PEF) method indicate that the decontamination efficiency of the PWC method is slightly higher than that of the PEF method. View full abstract»

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  • Special issue on the "nonthermal medical/biological applications of ionized gases and electromagnetic fields"

    Publication Year: 2002 , Page(s): 1398 - 1399
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB)  

    First Page of the Article
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  • The respective roles of UV photons and oxygen atoms in plasma sterilization at reduced gas pressure: the case of N2-O2 mixtures

    Publication Year: 2002 , Page(s): 1429 - 1436
    Cited by:  Papers (92)
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    In the reduced-pressure (≤10 torr) afterglow stemming from discharges in O2- containing mixtures such as N2-O2, the test-reference spores are ultimately inactivated by UV photons through destruction of their genetic material (DNA). To show this, we assume the inactivation to result from a sufficiently large number of successful hits of the DNA strands by UV photons. This implies that the higher the UV intensity, the shorter the time required to reach the lethal dose. Simultaneously, the increased erosion of the spores by the oxygen atoms as time elapses reduces the incident number of photons required to meet the lethal dose. Erosion, as observed by scanning electron microscopy, also increases with the O2 percentage in the mixture. Actually, sterilization time is found to be the shortest when the O2 percentage in the mixture is set to maximize the UV emission intensity, which occurs at O2 percentages typically below 2%, where erosion is low. This proves the predominant role of UV radiation over erosion as far as spore inactivation is concerned. In any case, plasma sterilization always implies some erosion of the test spores, in contrast to what happens with conventional sterilization methods. View full abstract»

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  • Filamentary, patterned, and diffuse barrier discharges

    Publication Year: 2002 , Page(s): 1400 - 1408
    Cited by:  Papers (218)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (722 KB) |  | HTML iconHTML  

    Barrier discharges, also known as dielectric-barrier discharges or silent discharges, provide a simple technology to establish nonequilibrium plasma conditions in atmospheric-pressure gases. This property has led to a number of industrial applications, including ozone generation, surface modification, pollution control, CO2 lasers, excimer lamps, and flat plasma-display panels. Depending on a variety of gas properties, operating parameters, and boundary conditions, the discharge can exhibit pronounced filamentary character, self-organized regular-discharge patterns, or completely diffuse appearance. The literature on these different types of barrier discharges is reviewed, and the underlying physical phenomena are discussed. Relative recent investigations on low-current density diffuse barrier discharges suggest novel applications of fairly "mild" plasmas for sterilization and disinfection purposes and utilizing their selective influence on biological cells. View full abstract»

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  • A review of electrocoupling mechanisms mediating facilitated wound healing

    Publication Year: 2002 , Page(s): 1504 - 1515
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB) |  | HTML iconHTML  

    The role of electrical interaction in wound healing has been recognized for nearly half of the last century. Based on the notion that wound healing may be facilitated by using electrical stimulation (referred to as electrotherapy), numerous animal model studies and clinical trials have been carried out to establish the effectiveness of electrotherapy. In spite of the concentrated effort, however, electrotherapy has not been approved by the U.S. FDA and remains poorly understood. Elucidation of the molecular and cellular mechanisms mediating facilitated wound healing is likely required, before rational electrotherapy can be devised and successfully implemented. Over the past six years, we have performed a series of in vitro experiments designed to identify the mechanisms mediating the cellular effects induced by exogenous application of electrical stimulation. The purpose of this review is to provide a description for such mechanisms (i.e., electrocoupling mechanisms) and to formulate an integrated model for these coupling mechanisms. View full abstract»

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  • Simulations of electroporation dynamics and shape deformations in biological cells subjected to high voltage pulses

    Publication Year: 2002 , Page(s): 1536 - 1546
    Cited by:  Papers (15)
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    The temporal dynamics of electroporation of cells subjected to ultrashort voltage pulses are studied based on a coupled scheme involving the Laplace, Nernst-Planck, and Smoluchowski equations. It is shown that a finite time delay exists in pore formation, and leads to a transient overshoot of the transmembrane potential Vmem beyond 1.0 V. Pore resealing is shown to consist of an initial fast process, a 10-4 second delay, followed by a much slower closing at a time constant of about 10-1 s. This establishes a time window for effective killing by a second pulse. The results are amply supported by our experimental data for E.-coli cells, and the time constant also matches experiments. An electromechanical analysis for analyzing cell shape changes is also presented. Our calculations show that at large fields, the spherical cell geometry can be significantly modified, and even ellipsoidal forms would be inappropriate to describe the deformation. Values of surface forces obtained are in very good agreement with the 1-10-nN/m range reported for membrane rupture. It is also demonstrated that, at least for the smaller electric fields, both the cellular surface area and volume change roughly in a quadratic manner with electric field. Finally, it is shown that the bending moments are generally quite small and can be neglected for a simpler analysis. View full abstract»

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  • A study on biological effects of low-intensity millimeter waves

    Publication Year: 2002 , Page(s): 1489 - 1496
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (745 KB) |  | HTML iconHTML  

    Resonance-like biological effects of millimeter-wave radiation at frequencies of approximately 42 GHz on the growth rate of E. coli and on DNA have been reported in several scientific publications. In order to explore these nonthermal effects, we have measured the growth rate and the absorption spectrum of E. coli, irradiated by millimeter waves in the frequency range from 41 to 43 GHz. In addition, the effect of this radiation on DNA was studied by measuring plasmid transformation efficiency. Both the growth rate variations with varying frequency and the variations in the result of the plasmid transformation efficiency experiments were found to be statistically insignificant. Resonance-like absorption features observed in the absorption spectrum of E. coli were identified as modes generated in the millimeter-wave system, when the sample was inserted. The experimental results indicate that resonance effects are unlikely in this particular frequency range. View full abstract»

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  • Low-frequency electromagnetic fields evoke the stress response: mechanism of interaction with DNA and biomedical applications

    Publication Year: 2002 , Page(s): 1497 - 1500
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (201 KB) |  | HTML iconHTML  

    Low-frequency electromagnetic (EM) fields react with many cellular systems. One important interaction is the stress response, a protective mechanism in reaction to potentially harmful stimuli in the environment. The stress response is characterized by the synthesis of stress proteins, a complex process that requires activation of DNA. Induction of this response by EM fields may be initiated by direct interaction of the fields with moving electrons in DNA. This mechanism is physically reasonable, and interactions between EM fields and electron transfer have been shown to occur in several simpler molecular systems. Additional support for the idea of direct interaction of EM fields with DNA is identification of a specific DNA sequence that can promote an EM-field response when it is normally present or artificially introduced. The protective stress response and the EM-field-specific DNA sequence lend themselves to biomedical applications in cardiac surgery and gene therapy. View full abstract»

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  • Comparison of the effectiveness of biphase and monophase rectangular pulses for the inactivation of micro-organisms using pulsed electric fields

    Publication Year: 2002 , Page(s): 1525 - 1531
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (683 KB) |  | HTML iconHTML  

    The use of pulsed electric fields (PEF) for the inactivation of micro-organisms is currently of considerable interest as an alternative method to the conventional thermal methods of food pasteurization presently in widespread use. Many parameters of PEF influence the effectiveness of inactivation, one of which is the pulse profile, which is the subject of the present study. In this study, a pulse-forming network was designed and constructed to allow direct comparison of the effectiveness of a rectangular "monophase" pulse (single polarity) with a rectangular "biphase" pulse (incorporating a rapid reversal of polarity for the second half of the pulse). The pulses of 30 kV/cm in electric field intensity, 2 μs in duration for monophase, and 1 μs for each phase for biphase, were applied to parallel-plate test cells. Three different species of bacteria were tested including Gram negative and positive cell types. The bacteria were suspended in peptone water solutions of varied peptone concentration and hence, conductivity. The results show that, contrary to previous findings, biphase pulsing did not provide superior inactivation levels compared with monophase pulsing, for all three bacteria tested. Increasing the conductivity of the suspension fluid produced a general trend toward similar levels of inactivation of biphase compared with monophase PEF treatment, but in no case was it found that biphase PEF treatment was superior to monophase PEF treatment. View full abstract»

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  • Features of sterilization using low-pressure DC-discharge hydrogen-peroxide plasma

    Publication Year: 2002 , Page(s): 1440 - 1444
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB) |  | HTML iconHTML  

    This investigation studies the theoretical and practical features of sterilization using glow discharge plasma in hydrogen-peroxide vapor. It is determined that in such a system, most sterilization is performed by the active species formed in the plasma rather than by ultraviolet radiation (as is the case in air or oxygen discharges). This study shows that sterilization by discharge plasma in hydrogen-peroxide vapor is more efficient than sterilization by other gas discharges: sterilization time is two to three times shorter in open surfaces and ten times shorter in packed articles. This study's calculations indicate that this enhanced efficiency might be due to fact that concentrations of the main biologically active particles, such as atomic oxygen and oxygen molecules excited to lower metastable states, reach values of ∼1014-1015 cm-3, which is two to three orders of magnitude higher than that in oxygen plasma at the same parameters of the discharge. View full abstract»

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  • The technology and execution of plasmachemical disinfection of hazardous medical waste

    Publication Year: 2002 , Page(s): 1445 - 1448
    Cited by:  Papers (6)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (497 KB) |  | HTML iconHTML  

    This report describes the technology used for plasma-chemical disinfection of hazardous medical waste (HMW), which employs high-temperature mineralization. This method uses low-temperature plasma produced in a plasma generator as an additional source of heat energy. The method not only neutralizes medical waste, but it also reduces by 50-400 times the volume of waste being buried. The waste-combustion process includes the following stages: two-stage combustion in the furnace at a temperature of 1000°C-1200°C and in the afterburning chamber at a temperature of 1200°C-1300°C, with dwell time of flue gases no less than 2 s; obligatory quenching (fast cooling) of flue gases; multistage cleaning of flue gases of fly ash, vapors of heavy metals, acid gases, and, if necessary, dioxins and furans; automated control of mode parameters, ejection into the atmosphere and control of all technological processes; low-consumption factors on energy and used reagents. The installation is designed for treatment of 150 kg/h of HMW and it employs a rotary kiln with parallel-current flow of burned waste and incandescent gases for plasma combustion of the waste. This allows the burning waste to be constantly mixed, which prevents fusion or baking into layers, and thus intensifies the processes of heat and mass exchange. Waste is supplied into the furnace periodically through the system of trays using pneumatic pushers. Two plasma generators are mounted on the loading end of the furnace, and one is mounted on the afterburning chamber. Slag is unloaded from the furnace by quenching it with water. After quenching, cooling, and discharging the slag, it is disposed of. The gas cleaning system consists of a Venturi scrubber, a packed-bed scrubber, a demister, and an absorber. This technological process solves several problems involved in collecting, packing, and disposing of HMW by automating the loading processes, organizing combustion regimes, and cleaning flue gases. View full abstract»

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  • A numerical analysis of pulsed current-density distribution inside tissues under medical treatment

    Publication Year: 2002 , Page(s): 1532 - 1535
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    This paper uses a simplified numerical two-dimensional model to calculate the low-frequency current-density distribution in the horizontal thorax section of the human body. The model considers the application of two electrodes on the spinal surface where neurological disease is under treatment. The report provides data for the numerical model, the simulation procedure, and the graphs of the current distribution in the normalized view along the main control lines of the model. The simulation results suggest a possibility of observing current flow through vitally important organs (like the heart) with a similar density to that through the tissue being treated. View full abstract»

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  • Decontamination of water by excimer UV radiation

    Publication Year: 2002 , Page(s): 1501 - 1503
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB) |  | HTML iconHTML  

    Water is one of the most important substances on which life depends. However, water may also serve as a medium by which disease is spread to humans, animals, and plants. Therefore, the biological decontamination of this vital substance is of paramount importance. Several methods have been used to decontaminate water and assure its clean supply. Unfortunately, most of these methods use potentially hazardous chemicals, which require proper storage and transport and are not environmentally friendly. Here we present a decontamination method based on the use of UV radiation emitted by the decay of excimers generated by a nonequilibrium discharge operating in the high-pressure regime. We found that at an appropriate wavelength, this type of UV radiation has a devastating effect on micro-organisms. View full abstract»

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  • Sterilization of dental bacteria in a flowing N2-O2 postdischarge reactor

    Publication Year: 2002 , Page(s): 1437 - 1439
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    Destruction processes of several dental bacteria have been analyzed in a flowing postdischarge reactor. An N2-5%O2 gas mixture has been chosen to produce a high quantity of oxygen atoms and a UV emission intensity of NOβ bands in the whole reactor chamber. The first results obtained with Streptococcus mutans (Sm), Porphyromonas gingivalis (Pg), Fusobacterium nucleatum (Fn), Prevotella intermedia (Pi), and Escherichia coli (E. Coli) dental bacteria at initial concentrations from 106-1010 colony forming unit per milliliter (CFU/ml) introduced in small cylindrical Al substrates (previously sterilized) are reported. A full destruction of Sm, Pg, and Pi bacteria was obtained after 15-20 min and of Fn after 30 min of treatment. However, the E. coli bacteria, introduced to 1010 CFU/ml was still not destroyed after a treatment time of 30 min. View full abstract»

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  • Mapping membrane-potential perturbations of chromaffin cells exposed to electric fields

    Publication Year: 2002 , Page(s): 1516 - 1524
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB)  

    The numerous and diverse responses of biological systems to electric fields continue to evoke interest in elucidating the fundamental mechanisms of cellular interactions with these fields. In order to address this issue for excitable cells, responses of bovine adrenal chromaffin cells exposed to DC electric fields in various orientations were investigated. Spatial variations in membrane potential were monitored in single cells as well as in complex clusters of cells using fluorescence video imaging and a voltage-sensitive dye, di-8-ANEPPS. Responses in isolated cells were in general agreement with that predicted by theory. Reversal of the electric field direction did not produce an exactly symmetrical reversal of fluorescent intensities, suggesting structural asymmetries within the cells. Clusters larger than a single cell exhibited more complex responses at the interfaces between cells that were dependent on the orientation of the regions of contact with the electric-field direction. Taken as a whole, the results of this study provide a foundation to understand the interaction of electric fields at the level of tissues and organs. View full abstract»

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  • Destruction of Bacillus Subtilis cells using an atmospheric-pressure capillary plasma electrode discharge

    Publication Year: 2002 , Page(s): 1424 - 1428
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (209 KB) |  | HTML iconHTML  

    We report the results of experiments aimed at the investigation of the destruction of spore-forming bacteria, which are believed to be among the most resistant micro-organisms, using a novel atmospheric-pressure capillary plasma electrode discharge plasma. Various well-characterized cultures of Bacillus Subtilis were prepared, subjected to atmospheric-pressure plasma jets emanating from a plasma-shower reactor operated either in He or in air (N2/O2 mixture) at various power levels and exposure times, and analyzed after plasma treatment. Reductions in colony-forming units ranged from 104 (He plasma) to 108 (air plasma) for plasma exposure times of less than 10 min. View full abstract»

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  • Processing of sugar beets with pulsed-electric fields

    Publication Year: 2002 , Page(s): 1547 - 1551
    Cited by:  Papers (13)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB) |  | HTML iconHTML  

    The treatment of biological cells with strong pulsed-electric fields can lead to irreversible formation of large pores in the cell membrane and thus destroy the cell and give access to its content. This well-known process of electroporation has been successfully applied to the inactivation of bacteria in many laboratories. However, few efforts have been made to utilize the technique on a large industrial scale for the production of nourishment from food plants. We have built the mobile test device Karlsruher Elektroporations Anlage (KEA), which consists of a 300-kV Marx generator operating at 10 Hz and delivering its pulses to a cylindrical reaction chamber with axially and azimuthally distributed electrodes. The reaction chamber has a large cross section, sufficient for the treatment of entire sugar beets in a continuous stream. KEA has been used in an experimental campaign to demonstrate the advantages of electric pulse treatment for the production of sugar from beets compared with conventional techniques. Although the process has not yet been optimized, it was found that appreciable energy savings are possible since the treated beets could be extracted at much lower temperatures with the same result. To demonstrate the technical and economic feasibility on a large scale, we plan to build a pilot plant with a throughput of several tens of tons per hour and to use it in the next seasonal campaign. Although the results are convincing, important details of the effect are not yet understood. In particular, the interaction between the cell membrane and the cell wall in the plant organism under the action of the electric field needs further investigation. Therefore, we also plan to establish a basic research program. View full abstract»

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  • "On the ionization of air for removal of noxious effluvia" (Air ionization of indoor environments for control of volatile and particulate contaminants with nonthermal plasmas generated by dielectric-barrier discharge)

    Publication Year: 2002 , Page(s): 1471 - 1481
    Cited by:  Papers (14)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (439 KB) |  | HTML iconHTML  

    Recent developments in the application of controllable air ionization processes that apply dielectric-barrier discharge devices to generate nonthermal plasmas have led to applications for chemical and biological decontamination in indoor air environments. These include significant reductions in airborne microbials, neutralization of odors, and reductions of specific volatile organic compounds (VOCs). Removal of very fine particulates (PMx) is also is enhanced by air ionization. The process of air ionization involves the electronically induced formation of small air ions, including reactive oxygen species, such as superoxide O2·-, the diatomic oxygen radical anion, which react rapidly with airborne VOC and PMx. The physics and chemistry of air ionization, and its utility for contributing to significant improvements in indoor air quality are discussed. View full abstract»

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  • Directed killing of anthrax spores by microwave-induced cavitation

    Publication Year: 2002 , Page(s): 1482 - 1488
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    High-power pulsed-microwave radiation damages anthrax spores by apparent sonoluminescence in aqueous solutions containing the organic semiconductor diazoluminomelanin (DALM). DALM biosynthesized by JM109 E. coli, containing the plasmid pIC2ORNR1.1, had a higher affinity for spores of Sterne strain anthrax when compared to several other species of bacilli and enhanced the effect. Upon exposure to pulsed-microwave radiation, anthrax spores showed a maximum of 4 to 5 (i.e., 4.6) logs of kill. The light emitted was typical of plasma gas emissions and the spores, upon scanning electron-microscopic examination, showed enlargement and rupture typical of rapid expansion. Therefore, microwave-induced cavitations localized to the spore surfaces enhanced kill. View full abstract»

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  • Chemical warfare agent decontamination studies in the plasma decon chamber

    Publication Year: 2002 , Page(s): 1460 - 1470
    Cited by:  Papers (21)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB) |  | HTML iconHTML  

    A "plasma decon chamber" has been developed at Los Alamos National Laboratory (LANL), Albuquerque, NM, to study the decontamination of chemical and biological warfare agents. This technology is targeted at sensitive electronic equipment for which there is currently no acceptable, nondestructive means of decontamination. Chemical reactivity is provided by a downstream flux of reactive radicals such as atomic oxygen and atomic hydrogen, produced in a capacitively coupled plasma. In addition, the decon chamber provides an environment that accelerates the evaporation of chemical agents from contaminated surfaces by vacuum, heat, and forced convection. Once evaporated, agents and agent byproducts are recirculated directly through the plasma, where they undergo further chemical breakdown. Preliminary studies on actual chemical agents were conducted at the U.S. Army Dugway Proving Ground, Dugway, UT. Exposures were conducted at a system pressure of 30 torr, exposure temperature of 70°C, plasma-to-sample standoff distance of 10 cm, and 10% addition of oxygen or hydrogen to a helium balance. This exposure condition was based on optimization studies conducted at LANL on agent simulants. The agents studied were VX and soman (GD) nerve agents and sulfur mustard (HD) blister agent, as well as a thickened simulant. All agents were decontaminated off aluminum substrates to below the detection limit of ∼0.1% of the initial contamination level of approximately 1 mg/cm2. For VX, this level of decontamination was achieved in 8-16 min of exposure, while only 2 min were required for the more volatile HD and GD. Evaporation and subsequent gas-phase chemical breakdown in the plasma appears to be the dominant decontamination mechanism for all of the agents. However, an observed difference in the decontamination process between oxygen and hydrogen indicates that chemical reactivity in the liquid phase also plays an important role. View full abstract»

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  • Surface decontamination of simulated chemical warfare agents using a nonequilibrium plasma with off-gas monitoring

    Publication Year: 2002 , Page(s): 1454 - 1459
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB) |  | HTML iconHTML  

    InnovaTek, Inc., Richland, WA, is developing a surface decontamination technology that utilizes active species generated in a nonequilibrium corona plasma. The plasma technology was tested against dimethyl-methyl phosphonate (DMMP), a simulant for the chemical agent Sarin. Gas chromatograph mass spectrometry analysis showed that a greater than four log10 destruction of the DMMP on an aluminum surface was achieved in a 10-min treatment. An ion-trap mass spectrometer was utilized to collect time-resolved data on the treatment off-gases. These data indicate that only nontoxic fragments of the broken down DMMP molecule were present in the gas phase. The technology is being further refined to develop a product that will not only decontaminate surfaces but that will also sense when decontamination is complete. View full abstract»

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  • Anticancer activity by magnetic fields: inhibition of metastatic spread and growth in a breast cancer model

    Publication Year: 2002 , Page(s): 1552 - 1557
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (409 KB) |  | HTML iconHTML  

    The possibility that magnetic fields (MFs) induce anticancer activity in vivo has been investigated by using a highly metastatic human cancer model transplanted in immunoincompetent mice (CD-1, nu-nu). The nude mice, bearing a subcutaneous human breast tumor (MDA-MB-435), were exposed for 70 min daily, for six consecutive weeks, to modulated MF (static with a superimposition of extremely low-frequency fields at 50 Hz) having a time-average total intensity of 5.5 mT. A positive control group was treated with a chemotherapeutic agent (cyclophosphamide). Neither MF nor cyclophosphamide significantly reduced the total number of pulmonary metastases. Both treatments induced a significant inhibition on spread and growth of intermediate (10-100 cells) and large (>100 cells) lung metastases compared with the MF sham-treatment. The inhibition induced by the MF was significantly greater than that observed in mice treated with cyclophosphamide. Gross pathology at necroscopy, hematoclinical/hematological, and histological examination did not show any toxic or abnormal effects. These findings support a potential use of MF as an anticancer agent. 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.
Senior Scientist, US Civilian Research & Development Foundation
Guest Scientist, Los Alamos National Laboratory
1428 Miracerros Loop South
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