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1

Gas plasma sterilization of microorganisms and mechanisms of action  

PubMed Central

The use of true gas plasmas for the inactivation of microorganisms is an area of dynamic research. Many types of gases are used as a source of plasma, and different plasma production methods have been applied. The antimicrobial mechanisms of oxygen-based gas plasmas may be due to an etching effect on microbial structures, particularly bacterial endospores resulting in shrinkage. By contrast, the definite mechanisms of actions of other gas plasma sources, such as N2, He, Ne, Ar and Xe gases, have not been clearly defined and indeed may be distinct. The speculated mechanisms of these gas plasmas involve the direct attack of metastable (excited molecular), UV and/or VUV to microbial structures, specifically the inner membrane and DNA in the core of bacterial endospores. According to this speculation, sterilized spore figures would remain unchanged. However, these mechanisms remain to be clarified. Future perspectives on the use of gas plasma for sterilization are of interest, as it is possible that appropriate sterility assurance levels can be obtained in parallel with material and functional compatibility. Traditional sterilization methods are often limited in these requirements. Therefore, gas plasma sterilization may prove to be an appropriate alternative sterilization procedure. PMID:22993596

SHINTANI, HIDEHARU; SAKUDO, AKIKAZU; BURKE, PETER; McDONNELL, GERALD

2010-01-01

2

Assessment of the efficacy of a low temperature hydrogen peroxide gas plasma sterilization system  

Microsoft Academic Search

The STERRAD 100 sterilization system (Johnson & Johnson Medical Ltd) uses low temperature hydrogen peroxide gas plasma for sterilization of heat labile equipment. The efficacy of the machine was tested by contaminating a standard set of instruments with different organisms and using a filtration method to assess recovery of organisms from the wash fluids of instruments post-sterilization. Experiments were performed

M. S. Kyi; J. Holton; G. L. Ridgway

1995-01-01

3

Apparatus Circulates Sterilizing Gas  

NASA Technical Reports Server (NTRS)

Apparatus circulates sterilizing gas containing ethylene oxide and chlorofluorocarbon through laboratory or medical equipment. Confines sterilizing gas, circulating it only through parts to be treated. Consists of two units. One delivers ethylene oxide/chlorofluorocarbon gas mixture and removes gas after treatment. Other warms, humidifies, and circulates gas through equipment to be treated. Process provides reliable sterilization with negligible residual toxicity from ethylene oxide. Particularly suitable for sterilization of interiors of bioreactors, heart/lung machines, dialyzers, or other equipment including complicated tubing.

Cross, John H.; Schwarz, Ray P.

1991-01-01

4

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

PubMed

The mechanism of action on biomolecules of N? gas plasma, a novel sterilization technique, remains unclear. Here, the effect of N? gas plasma on protein structure was investigated. BSA, which was used as the model protein, was exposed to N? gas plasma generated by short-time high voltage pulses from a static induction thyristor power supply. N? 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 protein's secondary structure. When the amide I region was analyzed in the infrared spectra according to curve fitting and Fourier self-deconvolution, N? gas plasma-treated BSA showed increased ?-helix and decreased ?-turn content. Because heating decreased ?-helix and increased ?-sheet content, the structural changes induced by N? gas plasma-treatment of BSA were not caused by high temperatures. Thus, the present results suggest that conformational changes induced by N? gas plasma are mediated by mechanisms distinct from heat denaturation. PMID:23617321

Sakudo, Akikazu; Higa, Masato; Maeda, Kojiro; Shimizu, Naohiro; Imanishi, Yuichiro; Shintani, Hideharu

2013-07-01

5

Experimental study on a new sterilization process using plasma source ion implantation with N2 gas  

NASA Astrophysics Data System (ADS)

Plasma source ion implantation (PSII) with negative high voltage pulses has been applied to the sterilization process as a technique suitable for sterilization of three-dimensional work pieces. Pulsed high negative voltage (0-10 ?s pulse width, 900 pulses/s, -9 to -16 kV) was applied to the electrode in this process at a gas pressure of 2-7 Pa of N2. This process has been found to be capable of generating glow discharge plasma around a stainless electrode, on which quartz glass samples with biological materials are placed. We found that the PSII process reduced the numbers of active Bacillus pumilus cells using N2 gas plasma generated by pulsed dc voltages. The number of bacteria survivors was reduced by 105×with 5-10 min exposure. The state of cells on quartz glass was observed by scanning electron microscopy with and without exposure. We found that the ion energy is the most important processing parameter. The technique is demonstrated to be an effective means of low-temperature surface sterilization, with very little damage to the target.

Yoshida, M.; Tanaka, T.; Watanabe, S.; Takagi, T.; Shinohara, M.; Fujii, S.

2003-07-01

6

In vitro effect of multiple hydrogen peroxide gas plasma sterilizations on the rate of closure of ameroid constrictors.  

PubMed

Objective-To evaluate the effect of multiple hydrogen peroxide gas plasma (HPGP) sterilizations on the rate of closure of ameroid constrictors. Sample-Thirty-six 5.0-mm ameroid constrictors. Procedures-Ameroid constrictors were randomly allocated to 6 groups. Each group underwent 1, 2, 3, 4, 5, or 6 HPGP sterilizations. Ameroid constrictors were then incubated for 35 days in canine plasma and digitally imaged at predetermined times during incubation. One individual, who was unaware of the group to which each ameroid constrictor was assigned, measured the lumen area of the constrictor on each digital image. Mean lumen area was compared among groups. Results-No ameroid constrictors were completely closed after 35 days of incubation in canine plasma. Mean lumen area after incubation did not differ among constrictors that underwent 1, 2, and 3 sterilizations. Constrictors that underwent 4 sterilizations were closed significantly more than were those that underwent 1, 2, or 3 sterilizations. Mean lumen area after incubation did not differ significantly between constrictors that underwent 5 and 6 sterilizations, although the final lumen areas for those constrictors were significantly smaller than those for constrictors that underwent 1, 2, 3, and 4 sterilizations. Conclusions and Clinical Relevance-Ameroid constrictors that underwent 5 and 6 HPGP sterilizations had a 9% to 12% decrease in lumen area, compared with that of constrictors that underwent ? 4 plasma sterilizations, and the use of such constrictors could increase the risk of portal hypertension and secondary acquired shunting or decrease the risk of persistent shunting. PMID:25255183

Thompson, Elizabeth M; Towle Millard, Heather A; Moore, George E; Guptill, Lynn

2014-10-01

7

Effects of Low-Temperature Hydrogen Peroxide Gas Plasma Sterilization on In Vitro Cytotoxicity of Poly(?-Caprolactone) (PCL).  

PubMed

Our objective was to determine whether low-temperature hydrogen peroxide (H(2)O(2)) gas plasma sterilization of porous three-dimensional poly(?-caprolactone) (PCL) constructs significantly inhibits cellular metabolism of canine chondrocytes. Porous cylindrical constructs were fabricated using fused deposition modeling and divided into four sterilization groups. Two groups were sterilized with low-temperature H(2)O(2) gas plasma (LTGP) and constructs from one of those groups were subsequently rinsed with Dulbecco's Modified Essential Media (LTGPDM). Constructs in the other two groups were disinfected with either 70% isopropyl alcohol or exposure to UV light. Canine chondrocytes were seeded in 6-well tissue-culture plates and allowed to adhere prior to addition of PCL. Cellular metabolism was assessed by adding resazurin to the tissue-culture wells and assessing conversion of this substrate by viable cells to the fluorescent die resorufin. This process was performed at three times prior to addition of PCL and at four times after addition of PCL to the tissue-culture wells. Metabolism was not significantly different among the different tissue-culture wells at any of the 3 times prior to addition of PCL. Metabolism was significantly different among the treatment groups at 3 of 4 times after addition of PCL to the tissue culture wells. Metabolism was significantly lower with constructs sterilized by LTGP than all other treatment groups at all 3 of these times. We conclude that LTGP sterilization of PCL constructs resulted in significant cytotoxicity to canine chondrocytes when compared to PCL constructs disinfected with either UV light exposure or 70% isopropyl alcohol. PMID:22126862

Franklin, Samuel Patrick; Stoker, Aaron M; Cockrell, Mary K; Pfeiffer, Ferris M; Bal, B Sonny; Cook, James L

2011-11-25

8

Plasma sterilization using the RF glow discharge  

NASA Astrophysics Data System (ADS)

In the present work, glow discharge oxygen plasma was used to sterilize the Pseudomonas aeruginosa on the polyethylene terephthalate (PET) sheets. In a self-designed plasma reaction equipment, active species (electron, ion, radical, UV light, etc.) were separated effectively, and the discharge area, afterglow area and remote area were plotted out in the plasma field. Before and after plasma treatment the cell morphology was studied by scanning electron microscopy (SEM). The results showed that after treatment of 30 s the germicidal effect is 4.26, 3. 84, 2.61, respectively in the three areas on the following conditions: discharge power was 40 W and gas flux was 20 cm 3/min. SEM results revealed the cell morphology before and after plasma treatment. The walls or cell membrane cracking was testified by determining the content of protein using coomassie light blue technique. The results from electron spin resonance spectroscopy (ESR) and double Langmuir electron probe showed that electron, ion and oxygen free radical played important roles in sterilization in the discharge area, but only oxygen radicals acted to sterilize the bacteria in the afterglow area and the remote area.

Yang, Liqing; Chen, Jierong; Gao, Junling; Guo, Yafei

2009-08-01

9

Sterilization effects of atmospheric cold plasma brush  

SciTech Connect

This study investigated the sterilization effects of a brush-shaped plasma created at one atmospheric pressure. A population of 1.0x10{sup 4}-1.0x10{sup 5} Escherichia coli or Micrococcus luteus bacteria was seeded in filter paper media and then subjected to Ar and/or Ar+O{sub 2} plasmas. A complete kill of the Micrococcus luteus required about 3 min argon plasma exposures. With oxygen addition into the argon plasma gas streams, a complete kill of the bacteria needed only less than 1 min plasma exposure for Micrococcus luteus and about 2 min exposure for Escherichia coli. The plasma treatment effects on the different bacteria cell structures were examined using scanning electron microscopy.

Yu, Q.S.; Huang, C.; Hsieh, F.-H.; Huff, H.; Duan Yixiang [Center for Surface Science and Plasma Technology, and Department of Chemical Engineering, University of Missouri-Columbia, Columbia, Missouri 65211 (United States); Department of Biological Engineering, University of Missouri-Columbia, Columbia, Missouri 65211 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2006-01-02

10

Plasma Sterilization: Opportunities and Microbial Assessment Strategies in Medical Device Manufacturing  

Microsoft Academic Search

Non-thermal gas discharge plasmas have significant potential as novel sterilization\\/decontamination agents in medical device manufacturing, and such agents may well be accepted by regulatory agencies. A number of aspects of plasma technology are currently under active investigation by many institutions and companies in order to obtain a thorough understanding of plasma sterilization as an alternative to conventional sterilization methods for

Ozlem Yardimci; Peter Setlow

2010-01-01

11

Sterilization of Cotton Fabrics Using Plasma Treatment  

NASA Astrophysics Data System (ADS)

Microbial contamination induces surface deformations and strength degradation of cotton fabrics by invading deeply into the fibers. In this study, the sterilization effects of low pressure plasmas on bacteria-inoculated cotton fabrics were investigated. Oxygen plasma treatment completely sterilized the cotton fabrics inoculated with various concentrations of staphylococcus aureus. Also, the influence of plasma treatment on physical properties of fabrics was examined. It was found that the plasma treatment did not affect ultimate tensile strength and surface morphology of the fabrics because it took advantage of relatively low plasma temperature.

Shahidi, S.; Ghoranneviss, M.

2013-10-01

12

21 CFR 880.6860 - Ethylene oxide gas sterilizer.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Ethylene oxide gas sterilizer. 880.6860...Miscellaneous Devices § 880.6860 Ethylene oxide gas sterilizer. (a) Identification. An ethylene gas sterilizer is a nonportable...

2010-04-01

13

Atmospheric-pressure plasma decontamination/sterilization chamber  

DOEpatents

An atmospheric-pressure plasma decontamination/sterilization chamber is described. The apparatus is useful for decontaminating sensitive equipment and materials, such as electronics, optics and national treasures, which have been contaminated with chemical and/or biological warfare agents, such as anthrax, mustard blistering agent, VX nerve gas, and the like. There is currently no acceptable procedure for decontaminating such equipment. The apparatus may also be used for sterilization in the medical and food industries. Items to be decontaminated or sterilized are supported inside the chamber. Reactive gases containing atomic and metastable oxygen species are generated by an atmospheric-pressure plasma discharge in a He/O.sub.2 mixture and directed into the region of these items resulting in chemical reaction between the reactive species and organic substances. This reaction typically kills and/or neutralizes the contamination without damaging most equipment and materials. The plasma gases are recirculated through a closed-loop system to minimize the loss of helium and the possibility of escape of aerosolized harmful substances.

Herrmann, Hans W. (Los Alamos, NM); Selwyn, Gary S. (Los Alamos, NM)

2001-01-01

14

Cold atmospheric plasma sterilization: from bacteria to biomolecules  

NASA Astrophysics Data System (ADS)

Although ionized gases have been known to have biological effects for more than 100 years, their impact on the practice in healthcare service became very significant only recently. Today, plasma-based surgical tools are used for tissue reduction and blood coagulation as surgical procedures. Most significant however is the speed at which low-temperature gas plasmas are finding new applications in medicine and biology, including plasma sterilization, wound healing, and cancer therapies just to name a few. In the terminology of biotechnology, the ``pipeline'' is long and exciting. This presentation reviews the current status of the field with a particular emphasis on plasma inactivation of microorganisms and biomolecules, for which comprehensive scientific evidence has been obtained. Some of the early speculations of biocidal plasma species are now being confirmed through a combination of optical emission spectroscopy, laser-induced fluorescence, mass spectrometry, fluid simulation and biological sensing with mutated bacteria. Similarly, fundamental studies are being performed to examine cell components targeted by gas plasmas, from membrane, through lipid and membrane proteins, to DNA. Scientific challenge is significant, as the usual complexity of plasma dynamics and plasma chemistry is compounded by the added complication that cells are live and constantly evolving. Nevertheless, the current understanding of plasma inactivation currently provides strong momentum for plasma decontamination technologies to be realized in healthcare. We will discuss the issue of protein and tissue contaminations of surgical instruments and how cold atmospheric plasmas may be used to degrade and reduce their surface load. In the context of plasma interaction with biomolecules, we will consider recent data of plasma degradation of adhesion proteins of melanoma cells. These adhesion proteins are important for cancer cell migration and spread. If low-temperature plasmas could be used to degrade them, it could form a control strategy for cancer spread. This adds to the option of plasma-triggered programmed cell death (apoptosis). Whilst opportunities thus highlighted are significant and exciting, the underpinning science poses many open questions. The presentation will then discuss main requirements for plasma sources appropriate for their biomedical applications, in terms of the scope of up-scaling, the ability to treat uneven surfaces of varying materials, the range of plasma chemistry, and the control of plasma instabilities. Finally a perspective will be offered, in terms of both opportunities and challenges.

Kong, Michael

2009-10-01

15

Sterilization of Turmeric by Atmospheric Pressure Dielectric Barrier Discharge Plasma  

NASA Astrophysics Data System (ADS)

In this study atmospheric pressure dielectric barrier discharge (DBD) plasma has been employed for sterilizing dry turmeric powders. A 6 kV, 6 kHz frequency generator was used to generate plasma with Ar, Ar/O2, He, and He/O2 gases between the 5 mm gap of two quartz covered electrodes. The complete sterilization time of samples due to plasma treatment was measured. The most important contaminant of turmeric is bacillus subtilis. The results show that the shortest sterilization time of 15 min is achieved by exposing the samples to Ar/O2 plasma. Survival curves of samples are exponential functions of time and the addition of oxygen to plasma leads to a significant increase of the absolute value of time constant of the curves. Magnitudes of protein and DNA in treated samples were increased to a similar value for all samples. Taste, color, and solubility of samples were not changed after the plasma treatment.

Setareh, Salarieh; Davoud, Dorranian

2013-11-01

16

Simultaneous Sterilization With Surface Modification Of Plastic Bottle By Plasma-Based Ion Implantation  

NASA Astrophysics Data System (ADS)

Dry sterilization of polymeric material is developed. The technique utilizes the plasma-based ion implantation which is same as for surface modification of polymers. Experimental data for sterilization are obtained by using spores of Bacillus subtilis as samples. On the other hand we previously showed that the surface modification enhanced the gas barrier characteristics of plastic bottles. Comparing the implantation conditions for the sterilization experiment with those for the surface modification, we find that both sterilization and surface modification are simultaneously performed in a certain range of implantation conditions. This implies that the present bottling system for plastic vessels will be simplified and streamlined by excluding the toxic peroxide water that has been used in the traditional sterilization processes.

Sakudo, N.; Ikenaga, N.; Ikeda, F.; Nakayama, Y.; Kishi, Y.; Yajima, Z.

2011-01-01

17

Simultaneous Sterilization With Surface Modification Of Plastic Bottle By Plasma-Based Ion Implantation  

SciTech Connect

Dry sterilization of polymeric material is developed. The technique utilizes the plasma-based ion implantation which is same as for surface modification of polymers. Experimental data for sterilization are obtained by using spores of Bacillus subtilis as samples. On the other hand we previously showed that the surface modification enhanced the gas barrier characteristics of plastic bottles. Comparing the implantation conditions for the sterilization experiment with those for the surface modification, we find that both sterilization and surface modification are simultaneously performed in a certain range of implantation conditions. This implies that the present bottling system for plastic vessels will be simplified and streamlined by excluding the toxic peroxide water that has been used in the traditional sterilization processes.

Sakudo, N.; Ikenaga, N.; Ikeda, F.; Nakayama, Y.; Kishi, Y.; Yajima, Z. [Kanazawa Institute of Technology, 3-1 Yatsukaho, Hakusan, Ishikawa 924-0838 (Japan)

2011-01-07

18

High-speed sterilization technique using dielectric barrier discharge plasmas in atmospheric humid air  

NASA Astrophysics Data System (ADS)

The inactivation of Bacillus atrophaeus spores by a dielectric barrier discharge (DBD) plasma produced by an ac voltage application of 1 kHz in atmospheric humid air was investigated in order to develop low-temperature, low-cost and high-speed plasma sterilization technique. The biological indicators covered with a Tyvek sheet were set just outside the DBD plasma region, where the air temperature and humidity as a discharge gas were precisely controlled by an environmental test chamber. The results show that the inactivation of Bacillus atrophaeus spores was found to be dependent strongly on the humidity, and was completed within 15 min at a relative humidity of 90 % and a temperature of 30 C. The treatment time for sterilization is shorter than those of conventional sterilization methods using ethylene oxide gas and dry heat treatment. It is considered that reactive species such as hydroxyl radicals that are effective for the inactivation of Bacillus atrophaeus spores could be produced by the DBD plasma in the humid air. Repetitive micro-pulsed discharge plasmas in the humid air will be applied for the sterilization experiment to enhance the sterilization efficiency.

Miyamae, M.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

2010-11-01

19

Permeation barrier coating and plasma sterilization of PET bottles and foils  

NASA Astrophysics Data System (ADS)

Modern packaging materials such as polyethylene terephthalate (PET) offer various advantages over glass or metal containers. Beside this they only offer poor barrier properties against gas permeation. Therefore, the shelf-live of packaged food is reduced. Additionally, common sterilization methods like heat, hydrogen peroxide or peracetic acid may not be applicable due to reduced heat or chemical resistance of the plastic packaging material. For the plasma sterilization and permeation barrier coating of PET bottles and foils, a microwave driven low pressure plasma reactor is developed based on a modified Plasmaline antenna. The dependencies of important plasma parameters, such as gas mixture, process pressure, power and pulse conditions on oxygen permeation through packaging foil are investigated. A residual permeation as low as J = 1.0 ±0.3 cm^3m-2day-1bar-1 for 60 nm thick silicon oxide (SiOx) coated PET foils is achieved. To discuss this residual permeation, coating defects are visualized by capacitively coupled atomic oxygen plasma etching of coated substrate. A defect density of 3000 mm-2 is revealed responsible for permeation. For plasma sterilization, optimized plasma parameters based on fundamental research of plasma sterilization mechanisms permit short treatment times of a few seconds.

Steves, Simon; Deilmann, Michael; Bibinov, Nikita; Awakowicz, Peter

2009-10-01

20

Spacecraft Sterilization Using Non-Equilibrium Atmospheric Pressure Plasma  

NASA Technical Reports Server (NTRS)

As a solution to chemically and thermally destructive sterilization methods currently used for spacecraft, non-equilibrium atmospheric pressure plasmas are used to treat surfaces inoculated with Bacillus subtilis and Deinococcus radiodurans. Evidence of significant morphological changes and reduction in viability due to plasma exposure will be presented, including a 4-log reduction of B. subtilis after 2 minutes of dielectric barrier discharge treatment.

Cooper, Moogega; Vaze, Nachiket; Anderson, Shawn; Fridman, Gregory; Vasilets, Victor N.; Gutsol, Alexander; Tsapin, Alexander; Fridman, Alexander

2007-01-01

21

Sterilization of bacterial endospores by an atmospheric-pressure argon plasma jet  

NASA Astrophysics Data System (ADS)

Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. However, the spore-killing efficiency of the atmospheric-pressure argon-oxygen jet depends very sensitively on the oxygen concentration in the argon gas.

Uhm, Han S.; Lim, Jin P.; Li, Shou Z.

2007-06-01

22

[A double inductively coupled low-pressure plasma for sterilization of medical implant materials].  

PubMed

The potential of plasma treatment in medicine is only slowly gaining acceptance. Inactivation of germs through exposure to UV radiation produced by plasma discharges and sterilization of medical implant devices and instruments is one possible application of this technique. In addition, due to the manifold possibilities of coating through plasma processes, quick sterilization-coating combinations of medical implant devices are possible. To analyze the effectiveness of this sterilization process on different material surfaces, three different alloys (X2CrNiMo18-15-3, Ti6Al7Nb and Ti6Al4V) and one thermoplastic material (ultra-high molecular weight polyethylene, UHMWPE), commonly used in medical implant devices, were examined in the presented study. After spraying Bacillus atrophaeus spores (10(6) CFU) on the surfaces of four different implant materials tested in this study (X2CrNiMo18-15-3, UHMWPE, Ti6Al7Nb and Ti6Al4V), it was demonstrated in each of four gas mixtures used (Ar, Ar:O2, Ar:H2 and Ar:N2) that due to the application of inductively coupled low-pressure plasma technique, plain medical implant materials can be sterilized rapidly, and can be protective and efficient. PMID:18643713

Hauser, Jörg; Halfmann, Helmut; Awakowicz, Peter; Köller, Manfred; Esenwein, Stefan A

2008-08-01

23

A novel plasma source for sterilization of living tissues  

NASA Astrophysics Data System (ADS)

A source for the production of low-power plasmas at atmospheric pressure, to be used for the nondamaging sterilization of living tissues, is presented. The source, powered by radiofrequency and working with a helium flow, has a specific configuration, studied to prevent the formation of electric arcs dangerous to living matter. It is capable of killing different types of bacteria with a decimal reduction time of 1-2 min; on the contrary, human cells such as conjunctival fibroblasts were found to be almost unharmed by the plasma. A high concentration of OH radicals, likely to be the origin of the sterilizing effect, is detected through their UV emission lines. The effect of the UV and the OH radicals on the fibroblasts was analysed and no significant effects were detected.

Martines, E.; Zuin, M.; Cavazzana, R.; Gazza, E.; Serianni, G.; Spagnolo, S.; Spolaore, M.; Leonardi, A.; Deligianni, V.; Brun, P.; Aragona, M.; Castagliuolo, I.; Brun, P.

2009-11-01

24

Long-distance oxygen plasma sterilization: Effects and mechanisms  

NASA Astrophysics Data System (ADS)

The distribution of electrons, ions and oxygen radicals in long-distance oxygen plasma and the germicidal effect (GE) of Escherichia coli on the surface of medical poly(tetrafluoroethylene) (PTFE) film were studied. The quantity of protein leakage and the production of lipid peroxide in bacterial suspension as well as the state of DNA were measured after sterilization to analyse the inactivation mechanisms. The results showed that the concentration of electrons and ions decreased rapidly with increasing the distance from the center of induction coil, which approximated to 0 at 30 cm, whereas the concentration of oxygen radicals reduced slowly, i.e. decreased 30% within 40 cm. GE value reached 3.42 in the active discharge zone (0 cm) and exceeded 3.32 within 40 cm when plasma treatment parameters were set as follows: plasma rf power at 100 W, treatment time at 60 s and oxygen flux at 40 cm 3/min. Fast etching action on cell membrane by electrons, ions and attacking polyunsaturation fatty acid (PUFA) in cell membrane by oxygen radicals are primary reasons of oxygen plasma sterilization in the active discharge and the afterglow zone, respectively. The GE of UV radiation in long-distance oxygen plasma is feebleness.

Liu, Hongxia; Chen, Jierong; Yang, Liqing; Zhou, Yuan

2008-01-01

25

Sterilization.  

PubMed

Male and female sterilization is a safe and effective form of permanent contraception. The number of patients accepting this method has rapidly increased over the last ten years and is likely to continue. In some countries the rate has plateaued out: in the USA it has been 31 per cent of all married women for the last eight years. Before sterilization it is important that adequate counselling is given to both partners and that the decision is not hurried. This is emphasized by the number of women and men requesting reversal of sterilization (thought to be between 0.1 and 10 per cent of all sterilizations). These requests for reversal usually come from couples who have remarried, tend to be younger, have fewer live children, have had more abortions, less schooling and are poor users of contraception. In these high-risk patients counselling and time to make the decision is essential. Other studies indicate that regret after puerperal sterilization may be commoner, but the risks of further pregnancies have to be weighed against sterilization regret. The methodology of male sterilization has changed little in the last ten years; it is simple and usually done under local anaesthesia. In contrast, female sterilization methods are constantly being refined, from laparotomy to laparoscopy and from extensive tubal destruction or excision to minimal tubal damage. The common methods now are mini-laparotomy and laparoscopy under local or general anaesthesia, with tubal occlusion by clips, rings or bipolar or thermal coagulation. There is no place now for unipolar diathermy, because of the higher complication rate, especially for major complications such as bowel burns. Recent multicentre studies comparing different methods give low rates for immediate morbidity and surgical complications (0.8 to 2.5 per cent of cases). Technical failure is rare but often due to a pre-existing condition, for example obesity or previous pelvic disease. Some failures are due, however, to difficulties with the instruments, especially at laparoscopy; here further developments and the use of teaching aids for those in training will help to reduce problems. Mortality from female sterilization is low, at 2 to 10 per 100 000 procedures; however, half is due in part to anaesthetic complications (hypoventilation), which can be avoided by intubation, and others are due to pre-existing medical conditions. Long-term follow-up has now shown that sterilization does not cause an increase in menstrual blood loss.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:6239731

Newton, J R

1984-12-01

26

Plasma-based ion implantation sterilization technique and ion energy estimation  

NASA Astrophysics Data System (ADS)

Plasma-based ion implantation (PBII) is applied as a sterilization technique for three-dimensional work pieces. In the sterilization process, a pulsed negative high voltage (5 ?s pulse width, 300 pulses/s,-800 V to -13 kV) is applied to the electrode (workpiece) under N2 at a gas pressure of 2.4 Pa. The resultant self-ignited plasma is shown to successfully reduce the number of active Bacillus pumilus cells by 105 times after 5 min of processing. The nitrogen ion energy is estimated using a simple method based on secondary ion mass spectroscopy analysis of the vertical distribution of nitrogen in PBII-treated Si.

Tanaka, T.; Watanabe, S.; Shibahara, K.; Yokoyama, S.; Takagi, T.

2005-07-01

27

Low-temperature low-damage sterilization based on UV radiation through plasma immersion  

NASA Astrophysics Data System (ADS)

This paper introduces a new type of high-frequency (HF) sustained discharge where the HF field applicator is a planar transmission line that allows us to fill with plasma a long chamber of rectangular cross-section (typically 1 m × 15 cm × 5 cm). Peculiar interesting features of this plasma source are a low gas temperature (typically below 40 °C in the 1 Torr range in argon), broadband impedance matching with no need for retuning, stability and reproducibility of the discharge (non-resonant behaviour). This type of plasma source could be useful for web processing; nonetheless, it is applied here to plasma sterilization, taking advantage of its low gas temperature to inactivate microorganisms on polymer-made medical devices to avoid damaging them. The predominant biocide species are the UV photons emitted by the discharge whereas most plasma sterilization techniques call for reactive species such as O atoms and OH molecules, which induce significant erosion damage on polymers. Polystyrene microspheres are actually observed to be erosion-free under the current plasma sterilization conditions (scanning electron micrographs have been examined). Moreover, inactivation is quite fast: 106 B. atrophaeus spores deposited on a Petri dish are inactivated in less than 1 min. Correlation of the UV radiation with the spore inactivation rate is examined by (i) considering the emitted light intensity integrated over the 112-180 nm vacuum UV (VUV) range with a photomultiplier; (ii) looking with an optical spectrometer at the emission spectrum over the 200-400 nm UV range; (iii) using absorption spectroscopy to determine the role of the VUV argon resonant lines (105 and 107 nm) on spore inactivation. It is found that the test-reference spores are mainly inactivated by VUV photons (112-180 nm) that are primarily emitted by impurities present in the argon plasma.

Pollak, J.; Moisan, M.; Kéroack, D.; Boudam, M. K.

2008-07-01

28

Effect of Dielectric and Liquid on Plasma Sterilization Using Dielectric Barrier Discharge Plasma  

PubMed Central

Plasma sterilization offers a faster, less toxic and versatile alternative to conventional sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge surface plasma generator, we achieved ?6 log reduction in concentration of vegetative bacterial and yeast cells within 4 minutes and ?6 log reduction of Geobacillus stearothermophilus spores within 20 minutes. Plasma sterilization is influenced by a wide variety of factors. Two factors studied in this particular paper are the effect of using different dielectric substrates and the significance of the amount of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC)), it is noted that the FR4 is more efficient in terms of time taken for complete inactivation. FR4 is more efficient at generating plasma as shown by the intensity of spectral peaks, amount of ozone generated, the power used and the speed of killing vegetative cells. The surface temperature during plasma generation is also higher in the case of FR4. An inoculated FR4 or SC device produces less ozone than the respective clean devices. Temperature studies show that the surface temperatures reached during plasma generation are in the range of 30°C–66°C (for FR4) and 20°C–49°C (for SC). Surface temperatures during plasma generation of inoculated devices are lower than the corresponding temperatures of clean devices. pH studies indicate a slight reduction in pH value due to plasma generation, which implies that while temperature and acidification may play a minor role in DBD plasma sterilization, the presence of the liquid on the dielectric surface hampers sterilization and as the liquid evaporates, sterilization improves. PMID:23951023

Mastanaiah, Navya; Johnson, Judith A.; Roy, Subrata

2013-01-01

29

The role of chemical sputtering during plasma sterilization of Bacillus atrophaeus  

NASA Astrophysics Data System (ADS)

The inactivation of bacteria by plasma discharges offers the unique benefits of short treatment times, minimal damage to the objects being sterilized and minimal use of hazardous chemicals. Plasmas produce reactive fluxes of ions, atoms and UV photons from any given precursor gas and are expected to be a viable method for such sterilization applications. The plasma based inactivation of harmful biological systems is, however, not yet widely used, because any validation is hampered by the limited knowledge about the interaction mechanisms at the interface between a plasma and a biological system. By using quantified beams of hydrogen atoms, argon ions and UV photons, the treatment of bacteria in a typical argon-hydrogen plasma is mimicked in a very controlled manner. As an example the inactivation of endospores of Bacillus atrophaeus is studied. It is shown that the impact of H atoms alone causes no inactivation of bacteria. Instead, the simultaneous impact of atoms and low energy ions causes a perforation of the endosporic shell. The same process occurs during plasma treatment and explains the efficient inactivation of bacteria.

Opretzka, J.; Benedikt, J.; Awakowicz, P.; Wunderlich, J.; von Keudell, A.

2007-05-01

30

PLASMA STERILIZATION Plasma sterilization is fast evolving into a promising alternative to standard  

E-print Network

of the page. Now imagine a layer of spores on a surface as shown at the top of the page. When the plasma in these experiments. The process involves UV irradiation, photo-desorption and chemical etching. The spores exposed a solution of yeast spores to plasma for different times of exposure. · As can be seen above

Roy, Subrata

31

Examining the Role of Ozone in Surface Plasma Sterilization Using Dielectric Barrier  

E-print Network

Examining the Role of Ozone in Surface Plasma Sterilization Using Dielectric Barrier Discharge (DBD (DBD) devices are known ozone generators. Authors have previously demonstrated a DBD surface plasma and sterilization in 20 min (bacterial spores). The aim of this paper is to examine the role of the ozone in surface

Roy, Subrata

32

Atmospheric Pressure Plasma Induced Sterilization and Chemical Neutralization  

NASA Astrophysics Data System (ADS)

We are studying chemical neutralization and surface decontamination using atmospheric pressure plasma discharges. The plasma is produced by corona discharge from an array of pins and a ground plane. The array is constructed so that various gases, like argon or helium, can be flowed past the pins where the discharge is initiated. The pin array can be biased using either DC, AC or pulsed discharges. Results indicate that the atmospheric plasma is effective in sterilizing surfaces with biological contaminants like E-coli and bacillus subtilus cells. Exposure times of less than four minutes in an air plasma result in a decrease in live colony counts by six orders of magnitude. Greater exposure times result in a decrease of live colony counts of up to ten orders of magnitude. The atmospheric pressure discharge is also effective in decomposing organic phosphate compounds that are simulants for chemical warfare agents. Details of the decomposition chemistry, by-product formation, and electrical energy consumption of the system will be discussed.

Garate, Eusebio; Evans, Kirk; Gornostaeva, Olga; Alexeff, Igor; Lock Kang, Weng; Wood, Thomas K.

1998-11-01

33

Comparative evaluation of the sporicidal activity of new low-temperature sterilization technologies: Ethylene oxide, 2 plasma sterilization systems, and liquid peracetic acid  

Microsoft Academic Search

Objective: This study was undertaken to evaluate the efficacy of 4 new low-temperature sterilization technologies: ethylene oxide with hydrochlorofluorocarbons, a liquid peracetic acid immersion system (Steris System 1 Processor), and 2 plasma sterilization processes that use vaporized hydrogen peroxide (Sterrad 100 and the Sterrad 100S). The Sterrad 100S system potentially improves sterilizer efficacy by using 2 cycles of a diffusion

William A. Rutala; Maria F. Gergen; David J. Weber

1998-01-01

34

Estimation of Nitrogen Ion Energy in Sterilization Technology by Plasma Based Ion Implantation  

NASA Astrophysics Data System (ADS)

Plasma based ion implantation (PBII) with negative voltage pulses to the test specimen has been applied to the sterilization process as a technique suitable for three-dimensional work pieces. Pulsed high negative voltage (5 ?s pulse width, 300 pulses/s, -800 V to -15 kV) was applied to the electrode in this process at a gas pressure of 2.4 Pa of N2. We found that the PBII process, in which N2 gas self-ignitted plasma generated by only pulsed voltages is used, reduces the number of active Bacillus pumilus cell. The number of bacteria survivors was reduced by 10-5 x with 5 min exposure. Since the ion energy is the most important processing parameter, a simple method to estimate the nitrogen ion energy from distribution of nitrogen atoms in Si implanted by PBII was developed. The implanted ion energy is discussed from the SIMS in depth profiles.

Kondou, Youhei; Nakashima, Takeru; Tanaka, Takeshi; Takagi, Toshinori; Watanabe, Satoshi; Ohkura, Kensaku; Shibahara, Kentaro; Yokoyama, Shin

35

The Effect of Air Plasma on Sterilization of Escherichia coli in Dielectric Barrier Discharge  

NASA Astrophysics Data System (ADS)

In this work, a Dielectric Barrier Discharge (DBD) air plasma was used to sterilize Escherichia coli (E. coli) on the surface of medical Polyethylene Terephthalate (PET) film. The leakage of cellular DNA and protein by optical absorbance measurement at 260 nm and 280 nm, together with transmission electron microscopy (TEM) about cell morphology were performed after sterilization to analyse inactivation mechanisms. The results indicated that the DBD air plasma was very effective in E. coli sterilization. The plasma germicidal efficiency depended on the plasma treatment time, the air-gap distance, and the applied voltage. Within 5 min of plasma treatment, the germicidal efficiency against E. coli could reach 99.99%. An etching action on cell membranes by electrons, ions and radicals is the primary mechanism for DBD air plasma sterilization, which leads to the effusion of cellular contents (DNA and protein) and bacterial death.

Hu, Miao; Guo, Yun

2012-08-01

36

Sterilization of Staphylococcus Aureus by an Atmospheric Non-Thermal Plasma Jet  

NASA Astrophysics Data System (ADS)

An atmospheric non-thermal plasma jet was developed for sterilizing the Staphylococcus aureus (S. aureus). The plasma jet was generated by dielectric barrier discharge (DBD), which was characterized by electrical and optical diagnostics. The survival curves of the bacteria showed that the plasma jet could effectively inactivate 106 cells of S. aureus within 120 seconds and the sterilizing efficiency depended critically on the discharge parameter of the applied voltage. It was further confirmed by scanning electron microscopy (SEM) that the cell morphology was seriously damaged by the plasma treatment. The plasma sterilization mechanism of S. aureus was attributed to the active species of OH, N2+ and O, which were generated abundantly in the plasma jet and characterized by OES. Our findings suggest a convenient and low-cost way for sterilization and inactivation of bacteria.

Liu, Xiaohu; Hong, Feng; Guo, Ying; Zhang, Jing; Shi, Jianjun

2013-05-01

37

[Dependency of a microbiological test of a formaldehyde gas sterilization procedure on the shape of objects to be sterilized].  

PubMed

During the last decade, a number of procedures have been developed by different firms for the sterilization of heat-sensitive instruments using a mixture of formaldehyde and water vapor at a temperature of approximately 60 degrees C as means of sterilization. Instruments to be sterilized by this technique as e.g. sounds and catheters normally have long narrow cavities. Therefore, the formaldehyde gas sterilization procedures have to be tested primarily for their capability of achieving a sufficient microbicidal effect within those cavities. For this purpose, the bioindicators are placed into special test pieces. The test pieces commonly in use differ widely in their construction, shape, and size. They mostly consist of some hollow cylinder with an attached capillary or a tube (see Table 1). The authors demonstrated by means of models that the variety of test pieces in use meant that the sterilization procedures had to meet quite different requirements. The models consisted of flexible tubes differing in diameter and length and were connected to short glass tubes. These glass tubes having identical or wider inner diameters than the flexible tubes served as receptacles containing the bioindicators. Spores of Bacillus stearothermophilus served as test organisms. The spores were suspended in defibrinated sheep blood and dried on filter paper. The efficiency of the sterilization technique was measured in terms of the relative number of indicator strips with surviving germs (i.e. non-sterilized indicators) after treatment of the test pieces with the formaldehyde gas. At first, the test results were examined as to their dependency on the length of the flexible tubes. These tubes were 3 mm wide and 5 to 100 cm long, each being sealed at one end and with the bioindicators placed near the sealed end. The percentage of indicators with surviving germs increased with the length of the tubes. After the sterilization process, nearly all indicators (92%) contained in the 1 m tubes proved to be non-sterile (see Table 2). The same results were obtained with tubes open at both ends, with the bioindicators located in the middle section of the tubes (see Table 3). Using tubes of 1 m length, the dependency of the test results on the inner diameter of the test pieces was demonstrated. While all indicators placed into tubes of 3 mm inner diameter still contained surviving germs, those in the tubes of 9 mm inner diameter were all sterile (see Table 4).(ABSTRACT TRUNCATED AT 400 WORDS) PMID:6367309

Spicher, G; Borchers, U

1983-06-01

38

Sorption Processes in Gas Sterilization in the Medical Sector  

PubMed Central

Sorption of ethylene oxide during and after gaseous sterilization is influenced by numerous factors. It was found that ethylene oxide desorption not only depends on material to be fumigated but also to a considerable degree on the wrapping material. Although polyethylene, polyamide (nylon), polytetrafluoroethylene (Teflon), silicone, aluminum, and glass beads contained no quantities of ethylene oxide detectable by gas chromatography after 72 h of aeration, residual amounts were definitely determined, even after 76 h of aeration in polypropylene, polystyrene, polyvinylchloride, paper products, and compound products of various plastics and paper mixtures. Desorption was, in all cases, found to be better when a mixture of ethylene oxide and methyl formate was used instead of pure ethylene oxide. PMID:4751803

Jordy, A.; Suhr, H.

1973-01-01

39

Effects of Environmental Humidity and Temperature on Sterilization Efficiency of Dielectric Barrier Discharge Plasmas in Atmospheric Pressure Air  

NASA Astrophysics Data System (ADS)

The inactivation of Bacillus atrophaeus spores by a dielectric barrier discharge (DBD) plasma in atmospheric humid air was investigated in order to develop a low-temperature, low-cost, and high-speed plasma sterilization technique. The biological indicators covered with a Tyvek sheet were set just outside the DBD plasma region, where air temperature and humidity as a discharge gas were precisely controlled by an environmental test chamber. The results show that the inactivation of B. atrophaeus spores was found to be dependent strongly on humidity, and was completed within 15 min at a relative humidity of 90% and a temperature of 30 °C. The treatment time for sterilization is shorter than those of conventional sterilization methods using ethylene oxide gas and dry heat treatment. The inactivation rates depend on not only relative humidity but also temperature, so that water content in air could determine the generation of reactive species such as hydroxyl radicals that are effective for the inactivation of B. atrophaeus spores.

Kikuchi, Yusuke; Miyamae, Masanori; Nagata, Masayoshi; Fukumoto, Naoyuki

2011-01-01

40

Inductively-Coupled RF Powered O2 Plasma as a Sterilization Source  

NASA Technical Reports Server (NTRS)

Low-temperature or cold plasmas have been shown to be effective for the sterilization of sensitive medical devices and electronic equipment. Low-temperature plasma sterilization procedures possess certain advantages over other protocols such as ethylene oxide, gamma radiation, and heat due to the use of inexpensive reagents, the insignificant environmental impacts and the low energy requirements. In addition, plasmas may also be more efficacious in the removal of robust microorganisms due to their higher chemical reactivity. Together, these attributes render cold plasma sterilization as ideal for the surface decontamination requirements for NASA Planetary Protection. Hence, the work described in this study involves the construction, characterization, and application of an inductively-coupled, RF powered oxygen (O2) plasma.

Sharma, S. P.; Rao, M. V. V. S.; Cruden, B. A.; Meyyappan, M.; Mogul, R.; Khare, B.; Chan, S. L.; Arnold, James O. (Technical Monitor)

2001-01-01

41

Testing a steam-formaldehyde sterilizer for gas penetration efficiency.  

PubMed

A test piece is described for monitoring the performance of low-temperature steam-with-formaldehyde sterilizers. Comparative tests have shown it to be more difficult to penetrate than an arterial catheter when exposed to the same sterilizing conditions. It is permanent and simple to use and maintain. The growth or non-growth of bacterial spores, in the convenient form of spore strips, is used to indicate the efficacy of sterilization. PMID:4752414

Line, S J; Pickerill, J K

1973-09-01

42

Testing a steam-formaldehyde sterilizer for gas penetration efficiency  

PubMed Central

A test piece is described for monitoring the performance of low-temperature steam-with-formaldehyde sterilizers. Comparative tests have shown it to be more difficult to penetrate than an arterial catheter when exposed to the same sterilizing conditions. It is permanent and simple to use and maintain. The growth or non-growth of bacterial spores, in the convenient form of spore strips, is used to indicate the efficacy of sterilization. PMID:4752414

Line, Stuart J.; Pickerill, J. K.

1973-01-01

43

Sterilization effect of atmospheric pressure non-thermal air plasma on dental instruments  

PubMed Central

PURPOSE Autoclaves and UV sterilizers have been commonly used to prevent cross-infections between dental patients and dental instruments or materials contaminated by saliva and blood. To develop a dental sterilizer which can sterilize most materials, such as metals, rubbers, and plastics, the sterilization effect of an atmospheric pressure non-thermal air plasma device was evaluated. MATERIALS AND METHODS After inoculating E. coli and B. subtilis the diamond burs and polyvinyl siloxane materials were sterilized by exposing them to the plasma for different lengths of time (30, 60, 90, 120, 180 and, 240 seconds). The diamond burs and polyvinyl siloxane materials were immersed in PBS solutions, cultured on agar plates and quantified by counting the colony forming units. The data were analyzed using one-way ANOVA and significance was assessed by the LSD post hoc test (?=0.05). RESULTS The device was effective in killing E. coli contained in the plasma device compared with the UV sterilizer. The atmospheric pressure non-thermal air plasma device contributed greatly to the sterilization of diamond burs and polyvinyl siloxane materials inoculated with E. coli and B. subtilis. Diamond burs and polyvinyl siloxane materials inoculated with E. coli was effective after 60 and 90 seconds. The diamond burs and polyvinyl siloxane materials inoculated with B. subtilis was effective after 120 and 180 seconds. CONCLUSION The atmospheric pressure non-thermal air plasma device was effective in killing both E. coli and B. subtilis, and was more effective in killing E. coli than the UV sterilizer. PMID:23508991

Sung, Su-Jin; Huh, Jung-Bo; Yun, Mi-Jung; Chang, Brian Myung W.; Jeong, Chang-Mo

2013-01-01

44

Chemicophysical modifications induced by plasma and ozone sterilizations on shape memory polyurethane foams  

Microsoft Academic Search

Thermally activated shape memory polyurethane foams are promising materials for minimally invasive surgical procedures. Understanding\\u000a their physical and chemical properties, in vitro response and effects of sterilization is mandatory when evaluating their\\u000a potential as biomaterials. In this work, we report on the characterization of two Cold Hibernated Elastic Memory (CHEM) foams\\u000a before and after two novel low-temperature sterilization techniques (plasma

Luigi De Nardo; Monica Moscatelli; Federica Silvi; Maria Cristina Tanzi; L’Hocine Yahia; Silvia Farè

2010-01-01

45

Confirmation of the sterilization effect using a high concentration of ozone gas for the bio-clean room.  

PubMed

A high-level aseptic environment must be maintained in bio-cleanrooms used for the manufacture of sterile products. In the past, formaldehyde gas was most commonly used to sterilize bio-cleanrooms, but due to strict residual limitations there has been a need to develop a less toxic alternative choice. The authors have developed a revolutionary new sterilization system using a high concentration of ozone gas and used this system to sterilize an actual bio-cleanroom. This system integrates the ozone gas generator with the air conditioning system by proper control. The design specifications for the system included an ozone gas concentration of 200 ppm or more, relative humidity of 80% or more, and a sterilizing time of 120 min. Blow vents and suction ports were placed to ensure a uniform airflow which would extend through the entire room during ozone gas sterilization. Tests regarding long-term material exposure to ozone gas were conducted when the system was introduced to distinguish usable and unusable materials. In an actually constructed cleanroom, simulations were used to predict the evenness of the diffusion of ozone gas concentration and relative humidity during ozone gas sterilization, and measurements of the actual indoor ozone gas concentration, temperature and relative humidity during sterilization revealed that the ozone concentration and relative humidity needed for sterilization had been achieved generally throughout the entire environment. In addition, the CT value (mg/m(3) (=ppm) × min) , derived by multiplying the ozone gas concentration during ozone gas sterilization by the sterilization time, was equal to or greater than the target value of 24 × 10(3) (ppm·min) . When the results of sterilization in a cleanroom were confirmed using a biological indicator (BI) , negative results were obtained at all measurement points, demonstrating that sterilization was being performed effectively in the actual factory at which the ozone gas sterilization system had been introduced. PMID:23538847

Iwamura, Takuji; Nagano, Katsunori; Nogami, Toshihiro; Matsuki, Noritomo; Kosaka, Noriyoshi; Shintani, Hideharu; Katoh, Miyoshi

2013-01-01

46

Influence of oxygen in atmospheric-pressure argon plasma jet on sterilization of Bacillus atrophaeous spores  

NASA Astrophysics Data System (ADS)

A nonequilibrium Ar /O2 plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56MHz rf power supplier. The argon glow discharge with high electron density produces oxygen reactive species in large quantities. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. The decimal reduction time (D values) of the Ar /O2 plasma jet at an exposure distance of 0.5-1.5cm ranges from 5 to 57s. An actinometric comparison of the sterilization data shows that atomic oxygen radicals play a significant role in plasma sterilization. When observed under a scanning electron microscope, the average size of the spores appears to be greatly reduced due to chemical reactions with the oxygen radicals.

Lim, Jin-Pyo; Uhm, Han S.; Li, Shou-Zhe

2007-09-01

47

Radiative decay of keV-mass sterile neutrinos in a strongly magnetized plasma  

E-print Network

The radiative decay of sterile neutrinos with typical masses of 10 keV is investigated in the presence of a strong magnetic field and degenerate plasma. Full account is taken of the strongly modified photon dispersion relation relative to vacuum. The limiting cases of relativistic and non-relativistic plasma are analyzed. The decay rate in a strongly magnetized plasma as a function of the electron number density is compared with the un-magnetized case. We find that a strong magnetic field suppresses the catalyzing influence of the plasma on the decay rate.

Alexandra A. Dobrynina; Nicolay V. Mikheev; Georg G. Raffelt

2014-10-29

48

Radiative decay of keV-mass sterile neutrinos in a strongly magnetized plasma  

E-print Network

The radiative decay of sterile neutrinos with typical masses of 10 keV is investigated in the presence of a strong magnetic field and degenerate plasma. Full account is taken of the strongly modified photon dispersion relation relative to vacuum. The limiting cases of relativistic and non-relativistic plasma are analyzed. The decay rate in a strongly magnetized plasma as a function of the electron number density is compared with the un-magnetized case. We find that a strong magnetic field suppresses the catalyzing influence of the plasma on the decay rate.

Dobrynina, Alexandra A; Raffelt, Georg G

2014-01-01

49

Ternary gas plasma welding torch  

NASA Technical Reports Server (NTRS)

A plasma arc welding torch is discussed. A first plasma gas is directed through the body of the welding torch and out of the body across the tip of a welding electrode disposed at the forward end of the body. A second plasma gas is disposed for flow through a longitudinal bore in the electrode. The second plasma gas enters one end of the electrode and exits the electrode at the tip thereof for co-acting with the electric welding arc to produce the desired weld. A shield gas is directed through the torch body and circulates around the head of the torch adjacent to the electrode tip.

Rybicki, Daniel J. (inventor); Mcgee, William F. (inventor); Waldron, Douglas J. (inventor)

1995-01-01

50

Battling Bacterial Biofilms with Gas Discharge Plasma  

NASA Astrophysics Data System (ADS)

Most studies dealing with growth and physiology of bacteria have been carried out using free-living cells. However, most bacteria live in communities referred to as biofilms where cooperative interactions among their members make conventional methods of controlling microbial growth often ineffective. The use of gas discharge plasmas represents an alternative to traditional decontamination/sterilization methods. We studied biofilms using two organisms, Chromobacterium violaceum and Pseudomonas aeruginosa. With the first organism we demonstrated almost complete loss of cell culturability after a 5-min plasma treatment. However, additional determinations showed that non-culturable cells were still alive after short exposure times. We have recently reported the effect of plasma on P. aeruginosa biofilms grown on borosilicate coupons. In this paper, we present results for plasma treatments of 1-, 3-, and 7-day old P. aeruginosa biofilms grown on polycarbonate or stainless-steel coupons. Results indicate nearly 100% of ­biofilm inactivation after 5 min of exposure with similar inactivation kinetics for 1-, 3-, and 7-day-old biofilms, and for both materials used. The inactivation kinetics is similar for both organisms, suggesting that the method is useful regardless of the type of biofilm. AFM images show changes in biofilm structure for various plasma exposure times.

Zelaya, Anna; Vandervoort, Kurt; Brelles-Mariño, Graciela

51

Cold Atmospheric Air Plasma Sterilization against Spores and Other Microorganisms of Clinical Interest  

PubMed Central

Physical cold atmospheric surface microdischarge (SMD) plasma operating in ambient air has promising properties for the sterilization of sensitive medical devices where conventional methods are not applicable. Furthermore, SMD plasma could revolutionize the field of disinfection at health care facilities. The antimicrobial effects on Gram-negative and Gram-positive bacteria of clinical relevance, as well as the fungus Candida albicans, were tested. Thirty seconds of plasma treatment led to a 4 to 6 log10 CFU reduction on agar plates. C. albicans was the hardest to inactivate. The sterilizing effect on standard bioindicators (bacterial endospores) was evaluated on dry test specimens that were wrapped in Tyvek coupons. The experimental D23°C values for Bacillus subtilis, Bacillus pumilus, Bacillus atrophaeus, and Geobacillus stearothermophilus were determined as 0.3 min, 0.5 min, 0.6 min, and 0.9 min, respectively. These decimal reduction times (D values) are distinctly lower than D values obtained with other reference methods. Importantly, the high inactivation rate was independent of the material of the test specimen. Possible inactivation mechanisms for relevant microorganisms are briefly discussed, emphasizing the important role of neutral reactive plasma species and pointing to recent diagnostic methods that will contribute to a better understanding of the strong biocidal effect of SMD air plasma. PMID:22582068

Isbary, Georg; Shimizu, Tetsuji; Li, Yang-Fang; Zimmermann, Julia L.; Stolz, Wilhelm; Schlegel, Jurgen; Morfill, Gregor E.; Schmidt, Hans-Ulrich

2012-01-01

52

Cold atmospheric air plasma sterilization against spores and other microorganisms of clinical interest.  

PubMed

Physical cold atmospheric surface microdischarge (SMD) plasma operating in ambient air has promising properties for the sterilization of sensitive medical devices where conventional methods are not applicable. Furthermore, SMD plasma could revolutionize the field of disinfection at health care facilities. The antimicrobial effects on Gram-negative and Gram-positive bacteria of clinical relevance, as well as the fungus Candida albicans, were tested. Thirty seconds of plasma treatment led to a 4 to 6 log(10) CFU reduction on agar plates. C. albicans was the hardest to inactivate. The sterilizing effect on standard bioindicators (bacterial endospores) was evaluated on dry test specimens that were wrapped in Tyvek coupons. The experimental D(23)(°)(C) values for Bacillus subtilis, Bacillus pumilus, Bacillus atrophaeus, and Geobacillus stearothermophilus were determined as 0.3 min, 0.5 min, 0.6 min, and 0.9 min, respectively. These decimal reduction times (D values) are distinctly lower than D values obtained with other reference methods. Importantly, the high inactivation rate was independent of the material of the test specimen. Possible inactivation mechanisms for relevant microorganisms are briefly discussed, emphasizing the important role of neutral reactive plasma species and pointing to recent diagnostic methods that will contribute to a better understanding of the strong biocidal effect of SMD air plasma. PMID:22582068

Klämpfl, Tobias G; Isbary, Georg; Shimizu, Tetsuji; Li, Yang-Fang; Zimmermann, Julia L; Stolz, Wilhelm; Schlegel, Jürgen; Morfill, Gregor E; Schmidt, Hans-Ulrich

2012-08-01

53

The cold and atmospheric-pressure air surface barrier discharge plasma for large-area sterilization applications  

SciTech Connect

This letter reports a stable air surface barrier discharge device for large-area sterilization applications at room temperature. This design may result in visually uniform plasmas with the electrode area scaled up (or down) to the required size. A comparison for the survival rates of Escherichia coli from air, N{sub 2} and O{sub 2} surface barrier discharge plasmas is presented, and the air surface plasma consisting of strong filamentary discharges can efficiently kill Escherichia coli. Optical emission measurements indicate that reactive species such as O and OH generated in the room temperature air plasmas play a significant role in the sterilization process.

Wang Dacheng [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Zhao Di [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); School of Photoelectrical Engineering, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Feng Kecheng [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Zhang Xianhui [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Liu Dongping [School of Science, Changchun University of Science and Technology, Changchun, Jilin 130022 (China); Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); School of Physics and Materials Engineering, Dalian Nationalities University, Dalian 116600 (China); Yang Size [Department of Aeronautics, Fujian Key Laboratory for Plasma and Magnetic Resonance, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen, Fujian 361005 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100080 (China)

2011-04-18

54

Development of advanced antimicrobial and sterilized plasma polypropylene grafted muga (antheraea assama) silk as suture biomaterial.  

PubMed

Surface modification of silk fibroin (SF) materials using environmentally friendly and non-hazardous process to tailor them for specific application as biomaterials has drawn a great deal of interest in the field of biomedical research. To further explore this area of research, in this report, polypropylene (PP) grafted muga (Antheraea assama) SF (PP-AASF) suture is developed using plasma treatment and plasma graft polymerization process. For this purpose, AASF is first sterilized in argon (Ar) plasma treatment followed by grafting PP onto its surface. AASF is a non-mulberry variety having superior qualities to mulberry SF and is still unexplored in the context of suture biomaterial. AASF, Ar plasma treated AASF (AASFAr ) and PP-AASF are subjected to various characterization techniques for better comparison and the results are attempted to correlate with their observed properties. Excellent mechanical strength, hydrophobicity, antibacterial behavior, and remarkable wound healing activity of PP-AASF over AASF and AASFAr make it a promising candidate for application as sterilized suture biomaterial. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 355-365, 2014. PMID:23913788

Gogoi, Dolly; Choudhury, Arup Jyoti; Chutia, Joyanti; Pal, Arup Ratan; Khan, Mojibur; Choudhury, Manash; Pathak, Pallabi; Das, Gouranga; Patil, Dinkar S

2014-04-01

55

Reuse of healing abutments: an in vitro model of plasma cleaning and common sterilization techniques.  

PubMed

The reuse of transgingival healing abutments has been advocated by several implant manufacturers, but cleaning and sterilization procedures to yield clean and optimal surfaces have yet to be developed. The objective of this in vitro project was to investigate various cleaning and sterilization regimens for the removal of biological debris to support reattachment of subgingival connective tissue. Simulated clinical healing abutment surfaces were exposed to culture medium with serum for 1 hour to simulate biological exposure. Simulated healing abutment surfaces not contaminated by serum were used to represent the "as-is" healing abutment surface without prior in vivo use. The discs were cleaned with detergent before sterilization by ultraviolet light (UV) or steam autoclaving (AC) both with and without 1- and 5-minute plasma cleaning (PC). A series of surface analytical techniques (XPS, AES, and surface contact angles) and in vitro analysis of cell attachment and spreading using gingival fibroblasts were performed. After exposure to the simulated biological conditions, clinical cleaning followed by UV resulted in contaminated surfaces and relatively high levels of cell attachment. PC before UV treatment enhanced surface energetics but did not affect cell attachment and spreading. AC increased surface wetting angles; which were decreased somewhat by previous PC. Cell attachment was significantly reduced by AC. Although some increase in cell attachment after longer plasma cleaning was noted in the AC group, no difference in cell spreading was seen in any AC group. Cell spreading seemed to be less for all AC groups compared with all UV, as-is, and control groups. Although certain cleaning (PC) and sterilization (UV) procedures can be effective for cleaning transgingival healing abutments, those using AC are questionable due to their propensity for organic and inorganic contamination and unfavorable surface alteration. PMID:11307410

Vezeau, P J; Keller, J C; Wightman, J P

2000-01-01

56

Impact of chlorine dioxide gas sterilization on nosocomial organism viability in a hospital room.  

PubMed

To evaluate the ability of ClO2 to decontaminate pathogens known to cause healthcare-associated infections in a hospital room strains of Acinetobacter baumannii, Escherichia coli, Enterococcus faecalis, Mycobacterium smegmatis, and Staphylococcus aureus were spot placed in duplicate pairs at 10 sites throughout a hospital room and then exposed to ClO2 gas. Organisms were collected and evaluated for reduction in colony forming units following gas exposure. Six sterilization cycles with varied gas concentrations, exposure limits, and relative humidity levels were conducted. Reductions in viable organisms achieved ranged from 7 to 10-log reductions. Two sterilization cycles failed to produce complete inactivation of organisms placed in a bathroom with the door closed. Reductions of organisms in the bathroom ranged from 6-log to 10-log reductions. Gas leakage between hospital floors did not occur; however, some minor gas leakage from the door of hospital room was measured which was subsequently sealed to prevent further leakage. Novel technologies for disinfection of hospital rooms require validation and safety testing in clinical environments. Gaseous ClO2 is effective for sterilizing environmental contamination in a hospital room. Concentrations of ClO2 up to 385 ppm were safely maintained in a hospital room with enhanced environmental controls. PMID:23792697

Lowe, John J; Gibbs, Shawn G; Iwen, Peter C; Smith, Philip W; Hewlett, Angela L

2013-06-01

57

Analysis of Surface Sterilization and Properties of Medical Poly(tetrafluoroethylene) in Remote Argon Plasma  

Microsoft Academic Search

We have used a remote-argon-plasma reactor in which the active species can be separated at a special plasma field. Argon gas is used as the work gas. In this remote argon plasma, the distribution of electrons, ions, and radicals and germicidal effect (GE) of Escherichia coli on the surface of medical poly(tetrafluoroethylene) (PTFE) film are studied. Then surface properties of

Hong-Xia Liu; Jie-Rong Chen

2008-01-01

58

Acid Etching and Plasma Sterilization Fail to Improve Osseointegration of Grit Blasted Titanium Implants  

PubMed Central

Interaction between implant surface and surrounding bone influences implant fixation. We attempted to improve the bone-implant interaction by 1) adding surface micro scale topography by acid etching, and 2) removing surface-adherent pro-inflammatory agents by plasma cleaning. Implant fixation was evaluated by implant osseointegration and biomechanical fixation. The study consisted of two paired animal sub-studies where 10 skeletally mature Labrador dogs were used. Grit blasted titanium alloy implants were inserted press fit in each proximal tibia. In the first study grit blasted implants were compared with acid etched grit blasted implants. In the second study grit blasted implants were compared with acid etched grit blasted implants that were further treated with plasma sterilization. Implant performance was evaluated by histomorphometrical investigation (tissue-to-implant contact, peri-implant tissue density) and mechanical push-out testing after four weeks observation time. Neither acid etching nor plasma sterilization of the grit blasted implants enhanced osseointegration or mechanical fixation in this press-fit canine implant model in a statistically significant manner. PMID:22962567

Saks?, Mikkel; Jakobsen, Stig S; Saks?, Henrik; Baas, J?rgen; Jakobsen, Thomas; S?balle, Kjeld

2012-01-01

59

An overview of research using the one atmosphere uniform glow discharge plasma (OAUGDP) for sterilization of surfaces and materials  

Microsoft Academic Search

The medical, food processing, and heating, ventilating, and air conditioning industries are searching for improved pasteurization, disinfection, and sterilization technologies. Candidate techniques must deal with and overcome such problems as thermal sensitivity and destruction by heat, formation of toxic by-products, costs, and inefficiency in performance. We report the results of a plasma source, the One Atmosphere Uniform Glow Discharge Plasma

Thomas C. Montie; Kimberly Kelly-Wintenberg; J. Reece Roth

2000-01-01

60

Titan's gas and plasma torus  

NASA Technical Reports Server (NTRS)

The implications of the Voyager observations for a steady state model of a torus of hydrogen and nitrogen neutral gas and plasma are assessed. Constraints are placed on the nitrogen neutral density, the neutral hydrogen and nitrogen escape fluxes (from Titan), and the diffusion rate in terms of observed or inferred quantities. The results obtained are consistent with the Voyager observations.

Eviatar, A.; Podolak, M.

1983-01-01

61

Sterilization and Mechanism of Microorganisms on A4 Paper by Dielectric Barrier Discharges Plasma at Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

This study investigated the microorganisms' sterilization and mechanism by a DBD plasma device at atmospheric pressure. The device including a transfer system and two roller-electrodes is driven by sine-wave high voltages at frequencies of 15 kHz. Normal A4 papers were used to study the effects of the sterilization on their surfaces by analyzing the number of the living bacteria cells. The state of Escherichia coil's DNA were also measured by agarose gel electrophoresis after sterilization to analyze the inactivation mechanisms. Experimental results indicated that microorganisms on the surface of A4 Papers almost were destroyed while the papers went through the device and there was no any damage of the paper during the process. The main reason engendered bacteria death was due to the double chains of the DNA broken by the plasma.

Xianghong, Jia; Jun, Wan; Jinhua, Yang; Feng, Xu; Shouguo, Wang

2009-10-01

62

Development of a new atmospheric pressure cold plasma jet generator and application in sterilization  

NASA Astrophysics Data System (ADS)

This paper reports that a new plasma generator at atmospheric pressure, which is composed of two homocentric cylindrical all-metal tubes, successfully generates a cold plasma jet. The inside tube electrode is connected to ground, the outside tube electrode is connected to a high-voltage power supply, and a dielectric layer is covered on the outside tube electrode. When the reactor is operated by low-frequency (6 kHz-20 kHz) AC supply in atmospheric pressure and argon is steadily fed as a discharge gas through inside tube electrode, a cold plasma jet is blown out into air and the plasma gas temperature is only 25-30°C. The electric character of the discharge is studied by using digital real-time oscilloscope (TDS 200-Series), and the discharge is capacitive. Preliminary results are presented on the decontamination of E.colis bacteria and Bacillus subtilis bacteria by this plasma jet, and an optical emission analysis of the plasma jet is presented in this paper. The ozone concentration generated by the plasma jet is 1.0×1016cm-3 which is acquired by using the ultraviolet absorption spectroscopy.

Cheng, Cheng; Liu, Peng; Xu, Lei; Zhang, Li-Ye; Zhan, Ru-Juan; Zhang, Wen-Rui

2006-07-01

63

Plasma wakefield acceleration in self-ionized gas or plasmas.  

PubMed

Tunnel ionizing neutral gas with the self-field of a charged particle beam is explored as a possible way of creating plasma sources for a plasma wakefield accelerator [Bruhwiler et al., Phys. Plasmas (to be published)]. The optimal gas density for maximizing the plasma wakefield without preionized plasma is studied using the PIC simulation code OSIRIS [R. Hemker et al., in Proceeding of the Fifth IEEE Particle Accelerator Conference (IEEE, 1999), pp. 3672-3674]. To obtain wakefields comparable to the optimal preionized case, the gas density needs to be seven times higher than the plasma density in a typical preionized case. A physical explanation is given. PMID:14683089

Deng, S; Barnes, C D; Clayton, C E; O'Connell, C; Decker, F J; Erdem, O; Fonseca, R A; Huang, C; Hogan, M J; Iverson, R; Johnson, D K; Joshi, C; Katsouleas, T; Krejcik, P; Lu, W; Marsh, K A; Mori, W B; Muggli, P; Tsung, F

2003-10-01

64

Choosing a low-temperature sterilization technology.  

PubMed

Low-temperature sterilization technologies are used instead of steam for sterilizing heat-sensitive or moisture-intolerant surgical equipment and supplies. In this Guidance Article, we describe several common alternatives, but we focus specifically on the two that have generated the most interest in recent years: ethylene oxide (EtO) and gas plasma sterilization. Ethylene oxide has been used as a low-temperature sterilization technology since the 1950s. Although EtO can be used safely, exposure to this gas is known to be a health hazard, and the emissions from certain EtO sterilizers are known to pollute the atmosphere. For these reasons, the use of EtO is regulated--more strictly in some regions than in others--and many healthcare facilities have decided to investigate alternative technologies. Gas plasma sterilization emerged in the 1990s as one promising alternative. This method appears to pose fewer health and environmental risks, and it offers faster turnaround times. However, this technology also has some limitations. We describe the advantages and disadvantages of both methods, along with the factors to consider when selecting from among these alternatives, in this Guidance Article. PMID:10609148

1999-11-01

65

Removal and sterilization of biofilms and planktonic bacteria by microwave-induced argon plasma at atmospheric pressure  

NASA Astrophysics Data System (ADS)

Microbial biofilms are a functional matrix of microbial cells, enveloped in polysaccharides, enzymes and virulence factors secreted by them that can develop on indwelling medical devices and biomaterials. Plasma sterilization has been widely studied in recent years for biological applications. In this study, we evaluated the possibility of removal and anti-recovery of biofilms by microwave-induced argon plasma at atmospheric pressure. We observed that all bacterial biofilms formatted by Gram-negative and Gram-positive bacteria are removed in less than 20 s, and the growth inhibitions of planktonic bacteria within biofilms are also confirmed by plasma exposure for 5 s. These results suggest that our plasma system can be applied to medical and biological fields where the removal of biofilms and their debris is required.

Lee, Mi Hee; Park, Bong Joo; Jin, Soo Chang; Kim, Dohyun; Han, Inho; Kim, Jungsung; Hyun, Soon O.; Chung, Kie-Hyung; Park, Jong-Chul

2009-11-01

66

[Dependence of microbiologic test results of formaldehyde gas sterilization methods on the nature of the test material].  

PubMed

The efficiency of a formaldehyde gas sterilization procedure was evaluated with the aid of test pieces consisting of various materials. Both rigid and flexible tubes served as test pieces. The tubes were 75 cm long with an inner diameter of 1 mm and were sealed at one end. The bioindicators were placed inside the tubes close to the sealed end. Dried spores of Bacillus stearothermophilus adhering to linen threads served as test organisms. The test results varied according to the material of the test pieces and the thickness of their walls (see Table 1). In flexible tubes made of silicon rubber, all bioindicators became sterile, in tubes of stainless steel, all bioindicators exhibited test organisms that had survived. The findings for materials such as polyvinyl chloride, polyethylene, polyamide and polytetrafluorethylene ranged between these two extremes; the frequencies of bioindicators containing viable germs were 10, 55, 68 and 85%, respectively. Rigid and flexible tubes which had been sealed at both ends served to demonstrate that silicon rubber and polyvinyl chloride were highly permeable for formaldehyde and water vapour. Also the other plastic materials tested were permeable for formaldehyde and water vapour but longer exposure periods were needed to create conditions in the interior of the tubes that would result in a killing of the test organisms (see Fig 2). In this respect, polyamide exhibited a peculiar behaviour. The number of viable spores remained at the initial level for a long period before a decline took place. From the results of testing, it is concluded that test pieces must conform to the objects to be sterilized not only in their dimensions (length, inner diameter) but also in the characteristics of their material. The walls of the test pieces should not have a higher permeability for formaldehyde and water vapour than the material to be sterilized. The highest demands on the efficiency of formaldehyde gas sterilization procedures are those created by mental tubes and thick-walled flexible polytetrafluorethylene. Instruments and devices to be sterilized by a formaldehyde gas procedure should be preferentially made of materials which are sufficiently permeable for formaldehyde and water vapour as e.g. silicon rubber. Such gas-permeable components may considerably facilitate the sterilization of cavities which have a small lumen and are difficult to reach. PMID:3113100

Spicher, G; Borchers, U

1987-05-01

67

Neutral Gas Plasma Interactions in Space Plasma  

Microsoft Academic Search

A sounding rocket experiment, CRIT-II, involving the injection of shaped-charge barium in ionospheric plasma was conducted on May 7, 1989, to investigate Alfven's critical ionization velocity (CIV) hypothesis in space. The CRIT -II main payload was instrumented to make in situ measurements within the neutral barium beam. Among the detectors, UNH provided three energetic particle detectors and two photometers. The

Kan Liou

1994-01-01

68

Packaging materials for plasma sterilization with the flowing afterglow of an N2-O2 discharge: damage assessment and inactivation efficiency of enclosed bacterial spores  

NASA Astrophysics Data System (ADS)

In conventional sterilization methods (steam, ozone, gaseous chemicals), after their proper cleaning, medical devices are wrapped/enclosed in adequate packaging materials, then closed/sealed before initiating the sterilization process: these packaging materials thus need to be porous. Gaseous plasma sterilization being still under development, evaluation and comparison of packaging materials have not yet been reported in the literature. To this end, we have subjected various porous packagings used with conventional sterilization systems to the N2-O2 flowing afterglow and also a non-porous one to evaluate and compare their characteristics towards the inactivation of B. atrophaeus endospores deposited on a Petri dish and enclosed in such packagings. Because the sterilization process with the N2-O2 discharge afterglow is conducted under reduced-pressure conditions, non-porous pouches can be sealed only after returning to atmospheric pressure. All the tests were therefore conducted with one end of the packaging freely opened, post-sealing being required. The features of these packaging materials, namely mass loss, resistance, toxicity to human cells as well as some characteristics specific to the plasma method used such as ultraviolet transparency, were examined before and after exposure to the flowing afterglow. All of our results show that the non-porous packaging considered is much more suitable than the conventionally used porous ones as far as ensuring an efficient and low-damage sterilization process with an N2-O2 plasma-afterglow is concerned.

Levif, P.; Séguin, J.; Moisan, M.; Soum-Glaude, A.; Barbeau, J.

2011-10-01

69

Tubal Sterilization  

MedlinePLUS

... sterilization? That depends on your general health, your attitude, your job and the type of sterilization. Recovery ... will likely have irregular periods after sterilization. As women get older, their periods change. How often your ...

70

EDITORIAL: Gas plasmas in biology and medicine  

NASA Astrophysics Data System (ADS)

It is my great pleasure to introduce this special cluster devoted to recent developments in biomedical plasma technology. It is an even greater pleasure to behold the enormous progress which has been made in this area over the last five years. Research on biomedical plasma applications proceeds hand in hand with the development of new material processing technologies, based on atmospheric plasma sources. In the beginning, major research effort was invested in the development and control of new plasma sources—in this laborious process, novel devices were constructed and characterized, and also new plasma physical phenomena were discovered. Self-constriction of micro-plasmas, pattern formation, filamentation of glow discharges and various mode transitions are just a few examples. It is a real challenge for theorists to gain an understanding of these complex phenomena. Later, the devices had to be thoroughly tested and automated, and various safety issues had to be addressed. At present, many atmospheric plasma sources are ready to use, but not all fundamental and technical problems have been resolved by far. There is still plenty of room for improvement, as in any dynamic area of research. The recent trends are clear: the application area of plasmas expands into processing of unconventional materials such as biological scaffolds, and eventually living human, animal and plant tissues. The gentle, precise and versatile character of cold plasmas simply invites this new application. Firstly, non-living surfaces have been plasma-treated to attain desired effects in biomedical research; tissue engineering will soon fully profit from this powerful technique. Furthermore, studies on cultured plant and animal cells have provided many findings, which are both fundamentally interesting and potentially applicable in health care, veterinary medicine and agriculture. The most important and hitherto unique property of plasma treatment is that it can evade accidental cell death and its attendant complications, such as inflammation and scarring. Another substantial research direction makes use of the bactericidal properties of the plasma. The number of findings on plasma inactivation of bacteria and spores is growing; plasma sterilization has already achieved some commercial success. In future, bacteriostatic properties of cold plasmas will even facilitate non-contact disinfection of human tissues. At this moment, one cannot explicitly list all the medical procedures in which cold plasmas will be involved. My personal intuition predicts widespread use of plasma treatment in dentistry and dermatology, but surely more applications will emerge in the course of this multi-disciplinary research. In fact, some plasma techniques, such as coagulation and coblation, are already used in clinical practice—this is another image of plasma science, which is so far unfamiliar to plasma physicists. Therefore, this particular topic forms a perfect platform for contacts between physicists and medical experts. Our colleagues from the medical scientific community will continue giving us feedback, suggestions or even orders. Biomedical plasmas should not become an isolated research area—we must grow together with medical research, listen to criticism, and eventually serve the physicians. Only then will this new field grow, flourish and bear fruit. All the above-mentioned topics meet in this issue of Journal of Physics D: Applied Physics, comprising the most significant examples of modern biomedical plasma research. Browsing through the contributions, the reader can trace back the progress in this field: from fundamental physical (numerical) studies, through phenomenology and physics of new discharges, studies on plasma-surface modification, bacterial inactivation tests, fundamental cell biological investigations, to final in vivo applications. One may ask why this selection has found its place in a purely physical journal—many contributions are concerned with (micro)-biology rather than physics. To me, the answer is clear: it is important to maintain t

Stoffels, Eva

2006-08-01

71

[Suitability of different procedures for the sterilization of microsurgical instruments. A review of current and future procedures].  

PubMed

A review of common methods of sterilization is presented. The principles of operation of steam, hot-air, and gas sterilizers, as well as that of a completely new method which uses H2O2 plasma, are described. The suitability of these methods for sterilizing microsurgical instruments was studied. This paper deals in particular with hot-air sterilization, which is preferred because of the low humidity involved. This method was investigated by recording temperature curves during sterilization. Sterilization with hot steam (autoclaving) has been shown to damage instruments by causing corrosion, to which the types of steel used to make these instruments are highly susceptible. A H2O2 plasma sterilization method is described which operates at low temperatures and with very low humidity. Its suitability for microsurgical instruments has been investigated. PMID:2243473

Draeger, J; Prüter, J W

1990-08-01

72

Reversible Sterilization  

ERIC Educational Resources Information Center

Notes that difficult questions arise concerning the use of sterilization for alleged eugenic and euthenic purposes. Thus, how reversible sterilization will be used with relation to the poor, mentally ill, mentally retarded, criminals, and minors, is questioned. (Author/AM)

Largey, Gale

1977-01-01

73

Gas arc constriction for plasma arc welding  

NASA Technical Reports Server (NTRS)

A welding torch for plasma arc welding apparatus has an inert gas applied circumferentially about the arc column externally of the constricting nozzle so as to apply a constricting force on the arc after it has exited the nozzle orifice and downstream of the auxiliary shielding gas. The constricting inert gas is supplied to a plenum chamber about the body of the torch and exits through a series of circumferentially disposed orifices in an annular wall forming a closure at the forward end of the constricting gas plenum chamber. The constricting force of the circumferential gas flow about the arc concentrates and focuses the arc column into a more narrow and dense column of energy after exiting the nozzle orifice so that the arc better retains its energy density prior to contacting the workpiece.

McGee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

1994-01-01

74

Sterilization/disinfection of medical devices using plasma: the flowing afterglow of the reduced-pressure N2-O2 discharge as the inactivating medium  

NASA Astrophysics Data System (ADS)

Potential sterilization/disinfection of medical devices (MDs) is investigated using a specific plasma process developed at the Université de Montréal over the last decade. The inactivating medium of the microorganisms is the flowing afterglow of a reduced-pressure N2-O2 discharge, which provides, as the main biocidal agent, photons over a broad ultraviolet (UV) wavelength range. The flowing afterglow is considered less damaging to MDs than the discharge itself. Working at gas pressures in the 400—700 Pa range (a few torr) ensures, through species diffusion, the uniform filling of large volume chambers with the species outflowing from the discharge, possibly allowing batch processing within them. As a rule, bacterial endospores are used as bio-indicators (BI) to validate sterilization processes. Under the present operating conditions, Bacillus atrophaeus is found to be the most resistant one and is therefore utilized as BI. The current paper reviews the main experimental results concerning the operation and characterization of this sterilizer/disinfector, updating and completing some of our previously published papers. It uses modeling results as guidelines, which are particularly useful when the corresponding experimental data are not (yet) available, hopefully leading to more insight into this plasma afterglow system. The species flowing out of the N2-O2 discharge can be divided into two groups, depending on the time elapsed after they left the discharge zone as they move toward the chamber, namely the early afterglow and the late afterglow. The early flowing afterglow from a pure N2 discharge (also called pink afterglow) is known to be comprised of N2+ and N4+ ions. In the present N2-O2 mixture discharge, NO+ ions are additionally generated, with a lifetime that extends over a longer period than that of the nitrogen molecular ions. We shall suppose that the disappearance of the NO+ ions marks the end of the early afterglow regime, thereby stressing our intent to work in an ion-free process chamber to minimize damage to MDs. Therefore, operating conditions should be set such that the sterilizer/disinfector chamber is predominantly filled by N and O atoms, possibly together with long-lived metastable-state O2(1 ?g) (singlet-delta) molecules. Various aspects related to the observed survival curves are examined: the actual existence of two “phases” in the inactivation rate, the notion of UV irradiation dose (fluence) and its implications, the UV photon best wavelength range in terms of inactivation efficiency, the influence of substrate temperature and the reduction of UV intensity through surface recombination of N and O atoms on the object/packaging being processed. To preserve their on-shelf sterility, MDs are sealed/wrapped in packaging material. Porous packaging materials utilized in conventional sterilization systems (where MDs are packaged before being subjected to sterilization) were tested and found inadequate for the N2-O2 afterglow system in contrast to a (non-porous) polyolefin polymer. Because the latter is non-porous, its corresponding pouch must be kept unsealed until the end of the process. Even though it is unsealed, but because the opening is very small the O2(1?g) metastable-state molecules are expected to be strongly quenched by the pouch material as they try to enter it and, as a result, only N and O atoms, together with UV photons, are significantly present within it. Therefore, by examining a given process under pouch and no-pouch conditions, it is possible to determine what are the inactivating agents operating: (i) when packaged, these are predominantly UV photons, (ii) when unpackaged, O2(1?g) molecules together with UV photons can be acting, (iii) comparing the inactivation efficiency under both packaged and unpackaged conditions allows the determination of the relative contribution of UV photons (if any) and O2(1?g) metastable-state molecules. Such a method is applied to pyrogenic molecules and to the enzymatic activity of lysozyme proteins once exposed to the N2-O2 flowing afterglow

Moisan, Michel; Boudam, Karim; Carignan, Denis; Kéroack, Danielle; Levif, Pierre; Barbeau, Jean; Séguin, Jacynthe; Kutasi, Kinga; Elmoualij, Benaïssa; Thellin, Olivier; Zorzi, Willy

2013-07-01

75

Endotoxin removal by radio frequency gas plasma (glow discharge)  

NASA Astrophysics Data System (ADS)

Contaminants remaining on implantable medical devices, even following sterilization, include dangerous fever-causing residues of the outer lipopolysaccharide-rich membranes of Gram-negative bacteria such as the common gut microorganism E. coli. The conventional method for endotoxin removal is by Food & Drug Administration (FDA)-recommended dry-heat depyrogenation at 250°C for at least 45 minutes, an excessively time-consuming high-temperature technique not suitable for low-melting or heat-distortable biomaterials. This investigation evaluated the mechanism by which E. coli endotoxin contamination can be eliminated from surfaces during ambient temperature single 3-minute to cumulative 15-minute exposures to radio-frequency glow discharge (RFGD)-generated residual room air plasmas activated at 0.1-0.2 torr in a 35MHz electrodeless chamber. The main analytical technique for retained pyrogenic bio-activity was the Kinetic Chromogenic Limulus Amebocyte Lysate (LAL) Assay, sufficiently sensitive to document compliance with FDA-required Endotoxin Unit (EU) titers less than 20 EU per medical device by optical detection of enzymatic color development corresponding to < 0.5 EU/ml in sterile water extracts of each device. The main analytical technique for identification of chemical compositions, amounts, and changes during sequential reference Endotoxin additions and subsequent RFGD-treatment removals from infrared (IR)-transparent germanium (Ge) prisms was Multiple Attenuated Internal Reflection (MAIR) infrared spectroscopy sensitive to even monolayer amounts of retained bio-contaminant. KimaxRTM 60 mm x 15 mm and 50mm x 15mm laboratory glass dishes and germanium internal reflection prisms were inoculated with E. coli bacterial endotoxin water suspensions at increments of 0.005, 0.05, 0.5, and 5 EU, and characterized by MAIR-IR spectroscopy of the dried residues on the Ge prisms and LAL Assay of sterile water extracts from both glass and Ge specimens. The Ge prism MAIR-IR measurements were repeated after employing 3-minute RFGD treatments sequentially for more than 10 cycles to observe removal of deposited matter that correlated with diminished EU titers. The results showed that 5 cycles, for a total exposure time of 15 minutes to low-temperature gas plasma, was sufficient to reduce endotoxin titers to below 0.05 EU/ml, and correlated with concurrent reduction of major endotoxin reference standard absorption bands at 3391 cm-1, 2887 cm-1, 1646 cm -1 1342 cm-1, and 1103 cm-1 to less than 0.05 Absorbance Units. Band depletion varied from 15% to 40% per 3-minute cycle of RFGD exposure, based on peak-to-peak analyses. In some cases, 100% of all applied biomass was removed within 5 sequential 3-minute RFGD cycles. The lipid ester absorption band expected at 1725 cm-1 was not detectable until after the first RFGD cycle, suggesting an unmasking of the actual bacterial endotoxin membrane induced within the gas plasma environment. Future work must determine the applicability of this low-temperature, quick depyrogenation process to medical devices of more complicated geometry than the flat surfaces tested here.

Poon, Angela

76

Design of experiments on a DC Steady State Atmospheric Pressure Plasma Sterilizer  

NASA Astrophysics Data System (ADS)

Our Resistive Barrier Discharge has been demonstrated to be successful on E. coli, Pseudomonas fluorescens (5RL), spores and bacteriophages. It has been tested successfully in sterilizing pagers at the St. Jude Research Hospital in Memphis, TN. In this recent work, we evaluate three primary factors in the atmospheric pressure resistive barrier discharge, hydrogen peroxide, charged ions and air (oxygen). The experiment used was Analysis of Variance (ANOVA) and regression analysis. The tests used 144 Petri Dishes and the bacteria used were E. coli. The hydrogen peroxide was used as a replacement for the water conductor on the resistive barrier discharge electrode. The charged ions were removed by a double charged wire mesh between the discharge and the Petri Dish. The air was displaced by a slow flow of nitrogen into the experimental area. The basic conclusions are that air, and charged ions are both extremely effective in killing bacteria. In addition, air and charged ions together strongly enhance each other. Hydrogen peroxide in our experiments did not enhance the kill rate.

Alexeff, Igor; Balasundaram, Arun; Sawheny, Rapinder

2009-11-01

77

Supersonic gas injector for plasma fueling  

SciTech Connect

A supersonic gas injector (SGI) has been developed for fueling and diagnostic applications on the National Spherical Torus Experiment (NSTX). It is comprised of a graphite converging-diverging Laval nozzle and a commercial piezoelectric gas valve mounted on a movable probe at a low field side midplane port location. Also mounted on the probe is a diagnostic package: a Langmuir probe, two thermocouples and five pickup coils for measuring toroidal, radial, vertical magnetic field components and magnetic fluctuations at the location of the SGI tip. The SGI flow rate is up to 4 x 10{sup 21} particles/s, comparable to conventional NSTX gas injectors. The nozzle operates in a pulsed regime at room temperature and a reservoir gas pressure up to 0.33 MPa. The deuterium jet Mach number of about 4, and the divergence half-angle of 5{sup o}-25{sup o} have been measured in laboratory experiments simulating NSTX environment. In initial NSTX experiments reliable operation of the SGI and all mounted diagnostics at distances 1-20 cm from the plasma separatrix has been demonstrated. The SGI has been used for fueling of ohmic and 2-4 MW NBI heated L- and H-mode plasmas. Fueling efficiency in the range 0.1-0.3 has been obtained from the plasma electron inventory analysis.

Soukhanovskii, V A; Kugel, H W; Kaita, R; Roquemore, A L; Bell, M; Blanchard, W; Bush, C; Gernhardt, R; Gettelfinger, G; Gray, T; Majeski, R; Menard, J; Provost, T; Sichta, P; Raman, R

2005-09-30

78

Maxwell Prize Session: Hot Plasma Effects in Gas Discharge Plasma  

NASA Astrophysics Data System (ADS)

Radio frequency (rf) gas discharges have been known for over a century. Recently, interest in low-pressure rf discharges has been revitalized due to great achievements and expectations in using such devices in plasma processing for manufacturing of semiconductor chips and lighting technology. In rf discharges the dominant interaction of the electromagnetic field with the plasma, and thus rf power absorption, takes place in the plasma boundary layer (near the electrode sheath in a capacitive and in the skin layer in an inductive rf discharge). The interaction of the electromagnetic field with plasma can be of local or nonlocal character. In the first case, there is local coupling between the rf current and the electric field described by a local complex conductivity tensor of a cold plasma. That corresponds to traditional (collisional) gas discharge physics. In the second case, electron thermal motion brings spatial dispersion into the relation between the rf current and the electric field, so that the conductivity tensor becomes a nonlocal operator. Stochastic (collisionless) electron heating, anomalous skin effect and a variety of plasma kinetic and nonlinear effects are typical for low-pressure rf discharges operating in the regime of nonlocal electrodynamics. Such phenomena are characteristic of hot fusion and space plasmas, where they are usually observed experimentally as some global effects. The ability to reproduce these phenomena in a table-top rf discharge experiment (equipped with spatially resolved electron kinetic and electromagnetic field diagnostics) makes the rf discharge a unique playground for basic plasma studies highly amenable to theoretical analysis. The subject of this talk is a review of nonlocal and nonlinear effects found in rf discharge experiments and theoretical analysis, where the interaction of electromagnetic field with plasma is controlled by the electron thermal motion rather than the electron-atom collisions. New features in the electron energy distribution, wave phase bifurcation and phase velocity reversal, collisionless and negative power absorption, harmonic generation and ponderomotive effect are found in these experiments and interpreted in terms of non-local, hot electron electrodynamics.

Godyak, Valery

2004-11-01

79

Gas plasma analysis using an emission spectrometer  

SciTech Connect

Techniques and methods for using an optical emission spectrometer were developed. The spectrometer was effective in identifying species of gas plasma and was used to determine the end-of-process for chlorine contaminated diodes, silicone nitride removal, and the removal of organic contamination. Methods of data collection and manipulation were developed and a spectral library program was obtained to assist in identifying the spectral peaks or heads. 14 refs., 19 figs.

Hester, M.D.

1990-01-01

80

Sterilization System  

NASA Technical Reports Server (NTRS)

Cox Sterile Products, Inc.'s Rapid Heat Transfer Sterilizer employs a heat exchange process that induces rapid air movement; the air becomes the heat transfer medium, maintaining a uniform temperature of 375 degrees Fahrenheit. It features pushbutton controls for three timing cycles for different instrument loads, a six-minute cycle for standard unpackaged instruments, eight minutes for certain specialized dental/medical instruments and 12 minutes for packaged instruments which can then be stored in a drawer in sterile condition. System will stay at 375 degrees all day. Continuous operation is not expensive because of the sterilizer's very low power requirements.

1990-01-01

81

Microwave sterilization.  

PubMed

This study has shown that representative fungi, viruses, and aerobic and anaerobic bacteria, including spore formers, can easily be killed in a conventional microwave oven with proper modifications. Metal instruments, including air turbine handpieces and burs, and acrylic dentures can be sterilized in short periods. Consistent sterilization can be accomplished only if the items to be sterilized are rotated in a three-dimensional manner throughout the microwave cavity. Arcing back to the magnetron and damage to the microwave oven are prevented by placing a radar absorbent material within the oven and with proper insulation of the item to be sterilized. PMID:3884686

Rohrer, M D; Bulard, R A

1985-02-01

82

Entrainment of cold gas into thermal plasma jets  

Microsoft Academic Search

There is increasing evidence that the entrainment of cold gas surrounding a turbulent plasma jet is more of an engulfment type process rather than simple diffusion. A variety of diagnostic techniques have been employed to determine the development of turbulence in a plasma jet and to measure concentration and temperatures of the cold gas entrained into atmospheric-pressure argon plasma jets

E. Pfender; J. Fincke; R. Spores

1991-01-01

83

Plasma bacterial and mitochondrial DNA distinguish bacterial sepsis from sterile systemic inflammatory response syndrome and quantify inflammatory tissue injury in nonhuman primates.  

PubMed

Systemic inflammatory response syndrome (SIRS) is a fundamental host response common to bacterial infection and sterile tissue injury. Systemic inflammatory response syndrome can cause organ dysfunction and death, but its mechanisms are incompletely understood. Moreover, SIRS can progress to organ failure or death despite being sterile or after control of the inciting infection. Biomarkers discriminating between sepsis, sterile SIRS, and postinfective SIRS would therefore help direct care. Circulating mitochondrial DNA (mtDNA) is a damage-associated molecular pattern reflecting cellular injury. Circulating bacterial 16S DNA (bDNA) is a pathogen-associated pattern (PAMP) reflecting ongoing infection. We developed quantitative polymerase chain reaction assays to quantify these markers, and predicting their plasma levels might help distinguish sterile injury from infection. To study these events in primates, we assayed banked serum from Papio baboons that had undergone a brief challenge of intravenous Bacillus anthracis delta Sterne (modified to remove toxins) followed by antibiotics (anthrax) that causes organ failure and death. To investigate the progression of sepsis to "severe" sepsis and death, we studied animals where anthrax was pretreated with drotrecogin alfa (activated protein C), which attenuates sepsis in baboons. We also contrasted lethal anthrax bacteremia against nonlethal E. coli bacteremia and against sterile tissue injury from Shiga-like toxin 1. Bacterial DNA and mtDNA levels in timed samples were correlated with blood culture results and assays of organ function. Sterile injury by Shiga-like toxin 1 increased mtDNA, but bDNA was undetectable: consistent with the absence of infection. The bacterial challenges caused parallel early bDNA and mtDNA increases, but bDNA detected pathogens even after bacteria were undetectable by culture. Sublethal E. coli challenge only caused transient rises in mtDNA consistent with a self-limited injury. In lethal anthrax challenge (n = 4), bDNA increased transiently, but mtDNA levels remained elevated until death, consistent with persistent septic tissue damage after bacterial clearance. Critically, activated protein C pretreatment (n = 4) allowed mtDNA levels to decay after bacterial clearance with sparing of organ function and survival. In summary, host tissue injury correlates with mtDNA whether infective or sterile. Mitochondrial DNA and bDNA polymerase chain reactions can quantify tissue injury incurred by septic or sterile mechanisms and suggest the source of SIRS of unknown origin. PMID:23247122

Sursal, Tolga; Stearns-Kurosawa, Deborah J; Itagaki, Kiyoshi; Oh, Sun-Young; Sun, Shiqin; Kurosawa, Shinichiro; Hauser, Carl J

2013-01-01

84

New disinfection and sterilization methods.  

PubMed Central

New disinfection methods include a persistent antimicrobial coating that can be applied to inanimate and animate objects (Surfacine), a high-level disinfectant with reduced exposure time (ortho-phthalaldehyde), and an antimicrobial agent that can be applied to animate and inanimate objects (superoxidized water). New sterilization methods include a chemical sterilization process for endoscopes that integrates cleaning (Endoclens), a rapid (4-hour) readout biological indicator for ethylene oxide sterilization (Attest), and a hydrogen peroxide plasma sterilizer that has a shorter cycle time and improved efficacy (Sterrad 50). PMID:11294738

Rutala, W. A.; Weber, D. J.

2001-01-01

85

The Use of Liquid Isopropyl Alcohol and Hydrogen Peroxide Gas Plasma to Biologically Decontaminate Spacecraft Electronics  

NASA Technical Reports Server (NTRS)

Legitimate concern exists regarding sending spacecraft and their associated hardware to solar system bodies where they could possibly contaminate the body's surface with terrestrial microorganisms. The NASA approved guidelines for sterilization as set forth in NPG 8020.12C, which is consistent with the biological contamination control objectives of the Committee on Space Research (COSPAR), recommends subjecting the spacecraft and its associated hardware to dry heat-a dry heat regimen that could potentially employ a temperature of 110(deg)C for up to 200 hours. Such a temperature exposure could prove detrimental to the spacecraft electronics. The stimulated growth of intermetallic compounds (IMCs) in metallic interconnects and/or thermal degradation of organic materials composing much of the hardware could take place over a prolonged temperature regimen. Such detrimental phenomena would almost certainly compromise the integrity and reliability of the electronics. Investigation of sterilization procedures in the medical field suggests that hydrogen peroxide (H202) gas plasma (HPGP) technology can effectively function as an alternative to heat sterilization, especially for heat-sensitive items. Treatment with isopropyl alcohol (IPA) in liquid form prior to exposure of the hardware to HPGP should also prove beneficial. Although IPA is not a sterilant, it is frequently used as a disinfectant because of its bactericidal properties. The use of IPA in electronics cleaning is widely recognized and has been utilized for many years with no adverse affects reported. In addition, IPA is the principal ingredient of the test fluid used in ionic contamination testers to assess the amount of ionic contamination found on the surfaces of printed wiring assemblies. This paper will set forth experimental data confirming the feasibility of the IPA/H202 approach to reach acceptable microbial reduction (MR) levels of spacecraft electronic hardware. In addition, a proposed process flow in which both IPA liquid and HPGP are utilized will be presented in Section 7.0.

Bonner, J. K.; Tudryn, Carissa D.; Choi, Sun J.; Eulogio, Sebastian E.; Roberts, Timothy J.; Tudryn, Carissa D.

2006-01-01

86

Gas discharge plasmas are effective in inactivating Bacillus and Clostridium spores.  

PubMed

Bacterial spores are the most resistant form of life and have been a major threat to public health and food safety. Nonthermal atmospheric gas discharge plasma is a novel sterilization method that leaves no chemical residue. In our study, a helium radio-frequency cold plasma jet was used to examine its sporicidal effect on selected strains of Bacillus and Clostridium. The species tested included Bacillus subtilis, Bacillus stearothermophilus, Clostridium sporogenes, Clostridium perfringens, Clostridium difficile, and Clostridium botulinum type A and type E. The plasmas were effective in inactivating selected Bacillus and Clostridia spores with D values (decimal reduction time) ranging from 2 to 8 min. Among all spores tested, C. botulinum type A and C. sporogenes were significantly more resistant to plasma inactivation than other species. Observations by phase contrast microscopy showed that B. subtilis spores were severely damaged by plasmas and the majority of the treated spores were unable to initiate the germination process. There was no detectable fragmentation of the DNA when the spores were treated for up to 20 min. The release of dipicolinic acid was observed almost immediately after the plasma treatment, indicating the spore envelope damage could occur quickly resulting in dipicolinic acid release and the reduction of spore resistance. PMID:22075631

Tseng, Shawn; Abramzon, Nina; Jackson, James O; Lin, Wei-Jen

2012-03-01

87

Nanoscale topographic changes on sterilized glass surfaces affect cell adhesion and spreading.  

PubMed

Producing sterile glass surfaces is of great importance for a wide range of laboratory and medical applications, including in vitro cell culture and tissue engineering. However, sterilization may change the surface properties of glass and thereby affect its use for medical applications, for instance as a substrate for culturing cells. To investigate potential effects of sterilization on glass surface topography, borosilicate glass coverslips were left untreated or subjected to several common sterilization procedures, including low-temperature plasma gas, gamma irradiation and steam. Imaging by atomic force microscopy demonstrated that the surface of untreated borosilicate coverslips features a complex landscape of microislands ranging from 1000 to 3000 nm in diameter and 1 to 3 nm in height. Steam treatment completely removes these microislands, producing a nanosmooth glass surface. In contrast, plasma treatment partially degrades the microisland structure, while gamma irradiation has no effect on microisland topography. To test for possible effects of the nanotopographic structures on cell adhesion, human gingival fibroblasts were seeded on untreated or sterilized glass surfaces. Analyzing fibroblast adhesion 3, 6, and 24 h after cell seeding revealed significant differences in cell attachment and spreading depending on the sterilization method applied. Furthermore, single-cell force spectroscopy revealed a connection between the nanotopographic landscape of glass and the formation of cellular adhesion forces, indicating that fibroblasts generally adhere weakly to nanosmooth but strongly to nanorough glass surfaces. Nanotopographic changes induced by different sterilization methods may therefore need to be considered when preparing sterile glass surfaces for cell culture or biomedical applications. PMID:24027204

Wittenburg, Gretel; Lauer, Günter; Oswald, Steffen; Labudde, Dirk; Franz, Clemens M

2014-08-01

88

Partial microwave-assisted wet digestion of animal tissue using a baby-bottle sterilizer for analyte determination by inductively coupled plasma optical emission spectrometry  

NASA Astrophysics Data System (ADS)

A procedure for partial digestion of bovine tissue is proposed using polytetrafluoroethylene (PTFE) micro-vessels inside a baby-bottle sterilizer under microwave radiation for multi-element determination by inductively coupled plasma optical emission spectrometry (ICP OES). Samples were directly weighed in laboratory-made polytetrafluoroethylene vessels. Nitric acid and hydrogen peroxide were added to the uncovered vessels, which were positioned inside the baby-bottle sterilizer, containing 500 mL of water. The hydrogen peroxide volume was fixed at 100 µL. The system was placed in a domestic microwave oven and partial digestion was carried out for the determination of Ca, Cu, Fe, Mg, Mn and Zn by inductively coupled plasma optical emission spectrometry. The single-vessel approach was used in the entire procedure, to minimize contamination in trace analysis. Better recoveries and lower residual carbon content (RCC) levels were obtained under the conditions established through a 2 4-1 fractional factorial design: 650 W microwave power, 7 min digestion time, 50 µL nitric acid and 50 mg sample mass. The digestion efficiency was ascertained according to the residual carbon content determined by inductively coupled plasma optical emission spectrometry. The accuracy of the proposed procedure was checked against two certified reference materials.

Matos, Wladiana O.; Menezes, Eveline A.; Gonzalez, Mário H.; Costa, Letícia M.; Trevizan, Lilian C.; Nogueira, Ana Rita A.

2009-06-01

89

Decomposition of tetrodotoxin using multi-gas plasma jet.  

PubMed

In this study, non-thermal multi-gas plasma treatments were performed for Tetrodotoxin (TTX) solution, and TTX decomposition was analyzed by liquid chromatography coupled with electrospray time-of-flight mass spectrometry. The TTX mass spectrum signal was reduced by plasma irradiations to different levels by using various gas species. Nitrogen plasma exhibited the optimal capability for TTX decomposition, followed by oxygen, argon, and carbon dioxide plasmas. The TTX concentration decreased 100-fold by nitrogen plasma treatment for 10 min. PMID:24646709

Takamatsu, Toshihiro; Miyahara, Hidekazu; Azuma, Takeshi; Okino, Akitoshi

2014-04-01

90

Impact of Gas Heating in Inductively Coupled Plasmas  

NASA Technical Reports Server (NTRS)

Recently it has been recognized that the neutral gas in inductively coupled plasma reactors heats up significantly during processing. The resulting gas density variations across the reactor affect reaction rates, radical densities, plasma characteristics, and uniformity within the reactor. A self-consistent model that couples the plasma generation and transport to the gas flow and heating has been developed and used to study CF4 discharges. A Langmuir probe has been used to measure radial profiles of electron density and temperature. The model predictions agree well with the experimental results. As a result of these comparisons along with the poorer performance of the model without the gas-plasma coupling, the importance of gas heating in plasma processing has been verified.

Hash, D. B.; Bose, D.; Rao, M. V. V. S.; Cruden, B. A.; Meyyappan, M.; Sharma, S. P.; Biegel, Bryan (Technical Monitor)

2001-01-01

91

Inert-Gas Diffuser For Plasma Or Arc Welding  

NASA Technical Reports Server (NTRS)

Inert-gas diffuser provides protective gas cover for weld bead as it cools. Follows welding torch, maintaining continuous flow of argon over newly formed joint and prevents it from oxidizing. Helps to ensure welds of consistently high quality. Devised for plasma arc keyhole welding of plates of 0.25-in. or greater thickness, also used in tungsten/inert-gas and other plasma or arc welding processes.

Gilbert, Jeffrey L.; Spencer, Carl N.; Hosking, Timothy J.

1994-01-01

92

21 CFR 610.12 - Sterility.  

...require sterility testing for Whole Blood, Cryoprecipitated Antihemophilic Factor, Platelets, Red Blood Cells, Plasma, Source Plasma, Smallpox Vaccine, Reagent Red Blood Cells, Anti-Human Globulin, and Blood Grouping Reagents....

2014-04-01

93

Plasma arc welding torch having means for vortexing plasma gas exiting the welding torch  

NASA Technical Reports Server (NTRS)

A plasma arc welding torch is described wherein a plasma gas is directed through the body of the welding torch and out of the body across the tip of the welding electrode disposed at the forward end of the body. The plasma gas is provided with a vortexing motion prior to exiting the body by a vortex motion imparting member which is mounted in an orifice housing member and carried in the forward portion of the torch body. The orifice housing member is provided with an orifice of an predetermined diameter through which the electric arc and the plasma gas exits.

Rybicki, Daniel J. (inventor); Mcgee, William F. (inventor)

1994-01-01

94

Synergistic sterilization effect of microwave-excited nonthermal Ar plasma, H2O2, H2O and TiO2, and a global modeling of the interactions  

NASA Astrophysics Data System (ADS)

A microwave-excited atmospheric-pressure plasma jet (uAPPJ) exhibited a synergistic sterilization effect when combined with hydrogen peroxide (H2O2), distilled water (DW) and titanium dioxide (TiO2) photocatalysis. The sterilization efficacy of H2O2-uAPPJ increased as the H2O2 concentration increased. The addition of TiO2 also remarkably increased the sterilization efficacy. To find the main factor for the sterilization effect, optical emission spectra and the degradation rate of a methylene blue solution were measured. Numerical analysis, a newly developed global modeling, was also conducted to discover the mechanisms. Both experimental measurements and global modeling results suggested that combinations of H2O2, DW and TiO2 increased the generation of hydroxyl radicals (·OH), which are known to be strong bactericidal agents. It was revealed that charged species, especially electrons, have a dominant role in the increase of ·OH.

Lee, H. Wk; Lee, H. W.; Kang, S. K.; Y Kim, H.; Won, I. H.; Jeon, S. M.; Lee, J. K.

2013-10-01

95

Round-robin evaluation of a solid-phase microextraction-gas chromatographic method for reliable determination of trace level ethylene oxide in sterilized medical devices.  

PubMed

Medical devices that are sterilized with ethylene oxide (EtO) retain small quantities of EtO residuals, which may cause negative systemic and local irritating effects, and must be accurately quantified to ensure non-toxicity. The goal of this round-robin study is to investigate the capability of a novel solid-phase microextraction-gas chromatographic (SPME-GC) method for trace-level EtO residuals analysis: three independent laboratories conducted a guided experiment using this SPME-GC method, in assessing method performance, ruggedness and the feasibility of SPME fibers. These were satisfactory across the independent laboratories, at the 0.05-5.00 ppm EtO range. This method was then successfully applied to analyze EtO residuals in several sterilized/aerated medical devices of various polymeric composition, reliably detecting and quantifying the trace levels of EtO residuals present ( approximately 0.05 ppm EtO). SPME is a feasible alternative for quantifying trace-level EtO residuals in sterilized medical devices, thereby lowering the limit of quantification (LOQ) by as much as two to three orders of magnitude over the current GC methodology of direct liquid injection. PMID:17853387

Harper, Thomas; Cushinotto, Lisa; Blaszko, Nancy; Arinaga, Julie; Davis, Frank; Cummins, Calvin; DiCicco, Michael

2008-02-01

96

Sterilization of Exopolysaccharides Produced by Deep-Sea Bacteria: Impact on Their Stability and Degradation  

PubMed Central

Polysaccharides are highly heat-sensitive macromolecules, so high temperature treatments are greatly destructive and cause considerable damage, such as a great decrease in both viscosity and molecular weight of the polymer. The technical feasibility of the production of exopolysaccharides by deep-sea bacteria Vibrio diabolicus and Alteromonas infernus was previously demonstrated using a bioproduct manufacturing process. The objective of this study was to determine which sterilization method, other than heat sterilization, was the most appropriate for these marine exopolysaccharides and was in accordance with bioprocess engineering requirements. Chemical sterilization using low-temperature ethylene oxide and a mixture of ionized gases (plasmas) was compared to the sterilization methods using gamma and beta radiations. The changes to both the physical and chemical properties of the sterilized exopolysaccharides were analyzed. The use of ethylene oxide can be recommended for the sterilization of polysaccharides as a weak effect on both rheological and structural properties was observed. This low-temperature gas sterilizing process is very efficient, giving a good Sterility Assurance Level (SAL), and is also well suited to large-scale compound manufacturing in the pharmaceutical industry. PMID:21566796

Rederstorff, Emilie; Fatimi, Ahmed; Sinquin, Corinne; Ratiskol, Jacqueline; Merceron, Christophe; Vinatier, Claire; Weiss, Pierre; Colliec-Jouault, Sylvia

2011-01-01

97

Vortices in a gas-discharge plasma  

Microsoft Academic Search

Processes of vortex generation in a weakly ionized gas are reviewed in circumstances where a high-speed flow propagates along the gas discharge and acoustic waves interact with a positive column. Results on the effect of longitudinal gas flow in the positive-column properties are presented. It is shown that in certain conditions the gas flow in the positive column gives rise

A R Aramyan; G A Galechyan

2007-01-01

98

A double plasma gas chromatography injector and detector.  

PubMed

A direct-current, chip-based plasma has been used for gas sample injection in gas chromatography. A second identical plasma chip has been used as the excitation source for an optical emission detector. The first plasma is normally continually sustained during operation, causing continuous ionisation/fragmentation of the sample, whilst the second plasma records the optical emission downstream. For injection, the first plasma is briefly interrupted, introducing a "plug" of unmodified sample into the system. Injection plug sizes of between 5 and 50 [micro sign]l have been reproducibly obtained, although significantly smaller volumes may be possible with the use of smaller cross-section columns, lower flow rates and/or shorter plasma interruption times. PMID:15472726

Naji, Omar P; Manz, Andreas

2004-10-01

99

Transition of RF internal antenna plasma by gas control  

SciTech Connect

The transition between the capacitively coupled plasma (CCP) and the inductively coupled plasma (ICP) was investigated with the internal radio frequency (RF) multi-turn antenna. The transition between them showed the hysteresis curve. The radiation power and the period of the self-pulse mode became small in proportion to the gas pressure. It was found that the ICP transition occurred by decreasing the gas pressure from 400 Pa.

Hamajima, Takafumi; Yamauchi, Toshihiko; Kobayashi, Seiji; Hiruta, Toshihito; Kanno, Yoshinori [Advanced Institute of Industrial Technology, 1-10-40 HigashiOhi, Shinagawa-ku, Tokyo, 140-0011 (Japan); Japan Atomic Energy Agency, 2-4 Tokai-mura, Naka-gun, Ibaraki-ken, 319-1195 (Japan)

2012-07-11

100

Sterilizations reconsidered?  

PubMed

Cowdin and Tuohey argue for a rethinking of Catholic bioethical principles and the Church's moral authority. Citing the Second Vatican Council for support, they argue that if the Church were to respect the proper autonomy of medicine, it would allow sterilizations. In this essay I argue against Cowdin and Tuohey's understanding that the Church has derived its moral laws independent of consultation with medicine and that it treats medicine simply as a source of technical expertise. I also argue that they misunderstand that nature of autonomy as well as the Church's position regarding the type of autonomy they request for medicine. I will especially argue against their understanding of the principles of totality and double effect as "dispensations" from the moral order. I conclude that they have provided no grounds to cause the Church to reconsider its condemnation of all sterilizations. PMID:11657267

Smith, Janet E

1998-04-01

101

Gas Puffing into the AMBAL-M Solenoid Plasma  

SciTech Connect

The central solenoid of AMBAL-M was filled with a turbulent plasma stream generated by a source located outside the entrance magnetic throat, the plasma {approx}0.4 m in diameter, with density {approx}1.5.10{sup 13} cm{sup -3}, electron temperature {approx}50 eV and ion energy {approx}200 eV was obtained.Additional hydrogen puffing allowed plasma density increase. The plasma with a cold component from ionized gas and charge exchange ions was heated by electrostatic oscillations produced by the working source. At optimized gas puffing the plasma density was increased to 5.10{sup 13} cm{sup -3} without substantial reduction of the ion temperature. No big differences in plasma properties were found between gas puffing through a gas-box and a ceramic tube.The plasma density increment was shown to depend only on the total amount of the injected gas. The experimental optimization was made for different values of solenoid magnetic field taking the diamagnetism into account.Neutral hydrogen distribution in the solenoid vacuum chamber and recycling rate were estimated from data of fast inverse magnetron gauges constructed in BINP.

Akhmetov, T.D.; Bespamyatnov, I.O.; Davydenko, V.I.; Kovalenko, Yu.V.; Krivenko, A.S.; Parakhin, I.K.; Razorenov, V.V.; Soldatkina, E.I

2005-01-15

102

NUCLEAR GENERATED PLASMAS IN NOBLE GAS THERMIONIC CONVERTERS  

Microsoft Academic Search

The generation of a plasma by fission fragment ionization in noble gas ; thermionic converters was investigated in a series of inpile experiments at the ; University of Michigan reactor. The plasma generated in Ne: Ar (1000: 1) at a ; pressure of 20 mm Hg was investigated in a plane parallel diode with electrically ; heated emitter and collector

F. E. Jamerson; R. H. Jr. Abrams; C. B. Leffert; R. Silver

1963-01-01

103

Gas-jet laser-plasma interaction experiments  

Microsoft Academic Search

Preliminary results of laser-plasma interaction studies at 1.06 and 0.53 microns with gas-jet targets are presented. Stimulated Brillouin backscatter is strong in the 100 microns scale-length plasmas, but sidescatter is weak. Temperature, transport, and absorption measurements are discussed.

F. J. Mayer; M. A. Buoniconto; G. E. Busch; G. C. Castella; G. Charatis; D. Jarrell; R. Schroeder; D. L. Matthews; D. Slater; J. Tarvin; C. Thomas; M. Herbst; B. Ripin

1981-01-01

104

Differential cross sections for modeling of noble gas plasmas  

Microsoft Academic Search

Differential cross sections are required to model the 3D diffusion of electrons in a gas under the influence of electromagnetic fields. In a low temperature plasma containing a noble gas elastic scattering from the neutral atoms is an important process governing this diffusion even at energies above the inelastic thresholds. We have calculated the phase shifts at such energies using

Allan Stauffer; Robert McEachran

2009-01-01

105

Momentum Model of Gas Jet Penetration in Plasma  

Microsoft Academic Search

The lack of penetration of supersonic gas jets used in recent disruption mitigation experiments is explained. In the model [1], a cold, thin, plasma halo forms over the surface of the jet, shielding the neutral gas interior. The magnetic field inside the jet is slightly less than the field outside as a result of the balance between sideways advection of

P. B. Parks

2005-01-01

106

Overview of gas balance in plasma fusion devices  

Microsoft Academic Search

Particle retention is a major constraint for future fusion devices like ITER in which the amount of tritium will be strictly limited for safety reasons. In the EU Task Force on plasma wall interaction, efforts are underway to investigate the gas balance, the particle retention and removal in fusion devices. Gas balance in JET, ASDEX Upgrade, TEXTOR and Tore Supra

107

Electron energy distribution function control in gas discharge plasmas  

SciTech Connect

The formation of the electron energy distribution function (EEDF) and electron temperature in low temperature gas discharge plasmas is analyzed in frames of local and non-local electron kinetics. It is shown, that contrary to the local case, typical for plasma in uniform electric field, there is the possibility for EEDF modification, at the condition of non-local electron kinetics in strongly non-uniform electric fields. Such conditions “naturally” occur in some self-organized steady state dc and rf discharge plasmas, and they suggest the variety of artificial methods for EEDF modification. EEDF modification and electron temperature control in non-equilibrium conditions occurring naturally and those stimulated by different kinds of plasma disturbances are illustrated with numerous experiments. The necessary conditions for EEDF modification in gas discharge plasmas are formulated.

Godyak, V. A. [Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109, USA and RF Plasma Consulting, Brookline, Massachusetts (United States)] [Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109, USA and RF Plasma Consulting, Brookline, Massachusetts (United States)

2013-10-15

108

[The suitability of bioindicators according to DIN 58948 part 4 for monitoring gas-sterilizers (author's transl)].  

PubMed

In the Federal Republic of Germany bioindicators according to DIN 58948, Part 4, are generally used for testing the efficacy of ethylene oxide sterilizers. They are based on spores of Bacillus subtilis dried in sheep-blood on the bottom of a small test tube. As some authors doubted the resistance of these indicators to ethylene oxide especially in comparison with spore soil and spores of Clostridium perfringens, three different test procedures were performed showing that spores of sulfite reducing clostridia (Cl. perfringens included) are less resistant to ethylene oxide than spores of B. subtilis. The results are summarized in tables 1 to 3. They are discussed with regard to literature on the subject with special emphasis to the significance of occlusion of spores in insoluble crystals. It is concluded that spores of B. subtilis are the most suitable test-organisms for monitoring ethylene oxide sterilization and that spore soil cannot be used for this purpose. PMID:6258352

Adam, W; Marcy, G

1980-01-01

109

Observations on a formaldehyde low-temperature steam sterilizer.  

PubMed

In Finnish hospitals, heat labile equipment is mostly sterilized by ethylene oxide (EO) gas. Formaldehyde sterilizers are rarely used. We have tested a new commercial autoclave constructed exclusively for formaldehyde and low-temperature steam (F-LTS) sterilization, offering a potentially safer and cheaper method of sterilization. Both the sterilizing efficacy of the apparatus and the levels of formaldehyde in the processed materials were studied. PMID:10285026

Kuronen, T

1987-10-01

110

Sterilization. Steam sterilizers and steam sterilizer standards--Australia.  

PubMed

The objectives that I have adopted for my contribution are: To describe the "environment" surrounding steam sterilization in Australian Hospitals; To describe the origin and features of current Australian steam sterilizer Standards; and To discuss some directions for future changes to hospital steam sterilization in Australia. PMID:10283154

Friend, D W

1987-06-01

111

Experimental Identification of Plasma Bullets on a Gas-stream Type Atmospheric Pressure Plasma Source  

NASA Astrophysics Data System (ADS)

In this work, an atmospheric pressure plasma source was experimentally constructed by a coaxial arrangement with a discharge electrode and a dielectric tube of 6 mm in an inner diameter. The atmospheric pressure plasma was formed in a noble gas (He) stream exposed to dielectric barrier discharges on AC high-voltage applications. The axial plasma propagation was evaluated from the high-speed photograph and the inductive current. The plasma ignited by the barrier discharges was observed as a plasma bullet traveling from the discharge electrode to ambient air. The velocity of plasma bullet was hypersonic of 3×103 ? 8×103 m/s. The velocity varied according to time and traveling length. The optically identified characteristic of plasma propagation indicated the same tendency as time and space resolved profiles of the plasma bullet travelling which was observed utilizing a Rogowski coil as the current monitor. The plasma density was evaluated from the inductive current of plasma bullets along the gas stream axis, and the plasma density was in the order of 1016 m-3.

Fukawatase, Ryosuke; Inazuka, Ryuta; Ohyama, Ryu-Ichiro

112

N? gas plasma inactivates influenza virus mediated by oxidative stress.  

PubMed

Here we show that N? gas plasma, produced by applying a short high-voltage pulse using a static induction (SI) thyristor power supply inactivates influenza virus. N? gas plasma treatment of influenza A and B viruses induced the degradation of viral proteins, including nucleoprotein, hemagglutinin, and neuraminidase. The injury of viral RNA genome and the inactivation of hemagglutination were also observed after N? gas plasma treatment. These changes were possibly due to changes in the viral envelope, because modification of the lipid content was also suggested by Fourier-transformed infrared spectroscopy. At least three major mechanisms of action (heat, UV-A, and oxidative stress (i.e. hydrogen peroxide-like molecules)) were found in this system. Among them, oxidative stress appeared to be the main factor in the inactivation of influenza virus. In addition, there was an increase in the nitrotyrosine content of viral proteins, suggesting that oxidative stress produced by N? gas plasma generation oxidized proteins. As a result, oxidation may be the most important factor in the inactivation, degradation, and modification of influenza virus by N? gas plasma. PMID:24389143

Sakudo, Akikazu; Misawa, Tatsuya; Shimizu, Naohiro; Imanishi, Yuichiro

2014-01-01

113

Microwave Plasma Sources for Gas Processing  

SciTech Connect

In this paper atmospheric pressure microwave discharge methods and devices used for producing the non-thermal plasmas for processing of gases are presented. The main part of the paper concerns the microwave plasma sources (MPSs) for environmental protection applications. A few types of the MPSs, i.e. waveguide-based surface wave sustained MPS, coaxial-line-based and waveguide-based nozzle-type MPSs, waveguide-based nozzleless cylinder-type MPS and MPS for microdischarges are presented. Also, results of the laboratory experiments on the plasma processing of several highly-concentrated (up to several tens percent) volatile organic compounds (VOCs), including Freon-type refrigerants, in the moderate (200-400 W) waveguide-based nozzle-type MPS (2.45 GHz) are presented. The results showed that the microwave discharge plasma fully decomposed the VOCs at relatively low energy cost. The energy efficiency of VOCs decomposition reached 1000 g/kWh. This suggests that the microwave discharge plasma can be a useful tool for environmental protection applications. In this paper also results of the use of the waveguide-based nozzleless cylinder-type MPS to methane reforming into hydrogen are presented.

Mizeraczyk, J. [Centre for Plasma and Laser Engineering, Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-952 Gdansk (Poland); Department of Marine Electronics, Gdynia Martime University, Morska 83, 81-225 Gdynia (Poland); Jasinski, M.; Dors, M.; Zakrzewski, Z. [Centre for Plasma and Laser Engineering, Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences, Fiszera 14, 80-952 Gdansk (Poland)

2008-03-19

114

Plasma Spraying of Copper by Hybrid Water-Gas DC Arc Plasma Torch  

NASA Astrophysics Data System (ADS)

Water-stabilized DC arc plasma torches offer a good alternative to common plasma sources used for plasma spraying applications. Unique properties of the generated plasma are determined by a specific plasma torch construction. This article is focused on a study of the plasma spraying process performed by a hybrid torch WSP500®-H, which combines two principles of arc stabilization—water vortex and gas flow. Spraying tests with copper powder have been carried out in a wide range of plasma torch parameters. First, analyses of particle in-flight behavior for various spraying conditions were done. After, particles were collected in liquid nitrogen, which enabled analyses of the particle in-flight oxidation. A series of spraying tests were carried out and coatings were analyzed for their microstructure, porosity, oxide content, mechanical, and thermal properties.

Kavka, T.; Mat?jí?ek, J.; Ctibor, P.; Mašláni, A.; Hrabovský, M.

2011-06-01

115

Synergy effect of heat and UV photons on bacterial-spore inactivation in an N2-O2 plasma-afterglow sterilizer  

NASA Astrophysics Data System (ADS)

As a rule, medical devices (MDs) made entirely from metals and ceramics can withstand, for sterilization purposes, elevated temperatures such as those encountered in autoclaves (moist heat >=120 °C) or Poupinel (Pasteur) ovens (dry heat >=160 °C). This not the case with MDs containing polymers: 70 °C seems to be a limit beyond which their structural and functional integrity will be compromised. Nonetheless, all the so-called low-temperature sterilization techniques, relying essentially on some biocidal chemistry (e.g. ethylene oxide, H2O2, O3), are operated at temperatures close to 65 °C, essentially to enhance the chemical reactivity of the biocidal agent. Based on this fact, we have examined the influence of increasing the temperature of the polystyrene Petri dish containing B. atrophaeus bacterial spores when exposing them to UV radiation coming from an N2-O2 flowing plasma afterglow. We have observed that, for a given UV radiation intensity, the inactivation rate increases with the temperature of the Petri dish, provided heat and UV photons are applied simultaneously, a clear case of synergistic effect. More specifically, it means that (i) simply heating the spores at temperatures below 65 °C without irradiating them with UV photons does not induce mortality; (ii) there is no additional increase in the inactivation rate when the Petri has been pre-heated and then brought back to ambient temperature before the spores are UV irradiated; (iii) no additional inactivation results from post-heating spores previously inactivated with UV radiation. Undoubtedly, the synergistic effect shows up only when the physico-chemical agents (UV photons and temperature) are simultaneously in action.

Boudam, M. K.; Moisan, M.

2010-07-01

116

Female Sterilization: Risk of Ectopic Pregnancy After Tubal Sterilization  

MedlinePLUS

... Female Sterilization: Ectopic Pregnancy Back to Female Sterilization Female Sterilization: Risk of Ectopic Pregnancy After Tubal Sterilization ... and Health Promotion Home Contraception Medical Eligibility Criteria Female Sterilization Vasectomy Reproductive Health Home Data and Statistics ...

117

Plasma Reforming And Partial Oxidation Of Hydrocarbon Fuel Vapor To Produce Synthesis Gas And/Or Hydrogen Gas  

DOEpatents

Methods and systems are disclosed for treating vapors from fuels such as gasoline or diesel fuel in an internal combustion engine, to form hydrogen gas or synthesis gas, which can then be burned in the engine to produce more power. Fuel vapor, or a mixture of fuel vapor and exhaust gas and/or air, is contacted with a plasma, to promote reforming reactions between the fuel vapor and exhaust gas to produce carbon monoxide and hydrogen gas, partial oxidation reactions between the fuel vapor and air to produce carbon monoxide and hydrogen gas, or direct hydrogen and carbon particle production from the fuel vapor. The plasma can be a thermal plasma or a non-thermal plasma. The plasma can be produced in a plasma generating device which can be preheated by contact with at least a portion of the hot exhaust gas stream, thereby decreasing the power requirements of the plasma generating device.

Kong, Peter C. (Idaho Falls, ID); Detering, Brent A. (Idaho Falls, ID)

2004-10-19

118

Gas embolism following bronchoscopic argon plasma coagulation: a case series.  

PubMed

Thermal ablation using argon plasma coagulation (APC) is a commonly used modality in the bronchoscopic management of central airway obstruction and hemoptysis. In experienced hands, APC is considered to be a relatively safe tool. Reported complications associated with APC use are rare and include hemorrhage, airway perforation, or airway fires. Systemic gas embolism has been reported with APC during laparoscopic hepatic surgeries, and we have reported one case of systemic gas embolism with cardiovascular collapse in the past. We now report the first case series of systemic, life-threatening gas embolism occurring as a complication of bronchoscopic application of APC. PMID:18988782

Reddy, Chakravarthy; Majid, Adnan; Michaud, Gaetane; Feller-Kopman, David; Eberhardt, Ralph; Herth, Felix; Ernst, Armin

2008-11-01

119

Mathematical model of gas plasma applied to chronic wounds  

SciTech Connect

Chronic wounds are a major burden for worldwide health care systems, and patients suffer pain and discomfort from this type of wound. Recently gas plasmas have been shown to safely speed chronic wounds healing. In this paper, we develop a deterministic mathematical model formulated by eight-species reaction-diffusion equations, and use it to analyze the plasma treatment process. The model follows spatial and temporal concentration within the wound of oxygen, chemoattractants, capillary sprouts, blood vessels, fibroblasts, extracellular matrix material, nitric oxide (NO), and inflammatory cell. Two effects of plasma, increasing NO concentration and reducing bacteria load, are considered in this model. The plasma treatment decreases the complete healing time from 25 days (normal wound healing) to 17 days, and the contributions of increasing NO concentration and reducing bacteria load are about 1/4 and 3/4, respectively. Increasing plasma treatment frequency from twice to three times per day accelerates healing process. Finally, the response of chronic wounds of different etiologies to treatment with gas plasmas is analyzed.

Wang, J. G.; Liu, X. Y.; Liu, D. W.; Lu, X. P. [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China)] [State Key Lab of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Zhang, Y. T. [Shandong Provincial Key Lab of UHV Technology and Gas Discharge Physics, School of Electrical Engineering, Shandong University, Jinan, Shandong Province 250061 (China)] [Shandong Provincial Key Lab of UHV Technology and Gas Discharge Physics, School of Electrical Engineering, Shandong University, Jinan, Shandong Province 250061 (China)

2013-11-15

120

Plasma formation using a capillary discharge in water and its application to the sterilization of E. coli  

NASA Astrophysics Data System (ADS)

An underwater electrical discharge in a narrow dielectric capillary provides the details of the evolution of microbubbles to plasma as formed by a tungsten electrode inserted in the capillary. An increase in the applied voltage forms microbubbles after water fills the capillary. A further increase in the voltage generates a surface discharge through the boundary of the bubble, elongating the bubble shape, and eventually forming plasma by electrical breakdown. This produces atomic oxygen, atomic hydrogen, and hydroxyl radicals from dissociation of water vapor. Also, a bactericidal test in normal saline solution showed that more than 99.6% of the bacterial cells were killed within 8 s, resulting from chlorine-containing species, in particular hypochlorous acid as a major bactericidal agent.

Hong, Yong Cheol; Park, Hyun Jae; Lee, Bong Ju; Kang, Won-Seok; Uhm, Han Sup

2010-05-01

121

Application of non-thermal plasma on gas cleansing  

NASA Astrophysics Data System (ADS)

Non-thermal plasma technologies are an interesting complement or alternative, for some conventional systems used for gas pollution control (i.e. wet scrubbers and catalytic converters) because they are able to remove simultaneously several gas pollutants, with quite good efficiency at a relatively low-energy consumption. In this work, a dielectric barrier discharge was used to remove nitric oxides (NOx) and sulfur dioxide (SO2) from a mixture of air and water vapor. A chemical model was developed to obtain a toxic gas removal mechanism and to observe the behavior of the species in the plasma. The influence of water vapor addition on the toxic gases removal efficiency is also investigated. Several experimental parameters such as power, frequency, initial concentration of NOx and SO2 were tested and analyzed. Results of numerical simulation demonstrated good agreement with experimental data of the removal process achieving about 95% of efficiency removal of toxic gases studied.

Pacheco, M.; Pacheco, J.; Moreno, H.; Santana, A.

2008-10-01

122

Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition  

NASA Astrophysics Data System (ADS)

An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O2 plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O2 plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O2 (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

Chen, Wei; Huang, Jun; Du, Ning; Liu, Xiao-Di; Wang, Xing-Quan; Lv, Guo-Hua; Zhang, Guo-Ping; Guo, Li-Hong; Yang, Si-Ze

2012-07-01

123

Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition  

SciTech Connect

An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O{sub 2} plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O{sub 2} plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O{sub 2} (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

Chen Wei; Huang Jun; Wang Xingquan; Lv Guohua; Zhang Guoping [Key Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, 100190 Beijing (China); Du Ning; Liu Xiaodi; Guo Lihong [Department of Oral Biology, Peking University School and Hospital of Stomatology, 100080 Beijing (China); Yang Size [Key Laboratory of Soft Matter Physics, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, 100190 Beijing (China); Fujian Key Laboratory for Plasma and Magnetic Resonance, Department of Aeronautics, School of Physics and Mechanical and Electrical Engineering, Xiamen University, Xiamen 361005 (China)

2012-07-01

124

Positron transport: The plasma-gas interface  

SciTech Connect

Motivated by an increasing number of applications, new techniques in the analysis of electron transport have been developed over the past 30 years or so, but similar methods had yet to be applied to positrons. Recently, an in-depth look at positron transport in pure argon gas has been performed using a recently established comprehensive set of cross sections and well-established Monte Carlo simulations. The key novelty as compared to electron transport is the effect of positronium formation which changes the number of particles and has a strong energy dependence. This coupled with spatial separation by energy of the positron swarm leads to counterintuitive behavior of some of the transport coefficients. Finally new results in how the presence of an applied magnetic field affects the transport coefficients are presented.

Marler, J. P. [University of Aarhus, Aarhus C DK-8000 (Denmark); Petrovic, Z. Lj.; Bankovic, A.; Dujko, S.; Suvakov, M.; Malovic, G. [Institute of Physics, P.O. Box 68, 11080 Belgrade (Serbia); Buckman, S. J. [CAMS, RSPhysSE, Australian National University, Canberra 2600 (Australia)

2009-05-15

125

Dynamic gas flow during plasma operation in TMX-U  

SciTech Connect

Control of the neutral density outside of the plasma radius is essential for proper operation of the various plasma configurations in TMX-U. TMX-U excess-beam, stream-gun, gas-box, and beam-reflux gases are pumped internally in regions defined by 73/sup 0/ Ti-gettered liners and warm Ti-gettered plasma liners. The array of fast and slow ion gauges - a large TMX-U diagnostic - has been used to measure the dynamic pressure in many of the liner-defined regions on three time scales. The natural divertor action, or plasma pump effect, of mirror plasmas has been measured using the ion gauge diagnostics on a fast time scale during operation of TMX-U with ECRH start-up. Routine operation of TMX-U is enhanced by the ability to verify the effectiveness of gettering and to locate leaks using pressure data collected on the two slow time scales. A computer code, DYNAVAC 6, which treats TMX-U as a set of conductance-coupled regions with pumping and sources in each region, has been used to successfully model the overall gas dynamics during all phases of TMX-U operation.

Pickles, W.L.; Carter, M.R.; Clower, C.A.; Drake, R.P.; Hunt, A.L.; Simonen, T.C.; Turner, W.C.

1982-11-12

126

Tailored supersonic gas jets for laser plasma accelerators  

NASA Astrophysics Data System (ADS)

Petawatt class lasers have been used to demonstrate acceleration of electron bunches to ˜1-3GeV energy over distances of ˜10-30mm, an accelerating gradient of ˜100GeV/m. Present gas jets have lengths of only 2-4 mm at densities of 10^19 cm-3, sufficient for self trapping and electron acceleration to energies up to ˜150 MeV. Capillary structures 3 cm long have been used to accelerate beams up to 1 GeV. Several concepts have been suggested that use tailored gas density distributions to enhnace the laser plasma acceleration. Stepped profiles (high density followed by lower density) have been suggested in which the short and dense region acts as a nonlinear lens, followed by the lower density and long plateau in which background electrocn are trapped and accelerated by a nonlinear laser wakefield. Other profiles have been suggested to keep the electrons in phase with the wakefield and thereby increase energy and charge in the bunch. Such tailored gas profiles require innovative supersonic gas nozzles, the design of some of which are described. The nozzle flows are mapped using a laser interferometer. The non-axisymmetric density profiles demand multiple measurements at many angles around the azimuth and tomographic reconstruction techniques. S.Y. Kalmykov et al., Plasma Phys. Control. Fusion 53(2011). W. Rittershofer et al., PHYSICS OF PLASMAS 17, 063104, 2010.

Madden, Robert; Krishnan, Mahadevan; Baudisch, Bastian; Bures, Brian; Wilson-Elliot, Kristi; Coleman, Philip

2012-10-01

127

Modeling of non-thermal plasma in flammable gas mixtures  

NASA Astrophysics Data System (ADS)

An idea of using plasma-assisted methods of fuel ignition is based on non-equilibrium generation of chemically active species that speed up the combustion process. It is believed that gain in energy consumed for combustion acceleration by plasmas is due to the non-equilibrium nature of discharge plasma, which allows radicals to be produced in an above-equilibrium amount. Evidently, the size of the effect is strongly dependent on the initial temperature, pressure, and composition of the mixture. Of particular interest is comparison between thermal ignition of a fuel-air mixture and non-thermal plasma initiation of the combustion. Mechanisms of thermal ignition in various fuel-air mixtures have been studied for years, and a number of different mechanisms are known providing an agreement with experiments at various conditions. The problem is -- how to conform thermal chemistry approach to essentially non-equilibrium plasma description. The electric discharge produces much above-equilibrium amounts of chemically active species: atoms, radicals and ions. The point is that despite excess concentrations of a number of species, total concentration of these species is far below concentrations of the initial gas mixture. Therefore, rate coefficients for reactions of these discharge produced species with other gas mixture components are well known quantities controlled by the translational temperature, which can be calculated from the energy balance equation taking into account numerous processes initiated by plasma. A numerical model was developed combining traditional approach of thermal combustion chemistry with advanced description of the plasma kinetics based on solution of electron Boltzmann equation. This approach allows us to describe self-consistently strongly non-equilibrium electric discharge in chemically unstable (ignited) gas. Equations of pseudo-one-dimensional gas dynamics were solved in parallel with a system of thermal chemistry equations, kinetic equations for charged particles (electrons, positive and negative ions), and with the electric circuit equation. The electric circuit comprises power supply, ballast resistor connected in series with the discharge and capacity. Rate coefficients for electron-assisted reactions were calculated from solving the two-term spherical harmonic expansion of the Boltzmann equation. Such an approach allows us to describe influence of thermal chemistry reactions (burning) on the discharge characteristics. Results of comparison between the discharge and thermal ignition effects for mixtures of hydrogen or ethylene with dry air will be reported. Effects of acceleration of ignition by discharge plasma will be analyzed. In particular, the role of singlet oxygen produced effectively in the discharge in ignition speeding up will be discussed.

Napartovich, A. P.; Kochetov, I. V.; Leonov, S. B.

2008-07-01

128

Ethylene Oxide Gaseous Sterilization  

PubMed Central

The duration of the equilibration period between admission of water vapor and subsequent introduction of gaseous ethylene oxide to an evacuated sterilizer chamber was studied with respect to its effect on the inactivation of spores of Bacillus subtilis var. niger under simulated practical conditions. Introduction of a water-adsorbing cotton barrier between the spores and an incoming gas mixture of water vapor and ethylene oxide caused a marked increase in the observed thermochemical death time of the spore populations. This effect was negated by admission of water vapor one or more minutes prior to introduction of ethylene oxide gas. Increases in temperature and relative humidity of the system promoted passage of water vapor through the cotton barriers and diminished their effect. PMID:13890660

Ernst, Robert R.; Shull, James J.

1962-01-01

129

Modeling and Data Needs of Atmospheric Pressure Gas Plasma and Biomaterial Interaction  

NASA Astrophysics Data System (ADS)

Non-thermal atmospheric pressure plasmas have received considerable attention recently. One promising application of non-thermal plasma devices appears to be biomaterial and biomedical treatment. Various biological and medical effects of non-thermal plasmas have been observed by a variety of investigators, including bacteria sterilization, cell apoptosis, and blood coagulation, among others. The mechanisms of the plasma-biomaterial interaction are however only poorly understood. A central scientific challenge is therefore how to answer the question: "What plasma-generated agents are responsible for the observed biological effects?" Our modeling efforts are motivated by this question. In this paper, we review our modeling results of the plasma needle discharge. Then, we address data needs for further modeling and understanding of plasma-biomaterial interaction

Sakiyama, Yukinori; Graves, David B.

2009-05-01

130

Modeling and Data Needs of Atmospheric Pressure Gas Plasma and Biomaterial Interaction  

SciTech Connect

Non-thermal atmospheric pressure plasmas have received considerable attention recently. One promising application of non-thermal plasma devices appears to be biomaterial and biomedical treatment. Various biological and medical effects of non-thermal plasmas have been observed by a variety of investigators, including bacteria sterilization, cell apoptosis, and blood coagulation, among others. The mechanisms of the plasma-biomaterial interaction are however only poorly understood. A central scientific challenge is therefore how to answer the question: 'What plasma-generated agents are responsible for the observed biological effects?' Our modeling efforts are motivated by this question. In this paper, we review our modeling results of the plasma needle discharge. Then, we address data needs for further modeling and understanding of plasma-biomaterial interaction.

Sakiyama, Yukinori; Graves, David B. [Department of Chemical Engineering, University of California at Berkeley, Berkeley, CA 94720 (United States)

2009-05-02

131

Classical transport equations for burning gas-metal plasmas  

NASA Astrophysics Data System (ADS)

Thermonuclear inertial confinement fusion plasmas confined by a heavy metal shell may be subject to the mixing of metal into the gas with a resulting degradation of fusion yield. Classical plasma diffusion driven by a number of gradients can provide a physical mechanism to produce atomic mix, possibly in concert with complex hydrodynamic structures and/or turbulence. This paper gives a derivation of the complete dissipative plasma hydrodynamics equations from kinetic theory, for a binary ionic mixture plasma consisting of electrons, e, a light (hydrogenic gas) ion species, i, and a heavy, high ZI plasma metal species, I. A single mean ionization state for the heavy metal, ZI, is assumed to be provided by some independent thermodynamic model of the heavy metal Z I = Z I ( n i , n I , T e ). The kinetic equations are solved by a generalized Chapman-Enskog expansion that assumes small Knudsen numbers for all species: N K e ? ? e / L ? 1 , N K i ? ? i / L ? 1. The small electron to ion mass ratio, m e / m i ? 1, is utilized to account for electron-ion temperature separation, T e ? T i, and to decouple the electron and ion transport coefficient calculations. This produces a well ordered perturbation theory for the electrons, resulting in the well known "Spitzer" problem of Spitzer and collaborators and solved independently by Braginskii. The formulation in this paper makes clear the inherent symmetry of the transport and gives an analytic solution for all values of the effective charge Z eff, including Z eff < 1. The electron problem also determines the ambipolar electric field and the "thermal forces" on both ion species that are needed for the ion kinetic solution. The ion transport problem makes use of the small mass ratio between ion species, m i / m I ? 1, to identify an "ion Spitzer problem" that is mathematically identical to that for the electrons but with different thermodynamic forces. The ionic scattering parameter, ? I ? n I Z I 2 / n i, replaces the Z eff of the electron problem, but has an extended domain, 0? ? I < ?, to cover all mixture fractions from the pure gas to the pure metal plasma. The extension of the Spitzer problem to include this extended domain is given in this work. The resulting transport equations for the binary gas-metal plasma mixture are complete and accurate through second order. All transport coefficients are provided in analytic form.

Molvig, Kim; Simakov, Andrei N.; Vold, Erik L.

2014-09-01

132

Mobility in a strongly coupled dusty plasma with gas.  

PubMed

The mobility of a charged projectile in a strongly coupled dusty plasma is simulated. A net force F, opposed by a combination of collisional scattering and gas friction, causes projectiles to drift at a mobility-limited velocity up. The mobility ?p=up/F of the projectile's motion is obtained. Two regimes depending on F are identified. In the high-force regime, ?p?F0.23, and the scattering cross section ?s diminishes as up-6/5. Results for ?s are compared with those for a weakly coupled plasma and for two-body collisions in a Yukawa potential. The simulation parameters are based on microgravity plasma experiments. PMID:24827355

Liu, Bin; Goree, J

2014-04-01

133

Mobility in a strongly coupled dusty plasma with gas  

E-print Network

The mobility of a charged projectile in a strongly coupled dusty plasma is simulated. A net force $F$, opposed by a combination of collisional scattering and gas friction, causes projectiles to drift at a mobility-limited velocity $u_p$. The mobility $\\mu_p=u_p/F$ of the projectile's motion is obtained. Two regimes depending on $F$ are identified. In the high force regime, $\\mu_p \\propto F^{0.23}$, and the scattering cross section $\\sigma_s$ diminishes as $u_p^{-6/5}$. Results for $\\sigma_s$ are compared with those for a weakly coupled plasma and for two-body collisions in a Yukawa potential. The simulation parameters are based on microgravity plasma experiments.

Liu, Bin

2014-01-01

134

Ultra-Intense Laser Pulse Propagation in Gas and Plasma  

SciTech Connect

It is proposed here to continue their program in the development of theories and models capable of describing the varied phenomena expected to influence the propagation of ultra-intense, ultra-short laser pulses with particular emphasis on guided propagation. This program builds upon expertise already developed over the years through collaborations with the NSF funded experimental effort lead by Professor Howard Milchberg here at Maryland, and in addition the research group at the Ecole Polytechnique in France. As in the past, close coupling between theory and experiment will continue. The main effort of the proposed research will center on the development of computational models and analytic theories of intense laser pulse propagation and guiding structures. In particular, they will use their simulation code WAKE to study propagation in plasma channels, in dielectric capillaries and in gases where self focusing is important. At present this code simulates the two-dimensional propagation (radial coordinate, axial coordinate and time) of short pulses in gas/plasma media. The plasma is treated either as an ensemble of particles which respond to the ponderomotive force of the laser and the self consistent electric and magnetic fields created in the wake of pulse or as a fluid. the plasma particle motion is treated kinetically and relativistically allowing for study of intense pulses that result in complete cavitation of the plasma. The gas is treated as a nonlinear medium with rate equations describing the various stages of ionization. A number of important physics issues will be addressed during the program. These include (1) studies of propagation in plasma channels, (2) investigation of plasma channel nonuniformities caused by parametric excitation of channel modes, (3) propagation in dielectric capillaries including harmonic generation and ionization scattering, (4) self guided propagation in gas, (5) studies of the ionization scattering instability recently identified theoretically and experimentally in the group, and (6) studies of propagation in cluster plasmas. New models will be developed for the harmonic generation of radiation and these will be incorporated in the modeling and simulation.

Antonsen, T. M.

2004-10-26

135

Temperature gradient effects on the neutral gas penetration into a magnetized plasma  

Microsoft Academic Search

Experimental evidence of temperature gradient effects on the neutral gas penetration into a plasma is summarized. An increased temperature gradient reduces the neutral gas content in the partially ionized boundary layer of a cold gas blanket system. A strong modification of the rotation plasma equilibrium is then observed. Such an equilibrium is a sensitive function of the neutral gas concentration

M. Bures

1982-01-01

136

Terahertz-Radiation-Enhanced Emission of Fluorescence from Gas Plasma  

SciTech Connect

We report the study of femtosecond laser-induced air plasma fluorescence under the illumination of terahertz (THz) pulses. Semiclassical modeling and experimental verification indicate that time-resolved THz radiation-enhanced emission of fluorescence is dominated by the electron kinetics and the electron-impact excitation of gas molecules or ions. We demonstrate that the temporal waveform of the THz field could be retrieved from the transient enhanced fluorescence, making omnidirectional, coherent detection available for THz time-domain spectroscopy.

Liu Jingle; Zhang, X.-C. [Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

2009-12-04

137

Plasma\\/neutral gas transport in divertors and limiters  

Microsoft Academic Search

The engineering design of the divertor and first wall region of fusion reactors requires accurate knowledge of the energies and particle fluxes striking these surfaces. Simple calculations indicate that approx. 10 MW\\/m(2) heat fluxes and approx. 1 cm\\/yr erosion rates are possible, but there remain fundamental physics questions that bear directly on the engineering design. Hydrogen plasma and neutral gas

P. J. Gierszewski

1983-01-01

138

Gas Contamination In Plasma-Arc-Welded Aluminum  

NASA Technical Reports Server (NTRS)

Document describes experimental investigation on visible and tactile effects of gaseous contaminants in variable-polarity plasma arc (VPPA) welding of 2219 T-87 aluminum alloy. Contaminant gases (nitrogen, methane, oxygen, and hydrogen) introduced in argon arc and in helium shield gas in various controlled concentrations. Report represents results of experiments in form of photographs of fronts, backs, polished cross sections, and etched cross sections of welds made with various contaminants at various concentrations. Provides detailed discussion of conditions under which welds made.

Mcclure, John C.; Torres, Martin R.; Gurevitch, Alan C.; Newman, Robert A.

1992-01-01

139

Design and Preliminary Performance Testing of Electronegative Gas Plasma Thruster  

NASA Technical Reports Server (NTRS)

In classical gridded electrostatic ion thrusters, positively charged ions are generated from a plasma discharge of noble gas propellant and accelerated to provide thrust. To maintain overall charge balance on the propulsion system, a separate electron source is required to neutralize the ion beam as it exits the thruster. However, if high-electronegativity propellant gases (e.g., sulfur hexafluoride) are instead used, a plasma discharge can result consisting of both positively and negatively charged ions. Extracting such electronegative plasma species for thrust generation (e.g., with time-varying, bipolar ion optics) would eliminate the need for a separate neutralizer cathode subsystem. In addition for thrusters utilizing a RF plasma discharge, further simplification of the ion thruster power system may be possible by also using the RF power supply to bias the ion optics. Recently, the PEGASES (Plasma propulsion with Electronegative gases) thruster prototype successfully demonstrated proof-of-concept operations in alternatively accelerating positively and negatively charged ions from a RF discharge of a mixture of argon and sulfur hexafluoride.i In collaboration with NASA Marshall Space Flight Center (MSFC), the Georgia Institute of Technology High-Power Electric Propulsion Laboratory (HPEPL) is applying the lessons learned from PEGASES design and testing to develop a new thruster prototype. This prototype will incorporate design improvements and undergo gridless operational testing and diagnostics checkout at HPEPL in April 2014. Performance mapping with ion optics will be conducted at NASA MSFC starting in May 2014. The proposed paper discusses the design and preliminary performance testing of this electronegative gas plasma thruster prototype.

Liu, Thomas M.; Schloeder, Natalie R.; Walker, Mitchell L. R.; Polzin, Kurt A.; Dankanich, John W.; Aanesland, Ane

2014-01-01

140

The economics of sterilization.  

PubMed

In this approach to selecting the most appropriate sterilization method, comparisons are made of the initial and ongoing costs for sterilization by ethylene oxide, gamma radiation, and electron radiation. Considerations that have an impact on cost include the monetary value of the time that elapses between sending a product for processing and its release for sale, anticipated growth in the level of product to be sterilized, labour, electricity and utilities, and the price of the sterilant. PMID:10155389

Brinston, R M

1995-06-01

141

Dynamic characteristics of gas-water interfacial plasma under water  

SciTech Connect

Gas-water interfacial plasmas under water were generated in a compact space in a tube with a sandglass-like structure, where two metal wires were employed as electrodes with an applied 35 kHz ac power source. The dynamic behaviors of voltage/current were investigated for the powered electrode with/without water cover to understand the effect of the gas-water interface. It is found that the discharge exhibits periodic pulsed currents after breakdown as the powered electrode is covered with water, whereas the electrical current reveals a damped oscillation with time with a frequency about 10{sup 6} Hz as the powered electrode is in a vapor bubble. By increasing water conductivity, a discharge current waveform transition from pulse to oscillation presents in the water covering case. These suggest that the gas-water interface has a significant influence on the discharge property.

Zheng, S. J.; Zhang, Y. C.; Ke, B.; Ding, F.; Tang, Z. L.; Yang, K.; Zhu, X. D. [Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2012-06-15

142

ISO radiation sterilization standards  

NASA Astrophysics Data System (ADS)

This presentation provides an overview of the current status of the ISO radiation sterilization standards. The ISO standards are voluntary standards which detail both the validation and routine control of the sterilization process. ISO 11137 was approved in 1994 and published in 1995. When reviewing the standard you will note that less than 20% of the standard is devoted to requirements and the remainder is guidance on how to comply with the requirements. Future standards developments in radiation sterilization are being focused on providing additional guidance. The guidance that is currently provided in informative annexes of ISO 11137 includes: device/packaging materials, dose setting methods, and dosimeters and dose measurement, currently, there are four Technical Reports being developed to provide additional guidance: 1. AAMI Draft TIR, "Radiation Sterilization Material Qualification" 2. ISO TR 13409-1996, "Sterilization of health care products — Radiation sterilization — Substantiation of 25 kGy as a sterilization dose for small or infrequent production batches" 3. ISO Draft TR, "Sterilization of health care products — Radiation sterilization Selection of a sterilization dose for a single production batch" li]4. ISO Draft TR, "Sterilization of health care products — Radiation sterilization-Product Families, Plans for Sampling and Frequency of Dose Audits."

Lambert, Byron J.; Hansen, Joyce M.

1998-06-01

143

Quantification of ethylene chlorohydrin and ethylene glycol as potential reaction products in gas-sterilized medical-grade plastics.  

PubMed

A gas chromatographic procedure is described for the quantitative determinations of ethylene chlorohydrin and ethylene glycol in disposable medical-grade plastics. Both components are isolated by solvent extraction. The lower limit of detection is 1 p.p.m. of ethylene chlorohydrin and 2 p.p.m. of ethylene glycol. Propylene glycol is used as an internal standard. Ethylene oxide residues have to be removed prior to the assay. PMID:3711360

De Rudder, D; De Graeve, E; Van Severen, R; Braeckman, P

1986-04-01

144

IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 34, NO. 3, JUNE 2006 755 Nonequilibrium EEDF in Gas Discharge Plasmas  

E-print Network

by an electron beam, where electron ac- celeration takes place in an electron gun outside the plasma. A wellIEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 34, NO. 3, JUNE 2006 755 Nonequilibrium EEDF in Gas Discharge Plasmas Valery A. Godyak, Fellow, IEEE Abstract--Nonequilibrium effects associated with spatial

Kaganovich, Igor

145

Proper monitoring of sterilization procedures used in oral surgery.  

PubMed

The sterilization procedures used by oral surgeons in Norway have been surveyed. In 22 of the 25 oral surgical clinics controlled, instruments were sterilized by saturated steam at 121 degrees C or 134 degrees C; 3 used a dry heat oven sterilizer; dry heat and/or gas sterilization procedures supplemented steam sterilization in 17 clinics. When these sterilization procedures were monitored with biological indicators, 5 autoclaves (challenged with B. stearothermophilus spores), 2 dry heat sterilizers (B. subtilis spores), and all the Harvey Chemiclaves tested (B. subtilis spores) did not inactivate the bacterial spores. A biological monitoring system that fulfills the valid requirements for sterilization procedures given by the national health authorities and that is reliable, convenient, economical and self-contained should be used routinely in oral surgery clinics. PMID:6411637

Skaug, N

1983-06-01

146

Observation of tritium in gas/plasma loaded titanium samples  

NASA Astrophysics Data System (ADS)

The observation of significant neutron yield from gas loaded titanium samples at Frascati in April 1989 opened up an alternate pathway to the investigation of anomalous nuclear phenomena in deuterium/solid systems, complimenting the electrolytic approach. Since then at least six different groups have successfully measured burst neutron emission from deuterated titanium shavings following the Frascati methodology, the special feature of which was the use of liquid nitrogen to create repeated thermal cycles resulting in the production of non-equilibrium conditions in the deuterated samples. At Trombay several variations of the gas loading procedure have been investigated including induction heating of single machined titanium targets in a glass chamber as well as use of a plasma focus device for deuteriding its central titanium electrode. Stemming from earlier observations both at BARC and elsewhere that tritium yield is ?108 times higher than neutron output in cold fusion experiments, we have channelised our efforts to the search for tritium rather than neutrons. The presence of tritium in a variety gas/plasma loaded titanium samples has been established successfully through a direct measurement of the radiations emitted as a result of tritium decay, in contradistinction to other groups who have looked for tritium in the extracted gases. In some samples we have thus observed tritium levels of over 10 MBq with a corresponding (t/d) ratio of ?10-5.

Srinivasan, M.; Shyam, A.; Kaushik, T. C.; Rout, R. K.; Kulkarni, L. V.; Krishnan, M. S.; Malhotra, S. K.; Nagvenkar, V. G.; Iyengar, P. K.

1991-05-01

147

Investigation of the laser-induced plasma produced in a gas-filled chamber and in a gas jet  

Microsoft Academic Search

In the current study, characteristics of the laser-induced plasma were investigated in a gas filled chamber or in a gas jet by using a relatively low intensity laser (I <= 5 x 1012 W\\/cm2). Temporal evolutions of the produced plasma were measured using the shadow visualization and the shock wave propagation as well as the electron density profiles in the

Jong-Uk Kim; Gaung-Hoon Kim; Hyyong Suk

2003-01-01

148

Experimental Evidence of Temperature Gradient Effects on the Neutral Gas Penetration into a Magnetized Rotating Plasma  

Microsoft Academic Search

The experimental evidence of temperature gradient effects on the neutral gas penetration into a plasma is presented. It is found that an increased temperature gradient reduces the neutral gas content in the partially ionized boundary layer of a cold gas blanket system. A strong modification of the rotating plasma equilibrium is then observed. Such an equilibrium is a sensitive function

M. Bures

1983-01-01

149

On the use of gas jet targets for laser plasma interaction physics with nanosecond laser pulses  

Microsoft Academic Search

The implementation of gas jet targets appears to be a very attractive alternative to pre-exploded thin foils targets for relativistic laser plasma interactions. In this article, we report a review of recent results obtained by focusing a nanosecond laser beam onto a gas jet target. The benefit of gas jet targets for the generation of homogeneous and large scale plasmas,

V. Malka

2006-01-01

150

Nucleation and growth of Nb nanoclusters during plasma gas condensation  

SciTech Connect

Niobium nanoclusters were produced using a plasma gas condensation process. The influence of gas flow rate, aggregation length, and source current on the nanocluster nucleation and growth were analyzed. Nanoclusters with an average diameter from 4 nm to 10 nm were produced. Cluster size and concentration were tuned by controlling the process inputs. The effects of each parameter on the nucleation zone, growth length, and residence time was examined. The parameters do not affect the cluster formation and growth independently; their influence on cluster formation can be either cumulative or competing. Examining the nucleation and growth over a wide combination of parameters provided insight into their interactions and the impact on the growth process. These results provide the opportunity for a broader understanding into the nucleation and growth of nanoclusters and some insights into how process parameters interact during deposition. This knowledge will enhance the ability to create nanoclusters with desired size dispersions.

Bray, K. R.; Jiao, C. Q. [UES, Inc., 4401 Dayton-Xenia Rd, Dayton, Ohio 45432 (United States)] [UES, Inc., 4401 Dayton-Xenia Rd, Dayton, Ohio 45432 (United States); DeCerbo, J. N. [Air Force Research Laboratory, AFRL/RQQE, 1950 Fifth St., WPAFB, Ohio 45433 (United States)] [Air Force Research Laboratory, AFRL/RQQE, 1950 Fifth St., WPAFB, Ohio 45433 (United States)

2013-06-21

151

Data Processing from Micro-Plasma Gas Analytical Sensor  

NASA Astrophysics Data System (ADS)

Theoretical consideration of signal formation at micro-plasma gas analyzer based on Collisional Electron Spectroscopy (CES) and experimental results on CES sensor are presented. It is demonstrated that a diffusion path confinement for characteristic electrons provides a possibility to measure electrons energy distribution function (EEDF) and to find characteristic spectra of species at high (up to atmospheric) gas pressure. Simple micro-plasma CES sensor of two plane parallel electrode configuration with current-voltage measurement in afterglow discharge may be operated in two possible modes. The first mode presumes application of classic 2-nd derivative of current-voltage curve to select characteristic peaks in electron energy spectra of the species to be detected. In the case of a deeper collisional dissipation of characteristic peaks, a 3-rd derivative may be used. Said derivatives were obtained by differentiating of a spline providing least-squares approximation of current-voltage curve. Model and experimental electron energy spectra of pair He metastables collisions in dependence of inter-electrode gap are discussed.

Mustafaev, Alexander; Tsyganov, Alexander

2011-11-01

152

Modelling penetration and plasma response of a dense neutral gas jet in a post-thermal quenched plasma  

NASA Astrophysics Data System (ADS)

This paper is about the dynamics of gas jet injection and propagation into the cold, current quench (CQ) discharge following the thermal quench (TQ) phase of a disruption event. Understanding the processes involved in the interpenetration between a dense, fast-moving supersonic gas jet and a magnetized plasma is fundamental to the solution of the disruption mitigation problem using massive gas injection. An analytical model was developed that provides the penetration depth of the jet in the CQ discharge. The model developed incorporates the injector, the vacuum space between injector and plasma, and the low beta CQ plasma through which the jet penetrates. The radially moving gas stagnates at some point inside the plasma by formation of a ‘bottle shock’, resulting in a certain penetration depth. Consistent with experimental findings, it is shown that high fuelling efficiency >70% and good penetration beyond the q = 2 surface is possible in such plasma discharges, but in normal (unquenched) plasma discharges penetration of dense gas jets will be quite poor. The paper also sheds light on how the external plasma responds to allow interpenetration of perfectly insulating gas jet through a strong magnetic field B2/2?0 ? ?u2. The paper also develops semi-analytical models for the response of the cold, high-current, collision-dominated plasma to the insertion of a dense neutral jet: the propagation of cooling waves out along the magnetic field lines, the heated and ionized surface layer which also expands outwards along the magnetic field lines, and the electrical breakdown of the neutral gas within the jet volume. Although good penetration in the ITER post-TQ discharge can be achieved, the plasma resistivity is only marginally enhanced. This may render repetitive gas inject ineffective, as the concept requires a sizable resistivity enhancement to initiate a current profile contraction, and resulting kink-tearing activity to suppress runaway avalanching.

Parks, P. B.; Wu, W.

2014-02-01

153

[Sterilization of women].  

PubMed

Voluntary sterilization is a permanent method of contraception. Therefore medical counseling of patients desiring sterilization is of utmost importance and should include documented incidence of failure (i.e., pregancy), complication risks, and if necessary, the various factors influencing successful reversal, although it should be emphasized that reversal can never be guaranteed. Laproscopic sterilization has proven very successful. Comparison of the advantages and disadvantages of the most used methods appears in Table 7. The most commonly used method is bipolar electrocoagulation in the isthmic tubal section. Unipolar electrocoagulation should not be used. Hysterectomy is too major an operation to be used solely for sterilization purposes, and is indicated only when other procedures have been eliminated. Pregnancy in failed sterilizations is approximately 8-10/1000 using the current methods, and an overwhelming number of these pregnancies are extrauterine. The rate of complications is lowest in laparoscopic interval sterilizations using local anesthesia. Approximately 1% of sterilized women desired reversal, despite preoperative counseling. The success rate of reversal is most favorable when the sterilization was perfomed in the isthmic tubal section with little destruction of tissue (by the clip method), the tubal segments are long, and the time since sterilization is less than 5 years. Reversal is not possible after fimbriectomy. PMID:6489844

Hirsch, H A

1984-09-01

154

Sterilization. Disciplined microbial control.  

PubMed

The goal of instrument processing is to protect patients by preventing cross-contamination from instruments. The processing involves a series of sequential steps aimed at removing and killing microbes on contaminated instruments and maintaining those instruments in an aseptic state until they are reused. These steps must be conducted carefully to assure success and to reduce chances of disease spread or physical injury to those handling the contaminated instruments. Presoaking begins the cleaning process and facilitates terminal cleaning by ultrasonic or manual scrubbing. If instruments are not properly cleaned, subsequent sterilization may be jeopardized by insulation of blood- or saliva-coated microbes from the sterilizing agent. Items that would be destroyed by heat should be cleaned and sterilized in a properly prepared glutaraldehyde solution. Cleaned instruments must be packaged prior to heat sterilization to protect them from recontamination after sterilization and before reuse. Sterilization of cleaned, packaged instruments in steam, chemical vapor, or dry heat sterilizers must involve proper loading, processing, drying, and cooling. Routine use of spore tests and chemical indicators will provide quality assessment of packaging procedures and operation of the sterilizer, as well as assist in identifying processed packages during distribution. Using the results of sterilization monitoring to adjust procedures as a means of assuring sterilization provides quality assurance to the office staff and to the patients that the instruments have been properly processed. Carefully handling storage and distribution of the sterilized instrument packs or trays reduces the chances for recontamination until the instruments are reused. Instrument processing is a major part of the office infection control program. It must be performed in a controlled manner with proper monitoring to achieve the desired outcome of patient protection. PMID:2032579

Miller, C H

1991-04-01

155

Optimized method of producing washers of titanium hydride for plasma gun using occluded hydrogen gas  

Microsoft Academic Search

An optimized way of producing washers of titanium hydride for the application to a plasma gun using the occluded gas is presented. The amount of H2 gas (equivalently, gas pressure p) is entirely preadjusted in a gas reservoir of a simple instrument. The temperature T of a furnace is completely feedback controlled. Data show that when p is the order

H. Himura; Y. Saito; A. Sanpei; S. Masamune; N. Takeuchi; T. Shiono

2006-01-01

156

Initial experiments of RF gas plasma source for heavy ionfusion  

SciTech Connect

The Source Injector Program for the US Heavy Ion Fusion Virtual National Laboratory is currently exploring the feasibility of using RF gas plasma sources for a HIF driver. This source technology is presently the leading candidate for the multiple aperture concept, in which bright millimeter size beamlets are extracted and accelerated electrostatically up to 1 MeV before the beamlets are allowed to merge and form 1 A beams. Initial experiments have successfully demonstrated simultaneously high current density, {approx} 100 mA/cm{sup 2} and fast turn on, {approx} 1 {micro}s. These experiments were also used to explore operating ranges for pressure and RF power. Results from these experiments are presented as well as progress and plans for the next set of experiments for these sources.

Ahle, L.; Hall, R.; Molvik, A.W.; Chacon-Golcher, E.; Kwan, J.W.; Leung, K.N.; Reijonen, J.

2002-05-22

157

Microbiological aspects of Radiation Sterilization  

E-print Network

on showing that microorganisms can be killed as they occur on or in product units. Sect 1.2.3: The use -nutrients - etc..... #12;13 Sterilization Definition of "sterilization" in EN 556-1: Sterilization

158

Collisional diffusion in a two-dimensional point vortex gas or a two-dimensional plasma  

E-print Network

Collisional diffusion in a two-dimensional point vortex gas or a two-dimensional plasma Daniel H. E of a multispecies two-dimensional 2D point vortex gas, or a 2D plasma, in the presence of retrograde shear of point vortices, Onsager relations require that the diffusive flux conserves the total vorticity (r

California at San Diego, University of

159

Wool treatment in the gas flow from gliding discharge plasma at atmospheric pressure  

Microsoft Academic Search

A new method of wool plasma surface treatment at atmospheric pressure employing the stable gas flow excited in gliding electrical discharge (called GlidArc) has been developed. The plasma from a small space between electrodes is drifted by the gas flow into a conic space, towards the base of which, the treated combed top moves. The subjective handle of the treated

J. Jan?a; A. Czernichowski

1998-01-01

160

Improved Back-Side Purge-Gas Chambers For Plasma Arc Welding  

NASA Technical Reports Server (NTRS)

Improved chambers for inert-gas purging of back sides of workpieces during plasma arc welding in keyhole (full-penetration) mode based on concept of directing flows of inert gases toward, and concentrating them on, hot weld zones. Tapered chamber concentrates flow of inert gas on plasma arc plume and surrounding metal.

Ezell, Kenneth G.; Mcgee, William F.; Rybicki, Daniel J.

1995-01-01

161

An enhancement of plasma density by neutral gas injection observed in SEPAC Spacelab-1 experiment  

NASA Technical Reports Server (NTRS)

An enhancement of plasma density observed during a neutral gas injection in Space Experiments with Particle Accelerators by the Space Shuttle/Spacelab-1 is presented. When a plume of nitrogen gas was injected from the orbiter into space, a large amount of plasma was detected by an onboard plasma probe. The observed density often increased beyond the background plasma density and was strongly dependent on the attitude of the orbiter with respect to the velocity vector. This effect has been explained by a collisional interaction between the injected gas molecules and the ionospheric ions relatively drifting at the orbital speed.

Sasaki, S.; Kawashima, N.; Kuriki, K.; Yanagisawa, M.; Obayashi, T.; Kubota, S.; Roberts, W. T.; Reasoner, D. L.; Taylor, W. W. L.; Williamson, P. R.

1985-01-01

162

Isolation and derivatization of plasma taurine for stable isotope analysis by gas chromatography-mass spectrometry  

Microsoft Academic Search

A method for the isolation and derivatization of plasma taurine is described that allows stable isotope determinations of taurine to be made by gas chromatography-mass spectrometry. The isolation procedure can be applied to 0.1 ml of plasma; the recovery of plasma taurine was 70 to 80%. For gc separation, taurine was converted to its dimethylaminomethylene methyl ester derivative which could

C. S. Irving; P. D. Klein

1980-01-01

163

Atomic Force Microscope Investigations of Biofilm-Forming Bacterial Cells Treated with Gas Discharge Plasmas  

NASA Astrophysics Data System (ADS)

We present investigations of biofilm-forming bacteria before and after treatment from gas discharge plasmas. Gas discharge plasmas represent a way to inactivate bacteria under conditions where conventional disinfection methods are often ineffective. These conditions involve bacteria in biofilm communities, where cooperative interactions between cells make organisms less susceptible to standard killing methods. Chromobacterium violaceum were imaged before and after plasma treatment using an atomic force microscope (AFM). After 5 min. plasma treatment, 90% of cells were inactivated, that is, transformed to non-culturable cells. Results for cell surface morphology and micromechanical properties for plasma treatments lasting from 5 to 60 minutes were obtained and will be presented.

Vandervoort, Kurt; Renshaw, Andrew; Abramzon, Nina; Brelles-Marino, Graciela

2009-03-01

164

Comparing the equivalent particle number density distribution of gas and plasma flow fields.  

PubMed

In this paper, the equivalent particle number density distribution of gas and plasma flow fields is investigated. For the purpose of facilitating comparison, argon gas and argon arc plasma are chosen as practical examples for experiment. The equivalent particle number density distributions of the argon gas and argon arc plasma are reconstructed from the experimentally measured refractive index distributions obtained by moiré tomography, while five cross sections, which are 7, 8.5, 10, 11.5, and 13 mm away from the jet nozzle are chosen for practical calculation and comparison. In experiment, the probe wavelength and the export pressure of argon gas and argon arc plasma are the same. The experimental results manifest that (1) the equivalent particle number density decreases with the distance away from the jet nozzle of the gas flow field, while (2) the equivalent particle number density of the plasma flow field has a different variation. Finally, the experimental results are theoretically explained and analyzed. PMID:23669673

Chen, Yun-yun; Zhang, Ying-ying; Zhang, Cheng-yi; Li, Zhen-hua

2013-04-20

165

Direct Injection Multi-Gas Inductively Coupled Plasma Source for Industrial Applications  

Microsoft Academic Search

Summary form only given. A new direct injection multi-gas inductively coupled plasma (ICP) source is developed. With the new ICP source, not only Ar but He, O2, N2, CO2, air and their mixture gas plasma can be stably generated in the atmospheric pressure. Furthermore, aqueous solutions can be introduced directly into the plasmas using common pneumatic nebulizer. To generate molecular

Akitoshi Okino; Hidekazu Miyahara; Takayuki Doi; Yoichi Mizusawa; Eiki Hotta

2005-01-01

166

Radiation from high-intensity ultrashort-laser-pulse and gas-jet magnetized plasma interaction  

Microsoft Academic Search

Using a gas-jet flow, via the interaction between an ultrashort high-intensity laser pulse and plasma in the presence of a perpendicular external dc magnetic field, the short pulse radiation from a magnetized plasma wakefield has been observed. Different nozzles are used in order to generate different densities and gas profiles. The neutral density of the gas-jet flow measured with a

Davoud Dorranian; Mikhail Starodubtsev; Hiromichi Kawakami; Hiroaki Ito; Noboru Yugami; Yasushi Nishida

2003-01-01

167

Combining non-thermal plasma with heterogeneous catalysis in waste gas treatment: A review  

Microsoft Academic Search

Plasma driven catalysis is a promising technology for waste gas treatment characterized by higher energy efficiencies, high mineralization rates and low by-product formation. The combination of heterogeneous catalysts with non-thermal plasma can be operated in two configurations: positioning the catalyst in the discharge zone (in-plasma catalysis) or downflow the discharge zone (post plasma catalysis).In a first part of the review,

Jim Van Durme; Jo Dewulf; Christophe Leys; Herman Van Langenhove

2008-01-01

168

Measurements of Plasma Expansion due to Background Gas in the Electron Diffusion Gauge Experiment  

SciTech Connect

The expansion of pure electron plasmas due to collisions with background neutral gas atoms in the Electron Diffusion Gauge (EDG) experiment device is observed. Measurements of plasma expansion with the new, phosphor-screen density diagnostic suggest that the expansion rates measured previously were observed during the plasma's relaxation to quasi-thermal-equilibrium, making it even more remarkable that they scale classically with pressure. Measurements of the on-axis, parallel plasma temperature evolution support the conclusion.

Kyle A. Morrison; Stephen F. Paul; Ronald C. Davidson

2003-08-11

169

Quantifying the effect of resin type and sterilization method on the degradation of ultrahigh molecular weight polyethylene after 4 years of real-time shelf aging.  

PubMed

Alternative sterilization methods including ethylene oxide, gas plasma, and gamma-radiation in an inert environment were implemented in the late 1990s, to limit oxidative degradation of ultrahigh molecular weight polyethylene (PE). There was also a simultaneous transition to PE resins that did not contain calcium stearate. Shelf storage duration of PE inserts following gamma-irradiation in air has been correlated to poor clinical performance and increased wear. This study aimed to determine how sterilization method and resin type influenced degradation of PE after 4 years of real-time shelf aging. It was hypothesized that gamma-irradiation and stearate containing resins would incur significantly more degradation than nonradiated, stearate-free resins. Gamma-irradiated PE samples in air and nitrogen had a significantly increased density and oxidation index, compared to nonirradiated PE after 4 years of shelf aging. Alternative sterilization methods such as ethylene oxide and gas plasma appeared to have significantly less oxidation regardless of PE resin type. A partial correlation demonstrated that density and oxidation index were not correlated (r(2) = 0.079) when examining the influence of sterilization method. The data supported that after 4 years of real-time shelf aging, the type of sterilization method had a larger influence on PE degradation than resin type. PMID:15127395

Willie, Bettina M; Ashrafi, Shadi; Alajbegovic, Sanjin; Burnett, Trever; Bloebaum, Roy D

2004-06-01

170

Effects of rf-bias power on plasma parameters in a low gas pressure inductively coupled plasma  

SciTech Connect

Remarkable changes of the electron temperature and the plasma density by increasing bias power were observed in low gas pressure inductively coupled plasma (ICP) by the measurement of electron energy distribution function (EEDF). As the bias power increases, the electron temperature increased with accompanying the evolution of the EEDF from a bi-Maxwellian to a Maxwellian distribution. However, a different trend of the plasma density was observed with a dependence on the ICP powers. When the ICP power was relatively small or the discharge is in capacitive mode (E mode), the plasma density increased considerably with the bias power, while decrease of the plasma density was observed when the discharge is in inductive mode (H mode). The change of the plasma density can be explained by the balance between total power absorption and power dissipation.

Lee, Hyo-Chang; Lee, Min-Hyong; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

2010-02-15

171

An argon-nitrogen-hydrogen mixed-gas plasma as a robust ionization source for inductively coupled plasma mass spectrometry  

NASA Astrophysics Data System (ADS)

Multivariate optimization of an argon-nitrogen-hydrogen mixed-gas plasma for minimum matrix effects, while maintaining analyte sensitivity as much as possible, was carried out in inductively coupled plasma mass spectrometry. In the presence of 0.1 M Na, the 33.9 ± 3.9% (n = 13 elements) analyte signal suppression on average observed in an all-argon plasma was alleviated with the optimized mixed-gas plasma, the average being - 4.0 ± 8.8%, with enhancement in several cases. An addition of 2.3% v/v N2 in the outer plasma gas, and 0.50% v/v H2 to the central channel, as a sheath around the nebulizer gas flow, was sufficient for this drastic increase in robustness. It also reduced the background from ArO+ and Ar2+ as well as oxide levels by over an order of magnitude. On the other hand, the background from NO+ and ArN+ increased by up to an order of magnitude while the levels of doubly-charged ions increased to 7% (versus 2.7% in an argon plasma optimized for sensitivity). Furthermore, detection limits were generally degraded by 5 to 15 fold when using the mixed-gas plasma versus the argon plasma for matrix-free solution (although they were better for several elements in 0.1 M Na). Nonetheless, the drastically increased robustness allowed the direct quantitative multielement analysis of certified ore reference materials, as well as the determination of Mo and Cd in seawater, without using any matrix-matching or internal standardization.

Makonnen, Yoseif; Beauchemin, Diane

2014-09-01

172

Further development of plasma electron gun for operation at forepump gas pressure  

Microsoft Academic Search

The hollow cathode plasma electron gun was designed especially for operation at forepump (up to 0.1 Torr) gas pressure. This work is devoted to investigation of maximum values of gas pressure and accelerating voltage It was established, that the maximum. operation gas pressure as well as the electron accelerating voltage increased with the smaller emission mesh size, shorter accelerating gap

Y. Burachevsky; V. Burdovitsin; D. Danilishin; A. Mytnikov; E. Oks

2001-01-01

173

Gas flow driven by thermal creep in dusty plasma T. M. Flanagan and J. Goree  

E-print Network

2009 Thermal creep flow TCF is a flow of gas driven by a temperature gradient along a solid boundary temperature gradient along a solid boundary. Since gas flows along the boundary, TCF is very different fromGas flow driven by thermal creep in dusty plasma T. M. Flanagan and J. Goree Department of Physics

Goree, John

174

Pulsed-plasma treatment of polluted gas using wet-\\/low-temperature corona reactors  

Microsoft Academic Search

Application of pulsed plasma for gas cleaning is gaining prominence in recent years, mainly from the energy consideration point of view. Normally, the gas treatment is carried out at or above room temperature by the conventional dry-type corona reactor. However, this treatment is still inadequate for the removal of certain stable gases present in the exhaust\\/flue gas mixture. The authors

Kazuo Shimizu; Katsuhiro Kinoshita; Ken-ya Yanagihara; B. S. Rajanikanth; Shinji Katsura; Akira Mizuno

1997-01-01

175

Sterilization by Laparoscopy  

MedlinePLUS

... or blocked with scar tissue formed by small implants. Tubal sterilization prevents the sperm from reaching the ... scar tissue formed by the insertion of small implants, preventing sperm from entering the fallopian tubes to ...

176

Particle Dynamics in Neutral-Gas Confined Laser-Produced Plasmas  

NASA Astrophysics Data System (ADS)

Laser-produced plasma from a metallic target can be confined to higher plasma densities by immersing the target in an inert gas medium at increasingly high density. The plasma becomes Rayleigh-Taylor unstable, however, when the mass density of the neutral gas exceeds the plasma mass density substantially.[1] A new plasma diagnostic method is developed to help examine the early time development of the gas-plasma interfacial structure. A preliminary study based on plasma polarization spectroscopy is presented, in which the dynamics of atoms and ions are visualized in the presence of electromagnetic fields due to charge separation. The ambient gas pressure of argon is varied as active control in the low-pressure regime. Time-resolved multi-directional projections of an aluminum plasma are obtained in line and continuum emissions, polarization and spectral broadening including Doppler shifts. The electrostatic potential of the target is also followed. The results indicate a bifurcation of the phase-space distribution function and structural segmentation of the plasma into a thermalized core and a crown with highly aligned, energetic atoms and ions. Reconstruction of the plasma structure appears possible by generalization of the two new algorithms we have developed.[1,2] 1. Y.W. Kim and J.-C. Oh, Rev. Sci. Inst. 72, 948 (2001). 2. Y.W. Kim and C.D. Lloyd-Knight, Rev. Sci. Inst. 72, 944 (2001).

Kim, Yong W.

2001-10-01

177

ORAL ISSUE OF THE JOURNAL "USPEKHI FIZICHESKIKH NAUK": Modeling of gas discharge plasma  

NASA Astrophysics Data System (ADS)

The condition for the self-maintenance of a gas discharge plasma (GDP) is derived from its ionization balance expressed in the Townsend form and may be used as a definition of a gas discharge plasma in its simplest form. The simple example of a gas discharge plasma in the positive column of a cylindrical discharge tube allows demonstrating a wide variety of possible GDP regimes, revealing a contradiction between simple models used to explain gas discharge regimes and the large number of real processes responsible for the self-maintenance of GDP. The variety of GDP processes also results in a stepwise change of plasma parameters and developing some instabilities as the voltage or discharge current is varied. As a consequence, new forms and new applications of gas discharge arise as technology progresses.

Smirnov, Boris M.

2009-06-01

178

Gas ionization induced by a high speed plasma injection in space  

NASA Technical Reports Server (NTRS)

Gas ionization induced by a fast plasma injection has been observed with the Space Experiments with Particle Accelerators (SEPAC) Experiment on Spacelab-1. When an impulsive high-density plasma was injected from the orbiter, waves near the lower-hybrid frequency were enhanced, and the surrounding gas drifting with the orbiter was ionized for several tens of milliseconds after the plasma injection. The long-duration gas ionization was observed only when the plasma flux incoming to the orbiter cargo bay and the orbital velocity perpendicular to the magnetic field were relatively large. This effect has been explained by the concept of critical velocity ionization (CVI) for the gas drifting with the orbiter, although the gas velocity perpendicular to the magnetic field was less than the Alfven critical velocity.

Sasaki, S.; Kawashima, N.; Kuriki, K.; Yanagisawa, M.; Obayashi, T.; Roberts, W. T.; Reasoner, D. L.; Taylor, W. W. L.

1986-01-01

179

Atomic Force Microscope Investigations of Bacterial Biofilms Treated with Gas Discharge Plasmas  

NASA Astrophysics Data System (ADS)

We present investigations of bacterial biofilms before and after treatment with gas discharge plasmas. Gas discharge plasmas represent a way to inactivate bacteria under conditions where conventional disinfection methods are often ineffective. These conditions involve biofilm communities, where bacteria grow embedded in an exopolysaccharide matrix, and cooperative interactions between cells make organisms less susceptible to standard inactivation methods. In this study, biofilms formed by the opportunistic bacterium Pseudomonas aeruginosa were imaged before and after plasma treatment using an atomic force microscope (AFM). Through AFM images and micromechanical measurements we observed bacterial morphological damage and reduced AFM tip-sample surface adhesion following plasma treatment.

Vandervoort, Kurt; Zelaya, Anna; Brelles-Marino, Graciela

2012-02-01

180

Influence of the gas-flow Reynolds number on a plasma column in a glass tube  

SciTech Connect

Atmospheric-plasma generation inside a glass tube is influenced by gas stream behavior as described by the Reynolds number (Rn). In experiments with He, Ne, and Ar, the plasma column length increases with an increase in the gas flow rate under laminar flow characterized by Rn < 2000. The length of the plasma column decreases as the flow rate increases in the transition region of 2000 < Rn < 4000. For a turbulent flow beyond Rn > 4000, the length of the plasma column is short in front of the electrode, eventually leading to a shutdown.

Jin, Dong Jun; Uhm, Han S.; Cho, Guangsup [Department of Electronic and Biological Physics, Kwangwoon University, 20 Kwangwon-Ro, Nowon-Gu, Seoul 139-701 (Korea, Republic of)] [Department of Electronic and Biological Physics, Kwangwoon University, 20 Kwangwon-Ro, Nowon-Gu, Seoul 139-701 (Korea, Republic of)

2013-08-15

181

Influence of the gas-flow Reynolds number on a plasma column in a glass tube  

NASA Astrophysics Data System (ADS)

Atmospheric-plasma generation inside a glass tube is influenced by gas stream behavior as described by the Reynolds number (Rn). In experiments with He, Ne, and Ar, the plasma column length increases with an increase in the gas flow rate under laminar flow characterized by Rn < 2000. The length of the plasma column decreases as the flow rate increases in the transition region of 2000 < Rn < 4000. For a turbulent flow beyond Rn > 4000, the length of the plasma column is short in front of the electrode, eventually leading to a shutdown.

Jin, Dong Jun; Uhm, Han S.; Cho, Guangsup

2013-08-01

182

Decomposition of Gas Phase Formaldehyde by Plasma Discharge.  

National Technical Information Service (NTIS)

Formaldehyde decomposition in a silent electrical discharge is shown to occur and it is demonstrated that the basis for the decomposition is not oxidation produced by ozone in the plasma. Keywords include: Plasma decomposition; Formaldehyde decomposition;...

E. J. Clothiaux

1985-01-01

183

Uranium plasma emission at gas-core reaction conditions  

NASA Technical Reports Server (NTRS)

The results of uranium plasma emission produced by two methods are reported. For the first method a ruby laser was focused on the surface of a pure U-238 sample to create a plasma plume with a peak plasma density of about 10 to the 20th power/cu cm and a temperature of about 38,600 K. The absolute intensity of the emitted radiation, covering the range from 300 to 7000 A was measured. For the second method, the uranium plasma was produced in a 20 kilovolt, 25 kilojoule plasma-focus device. The 2.5 MeV neutrons from the D-D reaction in the plasma focus are moderated by polyethylene and induce fissions in the U-235. Spectra of both uranium plasmas were obtained over the range from 30 to 9000 A. Because of the low fission yield the energy input due to fissions is very small compared to the total energy in the plasma.

Williams, M. D.; Jalufka, N. W.; Hohl, F.; Lee, J. H.

1976-01-01

184

A Novel Charged Medium Consisting of Gas-Liquid Interfacial Plasmas  

NASA Astrophysics Data System (ADS)

Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we succeed in creating the reactive gas (plasmas)—liquid (ionic liquids) interfacial field under a low gas pressure condition, where the plasma ion behavior can be controlled. The effects of the plasma ion irradiation on the liquid medium are quantitatively revealed for the first time. In connection with the plasma ion irradiation, the potential structure and optical emission properties of the gas-liquid interfacial plasma are investigated by changing a polarity of the electrode in the liquid to evaluate the plasma-liquid interactions. These results would contribute to synthesizing the metal nanoparticles with carbon nanotubes as a template in the ionic liquid. It is found that the high density, mono-dispersed, and isolated metal nanoparticles are synthesized between or inside the carbon nanotubes by controlling the gas-liquid interfacial plasmas. Furthermore, we can form novel nano-bio composite materials, such as DNA encapsulated carbon nanotubes using the plasma ion irradiation method in an electrolyte plasma with DNA, and demonstrate modifications of the electrical properties of the carbon nanotubes depending on the kinds of encapsulated DNA for the first time.

Kaneko, Toshiro; Hatakeyama, Rikizo

2009-11-01

185

A Novel Charged Medium Consisting of Gas-Liquid Interfacial Plasmas  

SciTech Connect

Due to the unique properties of ionic liquids such as their extremely low vapor pressure and high heat capacity, we succeed in creating the reactive gas (plasmas)--liquid (ionic liquids) interfacial field under a low gas pressure condition, where the plasma ion behavior can be controlled. The effects of the plasma ion irradiation on the liquid medium are quantitatively revealed for the first time. In connection with the plasma ion irradiation, the potential structure and optical emission properties of the gas-liquid interfacial plasma are investigated by changing a polarity of the electrode in the liquid to evaluate the plasma-liquid interactions. These results would contribute to synthesizing the metal nanoparticles with carbon nanotubes as a template in the ionic liquid. It is found that the high density, mono-dispersed, and isolated metal nanoparticles are synthesized between or inside the carbon nanotubes by controlling the gas-liquid interfacial plasmas. Furthermore, we can form novel nano-bio composite materials, such as DNA encapsulated carbon nanotubes using the plasma ion irradiation method in an electrolyte plasma with DNA, and demonstrate modifications of the electrical properties of the carbon nanotubes depending on the kinds of encapsulated DNA for the first time.

Kaneko, Toshiro; Hatakeyama, Rikizo [Department of Electronic Engineering, Tohoku University, Sendai 980-8579 (Japan)

2009-11-10

186

Gamma Inert Sterilization: A Solution to Polyethylene Oxidation?  

PubMed Central

Background: In the 1990s, oxidation was found to occur in ultra-high molecular weight polyethylene total joint replacement components following gamma irradiation and prolonged shelf aging in air. Orthopaedic manufacturers developed barrier packaging to reduce oxidation during and after radiation sterilization. The present study explores the hypothesis that polyethylene components sterilized in a low-oxygen environment undergo similar in vivo oxidative mechanisms as inserts sterilized in air. In addition, the potential influence of the different sterilization processes on the wear performance of the polyethylene components was examined. Methods: An analysis of oxidation, wear, and surface damage was performed for forty-eight acetabular liners and 123 tibial inserts. The mean implantation time was 12.3 ± 3.7 years for thirty-one acetabular liners that had been gamma sterilized in air and 4.0 ± 2.5 years for the seventeen acetabular liners that had been gamma sterilized in inert gas. The mean implantation time was 11.0 ± 3.2 years for the twenty-six tibial inserts that had been sterilized in air and 2.8 ± 2.2 years for the ninety-seven tibial inserts that had been gamma sterilized in inert gas. Oxidation and hydroperoxide levels were characterized in loaded and unloaded regions of the inserts. Results: Measurable oxidation and oxidation potential were observed in all cohorts. The oxidation and hydroperoxide levels were regional. Surfaces with access to body fluids were more heavily oxidized than protected bearing surfaces were. This variation appeared to be greater in historical (gamma-in-air-sterilized) components. Regarding wear performance, historical and conventional acetabular liners showed similar wear penetration rates, whereas a low incidence of delamination was confirmed for the conventional tibial inserts in the first decade of implantation. Conclusions: The present study explores the impact of industry-wide changes in sterilization practices for polyethylene. We found lower oxidation and oxidation potential in the conventional acetabular liners and tibial inserts that had been gamma sterilized in inert gas as compared with the historical components that had been gamma sterilized in air. However, we also found strong evidence that conventional components undergo mechanisms of in vivo oxidation similar to those observed following gamma irradiation in air. In addition, gamma sterilization in inert gas did not provide polyethylene with a significant improvement in terms of wear resistance as compared with gamma sterilization in air, except for a lower incidence of delamination in the first decade of implantation for tibial inserts. Clinical Relevance: Our research demonstrates that gamma inert sterilization may have improved, but not completely solved, the problem of polyethylene oxidation for hip and knee arthroplasty. PMID:19339568

Medel, Francisco J.; Kurtz, Steven M.; Hozack, William J.; Parvizi, Javad; Purtill, James J.; Sharkey, Peter F.; MacDonald, Daniel; Kraay, Matthew J.; Goldberg, Victor; Rimnac, Clare M.

2009-01-01

187

Enhancement of gas sensor response of nanocrystalline zinc oxide for ammonia by plasma treatment  

NASA Astrophysics Data System (ADS)

The effect of oxygen plasma treatment on nanocrystalline ZnO thin film based gas sensor was investigated. ZnO thin films were synthesized on alkali-free glass substrates by a sol-gel process. ZnO thin films were treated with oxygen plasma to change the number of vacancies/defects in ZnO. The effect of oxygen plasma on the structural, electrical, optical and gas sensing properties was investigated as a function of plasma treatment time. The results suggest that the microstructure and the surface morphology can be tuned by oxygen plasma treatment. The optical transmission in the visible range varies after the oxygen plasma treatment. Moreover, it is found that the oxygen plasma has significant impact on the electrical properties of ZnO thin films indicating a variation of resistivity. The oxygen plasma treated ZnO thin film exhibits an enhanced sensing response towards NH3 in comparison with that of the as-deposited ZnO sensor. When compared with the as-deposited ZnO film, the sensing response was improved by 50% for the optimum oxygen plasma treatment time of 8 min. The selectivity of 8 min plasma treated ZnO sensor was also examined for an important industrial gas mixture of H2, CH4 and NH3.

Hou, Yue; Jayatissa, Ahalapitiya H.

2014-08-01

188

The role of the gas/plasma plume and self-focusing in a gas-filled capillary discharge waveguide for high-power laser-plasma applications  

NASA Astrophysics Data System (ADS)

The role of the gas/plasma plume at the entrance of a gas-filled capillary discharge plasma waveguide in increasing the laser intensity has been investigated. Distinction is made between neutral gas and hot plasma plumes that, respectively, develop before and after discharge breakdown. Time-averaged measurements show that the on-axis plasma density of a fully expanded plasma plume over this region is similar to that inside the waveguide. Above the critical power, relativistic and ponderomotive self-focusing lead to an increase in the intensity, which can be nearly a factor of 2 compared with the case without a plume. When used as a laser plasma wakefield accelerator, the enhancement of intensity can lead to prompt electron injection very close to the entrance of the waveguide. Self-focusing occurs within two Rayleigh lengths of the waveguide entrance plane in the region, where the laser beam is converging. Analytical theory and numerical simulations show that, for a density of 3.0 × 1018 cm-3, the peak normalized laser vector potential, a0, increases from 1.0 to 1.85 close to the entrance plane of the capillary compared with a0 = 1.41 when the plume is neglected.

Ciocarlan, C.; Wiggins, S. M.; Islam, M. R.; Ersfeld, B.; Abuazoum, S.; Wilson, R.; Aniculaesei, C.; Welsh, G. H.; Vieux, G.; Jaroszynski, D. A.

2013-09-01

189

Gas-confined barrier discharges: a simplified model for plasma dynamics in flame environments  

E-print Network

In this paper we evaluate the dynamics of non-thermal plasmas developing in extremely non-homogeneous environments. We present the gas-confined barrier discharge (GBD) concept and justify its importance as a first step to ...

Guerra-Garcia, Carmen

190

Dust-gas Interactions in Dusty X-ray Emitting Plasmas  

NASA Technical Reports Server (NTRS)

Dusty shocked plasmas cool primarily by infrared emission from dust that is collisionally heated by the ambient hot gas. The infrared emission provides therefore an excellent diagnostic of the conditions (density and temperature) of the shocked gas. In this review I will discuss the physical processes in these plasmas, with a particular emphasis on recent infrared observations of the interaction between the blast wave of SN1987a and its equatorial ring.

Dwek, Eli

2006-01-01

191

Residual stress in plasma sprayed ceramic turbine tip and gas path seal specimens  

NASA Technical Reports Server (NTRS)

The residual stresses in a ceramic sheet material used for turbine blade tip gas path seals, were estimated. These stresses result from the plasma spraying process which leaves the surface of the sheet in tension. To determine the properties of plasma sprayed ZrO2-Y2O3 sheet material, its load deflection characteristics were measured. Estimates of the mechanical properties for sheet materials were found to differ from those reported for plasma sprayed bulk materials.

Hendricks, R. C.; Mcdonald, G.; Mullen, R. L.

1983-01-01

192

Electron interaction cross sections for a low-temperature 'plasma-like' gas mixture  

NASA Astrophysics Data System (ADS)

Electron interaction cross sections for species found in low-temperature industrial plasma environments are a crucial component to allow for accurate modeling of those plasmas. However, such data are still rarely reported in the literature, due to the complexities of working with such highly reactive species in a laboratory. Here, absolute differential cross section measurements for a 'plasma-like' gas mixture, containing CF3I, CF3, I2, I and C2F6, are reported.

Hargreaves, L. R.; Brunton, J. R.; Brunger, M. J.; Buckman, S. J.

2010-12-01

193

Effects of Ignition on Discharge Symmetry in Gas-Fed Pulsed Plasma Thrusters  

E-print Network

. Originally studied in the late 1960's, both ablative pulsed plasma thrusters (APPTs) and Gas-fed pulsed Assistant supported by Princeton University's Program in Plasma Science and Technology. Member AIAA. Princeton University Princeton, New Jersey 08544 Daniel Birx Science Research Laboratory Inc., Sommerville

Choueiri, Edgar

194

Treatment of NO x in exhaust gas by corona plasma over water surface  

Microsoft Academic Search

For developing NOx treatment engineering of exhaust gas in lower construction and operating cost, we propose a new type of corona reactor with some experimental results. The reactor is madeup of multi needles’ electrode placed over water and to make use of corona plasma over water surface for plasma chemical reactions. Typical corona characteristics of the reactor with positive and

Tomio Fujii; Massimo Rea

2000-01-01

195

Non-thermal plasmas as gas-phase advanced oxidation processes  

SciTech Connect

Non-thermal plasmas are useful for generating reactive species (free radicals) in a gas stream. Because radical attack reaction rate constants are very large for many chemical species, entrained pollutants are readily decomposed by radicals. Such plasmas can generate both oxidative and reductive radicals; therefore, they show promise for treating a wide variety of pollutants.

Rosocha, L.A.

1997-08-01

196

Generation of short pulse radiation from magnetized wake in gas-jet plasma and laser interaction  

Microsoft Academic Search

New features of a high power tunable radiation from the magnetized plasma wakes are studied. This Letter covers some aspects of the problem, which was previously discussed in details in [Phys. Rev. E 68 (2003) 026409]. A gas-jet flow is used to generate the sharp boundary plasma. Wakefield is excited by a mode locked Ti:sapphire laser beam operating at 800

Davoud Dorranian; Mahmood Ghoranneviss; Mikhail Starodubtsev; Hiroaki Ito; Noboru Yugami; Yasushi Nishida

2004-01-01

197

Numerical modelling of atmospheric pressure gas discharges leading to plasma production  

Microsoft Academic Search

In this paper, we give a detailed review of recent work carried out on the numerical characterization of non-thermal gas discharge plasmas in air at atmospheric pressure. First, we briefly describe the theory of discharge development for dielectric barrier discharges, which is central to the production of non-equilibrium plasma, and we present a hydrodynamic model to approximate the evolution of

G E Georghiou; A P Papadakis; R Morrow; A C Metaxas

2005-01-01

198

Influence of Plasma Gas on the Quality-Related Properties of Wool Fabric  

Microsoft Academic Search

Plasma treatment affected the quality-related properties of wool fabric such as air permeability, pilling, tearing strength, tensile strength, crease-recovery angle, and surface luster which were studied thoroughly in this paper. The plasma gases with different natures were used, and the experimental results showed that the gas nature influenced the properties of air permeability, tearing strength, tensile strength, elongation, and crease

C. W. Kan; C. W. M. Yuen

2009-01-01

199

Karlson ozone sterilizer. Final report  

SciTech Connect

The authors have a functional sterilization system employing ozone as a sterilization agent. This final report covers the work that led to the first medical sterilizer using ozone as the sterilizing agent. The specifications and the final design were set by hospital operating room personnel and public safety standards. Work on kill tests using bacteria, viruses and fungi determined the necessary time and concentration of ozone necessary for sterilization. These data were used in the Karlson Ozone Sterilizer to determine the length of the steps of the operating cycle and the concentration of ozone to be used. 27 references.

Karlson, E.

1984-05-07

200

Sterilization by dry heat  

PubMed Central

The advantages and disadvantages of three forms of dry heat sterilization are discussed. In addition a fourth method, consisting of heating by infrared rays in vacuo, is described. This method is particularly suitable for instruments used in the operating theatre, since it can replace an autoclave where a supply of steam is not available. Recommended times and temperatures for dry heat sterilization are detailed, and are related to the thermal death point of Cl. tetani. The dangers of recontamination during the cooling process are discussed. PMID:13719782

Darmady, E. M.; Hughes, K. E. A.; Jones, J. D.; Prince, D.; Tuke, Winifred

1961-01-01

201

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Interaction of laser radiation with a dense gas target  

Microsoft Academic Search

An investigation was made of the interaction of a nanosecond laser pulse with a 'puff' gas target at gas densities sufficient for the formation of a critical-density plasma. The parameters of the laser plasma formed in the central interaction region and at its periphery were determined by x-ray spectroscopic methods. The formation of a plasma channel was observed and it

A. Bartnik; V. M. Dyakin; I. Yu Skobelev; A. Ya Faenov; H. Fiedorowicz; M. Szczurek

1997-01-01

202

Spectroscopy and X-radiation from exploded-wire arrays and gas-puff plasmas  

Microsoft Academic Search

In this report results are presented for three separate experiments involving multiple exploded wire arrays and puff gas plasmas. The first section deals with the analysis and interpretation of X-ray line spectra from a variety of exploded multiple wire arrays including Al, glass, Ti, SS, Mo, and W wires. The second section deals with X-ray spectra from puff gas experiments

P. Burkhalter; J. Davis

1979-01-01

203

Atmospheric Pressure Humid Argon DBD Plasma for the Application of Sterilization - Measurement and Simulation of Hydrogen, Oxygen, and Hydrogen Peroxide Formation  

Microsoft Academic Search

Hydrogen, oxygen, and hydrogen peroxide have been measured downstream of an atmospheric pressure humid argon dielectric barrier discharge. The yield of the three species was studied as a function of the discharge power and gas flow rate. Hydrogen peroxide was measured after dissolution into water downstream of the discharge, while hydrogen and oxygen were measured in the gas phase. The

M. J. Kirkpatrick; B. Dodet; E. Odic

204

Biological Sterilization of Returned Mars Samples  

NASA Technical Reports Server (NTRS)

Martian rock and soil, collected by robotic spacecraft, will be returned to terrestrial laboratories early in the next century. Current plans call for the samples to be immediately placed into biological containment and tested for signs of present or past life and biological hazards. It is recommended that "Controlled distribution of unsterilized materials from Mars should occur only if rigorous analyses determine that the materials do not constitute a biological hazard. If any portion of the sample is removed from containment prior to completion of these analyses it should first be sterilized." While sterilization of Mars samples may not be required, an acceptable method must be available before the samples are returned to Earth. The sterilization method should be capable of destroying a wide range of organisms with minimal effects on the geologic samples. A variety of biological sterilization techniques and materials are currently in use, including dry heat, high pressure steam, gases, plasmas and ionizing radiation. Gamma radiation is routinely used to inactivate viruses and destroy bacteria in medical research. Many commercial sterilizers use Co-60 , which emits gamma photons of 1.17 and 1.33 MeV. Absorbed doses of approximately 1 Mrad (10(exp 8) ergs/g) destroy most bacteria. This study investigates the effects of lethal doses of Co-60 gamma radiation on materials similar to those anticipated to be returned from Mars. The goals are to determine the gamma dose required to kill microorganisms in rock and soil samples and to determine the effects of gamma sterilization on the samples' isotopic, chemical and physical properties. Additional information is contained in the original extended abstract.

Allen, C. C.; Albert, F. G.; Combie, J.; Bodnar, R. J.; Hamilton, V. E.; Jolliff, B. L.; Kuebler, K.; Wang, A.; Lindstrom, D. J.; Morris, P. A.

1999-01-01

205

An inductively coupled plasma spectrometer for on-line, real-time process gas analysis  

SciTech Connect

On-line, real-time analysis of process gas streams, such as gasification and combustion processes, is becoming increasingly important. This dissertation describes an inductively coupled plasma spectrometer capable of analyzing for trace metals in particulate laden process gases that are injected directly into the ICP torch at high temperatures (500/degree/C) and at high sample flow rates necessary to maintain large particulate (10 to 20 micron) entrainment between the process sampling point and the plasma. The system uses a mixed gas argon-helium plasma, and use of the argon-helium plasma as opposed to a nitrogen, oxygen, or air plasma is defended. Characteristics of argon-helium and helium plasmas operated at very high rf forward energy levels are discussed and compared to the characteristics of an argon plasma operated under normal ICP conditions. Also presented are results of actual on-line testing of the ISP, some detection limits determined for elements in process gas types of streams, and the best emission lines to use for elements in process gas streams. 21 figs., 15 tabs.

McCarty, D.L. II

1988-01-01

206

Effect of plasma treatment on the gas sensor with single-walled carbon nanotube paste.  

PubMed

The effect of plasma treatment on the gas sensing properties of screen-printed single-walled carbon nanotube (SWCNT) pastes is reported. The gas sensors, using SWCNT pastes as a sensing material, were fabricated by photolithography and screen printing. The SWCNT pastes were deposited between interdigitated electrodes on heater membrane by screen printing. In order to functionalize the pastes, they were plasma treated using several gases which produce defects caused by reactive ion etching. The Ar and O(2) plasma-treated SWCNT pastes exhibited a large response to NO(2) exposure and the fluorinated gas, such as CF(4) and SF(6), plasma-treated SWCNT pastes exhibited a large response to NH(3) exposure. PMID:22284456

Dong, Ki-Young; Ham, Dae-Jin; Kang, Byung Hyun; Lee, Keunsoo; Choi, Jinnil; Lee, Jin-Woo; Choi, Hyang Hee; Ju, Byeong-Kwon

2012-01-30

207

Study Of The Gas Balance By Injection Of Hydrocarbons Into The Plasma Simulator PSI 2  

SciTech Connect

The stationary plasma of the plasma generator PSI 2 is used to study the gas balance of hydrocarbons and hydro-gen by means of mass spectrometers. For this purpose H2, acetylene and ethylene are injected into argon and hydrogen plasmas. It is found that hydrogenation of the hydrocarbon layers is strongly influenced by the hydrocarbon species injected previously. Furthermore, time constants of more than 1000 s for achieving stationary conditions are identified in some cases. The H/C ratio of the hydrocarbon layers is found to vary from about 1 to 1.4 for argon and hydrogen plasmas, respectively.

Bohmeyer, Werner [Max- Planck- Institut fuer Plasmaphysik TI Greifswald, Wendelsteinstr. 1 17491 Greifswald EURATOM Ass. (Germany); Markin, Andrey [RAS, Institute of Physical Chemistry, Moscow (Russian Federation); Koch, Bernd; Fussmann, Gerd [Max- Planck- Institut fuer Plasmaphysik TI Greifswald, Wendelsteinstr. 1 17491 Greifswald EURATOM Ass. (Germany); Humboldt Universitaet zu Berlin, Plasmaphysik, Newtonstr.15 12489 Berlin (Germany); Krenz, Gordon [Humboldt Universitaet zu Berlin, Plasmaphysik, Newtonstr.15 12489 Berlin (Germany)

2006-01-15

208

Modification of plasma flows with gas puff in the scrape-off layer of ADITYA tokamak  

SciTech Connect

The parallel Mach numbers are measured at three locations in the scrape-off layer (SOL) plasma of ADITYA tokamak by using Mach probes. The flow pattern is constructed from these measurements and the modification of flow pattern is observed by introducing a small puff of working gas. In the normal discharge, there is an indication of shell structure in the SOL plasma flows, which is removed during the gas puff. The plasma parameters, particle flux and Reynolds stress are also measured in the normal discharge and in the discharge with gas puff. It is observed that Reynolds stress and Mach number are coupled in the near SOL region and decoupled in the far SOL region. The coupling in the near SOL region gets washed away during the gas puff.

Sangwan, Deepak; Jha, Ratneshwar; Brotankova, Jana; Gopalkrishna, M. V. [Institute for Plasma Research, Gandhinagar 382428 (India)] [Institute for Plasma Research, Gandhinagar 382428 (India)

2013-06-15

209

Enhanced electron yield from a laser-plasma accelerator using high-Z gas jet targets  

E-print Network

An investigation of the multi-hundred MeV electron beam yield (charge) form helium, nitrogen, neon and argon gas jet plasmas in a laser-plasma wakefield acceleration experiment was carried out. The charge measurement has been made via imaging the electron beam intensity profile on a fluorescent screen into a 14-bit charge coupled device (CCD) which was cross-calibrated with nondestructive electronics-based method. Within given laser and plasma parameters, we found that laser-driven low Z- gas jet targets generate high-quality and well-collimated electron beams with reasonable yields at the level of 10-100 pC. On the other hand, filamentary electron beams which were observed from high-Z gas jets at higher densities reached much higher yield. Evidences for cluster formation were clearly observed in high-Z gases, especially in the argon gas jet target where we received the highest yield of ~ 3 nC

Mirzaie, Mohammad; Li, Song; Sokollik, Thomas; He, Fei; Cheng, Ya; Sheng, Zhengming; Zhang, Jie

2014-01-01

210

Investigation of helium addition for laser-induced plasma spectroscopy of pure gas phase systems: Analyte interactions and signal enhancement  

E-print Network

Investigation of helium addition for laser-induced plasma spectroscopy of pure gas phase systems in plasma properties, namely electron density and laser- plasma coupling. Helium addition is concluded breakdown processes. © 2007 Elsevier B.V. All rights reserved. Keywords: LIBS; Laser-induced plasma

Hahn, David W.

211

A Coupled Plasma Dynamics and Gas Flow Model for Semiconductor Processing  

NASA Technical Reports Server (NTRS)

A continuum modeling approach by self-consistently coupling plasma dynamics and gas flow will be presented for the analysis of high density plasma reactors. Experimental data shows that gas flow distribution affects the etch rate uniformity even at low pressures (6-20 mTorr) and flow rates (20-70 sccm). This study will investigate the effects of gas flow and gas energy on bulk plasma densities and temperatures using a continuum model. The model solves multidimensional equations of mass balance for neutrals and ions, gas momentum, separate energy equations for electrons and neutrals and Maxwell's equations for power coupling. A test case of N2 plasma in a 300mm TCP etch reactor, for which hybrid model and Langmuir probe data are available, is chosen for this analysis. Our preliminary results show that modeling gas flow and energy improves the predictions of electron density and its spatial variation in the reactor when compared with the experimental data. The aim of this study is to identify the operating conditions for the TCP reactor when a self-consistent modeling of gas flow is important.

Bose, Deepak; Govindan, T. R.; Meyyappan, M.; Arnold, James O. (Technical Monitor)

1998-01-01

212

Control of the area irradiated by the sheet-type plasma jet in atmospheric pressure  

NASA Astrophysics Data System (ADS)

The sterilization effect has been investigated using the sheet-type plasma jet, which was generated between asymmetric electrodes with dielectric plates in gas flow released into the atmospheric air. In this paper, it is indicated there is a possibility that the plasma jet irradiation area can be controlled only by supplied gases without changing a generator structure. The irradiation area control was evaluated from both the sterilization area size and the oxidizing substances distribution. The oxidizing substance distribution was obtained using the chemical reagent prepared in our laboratory. The width of the sheet-type plasma jet was able to be controlled by N2 addition into He gas. As a result, the width of the sterilization area was able to be controlled within the range of 2 to 12 mm at a constant height without changing the generator structure. On the other hand, the evaluation from the oxidizing substances distribution indicated that the irradiation area cannot be controlled in one direction.

Kawasaki, T.; Kawano, K.; Mizoguchi, H.; Yano, Y.; Yamashita, K.; Sakai, M.; Uchida, G.; Koga, K.; Shiratani, M.

2014-06-01

213

Solid particle production in fluorocarbon plasmas II: Gas phase reactions for polymerization  

NASA Astrophysics Data System (ADS)

Solid particles were observed in fluorocarbon (C4F8) plasmas applied to semiconductor plasma processing. In order to elucidate gas-phase reactions for particle formation, Fourier transform infrared (FTIR) spectroscopy was employed. The method showed that stable molecules (CF4, C2F6, and C2F4) were produced in the plasmas. Several absorption peaks found in a spectrum from a surface polymer were observed in the gas phase. The peaks were regarded to be from plasma-polymerized molecules in the plasmas. In particular, the absorption signals from species of -CF=CF- and -CF=CF2, which were produced from C2F4 molecules, were extinguished with the particle formation. Furthermore, densities of fluorocarbon radicals CFx (x=1,2,3) were measured in CHF3 and C2F6 plasmas as well as in C4F8 plasmas with infrared laser absorption spectroscopy. The pressure dependence of the densities drastically changed with the presence of the particles. This was induced by sticking of the radicals onto gas-phase polymers including the particles. As the results obtained in the infrared spectroscopic methods, it was found that not these radicals but the C2F4 molecule as a reactive product played an important role in the formation of the particles.

Takahashi, Kazuo; Tachibana, Kunihide

2002-03-01

214

Magnetically controlled deposition of metals using gas plasma. Final report  

SciTech Connect

This is the first phase of a project that has the objective to develop a method of spraying materials on a substrate in a controlled manner to eliminate the waste and hazardous material generation inherent in present plating processes. The project is considering plasma spraying of metal on a substrate using magneto-hydrodynamics to control the plasma/metal stream. The process being developed is considering the use of commercially available plasma torches to generate the plasma/metal stream. The plasma stream is collimated, and directed using magnetic forces to the extent required for precise control of the deposition material. The project will be completed in phases. Phase one of the project, the subject of this grant, is the development of an analytical model that can be used to determine the feasibility of the process and to design a laboratory scale demonstration unit. The contracted time is complete, and the research is still continuing. This report provides the results obtained to date. As the model and calculations are completed those results will also be provided. This report contains the results of the computer code that have been completed to date. Results from a ASMEE Benchmark problem, flow over a backward step with heat transfer, Couette flow with magnetic forces, free jet flow are presented along with several other check calculations that are representative of the cases that were calculated in the course of the development process. The final cases that define a velocity field in the exit of a plasma spray torch with and without a magnetic field are in process. A separate program (SPRAY) has been developed that can track the plating material to the substrate and describe the distribution of the material on the substrate. When the jet calculations are complete SPRAY will be used to compare the distribution of material on the substrate with and without the effect of the magnetic focus.

NONE

1998-04-02

215

Plasma assisted synthesis of WS2 for gas sensing applications  

NASA Astrophysics Data System (ADS)

We report the plasma assisted synthesis of WS2 thin films and demonstrate their suitability for sensing applications. This was achieved by using a H2S plasma to sulphurise WO3 films at temperatures as low as 500 °C. This is a significant step towards semiconductor compatible growth of transition metal dichalcogenide (TMD) thin films without the need for highly elevated temperatures. We found that the electrical transport in thin films is highly sensitive to the presence of NH3. A sensitivity of 1.4 ppm NH3 in nitrogen at room temperature has been achieved, demonstrating the potential of 2D TMD films for sensing applications.

O'Brien, Maria; Lee, Kangho; Morrish, Rachel; Berner, Nina C.; McEvoy, Niall; Wolden, Colin A.; Duesberg, Georg S.

2014-11-01

216

A review: taking the sterile out of sterility.  

PubMed

Users of in-dwelling medical devices, prostheses and surgical dressings rely implicitly on their sterility. Rarely do consumers give any thought to what sterility really means. The general assumption is that manufacturers have adopted the most efficient and cost-effective methods of achieving sterility. Currently, terminal sterilization processes appropriate for the manufacture of medical devices are those that are deemed to give less than one chance in a million of a single, finished product item containing a viable organism. Such a definition of sterility is embodied in the European standard EN556 as a Sterility Assurance Level of 10(-6), based on the properties of heat-resistant endospores. However, is this level of sterility assurance appropriate for all categories of medical device? Moreover, do all medical devices which are labelled as sterile require the same level of treatment? This paper will demonstrate that in some instances, the high standards set for sterilization processing are unreasonable, not cost-effective and exclude new sterilization technologies from being accepted by the regulatory authorities. PMID:10664904

Allison, D G

1999-12-01

217

The testing of sterilizers  

PubMed Central

Satisfactory spore preparations for testing hospital sterilizers can be made from B. stearothermophilus and comparatively simple methods for loading and drying the papers are considered to be valid. Each batch of spore papers should be calibrated by plotting dose-response curves for exposure to steam. A minimum standard in terms of the L.D.50 to moist heat is proposed and confidence limits suggested when such papers are used in pairs or small multiples. PMID:13752417

Kelsey, J. C.

1961-01-01

218

Atomic Force Microscope Investigations of Biofilms Treated with Gas Discharge Plasmas  

NASA Astrophysics Data System (ADS)

We present investigations of bacterial biofilms before and after treatment with gas discharge plasmas. Gas discharge plasmas represent a way to inactivate bacteria under conditions where conventional disinfection methods are often ineffective. These conditions involve bacteria in biofilm communities, where cooperative interactions between cells make organisms less susceptible to standard inactivation methods. In this study, biofilms formed by the opportunistic bacterium Pseudomonas aeruginosa were imaged before and after plasma treatment using an atomic force microscope (AFM). Cell morphology and biofilm structure were investigated through AFM images obtained for various plasma exposure times. Also, structural properties of the biofilms were studied through force-distance curves by pressing the AFM tip into the film surface while monitoring the cantilever deflection.

Vandervoort, Kurt; Stough, Gregory; Zelaya, Anna; Brelles-Marino, Graciela

2010-03-01

219

Modelling of non-thermal plasma aftertreatment of exhaust gas streams  

NASA Astrophysics Data System (ADS)

A reaction mechanism has been developed that is appropriate for the plasma aftertreatment of diesel exhaust gas. It is based on a simulated gas mixture containing propene, nitric oxide, nitrogen dioxide, oxygen and nitrogen. The reaction mechanism has been used to determine the end-products from the plasma processing and their concentrations using a chemical kinetics modelling procedure. It has been validated by a range of experiments using the same gas mixture with a packed bed, a dielectric barrier plasma reactor and a wide range of end-product analysis techniques. Using a wide range of experimental conditions has enabled us to validate the model and its predictions and to critically evaluate several alternative reaction mechanisms for the oxidation of propene and the formation of end-products in a more systematic and reliable manner than before.

Martin, Anthony R.; Shawcross, James T.; Whitehead, J. Christopher

2004-01-01

220

Gravity Control by means of Electromagnetic Field through Gas or Plasma at Ultra-Low Pressure  

E-print Network

It is shown that the gravity acceleration just above a chamber filled with gas or plasma at ultra-low pressure can be strongly reduced by applying an Extra Low-Frequency (ELF) electromagnetic field across the gas or the plasma. This Gravitational Shielding Effect is related to recent discovery of quantum correlation between gravitational mass and inertial mass. According to the theory samples hung above the gas or the plasma should exhibit a weight decrease when the frequency of the electromagnetic field is decreased or when the intensity of the electromagnetic field is increased. This Gravitational Shielding Effect is unprecedented in the literature and can not be understood in the framework of the General Relativity. From the technical point of view, there are several applications for this discovery; possibly it will change the paradigms of energy generation, transportation and telecommunications.

Fran De Aquino

2007-01-08

221

MW-CLASS INDUCTIVE MPD THRUSTER USING NON-UNIFORM GAS-PLASMA FLOW  

Microsoft Academic Search

Numerical simulations of nonstationary MHD process of the non-uniform gas-plasma flow acceleration in the electric propulsion (EP) channel in one-dimensional and two-dimensional approaches are performed. It is demonstrated that the T-layers used to generate the flow inhomogeneities in the form of plasma pistons allows to avoid the overheating instability development even at 1000 times increase of mass flow rate. The

V. S. Slavin; A. A. Gavrilov

222

Method for generating a highly reactive plasma for exhaust gas aftertreatment and enhanced catalyst reactivity  

DOEpatents

A method for non-thermal plasma aftertreatment of exhaust gases the method comprising the steps of providing short risetime (about 40 ps), high frequency (about 5G hz), high power bursts of low-duty factor microwaves sufficient to generate a dielectric barrier discharge and passing a gas to treated through the discharge so as to cause dissociative reduction of the exhaust gases. The invention also includes a reactor for generating the non-thermal plasma.

Whealton, John H. (Oak Ridge, TN); Hanson, Gregory R. (Clinton, TN); Storey, John M. (Oak Ridge, TN); Raridon, Richard J. (Oak Ridge, TN); Armfield, Jeffrey S. (Upsilanti, MI); Bigelow, Timothy S. (Knoxville, TN); Graves, Ronald L. (Knoxville, TN)

2001-01-01

223

The effect of the gas temperature gradient on dust structures in a glow-discharge plasma  

Microsoft Academic Search

An experimental investigation is performed of the effect of the neutral gas temperature gradient on plasma-dust formations\\u000a in the positive column of a glow discharge. It is demonstrated that the thermophoretic forces arising due to the temperature\\u000a gradient are comparable with radial electric fields and define the condition of formation and different shapes of plasma-dust\\u000a structures, in particular, the formation

V. V. Balabanov; L. M. Vasilyak; S. P. Vetchinin; A. P. Nefedov; D. N. Polyakov; V. E. Fortov

2001-01-01

224

On-board plasma-assisted conversion of heavy hydrocarbons into synthesis gas  

Microsoft Academic Search

The fuel conversion performance of two gliding arc plasma reformers is investigated with the goal of syn-gas production on-board vehicles. In both systems, n-tetradecane (C14H30) fuel was reformed with plasma under partial oxidation conditions in the absence of metal catalysts and steam. A comparison of the performance of each device is made with regard to the hydrogen yield and energy

Michael J. Gallagher; Robert Geiger; Anatoliy Polevich; Alexander Rabinovich; Alexander Gutsol; Alexander Fridman

2010-01-01

225

Hysteroscopic Tubal Sterilization  

PubMed Central

Background Hysteroscopic sterilization is a minimally invasive alternative to laparoscopic tubal ligation for women who want permanent contraception. In contrast to the laparoscopic technique, a hysteroscope is used to pass permanent microinserts through the cervix and place them in the fallopian tubes. This procedure does not require local or general anesthesia and can be performed in an office setting. Objectives The objective of this analysis was to determine, based on published literature, the cost-effectiveness of hysteroscopic tubal sterilization (HS) compared with laparoscopic tubal ligation (LS) for permanent female sterilization. Data Sources A systematic literature search was conducted for studies published between January 1, 2008, and December 11, 2012. Review Methods Potentially relevant studies were identified based on the title and abstract. Cost-utility analyses (studies that report outcomes in terms of costs and quality-adjusted life-years) were prioritized for inclusion. When not available, cost-effectiveness, cost-benefit, and cost-consequence analyses were considered. Costing studies were considered in the absence of all other analyses. Results A total of 33 abstracts were identified. Three cost analyses were included. A retrospective chart review from Canada found that HS was $111 less costly than LS; a prospective activity-based cost management study from Italy reported that it was €337 less costly than LS; and the results of an American decision model showed that HS was $1,178 less costly than LS. Limitations All studies had limited applicability to the Ontario health care system due to differences in setting, resource use, and costs. Conclusions Three cost analyses found that, although the HS procedure was more expensive due to the cost of the microinserts, HS was less costly than LS overall due to the shorter recovery time required. Plain Language Summary Hysteroscopic sterilization is a minimally invasive alternative to conventional tubal ligation for women who want a permanent method of contraception. Both approaches involve closing off the fallopian tubes, preventing the egg from moving down the tube and the sperm from reaching the egg. Tubal ligation is a surgical procedure to tie or seal the fallopian tubes, and it usually requires general anesthesia. In contrast, hysteroscopic tubal sterilization can be performed in 10 minutes in an office setting without general or even local anesthesia. A tiny device called a microinsert is inserted into each fallopian tube through the vagina, cervix, and uterus without surgery. An instrument called a hysteroscope allows the doctor to see inside the body for the procedure. Once the microinserts are in place, scar tissue forms around them and blocks the fallopian tubes. Health Quality Ontario commissioned a systematic review of published economic literature to determine whether hysteroscopic sterilization is cost-effective compared to tubal ligation. This review did not find any studies that reported results in terms of both costs and effectiveness or costs and quality-adjusted life-years. We did find 3 costing studies and included them in our review. All of these studies found that when hysteroscopic sterilization was performed as an outpatient procedure, it was less expensive than tubal ligation due to a shorter recovery time. However, none of the studies apply directly to Ontario because of differences in our health care system compared to those in the studies. PMID:24228085

2013-01-01

226

Residual stress in plasma-sprayed ceramic turbine tip and gas-path seal specimens  

NASA Technical Reports Server (NTRS)

The residual stresses in a ceramic sheet material used for turbine blade tip gas path seals, were estimated. These stresses result from the plasma spraying process which leaves the surface of the sheet in tension. To determine the properties of plasma sprayed ZrO2-Y2O3 sheet material, its load deflection characteristics were measured. Estimates of the mechanical properties for sheet materials were found to differ from those reported for plasma sprayed bulk materials. Previously announced in STAR as N83-28380

Hendricks, R. C.; Mcdonald, G.; Mullen, R. L.

1983-01-01

227

Method for generating a highly reactive plasma for exhaust gas aftertreatment and enhanced catalyst reactivity  

DOEpatents

A method for non-thermal plasma aftertreatment of exhaust gases the method comprising the steps of providing short risetime, high frequency, high power bursts of low-duty factor microwaves sufficient to generate a plasma discharge and passing a gas to be treated through the discharge so as to cause dissociative reduction of the exhaust gases and enhanced catalyst reactivity through application of the pulsed microwave fields directly to the catalyst material sufficient to cause a polarizability catastrophe and enhanced heating of the metal crystallite particles of the catalyst, and in the presence or absence of the plasma. The invention also includes a reactor for aftertreatment of exhaust gases.

Whealton, John H. (Oak Ridge, TN); Hanson, Gregory R. (Clinton, TN); Storey, John M. (Oak Ridge, TN); Raridon, Richard J. (Oak Ridge, TN); Armfield, Jeffrey S. (Ypsilanti, MI); Bigelow, Timothy S. (Knoxville, TN); Graves, Ronald L. (Knoxville, TN)

2002-01-01

228

Feather-like He plasma plumes in surrounding N2 gas  

NASA Astrophysics Data System (ADS)

Effects of surrounding gases on the propagation of room-temperature atmospheric-pressure plasma jets are reported. A highly unusual feather-like plasma plume is observed only when N2 is used as surrounding gas. The He concentration on the axis at the starting point of the feather-like plume is ˜0.85 of the maximum value and is independent on the He flow rates. High-speed optical imaging reveals that dim diffuse plasmas emerge just behind the bright head of the plasma bullet at the starting point of the feather-like plume. These results help tailoring surface exposure in emerging applications of plasma jets in medicine and nanotechnology.

Xian, Y. B.; Zou, D. D.; Lu, X. P.; Pan, Y.; Ostrikov, K.

2013-08-01

229

Wear behavior of gas tunnel type plasma sprayed Zr-based metallic glass composite coatings  

NASA Astrophysics Data System (ADS)

Gas tunnel type plasma spraying is a prospective method to produce metallic glass composite coatings with high quality due to its noteworthy feature of process controllability. In this study, Zr55Cu30Al10Ni5 metallic glass composite coatings were produced by gas tunnel type plasma spraying torch under optimum spraying conditions with selected plasma currents. The formation mechanism, sliding, and erosive wear behaviors of the coatings with respect to plasma current was examined. The phase and thermal analyses as well as microstructure of the plasma sprayed coatings produced at different plasma currents were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) techniques. The sliding and erosive wear behaviors of the coatings were studied using a pin-on-disc and a specially designed erosive wear tester, respectively. The results showed that an increase in plasma current increased the crystalline content in the metallic glass composite coatings, which enhanced the hardness and wear resistance of the coatings.

Yugeswaran, S.; Kobayashi, A.; Suresh, K.; Rao, K. P.; Subramanian, B.

2012-09-01

230

The effect of asymmetric gas puffing on toroidal flow in the edge of tokamak plasma  

NASA Astrophysics Data System (ADS)

The neoclassical theory of toroidal plasma rotation in the presence of an asymmetric neutral gas source in the edge of tokamak is examined. The poloidal dependence of momentum damping and ion energy loss due to charge-exchange processes are included. It is shown that the toroidal flow velocity increases significantly if the gas is fueled from the inboard side of the tokamak; the radial electric field and its shear are modified accordingly. It is also shown that for a fixed gas-fueling rate, the asymmetric fueling has a smaller role in TEXTOR [G. Mank et al., Phys. Rev. Lett. 85, 2312 (2000)] than in COMPASS-D [M. Valovi et al., Plasma Phys. Controlled Fusion 44, A175 (2002)]. The role of asymmetric gas injection is therefore effectively stronger in COMPASS-D.

Singh, Raghvendra; Rogister, Andre; Kaw, Predhiman

2004-01-01

231

A carbon monoxide gas sensor using oxygen plasma modified carbon nanotubes  

NASA Astrophysics Data System (ADS)

Carbon monoxide (CO) is a highly toxic gas that can be commonly found in many places. However, it is not easily detected by human olfaction due to its colorless and odorless nature. Therefore, highly sensitive sensors need to be developed for this purpose. Carbon nanotubes (CNTs) have an immense potential in gas sensing. However, CNT-based gas sensors for sensing CO are seldom reported due to the lack of reactivity between CO and CNTs. In this work, O2 plasma modified CNT was used to fabricate a CNT gas sensor. The plasma treated CNTs showed selectively towards CO, with the capability of sensing low concentrations of CO (5 ppm) at room temperature, while the pristine CNTs showed no response. UV spectra and oxygen reduction reaction provided evidence that the difference in sensing property was due to the elimination of metallic CNTs and enhancement of the oxygen reduction property.

Zhao, Weiyun; Fam, Derrick Wen Hui; Yin, Zongyou; Sun, Ting; Tan, Hui Teng; Liu, Weiling; Iing Yoong Tok, Alfred; Boey, Yin Chiang Freddy; Zhang, Hua; Hng, Huey Hoon; Yan, Qingyu

2012-10-01

232

Removal of formaldehyde from gas streams via packed-bed dielectric barrier discharge plasmas  

Microsoft Academic Search

Formaldehyde is a major indoor air pollutant and can cause serious health disorders in residents. This work reports the removal of formaldehyde from gas streams via alumina-pellet-filled dielectric barrier discharge plasmas at atmospheric pressure and 70 °C. With a feed gas mixture of 140 ppm HCHO, 21.0% O2, 1.0% H2O in N2, ~92% of formaldehyde can be effectively destructed at

Hui-Xian Ding; Ai-Min Zhu; Xue-Feng Yang; Cui-Hong Li; Yong Xu

2005-01-01

233

Dilution effect with inert gas in direct methanol synthesis from methane using nonthermal plasma  

Microsoft Academic Search

Direct methanol synthesis from CH4 and O2 has been experimentally studied using pulsed discharge plasma in a concentric-cylinder-type reactor. The methanol production was enhanced by dilution of source gas with inert gas, such as Ar, He. The methanol production became about 2.5 times larger at the dilution ratio of 2.5, and gradually decreased with increase of the dilution ratio, resulting

Mamoru Okumoto; Zhenzhou Su; Shinji Katsura; Akira Mizuno

1997-01-01

234

Effects of inert gas dilution of silane on plasma-deposited aSi:H films  

Microsoft Academic Search

Electrical, optical, and structural characterization of hydrogenated amorphous silicon films plasma-deposited from mixtures of SiH4 with different inert-gas diluents reveals substantial differences in a number of properties. A general trend of increasing defect density with atomic weight of the inert gas is observed. Of specific interest to device applications is the observation that high deposition rates can be achieved concurrently

J. C. Knights; R. A. Lujan; M. P. Rosenblum; D. K. Bieglesen; J. A. Reimer

1981-01-01

235

Effects of inert gas dilution of silane on plasma-deposited a-Si:H films  

NASA Astrophysics Data System (ADS)

Electrical, optical, and structural characterization of hydrogenated amorphous silicon films plasma-deposited from mixtures of SiH4 with different inert-gas diluents reveals substantial differences in a number of properties. A general trend of increasing defect density with atomic weight of the inert gas is observed. Of specific interest to device applications is the observation that high deposition rates can be achieved concurrently with low defect densities when helium is used as a diluent.

Knights, J. C.; Lujan, R. A.; Rosenblum, M. P.; Street, R. A.; Bieglesen, D. K.; Reimer, J. A.

1981-03-01

236

Features of plasma glow in low pressure terahertz gas discharge  

NASA Astrophysics Data System (ADS)

Investigations of the low pressure (1-100 Torr) gas discharge in the powerful (1 kW) quasi-optical terahertz (0.55 THz) wave beams were made. An intense afterglow was observed after the end of gyrotron terahertz radiation pulse. Afterglow duration significantly exceeded radiation pulse length (8 ?s). This phenomenon could be explained by the strong dependence of the collisional-radiative recombination rate (that is supposed to be the most likely mechanism of electron losses from the low pressure terahertz gas discharge) on electron temperature.

Bratman, V. L.; Golubev, S. V.; Izotov, I. V.; Kalynov, Yu. K.; Koldanov, V. A.; Litvak, A. G.; Razin, S. V.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G.

2013-12-01

237

[An expedient semi-automatic procedure for the preparation of large quantities of bioindicators especially for use in gas sterilization processes].  

PubMed

Bioindicators serve to test the efficacy of disinfection and sterilization procedures. Such indicators mostly consist of a support (filter paper, as a rule) to which micro-organisms have been fixed by drying. The authors have used a thread as support and a special apparatus for semi-automatic preparation of the bioindicators. The components of the device are either commercially available or may be prepared from commercially available material without difficulty. The principle of the method is as follows: The thread serving as the support is drawn slowly, at constant speed, through the suspension of test organisms and dried in an air stream immediately afterwards. The apparatus consists of a cylindrical glass tube of a few centimeters in diameter, an electric motor slowly rotating the cylinder, a fan, a magnetic stirrer, and an ice-water bath. A small vial containing the germ suspension is immersed in the ice-water bath. The vial is sealed by a screw cap with two glass tubes of about 3 mm inner diameter passing through it. One of the glass tubes being bent in its upper part reaches far down into the vial to leave just enough play for free rotation of a magnetic stirring rod. This tube serves to introduce the thread into the germ suspension. The second straight tube does not reach as far down as the first one. Its lower opening should not be immersed in the germ suspension. This tube serves as a guide for the returning thread. Preparation begins by winding the thread to be soaked with the suspension around the cylinder.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3901603

Spicher, G; Borchers, U

1985-06-01

238

Study of Gas and Plasma Conditions in the High Isp VASIMR Thruster  

NASA Astrophysics Data System (ADS)

Internal electrode-free VASIMR thruster [1-3] consists of three major sections: plasma production, plasma heating, and plasma exhaust. In our previous works [6-10] we have performed an extensive study of plasma dynamics in the plasma source. We have developed several models of helicon plasma discharge utilizing hydrogen (deuterium) gas, and analyzed its performance in the experimental set-up [4-5]. In the present work we are trying to expand and apply existing models to the helium gas propellant case. Though the specific impulse is somewhat lower with heavier helium atoms, but unlike hydrogenic species helium doesn't form molecules, and therefore shows less radiative losses. We extend 0-D plasma-chemistry, 1-D mixed-collisional and kinetic gas flow models [11] to characterize gas/plasma composition and condition in the helium helicon discharge. Recent experiments suggest that there is a strong dependence of both VASIMR 1st and 2nd stage performance on the magnetic field mirror ratio in the VX-10 experimental configuration. We study effects of the plasma particles trapping in a strong magnetic field and their acceleration by the combination of the mirror force and ambipolar potential for the typical VASIMR experiment conditions. We also discuss possibility for plasma instabilities and comment on the micro-scale plasma transport in the VASIMR thruster. [1] Chang Díaz F.R., "Research Status of The Variable Specific Impulse Magnetoplasma Rocket", Proc. 39th Annual Meeting of the Division of Plasma Physics (Pittsburgh, PA, 1997), Bulletin of APS, 42 (1997) 2057. [2] Chang Díaz, F. R., Squire, J. P., Carter, M., et al., `'Recent Progress on the VASIMR'', Proc. 41th Annual Meeting of the Division of Plasma Physics (Seattle, WA, 1999), Bulletin of APS, 44 (1999) 99. [3] Chang Díaz, F. R., Squire, J. P., Ilin, A. V., et al. "The Development of the VASIMR Engine", Proceedings of International Conference on Electromagnetics in Advanced Applications (ICEAA99), Sept. 13-17, 1999, Torino, Italy, (1999) 99-102. [4] F.R.Chang Diaz et al., "An Overview of Current Research on the VASIMR Engine", DPP-2000, Bull. APS, vol.45, 7 (2000) 129. [5] J.P.Squire, "Recent Experimental Results in the VX-10 Device", DPP-2000, Bull. APS, vol.45, 7 (2000) 130. [6] O.Batishchev and K.Molvig, "Kinetic Simulation of the high Isp Plasma Thruster", JPC-36, AIAA-3754 technical paper, Huntsville (2000) 11p. [7] O.Batishchev and K.Molvig, "Study of the Operational Regimes of the VASIMR Helicon Plasma Source", DPP- 2000, Quebec City, Canada, Bull. APS, 45, 7 (2000) 130. [8] O.Batishchev and K.Molvig, "Study of Mixed Collisionality Gas Flow in the VASIMR Thruster", DFD-2000, DC, USA, Bull. APS, 45, 9 (2000) 169. [9] O.Batishchev and K.Molvig, "Kinetic Model of a Helicon Plasma Source for VASIMR", ACME-39, AIAA-0963 technical paper, ASME-39, Reno, 2001. [10] O.Batishchev and K.Molvig "Kinetic study of the VASIMR thruster operational regimes", JPC-37, AIAA-3501 technical paper, Salt-Lake City, 2001. [11] O.Batishchev and K.Molvig, "Numerical study of plasma production in the VASIMR thruster", IEPC-01-208 paper, 27 Int. Electric Prop. Conf., Pasadena CA, 15-19 October, -19p, 2001.

Batishchev, O.; Molvig, K.

2002-01-01

239

Gas Kinetic Study of Magnetic Field Effects on Plasma Plumes  

E-print Network

continuum-based description and computation valid; ii) in the context of MHD framework, the generalized Ohm’s law must be used to capture all of the relevant physics. This work also continues the development of the Magneto Gas Kinetic Method (MGKM...

Ebersohn, Frans 1987-

2012-12-07

240

Non-Equilibrium EEDF in Gas Discharge Plasmas Osram Sylvania  

E-print Network

Jersey August 2-4 2005 #12;Electron Temperature in gas Discharge (Uniform electric field, Maxwellian EEDF are not in equilibrium with heating electric field #12;Hot electrons generated in a narrow zone has features of a non-self-sustained discharge with typically low electron temperature #12;Heating

Kaganovich, Igor

241

Affinity patterning of biomaterials using plasma gas discharge  

E-print Network

Patterned surfaces were prepared by combination of gas discharge and photolitographic processes. First a protein-repellent surface was prepared by glow discharge deposition of tri- and tetraglyme vapor on poly (ethylene terephtalate) surface, then on top of it fluorocarbon was deposited on selected domains by photolithography. Cell attachment was shown to be dependent of the surface hydrophilicity.

Goessl, A; Hoffman, A S; Jung, L

1996-01-01

242

Inactivation of Escherichia coli Using the Atmospheric Pressure Plasma Jet of Ar gas  

NASA Astrophysics Data System (ADS)

Germicidal treatments of Escherichia coli on Langmuir-Blodget (LB) agar were performed using the atmospheric pressure plasma jet sources of Ar gas in the ambient air. Shorter distances from the nozzle of the plasma jet device were more effective in achieving higher bactericidal effects on E. coli grown on LB agar. The surface temperature of the agar was monitored and the spectroscopic analysis of the plasma jet was performed in order to evaluate the factors contributing to the bactericidal effect, such as heating, UV emission, and radical formation caused by the plasma jet. Although the plasma jet raised the surface temperature of LB agar up to about 40 °C, the bactericidal effect was not observed. Moreover, the bactericidal effect of UV (200-300 nm) emitted from the plasma jet was negligible compared with the effects of ions and radical species generated by the atmospheric plasma. The results suggest that the ions and radical species generated by the atmospheric pressure plasma jet are critical for high bactericidal effects on E. coli.

Homma, Takeshi; Furuta, Masakazu; Takemura, Yuichiro

2013-03-01

243

Experimental study of the effect of gas nature on plasma arc cutting of mild steel  

NASA Astrophysics Data System (ADS)

This paper is devoted to the experimental investigation of arc cutting of mild steel using plasmas generated in gas and liquid media. Due to different chemical compositions, the examined media have different thermophysical properties, which affect the properties of the generated plasma and cutting performance. The experiments are performed on 15 mm mild steel plates using commercial equipment at 60 A to approach real operation conditions in application areas. The studied gases are chosen according to recommendations of the world's leading manufacturers of arc cutting equipment for mild steel. Specific differences between plasma gases are discussed from the point of view of properties of the gas and the generated plasma, amount of removed material, kerf shape and overall energy balance of the cutting process. The paper describes the role of exothermic reaction of iron oxidation for oxygen cutting and explains its neglect for liquid cutting. This paper explains the potential of facilitating the cutting process by modification of the plasma gas chemical composition and flow rate.

Kavka, T.; Mašláni, A.; Hrabovský, M.; K?enek, P.; Stehrer, T.; Pauser, H.

2013-06-01

244

Formation of a hydrogen plasma from an incandescently heated hydrogen-catalyst gas mixture with an anomalous afterglow duration  

Microsoft Academic Search

We report the generation of a plasma of hydrogen and certain alkali ions as recorded via EUV spectroscopy and the hydrogen Balmer and alkali line emissions in the visible range. Typically, a hydrogen plasma is generated and the emission of extreme ultraviolet light from hydrogen gas is achieved via a discharge at high voltage, a high power inductively-coupled plasma, or

Randell L. Mills; Takeyoshi Onuma; Ying Lu

2001-01-01

245

Investigation of methods for sterilization of potting compounds and mated surfaces  

NASA Technical Reports Server (NTRS)

The feasibility of using formaldehyde-liberating synthetic resins or polymers for the sterilization of potting compounds, mated and occluded areas, and spacecraft surfaces was demonstrated. The detailed study of interrelated parameters of formaldehyde gas sterilization revealed that efficient cycle conditions can be developed for the sterilization of spacecraft components. It was determined that certain parameters were more important than others in the development of cycles for specific applications. The use of formaldehyde gas for the sterilization of spacecraft components provides NASA with a highly efficient method which is inexpensive, reproducible, easily quantitated, materials compatible, operationally simple, generally non-hazardous and not thermally destructive.

Tulius, J. J.; Daley, D. J.; Phillips, G. B.

1972-01-01

246

Fundamentals of Discharge Initiation in Gas-Fed Pulsed Plasma Thrusters  

E-print Network

at the 29th International Electric Propulsion Conference, Princeton University October 31 ­ November 4, 2005 James E. Cooley and Edgar Y. Choueiri Electric Propulsion and Plasma Dynamics Laboratory (EPPDy. A GFPPT is a pulsed electromagnetic accelerator in which small puffs of gas are injected between two

Choueiri, Edgar

247

Plasma-assisted reduction of carbon dioxide in the gas phase  

Microsoft Academic Search

The reduction of carbon dioxide by hydrogen, which constitutes the reverse water-gas shift reaction, is an active area of research because of its connection with the production of methanol and other fuels. Representative references are given, that have been reported in the catalysis literature where most of this research is described. In contrast with this, studies dealing with the plasma-assisted

L. Maya

2000-01-01

248

Fast H in hydrogen mixed gas microwave plasmas when an atomic hydrogen supporting surface was present  

Microsoft Academic Search

Atomic hydrogen is heated to temperatures of up to two orders of magnitude greater than the electron temperature or the temperature of any other species in certain hydrogen mixed gas RF or glow discharge plasmas. A crucial test of energetic hydrogen chemistry regarding a resonant energy transfer or rt-mechanism (RTM) versus field acceleration models (FAM) as the basis of this

R. L. Mills; K. Akhtar

2010-01-01

249

Radiation from high-intensity ultrashort-laser-pulse and gas-jet magnetized plasma interaction.  

PubMed

Using a gas-jet flow, via the interaction between an ultrashort high-intensity laser pulse and plasma in the presence of a perpendicular external dc magnetic field, the short pulse radiation from a magnetized plasma wakefield has been observed. Different nozzles are used in order to generate different densities and gas profiles. The neutral density of the gas-jet flow measured with a Mach-Zehnder interferometer is found to be proportional to back pressure of the gas jet in the range of 1 to 8 atm. Strength of the applied dc magnetic field varies from 0 to 8 kG at the interaction region. The frequency of the emitted radiation with the pulse width of 200 ps (detection limit) is in the millimeter wave range. Polarization and spatial distributions of the experimental data are measured to be in good agreement with the theory based on the V(p)xB radiation scheme, where V(p) is the phase velocity of the electron plasma wave and B is the steady magnetic field intensity. Characteristics of the radiation are extensively studied as a function of plasma density and magnetic field strength. These experiments should contribute to the development of a new kind of millimeter wavelength radiation source that is tunable in frequency, pulse duration, and intensity. PMID:14525122

Dorranian, Davoud; Starodubtsev, Mikhail; Kawakami, Hiromichi; Ito, Hiroaki; Yugami, Noboru; Nishida, Yasushi

2003-08-01

250

Oxygen transport by gas permeation through the zirconia layer in plasma sprayed thermal barrier coatings  

Microsoft Academic Search

The specific permeability of oxygen in plasma sprayed zirconia has been measured to be approximately 10?16 m2, with some dependence on microstructure, and hence on spraying conditions. Permeability rises with increasing temperature, as expected, and differences of a factor of approximately 4 were observed between room temperature and 600 °C. Maximum oxygen fluxes through the top coat via gas permeation,

A. C. Fox; T. W. Clyne

2004-01-01

251

Dust-gas interactions and the infrared emission from hot astrophysical plasmas  

NASA Technical Reports Server (NTRS)

Environments where the presence of dust is primarily inferred from its collisional interactions with the ambient gas are reviewed with emphasis on environments typically encountered behind fast (100 km/s or greater) shocks and in hot (few 10 exp 5 K) plasmas in galactic halos, some elliptical galaxies, or the intergalactic medium of galaxy clusters. The discussion covers interactions between dust grains and a hot gas, grain temperatures and infrared emission, supernova remnants and supershells, and dust and hot gas in, around, and between galaxies. Finally, future prospects in the field are briefly discussed.

Dwek, Eli; Arendt, Richard G.

1992-01-01

252

Hybrid Particle-Continuum Methods for Nonequilibrium Gas and Plasma Flows  

SciTech Connect

Two different hybrid particle-continuum methods are described for simulation of nonequilibrium gas and plasma dynamics. The first technique, used for nonequilibrium hypersonic gas flows, uses either a continuum description or a particle method throughout a flow domain based on local conditions. This technique is successful in reproducing the results of full particle simulations at a small fraction of the cost. The second method uses a continuum model of the electrons combined with a particle description of the ions and atoms for simulating plasma jets. The physical accuracy of the method is assessed through comparisons with plasma plume measurements obtained in space. These examples illustrate that the complex physical phenomena associated with nonequilibrium conditions can be simulated with physical accuracy and numerical efficiency using such hybrid approaches.

Boyd, Iain D. [Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI (United States)

2011-05-20

253

Investigation of a Gas Jet-Produced Hollow Plasma Wakefield Accelerator  

SciTech Connect

The effect of ion motion and the need for practical positron propagation in a plasma wakefield accelerator (PWFA) have incited interest in hollow plasma channels. These channels are typically assumed to be cylindrically symmetric; however, a different geometry might be easier to achieve. The introduction of an obstruction into the outlet of a high Mach number gas jet can produce two parallel slabs of gas separated by a density depression. Here, there is a detailed simulation study of the density depression created in such a system. This investigation reveals that the density depression is insufficient at the desired plasma density. However, insights from the simulations suggest another avenue for the creation of the hollow slab geometry.

Kirby, N; Blumenfeld, I.; Hogan, M.J.; Siemann, R.H.; Walz, D.R.; /SLAC; Davidson, A.W.; Huang, C.; /UCLA

2009-05-21

254

Numerical simulation and experimental verification of gas streams feeding a gliding discharge plasma reactor  

NASA Astrophysics Data System (ADS)

The modular device for the waste utilization, using the pyrolytic-plasma method, consists of, among others, the plasma reactor operating on the gliding discharge principles. The reactor is applied to oxidize hydrocarbons created in the process of the waste pyrolysis. Thus, the plasma reactor operation influences significantly the qualitative and quantitative composition of the output gases. Finding the most advantageous construction of the plasma reactor and the process parameters ensures full and complete oxidation of hydrocarbons. In the waste utilization process, two streams of gases were introduced into the plasma reactor through the system of two coaxial nozzles. The first stream was a mixture of argon and hydrocarbons and the second one was oxygen. Two different methods of gas introduction were considered. Methane was used as a model hydrocarbon both in calculations and in the experiments. On the basis of numerical calculations (Fluent commercial program), it was found that the most advantageous method of gas introduction into the reactor was the one in which the mixture of argon and hydrocarbons was introduced through the central nozzle and the oxygen was introduced through the outer one. This conclusion was confirmed experimentally. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

Opali?ska, Teresa; Majdak, Ma?gorzata; Piechna, Janusz; Selerowicz, Witold; Wnek, Bart?omiej

2013-02-01

255

Magnetic susceptibility and Landau diamagnetism of a quantum collisional Plasmas with arbitrary degree of degeneration of electronic gas  

E-print Network

The kinetic description of magnetic susceptibility and Landau diamagnetism of quantum collisional plasmas with any degeration of electronic gas is given. The correct expression of electric conductivity of quantum collisional plasmas with any degeration of electronic gas (see A. V. Latyshev and A. A. Yushkanov, Transverse electrical conductivity of a quantum collisional plasma in the Mermin approach. - Theor. and Math. Phys., V. 175(1):559-569 (2013)) is used.

Latyshev, A V

2013-01-01

256

Effects of inert gas dilution of 1,3 butadiene on plasma deposition of aC:H films  

Microsoft Academic Search

Amorphous hydrogenated carbon films (a-C:H) were deposited by the plasma decomposition of mixtures of 1,3 butadiene with different inert gas diluents (Ar, Ne, and He). Several characteristics of the plasma and the deposited films were investigated for deposition gas mixtures ranging in concentration from 0% to 90% of the diluent. Measurement of the optical emission from the plasma indicated the

Jayshree Seth; S. V. Babu

1993-01-01

257

Plasma-dynamic and optical characteristics of magnetron-type cylindrical gas discharge under conditions of titanium nitride film synthesis  

NASA Astrophysics Data System (ADS)

The results of comprehensive experimental investigation into the plasma-dynamic and optical characteristics of a magnetron cylindrical gas discharge are reported. Experiments are carried out under computer monitoring of the spectrum radiated by the discharge plasma in the visual range. Optimal conditions for TiN binary compound synthesis are found. They are provided by maintaining the intensities of the reactant and plasma-forming gas spectral lines. Characterization of synthesized films is given.

Blonskii, I. V.; Goncharov, A. A.; Demchishin, A. V.; Evsyukov, A. N.; Kostin, E. G.; Sal'Nikov, V. A.; Tereshchenko, A. G.; Tkachenko, L. N.

2009-07-01

258

Nonlinear structure of the diffusing gas-metal interface in a thermonuclear plasma.  

PubMed

This Letter describes the theoretical structure of the plasma diffusion layer that develops from an initially sharp gas-metal interface. The layer dynamics under isothermal and isobaric conditions is considered so that only mass diffusion (mixing) processes can occur. The layer develops a distinctive structure with asymmetric and highly nonlinear features. On the gas side of the layer the diffusion coefficient goes nearly to zero, causing a sharp "front," or well defined boundary between mix layer and clean gas with similarities to the Marshak thermal waves. Similarity solutions for the nonlinear profiles are found and verified with full ion kinetic code simulations. A criterion for plasma diffusion to significantly affect burn is given. PMID:25325648

Molvig, Kim; Vold, Erik L; Dodd, Evan S; Wilks, Scott C

2014-10-01

259

Nonlinear Structure of the Diffusing Gas-Metal Interface in a Thermonuclear Plasma  

NASA Astrophysics Data System (ADS)

This Letter describes the theoretical structure of the plasma diffusion layer that develops from an initially sharp gas-metal interface. The layer dynamics under isothermal and isobaric conditions is considered so that only mass diffusion (mixing) processes can occur. The layer develops a distinctive structure with asymmetric and highly nonlinear features. On the gas side of the layer the diffusion coefficient goes nearly to zero, causing a sharp "front," or well defined boundary between mix layer and clean gas with similarities to the Marshak thermal waves. Similarity solutions for the nonlinear profiles are found and verified with full ion kinetic code simulations. A criterion for plasma diffusion to significantly affect burn is given.

Molvig, Kim; Vold, Erik L.; Dodd, Evan S.; Wilks, Scott C.

2014-10-01

260

Gas-filled targets for large scalelength plasma interaction experiments on Nova  

SciTech Connect

Stimulated Brillouin backscatter from large scale length gas-filled targets has been measured on Nova. These targets were designed to approximate conditions in indirect drive ignition target designs in underdense plasma electron density (n{sub e}{approximately}10{sup 21}/cm{sup 3}), temperature (T{sub e}>3 keV), and gradient scale lengths (L{sub n}{approximately} mm, L{sub v}>6 mm) as well as calculated gain for stimulated Brillouin scattering (SBS). The targets used in these experiments were gas-filled balloons with polyimide walls (gasbags) and gas-filled hohlraums. Detailed characterization using x-ray imaging and x-ray and optical spectroscopy verifies that the calculated plasma conditions are achieved. Time-resolved SBS backscatter from these targets is <3% for conditions similar to ignition target designs.

Powers, L.V.; Berger, R.L.; Munro, D.H. [and others

1994-11-01

261

Ionized gas (plasma) delivery of reactive oxygen species (ROS) into artificial cells  

NASA Astrophysics Data System (ADS)

This study was designed to enhance our understanding of how reactive oxygen species (ROS), generated ex situ by ionized gas (plasma), can affect the regulation of signalling processes within cells. A model system, comprising of a suspension of phospholipid vesicles (cell mimics) encapsulating a ROS reporter, was developed to study the plasma delivery of ROS into cells. For the first time it was shown that plasma unequivocally delivers ROS into cells over a sustained period and without compromising cell membrane integrity. An important consideration in cell and biological assays is the presence of serum, which significantly reduced the transfer efficiency of ROS into the vesicles. These results are key to understanding how plasma treatments can be tailored for specific medical or biotechnology applications. Further, the phospholipid vesicle ROS reporter system may find use in other studies involving the application of free radicals in biology and medicine.

Hong, Sung-Ha; Szili, Endre J.; Jenkins, A. Toby A.; Short, Robert D.

2014-09-01

262

Process Conditions and Microstructures of Ceramic Coatings by Gas Phase Deposition Based on Plasma Spraying  

NASA Astrophysics Data System (ADS)

Plasma spraying at very low pressure (50-200 Pa) is significantly different from atmospheric plasma conditions (APS). By applying powder feedstock, it is possible to fragment the particles into very small clusters or even to evaporate the material. As a consequence, the deposition mechanisms and the resulting coating microstructures could be quite different compared to conventional APS liquid splat deposition. Thin and dense ceramic coatings as well as columnar-structured strain-tolerant coatings with low thermal conductivity can be achieved offering new possibilities for application in energy systems. To exploit the potential of such a gas phase deposition from plasma spray-based processes, the deposition mechanisms and their dependency on process conditions must be better understood. Thus, plasma conditions were investigated by optical emission spectroscopy. Coating experiments were performed, partially at extreme conditions. Based on the observed microstructures, a phenomenological model is developed to identify basic growth mechanisms.

Mauer, G.; Hospach, A.; Zotov, N.; Vaßen, R.

2013-03-01

263

Contrib. Plasma Phys. 51, No. 2-3, 293 296 (2011) / DOI 10.1002/ctpp.201000061 LTE Experimental Validation in a Gas Metal Arc Welding Plasma  

E-print Network

Conversion d'Energie); 118 route de Narbonne, F-31062 Toulouse Cedex 9, France 3 Universit�e des Sciences et Spectroscopy, Boltzmann Plot, Sola method, LTE. During gas metal arc welding (GMAW), the plasma obtained has

264

A combined plasma photolysis (CPP) method for removal of CS 2 from gas streams at atmospheric pressure  

Microsoft Academic Search

A combined plasma photolysis (CPP) reactor that utilizes a dielectric barrier discharge (DBD) plasma and 207nm UV radiation from discharge-driven KrBr? excimers was designed and constructed. Gas streams containing CS2 were treated with stand-alone DBD and CPP at atmospheric pressure. In comparison to DBD, CPP greatly enhanced the removal efficiency at the same applied voltage, waste gas concentration and gas

Hao Jie Fang; Hui Qi Hou; Lan Yan Xia; Xiao Hong Shu; Ren Xi Zhang

2007-01-01

265

Characterization and gas temperature measurements of a waveguide-based microwave plasma torch  

NASA Astrophysics Data System (ADS)

Research to characterize a microwave plasma torch was initiated at Penn State University. Microwave power input into the device initiates and sustains plasma in an argon gas jet issuing from a copper nozzle into the ambient atmosphere. Protruding through a rectangular waveguide, the nozzle acts to enhance the local electric field when microwaves are excited in the waveguide. The plasma resembles a small flame, approximately 2--4 cm in length and less than 1 cm in total diameter. The primary research interests which have driven experimental design and characterization of the torch include (1) increasing plasma jet control via improved impedance matching; (2) reducing the erosion of the nozzle tips; and (3) determining the viability of applying the Penn State Microwave Plasma Torch (PSMPT) to the cutting and melting of materials via gas temperature measurements. Literature on the similar microwave torches---particularly, those of the single-electrode plasma (SEP) type---was reviewed. Several design issues were encountered during early testing with the torch. Impedance matching and nozzle erosion presented the most significant obstacles. Poor impedance matching was overcome most effectively with an automatic tuner that could determine a match quickly. Nozzle erosion is not often addressed in the literature on SEPs. However, significant erosion was a limiting factor in early tests with the torch. More recent testing reveals that erosion can be mitigated by addition of a secondary flow of argon around the primary nozzle gas flow. Gas temperature in the plasma was deduced via OH rotational temperature measurements. Molecular nitrogen spectral interference with the OH spectra required fitting both the OH and N2 second positive system in the region of 305--318 nm. The results of this testing indicate an OH rotational temperature---and assumed gas temperature---between 2700--3400 K. These results indicate that the torch should prove useful in cutting and heat-treatment applications for some materials. Recommended areas of future study include examining the plasma for possible filamentation and enhanced spectroscopic diagnostics.

Hammond, Peter J.

266

Removal of Elemental Mercury from a Gas Stream Facilitated by a Non-Thermal Plasma Device  

SciTech Connect

Mercury generated from anthropogenic sources presents a difficult environmental problem. In comparison to other toxic metals, mercury has a low vaporization temperature. Mercury and mercury compounds are highly toxic, and organic forms such as methyl mercury can be bio-accumulated. Exposure pathways include inhalation and transport to surface waters. Mercury poisoning can result in both acute and chronic effects. Most commonly, chronic exposure to mercury vapor affects the central nervous system and brain, resulting in neurological damage. The CRE technology employs a series of non-thermal, plasma-jet devices to provide a method for elemental mercury removal from a gas phase by targeting relevant chemical reactions. The technology couples the known chemistry of converting elemental mercury to ionic compounds by mercury-chlorine-oxygen reactions with the generation of highly reactive species in a non-thermal, atmospheric, plasma device. The generation of highly reactive metastable species in a non-thermal plasma device is well known. The introduction of plasma using a jet-injection device provides a means to contact highly reactive species with elemental mercury in a manner to overcome the kinetic and mass-transfer limitations encountered by previous researchers. To demonstrate this technology, WRI has constructed a plasma test facility that includes plasma reactors capable of using up to four plasma jets, flow control instrumentation, an integrated control panel to operate the facility, a mercury generation system that employs a temperature controlled oven and permeation tube, combustible and mercury gas analyzers, and a ductless fume hood designed to capture fugitive mercury emissions. Continental Research and Engineering (CR&E) and Western Research Institute (WRI) successfully demonstrated that non-thermal plasma containing oxygen and chlorine-oxygen reagents could completely convert elemental mercury to an ionic form. These results demonstrate potential the application of this technology for removing elemental mercury from flue gas streams generated by utility boilers. On an absolute basis, the quantity of reagent required to accomplish the oxidation was small. For example, complete oxidation of mercury was accomplished using a 1% volume fraction of oxygen in a nitrogen stream. Overall, the tests with mercury validated the most useful aspect of the CR&E technology: Providing a method for elemental mercury removal from a gas phase by employing a specific plasma reagent to either increase reaction kinetics or promote reactions that would not have occurred under normal circumstances.

Charles Mones

2006-12-01

267

Cosmology of "Visible" Sterile Neutrinos  

E-print Network

We point out that in scenarios with a low reheating temperature $T_R cosmological bounds become less stringent than usually assumed, allowing sterile neutrinos to be ``visible'' in future experiments. For example, the sterile neutrino required by the LSND result does not have any cosmological problem within these scenarios.

Graciela B. Gelmini

2004-12-21

268

9 CFR 109.2 - Sterilizers.  

Code of Federal Regulations, 2010 CFR

... 2010-01-01 2010-01-01 false Sterilizers. 109.2 Section 109.2 Animals and...PASTEURIZATION AT LICENSED ESTABLISHMENTS § 109.2 Sterilizers. Steam and dry-heat sterilizers used in connection with the...

2010-01-01

269

Investigation on plasma-quenching efficiency of various gases using the inductively coupled thermal plasma technique: effect of various gas injection on Ar thermal ICP  

Microsoft Academic Search

Application of the inductively coupled thermal plasma (ICTP) technique was proposed for investigating plasma-quenching efficiency of various gases including the arc-quenching medium of SF6. The ICTP enables us to study fundamentally the effect of gas injection on thermal plasma without any impurities because it has no electrode. Seven kinds of gases including CO2, SF6 and environmentally benign gases (N2, O2,

Y. Tanaka; T. Sakuta

2002-01-01

270

Effects of shielding gas compositions on arc plasma and metal transfer in gas metal arc welding  

NASA Astrophysics Data System (ADS)

This article presents the effects of shielding gas compositions on the transient transport phenomena, including the distributions of temperature, flow velocity, current density, and electromagnetic force in the arc and the metal, and arc pressure in gas metal arc welding of mild steel at a constant current input. The shielding gas considered includes pure argon, 75% Ar, 50% Ar, and 25% Ar with the balance of helium. It is found that the shielding gas composition has significant influences on the arc characteristics; droplet formation, detachment, transfer, and impingement onto the workpiece; and weld pool dynamics and weld bead profile. As helium increases in the shielding gas, the droplet size increases but the droplet detachment frequency decreases. For helium-rich gases, the current converges at the workpiece with a "ring" shape which produces non-Gaussian-like distributions of arc pressure and temperature along the workpiece surface. Detailed explanations to the physics of the very complex but interesting transport phenomena are given.

Rao, Z. H.; Liao, S. M.; Tsai, H. L.

2010-02-01

271

Interpretation of the gas flow field modification induced by guided streamer (‘plasma bullet’) propagation  

NASA Astrophysics Data System (ADS)

Atmospheric-pressure non-equilibrium plasmas of noble gases in the form of ‘bullets’ have attracted considerable attention, against cold low-pressure or thermal atmospheric-pressure plasmas, for multidisciplinary scientific fields such as material science and biomedicine, due to their unique compatible features. A key factor for the efficiency of most of these systems is the interaction between the noble-gas channel, where the ‘bullets’ (streamers) propagate, and the plasma itself. It is the object of this paper to demonstrate this interaction and to provide the explanation on the gas flow field modification induced by the plasma ignition. A three-dimensional numerical model incorporating most of the governing equations, schlieren imaging and UV–visible high-resolution optical emission spectroscopy are applied. In accordance with the present results, the mechanism leading to the flow field alteration is clearly related to the electrohydrodynamic force, while it is demonstrated that the gas temperature plays a minor role.

Papadopoulos, P. K.; Vafeas, P.; Svarnas, P.; Gazeli, K.; Hatzikonstantinou, P. M.; Gkelios, A.; Clément, F.

2014-10-01

272

Investigation of a Light Gas Helicon Plasma Source for the VASIMR Space Propulsion System  

NASA Technical Reports Server (NTRS)

An efficient plasma source producing a high-density (approx.10(exp 19/cu m) light gas (e.g. H, D, or He) flowing plasma with a high degree of ionization is a critical component of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept. We are developing an antenna to apply ICRF power near the fundamental ion cyclotron resonance to further accelerate the plasma ions to velocities appropriate for space propulsion applications. The high degree of ionization and a low vacuum background pressure are important to eliminate the problem of radial losses due to charge exchange. We have performed parametric (e.g. gas flow, power (0.5 - 3 kW), magnetic field , frequency (25 and 50 MHz)) studies of a helicon operating with gas (H2 D2, He, N2 and Ar) injected at one end with a high magnetic mirror downstream of the antenna. We have explored operation with a cusp and a mirror field upstream. Plasma flows into a low background vacuum (<10(exp -4) torr) at velocities higher than the ion sound speed. High densities (approx. 10(exp 19/cu m) have been achieved at the location where ICRF will be applied, just downstream of the magnetic mirror.

Squire, J. P.; Chang-Diaz, F. R.; Jacobson, V. T.; Glover, T. W.; Baity, F. W.; Carter, M. D.; Goulding, R. H.; Bengtson, R. D.; Bering, E. A., III

2003-01-01

273

Investigation of a Light Gas Helicon Plasma Source for the VASIMR Space Propulsion System  

NASA Astrophysics Data System (ADS)

An efficient plasma source producing a high-density (˜1019 m-3) light gas (e.g. H, D, or He) flowing plasma with a high degree of ionization is a critical component of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept. The high degree of ionization and a low neutral background pressure are important to eliminate the problem of radial loss and axial drag due to charge exchange. We have performed parametric (e.g. gas flow, power (0.5 - 3 kW), and magnetic field studies of a helicon operating with gas (D2 or He) injected at one end, with a high magnetic mirror downstream of the antenna. The downstream mirror field has little effect on the exhaust flux up to a mirror ratio of 10. We have explored operation with a cusp and a mirror field upstream. The application of a cusp increases the plasma flux in the exhaust by a factor of two. Plasma flows into a large (5 m3) vacuum (< 10-4 torr) chamber at velocities higher than the ion sound speed. High densities (˜ 1019 m-3) have been achieved at the location where ICRF will be applied, just downstream of the magnetic mirror.

Squire, Jared P.; Chang-Diaz, Franklin R.; Jacobson, Verlin T.; Glover, Tim W.; Baity, F. Wally; Carter, Mark D.; Goulding, Richard H.; Bengtson, Roger D.; Bering, Edgar A.

2003-12-01

274

Xenon Additives Detection in Helium Micro-Plasma Gas Analytical Sensor  

NASA Astrophysics Data System (ADS)

Electron energy spectra of Xe atoms at He filled micro-plasma afterglow gas analyzer were observed using Collisional Electron Spectroscopy (CES) method [1]. According to CES, diffusion path confinement for characteristic electrons makes it possible to measure electrons energy distribution function (EEDF) at a high (up to atmospheric) gas pressure. Simple geometry micro-plasma CES sensor consists of two plane parallel electrodes detector and microprocessor-based acquisition system providing current-voltage curve measurement in the afterglow of the plasma discharge. Electron energy spectra are deduced as 2-nd derivative of the measured current-voltage curve to select characteristic peaks of the species to be detected. Said derivatives were obtained by the smoothing-differentiating procedure using spline least-squares approximation of a current-voltage curve. Experimental results on CES electron energy spectra at 10-40 Torr in pure He and in admixture with 0.3% Xe are discussed. It demonstrates a prototype of the new miniature micro-plasma sensors for industry, safety and healthcare applications. [1]. A.A.Kudryavtsev, A.B.Tsyganov. US Patent 7,309,992. Gas analysis method and ionization detector for carrying out said method, issued December 18, 2007.

Tsyganov, Alexander; Kudryavtsev, Anatoliy; Mustafaev, Alexander

2012-10-01

275

REVIEWS OF TOPICAL PROBLEMS: Vortices in a gas-discharge plasma  

NASA Astrophysics Data System (ADS)

Processes of vortex generation in a weakly ionized gas are reviewed in circumstances where a high-speed flow propagates along the gas discharge and acoustic waves interact with a positive column. Results on the effect of longitudinal gas flow in the positive-column properties are presented. It is shown that in certain conditions the gas flow in the positive column gives rise to vortices that cause the plasma to mix radially, producing a uniformly excited gas at high pressures. Results concerning the interaction of acoustic waves with low-temperature plasma are reviewed, and the acoustic-stimulated formation of vortex motion leading to an uncontracted discharge at elevated pressures is discussed. Also examined are flashes of superluminescence in an argon discharge caused by an abrupt transition of a positive column containing acoustic vortices from the uncontracted state to the contracted one at heightened pressures; this transition is understood to occur because of the turbulent-to-laminar transition in the acoustic flow. Finally, a gas-discharge acoustically induced laser is described.

Aramyan, A. R.; Galechyan, G. A.

2007-11-01

276

[Sterilization of mentally retarded girls].  

PubMed

About 1000 sterilizations are performed in mentally retarded women in Germany every year out of about 30,000-50,000 operations. Considering that 10 out of 1000 people are mentally retarded, they are overrepresented in this procedure. There are no clear regulations concerning their sterilization because of the historical antecedents of abuse of the rights of the mentally retarded. A 1933 law about hereditary health resulted in the forced sterilization of 300,000-400,000 persons mostly based on ideological indications. During the 1972 reform of the penal code the attempt to regulate sterilization with abortion and set very stringent conditions for minors and competent persons did not succeed. In 1987 federal medical association guidelines and the Einbecker recommendations were published permitting sterilization if it was in the well-meant interest of the mentally retarded person and the indications analogous to abortion could be considered. The consent of legal representative, guardian, and possibly both parents had to be secured, and the guardian court had to be given prior notice. The patient had to be advised and without her consent the operation could not be carried out. A draft proposal to become law in 1992 would forbid sterilization of minors: the consent of the guardian court is needed for incompetents of age if pregnancy would likely result without sterilization and it could not be prevented by other means. The handicapped oppose the sterilization of mentally retarded and the use of genetical criteria laid down in the regulation for indications for legal abortion. In 1990 the federal parliament passed the law on the rights of guardianship and care for those of age forbidding forced sterilization and sterilization of minors. This legislation will give clear guidelines for doctors. Some legal uncertainties still exist that can be used responsibly for the interest of the patient. PMID:1743571

Lenard, H G; Müller, K

1991-04-01

277

Cooling effect on hot antiproton plasma using buffer gas cloud. Simbuca - setup and simulations  

E-print Network

In this work I investigated the sympathetic cooling effect of antipro- tons with a plasma of charged anions in a Penning trap. From the AD (antiproton decelerator) antiprotons are decelerated to 5.5MeV. To get them further decelerated we trap the antiprotons inside the penning trap where we cool them down even further using a buffer gas which consists of charged plasma anions which helps us cool the antiprotons. For this work I used the open source simulations program Simbuca

Roshkovski, Dejan

2014-01-01

278

Measurements of plasma parameters in atmospheric helium plasma detectors for gas chromatograph  

Microsoft Academic Search

Summary form only given. In the field of chemical analysis, the gas chromatograph (GC) has been widely used because of its flexibility, short measurement time and low running cost. Recently, high-sensitive detection is required for further improvement of analytical performance. To realize high sensitivity, excellent detector for GC is needed. Until now, many types of detectors have been developed. Thermal

Y. Takahashi; Y. Nagata; H. Miyahara; A. Okino; O. Fujita; Y. Toyoura

2010-01-01

279

Characteristics of laser-produced plasmas in a gas filled chamber and in a gas jet by using a long pulse laser  

Microsoft Academic Search

The dynamics of the laser-produced plasma in a gas filled chamber and in a gas jet were investigated using a relatively low intensity laser (I<=5×1012 W\\/cm2) with long pulse duration (7 ns). Visualization methods such as the Mach-Zehnder interferometry and the shadow imaging were employed to characterize the shock velocity, electron densities, and temperatures in the laser-produced plasma. The electron

J. U. Kim; H. J. Lee; C. Kim; G. H. Kim; H. Suk

2003-01-01

280

Characteristics of laser-produced plasmas in a gas filled chamber and in a gas jet by using a long pulse laser  

Microsoft Academic Search

The dynamics of the laser-produced plasma in a gas filled chamber and in a gas jet were investigated using a relatively low intensity laser (I?5×1012 W\\/cm2) with long pulse duration (7 ns). Visualization methods such as the Mach–Zehnder interferometry and the shadow imaging were employed to characterize the shock velocity, electron densities, and temperatures in the laser-produced plasma. The electron

J. U. Kim; H. J. Lee; C. Kim; G. H. Kim; H. Suk

2003-01-01

281

RF gas plasma source development for heavy ion fusion  

SciTech Connect

Presently the Heavy Ion Fusion Virtual National Laboratory is researching ion sources and injector concepts to understand how to optimize beam brightness over a range of currents (50-2000 mA argon equivalent). One concept initially accelerates millimeter size, milliamp beamlets to 1 MeV before merging them into centimeter size, ampere beams. Computer simulations have shown the final brightness of the merged beams is dominated by the emittance growth of the merging process, as long as the beamlets ion temperature is below a few eV. Thus, a RF multicusp source capable of high current density can produce beams with better brightness compared to ones extracted from a colder source with a large aperture and lower current density. As such, experiments have begun to develop a RF multicusp source capable of delivering one amp of extracted beam current. It is expected that it will require 10 kW of 13 MHz RF power delivered via a quartz shielded, one and half turn, four inch diameter antenna. Important considerations in the development of the source include the dependence of current density and beam ion temperature on consumed RF power and gas pressure. A fast rise time ({approx}100 ns) for the extracted beam pulse must also be achieved. Progress on these experiments will be presented.

Ahle, L.E.; Hall, R.P.; Molvik, A.W.

2002-02-22

282

Increasing plasma waveguide production efficiency in H2 gas jet by cryogenically cooling the gas jet  

E-print Network

. The ignitor-heater scheme consists of a short and a long laser pulses to produce and heat electrons the interaction length in laser-plasma interaction is the key factor to the success of many important applications, such as the laser-driven electron accelerator, soft x-ray laser, and high harmonic generation. In our experiment, we

283

Registration of gas impurities in nonlocal plasma of helium microdischarge by an additional electrode — sensor  

NASA Astrophysics Data System (ADS)

Identification of gas impurities in helium by selective registration of groups of fast electrons created in Penning ionization of impurities atoms or molecules by metastable helium atoms at pressures of 7-40 Torr is realized. The collisional electron spectroscopy (CES) method is applied and is experimentally verified. Identification of impurities atoms and molecules is accomplished in collisional regime of movement of the particles, where the different groups of electrons have no time to relax in energy by collisions in the volume and behave independently of each other. An original design of microplasma gas analyzer is proposed, containing only nonlocal negative glow plasma of a short dc microdischarge. Registration of the energy spectra of penning electrons by means of an additional electrode-sensor, located at the boundary of the discharge volume is performed. The sensor has large collecting area compared to classical Langmuir probes, contributing to significant enhancement in the measurements sensitivity. Maxima in the EEDF are recorded in helium with small admixtures of krypton, argon and air. The obtained maxima appear at low discharge currents and at characteristic energies corresponding exactly to the expected maxima for penning electrons of the known gas impurities used. The gas analyser is compact, simple in technical performance, has high sensitivity and its size is dramatically reduced compared to the existing devices for gas analysis. This work is an approach to the development of microdischarge gas analyzers for gas impurities detection like poison gases, gas pollutions in the atmosphere or in the industry etc.

Kudryavtsev, A.; Pramatarov, P.; Stefanova, M.; Khromov, N.

2012-07-01

284

Calculation of force exerted by the Ohmic plasma channel on a relativistic electron beam propagating in a dense gas-plasma medium  

NASA Astrophysics Data System (ADS)

The problem on the interaction of an Ohmic plasma channel displaced in the transverse direction with a paraxial azimuthally symmetric relativistic electron beam propagating in a dense gas-plasma medium is considered. The formula for determining the force of the beam-plasma interaction is derived using the "hard" model of the beam and the channel in the case of an arbitrary displacement of the symmetry axis of the plasma channel relative to the corresponding axis of the beam. The forces are calculated in the Bennett and Gauss approximations for the radial profiles of the beam and the channel.

Manuilov, A. S.

2013-10-01

285

Genetically engineered cytoplasmic male sterility.  

PubMed

Cytoplasmic male sterility, conditioned by some maternally inherited plant mitochondrial genomes, is the most expedient method to produce uniform populations of pollen-sterile plants on a commercial scale. Plant mitochondrial genomes are not currently amenable to genetic transformation, but genetic manipulation of the plastid genome allows engineering of maternally inherited traits in some species. A recent study has shown that the Acinetobacter beta-ketothiolase gene, expressed in the Nicotiana tabacum plastid, conditions maternally inherited male sterility, laying the groundwork for new approaches to control pollen fertility in crop plants. PMID:16356756

Chase, Christine D

2006-01-01

286

Fast Plasma Shutdowns By Massive Hydrogen, Noble and Mixed-Gas Injection in DIII-D  

NASA Astrophysics Data System (ADS)

Experiments conducted with hydrogenic, noble and mixed (H2 + Ar and D2 + Ne) gases injected into H-mode plasmas are described. Gas species, quantity, delivery rate and intrinsic and added impurities (mixtures) all affect the disruption mitigation attributes of the resulting fast plasma shutdowns. With sufficient quantity, effective mitigation is obtained for all species. Optimal results for disruption and runaway avalanche mitigation are with 3x10^22 He delivery in ˜2 ms. This yields a favorable combination of moderately-fast current quench, high free-electron densities, ˜2x10^21,m-3, gas assimilation fractions ˜0.3 and avalanche suppression ratios, ne/nRB˜0.1. Favorable scaling of assimilation with increasing quantity is seen for all low-Z gases. The experiments provide validation data for emerging MHD/radiation simulation models and insight about design of injection systems for disruption and avalanche mitigation in ITER.

Wesley, J. C.; van Zeeland, M. A.; Evans, T. E.; Humphreys, D. A.; Hyatt, A. W.; Parks, P. B.; Strait, E. J.; Wu, W.; Hollmann, E. M.; Boedo, J. A.; Izzo, V. A.; James, A. N.; Moyer, R. A.; Rudakov, D. L.; Yu, J. H.; Jernigan, T. C.; Baylor, L. R.; Combs, S. K.; Groth, M.

2008-11-01

287

Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode  

PubMed Central

Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 ?F, 50 to 200 nH, and 1 to 3 kV, respectively. PMID:21267082

Poehlmann, Flavio R.; Cappelli, Mark A.; Rieker, Gregory B.

2010-01-01

288

Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode  

NASA Astrophysics Data System (ADS)

Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 ?F, 50 to 200 nH, and 1 to 3 kV, respectively.

Poehlmann, Flavio R.; Cappelli, Mark A.; Rieker, Gregory B.

2010-12-01

289

Effect of gas puffing from different side on lower hybrid wave-plasma coupling in experimental advanced superconductive tokamak  

NASA Astrophysics Data System (ADS)

Effect of gas puffing from electron-side and ion-side on lower hybrid wave (LHW)-plasma is investigated in experimental advanced superconductive tokamak for the first time. Experimental results with different gas flow rates show that electron density at the grill is higher in the case of gas puffing from electron-side; consequently, a lower reflection coefficient is observed, suggesting better effect of puffing from electron-side on LHW-plasma. The difference in edge density between electron- and ion-side cases suggests that local ionization of puffed gas plays a dominant role in affecting the density at the grill due to different movement direction of ionized electrons and that part of gas has been locally ionized near the gas pipe before diffusing into the grill region. Such difference could be enlarged and important in ITER due to the improvement of plasma parameters and LHW power.

Ding, B. J.; Kong, E. H.; Zhang, T.; Ekedahl, A.; Li, M. H.; Zhang, L.; Wei, W.; Li, Y. C.; Wu, J. H.; Xu, G. S.; Zhao, H. L.; Wang, M.; Gong, X. Z.; Shan, J. F.; Liu, F. K.; EAST Team

2013-10-01

290

Effect of gas puffing from different side on lower hybrid wave-plasma coupling in experimental advanced superconductive tokamak  

SciTech Connect

Effect of gas puffing from electron-side and ion-side on lower hybrid wave (LHW)-plasma is investigated in experimental advanced superconductive tokamak for the first time. Experimental results with different gas flow rates show that electron density at the grill is higher in the case of gas puffing from electron-side; consequently, a lower reflection coefficient is observed, suggesting better effect of puffing from electron-side on LHW-plasma. The difference in edge density between electron- and ion-side cases suggests that local ionization of puffed gas plays a dominant role in affecting the density at the grill due to different movement direction of ionized electrons and that part of gas has been locally ionized near the gas pipe before diffusing into the grill region. Such difference could be enlarged and important in ITER due to the improvement of plasma parameters and LHW power.

Ding, B. J.; Kong, E. H.; Li, M. H.; Zhang, L.; Wei, W.; Li, Y. C.; Wu, J. H.; Xu, G. S.; Wang, M.; Gong, X. Z.; Shan, J. F.; Liu, F. K. [Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031 (China)] [Institute of Plasma Physics, Chinese Academy of Science, Hefei 230031 (China); Zhang, T. [School of Physics, Hefei University of Technology, Hefei 230009 (China)] [School of Physics, Hefei University of Technology, Hefei 230009 (China); Ekedahl, A. [CEA, IRFM, 13108 St. Paul-lez-Durance (France)] [CEA, IRFM, 13108 St. Paul-lez-Durance (France); Zhao, H. L. [University of Science and Technology of China, Hefei 230026 (China)] [University of Science and Technology of China, Hefei 230026 (China); Collaboration: EAST Team

2013-10-15

291

Characteristics of impact-generated plasma with different electron temperature and gas temperature  

NASA Astrophysics Data System (ADS)

The characteristics of the plasma with difference between the electron temperature and gas temperature were investigated and the relationship between the plasma ionization degree and the internal energy of a system was obtained. A group of equations included the chemical reaction equilibrium equation, the chemical reaction rate equation and the energy conservation equation were adopted to calculate the electron density, the electron temperature and the atom temperature with a given internal energy. These equations combined with Navier-Stokes (N-S) equations is solved by a smooth particle hydrodynamic (SPH) code. The charges generated in hypervelocity impacts with five different velocities are calculated and verified with the empirical formulas. The influence of a critical velocity for plasma generation is considered in the empirical formula and the parameters are fitted by the numerical results. By comparing with the results in reference, the fitted new empirical formula is verified to be reasonable and useful for a wide range of impact velocity.

Li, Jianqiao; Song, Weidong; Ning, Jianguo; Tang, Huiping

2014-07-01

292

Influence of internal cold gas flow and of nozzle contour on spray properties of an atmospheric plasma spray torch  

SciTech Connect

With an automated Laser Doppler Anemometry (LDA) equipment trajectories, distributions and velocities of spray particles were measured operating a plasma spray torch under atmospheric pressure conditions. For this purpose a standard APS torch (PT F4) was used, applying different gas distribution rings and nozzle modifications to study the influence of internal plasma gas flow and of plasma jet formation. The main results are: (1) An inclined injection of the plasma cold gas results in a considerable spin of the plasma jet and a significant deviation of the particle trajectories around the plasma jet center. (2) With a plasma cold gas injection parallel to the torch axis no spin is observable, but torch voltage and the plasma jet enthalpy show considerably diminished values. (3) The flow of injected powder may be split up, if it is injected too fast. (4) In comparison with cylindrical nozzles, specially developed nozzles with a controlled expanding contour, lead to broader temperature profiles across the plasma jet and hence to better melting conditions for the particles.

Henne, R.H.; Borck, V. [DLR Inst. of Technical Thermodynamics, Stuttgart (Germany); Mayr, W. [Fachhochschule Muenchen, Munich (Germany); Landes, K.; Reusch, A. [Univ. of the German Armed Forces, Munich (Germany)

1995-12-31

293

Research on the activating flux gas tungsten arc welding and plasma arc welding for stainless steel  

Microsoft Academic Search

A systematic study of the effects of activating flux in the weld morphology, arc profile, and angular distortion and microstructure\\u000a of two different arc welding processes, namely, Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW), was carried\\u000a out. The results showed that the activating fluxes affected the penetration capability of arc welding on stainless steel.\\u000a An increase in

Her-Yueh Huang

2010-01-01

294

Improved gas chromatographic–mass spectrometric method for the quantitative determination of vinpocetine in human plasma  

Microsoft Academic Search

An improved and validated method for the determination of vinpocetine in human plasma using a combination of a solid-phase extraction as a cleaning step followed by gas chromatography–mass spectrometry (GC–MS) has been presented. Quantitation has been carried out with apovincaminic acid methyl ester as internal standard. A limit of detection of 0.01 ng\\/ml, limit of quantitation of 0.10 ng\\/ml, as

M Vatsova; S Tzvetanov; A Drenska; J Goranscheva; N Tyutyulkova

1997-01-01

295

Cold fusion experiments using Maxwellian plasmas and sub-atmospheric deuterium gas  

Microsoft Academic Search

Experiments are being performed to initiate the cold fusion process in Maxwellian plasmas and sub-atmospheric deuterium gas. Thus far, apparent neutron counts have been observed using a BF3 probe and Ludlum model 2200 digital counter, and a broad 8.1 MeV peak has been observed using a 3-inch sodium iodide crystal and a Nucleus PCA II multichannel analyzer. The results appear

Mark Prelas; Frederick Boody; Warren Gallaher; Edbertho Leal-Quiros; David Mencin; Scott Taylor

1990-01-01

296

Longitudinal gas-density profilometry for plasma-wakefield acceleration targets  

NASA Astrophysics Data System (ADS)

Precise tailoring of plasma-density profiles has been identified as one of the critical points in achieving stable and reproducible conditions in plasma wakefield accelerators. Here, the strict requirements of next generation plasma-wakefield concepts, such as hybrid-accelerators, with densities around 1017 cm-3 pose challenges to target fabrication as well as to their reliable diagnosis. To mitigate these issues we combine target simulation with fabrication and characterization. The resulting density profiles in capillaries with gas jet and multiple in- and outlets are simulated with the fluid code OpenFOAM. Satisfactory simulation results then are followed by fabrication of the desired target shapes with structures down to the 10 ?m level. The detection of Raman scattered photons using lenses with large collection solid angle allows to measure the corresponding longitudinal density profiles at different number densities and allows a detection sensitivity down to the low 1017 cm-3 density range at high spatial resolution. This offers the possibility to gain insight into steep density gradients as for example in gas jets and at the plasma-to-vacuum transition.

Schaper, Lucas; Goldberg, Lars; Kleinwächter, Tobias; Schwinkendorf, Jan-Patrick; Osterhoff, Jens

2014-03-01

297

Neutral gas plasma interactions and critical ionization velocity phenomena. Interim report  

SciTech Connect

The interplay of collisional and collisionless phenomena in the interaction of a magnetoplasma streaming through neutral gas produces some of the most fascinating plasma physics phenomena. A key notion controlling such interactions is the existence of a critical velocity (U sub c) effect postulated in an ad hoc fashion by Alfven, in his model of the formation of the solar system. According to Alfven's postulate, whenever the relative velocity between a neutral gas and a streaming magnetoplasma exceeds a value U sub c identical with Square root of (2Esub i/M), where E sub i is the ionization energy and M the mass of the neutral atoms, rapid ionization and anomalous momentum coupling occurs. Guided by recent laboratory and space experiments and plasma physics theory we present the basic plasma physics underlying the interaction. This is followed by a discussion of its relevance to the formation of the solar system and cometary tails, its controlling effect on plasma centrifuges and homopolar generators, and the fascinating possibility that critical velocity phenomena are controlling the space shuttle environment, transforming it into an artificial comet.

Papadopoulos, K.

1983-11-11

298

Hydro-gravitational fragmentation, diffusion and condensation of the primordial plasma, dark-matter and gas  

E-print Network

The first structures were proto-voids formed in the primordial plasma. Viscous and weak turbulence forces balanced gravitational forces when the scale of causal connection at time 30,000 years matched the viscous and turbulent Schwarz scales of hydro-gravitational theory (Gibson 1996). The photon viscosity allows only weak turbulence from the Reynolds number Re = 200, with fragmentation to give proto-supercluster voids, buoyancy forces, fossil vorticity turbulence, and strong sonic damping. The expanding, cooling, plasma continued fragmentation to proto-galaxy-mass with the density and rate-of-strain preserved as fossils of the weak turbulence and first structure. Turbulence fossilization by self-gravitational buoyancy explains the cosmic microwave background temperature fluctuations, not sonic oscillations in cold-dark-matter fragments. After plasma to gas transition at 300,000 years, gas fragmentation occurred within the proto-galaxies to form proto-globular-star-cluster (PGCs) clouds of small-planetary-mass primordial-fog-particles (PFPs). Dark PGC clumps of frozen PFPs persist as the inner-galaxy-halo dark matter, supporting Schild's 1996 quasar-microlensing interpretation. Non-baryonic dark matter diffused into the plasma proto-cluster-voids and later fragmented as outer-galaxy-halos at diffusive Schwarz scales, indicating light, weakly-collisional fluid particles (possibly neutrinos). Observations support the theory (Gibson and Schild 2003).

Carl H. Gibson

1999-11-15

299

Pulsed electromagnetic gas acceleration. [magnetohydrodynamics, plasma power sources and plasma propulsion  

NASA Technical Reports Server (NTRS)

Terminal voltage measurements with various cathodes and anodes in a high power, quasi-steady magnetoplasmadynamic (MPD) are discussed. The magnitude of the current at the onset of voltage fluctuations is shown to be an increasing function of cathode area and a weaker decreasing function of anode area. Tests with a fluted cathode indicated that the fluctuations originate in the plasma adjacent to the cathode rather than at the cathode surface. Measurements of radiative output from an optical cavity aligned to examine the current-carrying portion of a two-dimensional, 56 kA magnetoplasmadynamic discharge reveal no lasing in that region, consistent with calculations of electron excitation and resonance radiation trapping. A voltage-swept double probe technique allows single-shot determination of electron temperature and electron number density in the recombining MPD exhaust flow. Current distributions within the cavity of MPD hollow cathodes for various static prefills with no injected mass flow are examined.

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1975-01-01

300

Food irradiation and sterilization  

NASA Astrophysics Data System (ADS)

Radiation sterilization of food (radappertization) requires exposing food in sealed containers to ionizing radiation at absorbed doses high enough (25-70 kGy) to kill all organisms of food spoilage and public health significance. Radappertization is analogous to thermal canning is achieving shelf stability (long term storage without refrigeration). Except for dry products in which autolysis is negligible, the radappertization process also requires that the food be heated to an internal temperature of 70-80°C (bacon to 53°C) to inactivate autolytic enzymes which catalyze spoilage during storage without refrigeration. To minimize the occurence of irradiation induced off-flavors and odors, undesirable color changes, and textural and nutritional losses from exposure to the high doses required for radappertization, the foods are vacuum sealed and irradiated frozen (-40°C to -20°C). Radappertozed foods have the characteristic of fresh foods prepared for eating. Radappertization can substitute in whole or in part for some chemical food additives such as ethylene oxide and nitrites which are either toxic, carcinogenic, mutagenic, or teratogenic. After 27 years of testing for "wholesomeness" (safety for consumption) of radappertized foods, no confirmed evidence has been obtained of any adverse effecys of radappertization on the "wholesomeness" characteristics of these foods.

Josephson, Edward S.

301

Local demands on sterile neutrinos  

E-print Network

In a model independent manner, we explore the local implications of a single neutrino oscillation measurement which cannot be reconciled within a three-neutrino theory. We examine this inconsistency for a single region of baseline to neutrino energy $L/E$. Assuming that sterile neutrinos account for the anomaly, we find that the {\\it local} demands of this datum can require the addition to the theory of one to three sterile neutrinos. We examine the constraints which can be used to determine when more than one neutrino would be required. The results apply only to a given region of $L/E$. The question of the adequacy of the sterile neutrinos to satisfy a global analysis is not addressed here. Finally, using the results of a 3+2 analysis, we indicate values for unknown mixing matrix elements which would require two sterile neutrinos due to local demands only.

David C. Latimer; David J. Ernst

2005-09-23

302

Sterilization Using 365 nm UV-LED  

Microsoft Academic Search

There are several methods used for sterilization. In those methods chlorine, heat and UV rays are traditionally used. In recent years, the UV sterilization is taken notice as a sterilization method that the sterilized object does not change in quality and is environment-friendly. In this paper, an UV-LED is focused because it does not contain harmful substance and has longer

Noriyuki YAGI; Mirei MORI; Akiko HAMAMOTO; Masayuki NAKANO; Masatake AKUTAGAWA; Souko TACHIBANA; Akira TAKAHASHI; Toshitaka IKEHARA; Yohsuke KINOUCHI

2007-01-01

303

Optical and application study of gas-liquid discharge excited by bipolar nanosecond pulse in atmospheric air.  

PubMed

In this study, a bipolar nanosecond pulse with 20ns rising time is employed to generate air gas-liquid diffuse discharge plasma with room gas temperature in quartz tube at atmospheric pressure. The image of the discharge and optical emission spectra of active species in the plasma are recorded. The plasma gas temperature is determined to be approximately 390K by compared the experimental spectra with the simulated spectra, which is slightly higher than the room temperature. The result indicated that the gas temperature rises gradually with pulse peak voltage increasing, while decreases slightly with the electrode gap distance increasing. As an important application, bipolar nanosecond pulse discharge is used to sterilize the common microorganisms (Actinomycetes, Candida albicans and Escherichia coli) existing in drinking water, which performs high sterilization efficiency. PMID:24845733

Wang, Sen; Wang, Wen-chun; Yang, De-zheng; Liu, Zhi-jie; Zhang, Shuai

2014-10-15

304

Optical and application study of gas-liquid discharge excited by bipolar nanosecond pulse in atmospheric air  

NASA Astrophysics Data System (ADS)

In this study, a bipolar nanosecond pulse with 20 ns rising time is employed to generate air gas-liquid diffuse discharge plasma with room gas temperature in quartz tube at atmospheric pressure. The image of the discharge and optical emission spectra of active species in the plasma are recorded. The plasma gas temperature is determined to be approximately 390 K by compared the experimental spectra with the simulated spectra, which is slightly higher than the room temperature. The result indicated that the gas temperature rises gradually with pulse peak voltage increasing, while decreases slightly with the electrode gap distance increasing. As an important application, bipolar nanosecond pulse discharge is used to sterilize the common microorganisms (Actinomycetes, Candida albicans and Escherichia coli) existing in drinking water, which performs high sterilization efficiency.

Wang, Sen; Wang, Wen-chun; Yang, De-zheng; Liu, Zhi-jie; Zhang, Shuai

2014-10-01

305

A multistate model of fecundability and sterility.  

PubMed

This paper develops a multistate hazards model for estimating fecundability and sterility from data on waiting times to conception. Important features of the model include separate sterile and nonsterile states, a distinction between preexisting sterility and sterility that begins after initiation of exposure, and log-normally distributed fecundability among nonsterile couples. Application of the model to data on first birth intervals from Taiwan, Sri Lanka, and the Amish shows that heterogeneity in fecundability is statistically significant at most ages, but that preexisting sterility and new sterility are unimportant before age 40. These results suggest that sterility may not be an important determinant of natural fertility until later reproductive ages. PMID:7828764

Wood, J W; Holman, D J; Yashin, A I; Peterson, R J; Weinstein, M; Chang, M C

1994-08-01

306

Atmospheric-pressure plasma jets: Effect of gas flow, active species, and snake-like bullet propagation  

SciTech Connect

Cold atmospheric-pressure plasma jets have recently attracted enormous interest owing to numerous applications in plasma biology, health care, medicine, and nanotechnology. A dedicated study of the interaction between the upstream and downstream plasma plumes revealed that the active species (electrons, ions, excited OH, metastable Ar, and nitrogen-related species) generated by the upstream plasma plume enhance the propagation of the downstream plasma plume. At gas flows exceeding 2 l/min, the downstream plasma plume is longer than the upstream plasma plume. Detailed plasma diagnostics and discharge species analysis suggest that this effect is due to the electrons and ions that are generated by the upstream plasma and flow into the downstream plume. This in turn leads to the relatively higher electron density in the downstream plasma. Moreover, high-speed photography reveals a highly unusual behavior of the plasma bullets, which propagate in snake-like motions, very differently from the previous reports. This behavior is related to the hydrodynamic instability of the gas flow, which results in non-uniform distributions of long-lifetime active species in the discharge tube and of surface charges on the inner surface of the tube.

Wu, S.; Wang, Z.; Huang, Q.; Tan, X.; Lu, X. [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Ostrikov, K. [CSIRO Materials Science and Engineering, PO Box 218, Lindfield NSW 2070 (Australia); School of Physics, University of Sydney, Sydney NSW 2006 (Australia); State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China)

2013-02-15

307

Radiation from magnetized wakes in ultra-short high intensity laser pulse and gas jet plasma interaction  

Microsoft Academic Search

Using a gas jet flow, via the interaction between an ultra-short and high intensity laser pulse and plasma in the presence of a perpendicular external DC magnetic field, the short pulse radiation from magnetized plasma wakefields have been observed. The wakefields are excited by a mode locked Ti:sapphire laser beam. Different nozzles are used in order to generate different densities

D. Dorraman; M. Starodubtsev; H. Kawakami; H. P. Araghy; H. Ito; N. Yugami; Y. Nishida

2003-01-01

308

Characterization of fuel gas products from the treatment of solid waste streams with a plasma arc torch  

Microsoft Academic Search

This work addresses the plasma treatment of two solid waste streams and production of fuel gases from the process. In this study, carpet waste and simulated solid wastes generated by a United States Air Force Basic Expeditionary Airfield Resources Base deployment were used. Waste was treated in a furnace fitted with a 100kW plasma arc torch. The off gas was

Ambarish Vaidyanathan; James Mulholland; Jaeyong Ryu; Michael Stuart Smith; Louis J. Circeo

2007-01-01

309

A unified model of transport phenomena in gas metal arc welding including electrode, arc plasma and molten pool  

Microsoft Academic Search

This paper presents a theoretical model for describing globular transfer in gas metal arc welding. The heat and mass transfer in the electrode, arc plasma and molten pool are considered in one unified model. Using the volume of fluid method, the transport phenomena are dynamically studied in the following processes: droplet formation and detachment, droplet flight in arc plasma, impingement

H. G. Fan; R. Kovacevic

2004-01-01

310

Deuterium to helium plasma-wall change-over experiments in the JET MkII-gas box divertor  

Microsoft Academic Search

The deuterium and helium dynamics in the plasma and subdivertor regions of JET are compared during a sequence of similar ohmic and ICRH pulses where 100% He gas is injected into the JET vacuum vessel, whose graphite walls were previously saturated with deuterium. After the first six He fueled change-over discharges, only He plasma operation was performed. Following this investigation,

D. L. Hillis; T. Loarer; J. Bucalossi; A. Pospieszczyk; W. Fundamenski; G. Matthews; A. Meigs; P. Morgan; V. Phillips; R. Pitts; M. Stamp; M. von Hellermann

2003-01-01

311

Plasma properties of driver gas following interplanetary shocks observed by ISEE-3  

NASA Technical Reports Server (NTRS)

Plasma fluid parameters calculated from solar wind and magnetic field data to determine the characteristic properties of driver gas following a select subset of interplanetary shocks were studied. Of 54 shocks observed from August 1978 to February 1980, 9 contained a well defined driver gas that was clearly identifiable by a discontinuous decrease in the average proton temperature. While helium enhancements were present downstream of the shock in all 9 of these events, only about half of them contained simultaneous changes in the two quantities. Simultaneous with the drop in proton temperature the helium and electron temperature decreased abruptly. In some cases the proton temperature depression was accompanied by a moderate increase in magnetic field magnitude with an unusually low variance, by a small decrease in the variance of the bulk velocity, and by an increase in the ratio of parallel to perpendicular temperature. The cold driver gas usually displayed a bidirectional flow of suprathermal solar wind electrons at higher energies.

Zwickl, R. D.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.; Smith, E. J.

1983-01-01

312

Plasma properties of driver gas following interplanetary shocks observed by ISEE-3  

NASA Technical Reports Server (NTRS)

Plasma fluid parameters calculated from solar wind and magnetic field data obtained on ISEE 3 were studied. The characteristic properties of driver gas following interplanetary shocks was determined. Of 54 shocks observed from August 1978 to February 1980, nine contained a well defined driver gas that was clearly identifiable by a discontinuous decrease in the average proton temperature across a tangential discontinuity. While helium enhancements were present in all of nine of these events, only about half of them contained simultaneous changes in the two quantities. Often the He/H ratio changed over a period of minutes. Simultaneous with the drop in proton temperature the helium and electron temperature decreased abruptly. In some cases the proton temperature depression was accompanied by a moderate increase in magnetic field magnitude with an unusually low variance and by an increase in the ratio of parallel to perpendicular temperature. The drive gas usually displayed a bidirectional flow of suprathermal solar wind electrons at higher energies.

Zwickl, R. D.; Ashbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.; Smith, E. J.

1982-01-01

313

The Neutral Gas Desorption and Breakdown on a Metal-Dielectric Junction Immersed in a Plasma  

NASA Technical Reports Server (NTRS)

New results are presented of an experimental study and theoretical analysis of arcing on metal-dielectric junctions immersed in a low-density plasma. Two samples of conventional solar arrays have been used to investigate the effects of arcing within a wide range of neutral gas pressures, ion currents, and electron number densities. All data (except video) were obtained in digital form that allowed us to study the correlation between external parameters (plasma density, additional capacitance, bias voltage, etc) and arc characteristics (arc rate, arc current pulse width and amplitude, gas species partial pressures, intensities of spectral lines, and so on). Arc sites were determined by employing a video-camera, and it is shown that the most probable sites for arc inception are trip le-junctions, even though some arcs were initiated in gaps between cells. The effect of surface conditioning (decrease of arc rate due to outgassing) was clearly demonstrated. Moreover, a considerable increase in arc rate due to absorption of molecules from atmospheric air has been confirmed. The analysis of optical spectra (240-800 nm) reveals intense narrow atomic lines (Ag, H) and wide molecular bands (OH, CH, SiH, SiN) that confirm a complicated mechanism of arc plasma generation. The rate of plasma contamination due to arcing was measured by employing a mass-spectrometer. These measurements provided quite reliable data for the development of a theoretical model of plasma contamination, In conclusion, the arc threshold was increased to above 350 V (from 190 V) by keeping a sample in vacuum (20 micronTorr) for seven days. The results obtained are important for the understanding of the arc inception mechanism, which is absolutely essential for progress toward the design of high voltage solar arrays for space applications.

Vayner, Boris; Galofaro, Joel; Ferguson, Dale; Lyons, Valerie J. (Technical Monitor)

2002-01-01

314

Gas to particle conversion-gas exchange technique for direct analysis of metal carbonyl gas by inductively coupled plasma mass spectrometry.  

PubMed

A novel gas to particle conversion-gas exchange technique for the direct analysis of metal carbonyl gas by inductively coupled plasma mass spectrometry (ICPMS) was proposed and demonstrated in the present study. The technique is based on a transfer of gas into particle, which can be directly analyzed by ICPMS. Particles from metal carbonyl gases such as Cr(CO)6, Mo(CO)6, and W(CO)6 are formed by reaction with ozone (O3) and ammonium (NH3) gases within a newly developed gas to particle conversion device (GPD). The reaction mechanism of the gas to particle conversion is based on either oxidation of metal carbonyl gas by O3 or agglomeration of metal oxide with ammonium nitrate (NH4NO3) which is generated by the reaction of O3 and NH3. To separate the reaction gases (remaining O3 and NH3) from the formed particles, a previously reported gas exchange device (GED) was used and the in argon stabilized analyte particles were directly introduced and measured by ICPMS. This new technique provided limits of detection (LOD) of 0.15 pL L(-1) (0.32 ng m(-3)), 0.02 pL L(-1) (0.07 ng m(-3)), and 0.01 pL L(-1) (0.07 ng m(-3)) for Cr(CO)6, Mo(CO)6, and W(CO)6, respectively, which were 4-5 orders of magnitude lower than those conventional applied for detecting these gases, e.g., gas chromatography with electron captured detector (GC-ECD) as well as Fourier transform-infrared spectroscopy (FT-IR). The achieved LODs were also similar or slightly better than those for ICPMS coupled to GC. Since the gas to particle conversion technique can achieve the direct measurement of metal carbonyl gases as well as the removal of reaction and ambient gases from metal carbonyl gases, the technique is considered to be well suited to monitor gas quality in semiconductor industry, engine exhaust gases, and or waste incineration products. PMID:25247610

Nishiguchi, Kohei; Utani, Keisuke; Gunther, Detlef; Ohata, Masaki

2014-10-21

315

The interaction of energetic charged particles with gas and boundaries in the particle simulation of plasmas  

NASA Astrophysics Data System (ADS)

In many areas of plasma physics, the interaction of energetic particles with boundaries and background gas plays a key role in the dynamics. Examples include wakefield accelerators, high power microwave sources, and fusion devices. There are several key phenomena involved in these interactions such as collisions, radiation and photoemission. For this work, we adopt particle-in-cell plasma simulation codes by developing and adding models to existing 1D and 2D. This work comprises three parts: a relativistic collision model, a particle-fluid/particle-particle hybrid collision model, and radiation and photoemission generation by energetic particle interaction with solid surfaces. Previously, collision models were developed for the particle simulation of plasmas in the classical regime, however, the classical model breaks down as energies approach the relativistic regime. In this work, a relativistic Monte Carlo collision model is developed, adding relativistic collision dynamics and improved relativistic differential cross sections. With this model, we extend our simulation capabilities to predict and analyze the time-dependent performance of wakefield accelerators. In many practical collisional plasma models, such as in oxygen, nitrogen, or air, both target and projectile species in collisions may be particle species, reacting with many other particle and fluid species. A hybrid collision model is introduced to model the reactions between particle and fluid species as well as those between particle and particle species. A hybrid collision model enables particle-in-cell simulation of air or oxygen dielectric breakdown in high power microwave devices, as well as hydrocarbon collisions in the diverter sheath region in a tokamak magnetic fusion reactor. A computational model has been developed to describe xray generation for energetic particle impact with surfaces in the particle simulation of plasmas, and photoemission of electrons due to photon impact (e.g. xrays). Xray and photoemission may be one of the sources for generation of a first electron, leading to dielectric multipactor breakdown at the vacuum window in high power microwave devices. We are able to predict the energy and angular spectra of xrays generated by energetic impact of electrons on surfaces in high power microwave devices with the xray generation model. After building each model, we compared our simulation results with experiments and analytic solutions in order to verify our models and demonstrate the new modeling capabilities. The models developed in this work expand the regime of validity for particle simulation of collisional plasmas to higher energy, and enable study of interaction of energetic charged particles with surfaces, background gas, and reactive plasma constituents.

Lim, Chul-Hyun

316

Multielement model for the simulation of inductively coupled plasmas: Effects of helium addition to the central gas stream  

Microsoft Academic Search

A model for an atmospheric pressure inductively coupled plasma (ICP) is developed which allows rather easy extension to a variable number of species and ionisation degrees. This encompasses an easy calculation of transport parameters for mixtures, ionisation and heat capacity. The ICP is modeled in an axisymmetric geometry, taking into account the gas streaming into a flowing ambient gas. A

Helmut Lindner; Annemie Bogaerts

2011-01-01

317

Investigation of Variation Power and Additive Gas Effect on the $\\\\hbox{SF}_{6}$ Destruction Using Atmospheric Microwave Plasma Torch  

Microsoft Academic Search

An atmospheric microwave plasma torch for the de- composition of SF6 accompanying additive gases (O2, compressed air) was investigated experimentally in this paper. Applied mi- crowave power and additive gas species as effective parameters on destruction and removal efficiency (DRE) were considered. It was approved that compressed air is a more efficient additive gas for the removal of SF6 compared

Zahra Ahmadi; Mohammad Reza Khani; Saeed Kooshki; Fateme Mirzajani; Babak Shokri

2011-01-01

318

The limits of sterility assurance  

PubMed Central

Sterility means the absence of all viable microorganisms including viruses. At present, a sterility assurance level (SAL) of 10–6 is generally accepted for pharmacopoeial sterilization procedures, i.e., a probability of not more than one viable microorganism in an amount of one million sterilised items of the final product. By extrapolating the reduction rates following extreme artificial initial contamination, a theoretical overall performance of the procedure of at least 12 lg increments (overkill conditions) is demanded to verify an SAL of 10–6. By comparison, other recommendations for thermal sterilization procedures demand only evidence that the difference between the initial contamination and the number of test organisms at the end of the process amount to more than six orders of magnitude. However, a practical proof of the required level of sterility assurance of 10–6 is not possible. Moreover, the attainability of this condition is fundamentally dubious, at least in non-thermal procedures. Thus, the question is discussed whether the undifferentiated adherence to the concept of sterility assurance on the basis of a single SAL of 10–6 corresponds with the safety requirements in terms of patient or user safety, costs and energy efficiency. Therefore, in terms of practical considerations, a concept of tiered SALs is recommended, analogous to the comparable and well-established categorization into “High-level disinfection”, “Intermediate-level disinfection” and “Low-level disinfection”. The determination of such tiered SALs is geared both to the intended application of the sterilized goods, as well as to the characteristics of the products and the corresponding treatment options. In the case of aseptic preparation, filling and production procedures, a mean contamination probability of 10–3 is assumed. In automated processes, lower contamination rates can be realized. In the case of the production of re-usable medical devices, a reduction of at least 2 lg increments can be achieved through prior cleaning in validated cleaning and disinfecting devices. By chemical disinfection, a further reduction of ?5 lg increments is achieved. In the case of sterilized surgical instruments, an additional concern is that they lay opened in contaminated air for the duration of the operation, at least in conventionally ventilated operating theaters. Finally, the amount of pathogens necessary to cause an infection must be considered. By logical consideration of all aspects, it seems possible to partially reduce sterility assurance levels without any loss of safety. Proceeding from this, we would like to make the following suggestions for tiered SAL values, adjusted according to the respective sterilization task: SAL 10–6 for heat-resistant pharmaceutical preparations (parenterals), suggested term: “Pharmaceutical sterilization”, SAL 10–4 for heat-resistant medical devices, suggested term: “High-level sterilization”, SAL 10–3 for heat-sensitive re-usable medical devices, under the precondition of a validated cleaning efficacy of >4 lg increments, suggested term: “Low-level sterilization”. PMID:20204091

von Woedtke, Thomas; Kramer, Axel

2008-01-01

319

Development of injection gas heating system for introducing large droplets to inductively coupled plasma.  

PubMed

We developed an injection gas heating system for introducing large droplets, because we want to effectively to measure elements in a single cell. This system was applied to ICP-atomic emission spectrometry (ICP-AES), to evaluate it performance. To evaluate the effect of the emission intensity, the emission intensity of Ca(II) increased to a maximum of tenfold at 147°C and the peak was shifted upstream of the plasma. To investigate in detail the effect of an injection gas heating system, we studied different conditions of the injection gas temperature and droplet volume. When the injection gas temperature was 89°C, smaller droplets were easily ionized. At 147°C, the emission intensity ratio and the absolute amount of the sample including the droplet exhibited close agreement. These results show the advantages of the injection gas heating system for large droplet introduction, and the sufficient reduction in the solvent load. The solvent load could be reduced by heating to 147°C using the system. PMID:24334979

Kaburaki, Yuki; Nomura, Akito; Ishihara, Yukiko; Iwai, Takahiro; Miyahara, Hidekazu; Okino, Akitoshi

2013-01-01

320

Bacterial Sterilization Using Cavitating Jet  

NASA Astrophysics Data System (ADS)

In this paper, a new sterilization method using cavitating flow is presented. Water with bacteria was pressurized up to 105 MPa and flushed out through two very small nozzles 0.1-0.31 mm in diameter, where a cavitating jet was generated containing bubbles that collapsed downstream. First, the effects of jet velocity and cavitation number on the sterilization rate of Escherichia coli JCM1649T (E. coli) were examined. The sterilization rate increased with jet velocity. The rate was proportional to the 3rd power of the velocity. All the E. coli cells were killed by three successive treatments at V=355.7 m/s and cavitation number ?=0.154. The sterilization rate has a peak depending on cavitation number at the low-jet-velocity region of less than 300 m/s. An experiment was also performed to compare two types of bacteria, E. coli, as typical Gram-negative bacteria and Bacillus subtilis JCM1465T (B. subtilis), as typical Gram-positive bacteria. Additional tests were performed using Pseudomonas putida JCM13063T, Gram-negative bacteria and Bacillus halodurans JCTM9153, Gram-positive bacteria. The sterilization rate of the Gram-positive bacteria was much lower than that of the Gram-negative bacteria under the same experimental conditions. Gram-positive bacteria have a thicker peptidoglycan layer than Gram-negative bacteria. This may be the reason why B. subtilis is more resistant to the mechanical stress caused by cavitating flow.

Azuma, Yohei; Kato, Hiroharu; Usami, Ron; Fukushima, Tadamasa

321

Surface Decontamination of Simulated Chemical Warfare Agents Using a Nonequilibrium Plasma with Off-Gas Monitoring  

SciTech Connect

InnovaTek is developing a surface decontamination technology that utilizes active species generated in a nonequilibrium corona plasma. The plasma technology was tested against DMMP, a simulant for the chemical agent Sarin. GC-MS analysis showed that a greater than four log10 destruction of the DMMP on an aluminum surface was achieved in a 10 minute treatment. An ion-trap mass spectrometer was utilized to collect time-resolved data on the treatment off-gases. These data indicate that only non-toxic 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 will also sense when decontamination is complete

Moeller, Trevor M.; Alexander, M. Lizabeth; Engelhard, Mark H.; Gaspar, Dan J.; Luna, Maria L.; Irving, Patricia M.

2002-08-01

322

Instabilities in uranium plasma and the gas-core nuclear rocket engine  

NASA Technical Reports Server (NTRS)

The nonlinear evolution of unstable sound waves in a uranium plasma has been calculated using a multiple time-scale asymptotic expansion scheme. The fluid equations used include the fission power density, radiation diffusion, and the effects of the changing degree of ionization of the uranium atoms. The nonlinear growth of unstable waves is shown to be limited by mode coupling to shorter wavelength waves which are damped by radiation diffusion. This mechanism limits the wave pressure fluctuations to values of order delta P/P approximates 0.00001 in the plasma of a typical gas-core nuclear rocket engine. The instability is thus not expected to present a control problem for this engine.

Tidman, D. A.

1972-01-01

323

High energy photons from quark-gluon plasma versus hot badronic gas  

NASA Astrophysics Data System (ADS)

Photons in the energy range of about one-half to several GeV have been proposed as a signal of the formation of quark-gluon plasma in high energy collisions. To lowest order the thermal emission rate is infrared divergent for massless quarks, but we regulate this divergence using the resummation technique of Braaten and Pisarski. Photons can also be produced in the hadron phase. We find that the dominant contribution comes from the reactions ?? ? ?? and ?? ? ??; the decays ? ? ?? and ? ? ??? are also significant. Comparing the thermal emission rates at temperatures of order 150-200 MeV we conclude that the hadron gas shines just as brightly as quark-gluon plasma.

Kapusta, Joseph; Lichard, Peter; Seibert, David

1992-07-01

324

High-energy photons from quark-gluon plasma versus hot hadronic gas  

NASA Astrophysics Data System (ADS)

Photons in the energy range of about one-half to several GeV have been proposed as a signal of the formation of a quark-gluon plasma in high-energy collisions. To lowest order the thermal emission rate is infrared divergent for massless quarks, but we regulate this divergence using the resummation technique of Braaten and Pisarski. Photons can also be produced in the hadron phase. We find that the dominant contribution comes from the reactions ??-->?? and ??-->?? the decays ?-->?? and ?-->??? are also significant. Comparing the thermal emission rates at a temperature T=200 MeV we conclude that the hadron gas shines just as brightly as the quark-gluon plasma.

Kapusta, Joseph; Lichard, Peter; Seibert, David

1991-11-01

325

Thermal Phenomena in Gas Confinement Dielectric Tube of the VASIMR Helicon Plasma  

NASA Astrophysics Data System (ADS)

A quartz dielectric tube provides gas confinement in the helicon discharge of the VASIMR (Variable Specific Impulse Magnetoplasma Rocket) experiment. Despite highly aligned magnetic field lines to confine the plasma in the discharge, significant thermal heating of the dielectric tube occurs. We perform infrared camera imaging studies of heating of the tube with varying operational parameters of the experiment. Results show decreased heating of the tube as the plasma becomes more highly magnetized and less collisional. The data follows a trend that is well represented by a Bohm transport of ions perpendicular to the magnetic field lines suggesting that ion impact on the tube rather than radiation is the primary heating mechanism. Highly localized heating is also observed directly under the antenna in regions where the coils lie closest to the tube surface. This phenomenon is attributed to capacitive coupling effects that accelerate ions under the antenna coils, increasing the local energy flux to the tube surface.

Berisford, Dan; Bengtson, R.; Raja, L.; Squire, J.; Cassidy, L.; Chauncery, J.; McCaskill, G.

2007-11-01

326

Near-Resonant Rayleigh Scattering Method for Measurements of Alkali Atomic Density in Combustion Gas Plasmas  

NASA Astrophysics Data System (ADS)

This paper reports the development of a non-intrusive, space-resolved method for density measurements of alkali atoms in combustion gas plasmas. A sodium density of over 1014 cm-3 in an air-acetylene flame was measured using a near-resonant Rayleigh scattering (NRRS) method, in which the wavelength of the incident laser was detuned from the resonance line of the sodium atoms in order to avoid reabsorption of the scattered signal light. The results agree fairly well with those obtained by the spectral absorption method and the Na reference cell method. The results show that the NRRS method described here can also be used to measure atomic densities of the order of 1016 cm-3, typical values in an open-cycle MHD power-generation plasma.

Watanabe, Yukio; Ikegami, Tomoaki; Nishiyama, Toshio; Akazaki, Masanori

1984-07-01

327

Size-selected cluster beam source based on radio frequency magnetron plasma sputtering and gas condensation  

SciTech Connect

We report on a source for producing size-selected nanoclusters based on the combination of radio frequency magnetron plasma sputtering and gas condensation. The use of plasma sputtering to vaporize a target is applicable to a large range of materials; Ag, Au, Cu, and Si have been attempted to date. The source, combined with a time-of-flight mass filter, can produce clusters in the size range from 2 up to at least 70 000 atoms, depending on the target material, with a constant mass (M) resolution (M/{delta}M{approx}25) at an intensity that produces atomic monolayer coverage in as little as a few minutes. The source is also attached to an ultrahigh vacuum analysis chamber, which allows in situ surface chemical and structural analysis. Examples of cluster deposition experiments with the source are also presented.

Pratontep, S.; Carroll, S.J.; Xirouchaki, C.; Streun, M.; Palmer, R.E. [Nanoscale Physics Research Laboratory, School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

2005-04-01

328

21 CFR 522.82 - Aminopropazine fumarate sterile solution injection.  

Code of Federal Regulations, 2010 CFR

...false Aminopropazine fumarate sterile solution injection. 522.82 Section 522...82 Aminopropazine fumarate sterile solution injection. (a) Specifications...aminopropazine fumarate sterile aqueous solution, veterinary, contains...

2010-04-01

329

21 CFR 522.82 - Aminopropazine fumarate sterile solution injection.  

Code of Federal Regulations, 2011 CFR

...false Aminopropazine fumarate sterile solution injection. 522.82 Section 522...82 Aminopropazine fumarate sterile solution injection. (a) Specifications...aminopropazine fumarate sterile aqueous solution, veterinary, contains...

2011-04-01

330

Relativistic plasmas. [of electron gas with non-relativistic ions in astrophysics  

NASA Technical Reports Server (NTRS)

Recent work on the kinetic theory of a highly relativistic electron gas and the associated photon opacity is discussed. The relaxation time for thermalization by Moller scattering is compared with the characteristic times associated with various loss processes acting to perturb the distribution away from equilibrium. For an optically thin plasma, bremsstrahlung is found to dominate Moller scattering when the dimensionless electron temperature is greater than about 3.5. Results are presented for the opacity from Compton scattering, pair production in the fields of electrons and ions, inverse bremsstrahlung, and synchrotron self-absorption.

Gould, R. J.

1982-01-01

331

Cytoplasmic Sterility Factors in VICIA FABA L  

PubMed Central

Tissues of cytoplasmic male sterile, maintainer, restorer, and restored lines, and sterile plants which reverted to fertility in Vicia faba were examined in ultrathin sections. Cytoplasmic spherical bodies (CSB), ca. 70 nm in diameter, were observed in tissues of all sterile plants but not in tissues of maintainer, restorer or restored sterile plants. No CSB were observed in a reverted fertile branch of a tiller-sterile plant, nor in 5 of 6 reverted fertile plants. One reverted fertile plant contained CSB in ovules. It is proposed that the CSB are the sites of, or possibly, products of, sterility factors in Vicia faba. PMID:17248701

Edwardson, J. R.; Bond, D. A.; Christie, R. G.

1976-01-01

332

[Determination of formaldehyde concentration in a low-pressure sterilizer].  

PubMed

Two methods are described in determining the concentration of Formaldehyde in the sterilisation chamber of a regular commercial sterilizer. The measurement and flow of the concentration is ascertained during a routine sterilization procedure. With regard to the biological efficiency test of the examined apparatus the stability of the active Formaldehyde concentration is controlled. The difficulty in the determination of the Formaldehyde in such sterilizers is due to the fact that samples must be taken at a reduced pressure of 200 mbar. We have developed two different sampling methods. By employing the first continual collection method Formaldehyde gas is drawn out of the sterilization chamber with a high vacuum pump and conveyed with hydrogen into a nickel catalysator, whereby Methane is formed. The determination of Methane is carried out with a flame ionisation detector (F.I.D.). The results of the F.I.D. method are between 10.1-10.8 mg Formaldehyde per litre of gas. It is possible to detect a slight, even reduction in the Formaldehyde concentration throughout a period of 90 min. With the second discontinual method of determination vacuum tubes are employed which are furnished with external magnetic valves for control. By opening the magnetic valves briefly during the pre-vacuum therewith causing loss of pressure, Formaldehyde gas can be collected in the vacuum tubes throughout the sterilization procedure. The determination of the samples extracted by the discontinual method is carried out spectrophotometrically using the p-Rosanilin method after Miksch et al. The second method of determination shows values of 9.0-9.8 mg/l (Sx = 0.8 mg/l). These results lie somewhat lower than those of the F.I.D. determination. The flow of the concentration during 90 min. shows an average reduction of 7.4% and matches exactly the curve which was obtained by the F.I.D. method. By measuring the Formaldehyde concentrations which goods are subjected to in normal sterilization procedure it is possible to examine the efficacy of Formaldehyde sterilizers under regular conditions. Only by quotation of the Formaldehyde concentration present is it possible to reproduce details on sterilization times of treated articles. PMID:3113101

Steiner, C; Tottoli, M; Reber, H

1987-05-01

333

Fabrication and testing of gas filled targets for large scale plasma experiments on Nova  

SciTech Connect

An experimental campaign on the Nova laser was started in July 1993 to study one st of target conditions for the point design of the National Ignition Facility (NIF). The targets were specified to investigate the current NIF target conditions--a plasma of {approximately}3 keV electron temperature and an electron density of {approximately}1.0 E + 21 cm{sup {minus}3}. A gas cell target design was chosen to confine as gas of {approximately}0.01 cm{sup 3} in volume at {approximately} 1 atmosphere. This paper will describe the major steps and processes necessary in the fabrication, testing and delivery of these targets for shots on the Nova Laser at LLNL.

Stone, G.F.; Spragge, M.; Wallace, R.J. [Lawrence Livermore National Lab., CA (United States); Rivers, C.J. [Lawrence Livermore National Lab., CA (United States)]|[Schafer (W.J.) Associates, Inc., Livermore, CA (United States)

1995-03-06

334

Production of synthesis gas by conversion of methane in a steam-carbon dioxide plasma  

NASA Astrophysics Data System (ADS)

Experimental setup and results of methane conversion in a steam-carbon dioxide plasma are briefly described. Mass-flow rate of CH4 was varied from 2.5 to 3.7 g/s while mass-flow rates of H2O of ˜3 g/s and CO2 of ˜3 g/s were maintained constant. The energy consumption was 29-42 MJ per 1 kg of CH4. The H2/CO ratio in the produced synthesis gas was 2.2-2.4. The conversion rate of CH4 was 90.8-99.8%. The content of H2 and CO in the synthesis gas was ˜95%.

Rutberg, Ph. G.; Bratsev, A. N.; Kuznetsov, V. A.; Nakonechnyi, G. V.; Nikonov, A. V.; Popov, V. E.; Popov, S. D.; Serba, E. O.; Subbotin, D. I.; Surov, A. V.

2014-09-01

335

High pressure laser plasma studies. [energy pathways in He-Ar gas mixtures at low pressure  

NASA Technical Reports Server (NTRS)

The operation of a nuclear pumped laser, operating at a wavelength of 1.79 micron m on the 3d(1/2-4p(3/2) transition in argon with helium-3 as the majority gas is discussed. The energy pathways in He-Ar gas were investigated by observing the effects of varying partial pressures on the emissions of levels lying above the 4p level in argon during a pulsed afterglow. An attempt is made to determine the population mechanisms of the 3d level in pure argon by observing emission from the same transition in a high pressure plasma excited by a high energy electron beam. Both collisional radiative and dissociative recombination are discussed.

Wells, W. E.

1980-01-01

336

Detection of deuterium and hydrogen using laser-induced helium gas plasma at atmospheric pressure  

SciTech Connect

An experimental study on gas analysis by means of laser-induced breakdown spectroscopy was conducted using a Nd-yttrium aluminum garnet laser (1,064 nm, 120 mJ, 8 ns) and helium host gas at atmospheric pressure on a sample of mixed water (H{sub 2}O) and heavy water (D{sub 2}O) in vapor form. It was shown that completely resolved hydrogen (H{sub {alpha}}) and deuterium (D{sub {alpha}}) emission lines that are separated by only 0.179 nm could be obtained at a properly delayed detection time when the charged particles responsible for the strong Stark broadening effect in the plasma have mostly disappeared. It is argued that the helium metastable excited state plays an important role in the hydrogen excitation process.

Kurniawan, Koo Hendrik; Lie, Tjung Jie; Suliyanti, Maria Margaretha; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Pardede, Marincan; Idris, Nasrullah; Kobayashi, Takao; Kusumoto, Yoshihumi; Kagawa, Kiichiro; Tjia, May On [Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630 (Indonesia); Department of Fiber Amenity, Graduate School of Engineering, Fukui University, 9-1 Bunkyo 3-chome, Fukui 910 (Japan); Department of Chemistry and Bio-Science, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Department of Physics, Faculty of Education and Regional Studies, 9-1 Bunkyo 3-chome, Fukui 910 (Japan); Department of Physics, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, 10 Ganesha, Bandung 40132 (Indonesia)

2005-11-01

337

Plasma jets and plasma bullets  

Microsoft Academic Search

Plasma plumes, or plasma jets, belong to a large family of gas discharges whereby the discharge plasma is extended beyond the plasma generation region into the surrounding ambience, either by a field (e.g. electromagnetic, convective gas flow, or shock wave) or a gradient of a directionless physical quantity (e.g. particle density, pressure, or temperature). This physical extension of a plasma

M G Kong; B N Ganguly; R F Hicks

2012-01-01

338

Portable Ethylene Oxide Sterilization Chamber  

PubMed Central

A portable ethylene oxide sterilization chamber was designed, constructed, and tested for use in the sterilization of embolectomy catheters. The unit can accommodate catheters up to 40 inches (101.6 cm) in length and can be operated for less than 4 cents per cycle. A constant concentration of 500 mg of ethylene oxide per liter of space and holding periods of 4 and 6 hr at 43 and 22 C, respectively, were adequate when tested with B. subtilis spores. The estimated cost of construction was $165.00. If temperature control is unnecessary, the cost is approximately $80.00. Images PMID:4977644

Songer, J. R.; Mathis, R. G.

1969-01-01

339

Axial plasma density propagation of barrier discharge non-thermal plasma bullets in an atmospheric pressure argon gas stream  

NASA Astrophysics Data System (ADS)

The characteristics of volume-averaged plasma density on axial propagation for atmospheric argon (Ar) plasma bullets are experimentally investigated. The non-thermal plasma bullets are ejected through a glass tube into the surrounding ambient air. Taking into consideration the time and space profile of the plasma movement, the plasma propagation is measured using a Rogowski coil. The plasma density is evaluated from the propagation velocity and the current magnitude. The plasma density profiles are presented as functions of the applied voltage and the length of growth. The plasma density is in the order of 1016 m-3 and the propagation velocity is in the order of 105 m s-1. These values are similar to those of weakly ionized non-thermal plasma jets.

Ohyama, R.; Sakamoto, M.; Nagai, A.

2009-05-01

340

Laser Wakefield Structures and Electron Acceleration in Gas Jet and Capillary Discharge Plasmas  

NASA Astrophysics Data System (ADS)

Laser-driven plasma wakefield accelerators have the potential to become the next generation of particle accelerators because of the very high acceleration gradients. The beam quality from such accelerators depends critically on the details plasma wave spatial structures. In experiments at the University of Michigan it was possible in a single shot by frequency domain holography (FDH) to visualize individual plasma waves produced by the 40 TW, 30 fs Hercules laser focused to the intensity of 10^19 W/cm^2 onto a supersonic He gas jet [1]. These holographic ``snapshots'' capture the evolution of multiple wake periods, and resolve wavefront curvature seen previously only in simulations. High-energy quasi-monoenergetic electron beams for plasma density in the specific range 1.5x10^19<=ne<=3.5x10^19 cm-3 were generated [2]. The experiments show that the energy, charge, divergence and pointing stability of the beam can be controlled by changing ne, and that higher electron energies and more stable beams are produced for lower densities. An optimized quasi-monoenergetic beam of over 300 MeV and 10 mrad angular divergence is demonstrated at a plasma density of ne=1.5x10^19 cm-3. The resulted relativistic electron beams have been used to perform gamma-neutron activation of ^12C and ^63Cu and photo-fission of ^238U with a record high reaction yields of ˜5x10^5/Joule [3]. Experiments performed with ablative capillary discharge plasma demonstrate stable guiding for laser power up to 10 TW with the transmission of 50% and guided intensity of ˜10^17 W/cm^2. Study of the staged electron acceleration have been performed which uses ablated plasma in front of the capillary to inject electrons into the wakefield structures. [1] N. H. Matlis et. al., Nature Physics 2, 749 (2006). [2] A. Maksimchuk et. al., Journal de Physique IV 133, 1123 (2006). [3] S. A. Reed et. al., Appl. Phys. Lett. 89, 231107 (2006).

Maksimchuk, Anatoly

2007-11-01

341

Development of a plasma sprayed ceramic gas path seal for high pressure turbine applications  

NASA Technical Reports Server (NTRS)

The plasma sprayed graded layered yittria stabilized zirconia (ZrO2)/metal(CoCrAlY) seal system for gas turbine blade tip applications up to 1589 K (2400 F) seal temperatures was studied. Abradability, erosion, and thermal fatigue characteristics of the graded layered system were evaluated by rig tests. Satisfactory abradability and erosion resistance was demonstrated. Encouraging thermal fatigue tolerance was shown. Initial properties for the plasma sprayed materials in the graded, layered seal system was obtained, and thermal stress analyses were performed. Sprayed residual stresses were determined. Thermal stability of the sprayed layer materials was evaluated at estimated maximum operating temperatures in each layer. Anisotropic behavior in the layer thickness direction was demonstrated by all layers. Residual stresses and thermal stability effects were not included in the analyses. Analytical results correlated reasonably well with results of the thermal fatigue tests. Analytical application of the seal system to a typical gas turbine engine application predicted performance similar to rig specimen thermal fatigue performance. A model for predicting crack propagation in the sprayed ZrO2/CoCrAlY seal system was proposed, and recommendations for improving thermal fatigue resistance were made. Seal system layer thicknesses were analytically optimized to minimize thermal stresses in the abradability specimen during thermal fatigue testing. Rig tests on the optimized seal configuration demonstrated some improvement in thermal fatigue characteristics.

Shiembob, L. T.

1977-01-01

342

Diagnostics of nitrogen plasma by trace rare-gas-optical emission spectroscopy  

SciTech Connect

Trace rare-gas-optical emission spectroscopy is carried out to characterize the nitrogen plasma as a function of discharge parameters. The functional dependence of N{sub 2}(C {sup 3}{pi}{sub u}) and N{sub 2}{sup +}(B {sup 2}{sigma}{sub u}{sup +}) excited states is monitored by measuring the emission intensities of the bandheads of second positive and first negative systems. The excited-state population density of N atoms and N{sub 2} molecules, extracted from their optical emission, is related to the ground-state population density after normalizing the changes for excitation cross section and electron energy distribution function by optical actinometry. The electron temperature is determined from the plasma-induced optical emission of trace rare gas by the line-to-line method. The obtained data may help us to adjust the optimum discharge conditions for the production of active species, which are considered to be important for the desired treatment of the samples.

Qayyum, A.; Zeb, Shaista; Naveed, M.A.; Ghauri, S.A.; Zakaullah, M.; Waheed, A. [Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Pakistan Institute of Nuclear Science and Technology (PINSTECH), P.O. Box 2151, 44000 Islamabad (Pakistan)

2005-11-15

343

Rapid and sensitive determination of nalmefene in human plasma by gas chromatography-mass spectrometry.  

PubMed

A rapid gas chromatography-mass spectrometric method for the determination of nalmefene in human plasma is described. The procedure involves protein precipitation, extraction with ethanol-chloroform mixture and derivatization with pentafluropropionic anhydride. The deuterated analog of nalmefene, 6beta-naltrexol-d(7), was used as the internal standard. Quantitation was achieved on a HP-1 column (12 mx0.2 mm I.D.) with negative chemical ionization (NCI) using methane:ammonia (95:5) as the reagent gas. The standard curves were fitted using a quadratic equation with the curve encompassing a range of 0.5 to 200 ng/ml, and the intra- and inter-assay variations for three different nalmefene levels were less than 10% throughout. The limit of quantitation was found to be 0.5 ng/ml. The method described is highly specific and reproducible, and could also be applied for the determination of naltrexone and 6beta-naltrexol. Application of the method to actual human plasma samples is demonstrated. PMID:12031840

Xie, Shan; Suckow, Raymond F; Mason, Barbara J; Allen, David; Cooper, Thomas B

2002-06-25

344

Electrostatic plasma instabilities driven by neutral gas flows in the solar chromosphere  

NASA Astrophysics Data System (ADS)

We investigate electrostatic plasma instabilities of Farley-Buneman (FB) type driven by quasi-stationary neutral gas flows in the solar chromosphere. The role of these instabilities in the chromosphere is clarified. We find that the destabilizing ion thermal effect is highly reduced by the Coulomb collisions and can be ignored for the chromospheric FB-type instabilities. In contrast, the destabilizing electron thermal effect is important and causes a significant reduction of the neutral drag velocity triggering the instability. The resulting threshold velocity is found as function of chromospheric height. Our results indicate that the FB-type instabilities are still less efficient in the global chromospheric heating than the Joule dissipation of the currents driving these instabilities. This conclusion does not exclude the possibility that the FB-type instabilities develop in the places where the cross-field currents overcome the threshold value and contribute to the heating locally. Typical length-scales of plasma density fluctuations produced by these instabilities are determined by the wavelengths of unstable modes, which are in the range 10-102 cm in the lower chromosphere and 102-103 cm in the upper chromosphere. These results suggest that the decimetric radio waves undergoing scattering (scintillations) by these plasma irregularities can serve as a tool for remote probing of the solar chromosphere at different heights.

Gogoberidze, G.; Voitenko, Y.; Poedts, S.; De Keyser, J.

2014-03-01

345

Reactive species output of a plasma jet with a shielding gas device—combination of FTIR absorption spectroscopy and gas phase modelling  

NASA Astrophysics Data System (ADS)

In this work, a simple modelling approach combined with absorption spectroscopy of long living species generated by a cold atmospheric plasma jet yields insight into relevant gas phase chemistry. The reactive species output of the plasma jet is controlled using a shielding gas device. The shielding gas is varied using mixtures of oxygen and nitrogen at various humidity levels. Through the combination of Fourier transform infrared (FTIR) spectroscopy, computational fluid dynamics (CFD) simulations and zero dimensional kinetic modelling of the gas phase chemistry, insight into the underlying reaction mechanisms is gained. While the FTIR measurements yield absolute densities of ozone and nitrogen dioxide in the far field of the jet, the kinetic simulations give additional information on reaction pathways. The simulation is fitted to the experimentally obtained data, using the CFD simulations of the experimental setup to estimate the correct evaluation time for the kinetic simulation. It is shown that the ozone production of the plasma jet continuously rises with the oxygen content in the shielding gas, while it significantly drops as humidity is increased. The production of nitrogen dioxide reaches its maximum at about 30% oxygen content in the shielding gas. The underlying mechanisms are discussed based on the simulation results.

Schmidt-Bleker, A.; Winter, J.; Iseni, S.; Dünnbier, M.; Weltmann, K.-D.; Reuter, S.

2014-04-01

346

Transgenic technologies to induce sterility.  

PubMed

The last few years have witnessed a considerable expansion in the number of tools available to perform molecular and genetic studies on the genome of Anopheles mosquitoes, the vectors of human malaria. As a consequence, knowledge of aspects of the biology of mosquitoes, such as immunity, reproduction and behaviour, that are relevant to their ability to transmit disease is rapidly increasing, and could be translated into concrete benefits for malaria control strategies. Amongst the most important scientific advances, the development of transgenic technologies for Anopheles mosquitoes provides a crucial opportunity to improve current vector control measures or design novel ones. In particular, the use of genetic modification of the mosquito genome could provide for a more effective deployment of the sterile insect technique (SIT) against vector populations in the field. Currently, SIT relies on the release of radiation sterilized males, which compete with wild males for mating with wild females. The induction of sterility in males through the genetic manipulation of the mosquito genome, already achieved in a number of other insect species, could eliminate the need for radiation and increase the efficiency of SIT-based strategies. This paper provides an overview of the mechanisms already in use for inducing sterility by transgenesis in Drosophila and other insects, and speculates on possible ways to apply similar approaches to Anopheles mosquitoes. PMID:19917077

Catteruccia, Flaminia; Crisanti, Andrea; Wimmer, Ernst A

2009-01-01

347

Microwave powered sterile access port  

NASA Technical Reports Server (NTRS)

A device and method for elimination of contamination during transfer of materials either into or from bioreactors, food containers, or other microbially vulnerable systems. Using microwave power, thermal sterilizations of mating fixtures are achieved simply, reliably, and quickly by the volatilization of small quantities of water to produce superheated steam which contacts all exposed surfaces.

Sauer, Richard L. (Inventor); Atwater, James E. (Inventor); Dahl, Roger W. (Inventor); Garmon, Frank C. (Inventor); Lunsford, Teddie D. (Inventor); Michalek, William F. (Inventor); Wheeler, Jr., Richard R. (Inventor)

2000-01-01

348

Persistent effectivity of gas plasma-treated, long time-stored liquid on epithelial cell adhesion capacity and membrane morphology.  

PubMed

Research in plasma medicine includes a major interest in understanding gas plasma-cell interactions. The immediate application of gas plasma in vitro inhibits cell attachment, vitality and cell-cell contacts via the liquid. Interestingly, in our novel experiments described here we found that the liquid-mediated plasma effect is long-lasting after storage up to seven days; i. e. the liquid preserves the characteristics once induced by the argon plasma. Therefore, the complete Dulbecco's Modified Eagle cell culture medium was argon plasma-treated (atmospheric pressure, kINPen09) for 60 s, stored for several days (1, 4 and 7 d) at 37°C and added to a confluent mouse hepatocyte epithelial cell (mHepR1) monolayer. Impaired tight junction architecture as well as shortened microvilli on the cell membrane could be observed, which was accompanied by the loss of cell adhesion capacity. Online-monitoring of vital cells revealed a reduced cell respiration. Our first time-dependent analysis of plasma-treated medium revealed that temperature, hydrogen peroxide production, pH and oxygen content can be excluded as initiators of cell physiological and morphological changes. The here observed persisting biological effects in plasma-treated liquids could open new medical applications in dentistry and orthopaedics. PMID:25170906

Hoentsch, Maxi; Bussiahn, René; Rebl, Henrike; Bergemann, Claudia; Eggert, Martin; Frank, Marcus; von Woedtke, Thomas; Nebe, Barbara

2014-01-01

349

Persistent Effectivity of Gas Plasma-Treated, Long Time-Stored Liquid on Epithelial Cell Adhesion Capacity and Membrane Morphology  

PubMed Central

Research in plasma medicine includes a major interest in understanding gas plasma-cell interactions. The immediate application of gas plasma in vitro inhibits cell attachment, vitality and cell-cell contacts via the liquid. Interestingly, in our novel experiments described here we found that the liquid-mediated plasma effect is long-lasting after storage up to seven days; i. e. the liquid preserves the characteristics once induced by the argon plasma. Therefore, the complete Dulbecco's Modified Eagle cell culture medium was argon plasma-treated (atmospheric pressure, kINPen09) for 60 s, stored for several days (1, 4 and 7 d) at 37°C and added to a confluent mouse hepatocyte epithelial cell (mHepR1) monolayer. Impaired tight junction architecture as well as shortened microvilli on the cell membrane could be observed, which was accompanied by the loss of cell adhesion capacity. Online-monitoring of vital cells revealed a reduced cell respiration. Our first time-dependent analysis of plasma-treated medium revealed that temperature, hydrogen peroxide production, pH and oxygen content can be excluded as initiators of cell physiological and morphological changes. The here observed persisting biological effects in plasma-treated liquids could open new medical applications in dentistry and orthopaedics. PMID:25170906

Hoentsch, Maxi; Bussiahn, Rene; Rebl, Henrike; Bergemann, Claudia; Eggert, Martin; Frank, Marcus; von Woedtke, Thomas; Nebe, Barbara

2014-01-01

350

Adrenergic and glucocorticoid modulation of the sterile inflammatory response.  

PubMed

Exposure to an intense, acute stressor, in the absence of a pathogen, alters immune function. Exposure to a single bout of inescapable tail shock increases plasma and tissue concentrations of cytokines, chemokines, and the danger associated molecular pattern (DAMP) Hsp72. Although previous studies have demonstrated that adrenergic receptor (ADR) and glucocorticoid receptor (GCR)-mediated pathways alter pathogen or microbial associated molecular pattern (MAMP)-evoked levels of cytokines, chemokines, and Hsp72, far fewer studies have tested the role of these receptors across multiple inflammatory proteins or tissues to elucidate the differences in magnitude of stress-evoked sterile inflammatory responses. The goals of the current study were to (1) compare the sterile inflammatory response in the circulation, liver, spleen, and subcutaneous (SQ) adipose tissue by measuring cytokine, chemokine, and DAMP (Hsp72) responses; and (2) to test the role of alpha-1 (?1), beta-1 (?1), beta-2 (?2), and beta-3 (?3) ADRs, as well as GCRs in signaling the sterile inflammatory response. The data presented indicate plasma and SQ adipose are significantly more stress responsive than the liver and spleen. Further, administration of ADR and GCR-specific antagonists revealed both similarities and differences in the signaling mechanisms of the sterile inflammatory response in the tissues studied. Finally, given the selective increase in the chemokine monocyte chemotactic protein-1 (MCP-1) in SQ tissue, it may be that SQ adipose is an important site of leukocyte migration, possibly in preparation for infection as a consequence of wounding. The current study helps further our understanding of the tissue-specific differences of the stress-induced sterile inflammatory response. PMID:24321216

Cox, Stewart S; Speaker, Kristin J; Beninson, Lida A; Craig, Wendy C; Paton, Madeline M; Fleshner, Monika

2014-02-01

351

A Multistate model of fecundability and sterility  

Microsoft Academic Search

This paper develops a multistate hazards model for estimating fecundability and sterility from data on waiting times to conception.\\u000a Important features of the model include separate sterile and nonsterile states, a distinction between preexisting sterility\\u000a and sterility that begins after initiation of exposure, and log-normally distributed fecundability among nonsterile couples.\\u000a Application of the model to data on first birth intervals

James W. Wood; Darryl J. Holman; Anatoli I. Yashin; Raymond J. Peterson; Maxine Weinstein; Ming-Cheng Chang

1994-01-01

352

Study Of Sterilization Effect Of Dielectric Barrier Discharge On Eucaryotic Microorganisms  

Microsoft Academic Search

The work was focused on studying of the effect of the dielectric barrier discharge (DBD) operating at atmospheric pressure on bioindicator Aspergillus niger. Plasma was generated in nitrogen and argon. Paper and PET-foil were used as the carrying medium. The influence of various working conditions on the efficiency of plasma sterilization was studied. Some partial results are presented.

H. Vojkovská; J. Slámová; Z. Kozáková; F. Krcma

2010-01-01

353

Removal of gas-phase ammonia and hydrogen sulfide using photocatalysis, nonthermal plasma, and combined plasma and photocatalysis at pilot scale.  

PubMed

This study focuses on the removal of gas-phase ammonia (NH3) and hydrogen sulfide (H2S) in a continuous reactor. Photocatalysis and surface dielectric barrier discharge (SDBD) plasma are studied separately and combined. Though the removal of volatile organic compounds by coupling plasma and photocatalysis has been reported on a number of studies in laboratory scale, this is as far as we know the first time that it is used to remove inorganic malodorous pollutants. While each separate process is able to degrade ammonia and hydrogen sulfide, a synergetic effect appears when they are combined at a pilot scale, leading to removal capacity higher than the sum of each separate process. The removal capacity is higher when the gas circulates at a higher flow rate and when pollutant concentration is higher. The presence of water vapor in the gas is detrimental to the efficiency of the process. Operating conditions also influence the production of nitrogen oxides and ozone. PMID:24996941

Maxime, Guillerm; Aymen Amine, Assadi; Abdelkrim, Bouzaza; Dominique, Wolbert

2014-11-01

354

Investigations of Biofilm-Forming Bacterial Cells by Atomic Force Microscopy Prior to and Following Treatment from Gas Discharge Plasmas  

NASA Astrophysics Data System (ADS)

We present investigations of biofilm-forming bacteria before and after treatment from gas discharge plasmas. Gas discharge plasmas represent a way to inactivate bacteria under conditions where conventional disinfection methods are often ineffective. These conditions involve bacteria in biofilm communities, where cooperative interactions between cells make organisms less susceptible to standard killing methods. Rhizobium gallicum and Chromobacterium violaceum were imaged before and after plasma treatment using an atomic force microscope (AFM). In addition, cell wall elasticity was studied by measuring force distance curves as the AFM tip was pressed into the cell surface. Results for cell surface morphology and micromechanical properties for plasma treatments lasting from 5 to 60 minutes were obtained and will be presented.

Vandervoort, K. G.; Joaquin, J. C.; Kwan, C.; Bray, J. D.; Torrico, R.; Abramzon, N.; Brelles-Marino, G.

2007-03-01

355

Steam Sterilization Cycles for Lab Applications  

E-print Network

;Steam Sterilization STERILIZER CHAMBER The large transfer of heat and WRAPPED PACK Condensate The large STEAM Steam at very high temperature and pressure must come in contact with every surface or penetrateSteam Sterilization Cycles for Lab Applications Presented by Gary Butler STERIS Life Sciences

Farritor, Shane

356

Effect of non-thermal atmospheric pressure plasma jet on human breast cancer cells  

NASA Astrophysics Data System (ADS)

Nowadays, Non-thermal plasma enjoy a wide range of applications in biomedical fields such as Sterilization, Wound healing, Cancer treatment and etc. The aim of this paper is to study the effect of non-thermal atmospheric pressure plasma jet on breast cancer (MCF-7) cells. In this regard the effect of plasma on death of the cancer cells are explored experimentally. The plasma in this discharge is created by pulsed dc high voltage power supply with repetition rate of several tens of kilohertz which led to the inductively coupled plasma. The pure helium gas were used for formation of the plasma jet. MTT assay were used for quantification of death cells. The results showed that the cells death rate increase with plasma exposure time. This study confirm that plasma jet have significant effect on treatment of human breast cancer cells.

Mirpour, Shahriar; Nikkhah, Maryam; Pirouzmand, Somaye; Ghomi, Hamid Reza

2012-10-01

357

Determination of gas-temperature and velocity profiles in an argon thermal-plasma jet by laser-light scattering  

Microsoft Academic Search

Gas-temperature and velocity profiles at the exit plane of a thermal argon plasma torch have been determined directly from a high-resolution Doppler-shifted line-shape analysis of laser light scattered by the plasma. Peak temperature and velocity values observed were 13 350 K[plus minus]7% and 1100 m s[sup [minus]1][plus minus]3%. Velocities as low as 45 m s[sup [minus]1][plus minus]45% were measured in

S. C. Snyder; L. D. Reynolds; G. D. Lassahn; J. R. Fincke; C. B. Jr. Shaw; R. J. Kearney

1993-01-01

358

Sensitive and selective gas chromatographic methods for the quantitation of camphor, menthol and methyl salicylate from human plasma  

Microsoft Academic Search

Analytical methods using gas chromatography–flame ionization detection (GC–FID) for the quantitation of camphor and menthol and GC–MS for the quantitation of methyl salicylate have been developed for measurement of low concentrations from human plasma. Anethole serves as the internal standard for camphor and menthol and ethyl salicylate serves as the internal standard for methyl salicylate. Plasma samples undergo multiple, sequential

Jennifer S Valdez; Debra K Martin; Michael Mayersohn

1999-01-01

359

Structure and optical properties of tungsten oxide nanomaterials prepared by a modified plasma arc gas condensation technique  

Microsoft Academic Search

With the use of a modified plasma arc gas condensation technique and control of the processing parameters, namely, plasma\\u000a current and chamber pressure, we synthesized tungsten oxide nanomaterials with aspect ratios ranging from 1.1 (for equiaxed\\u000a particles with the length and width of 48 nm and 44 nm, respectively) to 12.7 (for rods with the length and width of 266 nm\\u000a and 21 nm,

Cherng-Yuh Su; Hsuan-Ching Lin; Tsung-Kun Yang; Chung-Kwei Lin

2010-01-01

360

The effects of UV irradiation and gas plasma treatment on living mammalian cells and bacteria: a comparative approach  

Microsoft Academic Search

Living mammalian cells and bacteria were exposed to irradiation from narrow-band UV lamps and treated with a nonthermal gas plasma (plasma needle). The model systems were: Chinese Hamster Ovary (CHO-K1) cells (fibroblasts) and Escherichia Coli bacteria. UV irradiation can lead to cell death (necrosis) in fibroblasts, but the doses that cause such damage are much higher than those needed to

Edward A. Sosnin; Eva Stoffels; Michael V. Erofeev; Ingrid E. Kieft; Sergey E. Kunts

2004-01-01

361

Developpement et utilisation de sources de plasma pour steriliser des instruments medicaux  

NASA Astrophysics Data System (ADS)

Advances in plasma sterilization of medical devices (MDs) are dependent upon both the development of plasma sources adapted to the processing of these MDs, and upon the understanding of the inactivation mechanisms of microorganisms. The main objectives of this thesis were, on the one hand, to develop plasma sources that are spatially uniform and that have a low gas temperature (< 50°C) and, on the other hand, the identification and optimization of biocidal agents (e.g. UV radiation) in their plasmas. In the course of this work, we have designed and developed three types of electromagnetic field applicators to sustain plasma. The first was a network of distributed antennas on the outside of the dielectric discharge-vessel, which possessed multiple high-frequency (HF) input ports fed by a waveguide-based power divider. This distributed source concept was soon abandoned in favour of two other plasma source designs, since the latter ones provided immediate advantages for biomedical sterilization, and also in terms of energy efficiency and frequency bandwidth (e.g. near-constant input impedance). These two plasma sources are based on planar transmission line designs where the plasma is part of the transmission line: the first allows one to sterilize the inner surfaces (lumen) of thermally sensitive dielectric tubes (e.g. cardiac catheters), while the other enables one to immerse three-dimensional objects within the plasma (e.g. forceps). Two types of microorganisms were used to test the performances to identify and to optimise the biocidal agents of the plasma sources that we have developed namely, sedimented bacterial spores from a suspension of Bacillus atrophaeus and vegetative Staphylococcus aureus bacteria embedded in a biofilm matrix. Inactivation of these microorganisms in our plasma sterilizers results through irradiation. This sterilization process is rapid (a few minutes), non-toxic (it does not require venting), and it affects thermally sensitive polymers relatively little (no erosion was detected). Keywords: high-frequency (HF) plasma sources, input impedance, planar transmission lines, sterilization, bacterial spores, biofilm, thermally sensitive medical devices (MDs).

Pollak, Jerome

362

Influence of gas puff location on the coupling of lower hybrid waves in JET ELMy H-mode plasmas  

SciTech Connect

Reliable coupling of the lower hybrid current drive (LHCD) to H-mode plasmas in JET is made feasible through a dedicated gas injection system, located at the outer wall and magnetically connected to the antenna (Pericoli Ridolfini et al 2004 Plasma Phys. Control. Fusion 46 349, Ekedahl et al 2005 Nucl. Fusion 45 351, Ekedahl et al 2009 Plasma Phys. Control. Fusion 51 044001). An experiment was carried out in JET in order to investigate whether a gas injection from the top of the torus, as is foreseen for the main gas injection in ITER, could also provide good coupling of the LH waves if magnetically connected to the antenna. The results show that a top gas injection was not efficient for providing a reliable LHCD power injection, in spite of being magnetically connected and in spite of using almost twice the amount of gas flow compared with the dedicated outer mid-plane gas puffing system. A dedicated gas injection system, set in the outer wall and magnetically connected to the LHCD antenna, is therefore recommended in order to provide the reliable coupling conditions for an LHCD antenna in ITER.

Ekedahl, A. [CEA, IRFM, France; Petrzilka, V. [Assoc. Euratom-IPP.CR, Czech Republic; Baranov, Y. [EURATOM / UKAEA, UK; Brix, M [UKAEA Fusion, Culham UK; Goniche, M. [CEA, IRFM, France; Jacquet, P. [EURATOM / UKAEA, Abingdon, UK; Kirov, K K [Association EURATOM-CCFE, Abingdon, UK; Klepper, C Christopher [ORNL; Mailloux, J. [EURATOM / UKAEA, UK; Mayoral, M.-L. [EURATOM / UKAEA, UK; Nave, M. F. F. [Association EURATOM/IST, Lisbon, Portugal; Ongena, J. [Laboratory for Plasma Physics-ERM/KMS (LPP-ERM/KMS), Brussels, Belgium

2012-01-01

363

Fast x-ray imaging of the National Spherical Tokamak Experiment plasma with a micropattern gas detector based on gas electron multiplier amplifier  

NASA Astrophysics Data System (ADS)

An innovative fast system for x-ray imaging has been developed at ENEA-Frascati, Italy, in collaboration with INFN-Pisa, Italy. It is based on a pinhole camera coupled to a micropattern gas detector (MPGD) having a gas electron multiplier (GEM) as amplifying stage. This detector (2.5 cm×2.5 cm active area) is equipped with a two dimensional readout printed circuit board with 144 pixels (12×12). It is able to get x-ray images of the plasma at very high framing rate (up to 100 kHz) in a selectable x-ray energy range, with different magnifications or views of the plasma. The system has been tested successfully on the Frascati Tokamak Upgrade (FTU) during Summer 2001, with a one-dimensional perpendicular view of the plasma. In collaboration with ENEA, the Johns Hopkins University (JHU) and Princeton Plasma Physics (PPPL), this system has been setup and calibrated in the x-ray energy range 3-8 keV and it has been installed, with a tangential view, on the NSTX experiment at PPPL. Time resolved, two-dimensional x-ray images of the NSTX plasma core will be presented, with different magnifications and different orientations of the optical axis of the x-ray pinhole camera. Fast acquisitions, performed up to 50 kHz of framing rate, allow the study of the plasma evolution and the 2D shaping during MHD activity.

Pacella, D.; Pizzicaroli, G.; Leigheb, M.; Bellazzini, R.; Brez, A.; Finkenthal, M.; Stutman, D.; Blagojevic, B.; Vero, R.; Kaita, R.; Roquemore, A. L.; Johnson, D.

2003-03-01

364

Time-dependent calculations of molten pool formation and thermal plasma with metal vapour in gas tungsten arc welding  

NASA Astrophysics Data System (ADS)

A gas tungsten arc (GTA) was modelled taking into account the contamination of the plasma by metal vapour from the molten anode. The whole region of GTA atmosphere including the tungsten cathode, the arc plasma and the anode was treated using a unified numerical model. A viscosity approximation was used to express the diffusion coefficient in terms of viscosity of the shielding gas and metal vapour. The transient two-dimensional distributions of temperature, velocity of plasma flow and iron vapour concentration were predicted, together with the molten pool as a function of time for a 150 A arc current at atmospheric pressure, both for helium and argon gases. It was shown that the thermal plasma in the GTA was influenced by iron vapour from the molten pool surface and that the concentration of iron vapour in the plasma was dependent on the temperature of the molten pool. GTA on high sulfur stainless steel was calculated to discuss the differences between a low sulfur and a high sulfur stainless steel anode. Helium was selected as the shielding gas because a helium GTA produces more metal vapour than an argon GTA. In the GTA on a high sulfur stainless steel anode, iron vapour and current path were constricted. Radiative emission density in the GTA on high sulfur stainless steel was also concentrated in the centre area of the arc plasma together with the iron vapour although the temperature distributions were almost the same as that in the case of a low sulfur stainless steel anode.

Tanaka, M.; Yamamoto, K.; Tashiro, S.; Nakata, K.; Yamamoto, E.; Yamazaki, K.; Suzuki, K.; Murphy, A. B.; Lowke, J. J.

2010-11-01

365

Evolution from Rydberg gas to ultracold plasma in a supersonic atomic beam of Xe  

NASA Astrophysics Data System (ADS)

A Rydberg gas of xenon, entrained in a supersonic atomic beam, evolves slowly to form an ultracold plasma. In the early stages of this evolution, when the free-electron density is low, Rydberg atoms undergo long-range \\ell -mixing collisions, yielding states of high orbital angular momentum. The development of high-\\ell states promotes dipole–dipole interactions that help to drive Penning ionization. The electron density increases until it reaches the threshold for avalanche. Ninety ?s after the production of a Rydberg gas with the initial state, {{n}_{0}}{{\\ell }_{0}}=42d, a 432 V cm?1 electrostatic pulse fails to separate charge in the excited volume, an effect which is ascribed to screening by free electrons. Photoexcitation cross sections, observed rates of \\ell -mixing, and a coupled-rate-equation model simulating the onset of the electron-impact avalanche point consistently to an initial Rydberg gas density of 5\\times {{10}^{8}}\\;c{{m}^{-3}}.

Hung, J.; Sadeghi, H.; Schulz-Weiling, M.; Grant, E. R.

2014-08-01

366

Magnetohydrodynamic simulations of massive gas injection into Alcator C-Mod and DIII-D plasmas  

SciTech Connect

Disruption mitigation experiments using massive gas injection (MGI) on Alcator C-Mod [Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] and DIII-D [Luxon and Davis, Fusion Technol. 8, 441 (1985)] have shown that magnetohydrodynamics (MHD) plays an important role. The three-dimensional MHD code NIMROD [Sovinec et al., J. Comput. Phys. 195, 355 (2004)] has been extended to include atomic physics taken from the KPRAD code to perform simulations of MGI. Considerable benchmarking of the code has been done against Alcator C-Mod for neon and helium gas jet experiments. The code successfully captures the qualitative sequence of events observed in MGI experiments up to the end of the thermal quench. Neon jet simulations also show quantitative agreement with the experimental thermal quench onset time. For helium gas jets, we show that a small percent boron density can significantly alter the results even in the presence of a helium jet with three orders of magnitude higher density. The thermal quench onset time is considerably overpredicted unless boron radiation is included. A DIII-D helium jet simulation shows a faster rise time for total radiated power than the experiment, but comparable amplitude. Similar to the important role of boron in C-Mod, carbon radiation is a significant factor in DIII-D helium jet simulations and experiments.

Izzo, V. A.; Hollmann, E. M. [University of California-San Diego, La Jolla, California 92093 (United States); Whyte, D. G.; Granetz, R. S. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Parks, P. B.; Lao, L. L.; Wesley, J. C. [General Atomics, P.O. Box 85608, San Diego, California 92186-56088 (United States)

2008-05-15

367

Plasma nitriding using high H2 content gas mixtures for a cavitation erosion resistant steel  

NASA Astrophysics Data System (ADS)

Plasma nitriding using high H2 content gas mixtures in CA-6NM martensitic stainless steel was studied in the present work. Nitriding was performed in H2 + N2 gas mixtures for 5, 10 and 20% N2, in volume, at 773 K (500 °C), during 2 h. Changes in the surface morphology and nitrided layer constitution were characterized by SEM, XRD, roughness analysis, and nanoindentation technique. Cavitation erosion behavior of the nitrided samples was also investigated by means of a 20 kHz ultrasonic vibrator. The study was emphasized for the three first cavitation stages (incubation, acceleration, and maximum erosion rate stage) of the cumulative erosion-time curve. Results indicate that the gas mixture nitrogen content strongly influences the phases' formation and its distribution on the nitrided layer. Better cavitation erosion resistance which was attributed to the finer and more homogeneous distribution of the nitrided layer phases was verified for samples treated at 5% N2. Otherwise, worse cavitation erosion behavior for samples nitrided at 20% N2 is supposed to be due to the formation of multiphase compound layer constituted by Fe4N + Fe2-3N + CrN, which can infer residual stress in treated surface.

Allenstein, A. N.; Lepienski, C. M.; Buschinelli, A. J. A.; Brunatto, S. F.

2013-07-01

368

Theoretical Study of Plasma Parameters Dependence on Gas Temperature in an Atmospheric Pressure Argon Microwave Discharge  

SciTech Connect

The gas temperature is an important parameter in many applications of atmospheric pressure microwave discharges (MW). That is why it is necessary to study the influence of that temperature on the plasma characteristics. Our investigation is based on a self-consistent model including the wave electrodynamics and gas-discharge kinetics. We adopt a blocks' energy structure of the argon excited atom. More specifically, we consider 7 different blocks of states, namely 4s, 4p, 3d, 5s, 5p, 4d, and 6s. Each block k is characterized by its effective energy uk (derived as an average energy of all levels in the block), as well as its effective g-factor and population. The argon dimmer, atomic and molecular ions are also taken into account in the model. We solve the Boltzmann equation in order to get the electron energy distribution function and the necessary rate constants of the elementary processes. The collisional-radiative part of the model is based on 87 processes. As a result we obtain the electron and ions' number densities, mean electron energy, mean power for sustaining an electron--ion pair in the discharge bulk, as well as the population of the excited blocks of states of the argon atom as functions of the gas temperature.

Pencheva, M.; Benova, E. [Department for Language Teaching and International Students, Sofia University, 27 Kosta Loulchev Street, BG-1111 Sofia (Bulgaria); Zhelyazkov, I. [Faculty of Physics, Sofia University, 5 James Bourchier Blvd, BG-1164 Sofia (Bulgaria)

2008-03-19

369

Ethylene Oxide Gaseous Sterilization  

PubMed Central

The relationships of reaction temperature and concentration of gaseous ethylene oxide to the time required for inactivation of air-dried Bacillus subtilis var. niger spores are more complex than previously reported. A plot of temperature vs. the logarithm of “thermochemical death time” (TCDT) resulted in a straight line between 18 and 57 C for systems of “high” ethylene oxide concentration. The TCDT values were independent of ethylene oxide concentrations above certain temperature-dependent limits. A given ethylene oxide concentration produced a TCDT curve identical in the upper temperature regions with that for higher concentrations. As the temperature was lowered beyond a critical point, this curve diverged from that for higher concentrations, as a straight line of lesser slope. Thus, a series of curves exists for a range of ethylene oxide concentrations. They are characterized by two segments, both logarithmic, intersecting at a critical temperature for each concentration. The intersecting point is at a temperature inversely related to the ethylene oxide gas concentration. The temperature quotient for the high temperature segments of all systems was 1.8. This value was characteristic for ethylene oxide concentrations of 440 and 880 mg/liter at temperatures above 40.6 and 33.4 C, respectively. Below these critical temperatures, the Q10 values for the respective systems were 3.2 and 2.3. PMID:13890659

Ernst, Robert R.; Shull, James J.

1962-01-01

370

Reduction of plasma electron density in a gas ionized by an electron beam - Use of a gaseous dielectric  

NASA Technical Reports Server (NTRS)

Propagation of an electron beam through a gas creates a secondary electron/ion plasma which can have subsequent deleterious effects on the propagation of the beam. In the case of pulsed electron beams with short micropulse durations, these effects can be greatly reduced through the use of a small doping fraction of an electron attachment gas. We present a model which allows the calculation of the reduction in unbound plasma electron density attainable with a gaseous dielectric dopant. Potential problems with a dopant, including increased ionization, increased scattering, altered refractive index, and dopant saturation and fragmentation, are discussed.

Reid, Max B.

1993-01-01

371

Measurements of the gas-kinetic pressure in plasma flows emerging from a micropinch discharge by means of laser interferometry  

NASA Astrophysics Data System (ADS)

A new method for measuring the gas-kinetic pressure in pulsed plasma flows is developed in which an acoustic line in the form of a thin rod built in the optical scheme of a laser interferometer is used as a detector. The time evolution of the gas-kinetic pressure in particle flows emerging from a micropinch discharge (a low-inductance vacuum spark) was studied. Due to the wide dynamic range of the method (˜105), it can be applied in various plasma devices with a wide range of parameters.

Kuznetsov, A. P.; Byalkovskii, O. A.; Gubskii, K. L.; Kozin, G. I.; Protsenko, E. D.; Dodulad, E. I.; Savjolov, A. S.

2014-04-01

372

Free radicals induced in aqueous solution by non-contact atmospheric-pressure cold plasma  

SciTech Connect

To understand plasma-induced chemical processing in liquids, we investigated the formation of free radicals in aqueous solution exposed to different types of non-contact atmospheric-pressure helium plasma using the spin-trapping technique. Both hydroxyl radical (OH{center_dot}) and superoxide anion radical (O{sub 2}{sup -}{center_dot}) adducts were observed when neutral oxygen gas was additionally supplied to the plasma. In particular, O{sub 2}{sup -}{center_dot} can be dominantly induced in the solution via oxygen flow into the afterglow gas of helium plasma. This type of plasma treatment can potentially be used in medical applications to control infectious diseases, because the O{sub 2}{sup -}{center_dot} is crucial for sterilization of liquids via atmospheric-pressure plasma.

Tani, Atsushi; Fukui, Satoshi [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Ono, Yusuke; Kitano, Katsuhisa [Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Ikawa, Satoshi [Technology Research Institute of Osaka Prefecture, Izumi, Osaka 594-1157 (Japan)

2012-06-18

373

Microwave Sterilization and Depyrogenation System  

NASA Technical Reports Server (NTRS)

A fully functional, microgravity-compatible microwave sterilization and depyrogenation system (MSDS) prototype was developed that is capable of producing medical-grade water (MGW) without expendable supplies, using NASA potable water that currently is available aboard the International Space Station (ISS) and will be available for Lunar and planetary missions in the future. The microwave- based, continuous MSDS efficiently couples microwaves to a single-phase, pressurized, flowing water stream that is rapidly heated above 150 C. Under these conditions, water is rapidly sterilized. Endotoxins, significant biological toxins that originate from the cell walls of gram-negative bacteria and which represent another defining MGW requirement, are also deactivated (i.e., depyrogenated) albeit more slowly, with such deactivation representing a more difficult challenge than sterilization. Several innovations culminated in the successful MSDS prototype design. The most significant is the antenna-directed microwave heating of a water stream flowing through a microwave sterilization chamber (MSC). Novel antenna designs were developed to increase microwave transmission efficiency. These improvements resulted in greater than 95-percent absorption of incident microwaves. In addition, incorporation of recuperative heat exchangers (RHxs) in the design reduced the microwave power required to heat a water stream flowing at 15 mL/min to 170 C to only 50 W. Further improvements in energy efficiency involved the employment of a second antenna to redirect reflected microwaves back into the MSC, eliminating the need for a water load and simplifying MSDS design. A quick connect (QC) is another innovation that can be sterilized and depyrogenated at temperature, and then cooled using a unique flow design, allowing collection of MGW at atmospheric pressure and 80 C. The final innovation was the use of in-line mixers incorporated in the flow path to disrupt laminar flow and increase contact time at a given flow rate. These technologies can be employed in small-scale systems for efficient production of MGW in the laboratory or in a range of larger systems that meet various industrial requirements. The microwave antennas can also be adapted to selectively sterilize vulnerable connections to ultra-pure water production facilities or biologically vulnerable systems where microorganisms may intrude.

Akse, James R.; Dahl, Roger W.; Wheeler, Richard R., Jr.

2009-01-01

374

Sixteen years of experience with sterilization monitoring.  

PubMed

Sterilization in the dental office should be monitored to ascertain proper sterilizer function. Biologic monitoring with calibrated preparations of bacterial spores is the preferred, as well as the only method that actually measures sterilization. A dental school-based sterilization monitoring service for dental practices was established in 1978 at the University of Detroit. This service has grown from 20 participating dental offices to more than 1,500. In 1993, 18,137 biologic monitoring tests were performed. The participants in the service primarily use autoclaves (70%) for heat sterilization, while unsaturated chemical-vapor sterilizers (20%) and dry-heat units (10%) are less common. This article describes the history of sterilization monitoring in dental practices from 1978 to the present through a dental school-based service. PMID:7758029

Molinari, J A; Gleason, M J; Merchant, V A

1994-12-01

375

Plasma discharge and time-dependence of its effect to bacteria.  

PubMed

Several types of plasma discharge have been proven to have a capacity for sterilization. Our goal is to introduce new nonthermal plasma pencil. We used it to sterilize different microbial populations with differing ages. We used a plasma discharge of the following characteristics: radio frequency barrier discharger at atmospheric pressure with a working frequency of 13.56 MHz, and the working gas used was argon. We performed 110 tests with the following microbial populations: Pseudomonas aeruginosa, Staphylococcus aureus, Proteus species, and Klebsiella pneumoniae. All populations were inoculated on the previous day and also on the day of our experiment. We made our evaluations the following day and also after 5 days, with all our microbial populations. Eradication of microbial populations is dependent on the plasma discharge exposure time in all cases. With regard to freshly inoculated microbes, we were able to sterilize agar with intensive exposure lasting for 10 s of colonies Pseudomonas, Proteus, and Klebsiella. The most resistant microbe seems to be S. aureus, which survives 5 s of coherent exposure in half of the cases. Using the lightest plasma discharge exposure, we achieved a maximum of 10(4)-10(5) CFU/mL (colony-forming unit - CFU). Regarding older microbial populations inoculated the day before the experiment, we can only decrease population growth to 10(5) CFU/mL approximately, but never completely sterilize. The plasma discharge with our characteristics could be used for the sterilization of the aforementioned superficially growing microbes, but does not sufficiently affect deeper layers and thus seems to be a limitation for eradication of the already erupted colonies. PMID:24464536

Justan, I; Cernohorska, L; Dvorak, Z; Slavicek, P

2014-07-01

376

Laser Generated Plasmas in Nitrogen Gas and from Aluminum Containing Targets.  

NASA Astrophysics Data System (ADS)

The work in this thesis centers on the spectroscopy of multiply charged atomic nitrogen ions, the first negative system of N_2^+ (both from pure N_2 gas) and of aluminum and the green system of aluminum oxide (from some aluminum containing solid targets). All results are obtained from experiments using the method of laser-induced-breakdown -spectroscopy (LIBS). Extremely high lying states atomic and molecular nitrogen ions have been observed in the transient plasma that results from focusing a Q-switched Nd:YAG laser into a pure nitrogen atmosphere ranging in pressure from 100 to 800 Torr. During the first 10 to 80 ns after plasma ignition several states of N^{4+} can be detected. Their Stark broadened line width is strongly time dependent due to the rapidly changing electron density in the decaying plasma. At delay times 20 to 40 mus after plasma ignition, rotationally resolved emission from the first negative system of rm N_2^+, B ^2Sigma_{u}^+ - rm X^2Sigma_{g }^+ indicates a rotational and vibrational temperature of about 9500 K +/- 500 K. The electronic temperature is found at a slightly higher value of 13,000 K +/- 1000 K. The rotational temperature decreases approximately to 5500 K at a delay of 80 mus. Laser-induced-fluorescence has been used to probe the rm X^2Sigma_{g }^+ ground state of the N_2 ^+ molecule. From the Doppler profile of the R(18) line a preliminary value of the translational temperature of about 2300K was obtained. Rotationally resolved emission spectra of the rm B^2Sigma_{u} ^+ - X^2Sigma_{g}^+ have been observed in nitrogen plasmas. Extremely high lying rotational levels up to N^' = 141 in the P branch of the (0,0) band have been identified. In this band, new perturbations due to the v = 12, 13, 14 and 15 vibrational levels of the A ^2Pi_{rm u} state as well as spin-rotation splitting of the high N -levels are reported. Despite the limited resolution, information about the third order distortion constants can also be obtained. Among the solid targets, aluminum was chosen for further detailed studies. Many previously unobserved, very strong vibrational bands of the rm B ^Sigma^+ - rm X^2Sigma^+ transition are reported here for the first time. A vibrational temperature of ~2300K has been obtained for the B states at delay time of 96 mus after breakdown. Only atomic aluminum lines and no molecular emission was observed when aluminum containing ceramic samples were used.

Alam, Rejina C.

377

Contraceptive practice before female sterilization.  

PubMed

The reproductive profile and contraceptive practice of 402 women undergoing female sterilization at the Central Women's Hospital are presented. Most (89%) of the interviewees were urban-dwellers and housewives with primary school education. Fifty-two percent were between 30 and 34 years with a mean of 4.2 living children. Sixty-nine percent were past contraceptive users, of them; 29.9% had used more than one method. A considerable gap between knowledge and practice of different methods was found. Education level and employment had a significant effect on contraceptive practice (p < 0.01 and p < 0.5). The majority knew and used combined oral contraceptive pills and injectable progestogens, whereas rhythm, withdrawal and barrier contraception were lesser known methods. Contraceptive use was primarily for child-spacing whereas the main reasons for female sterilization were socioeconomic and achievement of desired family size. PMID:8250756

Thike, K B; Wai, K T; Oo, N; Yi, K H

1993-09-01

378

Electrostatic plasma instabilities driven by neutral gas flows in the solar chromosphere  

E-print Network

We investigate electrostatic plasma instabilities of Farley-Buneman (FB) type driven by quasi-stationary neutral gas flows in the solar chromosphere. The role of these instabilities in the chromosphere is clarified. We find that the destabilizing ion thermal effect is highly reduced by the Coulomb collisions and can be ignored for the chromospheric FB-type instabilities. On the contrary, the destabilizing electron thermal effect is important and causes a significant reduction of the neutral drag velocity triggering the instability. The resulting threshold velocity is found as function of chromospheric height. Our results indicate that the FB type instabilities are still less efficient in the global chromospheric heating than the Joule dissipation of the currents driving these instabilities. This conclusion does not exclude the possibility that the FB type instabilities develop in the places where the cross-field currents overcome the threshold value and contribute to the heating locally. Typical length-scales...

Gogoberidze, G; Poedts, S; De Keyser, J

2013-01-01

379

Gas-to-Particle Conversion in Surface Discharge Nonthermal Plasmas and Its Implications for Atmospheric Chemistry  

PubMed Central

This paper presents some experimental data on gas-to-particle conversion of benzene using nonthermal plasma (NTP) technology and discusses the possibility of its technical application in atmospheric chemistry. Aerosol measurement using a differential mobility analyzer (DMA) revealed that the parts of benzene molecules were converted into a nanometer-sized aerosol. Aerosol formation was found to be highly related with the missing part in carbon balance. Scanning electron microscopy analysis showed that the aerosols formed in synthetic humid air are the collection of nanoparticles. The carbonyl band (C=O) was found to be an important chemical constituent in the aerosol. The potential of the NTP as an accelerated test tool in studying secondary organic aerosol (SOA) formation from VOCs will be also addressed. PMID:22163781

Kim, Hyun-Ha; Ogata, Atsushi

2011-01-01

380

Magnetic Ignition of Pulsed Gas Discharges in Air of Low Pressure in a Coaxial Plasma Gun  

NASA Technical Reports Server (NTRS)

The effect of an axial magnetic field on the breakdown voltage of a coaxial system of electrodes has been investigated by earlier workers. For low values of gas pressure times electrode spacing, the breakdown voltage is decreased by the application of the magnetic field. The electron cyclotron radius now assumes the role held by the mean free path in nonmagnetic discharges and the breakdown voltage becomes a function of the magnetic flux density. In this paper the dependence of the formative time lag as a function of the magnetic flux density is established and the feasibility of using a magnetic field for igniting high-voltage, high-current discharges is shown through theory and experiment. With a 36 microfarad capacitor bank charged to 48,000 volts, a peak current of 1.3 x 10( exp 6) amperes in a coaxial type of plasma gun was achieved with a current rise time of only 2 microseconds.

Thom, Karlheinz; Norwood, Joseph, Jr.

1961-01-01

381

Ionized Plasma and Neutral Gas Coupling in the Sun's Chromosphere and Earth's Ionosphere/Thermosphere  

NASA Astrophysics Data System (ADS)

We review physical processes of ionized plasma and neutral gas coupling in the weakly ionized, stratified, electromagnetically-permeated regions of the Sun's chromosphere and Earth's ionosphere/thermosphere. Using representative models for each environment we derive fundamental descriptions of the coupling of the constituent parts to each other and to the electric and magnetic fields, and we examine the variation in magnetization of the components. Using these descriptions we compare related phenomena in the two environments, and discuss electric currents, energy transfer and dissipation. We present examples of physical processes that occur in both atmospheres, the descriptions of which have previously been conducted in contrasting paradigms, that serve as examples of how the chromospheric and ionospheric communities can further collaborate. We also suggest future collaborative studies that will help improve our understanding of these two different atmospheres, which while sharing many similarities, also exhibit large disparities in key quantities.

Leake, J. E.; DeVore, C. R.; Thayer, J. P.; Burns, A. G.; Crowley, G.; Gilbert, H. R.; Huba, J. D.; Krall, J.; Linton, M. G.; Lukin, V. S.; Wang, W.

2014-11-01

382

Method of sterilization using ozone  

NASA Technical Reports Server (NTRS)

Methods of using ozone have been developed which sterilize instruments and medical wastes, oxidize, organics found in wastewater, clean laundry, break down contaminants in soil into a form more readily digested by microbes, kill microorganisms present in food products, and destroy toxins present in food products. The preferred methods for killing microorganism and destroying toxins use pressurized, humidified, and concentrated ozone produced by an electrochemical cell.

Murphy, Oliver J. (Inventor); Hitchens, G. Duncan (Inventor)

2002-01-01

383

Plasma Sprayed Pour Tubes and Other Melt Handling Components for Use in Gas Atomization  

SciTech Connect

Ames Laboratory has successfully used plasma sprayed ceramic components made from yttria stabilized zirconia as melt pouring tubes for gas atomization for many years. These tubes have proven to be strong, thermal shock resistant and versatile. Various configurations are possible both internally and externally. Accurate dimensions are achieved internally with a machined fugitive graphite mandrel and externally by diamond grinding. The previous study of the effect of spray parameters on density was extended to determine the effect of the resulting density on the thermal shock characteristics on down-quenching and up-quenching. Encouraging results also prompted investigation of the use of plasma spraying as a method to construct a melt pour exit stopper that is mechanically robust, thermal shock resistant, and not susceptible to attack by reactive melt additions. The Ames Laboratory operates two close-coupled high pressure gas atomizers. These two atomizers are designed to produce fine and coarse spherical metal powders (5{mu} to 500{mu} diameter) of many different metals and alloys. The systems vary in size, but generally the smaller atomizer can produce up to 5 kg of powder whereas the larger can produce up to 25 kg depending on the charge form and density. In order to make powders of such varying compositions, it is necessary to have melt systems capable of heating and containing the liquid charge to the desired superheat temperature prior to pouring through the atomization nozzle. For some metals and alloys this is not a problem; however for some more reactive and/or high melting materials this can pose unique challenges. Figure 1 is a schematic that illustrates the atomization system and its components.

Byrd, David; Rieken, Joel; Heidloff, Andy; Besser, Matthew; Anderson, Iver

2011-04-01

384

Reaction chemistry and optimization of plasma remediation of NxOy from gas streams  

NASA Astrophysics Data System (ADS)

Increasing environmental awareness and regulatory pressure have motivated investigations into energy efficient methods to remove oxides of nitrogen (NxOy) from gas streams resulting from the combustion of fossil fuels. Plasma remediation of NxOy is potentially an efficient removal technique due to the relative ease of generating reactants by electron-impact processes. Previous works have investigated the use of electron-beam, corona, and dielectric barrier discharge (DBD) generated plasmas for this purpose. In those works, reduction (N+NO?N2+O) and oxidation (NO2+OH?HNO3) reactions were identified as major removal channels. A computational study of the plasma remediation of NxOy from humid air using repetitively pulsed DBDs is reported. The dominant reaction pathways are discussed and scaling laws are proposed to optimize the energy efficiency of removal. Three reaction periods are identified: the current pulse (during which electron-impact processes generate radicals), the postpulse remediative period (during which NxOy is removed), and the interpulse period (during which the densities of various nitrogen oxides are reapportioned with little net removal). The lifetimes of reactants (OH and O3 in particular) determine the length of these periods and hence the optimum repetition frequency. Optimum repetition rates are typically less than hundreds of Hz. It is also found that a larger number of current pulses producing less energy deposition per pulse results in a higher removal efficiency due to reduced competition from radical-radical reactions which deplete the reactants. The production of unwanted species (e.g., O3 and N2O) can be minimized by reducing or terminating power deposition when the densities NO and NO2 have been reduced to ppm levels. The energy efficiency of remediation generally increases with increasing water content by removing NOx through the oxidation channel, although at the price of producing an acidic end product.

Gentile, Ann C.; Kushner, Mark J.

1995-08-01

385

Adhesive forces and surface properties of cold gas plasma treated UHMWPE  

PubMed Central

Cold atmospheric plasma (CAP) treatment was used on ultra-high molecular weight polyethylene (UHMWPE), a common articulating counter material employed in hip and knee replacements. UHMWPE is a biocompatible polymer with low friction coefficient, yet does not have robust wear characteristics. CAP effectively cross-links the polymer chains of the UHMWPE improving wear performance (Perni et al., Acta Biomater. 8(3) (2012) 1357). In this work, interactions between CAP treated UHMWPE and spherical borosilicate sphere (representing model material for bone) were considered employing AFM technique. Adhesive forces increased, in the presence of PBS, after treatment with helium and helium/oxygen cold gas plasmas. Furthermore, a more hydrophilic surface of UHMWPE was observed after both treatments, determined through a reduction of up to a third in the contact angles of water. On the other hand, the asperity density also decreased by half, yet the asperity height had a three-fold decrease. This work shows that CAP treatment can be a very effective technique at enhancing the adhesion between bone and UHMWPE implant material as aided by the increased adhesion forces. Moreover, the hydrophilicity of the CAP treated UHMWPE can lead to proteins and cells adhesion to the surface of the implant stimulating osseointegration process.

Preedy, Emily Callard; Brousseau, Emmanuel; Evans, Sam L.; Perni, Stefano; Prokopovich, Polina

2014-01-01

386

Development of a plasma sprayed ceramic gas path seal for high pressure turbine application  

NASA Technical Reports Server (NTRS)

Development of the plasma sprayed graded, layered ZRO2/CoCrAlY seal system for gas turbine engine blade tip seal applications up to 1589 K (2400 F) surface temperature was continued. The effect of changing ZRO2/CoCrAlY ratios in the intermediate layers on thermal stresses was evaluated analytically with the goal of identifying the materials combinations which would minimize thermal stresses in the seal system. Three methods of inducing compressive residual stresses in the sprayed seal materials to offset tensile thermal stresses were analyzed. The most promising method, thermal prestraining, was selected based upon potential, feasibility and complexity considerations. The plasma spray equipment was modified to heat, control and monitor the substrate temperature during spraying. Specimens were fabricated and experimentally evaluated to: (1) substantiate the capability of the thermal prestrain method to develop compressive residual stresses in the sprayed structure and (2) define the effect of spraying on a heated substate on abradability, erosion and thermal shock characteristics of the seal system. Thermal stress analysis, including residual stresses and material properties variations, was performed and correlated with thermal shock test results. Seal system performance was assessed and recommendations for further development were made.

Shiembob, L. T.

1978-01-01

387

Fabrication of gas turbine water-cooled composite nozzle and bucket hardware employing plasma spray process  

DOEpatents

In the method for fabrication of water-cooled composite nozzle and bucket hardware for high temperature gas turbines, a high thermal conductivity copper alloy is applied, employing a high velocity/low pressure (HV/LP) plasma arc spraying process, to an assembly comprising a structural framework of copper alloy or a nickel-based super alloy, or combination of the two, and overlying cooling tubes. The copper alloy is plamsa sprayed to a coating thickness sufficient to completely cover the cooling tubes, and to allow for machining back of the copper alloy to create a smooth surface having a thickness of from 0.010 inch (0.254 mm) to 0.150 inch (3.18 mm) or more. The layer of copper applied by the plasma spraying has no continuous porosity, and advantageously may readily be employed to sustain a pressure differential during hot isostatic pressing (HIP) bonding of the overall structure to enhance bonding by solid state diffusion between the component parts of the structure.

Schilke, Peter W. (4 Hempshire Ct., Scotia, NY 12302); Muth, Myron C. (R.D. #3, Western Ave., Amsterdam, NY 12010); Schilling, William F. (301 Garnsey Rd., Rexford, NY 12148); Rairden, III, John R. (6 Coronet Ct., Schenectady, NY 12309)

1983-01-01

388

Interferometric investigation of the influence of argon buffer gas on the characteristics of laser-induced aluminum plasmas.  

PubMed

An interferometric analysis was performed to investigate the influence of argon (Ar) buffer gas on the characteristics of laser-induced aluminum (Al) plasma at atmospheric pressure. The plasma was produced by focusing a Q-switched Nd:YAG laser pulse (?=1064??nm, pulse duration ?5??ns, E=6.0??mJ) onto an Al target. The interference patterns were constructed using a Nomarski interferometer incorporated with a frequency-doubled, Q-switched Nd:YAG laser (?=532??nm, pulse duration ?10??ns) that generates an interferometric probe beam. The interferometric measurements were carried out as a function of the elapsed time after the onset of breakdown under the conditions of open air and an Ar gas jet flow (5??l/min). With the injection of an Ar buffer gas jet in the ablation process, an increase in electron density and a preferential axial plasma expansion of the plasma plume were observed during the early stages of plasma formation as a consequence of increased inverse-Bremsstrahlung (IB) absorption efficiency. PMID:24921120

Oh, Seong Y; Singh, Jagdish P; Lim, Changhwan

2014-06-10

389

Development of a Multiscale Ionized Gas (MIG) Flow Code for Plasma Applications Subrata Roy Datta V. Gaitonde  

E-print Network

of Scientific Research, Department of Defense, and DARPA for flow control and stability about an air vehicleDevelopment of a Multiscale Ionized Gas (MIG) Flow Code for Plasma Applications Subrata Roy Datta V Engineering Aeronautical Sciences Division Kettering University Air Vehicles Directorate Flint, Michigan 48504

Roy, Subrata

390

An Air Plasma Off-Gas Emission Monitor (APO-GEM) For On-line Toxic Metal Monitoring  

Microsoft Academic Search

Increasing regulatory demands requiring significant reductions in the emission of hazardous air pollutants have led to the need for techniques capable of providing real-time monitoring of toxic metals in combustion gas streams. These waste streams range from coal-fired boilers, municipal waste combustors to plasma vitrification systems used for the remediation of low level radioactive waste. Our solution to this problem

G. P. Miller; Z. Zhu; D. P. Baldwin

1998-01-01

391

Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet  

PubMed Central

The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment. PMID:25319447

Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

2014-01-01

392

Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet  

NASA Astrophysics Data System (ADS)

The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment.

Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T. H.; Kang, Tae-Hong

2014-10-01

393

Effect of additive oxygen gas on cellular response of lung cancer cells induced by atmospheric pressure helium plasma jet.  

PubMed

The atmospheric pressure helium plasma jet driven by pulsed dc voltage was utilized to treat human lung cancer cells in vitro. The properties of plasma plume were adjusted by the injection type and flow rate of additive oxygen gas in atmospheric pressure helium plasma jet. The plasma characteristics such as plume length, electric current and optical emission spectra (OES) were measured at different flow rates of additive oxygen to helium. The plasma plume length and total current decreased with an increase in the additive oxygen flow rate. The electron excitation temperature estimated by the Boltzmann plot from several excited helium emission lines increased slightly with the additive oxygen flow. The oxygen atom density in the gas phase estimated by actinometry utilizing argon was observed to increase with the additive oxygen flow. The concentration of intracellular reactive oxygen species (ROS) measured by fluorescence assay was found to be not exactly proportional to that of extracellular ROS (measured by OES), but both correlated considerably. It was also observed that the expression levels of p53 and the phospho-p53 were enhanced in the presence of additive oxygen flow compared with those from the pure helium plasma treatment. PMID:25319447

Joh, Hea Min; Choi, Ji Ye; Kim, Sun Ja; Chung, T H; Kang, Tae-Hong

2014-01-01

394

What AGN revergeration maps tell us: plasma simulations of dense accreting gas  

NASA Astrophysics Data System (ADS)

The Cycle 21 large program, "Mapping the AGN Broad-line region by reverberation", will produce the definitive line-continuum reverberation dataset. These HST observations should "clarify the nature of the broad-line region, its role in the apparently complicated accretion/outflow process, and determine definitively the veracity and accuracy of the AGN reverberation-based black hole masses". This proposal aims to improve Cloudy simulations of the dense gas emitting the spectrum so that photoionization theory can meet the challenge posed by these new observations. Two specific advances, implementing physical processes now expected to be important, are proposed. The first involves electron scattering enhancement of H I lines. The lines will be broadened and enhanced by scattering off warm {8 000 K} electrons in the extended neutral gas deep within the cloud or disk, affecting both the line profile and intensity. The second involves collisional suppression of dielectronic recombination, the dominant process responsible for recombination of heavy-element UV lines such as C IV 1549, C III] 1909, Mg II 2798, etc. This is made possible by access to a large body of atomic rates within OpenADAS, and will impact predictions of essentially the entire Broad-line region spectrum. Both advances will become part of Cloudy, a publically available and widely used plasma simulation code.

Ferland, Gary

2014-10-01

395

Bacterial spore inactivation by atmospheric-pressure plasmas in the presence or absence of UV photons as obtained with the same gas mixture  

NASA Astrophysics Data System (ADS)

This paper comprises two main parts: a review of the literature on atmospheric-pressure discharges used for micro-organism inactivation, focused on the inactivation mechanisms, and a presentation of our research results showing, in particular, that UV photons can be the dominant species in the inactivation process. The possibility of achieving spore inactivation through UV radiation using an atmospheric-pressure discharge or its flowing afterglow is the object of a continuing controversy. In fact, the review of the literature that we present shows that a majority of researchers have come to the conclusion that, at atmospheric pressure, chemically reactive species such as free radicals, metastable atoms and molecules always control the inactivation process, while UV photons play only a minor role or no role at all. In contrast, only a few articles suggest or claim that UV photons coming from atmospheric-pressure discharges can, in some cases, inactivate micro-organisms, but the experimental data presented and the supporting arguments brought forward in that respect are relatively incomplete. Using a dielectric-barrier discharge operated at atmospheric pressure in an N2-N2O mixture, we present, for the first time, experiments where micro-organisms are subjected to plasma conditions such that, on the one hand, UV radiation is strong or, on the other hand, there is no UV radiation, the two different situations being obtained with the same experimental arrangement, including the same gas mixture, N2-N2O. To achieve maximum UV radiation, the concentration of the oxidant molecule (N2O) added to N2 needs to be tuned carefully, resulting then in the fastest inactivation rate. The concentration range of the oxidant molecule in the mixture for which the UV intensity is significant is extremely narrow, a fact that possibly explains why such a mode of plasma sterilization was not readily observed. The survival curves obtained under dominant UV radiation conditions are, as we show, akin to those recorded at reduced pressure. Relatively fast spore inactivation can also be obtained under no UV radiation as a result of radicals diffusing deeply inside the spores, leading to oxidative lethal damage.

Boudam, M. K.; Moisan, M.; Saoudi, B.; Popovici, C.; Gherardi, N.; Massines, F.

2006-08-01

396

Plasma metabolomic profiling of dairy cows affected with ketosis using gas chromatography/mass spectrometry  

PubMed Central

Background Ketosis is an important problem for dairy cows` production performance. However, it is still little known about plasma metabolomics details of dairy ketosis. Results A gas chromatography/mass spectrometry (GC/MS) technique was used to investigate plasma metabolic differences in cows that had clinical ketosis (CK, n=22), subclinical ketosis (SK, n=32), or were clinically normal controls (NC, n=22). The endogenous plasma metabolome was measured by chemical derivatization followed by GC/MS, which led to the detection of 267 variables. A two-sample t-test of 30, 32, and 13 metabolites showed statistically significant differences between SK and NC, CK and NC, and CK and SK, respectively. Orthogonal signal correction-partial least-square discriminant analysis (OPLS-DA) revealed that the metabolic patterns of both CK and SK were mostly similar, with the exception of a few differences. The development of CK and SK involved disturbances in many metabolic pathways, mainly including fatty acid metabolism, amino acid metabolism, glycolysis, gluconeogenesis, and the pentose phosphate pathway. A diagnostic model arbitrary two groups was constructed using OPLS-DA and receiver–operator characteristic curves (ROC). Multivariate statistical diagnostics yielded the 19 potential biomarkers for SK and NC, 31 for CK and NC, and 8 for CK and SK with area under the curve (AUC) values. Our results showed the potential biomarkers from CK, SK, and NC, including carbohydrates, fatty acids, amino acids, even sitosterol and vitamin E isomers, etc. 2-piperidinecarboxylic acid and cis-9-hexadecenoic acid were closely associated with metabolic perturbations in ketosis as Glc, BHBA and NEFA for dealing with metabolic disturbances of ketosis in clinical practice. However, further research is needed to explain changes of 2,3,4-trihydroxybutyric acid, 3,4-dihydroxybutyric acid, ?-aminobutyric acid, methylmalonic acid, sitosterol and ?-tocopherol in CK and SK, and to reveal differences between CK and SK. Conclusion Our study shows that some new biomarkers of ketosis from plasma may find new metabolic changes to have clinically new utility and significance in diagnosis, prognosis, and prevention of ketosis in the future. PMID:24070026

2013-01-01

397

Plasma-chemical treatment of hydrogen sulfide in natural gas processing. Final report, May 1991--December 1992  

SciTech Connect

A new process for the treatment of hydrogen sulfide waste that uses microwave plasma-chemical technology has been under development in Russia and the United States. Whereas the present waste-treatment technology, at best, only recovers sulfur, this novel process recovers both hydrogen and sulfur by dissociating hydrogen sulfide in a plasma by means of a microwave or radio-frequency reactor. A research project has been undertaken to determine the suitability of the plasma process in natural gas processing applications. The experiments tested acid-gas compositions with 30--65% carbon dioxide, 0--7% water, and 0--0.2% of a standard mixture of pipeline gas. The balance gas in all cases was hydrogen sulfide. The reactor pressure for the experiments was 50 torr, and the microwave power was 1.0 kW. Conversions of hydrogen sulfide ranged from 80 to 100%, while 35--50% of the carbon dioxide was converted to carbon monoxide. This conversion of carbon dioxide resulted in a loss of hydrogen production and an energy loss from a hydrogen sulfide waste-treatment perspective. Tests of a direct natural gas treatment concept showed that hydrocarbon losses were unacceptably high; consequently, the concept would not be economically viable.

Harkness, J.B.L.; Doctor, R.D. [Argonne National Lab., IL (United States)

1993-05-01

398

The impact of plasma-wall interaction on the gas mixing efficiency in electron cyclotron resonance ion sourcea)  

NASA Astrophysics Data System (ADS)

It is generally accepted that different effects are necessary to explain the gas mixing method of increasing the output of highly charged ions from an ECRIS. The two most important effects are the mass effect and the dilution effect. Their relative weights have not been determined experimentally yet, but it is generally assumed that the mass effect is dominant in standard ECRIS installations with stainless steel plasma chambers. In order to gain more insight into the physics of the gas mixing effect and in particular on the relevance of the dilution process, we have carried out a study where we have investigated the role of the plasma-wall interaction on the gas mixing effect. In this contribution, we shall discuss Charge state distributions spectra, measured at the Frankfurt ECRIS using different working gases, pure argon, a mixture of argon and oxygen, and argon mixed with neon.

Schachter, L.; Stiebing, K. E.; Dobrescu, S.

2012-02-01

399

Combined plasma gas-phase synthesis and colloidal processing of InP/ZnS core/shell nanocrystals  

PubMed Central

Indium phosphide nanocrystals (InP NCs) with diameters ranging from 2 to 5 nm were synthesized with a scalable, flow-through, nonthermal plasma process at a rate ranging from 10 to 40 mg/h. The NC size is controlled through the plasma operating parameters, with the residence time of the gas in the plasma region strongly influencing the NC size. The NC size distribution is narrow with the standard deviation being less than 20% of the mean NC size. Zinc sulfide (ZnS) shells were grown around the plasma-synthesized InP NCs in a liquid phase reaction. Photoluminescence with quantum yields as high as 15% were observed for the InP/ZnS core-shell NCs. PMID:21711589

2011-01-01

400

Combined plasma gas-phase synthesis and colloidal processing of InP/ZnS core/shell nanocrystals.  

PubMed

Indium phosphide nanocrystals (InP NCs) with diameters ranging from 2 to 5 nm were synthesized with a scalable, flow-through, nonthermal plasma process at a rate ranging from 10 to 40 mg/h. The NC size is controlled through the plasma operating parameters, with the residence time of the gas in the plasma region strongly influencing the NC size. The NC size distribution is narrow with the standard deviation being less than 20% of the mean NC size. Zinc sulfide (ZnS) shells were grown around the plasma-synthesized InP NCs in a liquid phase reaction. Photoluminescence with quantum yields as high as 15% were observed for the InP/ZnS core-shell NCs. PMID:21711589

Gresback, Ryan; Hue, Ryan; Gladfelter, Wayne L; Kortshagen, Uwe R

2011-01-01

401

The plasma line revisited as an aeronomical diagnostic - Suprathermal electrons, solar EUV, electron-gas thermal balance  

NASA Technical Reports Server (NTRS)

Spectra of plasma wave intensities in the ionosphere over Arecibo are calculated and compared with those from observations of the plasma line intensity. This approach involving directly observed quantities avoids the uncertainties that have plagued past comparisons with photoelectron theory. In addition, careful comparisons in physically relevant segments of the spectra show that any significant increase in the magnitude of the solar EUV flux would lead to a contradiction of the observed plasma wave intensities. Further, the comparisons indicate that resolution of the thermal electron-gas heat balance problem must be sought through better heat transfer rates (e.g., heating and cooling rates, etc.), rather than in the solar EUV. This approach utilizes more fully the potential of the plasma line experiment as a diagnostic tool for aeronomical studies, (e.g., photoelectrons, auroral secondaries, ionosphere-modification experiments, etc.).

Carlson, H. C., Jr.; Mantas, G. P.; Wickwar, V. B.

1977-01-01

402

Radiation sterilization of new drug delivery systems  

PubMed Central

Radiation sterilization has now become a commonly used method for sterilization of several active ingredients in drugs or drug delivery systems containing these substances. In this context, many applications have been performed on the human products that are required to be sterile, as well as on pharmaceutical products prepared to be developed. The new drug delivery systems designed to deliver the medication to the target tissue or organ, such as microspheres, nanospheres, microemulsion, and liposomal systems, have been sterilized by gamma (?) and beta (?) rays, and more recently, by e-beam sterilization. In this review, the sterilization of new drug delivery systems was discussed other than conventional drug delivery systems by ? irradiation. PMID:24936306

Abuhano?lu, Gürhan

2014-01-01

403

Hysteroscopic Sterilization: History and Current Methods  

PubMed Central

For many practicing obstetrician-gynecologists, tubal ligation was the gold standard by which female sterilization techniques were measured. Yet gynecologic surgeons have simultaneously sought to occlude the fallopian tubes transcervically to avoid discomfort and complications associated with transabdominal approaches. In this review, the history of transcervical sterilization is discussed. Past, current, and upcoming techniques are reviewed. This article focuses on interval sterilization techniques, thus removing post-vaginal and post-cesarean delivery tubal ligations from the discussion. PMID:19015762

Greenberg, James A

2008-01-01

404

Study of the desorption of ethylene oxide fixed on various materials during sterilization by a new procedure  

NASA Technical Reports Server (NTRS)

A continuous sterilization process using ethylene oxide was studied in comparison with a classical method in order to evaluate gas retention as a function of time and temperature on polyethylene, PVC, and rubber materials.

Lacomme, M.; Chaigneau, M.; Lemoan, G.

1977-01-01

405

Current sterilization and packaging methods for polyethylene.  

PubMed

Gamma sterilization in an air environment can induce oxidation in polyethylene. Oxidation can lead to polyethylene embrittlement, compromising mechanical integrity and clinical performance of polyethylene bearings. For these reasons, orthopaedic manufacturers have modified their methods of sterilizing and packaging polyethylene. Two alternative approaches have emerged: sterilization by non-radiation methods and sterilization by gamma irradiation in inert environments. The current study presents a prognosis for clinical performance of polyethylene sterilized with new methods, based on material property analyses (oxidation levels, mechanical properties, crosslink density) of never implanted and retrieved bearings. Data from bearings that were never implanted which were sterilized with the new methods and shelf aged as many as 3 years, show negligible oxidation, ductility above 400%, and ultimate tensile strength near 50 MPa, all exceeding specifications of the American Society for Testing and Materials. There are significant differences in crosslink density (swell ratio) depending on the sterilization method. Retrievals indicate that bearings sterilized with these new methods are performing well clinically and that the majority are not changing with time. The current study suggests that the shelf oxidation problem has been addressed by these new sterilization techniques and that clinical performance at short followup is acceptable. However, long-term clinical performance must be evaluated in the future. PMID:10611860

Bargmann, L S; Bargmann, B C; Collier, J P; Currier, B H; Mayor, M B

1999-12-01

406

Determination of cocaine and cocaethylene in plasma by solid-phase microextraction and gas chromatography-mass spectrometry.  

PubMed

The present paper describes a method for the simultaneous determination of cocaine and cocaethylene in plasma. It was based in the extraction of the analytes by solid-phase microextraction (SPME), and gas chromatography-mass spectrometry (GC-MS) was used to identify and quantify the analytes in selected ion monitoring (SIM) mode. The method showed to be very simple, rapid and sensitive. The method was validated for the two compounds, including linearity (range 25-1000 ng/mL) and the main precision parameters. It was applied to ten plasma samples from cocaine and alcohol users, obtaining positive results in all cases. PMID:16935038

Alvarez, Iván; Bermejo, Ana María; Tabernero, María Jesús; Fernández, Purificación; López, Patricia

2007-01-01

407

DARK MATTER AND STERILE NEUTRINOS  

E-print Network

Dark matter has been recognized as an essential part of matter for over 70 years now, and many suggestions have been made, what it could be. Most of these ideas have centered on Cold Dark Matter, particles that are predicted in extensions of standard particle physics, such as supersymmetry. Here we explore the concept that dark matter is sterile neutrinos, particles that are commonly referred to as Warm Dark Matter. Such particles have keV masses, and decay over a very long time, much longer than the Hubble time. In their decay they produce X-ray photons which modify the ionization balance in the very early universe, increasing the fraction of molecular Hydrogen, and thus help early star formation. Sterile neutrinos may also help to understand the baryon-asymmetry, the pulsar kicks, the early growth of black holes, the minimum mass of dwarf spheroidal galaxies, as well as the shape and smoothness of dark matter halos. As soon as all these tests have been made quantitative in their various parameters, we may focus on the creation mechanism of these particles, and could predict the strength of the sharp X-ray emission line, expected from any large dark matter assembly. A measurement of this X-ray emission line would be definitive proof for the existence of may be called weakly interacting neutrinos, or WINs.

Peter L. Biermann; Faustin Munyaneza

2007-01-01

408

A rapid analysis of plasma/serum ethylene and propylene glycol by headspace gas chromatography.  

PubMed

A rapid headspace-gas chromatography (HS-GC) method was developed for the analysis of ethylene glycol and propylene glycol in plasma and serum specimens using 1,3-propanediol as the internal standard. The method employed a single-step derivitization using phenylboronic acid, was linear to 200 mg/dL and had a lower limit of quantitation of 1 mg/dL suitable for clinical analyses. The analytical method described allows for laboratories with HS-GC instrumentation to analyze ethanol, methanol, isopropanol, ethylene glycol, and propylene glycol on a single instrument with rapid switch-over from alcohols to glycols analysis. In addition to the novel HS-GC method, a retrospective analysis of patient specimens containing ethylene glycol and propylene glycol was also described. A total of 36 patients ingested ethylene glycol, including 3 patients who presented with two separate admissions for ethylene glycol toxicity. Laboratory studies on presentation to hospital for these patients showed both osmolal and anion gap in 13 patients, osmolal but not anion gap in 13 patients, anion but not osmolal gap in 8 patients, and 1 patient with neither an osmolal nor anion gap. Acidosis on arterial blood gas was present in 13 cases. Only one fatality was seen; this was a patient with initial serum ethylene glycol concentration of 1282 mg/dL who died on third day of hospitalization. Propylene glycol was common in patients being managed for toxic ingestions, and was often attributed to iatrogenic administration of propylene glycol-containing medications such as activated charcoal and intravenous lorazepam. In six patients, propylene glycol contributed to an abnormally high osmolal gap. The common presence of propylene glycol in hospitalized patients emphasizes the importance of being able to identify both ethylene glycol and propylene glycol by chromatographic methods. PMID:23741644

Ehlers, Alexandra; Morris, Cory; Krasowski, Matthew D

2013-12-01

409

The discharge mode transition and O(5p1) production mechanism of pulsed radio frequency capacitively coupled plasma  

NASA Astrophysics Data System (ADS)

The discharge mode transition from uniform plasma across the gas gap to the ? mode happens at the rising phase of the pulsed radio frequency capacitively coupled plasma (PRF CCP). This transition is attributed to the fast increasing stochastic heating at the edge of sheath. In the second stage with the stable current and voltage amplitude, the consistency between experimental and numerical spatial-temporal 777 nm emission profile suggests that He* and He2* dominate the production of O(5p1) through dissociation and excitation of O2. Finally, the sterilization efficiency of PRF CCP is found to be higher than that of plasma jet.

Liu, X. Y.; Hu, J. T.; Liu, J. H.; Xiong, Z. L.; Liu, D. W.; Lu, X. P.; Shi, J. J.

2012-07-01

410

Ion angular distribution in plasma of vacuum arc ion source with composite cathode and elevated gas pressure.  

PubMed

The Metal Vapor Vacuum Arc (MEVVA) ion sources are capable of generating ion beams of almost all metals of the periodic table. For this kind of ion source, a combination of gas feeding with magnetic field allows the simultaneous generation of both metal and gaseous ions. That makes the MEVVA ion source an excellent instrument for science and application. This work presents results of investigation for ion angular distributions in vacuum arc plasma of Mevva-V.Ru ion source for composite cathodes and for elevated gas pressure. It was shown that for all the cathode materials, singly charged ions have wider angular distribution than multiply charged ions. Increasing the working gas pressure leads to a significant change in the angular distribution of gaseous ions, while with the distribution of metal ions gas remains practically unchanged. The reasons for such different influences are discussed. PMID:24593598

Nikolaev, A G; Savkin, K P; Yushkov, G Yu; Oks, E M

2014-02-01

411

Control of nanoparticle synthesis using physical and chemical dynamics of gas-liquid interfacial non-equilibrium plasmas  

NASA Astrophysics Data System (ADS)

Plasmas generated in contact with liquids have attracted considerable attention as a novel reactive field in nano-biomaterial creation because the brand-new chemical and biological reactions are yielded at the gas-liquid interface, which are induced by the physical actions of the non-equilibrium plasmas. Highly ordered periodic structures of gold nanoparticles (AuNPs) are formed by transcribing the plasma structure to the surface of the liquid, where the spatially selective synthesis of the AuNPs is realized. Furthermore, the plasma structure is controlled using a ring or disk electrode under strong magnetic fields up to 4 T. The ring structure of the nanoparticles is found to be formed in accordance with the shadow region of the ring electrode. It is found that the AuNPs are synthesized by the reduction effect of the hydrogen radical via irradiation of neutral radicals of the plasma and are destroyed by the oxidation effect of the fluorine radical via high-energy plasma-ion irradiation.

Kaneko, T.; Takahashi, S.; Hatakeyama, R.

2012-12-01

412

The effect of processing parameters on the synthesis of tungsten oxide nanomaterials by a modified plasma arc gas condensation technique.  

PubMed

In the present study, tungsten oxide nanomaterials were synthesized by a modified plasma arc gas condensation technique. The effects of processing parameters (plasma current ranged from 70-90 A and chamber pressure ranged from 200-600 torr) on the preparation of tungsten oxide nanomaterials were investigated. X-ray diffraction results showed that all of the nanomaterials synthesized in the present study exhibited W5O14 phase. Field emission scanning electron microscopy and transmission electron microscopy examinations revealed that the tungsten oxide nanomaterials were equiaxed when prepared at a relatively low plasma current of 70 A, and turned into rod-like nanoparticles with increasing plasma current (80 or 90 A). Generally, the relative amount, diameter, and length of tungsten oxide nanorods increased with increasing plasma currents or chamber pressures. The aspect ratio of the as-prepared tungsten oxide nanorods reached a maximum of 12.7 when a plasma current of 90 A and a chamber pressure of 400 torr were used. A growth mechanism for tungsten oxide nanorods was proposed. PMID:21125919

Su, Cherng-Yuh; Lin, Hsuan-Ching; Yang, Tsung-Kun; Lin, Chung-Kwei

2010-08-01

413

Influence of dust-particle concentration on gas-discharge plasma.  

PubMed

A self-consistent kinetic model of a low-pressure dc glow discharge with dust particles based on Boltzmann equation for the electron energy distribution function is presented. The ions and electrons production in ionizing processes as well as their recombination on the dust-particle surface and on the discharge tube wall were taken into account. The influence of dust-particle concentration N(d) on gas discharge and dust particles parameters was investigated. It is shown