These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Gas plasma sterilization--application of space-age technology.  

PubMed

Gas plasma sterilization is new to the healthcare field. The first such sterilizer has been manufactured by Advanced Sterilization Products (J&J, Irvine, CA). The system uses hydrogen peroxide as the substrate gas and radio frequency emissions to generate plasma. This system is a low-temperature, quick-acting process with no toxic residues. It appears that this sterilizer system holds promise in the healthcare field and could help to reduce the use of ethylene oxide. PMID:7594394

Crow, S; Smith, J H

1995-08-01

2

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

3

Plasma Sterilization Technology for Spacecraft Applications  

NASA Technical Reports Server (NTRS)

The application of plasma gas technology to sterilization and decontamination of spacecraft components is considered. Areas investigated include: effective sterilizing ranges of four separate gases; lethal constituents of a plasma environment; effectiveness of plasma against a diverse group of microorganisms; penetrating efficiency of plasmas for sterilization; and compatibility of spacecraft materials with plasma environments. Results demonstrated that plasma gas, specifically helium plasma, is a highly effective sterilant and is compatible with spacecraft materials.

Fraser, S. J.; Olson, R. L.; Leavens, W. M.

1975-01-01

4

Sterilization of Bacillus subtilis Spores Using an Atmospheric Plasma Jet with Argon and Oxygen Mixture Gas  

NASA Astrophysics Data System (ADS)

To determine an efficient sterilization mechanism, Bacillus subtilis spore samples were exposed to an atmospheric plasma jet. By using argon/oxygen mixture gas, the decimal reduction value was reduced from 60 s (using argon gas) to 10 s. More dramatically, after 5 min treatment, the colony-forming unit (CFU) was reduced by six orders. To understand the underlying mechanism of the efficient sterilization by plasma, the contributions from heat, UV radiation, charged particles, ozone, and reactive oxygen radicals were distinguished in this work, showing that charged particles and ozone were the main killing factors. The shape changes of the spores were also discussed.

Shen, Jie; Cheng, Cheng; Fang, Shidong; Xie, Hongbing; Lan, Yan; Ni, Guohua; Meng, Yuedong; Luo, Jiarong; Wang, Xiangke

2012-03-01

5

Effects of additional vapors on sterilization of microorganism spores with plasma-excited neutral gas  

NASA Astrophysics Data System (ADS)

Some fundamental experiments are carried out in order to develop a plasma process that will uniformly sterilize both the space and inner wall of the reactor chamber at atmospheric pressure. Air, oxygen, argon, and nitrogen are each used as the plasma source gas to which mixed vapors of water and ethanol at different ratios are added. The reactor chamber is remotely located from the plasma area and a metal mesh for eliminating charged particles is installed between them. Thus, only reactive neutral particles such as plasma-excited gas molecules and radicals are utilized. As a result, adding vapors to the source gas markedly enhances the sterilization effect. In particular, air with water and/or ethanol vapor and oxygen with ethanol vapor show more than 6-log reduction for Geobacillus stearothermophilus spores.

Matsui, Kei; Ikenaga, Noriaki; Sakudo, Noriyuki

2015-01-01

6

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

7

Sterilization by oxygen plasma  

NASA Astrophysics Data System (ADS)

The use of polymeric medical devices has stimulated the development of new sterilization methods. The traditional techniques rely on ethylene oxide, but there are many questions concerning the carcinogenic properties of the ethylene oxide residues adsorbed on the materials after processing. Another common technique is the gamma irradiation process, but it is costly, its safe operation requires an isolated site and it also affects the bulk properties of the polymers. The use of a gas plasma is an elegant alternative sterilization technique. The plasma promotes an efficient inactivation of the micro-organisms, minimises the damage to the materials and presents very little danger for personnel and the environment. Pure oxygen reactive ion etching type of plasmas were applied to inactivate a biologic indicator, the Bacillus stearothermophilus, to confirm the efficiency of this process. The sterilization processes took a short time, in a few minutes the mortality was complete. In situ analysis of the micro-organisms' inactivating time was possible using emission spectrophotometry. The increase in the intensity of the 777.5 nm oxygen line shows the end of the oxidation of the biologic materials. The results were also observed and corroborated by scanning electron microscopy.

Moreira, Adir José; Mansano, Ronaldo Domingues; Andreoli Pinto, Terezinha de Jesus; Ruas, Ronaldo; Zambon, Luis da Silva; da Silva, Mônica Valero; Verdonck, Patrick Bernard

2004-07-01

8

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

9

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

10

The application of a non-thermal plasma generated by gas-liquid gliding arc discharge in sterilization  

NASA Astrophysics Data System (ADS)

Gliding arc discharge has been investigated in recent years as an innovative physicochemical technique for contaminated water treatment at atmospheric pressure and ambient temperature. In this study we tested a gas-liquid gliding arc discharge reactor, the bacterial suspension of which was treated circularly. When the bacterial suspension was passed through the electrodes and circulated at defined flow rates, almost 100% of the bacteria were killed in less than 3.0 min. Experimental results showed that it is possible to achieve an abatement of 7.0 decimal logarithm units within only 30 s. Circulation flow rates and types of feeding gas caused a certain impact on bacteria inactivation, but the influences are not obvious. So, under the promise of sterilization effect, industrial applications can select their appropriate operating conditions. All inactivation curves presented the same three-phase profile showing an apparent sterilization effect. Analysis of the scanning electron microscope images of bacterial cells supports the speculation that the gas-liquid gliding arc discharge plasma is acting under various mechanisms driven essentially by oxidation and the effect of electric field. These results enhance the possibility of applying gas-liquid gliding arc discharge decontamination systems to disinfect bacterial-contaminated water. Furthermore, correlational research indicates the potential applications of this technology in rapid sterilization of medical devices, spacecraft and food.

Du, Chang Ming; Wang, Jing; Zhang, Lu; Xia Li, Hong; Liu, Hui; Xiong, Ya

2012-01-01

11

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

12

Plasma Sterilization: New Epoch in Medical Textiles  

NASA Astrophysics Data System (ADS)

Clothing is perceived to be second skin to the human body since it is in close contact with the human skin most of the times. In hospitals, use of textile materials in different forms and sterilization of these materials is an essential requirement for preventing spread of germs. The need for appropriate disinfection and sterilization techniques is of paramount importance. There has been a continuous demand for novel sterilization techniques appropriate for use on various textile materials as the existing sterilization techniques suffer from various technical and economical drawbacks. Plasma sterilization is the alternative method, which is friendlier and more effective on the wide spectrum of prokaryotic and eukaryotic microorganisms. Basically, the main inactivation factors for cells exposed to plasma are heat, UV radiation and various reactive species. Plasma exposure can kill micro-organisms on a surface in addition to removing adsorbed monolayer of surface contaminants. Advantages of plasma surface treatment are removal of contaminants from the surface, change in the surface energy and sterilization of the surface. Plasma sterilization aims to kill and/or remove all micro-organisms which may cause infection of humans or animals, or which can cause spoilage of foods or other goods. This review paper emphasizes necessity for sterilization, essentials of sterilization, mechanism of plasma sterilization and the parameters influencing it.

Senthilkumar, P.; Arun, N.; Vigneswaran, C.

2015-01-01

13

[Studies on the method of sterilization with ethylene oxide gas. 1. Sterilization procedure and sterilizing effect].  

PubMed

Undertaken to ensure perfection of sterilization with ethylene oxide gas (EO gas) in routine clinical laboratory practice, an investigation was made of the relationship between sterilization procedure and sterilizing effect using the film bag delivery system and chamber system. Using a biological indicator as a monitor of sterilizing effect, the efficiency of sterilization was studied under various likely conditions and compared. The results led to the following conclusions: 1. Sterilization with EO gas by the film bag delivery system, because of this procedure being unable to be performed at a constant temperature, was shown to prove inadequate due to insufficient exposure to gas especially in winter season (when room temperature fell below 10 degrees C). 2. With the EO gas sterilization method using the film bag delivery system, which is believed to be effective within the ordinary range of humidity of the atmosphere, sterilizing effect was recognized to be affected by excess wetting of an object of sterilization that was caused by inadvertent manipulation or due to a predisposing attribute of the object, such as shape or outline. 3. All materials are sterilized upon being packaged. It is necessary therefore to make best choice of package material with respect of texture and size. Reuse influence to sterilizing effect. 4. The method of sterilization with EO gas using the chamber system has the advantage in that operating conditions are all automatically controlled. For this reason, there was not a single instance of failure to sterilize due to inappropriateness of temperature and humidity. From these results it is concluded that sterilising effect was affected by sterilization procedure and condition.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2489348

Arimoto, H; Ukisu, S; Yamada, Y; Sano, K; Kanri, T

1989-12-01

14

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

15

Air and Water Sterilization using Non-Thermal Plasma  

Microsoft Academic Search

Summary form only given. Various investigations have proven the effectiveness of nonthermal plasma against microorganisms. This sterilization effect is of great importance in countering the threat of bioterrorism. So far, most of sterilization studies have been in the direction of surface sterilization. The sterilization effect of plasma on air and water were investigated in this study. For air sterilization, a

N. D. Vaze; K. P. Arjunan; M. J. Gallagher; V. N. Vasilets; A. Gutsol; A. Fridman; S. Anandan

2007-01-01

16

Gas dynamics of ethylene oxide during sterilization  

NASA Astrophysics Data System (ADS)

This article reports a case study of the dynamics of ethylene oxide gas during sterilization using a microwave spectrometer. A diffusion equation is used to describe the processes of gas penetration, gas sorption, and chemical reactions. The three processes, although mathematically related, may be solved separately under simplified assumptions. This permits the prediction of gas penetration and sorption as well as the effect of chemical reactions upon the gas concentration for loads of differing dimensions and densities.

Zhu, Z.; Matthews, I. P.; Wang, C.

1999-07-01

17

Observation of Effectiveness of Clinical Sterilization by CASP-80A Low-Temperature Plasma Sterilizer  

NASA Astrophysics Data System (ADS)

The influence on the effectiveness of sterilization by low-temperature plasma sterilizer CASP-80A was investigated so as to provide a theoretical basis for reducing medical costs and achieving ideal sterilization effectiveness. To conduct the on-site simulation test, a clinical material sterilization test and a test of the influence of organic substance were conducted, the former by using the representative of Bacillus Stearothermophilus, preparing the bacteria-contaminated carrier through polytetrafluoroethylene (PTFE) simulated hose endoscopes, and the latter by using calf serum as the influence factor of the organic substance. The results show that the CASP-80A low-temperature plasma sterilizer could achieve effective sterilization by either the short-cycle or the long-cycle sterilization method depending on different materials, apparatus, and extent of contamination. The organic substances could influence the effectiveness of sterilization by the low-temperature plasma (H2O2) sterilizer.

Li, Si; Zhang, Yangde; Liu, Weidong

2006-09-01

18

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

19

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

E-print Network

Atmospheric Pressure Humid Argon DBD Plasma for the Application of Sterilization - Measurement peroxide have been measured downstream of an atmospheric pressure humid argon dielectric barrier discharge. The results of experiments on the use of post-discharge effluent gas of humid argon plasma for sterilization

Paris-Sud XI, Université de

20

The efficacy of low temperature plasma (LTP) sterilization, a new sterilization technique.  

PubMed

The efficacy of low temperature plasma (LTP) sterilization, a newly developed sterilization procedure was tested. Following experiments were carried out: Determination of the most resistant test organism, influence of 10% and 20% defibrinated sheep blood or varying salt concentrations on the efficacy of the sterilization process, influence of the carrier position in the sterilization chamber and in the sterilization pouches, influence of a loaded sterilization chamber, comparative efficacy of EO and LTP, steel carriers with a blood burden of 0%, 5% and 10%, comparative efficacy of EO and LTP, strip carriers in endoscopes, blood burden 0% and 10%, with and without adaptors, evaluation of two bioindicator models. B. pumilus was the test spore that overall seemed to be most resistant to the sterilization procedure. Supplementation of the test suspension with blood or saline crystals resulted in significantly reduced efficacy and has to be avoided in practical operation. The fully loaded sterilization chamber or the position of germ carriers on the shelves had no negative influence on the effectivity of the sterilization process. There were no significant differences between EO and LTP, the blood burden not exceeding 5%. 10% blood burden resulted in a significantly weaker action of LTP. For sterilization of long lumens adaptors containing hydrogen peroxide are necessary. An appropriate bioindicator tube model is introduced. PMID:8397686

Höller, C; Martiny, H; Christiansen, B; Rüden, H; Gundermann, K O

1993-07-01

21

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

22

Study of Inactivation Factors in Low Temperature Surface-wave Plasma Sterilization  

NASA Astrophysics Data System (ADS)

In this study we investigated the low temperature surface-wave plasma sterilization of directly and indirectly exposed Geobacillus stearothermophilus spores with a large-volume microwave plasma device. The air-simulated gas mixture was used to produce the plasma. The water vapor addition to the gas mixture improved the sterilization efficiency significantly. The effect of ultraviolet photons produced along with plasma to inactivate the spores was studied using a separate chamber, which was evacuated to less than one mTorr and was observed that spores were sterilized within 60 min. The scanning electron microscopy images revealed no significant changes in the actual size of the spores with that of untreated spores despite the survival curve shown that the spores were inactivated.

Singh, Mrityunjai Kumar; Xu, Lei; Ogino, Akihisa; Nagatsu, Masaaki

23

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

24

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

25

Effect of ozone on sterilization of Penicillium digitatum using non-equilibrium atmospheric pressure plasma  

NASA Astrophysics Data System (ADS)

Methyl bromide has been sprayed to the crops for protecting from insects and virus, but has high ozone depletion potential. Thus, the development of substitute-technology has been strongly required. We have investigated a plasma sterilization for spores of Penicillium digitatum, which causes green mold disease of the crops, using non-equilibrium atmospheric pressure plasma. The sterilization was caused by UV light, ozone, O and OH radicals. In this study, ozone density was measured and the effect to sterilization was discussed. The plasma was generated at an alternative current of 6kV and Ar gas flow rate of 3L/min. In order to investigate the sterilization mechanism of ozone, the absolute density of ozone was measured using ultraviolet absorption spectroscopy and was from 2 to 8 ppm. The sterilization by this plasma was larger than that by the ozonizer (03:600ppm). It is confirmed that the effect of ozone to the sterilization of Penicillium digitatum would be small.

Ohta, Takayuki; Iseki, Sachiko; Ito, Masafumi; Kano, Hiroyuki; Higashijima, Yasuhiro; Hori, Masaru

2008-10-01

26

Rapid Sterilization of Escherichia coli by Solution Plasma Process  

NASA Astrophysics Data System (ADS)

Solution plasma (SP), which is a discharge in the liquid phase, has the potential for rapid sterilization of water without chemical agents. The discharge showed a strong sterilization performance against Escherichia coli bacteria. The decimal value (D value) of the reduction time for E. coli by this system with an electrode distance of 1.0 mm was estimated to be approximately 1.0 min. Our discharge system in the liquid phase caused no physical damage to the E. coli and only a small increase in the temperature of the aqueous solution. The UV light generated by the discharge was an important factor in the sterilization of E. coli.

Andreeva, Nina; Ishizaki, Takahiro; Baroch, Pavel; Saito, Nagahiro

2012-12-01

27

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

28

[Studies on the method of sterilization with ethylene oxide gas. 2. Residual EO gas on sterilized objects].  

PubMed

Ethylene oxide gas (EO gas) adsorbed onto sterilized objects was quantitated in an effort to take a safety measure against residual EO gas following its use in sterilization. We measured residual amounts of EO gas adsorbed onto laboratory wares, small medical tools and appliances just after post-sterilization airation to examine whether they were rendered entirely free from EO gas by the process. The results led us to arrive at the following conclusions: 1. EO gas was recognized to remain on sterilized objects even after allowing them to stand for about 16 hours following airation. 2. The amount of residual EO gas was smaller on metallic products and larger on rubber products (notably rubber gloves). An exceedingly high concentration of EO gas was noted to remain on a tooth-brush, among other plastic materials. These facts seem to indicate that the amount of residual EO gas is closely related to the texture and shape of materials to be sterilized. 3. As regards the potential toxicity of residual EO gas. However, their sensitivity was proved to be questionable, judgment on a result being subject to considerable individual variations. 4. Nevertheless, it is incontestable that these devices can at least provide a rough estimate of unavailing since monitoring by direct measurement of residual EO gas is virtually infeasible from a practical point of view. PMID:2489349

Arimoto, H; Wakui, H; Sakagami, M; Abe, Y; Magara, K; Yohkoh, N; Kanri, T

1989-12-01

29

Sterilization of Surfaces with a Handheld Atmospheric Pressure Plasma  

NASA Astrophysics Data System (ADS)

Low temperature, atmospheric pressure plasmas have shown great promise for decontaminating the surfaces of materials and equipment. In this study, an atmospheric pressure, oxygen and argon plasma was investigated for the destruction of viruses, bacteria, and spores. The plasma was operated at an argon flow rate of 30 L/min, an oxygen flow rate of 20 mL/min, a power density of 101.0 W/cm^3 (beam area = 5.1 cm^2), and at a distance from the surface of 7.1 mm. An average 6log10 reduction of viable spores was obtained after only 45 seconds of exposure to the reactive gas. By contrast, it takes more than 35 minutes at 121^oC to sterilize anthrax in an autoclave. The plasma properties were investigated by numerical modeling and chemical titration with nitric oxide. The numerical model included a detailed reaction mechanism for the discharge as well as for the afterglow. It was predicted that at a delivered power density of 29.3 W/cm^3, 30 L/min argon, and 0.01 volume% O2, the plasma generated 1.9 x 10^14 cm-3 O atoms, 1.6 x 10^12 cm-3 ozone, 9.3 x 10^13 cm-3 O2(^1?g), and 2.9 x 10^12 cm-3 O2(^1?^+g) at 1 cm downstream of the source. The O atom density measured by chemical titration with NO was 6.0 x 10^14 cm-3 at the same conditions. It is believe that the oxygen atoms and the O2(^1?g) metastables were responsible for killing the anthrax and other microorganisms.

Hicks, Robert; Habib, Sara; Chan, Wai; Gonzalez, Eleazar; Tijerina, A.; Sloan, Mark

2009-10-01

30

[The effect of gas concentration on ethylene oxide sterilization].  

PubMed

Ethylene oxide (EO) gas is widely used for sterilization of medical instruments and supplies. The gas being used in our hospital consists of 20% EO and 80% carbon dioxide and is packed in a cylinder as liquefied gas. We investigated the relationship between the composition of the gas and the amount of EO gas used by measuring the EO concentration in a sterilizer. The concentration of EO was increased as the amount of gas increased, and it decreased sharply when the remaining gas in the cylinder decreased up to about 12% of its initial value. This value agreed with the calculated one by gas-liquid equilibrium when all of the liquefied gas was consumed and only saturated gas remained in the cylinder. PMID:2609043

Hori, H; Miura, Y; Kojima, A

1989-12-01

31

Low Energy Nanosecond Pulsed Plasma Sterilization for Endodontic Applications  

Microsoft Academic Search

The development of effective and safe methods for root canal disinfection, including mechanical, chemical and laser techniques, remains an important problem, and complete eradication of bacteria from the root canal system with minimum tissue trauma is still a serious challenge for endodontists. Recently, a pulsed, hollow-electrode based plasma dental probe has been developed to sterilize the root canal system during

C. Jiang; P. T. Vernier; M. T. Chen; Y. H. Wu; L. L. Wang; M. A. Gundersen

2008-01-01

32

Comparison of two radio-frequency plasma sterilization processes using microspot evaluation of microbial inactivation.  

PubMed

In this study, we evaluated gas plasma surface sterilization methods in a specific sterilizer. We have introduced a new monitoring method using 0.4 microm pore size membranes, which in this study gave the information corresponding to 3000 exposed biological indicators per treatment cycle. This enabled us to compare the fraction of inoculates that showed no growth after exposure for 30 different locations in the chamber, and hereby identify weak and strong spots in the chamber with regard to sporicidal effect. Membranes were also used to expose a broad spectrum of soil bacteria for plasma treatment at four different conditions. The organisms were identified using PCR and sequencing. The test showed that Bacillus stearothermophilus spores were inactivated at the slowest rate among the tested microorganisms. Further alpha-proteobacteria (Gram negative) seemed more sensitive than the rest of the tested organisms. The microspot evaluation approach has been a most useful tool in the assessment of sterilization performance in sterilizers that do not have clear measurable parameters related to the sterilization. PMID:16362959

Lassen, Klaus S; Johansen, Jens E; Grün, Reinar

2006-07-01

33

Biological and Agricultural Studies on Application of Discharge Plasma and Electromagnetic Fields 2.Sterilization by Electrical Discharges and Plasmas  

NASA Astrophysics Data System (ADS)

The use of electrical discharges and plasmas for sterilization is reviewed. Plasmas generated by a silent discharge, a pulse discharge, and a radio frequency discharge under atmospheric pressure have been used for sterilization. Furthermore, a microwave plasma, a radio frequency plasma, and a low temperature plasma with hydrogen peroxide under low pressure conditions have been also used for sterilization. Sterilization results from injury caused by the discharge current, and from the reaction of species affected by the discharge. A silent discharge with air or oxygen is most effective for the sterilization. Nitrogen discharge also has a significant effect, however, argon discharge does not have a significant effect.

Watanabe, Takayuki

34

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

35

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

36

Effect of dielectric and liquid on plasma sterilization using dielectric barrier discharge plasma.  

PubMed

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

37

Sterilization and decontamination of surfaces using atmospheric pressure plasma discharges  

SciTech Connect

The goal of the program is to demonstrate that an atmospheric pressure plasma discharge can rapidly and effectively sterilize or decontaminate surfaces that are contaminated with model biological and chemical warfare agents. 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. the work done to date has focused on the sterilization of aluminum, polished steel and tantalum foil metal coupons, about 2 cm on a side and 2 mm thick, which have been inoculated with up to 10{sup 6} spores per coupon of Bacillus subtilis var niger or Bascillus stearothermorphilus. Results indicate that 5 minute exposures to the atmospheric pressure plasma discharge can reduce the viable spore count by 4 orders of magnitude. The atmospheric pressure discharge is also effective in decomposing organic phosphate compounds that are stimulants for chemical warfare agents. Details of the decomposition chemistry, by-product formation, and electrical energy consumption of the system will be discussed.

Garate, E.; Gornostaeva, O.; Alexeff, I.; Kang, W.L.

1999-07-01

38

Comparison of Sterilizing Effect of Nonequilibrium Atmospheric-Pressure He/O2 and Ar/O2 Plasma Jets  

NASA Astrophysics Data System (ADS)

The sterilizing effect of the non-equilibrium atmospheric pressure plasma jet by applying it to the Bacillus subtilis spores is invesigated. A stable glow discharge in argon or helium gas fed with active gas (oxygen), was generated in the coaxial cylindrical reactor powered by the radio-frequency power supply at atmospheric pressure. The experimental results indicated that the efficiency of killing spores by making use of an Ar/O2 plasma jet was much better than with a He/O2 plasma jet. The decimal reduction value of Ar/O2 and He/O2 plasma jets under the same experimental conditions was 4.5 seconds and 125 seconds, respectively. It was found that there exists an optimum oxygen concentration for a certain input power, at which the sterilization efficiency reaches a maximum value. It is believed that the oxygen radicals are generated most efficiently under this optimum condition.

Li, Shouzhe; Lim, Jinpyo

2008-02-01

39

Evaluation of Penicillium digitatum sterilization using non-equilibrium atmospheric pressure plasma by terahertz time-domain spectroscopy  

NASA Astrophysics Data System (ADS)

Recently, the plasma sterilization has attracted much attention as a new sterilization technique that takes the place of spraying agricultural chemicals. The conventional methods for sterilization evaluation, was demanded to culture the samples for several days after plasma treatment. Then, we focused on Terahertz time-domain spectroscopy (THz-TDS). At the THz region, vibrational modes of biological molecules and fingerprint spectra of biologically-relevant molecules were also observed. In this study, our purpose was measurement of the fingerprint spectrum of the Penicillium digitatum (PD) spore and establishment of sterilization method by THz-TDS. The sample was 40mg/ml PD spore suspensions which dropped on cover glass. The atmospheric pressure plasma generated under the conditions which Ar gas flow was 3slm, and alternating voltage of 6kV was applied. The samples were exposed the plasma from 10mm distance for 10 minutes. We could obtain the fingerprint spectrum of the PD spore from 0.5 to 0.9THz. This result indicated the possibility of in-situ evaluation for PD sterilization using THz-TDS.

Hiraoka, Takehiro; Ebizuka, Noboru; Takeda, Keigo; Ohta, Takayuki; Kondo, Hiroki; Ishikawa, Kenji; Kawase, Kodo; Ito, Masafumi; Sekine, Makoto; Hori, Masaru

2011-11-01

40

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

41

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

42

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

E-print Network

sterilization methods. Using a relatively small, low temperature, atmospheric, dielectric barrier discharge of liquid on the dielectric surface. Of the two dielectric substrates tested (FR4 and semi-ceramic (SC. Natural and fabricated plasmas occur over a wide range of pressures, temperatures and electron number

Roy, Subrata

43

Low-Temperature Sterilization with Surface-Wave-Excited Oxygen Plasma  

NASA Astrophysics Data System (ADS)

Low-temperature plasma sterilization has been experimentally demonstrated using surface-wave plasma excited by a 2.45 GHz microwave. With the spores of Bacillus stearothermophilus and Bacillus subtilis as biological indicators, we have carried out the plasma sterilization experiments by varying the irradiation period of oxygen plasma discharges. It was experimentally confirmed that the spores with a population of 1.5 × 106 were sterilized by irradiating them with oxygen plasma discharges generated with a microwave power of 700 W at a pressure of 60-80 mTorr for 3 min or longer. From the scanning electron microscopy (SEM) analysis of the spores, we found that the sterilized spores clearly had different sizes and shapes compared with those before the plasma irradiation. Furthermore, present experiments suggested that the changes of spore shapes were mainly attributed to the reactive interactions with oxygen radicals.

Nagatsu, Masaaki; Terashita, Fumie; Koide, Yukio

2003-07-01

44

[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

45

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

46

Plasma sterilization of Geobacillus Stearothermophilus by O{mathsf2}:N{mathsf2} RF inductively coupled plasma  

NASA Astrophysics Data System (ADS)

The aim of this work is to identify the main process responsible for sterilization of Geobacillus Stearothermophilus spores in O{2}:N{2} RF inductively coupled plasma. In order to meet this objective the sterilization efficiencies of discharges in mixtures differing in the initial O{2}/N{2} ratios are compared with plasma properties and with scanning electron microscopy images of treated spores. According to the obtained results it can be concluded that under our experimental conditions the time needed to reach complete sterilization is more related to O atom density than UV radiation intensity, i.e. complete sterilization is not related only to DNA damage as in UV sterilization but more likely to the etching of the spore.

Kylián, O.; Sasaki, T.; Rossi, F.

2006-05-01

47

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

48

Plasmas Generated With Gas Mixtures at the Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

Several applications, such as metal surface nitriding, medical instrument sterilization and chemical analysis, have been developed or improved using a gas mixture as plasmogen gas. Research carried out on these subjects covers the aspect of knowing the processes that take place in plasmas which depend on the densities of the different plasma particles and their energy values. In this paper, the results obtained from the application of spectroscopic techniques for the characterization of surface wave discharges at the atmospheric pressure, generated with more than one gas type, are presented, particularly for the Ar-He, Ar-Ne and Ar-N2 plasmas.

Calzada, M. D.; Muñoz, J.; Rincón, R.; Jiménez, M.; Sáez, M.

49

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

50

Destruction of Bacterial Biofilms Using Gas Discharge Plasma  

NASA Astrophysics Data System (ADS)

Biofilms are bacterial communities embedded in an exopolysaccharidic matrix with a complex architectural structure. Bacteria in biofilms show different properties from those in free life thus, conventional methods of killing bacteria are often ineffective with biofilms. The use of plasmas potentially offers an alternative to conventional sterilization methods since plasmas contain a mixture of charged particles, chemically reactive species, and UV radiation. 4 and 7 day-old biofilms were produced using two bacterial species: Rhizobium gallicum and Chromobacterium violaceum. Gas discharge plasma was produced by using an AtomfloTM reactor (Surfx Technologies) and bacterial biofilms were exposed to it for different periods of time. Our results show that a 10-minute plasma treatment was able to kill 100% of the cells in most cases. Optical emission spectroscopy was used to study plasma composition which is then correlated with the effectiveness of killing. These results indicate the potentiality of plasma as an alternative sterilization method. Supported by CSuperb.

Abramzon, Nina

2005-03-01

51

Personal Exposure Level and Environmental Ethylene Oxide Gas Concentration in Sterilization Facilities of Hospitals in Japan  

Microsoft Academic Search

Personal and environmental (stationary) ethylene oxide (EO) gas concentrations in gas sterilization facilities were measured at six workplaces in five hospitals. An ethylene oxide gas monitor (3M #3551) was used for both personal and stationary samplings. A gas detector tube was also used for instantaneous sampling. In most workplaces, the personal exposure levels of EO were below the detection limit

Hajime Hori; Katsuya Yahata; Kazuya Fujishiro; Koji Yoshizumi; Ding Li; Yoshiaki Goto; Toshiaki Higashi

2002-01-01

52

Plasma Sterilization of Poly Lactic Acid Ultrasound Contrast Agents: Surface Modification and Implications for Drug Delivery  

PubMed Central

Poly lactic acid (PLA) ultrasound contrast agents (CA) have been previously developed in our laboratory for ultrasound (US) imaging, as well as surface coated with doxorubicin to create a potential targeted platform of chemotherapeutic delivery using focused US. However, we have previously found it impossible to sterilize these agents while at the same time maintaining their acoustic properties, a task that would probably require fabrication within a clean facility. The purpose of this paper is to investigate the feasibility of using plasma to sterilize these CA while maintaining maximum echogenicity, a step that would greatly facilitate in vivo investigations. Effects of plasma exposure time (1, 3 and 6 minutes) and intensity (low- 10 mA, 6.8 W; medium- 15 mA, 10.5 W; and high- 25 mA, 18W) on the CA’s acoustic properties, surface morphology, zeta potential, capacity to carry chemotherapeutics, and overall sterility are described. Both increases in plasma intensity and exposure time increased CA zeta potential and also significantly increased drug payload. High intensity plasma exposure for three minutes was found to be an optimal sterilization protocol for maximal (100%) preservation of CA echogenicity. Plasma exposure resulted in sterile samples and maintained original CA enhancement of 20 dB and acoustic half-life over 75 minutes, while increasing CA zeta potential by 11 mV and doxorubicin loading efficiency by 10%. This study not only shows how a highly temperature and pressure sensitive agent can be sterilized using plasma, but also that surface modification can be used to increase surface binding of drug. PMID:19766380

Eisenbrey, John R.; Hsu, Jennifer; Wheatley, Margaret A.

2013-01-01

53

Personal exposure level and environmental ethylene oxide gas concentration in sterilization facilities of hospitals in Japan.  

PubMed

Personal and environmental (stationary) ethylene oxide (EO) gas concentrations in gas sterilization facilities were measured at six workplaces in five hospitals. An ethylene oxide gas monitor (3M #3551) was used for both personal and stationary samplings. A gas detector tube was also used for instantaneous sampling. In most workplaces, the personal exposure levels of EO were below the detection limit of the gas monitor. Most of the time-weighted average (TWA) concentrations by the stationary sampling were below the threshold limit value of EO (TLV-TWA = 1 ppm), but in one workplace, more than 4 ppm of EO were detected in front of the sterilizer in a clean room during a 24-hour measurement, although all the personal exposure levels were below the detection limit. Method of aeration after the sterilization was very important for reducing the EO exposure. The EO gas concentrations in two workplaces where sufficient aeration was carried out were below the detection limit in all the stationary samples. In one workplace where insufficient aeration was performed, EO was detected from 16 of 17 stationary samples, and more than 90-200 ppm of EO was determined by the gas detector tube near the worker's face at the moment when the door of the sterilizer was opened and the sterilized materials were removed. PMID:12216593

Hori, Hajime; Yahata, Katsuya; Fujishiro, Kazuya; Yoshizumi, Koji; Li, Ding; Goto, Yoshiaki; Higashi, Toshiaki

2002-09-01

54

Sterilization of Materials with a One Atmosphere Uniform Glow Discharge Plasma.*  

NASA Astrophysics Data System (ADS)

The relatively recent development of the One Atmosphere Uniform Glow Discharge Plasma sterilization technique at the UTK Plasma Science Laboratory has produced initial results which indicate that the technique may have commercial potential. We have shown that active species in a OAUGDP can be applied to the sterilization of fabrics, films, solid materials, and microbiological culture media. With a OAUGDP, we can eliminate the vacuum system which enforces batch processing and requires a continuous input of electrical power. With a OAUGDP, the exposure time is as little as 15 seconds. Sterilization of microorganisms with a kill ratio of 10E6 or higher, can be achieved with minimal unwanted byproducts and at less expense, compared to such conventional sterilization methods as autoclaving, ethylene oxide, or low pressure plasma treatment. This paper discusses the sterilization mechanisms of this new technique, and compares its advantages and disadvantages with other widely used techniques. ^1 Department of Microbiology, UTK ^2 UTK Textiles and Nonwovens Development Center (TANDEC) Research supported in part by the UTK Textiles and Nonwovens Development Center and UTK Center for Materials Processing.

Ku, Yongmin; Brickman, C.; Tosh, K.; Kelly-Wintenberg, K.; Montie, T. C.; Tsai, P.; Wadsworth, L.; Roth, J. Reece

1996-11-01

55

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

SciTech Connect

A nonequilibrium Ar/O{sub 2} plasma discharge at atmospheric pressure was carried out in a coaxial cylindrical reactor with a stepped electrode configuration powered by a 13.56 MHz 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/O{sub 2} plasma jet at an exposure distance of 0.5-1.5 cm ranges from 5 to 57 s. 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 [Department of Molecular Science and Technology, Ajou University, San 5 Wonchon-Dong, Youngtong-Gu, Suwon 443-749 (Korea, Republic of); State Key Laboratory of Materials Modification by Laser, Ion and Electron Beams Department of Physics, Dalian University of Technology, Dalian 116024 (China)

2007-09-15

56

Comparative sterilization effectiveness of plasma in O2-H2O2 mixtures and ethylene oxide treatment.  

PubMed

We investigated the influence of variable parameters of plasma sterilization and compared its effectiveness with that of ethylene oxide using a reactive ion etching plasma reactor at 13.56 MHz. Gases tested were pure oxygen and oxygen-hydrogen peroxide mixtures in 190/10, 180/20, and 160/40 sccm ratios with constant gas flow at 200 sccm, pressure at 0.100 torr, radio-frequency power at 25 W, 50 W, 100 W, and 150 W, and temperature below 60 degrees C. Ethylene oxide sterilization was performed using 450 mg/L at 55 degrees C, 60% humidity, and -0.65 and 0.60 kgf/cm2 pressure. The biological indicator was Bacillus atrophaeus ATCC 9372, with exposure times of 3 to 120 min. Observed D values were 215.91, 55.55, 9.19, and 2.98 min for pure oxygen plasma at 25 W, 50 W, 100 W, and 150 W, respectively. Oxygen-hydrogen peroxide plasma produced D values of 6.41 min (190/10), 6.47 min (180/20), and 4.02 min (160/40) at 100 W and 1.47 min (190/10), 3.11 min (180/20), and 1.94 min (160/40) at 150 W. Ethylene oxide processes resulted in a D value of 2.86 min. Scanning electron microscopy analyses showed damage to the spore cortex. PMID:17722487

Silva, J M F; Moreira, A J; Oliveira, D C; Bonato, C B; Mansano, R D; Pinto, T J A

2007-01-01

57

Effects of oxygen radicals in low-pressure surface-wave plasma on sterilization  

SciTech Connect

The effects of oxygen radicals on sterilization were studied using a 2.45 GHz surface-wave oxygen plasma. A population of 1.5x10{sup 6} Bacillus stearothermophilus spores was irradiated for 3 min or more with oxygen plasma, generated at pressures between 6 and 14 Pa. The decimal reduction value (D value), a measure of the effectiveness of sterilization, was determined to be about 15-25 s. Using only oxygen radicals, excluding all charged particles, the 1.5x10{sup 6} spores were sterilized with a D value of 30-45 s after 5 min or more of irradiation. On scanning electron microscopy, the length and width of the spores changed significantly due to chemical etching by oxygen radicals.

Nagatsu, Masaaki; Terashita, Fumie; Nonaka, Hiroyuki; Xu, Lei; Nagata, Toshi; Koide, Yukio [Graduate School of Science and Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561 (Japan); Graduate School of Electronic Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561 (Japan); Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192 (Japan)

2005-05-23

58

Effects of oxygen radicals in low-pressure surface-wave plasma on sterilization  

NASA Astrophysics Data System (ADS)

The effects of oxygen radicals on sterilization were studied using a 2.45GHz surface-wave oxygen plasma. A population of 1.5×106 Bacillus stearothermophilus spores was irradiated for 3min or more with oxygen plasma, generated at pressures between 6 and 14Pa. The decimal reduction value (D value), a measure of the effectiveness of sterilization, was determined to be about 15-25s. Using only oxygen radicals, excluding all charged particles, the 1.5×106 spores were sterilized with a D value of 30-45s after 5min or more of irradiation. On scanning electron microscopy, the length and width of the spores changed significantly due to chemical etching by oxygen radicals.

Nagatsu, Masaaki; Terashita, Fumie; Nonaka, Hiroyuki; Xu, Lei; Nagata, Toshi; Koide, Yukio

2005-05-01

59

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

2015-01-07

60

Plasma phenomena in gas discharges  

Microsoft Academic Search

Basic concepts of discharges and plasmas are examined, taking into account the motion of a charged particle in a gas, the inclusion of the effects of inelastic collisions, the motion of charged particles in a magnetic field, the motion of an electron gas, Boltzmann's equation, and plasma variables in terms of the distribution functions. The positive column is considered along

R. N. Franklin

1976-01-01

61

A gas monitoring system for ethylene oxide sterilizers with constant sample flow through a microwave cavity spectrometer.  

PubMed

This paper reports a measurement system for monitoring the gas concentrations of ethylene oxide (EO) within sterilizers. It samples gas from the sterilizer chamber at a constant flow into a microwave cavity spectrometer. The pressure in the cavity of the spectrometer is linearly proportional to that in the sterilizer chamber, hence the partial pressure (i.e. gas concentration) of the EO gas is linearly proportional to that in the chamber. Measurement of the gas concentration in the chamber can therefore take place without the need to monitor and interpret the chamber pressure. As a consequence the reliability of the sterilization process may be improved, thus enabling a reduction in the in-chamber concentration of EO during sterilization and, hence, EO residues. The microwave cavity spectrometer operates under conditions of power saturation, and there is a good linear correlation between the output signal and the concentration of EO in the gas cell (to within a standard error of 4%). PMID:8295225

Zhu, Z; Gibson, C; Samuel, A H; Matthews, L P

1993-01-01

62

Characterization of stationary and pulsed inductively coupled RF discharges for plasma sterilization  

NASA Astrophysics Data System (ADS)

Sterilization of bio-medical materials using radio frequency (RF) excited inductively coupled plasmas (ICPs) has been investigated. A double ICP has been developed and studied for homogenous treatment of three-dimensional objects. Sterilization is achieved through a combination of ultraviolet light, ion bombardment and radical treatment. For temperature sensitive materials, the process temperature is a crucial parameter. Pulsing of the plasma reduces the time average heat strain and also provides additional control of the various sterilization mechanisms. Certain aspects of pulsed plasmas are, however, not yet fully understood. Phase resolved optical emission spectroscopy and time resolved ion energy analysis illustrate that a pulsed ICP ignites capacitively before reaching a stable inductive mode. Time resolved investigations of the post-discharge, after switching off the RF power, show that the plasma boundary sheath in front of a substrate does not fully collapse for the case of hydrogen discharges. This is explained by electron heating through super-elastic collisions with vibrationally excited hydrogen molecules.

Gans, T.; Osiac, M.; O'Connell, D.; Kadetov, V. A.; Czarnetzki, U.; Schwarz-Selinger, T.; Halfmann, H.; Awakowicz, P.

2005-05-01

63

New sterilization technologies alternative to ethylene oxide  

Microsoft Academic Search

Sterilization of biomedical devices may induce bulk and surface modification, responsible for the decrease or loss of their biofunctionality. Pure ethylene oxide (EO) at low temperature and new alternative techniques such as cold gas plasma sterilization have been developed for heat-sensitive polymers. There is a lack of the knowledge concerning their safety in terms of materials damage and consequences on

Maryam Tabrizian; Sophie Lerouge; Anne Debrie; L'hocine Yahia

1997-01-01

64

[The stability of biological indicators used for monitoring ethylene oxide gas sterilization].  

PubMed

It was found the correlation between the storage time of biological indicators and their usefulness for monitoring of gas sterilization with ethylene oxide (EO). Bacillus subtilis var niger ATTC 9372 was used as a test organism. Two kinds of investigations were done: observation of bacterial growing or lack of growing after 1 hour exposition of storage tests in EO (EO concentration- 750 mg/l, temperature +/- 50 degrees C, (humidity-40%) and examination of drop in number of spores on strip tests after storage time. The results show that sterilization efficacy may be monitored using such spore strip tests up to six months of storage. PMID:7777783

Jakimiak, B; Bielicka, A

1994-01-01

65

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

66

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, Jürgen; Morfill, Gregor E.; Schmidt, Hans-Ulrich

2012-01-01

67

Discharge conditions for CW and pulse-modulated surface-wave plasmas in low-temperature sterilization  

NASA Astrophysics Data System (ADS)

The discharge conditions required for low-temperature plasma sterilization were investigated using low-pressure surface-wave plasma (SWP). The discharge conditions for both continuous wave (CW) and pulse-modulated SWPs in low-temperature sterilization of Geobacillus stearothermophilus with a population of 1.5 × 106 and 3.0 × 106 were studied by varying the microwave input power from 500 W to 3 kW, and the effective plasma treatment time from 40 to 300 s. Results showed that sterilization was possible in a shorter treatment time using a higher microwave power for both CW and pulse-modulated SWPs. Pulse-modulated SWPs gave effective sterilization at a temperature roughly 10 to 20 °C below that of CW SWPs under the same average microwave power.

Xu, L.; Terashita, F.; Nonaka, H.; Ogino, A.; Nagata, T.; Koide, Y.; Nanko, S.; Kurawaki, I.; Nagatsu, M.

2006-01-01

68

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

69

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

70

Impact of Chlorine Dioxide Gas Sterilization on Nosocomial Organism Viability in a Hospital Room  

PubMed Central

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.

2013-01-01

71

Safety of plasma-based sterilization: surface modifications of polymeric medical devices induced by Sterrad and Plazlyte processes.  

PubMed

Plasma-based sterilization is a promising alternative to the use of pure ethylene oxide (EO), for low-temperature clinical sterilization of medical instruments and devices. However, few studies have been published that evaluate its safety in terms of possible damage to materials, particularly polymers. The objective of this work was to evaluate polymer surface modifications induced by commercial plasma-based sterilizers, in comparison with pure EO: Samples from 5 polymer-based devices were subjected to 1, 5, and 10 sterilization cycles by Sterrad-100, Plazlyte, and pure EO. Surface analysis was carried out by X-ray photoelectron spectroscopy (XPS), dynamic contact angle measurements (DCA), and scanning electron microscopy (SEM). Surface oxidation and wettability changes were observed on all samples sterilized by plasma-based techniques, the degree of modifications depending on the sterilizer (Sterrad, Plazlyte) and the type of polymer. Drastic changes of surface appearance were also observed by SEM on PVC samples sterilized by Plazlyte and by pure EO. Possible repercussions on safety are discussed. PMID:11847405

Lerouge, S; Tabrizian, M; Wertheimer, M R; Marchand, R; Yahia, L'H

2002-01-01

72

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

73

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

74

Plasma-based sterilization: effect on surface and bulk properties and hydrolytic stability of reprocessed polyurethane electrophysiology catheters.  

PubMed

Plasma-based sterilization is a promising alternative to ethylene oxide (EO) for reprocessing of electrophysiology catheters. To assess its safety in terms of material damage, modifications of surface and bulk properties as well as hydrolytic stability of sterilized catheters were evaluated. Polyurethane (PU) single-use electrophysiology catheters were subjected to one, five, and ten sterilization cycles by Sterrad-100S and Plazlyte, as well as by pure EO for comparison. Surface analysis techniques (ATR-FTIR, XPS, DCA) showed oxidation limited to the near-surface layer induced by both plasma-based sterilizers, whereas EO induced slight but deeper alkylation. Using bulk analysis techniques (RP-HPLC, SEC), oligomer alteration was observed after all three sterilization techniques, without modification of molecular weights. Hydrolytic stability of catheters was slightly changed by plasma-based sterilization, with a small increase in released oligomers. Finally, although Plazlyte and Sterrad are both plasma-based techniques, they induced different impacts on catheters, such as the degradation of an additive with Sterrad, and a clear difference in coloration with Plazlyte. PMID:11033561

Lerouge, S; Guignot, C; Tabrizian, M; Ferrier, D; Yagoubi, N; Yahia, L

2000-12-15

75

Headspace gas chromatographic analysis for the determination of traces of ethylene oxide in sterilized materials  

Microsoft Academic Search

Summary  A headspace gas chromatographic method for determination of traces of ethylene oxide (EO) in sterilized materials has been\\u000a developed. The method allows the determination of the amount of EO by putting the samples directly into acetonitrile and analysing\\u000a by means of headspace GC.\\u000a \\u000a The procedure described is simple, sensitive, reproducible and linear. The lower limit of detection is 0.015 ?g\\/g

M. V. Russo

1989-01-01

76

Acid etching and plasma sterilization fail to improve osseointegration of grit blasted titanium implants.  

PubMed

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

Saksø, Mikkel; Jakobsen, Stig S; Saksø, Henrik; Baas, Jørgen; Jakobsen, Thomas; Søballe, Kjeld

2012-01-01

77

Ethylene oxide gas sterilization: a simple technique for storing explanted skull bone. Technical note.  

PubMed

The authors evaluated the effectiveness of a simple technique using ethylene oxide (EtO) gas sterilization and room temperature storage of autologous bone grafts for reconstructive cranioplasty following decompressive craniectomy. The authors retrospectively analyzed data in 103 consecutive patients who underwent cranioplasty following decompressive craniectomy for any cause at the University of Illinois at Chicago between 1999 and 2005. Patients with a pre-existing intracranial infection prior to craniectomy or lost to follow-up before reconstruction were excluded. Autologous bone grafts were cleansed of soft tissue, hermetically sealed in sterilization pouches for EtO gas sterilization, and stored at room temperature until reconstructive cranioplasty was performed. Cranioplasties were performed an average of 4 months after decompressive craniectomy, and the follow-up after reconstruction averaged 14 months. Excellent aesthetic and functional results after single-stage reconstruction were achieved in 95 patients (92.2%) as confirmed on computed tomography. An infection of the bone flap occurred in eight patients (7.8%), and the skull defects were eventually reconstructed using polymethylmethacrylate with satisfactory results. The mean preservation interval was 3.8 months in patients with uninfected flaps and 6.4 months in those with infected flaps (p = 0.02). A preservation time beyond 10 months was associated with a significantly increased risk of flap infection postcranioplasty (odds ratio [OR] 10.8, p = 0.02). Additionally, patients who had undergone multiple craniotomies demonstrated a trend toward increased infection rates (OR 3.0, p = 0.13). Data in this analysis support the effectiveness of this method, which can be performed at any institution that provides EtO gas sterilization services. The findings also suggest that bone flaps preserved beyond 10 months using this technique should be discarded or resterilized prior to reconstruction. PMID:17695404

Jho, David H; Neckrysh, Sergey; Hardman, Julian; Charbel, Fady T; Amin-Hanjani, Sepideh

2007-08-01

78

Effect of Gas Flow on RF Plasmas  

Microsoft Academic Search

Effects of gas flow on rf plasmas between parallel plates under plasma processing conditions are investigated using a Monte Carlo simulation (MCS) and a fluid model calculation. It has shown that the gas flow changes the ion density distribution in the bulk region of the rf plasma where the velocity of gas flow is faster than that of the ion

Nobuyasu Shida; Yutaka Shida

1999-01-01

79

New sterilization technologies alternative to ethylene oxide  

NASA Astrophysics Data System (ADS)

Sterilization of biomedical devices may induce bulk and surface modification, responsible for the decrease or loss of their biofunctionality. Pure ethylene oxide (EO) at low temperature and new alternative techniques such as cold gas plasma sterilization have been developed for heat-sensitive polymers. There is a lack of the knowledge concerning their safety in terms of materials damage and consequences on the biofunctionality of sterilized devices. The objective of our work consists in studying bulk and surface changes in biomedical devices induced by these two sterilization techniques. Samples from PVC, Polyurethane, Polyacrylate and Polyethylene-based medical devices are subjected to 1, 5, and 10 sterilization cycles by Steri-Vac-3M (pure EO), Sterrad-100$TM, J&J (gas plasma + H2O2), and studied by X-rays photoelectron spectroscopy. Preliminary results show an increasing in Oxygen/Carbon ratio by a factor of 1.3 to 4.4 between the first and tenth cycle indicating the surface oxidation by gas plasma sterilization processes. Some changes in C-C chemical bounding are associated with EO sterilization.

Tabrizian, Maryam; Lerouge, Sophie; Debrie, Anne; Yahia, L'Hocine

1997-06-01

80

Analysis of emission data from O2 plasmas used for microbe sterilization  

NASA Astrophysics Data System (ADS)

In order to study the sterilization capabilities of radio frequency driven low pressure oxygen plasmas, the radiative emission was recorded at various pressures and input powers. A distinct transition from the bright mode (primarily inductively coupled) to a dim mode (primarily capacitively coupled) was observed as the pressure was increased and/or the power decreased. The data was further analyzed to estimate the electron temperature, rotational and vibrational temperatures, and various species concentrations. Based on the diffusion and rovibrational relaxation times, it is concluded that the rotational temperatures can be assumed to be in equilibrium with the translational temperature. The ions are produced "hot" and have little time to get equilibrated with the translational temperature. It is further determined that in the bright mode, which is more effective in microbe sterilization, the translational/rotational temperatures are in the 650-850 K range, the electron temperatures are low (3.5-4.5 eV), and the concentrations of atomic O and atomic metastables are at 1 order of magnitude higher than in the dim mode.

Sharma, S. P.; Cruden, B. A.; Rao, M. V. V. S.; Bolshakov, A. A.

2004-04-01

81

Plasma sterilization of polyethylene terephthalate bottles by pulsed corona discharge at atmospheric pressure.  

PubMed

A pulsed power supply was used to generate a corona discharge on a polyethylene terephthalate bottle, to conduct plasma sterilization at atmospheric pressure. Before generating such a discharge, minute quantities of water were attached to the inner surface of the bottle and to the surface of a high voltage (HV) electrode inserted into the bottle. Next, high-voltage pulses of electricity were discharged between electrodes for 6.0s, while rotating the bottle. The resulting spore log reduction values of Bacillus subtilis and Aspergillus niger on the inner surface of the bottle were 5.5 and 6 or higher, respectively, and those on the HV electrode surface were each 6 or higher for both strains. The presence of the by-products gaseous ozone, hydrogen peroxide, and nitric ions resulting from the electrical discharge was confirmed. PMID:17629247

Masaoka, Satoshi

2007-06-01

82

Gas discharge plasmas and their applications  

Microsoft Academic Search

This paper attempts to give an overview of gas discharge plasmas in a broad perspective. It is meant for plasma spectroscopists who are familiar with analytical plasmas (glow discharges, ICPs and microwave discharges), but who are not so well aware of other applications of these and related plasmas. In the first part, an overview will be given of the various

Annemie Bogaerts; Erik Neyts; Renaat Gijbels; Joost van der Mullen

2002-01-01

83

Poly(ethylene glycol)–poly( l-lactide) diblock copolymer prevents aggregation of poly( l-lactide) microspheres during ethylene oxide gas sterilization  

Microsoft Academic Search

Sterilization procedure is one of the most important obstacles in the clinical applications of biodegradable microspheres. The microspheres prepared with poly(?-hydroxy acid) were severely aggregated during ethylene oxide (EO) gas sterilization, and could not be used in clinical applications. In this study, the effects of EO gas sterilization on the poly(l-lactide) (PLLA) microspheres were analyzed by nuclear magnetic resonance spectroscopy

Yongdoo Choi; Sang Yoon Kim; Myeong-Hee Moon; Sun Hee Kim; Kwang-Sun Lee; Youngro Byun

2001-01-01

84

Effect of Gas Flow on RF Plasmas  

Microsoft Academic Search

A Monte Carlo simulation (MCS) technique has been used for investigating effects of gas flow on the characteristic of rf plasmas sustained between parallel plates under a plasma processing condition. In this MCS, for neutral atoms and molecules, a Maxwelliam velocity distribution modified by gas flow is assumed. A typical one dimension spatial variation of the electric field averaged over

N. Sato; Y. Shida

1998-01-01

85

Gas-discharge plasma sources for nonlocal plasma technology  

SciTech Connect

Nonlocal plasma technology is based on the effect of self-trapping of fast electrons in the plasma volume [V. I. Demidov, C. A. DeJoseph, Jr., and A. A. Kudryavtsev, Phys. Rev. Lett. 95, 215002 (2006)]. This effect can be achieved by changing the ratio of fast electron flux to ion flux incident on the plasma boundaries. This in turn leads to a significant change in plasma properties and therefore can be useful for technological applications. A gas-discharge device which demonstrates control of the plasma properties by this method is described.

Demidov, V. I.; DeJoseph, C. A. Jr.; Simonov, V. Ya. [UES, Inc., Dayton-Xenia Rd., Beavercreek, Ohio 45432 (United States); Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433 (United States); St. Petersburg Mining Technical University, St. Petersburg 199026 (Russian Federation)

2007-11-12

86

[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

87

Application of Plasma on Reentry Vehicle Communication and Interplanetary Spacecraft Sterilization  

NASA Astrophysics Data System (ADS)

In order to gain a better understanding of the reactions occurring during reentry at the gas-surface interface, a reactive ion etch (RIE) plasma device was augmented to more accurately represent how material may paralyze in the presence of plasma. The device inflow was augmented to include a nitrogen line, and the outflow augmented to allow chemical analysis. A nichrome resistor heater was added to raise sample temperatures to pyrolysis levels. Cryo-focusing was performed on pyrolysis gases in order to test the ability to quantify compounds released during heating. This was done using liquid nitrogen prior to compounds entering the gas chromatography column. The nitrogen line also allowed initial study into the use of the RIE machine for planetary protection experiments due to the biocidal properties of Nitrogen/Oxygen plasma. This included static build-up experiments on equipment sensitive to electrostatic discharge. Experiments were also carried out using George Washington University's Vacuum Arc Thruster (VAT). The VAT was used in an attempt to catalyze spallation from a silicon phenolic thermal protection system material (TPS).

Fenstermacher, Jarrod J.

88

Postpartum Sterilization  

MedlinePLUS

... of a baby. What is the most common method of postpartum sterilization? The method used most often ... is postpartum sterilization? • What is the most common method of postpartum sterilization? • When is postpartum sterilization performed? • ...

89

Poly(ethylene glycol)-poly(L-lactide) diblock copolymer prevents aggregation of poly(L-lactide) microspheres during ethylene oxide gas sterilization.  

PubMed

Sterilization procedure is one of the most important obstacles in the clinical applications of biodegradable microspheres. The microspheres prepared with poly(alpha-hydroxy acid) were severely aggregated during ethylene oxide (EO) gas sterilization, and could not be used in clinical applications. In this study, the effects of EO gas sterilization on the poly(L-lactide) (PLLA) microspheres were analyzed by nuclear magnetic resonance spectroscopy (1H-NMR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), scanning electron microscope (SEM) and size fractionation. The aggregation between the microspheres might be stimulated by high mobility of amorphous regions of PLLA on the microsphere surfaces since both water vapor and gas mixture can reduce glass transition temperature (Tg) of PLLA below the sterilization temperature. During EO gas sterilization, there were no changes in the molecular structure and the molecular weight of PLLA in microspheres, but there were changes in the crystallinity of PLLA in microspheres. In this study, poly(L-lactide)-poly(ethylene glycol) diblock copolymers (PLE) were blended with PLLA homopolymers in various ratios to design the microsphere suitable for EO gas sterilization. Aggregation of PLLA microspheres was markedly prevented when more than 4wt% of PLE was blended in the microspheres. This inhibition effect on aggregation may be due to the increased initial crystallinity of the microspheres, which help to maintain the microsphere morphology during EO gas sterilization. PMID:11311019

Choi, Y; Kim, S Y; Moon, M H; Kim, S H; Lee, K S; Byun, Y

2001-05-01

90

Laser and radiofrequency tailored gas plasma sources  

Microsoft Academic Search

Summary form only given. We are carrying out plasma source research utilizing vacuum ultraviolet excimer laser ionization of an organic gas and microwave scattering and fast Langmuir probe measurements of the plasma formation and decay. We find that peak plasma densities of 2×1013\\/cm3 in 5 cm×10 cm×20 cm volumes can be created with a 300 mJ, 20 ns pulse of

J. Scharer; M. Bettenhausen; G. Ding; H. Gui; X. Guo; K. Kelly; Y. Mouzouris

1998-01-01

91

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

92

Cold atmospheric pressure gas plasma enhances the wear performance of ultra-high molecular weight polyethylene.  

PubMed

Ultra-high molecular weight polyethylene (UHMWPE) is frequently employed in joint replacements because of its high biocompatibility; however, this material does not exhibit particularly strong wear performance, thus potentially reducing the longevity of such devices. Numerous techniques have been investigated to increase the resistance to wear of UHMWPE, but they are all based on expensive machinery and require a high level of safety precautions. Cold atmospheric pressure gas plasma treatment is an inexpensive process that has been used as a surface modification method and as a sterilization technique. We demonstrate for the first time that a helium/oxygen cold atmospheric pressure gas plasma can be used to enhance the wear performance of UHMWPE without affecting the cytocompatibility of the material. The exposure to a cold atmospheric pressure gas plasma results in a greater level of crosslinking of the polyethylene chains. As a consequence of the higher crosslinking, the material stiffness of the treated surface is increased. PMID:22202910

Perni, Stefano; Kong, Michael G; Prokopovich, Polina

2012-03-01

93

Effects of the Nd:YAG dental laser on plasma-sprayed and hydroxyapatite-coated titanium dental implants: surface alteration and attempted sterilization.  

PubMed

The Nd:YAG dental laser has been recommended for a number of applications, including the decontamination or sterilization of surfaces of dental implants that are diseased or failing. The effects of laser irradiation in vitro (1) on the surface properties of plasma-sprayed titanium and plasma-sprayed hydroxyapatite-coated titanium dental implants, and (2) on the potential to sterilize those surfaces after contamination with spores of Bacillus subtilis have been examined. Surface effects were examined by scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction after laser irradiation at 0.3, 2.0, and 3.0 W using either contact or noncontact handpieces. Controls received no laser irradiation. Melting, loss of porosity, and other surface alterations were observed on both types of implants, even with the lowest power setting. For the sterilization study, both types of implants were first sterilized by exposure to ethylene oxide and then contaminated with spores of B subtilis. After laser irradiation, the implants were transferred to sterile growth medium and incubated. Laser irradiation did not sterilize either type of implant. The spore-contaminated implants in the control group were successfully sterilized with ethylene oxide. PMID:1299639

Block, C M; Mayo, J A; Evans, G H

1992-01-01

94

Effects of ethylene oxide gas sterilization on physical properties of poly(L-lactide)-poly(ethylene glycol)-poly(L-lactide) microspheres.  

PubMed

The aggregation of poly(alpha-hydroxy acid) microspheres during ethylene oxide (EO) gas sterilization makes it difficult for the microspheres to be used in clinical applications. In this study, six kinds of PLLA-PEG-PLLA triblock copolymers (TriPLE) were synthesized with various composition ratios of PEG/PLLA in the range of 0.012 to 0.103. TriPLE microspheres were prepared by the oil-in-water emulsion method. TriPLE microspheres were characterized by using 1H-NMR, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). After sterilization by EO gas at 55 degrees C, the microspheres were analyzed by scanning electron microscope (SEM), laser diffractometry, standard sieves, X-ray diffraction (XRD), GPC, and DSC. When the composition ratio of PEG/PLLA was above 0.02, the initial crystallinity of TriPLE in microspheres was as high as 50%, and the microspheres were suitable to be sterilized by EO gas. On the other hand, TriPLE microspheres, which had composition ratios of PEG/PLLA below 0.02, had low initial crystallinities of about 30%, and aggregated during EO gas sterilization. For these microspheres, crystallinity increased up to 50% during the sterilization, whereas other TriPLE microspheres did not show any changes in crystallinity. Therefore, the aggregation of TriPLE microspheres during EO gas sterilization was markedly reduced as the initial crystallinity of TriPLE in the microspheres was increased. PMID:11587041

Ah, Y C; Choi, Y; Kim, S Y; Kim, S H; Lee, K S; Byun, Y

2001-01-01

95

Effects of low temperature hydrogen peroxide gas on sterilization and cytocompatibility of porous poly( d, l-lactic- co-glycolic acid) scaffolds  

Microsoft Academic Search

Biodegradable poly(d,l-lactic-co-glycolic acid) (PLGA) has been widely used as a scaffold in tissue engineering due to its excellent biocompatibility. However, PLGA scaffolds become structurally deformed during the sterilization process since they were hydrolytically unstable. In this study, the effects of hydrogen peroxide gas (HPG) were investigated on the deformation, sterilization and cytocompatibility of porous PLGA scaffolds and compared with those

Mi Hee Lee; Hye-Lee Kim; Chang Hwa Kim; Sun Ho Lee; Jeong Koo Kim; Seung Jin Lee; Jong-Chul Park

2008-01-01

96

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

97

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

2011-12-01

98

Effect of plasma-glow discharge as a sterilization of titanium surfaces.  

PubMed

In this study, in vitro osteoblast responses to glow-discharged, commercially pure titanium (Ti) surfaces were investigated. It was hypothesized that the glow-discharge treatment would be an effective sterilization procedure for Ti implantations before implantation. The Ti surfaces were prepared by grinding to 600 grits followed by cleaning. These were then divided into two groups, with one group being the control and the other group undergoing glow-discharge treatment using oxygen. Human embryonic palatal mesenchyme cells, an osteoblast precursor, were used to evaluate the cell responses to glow-discharged and control Ti surfaces. It was observed from this study that protein production and osteocalcin production on both surfaces exhibited no significant differences during the 10-day study. Similarly, no significant differences were observed for alkaline phosphatase (ALP) specific activity during the first 7 days of incubation. However, at day 10, the ALP specific activity for control Ti surfaces was significantly higher than the ALP activity for the glow-discharged surface. Overall, this study suggested that the use of glow discharge as an alternative sterilization procedure for medical and dental implants did not inhibit osteoblast phenotypic expression. PMID:12704957

Youngblood, T; Ong, J L

2003-01-01

99

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

100

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

101

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

102

Damage of office supply, personal use items, and over-the-counter medical devices after sterilization by ethylene oxide gas, electron beam, and gamma radiation.  

PubMed

After letters containing Bacillus anthracis spores entered the U.S. mail in 2001, a problem emerged regarding how to decontaminate the letters, packages, and personal items in offices that received these letters. The effects of three sterilization methods (i.e. ethylene oxide gas [EO], electron beam [e-beam] radiation, and gamma radiation) were evaluated for a variety of office supply and equipment, personal use items, and over-the-counter medical devices. No single sterilization method was suitable for all items that could be mailed or found in an office. Damage or discoloration was evident for some items by each sterilization method. There were changes in the color of certain items, such as some of the packaging material, some pacifiers, some of the fabrics, and the nylon stockings after e-beam and gamma radiation. Both e-beam and gamma radiation damaged all film samples. Following EO sterilization and normal aeration, there were a number of samples with high (above 250 microg/g) levels of EO and samples with detectable ethylene chlorohydrin levels. The data would suggest that certain items exposed to EO sterilization must be further aerated prior to use, or discarded. Generic descriptions of products (such as plastics) or grouping of items (such as condoms) were not sufficient to predict what is safe in terms of EO residual levels remaining on an item. Successful decontamination of a wide variety of items will require careful selection of different sterilization methods. PMID:15635999

Lucas, Anne D; Merritt, Katharine; Hitchins, Victoria M

2004-01-01

103

Sterile neutrinos?  

E-print Network

The notion of sterile neutrinos is discussed. The schemes of mixing of four massive neutrinos, which imply the existence of sterile neutrinos, are briefly considered. Several model independent methods that allow to reveal possible transitions of solar neutrinos into sterile states are presented.

S. M. Bilenky; C. Giunti

1999-05-05

104

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

105

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

106

Sterilization/disinfection using reduced-pressure plasmas: some differences between direct exposure of bacterial spores to a discharge and their exposure to a flowing afterglow  

NASA Astrophysics Data System (ADS)

The use of plasma for sterilization or disinfection offers a promising alternative to conventional steam or chemical approaches. Plasma can operate at temperatures less damaging to some heat-sensitive medical devices and, in contrast to chemicals, can be non-toxic and non-polluting for the operator and the environment, respectively. Direct exposure to the gaseous discharge (comprising an electric field and ions/electrons) or exposure to its afterglow (no E-field) can both be envisaged a priori, since these two methods can achieve sterility. However, important issues must be considered besides the sterility goal. Direct exposure to the discharge, although yielding a faster inactivation of microorganisms, is shown to be potentially more aggressive to materials and sometimes subjected to the shadowing effect that precludes the sterilization of complex-form items. These two drawbacks can be successfully minimized with an adequate flowing-afterglow exposure. Most importantly, the current paper shows that direct exposure to the discharge can lead to the dislodgment and release of viable microorganisms from their substratum. Such a phenomenon could be responsible for the recontamination of sterilized devices as well as possible contamination of the ambient surroundings, additionally yielding an erroneous over-appreciation of the inactivation efficiency. The operation of the N2-O2 flowing afterglow system being developed in our group is such that there are no ions and electrons left in the process chamber (late-afterglow regime) in full contrast with their presence in the discharge. The dislodgment and release of spores could be attributed, based on the literature, to their electrostatic charging by electrons, leading to an (outward) electrostatic stress that exceeds the adhesion of the spores on their substrate.

Moisan, M.; Levif, P.; Séguin, J.; Barbeau, J.

2014-07-01

107

Effect of surface roughness and sterilization on bacterial adherence to ultra-high molecular weight polyethylene.  

PubMed

Sterilization with ethylene oxide (EO) and gas plasma (GP) are well-known methods applied to ultra-high molecular weight polyethylene (UHMWPE) surfaces in the belief that they prevent major material changes caused by gamma irradiation. However, the influence of these surface sterilization methods on bacterial adherence to UHMWPE is unknown. UHMWPE samples with various degrees of roughness (0.3, 0.8 and 2.0 ?m) were sterilized with either GP or EO. The variations in hydrophobicity, surface free energy and surface functional groups were investigated before and after sterilization. Sterilized samples were incubated with either Staphylococcus aureus or Staphylococcus epidermidis in order to study bacterial adherence to these materials. Fewer bacteria adhered to UHMWPE after sterilization with EO than after sterilization with GP, especially to the smoothest surfaces. No changes in chemical composition of the UHMWPE surface due to sterilization were observed using X-ray photoemission spectroscopy analysis. The decreased bacterial adherence to UHMWPE found at the smoothest surfaces after sterilization with EO was not directly related to changes in chemical composition. Increased bacterial adherence to rougher surfaces was associated with increased polar surface energy of EO-sterilized surfaces. PMID:19889055

Kinnari, T J; Esteban, J; Zamora, N; Fernandez, R; López-Santos, C; Yubero, F; Mariscal, D; Puertolas, J A; Gomez-Barrena, E

2010-07-01

108

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

109

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

110

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

111

STW gas sensors using plasma-polymerized allylamine  

Microsoft Academic Search

Gas sensors generally consist of two major components: a gas recognition element which provides the specificity and selectivity of the measurement and a physical transducer which translates the gas absorption or desorption event into electronic signal. In this paper, plasma polymerized allylamine (PPAa) film is used as a gas recognition element and a surface transverse wave (STW) device is used

Hiromi Yatsuda; Makoto Nara; Takashi Kogai; Hidenobu Aizawa; Shigeru Kurosawa

2007-01-01

112

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

113

Relation between plasma plume density and gas flow velocity in atmospheric pressure plasma  

SciTech Connect

We have studied atmospheric pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying RF high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. To study the properties of the plasma plume, the plasma plume current is estimated from the difference in currents on the circuit, and the drift velocity is measured using a photodetector. The relation of the plasma plume density n{sub plu}, which is estimated from the current and the drift velocity, and the gas flow velocity v{sub gas} is examined. It is found that the dependence of the density on the gas flow velocity has relations of n{sub plu} ? log(v{sub gas}). However, the plasma plume density in the laminar flow is higher than that in the turbulent flow. Consequently, in the laminar flow, the density increases with increasing the gas flow velocity.

Yambe, Kiyoyuki; Taka, Shogo; Ogura, Kazuo [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan)] [Graduate School of Science and Technology, Niigata University, Niigata 950-2181 (Japan)

2014-04-15

114

Elimination of transmissible spongiform encephalopathy infectivity and decontamination of surgical instruments by using radio-frequency gas-plasma treatment.  

PubMed

It has now been established that transmissible spongiform encephalopathy (TSE) infectivity, which is highly resistant to conventional methods of deactivation, can be transmitted iatrogenically by contaminated stainless steel. It is important that new methods are evaluated for effective removal of protein residues from surgical instruments. Here, radio-frequency (RF) gas-plasma treatment was investigated as a method of removing both the protein debris and TSE infectivity. Stainless-steel spheres contaminated with the 263K strain of scrapie and a variety of used surgical instruments, which had been cleaned by a hospital sterile-services department, were examined both before and after treatment by RF gas plasma, using scanning electron microscopy and energy-dispersive X-ray spectroscopic analysis. Transmission of scrapie from the contaminated spheres was examined in hamsters by the peripheral route of infection. RF gas-plasma treatment effectively removed residual organic residues on reprocessed surgical instruments and gross contamination both from orthopaedic blades and from the experimentally contaminated spheres. In vivo testing showed that RF gas-plasma treatment of scrapie-infected spheres eliminated transmission of infectivity. The infectivity of the TSE agent adsorbed on metal spheres could be removed effectively by gas-plasma cleaning with argon/oxygen mixtures. This treatment can effectively remove 'stubborn' residual contamination on surgical instruments. PMID:16033987

Baxter, H C; Campbell, G A; Whittaker, A G; Jones, A C; Aitken, A; Simpson, A H; Casey, M; Bountiff, L; Gibbard, L; Baxter, R L

2005-08-01

115

Plasma catalytic hybrid processes: gas discharge initiation and plasma activation of catalytic processes  

Microsoft Academic Search

Catalytic reactions of a gas mixture can efficiently be induced by pre-treatment using a gas discharge plasma or by combined treatment in a plasma catalytic hybrid reactor. The effects of plasma treatment can be excitation of molecules, formation of short lived radicals, formation of long lived intermediate species, emission of UV-radiation, or simply gas heating.By dielectric barrier discharge (DBD) pre-treatment

Th. Hammer; Th. Kappes; M. Baldauf

2004-01-01

116

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

117

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

118

Effects of ethylene oxide gas sterilization on physical properties of poly(L-lactide)–poly(ethylene glycol)–poly(L-lactide) microspheres  

Microsoft Academic Search

The aggregation of poly(?-hydroxy acid) microspheres during ethylene oxide (EO) gas sterilization makes it difficult for the microspheres to be used in clinical applications. In this study, six kinds of PLLA-PEG-PLLA triblock copolymers (TriPLE) were synthesized with various composition ratios of PEG\\/PLLA in the range of 0.012 to 0.103. TriPLE microspheres were prepared by the oil-in-water emulsion method. TriPLE microspheres

Young Chang Ah; Yongdoo Choi; Sang Yoon Kim; Sun Hee Kim; Kwang-Sun Lee; Youngro Byun

2001-01-01

119

Damage of Office Supply, Personal Use Items, and Over-the-Counter Medical Devices After Sterilization by Ethylene Oxide Gas, Electron Beam, and Gamma Radiation  

Microsoft Academic Search

After letters containing Bacillus anthracis spores entered the U.S. mail in 2001, a problem emerged regarding how to decon- taminate the letters, packages, and personal items in offices that received these letters. The effects of three sterilization methods (i.e. ethylene oxide gas (EO), electron beam (e-beam) radiation, and gamma radiation) were evaluated for a variety of office sup- ply and

Anne D. Lucas; Katharine Merritt; Victoria M. Hitchins

120

Sterile technique  

MedlinePLUS

... kit) A clean, dry surface Clean paper towels Wash your hands well and keep all work surfaces ... To open a sterile pad or kit: Wash your hands with soap and running ... palms, fingers, and between your fingers thoroughly. Wash ...

121

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

122

A microfluidic chip for generating reactive plasma at gas–gas interface formed in laminar flow  

NASA Astrophysics Data System (ADS)

A gas–gas interface is used for generating a localized reactive plasma flow at an atmospheric pressure. A microfluidic chip is fabricated as the reactor integrating a small plasma source located upstream. Within a Y-shaped microchannel, a discharging gas flows with a chemical gas. Owing to the small width of the microchannel, the gas flow is stabilized in a laminar flow. The resultant gas–gas interface is formed in the area where two gases flow facing each other activating the chemical gas through the energetic species in the discharging gas. A characteristic stream pattern is observed as the etching profile of a carbon film with a sub-µm sharp step change that can be explained by the spatial distribution of the reactive oxygen. This etching profile is different from that obtained when plasma discharging occurs near the channel exit being affected by the turbulent flow.

Hashimoto, Masahiro; Tsukasaki, Katsuki; Kumagai, Shinya; Sasaki, Minoru

2015-01-01

123

Rare gas flow structuration in plasma jet experiments  

NASA Astrophysics Data System (ADS)

Modifications of rare gas flow by plasma generated with a plasma gun (PG) are evidenced through simultaneous time-resolved ICCD imaging and schlieren visualization. The geometrical features of the capillary inside which plasma propagates before in-air expansion, the pulse repetition rate and the presence of a metallic target are playing a key role on the rare gas flow at the outlet of the capillary when the plasma is switched on. In addition to the previously reported upstream offset of the laminar to turbulent transition, we document the reverse action leading to the generation of long plumes at moderate gas flow rates together with the channeling of helium flow under various discharge conditions. For higher gas flow rates, in the l min-1 range, time-resolved diagnostics performed during the first tens of ms after the PG is turned on, evidence that the plasma plume does not start expanding in a laminar neutral gas flow. Instead, plasma ignition leads to a gradual laminar-like flow build-up inside which the plasma plume is generated. The impact of such phenomena for gas delivery on targets mimicking biological samples is emphasized, as well as their consequences on the production and diagnostics of reactive species.

Robert, E.; Sarron, V.; Darny, T.; Riès, D.; Dozias, S.; Fontane, J.; Joly, L.; Pouvesle, J.-M.

2014-02-01

124

21 CFR 610.12 - Sterility.  

Code of Federal Regulations, 2013 CFR

...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. (2) A manufacturer is...

2013-04-01

125

21 CFR 610.12 - Sterility.  

Code of Federal Regulations, 2014 CFR

...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

126

High Pressure Gas Injection In Tokamak - Modeling Of Plasma Dynamics  

SciTech Connect

The model is suggested to describe dynamics of plasma parameters during high pressure gas injection. Model predicts fast decrease of electron and ion temperatures, electron beam generation, ion abundance and average ion charge, the rate of total radiation losses. It was found that the main reason for electron and ion temperature drop is energy exchange between target plasma and injected particles. Model can be used to optimize gas injection process.

Baronova, E. O.; Morozov, D. Kh.; Vikhrev, V. V. [RRC Kurchatov Institute, Moscow (Russian Federation)

2006-01-15

127

Pulse plasma carburizing and high pressure gas quenching -- Industrial applications  

SciTech Connect

Pulse plasma carburizing with high pressure gas quenching up to 20 bar is the newly developed case hardening process now available in production size equipment. The first part of results demonstrates the tremendous potential of high pressure gas quenching for successful hardening of case hardening steels. The second part opens a window to glance at the pulse plasma carburizing of complex shaped parts. Both processes improve economical data and performance of carburizing processes.

Preisser, F.; Schnatbaum, F. [ALD Vacuum Technologies GmbH, Erlensee (Germany)

1995-12-31

128

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

129

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

E-print Network

and temporal nonlocality between electron energy distribution and electromagnetic field in gas discharge is considered for gas discharge plasmas at nonequilibrium condition. Index Terms--Electron energy distribution function (EEDF), electron kinetics, gas discharge, nonequilibrium. I. INTRODUCTION PARTIALLY ionized gas

Kaganovich, Igor

130

Nonlocal electron kinetics in collisional gas discharge plasmas  

Microsoft Academic Search

Nonlocal phenomena in electron kinetics of collisional gas discharge plasmas, their kinetic treatment by a nonlocal approach, and relevant experimental results are reviewed in this paper. Using the traditional two-term approximation for the electron distribution function, a general method to analyze electron kinetics in nonuniform plasmas in DC and RF fields for atomic gases is presented for the nonlocal case,

Vladimir I. Kolobov; Valery A. Godyak

1995-01-01

131

[What should be the length and inner diameter of the testing device for microbiological efficacy testing of formaldehyde gas sterilization methods?].  

PubMed

The series of tests described in a preceding publication (Spicher and Borchers, 1983) has been continued in a modified way. This time, the dependency of the microbiological test results of a formaldehyde gas sterilization procedure on length and inner diameter of the tubes serving as test pieces was examined. The tubes were 1 or 2 m in length with an inner diameter of 1 or 2 mm. The tests were performed with four different preparations of bioindicators. Spores of Bac. stearothermophilus served as test germs. The preparations differed in the type of suspension used for the preparation of the bioindicators: distilled water, diluted blood (10%), undiluted blood, 10% albumin solution. The spore suspensions had been dried on linen thread. During the test procedure, the bioindicators were located near the sealed end of the tube. After completion of the sterilization procedure, the bioindicators were examined for viable germs. In tubes of identical length, the frequency of indicators carrying viable germs was always higher in those of 1 mm than in those of 2 mm inner diameter. In tubes of identical inner diameter, the frequency of indicators carrying viable germs in those of 2 m length was always higher than in those of 1 m length. This regularity was independent of the type of bioindicators used. The bioindicators for the preparation of which a 10% albumin solution had been employed showed the highest resistance. A somewhat lower resistance was found for the bioindicators prepared with undiluted blood. The bioindicators for which the spores had been suspended in diluted blood proved to have the lowest resistance. If the spores had been suspended in distilled water, the resistance of the bioindicators was a little lower than that of those suspended in undiluted blood, but was higher than that of the dried spores with diluted blood. The test results confirm the effectiveness of the method proposed earlier, i.e. to deposit the bioindicators in special test pieces (e.g. tubes or sounds) for the microbiological testing of formaldehyde gas sterilization procedures. These test pieces must be at least as long and as narrow as the longest and narrowest cavity of the object to be sterilized (tubes, catheters). In order to standardize the microbiological testing of formaldehyde gas sterilization procedures and to guarantee a certain minimum efficiency, the bioindicator as well as the test piece and its size (length and inner diameter) should be standardized.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:6524142

Spicher, G; Borchers, U

1984-10-01

132

ETHYLENE OXIDE CONTROL TECHNOLOGY DEVELOPMENT FOR HOSPITAL STERILIZERS  

EPA Science Inventory

The report discusses the development of ethylene oxide (EO) control technology for hospital sterilizers. Hospitals sterilize heat-sensitive items in gas sterilizers that use a mixture of EO (12 wt %) and a chlorofluorocarbon (CFC) (88 wt %). The active sterilizing agent is EO. Th...

133

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

134

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

135

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

136

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

137

Sterile connector.  

PubMed

Fabrication of a sterile connector for joining a supply source to an independent delivery location through a contaminated environment requires four design steps: 1) alignment of connector housings; 2) exclusion of the contaminated environment; 3) sterilization of the excluded region; and 4) penetration within the sterilized area followed by coupling of the protected internal conduits. Protective covers for connectors now in use may be modified to provide penetrable terminal barrier membranes that can be joined to exclude the environment. An adhesive containing an antimicrobiologic agent would set the stage for a controlled mechanical penetration of the decontaminated fused barriers. In another design concept, plastic barrier membranes without preliminary adhesions are simultaneously fused, sterilized, and penetrated by a nichrome wire heated to approximately 288 C. A system can be designed that is compatible, at the option of the user, with either of these methods. The more economical mechanical approach could then be used for parenteral fluid therapy while the nichrome wire technique would be reserved for more complex processing methods (frozen erythrocytes) or when storage of the resulting component is a factor. PMID:982541

Tenczar, F J

1976-01-01

138

Operation of Ferroelectric Plasma Sources in a Gas Discharge Mode  

SciTech Connect

Ferroelectric plasma sources in vacuum are known as sources of ablative plasma, formed due to surface discharge. In this paper, observations of a gas discharge mode of operation of the ferroelectric plasma sources (FPS) are reported. The gas discharge appears at pressures between approximately 20 and approximately 80 Torr. At pressures of 1-20 Torr, there is a transition from vacuum surface discharge to the gas discharge, when both modes coexist and the surface discharges sustain the gas discharge. At pressures between 20 and 80 Torr, the surface discharges are suppressed, and FPS operate in pure gas discharge mode, with the formation of almost uniform plasma along the entire surface of the ceramics between strips. The density of the expanding plasma is estimated to be about 1013 cm-3 at a distance of 5.5 mm from the surface. The power consumption of the discharge is comparatively low, making it useful for various applications. This paper also presents direct measurements of the yield of secondary electron emission from ferroelectric ceramics, which, at low energies of primary electrons, is high and dependent on the polarization of the ferroelectric material

A. Dunaevsky; N.J. Fisch

2004-03-08

139

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

140

Experimental study of gas-puff z-pinch plasma  

Microsoft Academic Search

A small neon gas-puff z-pinch device was constructed, and the plasma implosion and its radiation characteristics were studied experimentally. The plasma implosion was investigated using a three-frame Mach-Zehnder interferometer (TFMZI) that is capable of taking three pictures (5 ns exposure and 13 ns interpicture delay) within a single z-pinch shot. Thermopiles were also used in the experiments with the TFMZI

Xiaobing Zou; Xinxin Wang; Chengmu Luo; Min Han

2005-01-01

141

[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

142

System and method of applying energetic ions for sterilization  

DOEpatents

A method of sterilization of a container is provided whereby a cold plasma is caused to be disposed near a surface to be sterilized, and the cold plasma is then subjected to a pulsed voltage differential for producing energized ions in the plasma. Those energized ions then operate to achieve spore destruction on the surface to be sterilized. Further, a system for sterilization of a container which includes a conductive or non-conductive container, a cold plasma in proximity to the container, and a high voltage source for delivering a pulsed voltage differential between an electrode and the container and across the cold plasma, is provided.

Schmidt, John A.

2003-12-23

143

Plasma jet's shielding gas impact on bacterial inactivation.  

PubMed

One of the most desired aims in plasma medicine is to inactivate prokaryotic cells and leave eukaryotic cells unharmed or even stimulate proliferation to promote wound healing. The method of choice is to precisely control the plasma component composition. Here the authors investigate the inactivation of bacteria (Escherichia coli) by a plasma jet treatment. The reactive species composition created by the plasma in liquids is tuned by the use of a shielding gas device to achieve a reactive nitrogen species dominated condition or a reactive oxygen species dominated condition. A strong correlation between composition of the reactive components and the inactivation of the bacteria is observed. The authors compare the results to earlier investigations on eukaryotic cells and show that it is possible to find a plasma composition where bacterial inactivation is strongest and adverse effects on eukaryotic cells are minimized. PMID:25832438

Jablonowski, Helena; Hänsch, Mareike A Ch; Dünnbier, Mario; Wende, Kristian; Hammer, Malte U; Weltmann, Klaus-Dieter; Reuter, Stephan; Woedtke, Thomas von

2015-01-01

144

Ethylene oxide control technology development for hospital sterilizers. Final report for March 1986September 1987  

Microsoft Academic Search

The report discusses the development of ethylene oxide (EO) control technology for hospital sterilizers. Hospitals sterilize heat-sensitive items in gas sterilizers that use a mixture of EO (12 wt %) and a chlorofluorocarbon (CFC) (88 wt %). The active sterilizing agent is EO. The CFC is added as a flameproofing diluent. Two potential sterilizer emission-control systems were tested: catalytic oxidation

Meiners

1988-01-01

145

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

E-print Network

generate an elongated plasma waveguide by using a combination of an axicon and the ignitor-heater scheme. The ignitor-heater scheme consists of a short and a long laser pulses to produce and heat electrons nitrogen is used to cool the valve and gas reservoir of the gas jet to increase the local atom density

146

Gas laser with dual plasma mixing  

DOEpatents

A gas laser includes an enclosure forming a first chamber, a second chamber and a lasing chamber which communicates through a first opening to the first chamber and through a second opening to the second chamber. The lasing chamber has a pair of reflectors defining a Fabry-Perot cavity. Separate inlets enable different gases to be introduced into the first and second chambers. A first cathode within the first chamber is provided to produce positive ions which travel into the lasing chamber and a second cathode of a pin-hollow type within the second chamber is provided to produce negative ions which travel into the lasing chamber. A third inlet introduces a molecular gas into the lasing chamber, where the molecular gas becomes excited by the positive and negative ions and emits light which lases in the Fabry-Perot cavity. 2 figs.

Pinnaduwage, L.A.

1999-04-06

147

Plasma reforming and partial oxidation of hydrocarbon fuel vapor to produce synthesis gas and/or hydrogen gas  

DOEpatents

Methods and systems 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.; Detering, Brent A.

2003-08-19

148

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

149

Interaction of radiatively cooled plasma jets with static gas and collimated supersonic gas jets  

NASA Astrophysics Data System (ADS)

The MAGPIE generator (1.4 MA, 240 ns) drives an ablative plasma from a thin Al foil. The convergence of the plasma from the foil on its axis leads to the formation of a supersonic plasma jet, with a typical velocity of ˜100 km/s. Jet-ambient interactions are studied either by injecting a highly-collimated, supersonic, cold gas jet above the foil using a nozzle, or by enclosing the foil inside a cell filled with neutral, static gas. In both cases, the plasma jet creates several shock features in the ambient medium. Experimental results from varied ambient parameters such as gas pressure and composition are presented together with 3-D MHD simulations.

Suzuki-Vidal, F.; Lebedev, S. V.; Skidmore, J.; Bocchi, M.; Bland, S. N.; Burdiak, G.; Chittenden, J. P.; de Grouchy, P.; Hall, G. N.; Harvey-Thompson, A. J.; Khoory, E.; Pickworth, L. A.; Suttle, L.; Swadling, G. F.; Krishnan, M.; Madden, R. E.; Elliot, K. W.; Coleman, P. L.; Ciardi, A.

2011-11-01

150

Mathematical model of gas plasma applied to chronic wounds  

NASA Astrophysics Data System (ADS)

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.; Zhang, Y. T.

2013-11-01

151

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

152

Laser plasma emission of small particles in different gas atmospheres  

NASA Astrophysics Data System (ADS)

The problem of laser pulse interaction with small solid particles in a gas atmosphere when detecting its parameters is a serous one in industrial and environmental applications. Previous investigations have shown the possibility of using the laser induced breakdown method. This method is very sensitive, but for a particle size of less than 0.1 micrometers the damage threshold of the solid target is very close to the breakdown point of pure gas. At breakdown, a small volume of dense hot plasma emits radiation by which the size and material of particles can be detected. We used an analytical model, simulation code and experiments to analyze this radiation and found that the emitted intensity varied with laser, gas and particle parameters. The increased dependence of SSP plasma emission rate on initial particle volume permits this method to be used for measuring small particle size by using emitted line spectrum at the late time stage.

Andreev, Alexander A.; Ueda, Toshitsugu; Wakamatsu, Muneaki

2002-06-01

153

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

154

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

155

[The suitability of commercial bioindicators with spores of B. stearothermophilus for the testing of formaldehyde gas sterilizers].  

PubMed

Commercially available biological indicators with spores of B. stearothermophilus were investigated by the Hygiene-Institutes of Kiel and Lubeck. The objective was to find out if those indicators to which sheep blood was added subsequently correspond to the formaldehyde resistance required by. DIN 58948, part 14 (DIN 58948, part 13). Both working groups determined unanimously that the indicators of one producer showed a resistance too low compared to the remaining biological indicators showing a much higher resistance than required. Even biological indicators manufactured strictly in accordance to the testing standard were more resistant than demanded. This also corresponded to the commercially available untreated spores. On the other hand, practice showed that the biological indicators investigated within this study can be easily killed by formaldehyde sterilizers if they respond to the technical standard. In order to realize the testing of these sterilizers with indicators of a generally accepted resistance we propose either to demand for an equivalently higher formaldehyde resistance or to set up a killing period for the spore resistance from 150 to 240 min until experimentally important data are available. Concerning the blood containing indicators the results of both working groups differed considerably within the limits of formaldehyde efficiency whereas this was not the case with untested commercially available spores. As the addition of thinned blood did not cause an increase in resistance we recommend, in the interest of standardized investigative conditions, not to use it. PMID:1953931

Mecke, P; Christiansen, B; Pirk, A

1991-09-01

156

Energetic binary collisions in rare gas plasmas  

NASA Astrophysics Data System (ADS)

Calculations have been made of cross sections for energy and momentum transfer in binary collisions between like pairs of Ar, Kr, and Xe atoms in the energy range from about 1 to 1000 eV. These calculations were made using a classical model with pair interaction potentials for the rare gases developed from experimental sources, e.g., investigations of specific heats, viscosities, solid-state parameters, and scattering data. Cross sections in this energy range have not been available. The cross sections exhibit a rapid decrease from accepted values at thermal energies as the interaction energy increases. This behavior can be used to understand directed beam propagation limits as well as particle propagation within a plasma. Experimental data have also been fit to a theoretical expression for the Ar resonance charge exchange cross section over the same energy range.

Robinson, R. S.

1979-04-01

157

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

158

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

159

Trends in Performance Improvements of a Coaxial Gas-Fed Pulsed Plasma Thruster  

E-print Network

Trends in Performance Improvements of a Coaxial Gas-Fed Pulsed Plasma Thruster J.K. Ziemer and E Science Research Laboratory Inc. IEPC-97-040§ Abstract The performance of a coaxial gas-fed pulsed plasma, Cleveland, OH, August 24-28, 1997. 1 Introduction Gas-fed pulsed plasma thrusters (GFPPTs) have re- surfaced

Choueiri, Edgar

160

Performance Scaling of Gas-Fed Pulsed Plasma John Kenneth Ziemer  

E-print Network

Performance Scaling of Gas-Fed Pulsed Plasma Thrusters John Kenneth Ziemer A DISSERTATION PRESENTED of Gas-Fed Pulsed Plasma Thrusters Prepared by: John K. Ziemer Approved by: Professor Edgar Y. Choueiri scaling of gas-fed pulsed plasma thrusters (GFPPTs) is in- vestigated theoretically and experimentally

Choueiri, Edgar

161

Fundamentals of Discharge Initiation in Gas-Fed Pulsed Plasma Thrusters  

E-print Network

Fundamentals of Discharge Initiation in Gas-Fed Pulsed Plasma Thrusters IEPC-2005-153 Presented discharges in gas-fed pulsed plasma thrusters (GFPPTs) is conducted. It is argued that undervoltage breakdown standing in the way of the gas-fed pulsed plasma thruster (GFPPT) becoming flight-ready hardware

Choueiri, Edgar

162

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

163

Plasma gas identification using the single Langmuir probe at the PUPR mirror-cusp  

Microsoft Academic Search

Plasma can be produced by ionizing gas particles. Different gases will produce different plasma parameters. Using the single Langmuir probe, the characteristics of argon, nitrogen, hydrogen and residual gas (no gas injected) can be compared. Using a mass spectrometer, we can identify the elements present in the chamber and relate the probe characteristic curve with its respective elements. Each gas

Jorge R. Gaudier; Ramón Rivera; Franklin Colmenares; Giovanni Lleonart; Miguel A. Carrera; Omar Mollina; Ángel González; Edbertho Leal-Quirós; Mark A. Prelas

2008-01-01

164

Plasma quench technology for natural gas conversion applications  

SciTech Connect

This paper describes the experimental demonstration of a process for direct conversion of methane to acetylene in a thermal plasma. The process utilizes a thermal plasma to dissociate methane and form an equilibrium mixture of acetylene followed by a supersonic expansion of the hot gas to preserve the produced acetylene in high yield. The high translational velocities and rapid cooling result in an overpopulation of atomic hydrogen which persists throughout the expansion process. The presence of atomic hydrogen shifts the equilibrium composition by inhibiting complete pyrolysis of methane and acetylene to solid carbon. This process has the potential to reduce the cost of producing acetylene from natural gas. Acetylene and hydrogen produced by this process could be used directly as industrial gases, building blocks for synthesis of industrial chemicals, or oligomerized to long chain liquid hydrocarbons for use as fuels. This process produces hydrogen and ultrafine carbon black in addition to acetylene.

Detering, B.A.; Kong, P.C.; Thomas, C.P. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

1995-07-01

165

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

166

Transport in a field aligned magnetized plasma/neutral gas boundary: the end of the plasma  

NASA Astrophysics Data System (ADS)

The objective of this dissertation is to characterize the physics of a boundary layer between a magnetized plasma and a neutral gas along the direction of a confining magnetic field. A series of experiments are performed at the Enormous Toroidal Plasma Device (ETPD) at UCLA to study this field aligned Neutral Boundary Layer (NBL) at the end of the plasma. A Lanthanum Hexaboride (LaB6) cathode and semi-transparent anode creates a magnetized, current-free helium plasma which terminates on a neutral helium gas without touching any walls. Probes are inserted into the plasma to measure the basic plasma parameters and study the transport in the NBL. The experiment is performed in the weakly ionized limit where the plasma density (ne) is much less than the neutral density (nn) such that ne/nn < 5%. The NBL is characterized by a field-aligned electric field which begins at the point where the plasma pressure equilibrates with the neutral gas pressure. Beyond the pressure equilibration point the electrons and ions lose their momentum by collisions with the neutral gas and come to rest. An electric field is established self consistently to maintain a current-free termination through equilibration of the different species' stopping rates in the neutral gas. The electric field resembles a collisional quasineutral sheath with a length 10 times the electron-ion collision length, 100 times the neutral collision length, and 10,000 times the Debye length. Collisions with the neutral gas dominate the losses in the system. The measured plasma density loss rates are above the classical cross-field current-free ambipolar rate, but below the anomalous Bohm diffusion rate. The electron temperature is below the ionization threshold of the gas, 2.2 eV in helium. The ions are in thermal equilibrium with the neutral gas. A generalized theory of plasma termination in a Neutral Boundary Layer is applied to this case using a two-fluid, current-free, weakly ionized transport model. The electron and ion momentum equations along the field are combined in a generalized Ohm's law which predicts the axial electric field required to maintain a current-free termination. The pressure balance criteria for termination and the predicted electric field are confirmed over a scaling of plasma parameters. The experiment and the model are relevant for studying NBLs in other systems, such as the atmospheric termination of the aurora or detached gaseous divertors. A steady state modified ambipolar system is measured in the ETPD NBL. The drift speeds associated with these currents are a small fraction of the plasma flow speeds and the problem is treated as a perturbation to the termination model. The current-free condition on the model is relaxed to explain the presence of the divergence free current.

Cooper, Christopher Michael

167

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

168

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

169

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

170

Neutral gas plasma interactions and critical ionization velocity phenomena  

NASA Astrophysics Data System (ADS)

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.

1983-11-01

171

Simultaneous gas and plasma driven hydrogen transport in solids  

SciTech Connect

The transport parameter formalism for evaluating the steady state hydrogen (tritium) inventory, permeation rate and recycle time for surfaces exposed to the plasma of an operating magnetic confinement fusion reactor has been extended to include synergistic effects of gas and plasma driven permeation. This steady state formalism includes hydrogen trapping, recombination barriers to release at inner and outer surfaces, diffusion, and effects of thermal gradients (e.g., Ludwig-Soret effect), and is applicable to simultaneous plasma-driven and gas-driven hydrogen injection. In addition to providing a simple way of calculating the magnitude of these important tritium-related concerns, the transport parameter together with the ratio of the recombination coefficients at the two surfaces can also be used to classify the nature of these processes as to whether they are rate limited by bulk diffusion or surface recombination. New simple equations are derived which define these various regimes, and a new regime is identified which could influence permeation-probe measurements of plasma-edge fluxes.

Brice, D.K.; Doyle, B.L.

1986-01-01

172

Simultaneous gas- and plasma-driven hydrogen transport in solids  

SciTech Connect

The transport parameter formalism for evaluating the steady-state hydrogen (tritium) inventory, permeation rate, and recycle time for surfaces exposed to the plasma of an operating magnetic confinement fusion reactor has been extended to include synergistic effects of gas- and plasma-driven permeation. This steady-state formalism includes hydrogen trapping, recombination barriers to release at inner and outer surfaces, diffusion, and effects of thermal gradients (e.g., Ludwig--Soret effect) and is applicable to simultaneous plasma-driven and gas-driven hydrogen injection. In addition to providing a simple way of calculating the magnitude of these important tritium-related concerns, the transport parameter together with the ratio of the recombination coefficients at the two surfaces can also be used to classify the nature of these processes as to whether they are rate limited by bulk diffusion or surface recombination. New simple equations are derived which define these various regimes, and a new regime is identified which could influence permeation-probe measurements of plasma-edge fluxes.

Brice, D.K.; Doyle, B.L.

1987-07-01

173

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

174

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

175

Dimensionless Performance Model for Gas-Fed Pulsed Plasma J.K. Ziemer  

E-print Network

Dimensionless Performance Model for Gas-Fed Pulsed Plasma Thrusters J.K. Ziemer and E.Y. Choueiri Jersey 08544 AIAA-98-3661§ Abstract We present a non-dimensional gas-fed pulsed plasma thruster are discussed. 1 Introduction Modeling the dynamics of a pulsed plasma thruster (PPT) discharge generally

Choueiri, Edgar

176

Laser Discharge Initiation for Gas-fed Pulsed Plasma Thrusters J.W. Berkery  

E-print Network

Laser Discharge Initiation for Gas-fed Pulsed Plasma Thrusters J.W. Berkery and E.Y. Choueiri is to produce spatially uniform current sheet initiation in gas-fed pulsed plasma thrusters. The effect is ex is the initiation of the discharge in a pulsed plasma thruster through laser stimulation of the cathode

Choueiri, Edgar

177

Title of Dissertation: MODELING LASER PULSE EVOLUTION IN IONIZING GAS AND PLASMA WITH  

E-print Network

ABSTRACT Title of Dissertation: MODELING LASER PULSE EVOLUTION IN IONIZING GAS AND PLASMA of laser pulse evolution and plasma response in simulations ranging from modeling laser wakefield energy distribution. #12;MODELING LASER PULSE EVOLUTION IN IONIZING GAS AND PLASMA WITH APPILCATION

Anlage, Steven

178

Screening of a high-density plasma from neutral gas penetration  

Microsoft Academic Search

In several experiments on a magnetically confined plasma and under certain conditions of a fusion reactor in stationary operation, neutral gas will be present in the regions surrounding the plasma. The inflow of neutrals and the outflow of plasma by diffusion or free streaming is studied in this paper, both for closed and open-ended systems:In a closed bottle neutral gas

B. Lehnert

1968-01-01

179

Plasma emission spectral detection for pyrolysis-gas chromatography  

NASA Astrophysics Data System (ADS)

Specific element gas chromatographic detection by plasma emission spectroscopy has been evaluated for the characterization of volatile pyrolyzates from a number of polymers containing hetero-atoms. Directly interfaced rapid-temperature rise time pyrolysis with high resolution open tubular column gas chromatography was employed. The atmospheric pressure microwave induced and sustained plasma utilizing a "Beenakker" type TM 010 cavity was applied for specific detection of phosphorus and carbon in polyphosphazene pyrolysis and for boron in carborane-silicone pyrolysis. An interfaced d.c. argon atmospheric pressure plasma was found more advantageous for the specific determination of silicon in the pyrolysis products of novel linear silarylene-siloxanes. In phosphazene pyrolysis notable differences were seen in the phosphorus content of volatiles formed on pyrolysis between polymers fluoroalkoxy and chlorophenoxy substituents. For carborane-silicones sequential volatilization followed by pyrolysis allowed the identification of residual boron containing monomers as well as pyrolyzates. Pyrolysis of the silarylene-siloxanes showed markedly differing levels of silicon content in polymers with differing aromatic backbones and different levels of vinyl substitution.

Riska, Gregory D.; Estes, Scott A.; Beyer, John O.; Uden, Peter C.

180

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

181

Interplay of discharge and gas flow in atmospheric pressure plasma jets Nan Jiang,1  

E-print Network

Interplay of discharge and gas flow in atmospheric pressure plasma jets Nan Jiang,1 JingLong Yang,2 2011) Interplay of discharge and gas flow in the atmospheric pressure plasma jets generated with three an optical schlieren system. Gas flow gains a forward momentum from discharge except for the case of overflow

Zexian, Cao

182

Operation of ferroelectric plasma sources in a gas discharge modea... A. Dunaevskyb)  

E-print Network

Operation of ferroelectric plasma sources in a gas discharge modea... A. Dunaevskyb) and N. J. In this paper, observations of a gas discharge mode of operation of the ferroelectric plasma sources FPS are reported. The gas discharge appears at pressures between 20 and 80 Torr. At pressures of 1­20 Torr

183

Female Sterilization: Risk of Ectopic Pregnancy After Tubal Sterilization  

MedlinePLUS

... Back to Female Sterilization Female Sterilization: Risk of Ectopic Pregnancy After Tubal Sterilization Fact Sheet Among 10,685 women studied, the risk of ectopic pregnancy within 10 years after sterilization was about ...

184

The Model of Gas-Discharge Nonneutral Electron Plasma  

E-print Network

The model of gas-discharge nonneutral electron plasma has been considered, in which the electron density is limited by non-linear processes initiated by diocotron instability and it does not depend on the mechanism of electron transport across the magnetic field. The model describes well the characteristics of electron sheath and the current characteristics of discharge both, in magnetron geometry and in the geometry of inversed magnetron, and it allows us to describe quantitatively the influence of anode misalignment on the discharge electron sheath for the first time. The scope of applicability of the proposed model, as well as its relation with other models of electron sheath is studied.

Kervalishvili, N A

2013-01-01

185

Electron distribution of the degenerate electron gas of a plasma in a strong electromagnetic field  

NASA Astrophysics Data System (ADS)

The paper determines the electron energy distribution function for the degenerate electron gas of a dense plasma in an intense electromagnetic field. The analysis is applicable to conditions in solid state plasmas.

Ablekov, V. K.; Babaev, Iu. N.; Frolov, A. M.

1980-01-01

186

Plasma polymerization of an ethylene-nitrogen gas mixture  

NASA Technical Reports Server (NTRS)

A procedure has been developed whereby nitrogen can be incorporated into an organic film from an ethylene-nitrogen gas mixture using an internal electrode capacitively coupled radio frequency reactor. The presence of nitrogen has been shown directly by infrared transmittance spectra and electron spectroscopic chemical analysis data, and further indirect evidence was provided by dielectric measurements and by the reverse osmosis properties of the film. Preparation of a nitrogen containing film did not require vapor from an organic nitrogen containing liquid monomer. Some control over the bonding and stoichiometry of the polymer film was provided by the added degree of freedom of the nitrogen partial pressure in the gas mixture. This new parameter strongly affected the dielectric properties of the plasma polymerized film and could affect the reverse osmosis behavior.

Hudis, M.; Wydeven, T.

1975-01-01

187

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

188

The effect of the puffed gas shell profile on plasma dynamics in a small gas-puff Z-pinch  

Microsoft Academic Search

This paper reports on an argon annular gas-puff Z-pinch that has been experimentally investigated with three different nozzles. The puffed gas shell profiles and the plasma implosion have been measured using a fast ionization gauge and a differential interferometer. These experiments confirm that both the puffed gas density and its distribution may effect the compression process of Z-pinch plasma.

C. R. Li; T. C. Yang; C. M. Luo; M. Han

1992-01-01

189

Polarity effect on the behavior of gas puff z-pinch plasma produced by IPP system  

Microsoft Academic Search

Summary form only given, as follows. Hot spots produced by gas-puff z-pinch plasma which are high energy density plasma regions radiate intensive soft X-rays. A gas-puff z-pinch is expected in industrial applications such as soft X-ray lithography, microscopy and lasers. In these cases, the scattering of hot spots is important when the gas-puff z-pinch plasma is used as a point

K. Imasaka; K. Takahashi; J. Suehiro; M. Hara

2001-01-01

190

Establishing isokinetic flow for a plasma torch exhaust gas diagnostic for a plasma hearth furnace  

SciTech Connect

Real time monitoring of toxic metallic effluents in confined gas streams can be accomplished through use of Microwave Induced Plasmas to perform atomic emission spectroscopy, For this diagnostic to be viable it is necessary that it sample from the flowstream of interest in an isokinetic manner. A method of isokinetic sampling was established for this device for use in the exhaust system of a plasma hearth vitrification furnace. The flow and entrained particulate environment were simulated in the laboratory setting using a variable flow duct of the same dimensions (8-inch diameter, schedule 40) as that in the field and was loaded with similar particulate (less than 10 {mu}m in diameter) of lake bed soil typically used in the vitrification process. The flow from the furnace was assumed to be straight flow. To reproduce this effect a flow straightener was installed in the device. An isokinetic sampling train was designed to include the plasma torch, with microwave power input operating at 2.45 GHz, to match local freestream velocities between 800 and 2400 ft/sec. The isokinetic sampling system worked as planned and the plasma torch had no difficulty operating at the required flowrates. Simulation of the particulate suspension was also successful. Steady particle feeds were maintained over long periods of time and the plasma diagnostic responded as expected.

Pollack, B.R.

1996-05-01

191

Gas purification by nonthermal plasma: a case study of ethylene.  

PubMed

The destruction of ethylene in a dielectric barrier discharge plasma is investigated by the combination of kinetic modeling and experiments, as a case study for plasma-based gas purification. The influence of the specific energy deposition on the removal efficiency and the selectivity toward CO and CO2 is studied for different concentrations of ethylene. The model allows the identification of the destruction pathway in dry and humid air. The latter is found to be mainly initiated by metastable N2 molecules, but the further destruction steps are dominated by O atoms and OH radicals. Upon increasing air humidity, the removal efficiency drops by ± 15% (from 85% to 70%), but the selectivity toward CO and CO2 stays more or less constant at 60% and 22%, respectively. Beside CO and CO2, we also identified acetylene, formaldehyde, and water as byproducts of the destruction process, with concentrations of 1606 ppm, 15033 ppm, and 185 ppm in humid air (with 20% RH), respectively. Finally, we investigated the byproducts generated by the humid air discharge itself, which are the greenhouse gases O3, N2O, and the toxic gas NO2. PMID:23676182

Aerts, R; Tu, X; Van Gaens, W; Whitehead, J C; Bogaerts, A

2013-06-18

192

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

193

Radiation pressure and gas drag forces on a melamine-formaldehyde microsphere in a dusty plasma  

E-print Network

Radiation pressure and gas drag forces on a melamine-formaldehyde microsphere in a dusty plasma Bin and gas drag forces acting on a single melamine-formaldehyde microsphere. The radiation pressure force

Goree, John

194

Laser ablated copper plasmas in liquid and gas ambient  

SciTech Connect

The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (n{sub e}) determined using Stark broadening of the Cu I (3d{sup 10}4d{sup 1} {sup 2}D{sub 3/2}-3d{sup 10}4p{sup 1} {sup 2}P{sub 3/2} at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (T{sub e}) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ?590 nm.

Kumar, Bhupesh; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)] [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)

2013-05-15

195

Electron beam relaxation in nonuniform plasma of a steady-state beam-plasma discharge at moderately low gas pressures  

SciTech Connect

Electron beam relaxation in plasma under conditions typical of laboratory plasma devices based on a steady-state beam-plasma discharge was investigated. It is shown that the measured dependences of the beam loss factor in a discharge operating at a moderately low gas pressure disagree with theoretical dependences calculated for a longitudinally uniform plasma. Analytic dependences obtained in the framework of quasilinear theory with allowance for longitudinal plasma inhomogeneity agree with experimental data. Some effects caused by the influence of the main discharge parameters on electron beam relaxation are analyzed.

Serov, A. A. [Russian Research Centre Kurchatov Institute, Institute of Nuclear Fusion (Russian Federation)

2009-07-15

196

Introduction to sterile neutrinos  

E-print Network

Model-building issues raised by the prospect of light sterile neutrinos are discussed in a pedagogical way. I first review the na\\"{\\i}ve proposal that sterile neutrinos be identified with ``right handed neutrinos''. A critical discussion of the simple expedient of adding three gauge singlet fermions to the usual minimal standard model matter content is followed by an examination of right handed neutrinos in extended theories. I introduce the terminology of ``fully sterile'' and ``weakly sterile'' to classify varieties usually conflated under the sterile neutrino banner. After introducing the concepts of ``technical naturalness'' and plain ``naturalness'', the unbearable lightness of being a sterile neutrino is confronted. This problem is used to motivate mirror neutrinos, whose connection with pairwise maximal mixing is emphasised. Some brief remarks about phenomenology are made throughout. The impossibility of identifying the sole sterile neutrino of the currently favoured $2 + 2$ and $3 + 1$ phenomenologic...

Volkas, R R

2002-01-01

197

Sterilization of elastic ligatures for intraoperative mandibulomaxillary immobilization.  

PubMed

Sterilization can influence the mechanical properties of elastic ligatures used for mandibulomaxillary immobilization. The aim of this study was to compare different sterilization protocols (ethylene oxide, autoclave, irradiation, plasma sterilization, povidone-iodine for 24 hours and 70% isopropyl alcohol for 24 hours) of three elastomers (natural rubber, silicone rubber, and polyurethane). Three mechanical variables were assessed in a testing machine: breaking strength, tensile strength and tensile strength after a 24-hour load (material fatigue). Natural rubber was most susceptible to mechanical alteration by sterilization and lost 46% of its breaking strength and 43% of its tensile strength after autoclaving. Polyurethane was more resistant (multiple comparison, Tukey-Kramer), but polyurethane ligatures stuck together after autoclaving. The protocols for low-temperature sterilization, ethylene oxide, irradiation, and plasma were superior to autoclaving and the disinfecting solutions. These data suggest that polyurethane sterilized with ethylene oxide is the material of choice. PMID:10922155

Terheyden, H; Lee, U; Ludwig, K; Kreusch, T; Hedderich, J

2000-08-01

198

Influence of ambient gas on the temperature and density of laser produced carbon plasma  

E-print Network

Influence of ambient gas on the temperature and density of laser produced carbon plasma S. S; accepted for publication 11 November 1997 The effect of ambient gas on the dynamics of the plasma generated than in helium or air as an ambient. © 1998 American Institute of Physics. S0003-6951 98 04102

Harilal, S. S.

199

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

200

Positron plasma techniques and the production of a positronium gas  

NASA Astrophysics Data System (ADS)

The use of buffer gas positron traps has led to numerous advances in the field of positron physics, including improved beams for measurements of positron scattering from atoms and molecules, the production of antihydrogen and the generation of high-density positron pulses. The latter has been used to study dense positronium (Ps), in particular Ps-Ps scattering and the formation of molecular positronium, Ps2. The ability to create non-neutral positron plasmas has played a key role in such experiments; using the rotating wall technique in the strong drive regime [Danielson and Surko, PRL 94, 035001] allows for precise control of the positron density as well as very long confinement times. Here I shall outline the methods we have used to produce intense bursts of dense Ps and consider what we can do using these techniques in the future.

Cassidy, David

2012-10-01

201

Modeling of nonstationary vacuum arc plasma jet interaction with a neutral background gas  

Microsoft Academic Search

A plasma beam formed by a stationary vacuum arc source with a copper cathode is considered as a supersonic hydrodynamic jet interacting by collisions with a neutral atmosphere of background gas (argon). The plasma jet propagation in the neutral atmosphere is calculated numerically using a one-dimensional approximation. The values assumed at the entrance cross section of the plasma jet were

E. Gidalevich; S. Goldsmith; R. L. Boxman

2001-01-01

202

THE USE OF GAS DISCHARGE PLASMAS TO CONTROL COMBUSTION AND AERODYNAMIC FLOWS  

E-print Network

physics, plasma assisted combustion, and plasma assisted flow control. Many of his studies deal THE USE OF GAS DISCHARGE PLASMAS TO CONTROL COMBUSTION AND AERODYNAMIC FLOWS Prof. Mark A flows, where combustion is sustained well below the lean flammabil ity limit. The mechanism for flame

Shyy, Wei

203

Investigation of Vortex Structures in Gas-Discharge Nonneutral Electron Plasma: I. Experimental Technique  

E-print Network

The nonperturbing experimental methods have been described, by means of which the solitary vortex structures in gas-discharge nonneutral electron plasma were detected and investigated. The comparison with the experimental methods used in devices with pure electron plasma was made. The problems of shielding the electrostatic perturbations in nonneutral plasmas were considered.

Kervalishvili, N A

2015-01-01

204

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

205

Effects of ionic liquid electrode on pulse discharge plasmas in the wide range of gas pressures  

SciTech Connect

Gas-liquid interfacial pulse discharge plasmas are generated in the wide range of gas pressures, where an ionic liquid is used as the liquid electrode. By analyzing the characteristics of discharge voltage and current, the discharge mechanisms at low and high pressures are found to be dominated by secondary electron emission and first Townsend ionization, respectively. Therefore, the discharge properties at low and high pressures are mainly determined by the cathode material and the discharge gas type, respectively. Furthermore, the plasma properties are investigated by a double Langmuir probe. The density of the positive pulse plasma is found to be much smaller than that of the negative pulse plasma, although the discharge voltage and current of the negative and positive pulse plasmas are of the same order of magnitude. The positive pulse discharge plasma is considered to quickly diffuse onto the chamber wall from the radially central region due to its high plasma potential compared with that in the peripheral region.

Chen Qiang; Hatakeyama, Rikizo [Department of Electronic Engineering, Tohoku University, Aoba-yama 05, Sendai 980-8579 (Japan); Kaneko, Toshiro [Department of Electronic Engineering, Tohoku University, Aoba-yama 05, Sendai 980-8579 (Japan); CREST/JST, 5, Sanbancho, Chiyoda-ku, Tokyo 102-0075 (Japan)

2010-11-15

206

Paraelectric gas flow accelerator  

NASA Technical Reports Server (NTRS)

A substrate is configured with first and second sets of electrodes, where the second set of electrodes is positioned asymmetrically between the first set of electrodes. When a RF voltage is applied to the electrodes sufficient to generate a discharge plasma (e.g., a one-atmosphere uniform glow discharge plasma) in the gas adjacent to the substrate, the asymmetry in the electrode configuration results in force being applied to the active species in the plasma and in turn to the neutral background gas. Depending on the relative orientation of the electrodes to the gas, the present invention can be used to accelerate or decelerate the gas. The present invention has many potential applications, including increasing or decreasing aerodynamic drag or turbulence, and controlling the flow of active and/or neutral species for such uses as flow separation, altering heat flow, plasma cleaning, sterilization, deposition, etching, or alteration in wettability, printability, and/or adhesion.

Sherman, Daniel M. (Inventor); Wilkinson, Stephen P. (Inventor); Roth, J. Reece (Inventor)

2001-01-01

207

Laser sustained plasma ball lensing effect controlled by means of coaxial gas flow  

NASA Astrophysics Data System (ADS)

The results of laser beam refraction studies in a continuous optical discharge (COD) stabilized in a focused (f4.4) laser beam and coaxial gas flow are reported. A plasma ball formed in COD acts as a defocusing plasma lens where lensing effect occurs mainly due to distributed free electrons. The properties of the plasma lens depending on the electron density distribution and controlled through a gas flow velocity have being studied. Intensity profiles of sustaining laser beam (M2 = 6.6) transmitted through the plasma together with intensity patterns of visible plasma images were simultaneously detected and analyzed. It was found that the dependency of average refraction angle of the sustaining beam in COD plasma on a gas flow velocity drops sharply as the velocity increased 1.5 m/s from initial value of 0.06 radians to milliradians, so that at higher gas flow velocities the beam refraction does not affect plasma properties. A shape of the curve of the refraction on gas flow velocity reveals the peculiarities of lensing properties of the plasma ball. The possibility of controlling the lensing effect in plasma by means of the gas flow was also demonstrated.

Zimakov, V. P.; Kedrov, A. Y.; Kuznetsov, V. A.; Shemyakin, A. N.; Solovyov, N. G.; Yakimov, M. Y.

2011-03-01

208

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

Microsoft Academic Search

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

M. K. Boudam; M. Moisan

2010-01-01

209

The Plasma Column Evolution in Gas-Puff Z-Pinches on the Yang Accelerator  

Microsoft Academic Search

The plasma column evolution in gas-puff z-pinch was investigated on the Yang accelerator. The pinch process was significantly influenced by the initial gas distribution. Uniformity of the gas-puff distribution resulted in the asymmetry of the initially load current through the main channels of the plasma layer. The zipper velocity and implosion speed under ``trumpet'' distribution was given, it was observed

Jianjun Deng; Libing Yang; Yuanchao Gu; Xianbing Huang; Fengping Li; Zeping Xv; Shican Ye; Guanghua Cheng; Lihua Chang; Shaotong Zhou; Siqun Zhang; Weiping Xie; Bonan Ding; Xianjue Peng

2006-01-01

210

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

211

Optical observation of the instability in microsecond gas-puff z-pinch plasmas  

Microsoft Academic Search

The occurrence of fluid instabilities in gas-puff z-pinch plasmas have been investigated using laser diagnostic systems. An interferometer system was employed to investigate the temporal evolution of the structure in the plasma column during the pinch. The z-pinch plasma was driven by a fast bank, which provided a current of 160 kA at 1.5 µs (T\\/4). Initially the plasma was

Sunao Katsuki; Koichi Murayama; Hidenori Akiyama

2000-01-01

212

Gasification of biomass in water\\/gas-stabilized plasma for syngas production  

Microsoft Academic Search

The experimental reactor PLASGAS for plasma pyrolysis and vitrification equipped with the hybrid gas-water stabilized torch\\u000a was used in the experiments. The plasma torch is characterized by low density, high temperature plasma with very low mass\\u000a flow rates and high enthalpy. High plasma enthalpy is advantageous for adjustment of higher reaction temperatures with high\\u000a energy efficiency. Gasification of biomass was

M. Hrabovsky; M. Konrad; V. Kopecky; M. Hlina; T. Kavka; G. van Oost; E. Beeckman; B. Defoort

2006-01-01

213

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

214

The Interaction of Hot Gas, Cool Gas and Dust, and Radio Plasma in the Central Galaxies of Cool Core Clusters  

Microsoft Academic Search

Some recent results on the interaction of the hot, X-ray emitting gas, cooler gaseous phases, dust, and radio plasma in the brightest cluster galaxies at the centers of cool core clusters of galaxies will be presented. The combination of low frequency radio images and sensitive X-ray observations shows that interactions between radio sources and the gas in clusters, groups, and

Craig L. Sarazin

2010-01-01

215

Transport in a field-aligned magnetized plasma and neutral gas boundary: the end of the plasma  

NASA Astrophysics Data System (ADS)

A series of experiments at the Enormous Toroidal Plasma Device (ETPD) at UCLA study the Neutral Boundary Layer (NBL) between a magnetized plasma and a neutral gas in the direction of the confining field. A lanthanum hexaboride (LaB6) cathode and semi-transparent anode create a current-free, weakly ionized (ne/nn<5%), helium plasma (B˜250 G, Rplasma=10cm, ne<10^12cm^3, Te<3eV, and Ti˜Tn) that terminates on helium gas without touching any walls. Probes inserted into the plasma measure the basic plasma parameters in the NBL. The NBL begins where the plasma and neutral gas pressures equilibrate and the electrons and ions come to rest through collisions with the neutral gas. A field-aligned electric field (??/kTe˜1) is established self-consistently to maintain a current-free termination and dominates transport in the NBL, similar to a sheath but with a length L˜10?ei˜10^2?en˜10^5?D. A two-fluid weakly-ionized transport model describes the system. A generalized Ohm's Law correctly predicts the electric field observed. The pressure balance criteria and magnitude of the termination electric field are confirmed over a scaling of parameters. The model can also be used to describe the atmospheric termination of aurora or fully detached gaseous divertors.

Cooper, Christopher; Gekelman, Walter

2012-10-01

216

Role of neutral gas in scrape-off layer tokamak plasma  

NASA Astrophysics Data System (ADS)

Neutral gas in scrape-off layer of tokamak plasma plays an important role as it can modify the plasma turbulence. In order to investigate this, we have derived a simple two-dimensional (2D) model that consists of electron continuity, quasi-neutrality, and neutral gas continuity equations using neutral gas ionization and charge exchange processes. Simple 1D profile analysis predicts neutral penetration depth into the plasma. Growth rate obtained from the linear theory has been presented. The 2D model equations have been solved numerically. It is found that the neutral gas reduces plasma fluctuations and shifts spectrum of the turbulence towards lower frequency side. The neutral gas fluctuation levels have been presented. The numerical results have been compared with Aditya tokamak experiments.

Bisai, N.; Jha, R.; Kaw, P. K.

2015-02-01

217

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

218

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

219

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

220

The Plasma Column Evolution in Gas-Puff Z-Pinches on the Yang Accelerator  

SciTech Connect

The plasma column evolution in gas-puff z-pinch was investigated on the Yang accelerator. The pinch process was significantly influenced by the initial gas distribution. Uniformity of the gas-puff distribution resulted in the asymmetry of the initially load current through the main channels of the plasma layer. The zipper velocity and implosion speed under 'trumpet' distribution was given, it was observed the pinch speed and the temperature of the plasma near cathode increased when the rise time of the load current was shortened.

Deng Jianjun; Yang Libing; Gu Yuanchao; Huang Xianbing; Li Fengping; Xv Zeping; Ye Shican; Cheng Guanghua; Chang Lihua; Zhou Shaotong; Zhang Siqun; Xie Weiping; Ding Bonan; Peng Xianjue [China Academy of Engineer Physics, P.O.Box 919-150, Mianyang, Sichuan, 621900 (China)

2006-01-05

221

Introduction to sterile neutrinos  

NASA Astrophysics Data System (ADS)

Model-building issues raised by the prospect of light sterile neutrinos are discussed in a pedagogical way. I first review the naive proposal that sterile neutrinos be identified with “right handed neutrinos”. A critical discussion of the simple expedient of adding three gauge singlet fermions to the usual minimal standard model matter content is followed by an examination of right handed neutrinos in extended theories. I introduce the terminology of “fully sterile” and “weakly sterile” to classify varieties usually conflated under the sterile neutrino banner. After introducing the concepts of “technical naturalness” and plain “naturalness”, the unbearable lightness of being a sterile neutrino is confronted. This problem is used to motivate mirror neutrinos, whose connection with pairwise maximal mixing is emphasised. Some brief remarks about phenomenology are made throughout. The impossibility of identifying the sole sterile neutrino of the currently favoured 2 + 2 and 3 + 1 phenomenological constructs as a lone gauge singlet fermion added to the minimal standard model is explained. Finally, I remark on the beauty and subtlety of light sterile neutrino cosmology.

Volkas, R. R.

2002-07-01

222

Introduction to sterile neutrinos  

E-print Network

Model-building issues raised by the prospect of light sterile neutrinos are discussed in a pedagogical way. I first review the na\\"{\\i}ve proposal that sterile neutrinos be identified with ``right handed neutrinos''. A critical discussion of the simple expedient of adding three gauge singlet fermions to the usual minimal standard model matter content is followed by an examination of right handed neutrinos in extended theories. I introduce the terminology of ``fully sterile'' and ``weakly sterile'' to classify varieties usually conflated under the sterile neutrino banner. After introducing the concepts of ``technical naturalness'' and plain ``naturalness'', the unbearable lightness of being a sterile neutrino is confronted. This problem is used to motivate mirror neutrinos, whose connection with pairwise maximal mixing is emphasised. Some brief remarks about phenomenology are made throughout. The impossibility of identifying the sole sterile neutrino of the currently favoured $2 + 2$ and $3 + 1$ phenomenological constructs as a lone gauge singlet fermion added to the minimal standard model is explained. Finally, I remark on the beauty and subtlety of light sterile neutrino cosmology.

Raymond R. Volkas

2001-11-26

223

Effect of Deuterium Gas Puff On The Edge Plasma In NSTX  

SciTech Connect

This paper describes a detailed examination of the effects of a relatively small pulsed deuterium gas puff on the edge plasma and edge turbulence in NSTX. This gas puff caused little or no change in the line-averaged plasma density or total stored energy, or in the edge density and electron temperature up to the time of the peak of the gas puff. The radial profile of the D? light emission and the edge turbulence within this gas puff did not vary significantly over its rise and fall, implying that these gas puffs did not significantly perturb the local edge plasma or edge turbulence. These measurements are compared with modeling by DEGAS 2, UEDGE, and with simplified estimates for the expected effects of this gas puff.

Zweben, S. J.

2014-02-20

224

Effect of a deuterium gas puff on the edge plasma in NSTX  

NASA Astrophysics Data System (ADS)

This paper describes a detailed examination of the effects of a relatively small pulsed deuterium gas puff on the edge plasma and edge turbulence in NSTX. This gas puff caused little or no change in the line-averaged plasma density or total stored energy, or in the edge density and electron temperature up to the time of the peak of the gas puff. The radial profile of the D? light emission and the edge turbulence within this gas puff did not vary significantly over its rise and fall, implying that these gas puffs did not significantly perturb the local edge plasma or edge turbulence. These measurements are compared with modeling by DEGAS 2, UEDGE, and with simplified estimates for the expected effects of this gas puff.

Zweben, S. J.; Stotler, D. P.; Bell, R. E.; Davis, W. M.; Kaye, S. M.; LeBlanc, B. P.; Maqueda, R. J.; Meier, E. T.; Munsat, T.; Ren, Y.; Sabbagh, S. A.; Sechrest, Y.; Smith, D. R.; Soukhanovskii, V.

2014-09-01

225

Nanosecond laser pulse interactions with breakdown plasma in gas medium confined in a microhole  

NASA Astrophysics Data System (ADS)

The previous investigations on nanosecond laser pulse interactions with breakdown plasma in a gas medium confined in a microhole have been limited. This kind of plasma has been studied in this paper. Due to the significant measurement difficulty resulted from the very small spatial and temporal scales involved, a physics-based computational model has been employed as the investigation tool. The model is developed by solving gas dynamic equations numerically using the finite difference method based on an essentially non-oscillatory scheme. The gas dynamic equations are coupled with suitable equation of state, where the electron number density for plasma region is calculated through the Saha equation. Using the model, the spatial confinement effects of the microhole sidewall on the plasma evolution under laser radiation have been investigated. It has been found that under the studied conditions the hole sidewall confinement can greatly enhance the plasma temperature, pressure, and thrust (over the same surface area). The enhancement should be due to the sidewall's restriction on the plasma lateral expansion and the sidewall's reflection of the pressure wave induced by plasma. This study implies potential advantages of the breakdown plasma confined in a microhole in many relevant applications, such as laser propulsion and laser-induced breakdown spectroscopy. The developed model also provides a useful guiding tool for future fundamental research and practical applications in many areas related to laser interactions with gas breakdown plasma.

Tao, Sha; Wu, Benxin

2013-11-01

226

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

227

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

228

Experimental study of implosion plasma physical characteristics in a small puff-gas z-pinch  

SciTech Connect

This paper presents the physical characteristics of the z-pinch implosion plasma. Experiments were carried out on a small gas-puff z-pinch plasma device. A three-frame Mach-Zehnder interferometer was developed to measure implosion plasma. Some important physical parameters of plasma implosion process were obtained. At the same time, the soft x-ray energy spectra range from 0.2 {approx} 1.5 keV and the energy spectra of ion beam emitted from the z-pinch plasma were measured.

Zou, X.B.; Wang, X.X.; Han, M.; Luo, C.M.; Zhang, G.X.; Liu, Z. [Gas Discharge and Plasma Laboratory, Dept. of Electrical Engineering, Tsinghua University, Beijing 100084 (China)

2006-01-05

229

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

SciTech Connect

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 × 10{sup 18} cm{sup ?3}, the peak normalized laser vector potential, a{sub 0}, increases from 1.0 to 1.85 close to the entrance plane of the capillary compared with a{sub 0} = 1.41 when the plume is neglected.

Ciocarlan, C. [Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom) [Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Department of Nuclear Physics, Horia Hulubei National Institute of Physics and Nuclear Engineering, 76900 Bucharest-Magurele (Romania); Wiggins, S. M.; Islam, M. R.; Ersfeld, B.; Abuazoum, S.; Wilson, R.; Aniculaesei, C.; Welsh, G. H.; Vieux, G.; Jaroszynski, D. A. [Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom)] [Department of Physics, Scottish Universities Physics Alliance, University of Strathclyde, Glasgow G4 0NG (United Kingdom)

2013-09-15

230

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

E-print Network

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 selffocusing 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 3.01018 cm3, the peak normalized...

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

2013-01-01

231

Long-Lived Vortex Structures in Collisional Pure and Gas-Discharge Nonneutral Electron Plasmas  

E-print Network

The analysis of experimental investigations of equilibrium, interaction and dynamics of vortex structures in pure electron and gas-discharge electron nonneutral plasmas during the time much more than the electron-neutral collision time has been carried out. The problem of long confinement of the column of pure electron plasma in Penning-Malmberg trap is considered. The mechanism of stability of long-lived vortex structure in gas-discharge nonneutral electron plasma is investigated. The collapse of electron sheath in gas-discharge nonneutral electron plasma in Penning cell at high pressures of neutral gas is described. The interaction between the stable vortex structure and the annular electron sheath, and the action of vortex structures on the transport of electrons along and across the magnetic field are discussed.

Kervalishvili, N A

2013-01-01

232

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

233

Characteristics of an opto-galvanic effect in cesium and other gas discharge plasmas  

Microsoft Academic Search

The change in the voltage between the electrodes of a gas discharge plasma when illuminated at wavelengths corresponding to allowed transitions in the gas atoms has been measured for cesium, uranium, argon, neon, hydrogen, and mercury plasmas. Using this effect, high signal-to-noise absorption spectra were obtained with a mechanically scanned cw Rh6G dye laser. Magnitude, polarity, and saturation of the

William B. Bridges

1978-01-01

234

Study of atmospheric plasma spray process with the emphasis on gas-shrouded nozzles  

Microsoft Academic Search

An atmospheric plasma spraying process is investigated in this work by using experimental approach and mathematical modelling. Emphasis was put on the gas shrouded nozzles, their design, and the protection against the mixing with the surrounding air, which they give to the plasma jet. First part of the thesis is dedicated to the analysis of enthalpy probe method, as a

Miodrag M. Jankovic

1997-01-01

235

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

236

Decomposition of Adsorbed Xylene on Adsorbent Using Nonthermal Plasma and Gas Circulation  

Microsoft Academic Search

The xylene decomposition system which consists of adsorption process by adsorbents and adsorbed xylene decomposition process using nonthermal plasma with gas circulation is investigated. Two types of hydrophobic zeolite pellets are used as adsorbent. The ac 60 Hz and 20 kHz high voltage power supplies are employed for nonthermal plasma generation. After p-xylene or xylene mixture which consists of o-,

Tomoyuki KUROKI; Kiyoyuki HIRAI; Ryouhei KAWABATA; Masaaki OKUBO; Toshiaki YAMAMOTO

2008-01-01

237

Removal of NOx and SO2 in flue gas by corona plasma reactor with water film  

Microsoft Academic Search

NOx and SO2 removal methods using plasma chemical reactions in nonthermal plasma have been widely studied. In this paper, a novel type of corona discharge model with water film was designed. The reactor is composed of needle-plate electrodes that are placed in a glass container filled with the flue gas, (the plate electrode is immersed in the water). The influence

Limin Dong; Jiaxiang Yang

2002-01-01

238

Adapting Continuous-Flow Plasma Jets for Intermittent Ignition in Gas Turbine Combustors  

Microsoft Academic Search

The effectiveness as pulsed igniters of plasma jets originally designed as continuous-flow radical generators, developed for flame stabilisation, is investigated with particular reference to ignition in aircraft gas turbines. It is found that these devices are able to ignite kerosene sprays in aircraft flame tubes more effectively than conventional high energy igniters, with either nitrogen or air as the plasma

G. K. CHERIYAN; K. KRALLIS; F. J. WEINBERG

1990-01-01

239

Instabilities in fissioning plasmas as applied to the gas-core nuclear rocket-engine  

NASA Technical Reports Server (NTRS)

The compressional wave spectrum excited in a fissioning uranium plasma confined in a cavity such as a gas cored nuclear reactor, is studied. Computer results are presented that solve the fluid equations for this problem including the effects of spatial gradients, nonlinearities, and neutron density gradients in the reactor. Typically the asymptotic fluctuation level for the plasma pressure is of order 1 percent.

1973-01-01

240

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

241

ECR-MBE Growth of GaN Using Hydrogen-Nitrogen Mixed Gas Plasma  

Microsoft Academic Search

SUMMARY Electron-cyclotron-resonance plasma-excited molecular beam epitaxial (ECR-MBE) growth ofGaN using hydrogen-nitrogen mixed gas plasma was investigated. The growth rate ofGaN was drastically increased by addition ofhy- drogen to nitrogen plasma. The transition ofreflection high en- ergy electron diffraction (RHEED) patterns, from streaked pat- terns created without the presence ofhydrogen to spotted pat- terns in the presence ofhydrogen, indicated that the

Yasuo CHIBA; Tsutomu ARAKI; Yasushi NANISHI

2000-01-01

242

Optical observation of the instability in microsecond gas-puff z-pinch plasmas  

Microsoft Academic Search

Summary form only given. The occurrence and growth of fluid instabilities in gas-puff z-pinch plasmas have been investigated by using laser diagnostic systems. A schlieren system was employed to investigate the temporal evolution of the structure in the plasma during the pinch. The z-pinch plasma was driven by a fast bank, which provided a current of 150 kA at 1.55s

Murayama; S. Katsuki; H. Akiyama; I. Fukudome

2001-01-01

243

Optical Observation of the Instability in Microsecond Gas-Puff Z-Pinch Plasmas  

Microsoft Academic Search

The occurrence of fluid instabilities in gas-puff z-pinch plasmas have been investigated using laser diagnostic systems. An interferometer system was employed to investigate the temporal evolution of the structure in the plasma column during the pinch. The z-pinch plasma was driven by a fast bank, which provided a current of 160 kA for 1.5 mus quarter period of oscillation. Initially

Sunao Katsuki; Koichi Murayama; Hidenori Akiyama

2001-01-01

244

Gas flow dependence for plasma-needle disinfection of S. mutans bacteria  

Microsoft Academic Search

The role of gas flow and transport mechanisms are studied for a small low-power impinging jet of weakly-ionized helium at atmospheric pressure. This plasma needle produces a non-thermal glow discharge plasma that kills bacteria. A culture of Streptococcus mutans (S. mutans) was plated onto the surface of agar, and spots on this surface were then treated with plasma. Afterwards, the

J. Goree; Bin Liu; David Drake

2006-01-01

245

Ozone-mist spray sterilization for pest control in agricultural management  

NASA Astrophysics Data System (ADS)

We developed a portable ozone-mist sterilization system to exterminate pests (harmful insects) in agricultural field and greenhouse. The system is composed of an ozone generator, an ozone-mist spray and a small container of ozone gas. The ozone generator can supply highly concentrated ozone using the surface dielectric barrier discharge. Ozone-mist is produced using a developed nozzle system. We studied the effects of ozone-mist spray sterilization on insects and agricultural plants. The sterilization conditions are estimated by monitoring the behavior of aphids and observing the damage of the plants. It was shown that aphids were exterminated in 30 s without noticeable damages of the plant leaves. The reactive radicals with strong oxidation potential such as hydroxyl radical (*OH), hydroperoxide radical (*HO2), the superoxide ion radical (*O2?) and ozonide radical ion (*O3?) can increase the sterilization rate for aphids. 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.

Ebihara, Kenji; Mitsugi, Fumiaki; Ikegami, Tomoaki; Nakamura, Norihito; Hashimoto, Yukio; Yamashita, Yoshitaka; Baba, Seiji; Stryczewska, Henryka D.; Pawlat, Joanna; Teii, Shinriki; Sung, Ta-Lun

2013-02-01

246

Aeration time following ethylene oxide sterilization for reusable rigid sterilization containers: concentration of gaseous ethylene oxide in containers.  

PubMed

Because ethylene oxide (EO) gas is toxic to humans, restrictions have been imposed on its use for sterilization, specifying allowable levels of residual EO remaining in sterilized apparatus and materials. However, the aeration time that optimizes the removal of the remaining EO when a rigid sterilizing container is used for a vessel had not been identified. Therefore, polyvinyl chloride, which easily adsorbs EO, was placed in rigid sterilizing containers, and aeration was carried out after 1, 8, 12, 17, and 24 hours. After standard EO sterilization, the EO concentrations remaining in the air in the rigid containers were measured. The results indicate that a period of 17 hours of aeration is appropriate when a rigid sterilizing container is used. PMID:10820640

Nakata, S; Umeshita, K; Ueyama, H; Takashina, M; Noguchi, S; Murata, A; Ochi, T

2000-01-01

247

Optimization of the ethylene oxide sterilization process.  

PubMed

Hospitals and manufacturers of medical supplies use ethylene oxide (EO) gas almost exclusively to sterilize devices that are heat sensitive. However, the evidence relating the mutagenicity and cytogeneticity shows the desirability of reducing personal exposure to a practical minimum. PMID:10294448

Mathews, I P; Samuel, A H; Gibson, C

1989-06-01

248

Measurement of activated species generated by 60 Hz excited atmospheric pressure Ar plasma in atmospheric gas  

NASA Astrophysics Data System (ADS)

Atmospheric pressure plasmas have a wide field of applications. To improve the performance, it needs to diagnose the behaviors of activated species generated by plasma discharge and to study about the gas-phase reactions in atmospheric pressure. Moreover, plasma treatments are frequently carried out under atmospheric condition without purge gases. In this study, behaviors of activated species generated by the atmospheric pressure plasma under atmospheric condition have been measured by using LIF spectroscopy. Firstly, concentration of the grand state nitrogen monoxide (NO) was measured. The wavelength of laser light for the excitation of NO was 226.3 nm. The fluorescence was observed on A-X(0, 2) band around 247 nm. The AC excited atmospheric pressure plasma with pure Ar gas was generated under atmospheric condition. The flow rate of Ar gas was fixed at 3 slm. The atmospheric condition was the humidity of 40% and ambient temperature of 25 ^oC. Concentration of NO has been measured as a function of distance from a jet slit of plasma head. The length of plasma jet was around 10 mm. The results show that the concentration of NO has a maximum at 10 mm from plasma head, and then decreases. This means that the influence of ambient gases was largest in the edge region of plasma.

Takeda, Keigo; Jolibois, Jerome; Ishikawa, Kenji; Tanaka, Hiromasa; Kano, Hiroyuki; Sekine, Makoto; Hori, Masaru

2012-10-01

249

Microbiological aspects of Radiation Sterilization  

E-print Network

, Air Dispersions Ltd, Manchester, UK #12;2 Sterilization EN ISO 11137 Sterilization of health care products Part 1 (2006): Requirements for development, validation and routine control of a sterilization of 25 kGy or 15 kGy, the primary manufacturer shall have evidence that the selected sterilization dose

250

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

251

Female Sterilization (Tubal Ligation)  

MedlinePLUS

... sterilization? Complications are rare and are usually from general anesthesia and not the procedure. There is a low risk of hurting the bowel, bladder or major blood vessel. If an electric current is used to destroy the fallopian tubes, ...

252

Fundamental Processes in A general definition of a plasma is: plasma is an ionized gas or other medium  

E-print Network

is an ionized gas or other medium in which charged particle interactions are predominantly collective. In contrast, in a plasma the charged particles interact simultaneously and hence collectively with many other by the collective but weak interactions between large numbers of nearby charged particles in it. Charged particles

Callen, James D.

253

Fullerene-rare gas mixed plasmas in an electron cyclotron resonance ion source  

E-print Network

A synthesis technology of endohedral fullerenes such as Fe@C60 has developed with an electron cyclotron resonance (ECR) ion source. The production of N@C60 was reported. However, the yield was quite low, since most fullerene molecules were broken in the ECR plasma. We have adopted gas-mixing techniques in order to cool the plasma and then reduce fullerene dissociation. Mass spectra of ion beams extracted from fullerene-He, Ar or Xe mixed plasmas were observed with a Faraday cup. From the results, the He gas mixing technique is effective against fullerene destruction.

Asaji, T; Uchida, T; Minezaki, H; Ishihara, S; Racz, R; Muramatsu, M; Biri, S; Kitagawa, A; Kato, Y; Yoshida, Y

2015-01-01

254

Fullerene-rare gas mixed plasmas in an electron cyclotron resonance ion source  

SciTech Connect

A synthesis technology of endohedral fullerenes such as Fe@C{sub 60} has developed with an electron cyclotron resonance (ECR) ion source. The production of N@C{sub 60} was reported. However, the yield was quite low, since most fullerene molecules were broken in the ECR plasma. We have adopted gas-mixing techniques in order to cool the plasma and then reduce fullerene dissociation. Mass spectra of ion beams extracted from fullerene-He, Ar or Xe mixed plasmas were observed with a Faraday cup. From the results, the He gas mixing technique is effective against fullerene destruction.

Asaji, T., E-mail: asaji@oshima-k.ac.jp; Ohba, T. [Oshima National College of Maritime Technology, 1091-1 Komatsu, Suo-oshima, Oshima, Yamaguchi 742-2193 (Japan)] [Oshima National College of Maritime Technology, 1091-1 Komatsu, Suo-oshima, Oshima, Yamaguchi 742-2193 (Japan); Uchida, T.; Yoshida, Y. [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan)] [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan); Minezaki, H.; Ishihara, S. [Graduate School of Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan)] [Graduate School of Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan); Racz, R.; Biri, S. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem Tér 18/c (Hungary)] [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem Tér 18/c (Hungary); Muramatsu, M.; Kitagawa, A. [National Institute of Radiological Sciences (NIRS), 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)] [National Institute of Radiological Sciences (NIRS), 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Kato, Y. [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)] [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)

2014-02-15

255

Fullerene-rare gas mixed plasmas in an electron cyclotron resonance ion source  

NASA Astrophysics Data System (ADS)

A synthesis technology of endohedral fullerenes such as Fe@C60 has developed with an electron cyclotron resonance (ECR) ion source. The production of N@C60 was reported. However, the yield was quite low, since most fullerene molecules were broken in the ECR plasma. We have adopted gas-mixing techniques in order to cool the plasma and then reduce fullerene dissociation. Mass spectra of ion beams extracted from fullerene-He, Ar or Xe mixed plasmas were observed with a Faraday cup. From the results, the He gas mixing technique is effective against fullerene destruction.

Asaji, T.; Ohba, T.; Uchida, T.; Minezaki, H.; Ishihara, S.; Racz, R.; Muramatsu, M.; Biri, S.; Kitagawa, A.; Kato, Y.; Yoshida, Y.

2014-02-01

256

Auditing radiation sterilization facilities  

NASA Astrophysics Data System (ADS)

The diversity of radiation sterilization systems available today places renewed emphasis on the need for thorough Quality Assurance audits of these facilities. Evaluating compliance with Good Manufacturing Practices is an obvious requirement, but an effective audit must also evaluate installation and performance qualification programs (validation_, and process control and monitoring procedures in detail. The present paper describes general standards that radiation sterilization operations should meet in each of these key areas, and provides basic guidance for conducting QA audits of these facilities.

Beck, Jeffrey A.

257

Sterile Gowning Procedures  

NSDL National Science Digital Library

The North Carolina Community College System BioNetwork's interactive eLearning tools (IETs) are reusable chunks of training that can be deployed in a variety of courses or training programs. IETs are designed to enhance, not replace hands-on training. Learners are able to enter a hands-on lab experience better prepared and more confident. This particular IET delves into Sterile Gowning Procedures, which teaches the steps for proper sterile gowning and gloving.

258

Government offers sterilization incentive.  

PubMed

The government has decided to offer an additional incentive to its employes who volunteer for sterilization, it was reported on December 23 (pop, 5955). Volunteers, who have to be below 50 years in the case of men and below 45 in the case of women, will pay .5% less interest on housebuilding loans, besides receiving the usual bonus of Rs. 75 for every sterilization. PMID:12261548

259

Inactivation of algae in ballast water with multi-needle gas-liquid hybrid discharge reactor  

Microsoft Academic Search

Pulsed high-voltage discharge is a new advanced oxidation water treatment technology. Plasma technology has recently become significant because it offers the advantages of lower costs, higher treatment and energy efficiencies, and the smaller space volume it occupies. The present work investigates the use of a multi-needle plate reactor with gas-liquid hybrid discharge system to sterilize ballast water. The optimal sterilization

Nyein Nyein Aye; Sun Bing; Xiaomei Zhu; Zhiying Gao; Masayuki Sato

2010-01-01

260

Theoretical Study of Plasma Parameters Dependence on Gas Temperature in an Atmospheric Pressure Argon Microwave Discharge  

Microsoft Academic Search

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

M. Pencheva; E. Benova; I. Zhelyazkov

2008-01-01

261

Gas Temperature Determination in Argon-Helium Plasma at Atmospheric Pressure using van der Waals Broadening  

SciTech Connect

The use of the van der Waals broadening of Ar atomic lines to determine the gas temperature in Ar-He plasmas, taking into account both argon and helium atoms as perturbers, has been analyzed. The values of the gas temperature inferred from this broadening have been compared with those obtained from the spectra of the OH molecular species in the discharge.

Munoz, Jose; Yubero, Cristina; Calzada, Maria Dolores [Grupo de Espectroscopia de Plasmas, Edificio A. Einstein (C-2), Campus Rabanales, Universidad de Cordoba (Spain); Dimitrijevic, Milan S. [Astronomical Observatory, Volgina 7, 11060 Belgrade (Serbia)

2008-10-22

262

On anomalous temporal evolution of gas pressure in inductively coupled plasma  

SciTech Connect

The temporal measurement of gas pressure in inductive coupled plasma revealed that there is an interesting anomalous evolution of gas pressure in the early stage of plasma ignition and extinction: a sudden gas pressure change and its relaxation of which time scales are about a few seconds and a few tens of second, respectively, were observed after plasma ignition and extinction. This phenomenon can be understood as a combined result between the neutral heating effect induced by plasma and the pressure relaxation effect for new gas temperature. The temporal measurement of gas temperature by laser Rayleigh scattering and the time dependant calculations for the neutral heating and pressure relaxation are in good agreement with our experimental results. This result and physics behind are expected to provide a new operational perspective of the recent plasma processes of which time is very short, such as a plasma enhanced atomic layer deposition/etching, a soft etch for disposal of residual by-products on wafer, and light oxidation process in semiconductor manufacturing.

Seo, B. H.; Chang, H. Y. [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)] [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); You, S. J.; Kim, J. H.; Seong, D. J. [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of)] [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of)

2013-04-01

263

Experimental study of a supersonic plasma jet interacting with an ambient gas  

NASA Astrophysics Data System (ADS)

The dynamics of the interaction of a supersonic, radiatively cooled plasma jet with an ambient gas are presented. The experimental setup consists of a radial foil, a ?m-thick aluminum disc held between two concentric electrodes and subjected to a 1.4 MA, 250 ns current pulse from the MAGPIE generator. The plasma flow, with typical velocities of ˜70-90 km/s, is produced by the JxB force acting on the plasma ablated from the foil. A jet is formed from the convergence of this ablated plasma on the axis of the system. The jet interacts with an argon ambient (N˜10^16-17 cm-3) from a supersonic gas nozzle (Mach˜9). The formation of several shock structures from the interaction of the jet with the gas will be presented and discussed.

Suzuki-Vidal, F.; Lebedev, S. V.; Krishnan, M.; Swadling, G.; Burdiak, G.; Bland, S. N.; de Grouchy, P.; Hall, G. N.; Harvey-Thompson, A. J.; Khoory, E.; Pickworth, L.; Skidmore, J.; Chittenden, J. P.; Bocchi, M.; Ciardi, A.

2010-11-01

264

Gas-phase and sample characterizations of multiwall carbon nanotube growth using an atmospheric pressure plasma  

SciTech Connect

Multiwall carbon nanotubes (CNTs) are synthesized using an atmospheric pressure rf plasma jet, with helium feed gas and acetylene gas as the precursor. The nanotubes are grown on a substrate with a thin catalyst (iron) film, with the substrate placed downstream from the plasma on a copper hot plate. In situ Fourier transformed infrared spectroscopy indicates an increase in gas temperature and a decrease in the density of the acetylene molecules at higher plasma powers. The helium metastables in the plasma break the C-H bonds in acetylene, causing molecular dissociation. It is apparent that the resultant formation of unsaturated carbon bonds causes taller and more graphitized CNT films to grow, as evident from scanning electron microscopy and Raman analyses of the samples. However, at higher substrate temperatures, taller and better quality films are obtained due to enhanced catalytic activity on the substrate surface.

Chandrashekar, Anand; Lee, Jeong-Soo; Lee, Gil S.; Goeckner, Matthew J.; Overzet, Lawrence J. [Department of Electrical Engineering, University of Texas at Dallas, 2301 North Floyd Road, Richardson, Texas 75080 (United States)

2006-09-15

265

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

266

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

267

Interplay of discharge and gas flow in atmospheric pressure plasma jets  

SciTech Connect

Interplay of discharge and gas flow in the atmospheric pressure plasma jets generated with three different discharge modes [N. Jiang, A. L. Ji, and Z. X. Cao, J. Appl. Phys. 106, 013308 (2009); N. Jiang, A. L. Ji, and Z. X. Cao, J. Appl. Phys. 108, 033302 (2010)] has been investigated by simultaneous photographing of both plasma plumes and gas flows in the ambient, with the former being visualized by using an optical schlieren system. Gas flow gains a forward momentum from discharge except for the case of overflow jets at smaller applied voltages. Larger applied voltage implies an elongated plasma jet only for single-electrode mode; for dielectric barrier discharge jet the plume length maximizes at a properly applied voltage. These findings can help understand the underlying processes, and are useful particularly for the economic operation of tiny helium plasma jets and jet arrays.

Jiang Nan; Cao Zexian [Beijing National Laboratory for Condensed Matters, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Yang Jinglong; He Feng [School of Aerospace, Tsinghua University, Beijing 100084 (China)

2011-05-01

268

Hysteroscopic Tubal Sterilization  

PubMed Central

Background Hysteroscopic tubal sterilization is a minimally invasive alternative to laparoscopic tubal ligation for women who want permanent contraception. The procedures involves non-surgical placement of permanent microinserts into both fallopian tubes. Patients must use alternative contraception for at least 3 months postprocedure until tubal occlusion is confirmed. Compared to tubal ligation, potential advantages of the hysteroscopic procedure are that it can be performed in 10 minutes in an office setting without the use of general or even local anesthesia. Objective The objective of this analysis was to determine the effectiveness and safety of hysteroscopic tubal sterilization compared with tubal ligation for permanent female sterilization. Data Sources A standard systematic literature search was conducted for studies published from January 1, 2008, until December 11, 2012. Review Methods Observational studies, randomized controlled trials (RCTs), systematic reviews and meta-analyses with 1 month or more of follow-up were examined. Outcomes included failure/pregnancy rates, adverse events, and patient satisfaction. Results No RCTs were identified. Two systematic reviews covered 22 observational studies of hysteroscopic sterilization. Only 1 (N = 93) of these 22 studies compared hysteroscopic sterilization to laparoscopic tubal ligation. Two other noncomparative case series not included in the systematic reviews were also identified. In the absence of comparative studies, data on tubal ligation were derived for this analysis from the CREST study, a large, multicentre, prospective, noncomparative observational study in the United States (GRADE low). Overall, hysteroscopic sterilization is associated with lower pregnancy rates and lower complication rates compared to tubal ligation. No deaths have been reported for hysteroscopic sterilization. Limitations A lack of long-term follow-up for hysteroscopic sterilization and a paucity of studies that directly compare the two procedures limit this assessment. In addition, optimal placement of the microinsert at the time of hysteroscopy varied among studies. Conclusions Hysteroscopic sterilization is associated with: lower pregnancy rates compared to tubal ligation (GRADE very low) lower complication rates compared to tubal ligation (GRADE very low) no significant improvement in patient satisfaction compared to tubal ligation (GRADE very low) Plain Language Summary Hysteroscopic tubal 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 conducted a review of the effectiveness and safety of hysteroscopic tubal sterilization compared to tubal ligation. This review indicates that hysteroscopic tubal sterilization is associated with: lower pregnancy rates compared to tubal ligation lower complication rates compared to tubal ligation no significant improvement in patient satisfaction compared to tubal ligation However, we found a number of limitations to the studies available on hysteroscopic tubal sterilization. Among other concerns, most studies did not include long-term follow-up and only 1 study directly compared hysteroscopic tubal sterilization to tubal ligation. PMID:24228084

McMartin, K

2013-01-01

269

Fusion plasma confinement research at the gas dynamic trap  

Microsoft Academic Search

A so called vortex confinement of plasma in axially symmetric mirror device was studied. This recently developed approach enables to significantly reduce transverse particle and heat losses typically caused by MHD instabilities which can be excited in this case. Vortex confinement regime was established by application of different potentials to the radial plasma limiters and end-plates. As a result, the

M. S. Korzhavina; V. V. Prikhodko; E. I. Soldatkina; A. L. Solomakhin; E. I. Pinzhenin; A. V. Lvovsky; A. N. Pushkareva; K. V. Zaytsev

2011-01-01

270

Experiment with a small gas-puff z-pinch plasma device  

Microsoft Academic Search

Summary form only given. A small gas-puff Z-pinch plasma device is composed of a capacitor energy storage bank (capacitance=16.3 ?F, charging voltage=23 kV), field distortion switches, a discharge chamber, vacuum pumping system, fast operation gas valve and diagnostics. The amplitude and the period of discharge current are 230 kA and 9.6 ?s, respectively. Firstly, a hollow gas shell is produced

C. M. Luo; C. R. Li; X. X. Wang; Z. X. Zheng; Z. F. Xie; M. Han

1998-01-01

271

Plasma Density Induced by Relativistic Electron Beam from a Gas Filled Diode  

Microsoft Academic Search

Generation of a relativistic electron beam in a gas-filled foilless diode and its injection into a gas-filled drift region have been studied for application to the pre-ionization of the magnetic mirror plasmas, high-power microwave sources, x-rays and powerful gas-laser pumping. The relativistic electron beam generated from a foilless diode is specially interesting because of good reproducibility of electron beams. The

Han S. Uhm; Eun H. Choi; J. J. Ko; Guangsup Cho; H. M. Shin

1998-01-01

272

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

273

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

274

Fluid absorption study in ultra-high molecular weight polyethylene (UHMWPE) sterilized and unsterilized acetabular cups.  

PubMed

The weight gain due to fluid absorption was measured in gamma-sterilized, ethylene oxide (ETO) gas-sterilized, and unsterilized ultra-high molecular weight (UHMW) polyethylene acetabular cups. After about 2 months the total average fluid absorption gain of the polyethylene cups was: 1.76 +/- 0.45 mg (average +/- standard deviation) for the unsterilized polyethylene cups, 2.81 +/- 0.95 mg for the gamma-sterilized polyethylene cups and 1.51 +/- 0.34 for the ETO gas-sterilized polyethylene cups. There was little difference in fluid absorption between the sterilized and unsterilized specimens. In particular, the gamma-sterilized acetabular cups absorbed more than the ETO gas-sterilized and the unsterilized cups. However, the weight gain was higher in serum compared with that in water. PMID:11323978

Affatato, S; Vandelli, C; Bordini, B; Toni, A

2001-01-01

275

Feed gas humidity: a vital parameter affecting a cold atmospheric-pressure plasma jet and plasma-treated human skin cells  

NASA Astrophysics Data System (ADS)

In this study, the effect of feed gas humidity on the reactive component generation of an atmospheric-pressure argon plasma jet and its effect on human skin cells are investigated. Feed gas humidity is identified as one key parameter that strongly influences stability and reproducibility of plasma medical studies. The plasma jet is investigated by absorption spectroscopy in the ultraviolet and infrared spectral region for its ozone production depending on the humidity concentration in the feed gas. By optical emission spectroscopy the dependence of present excited plasma species such as hydroxyl radicals, molecular nitrogen, argon and atomic oxygen on the feed gas humidity is investigated. As an interface layer between the plasma jet effluent and the biological cell, a buffer solution is treated and the hydrogen peroxide (H2O2) production is studied with two independent colorimetric assays as a function of humidity admixture to the feed gas. Ultimately, the effect of varying feed gas humidity on the cell viability of indirect plasma treated adherent HaCAT cells is investigated. The highest viability is found for the driest feed gas condition. Furthermore, this work shows answers for the relevance of unwanted—or intended—feed gas humidity in plasma medical experiments and their comparatively large relevance with respect to ambient humidity. The findings will lead to more reproducible experiments in the field of plasma medicine.

Winter, J.; Wende, K.; Masur, K.; Iseni, S.; Dünnbier, M.; Hammer, M. U.; Tresp, H.; Weltmann, K.-D.; Reuter, S.

2013-07-01

276

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

(BP) method. The welding experiments were made at arc current of 330 A, with pure argon as shielding Validation in a Gas Metal Arc Welding Plasma Column F. Valensi1,2 , S. Pellerin1 , A. Boutaghane3 , K Spectroscopy, Boltzmann Plot, Sola method, LTE. During gas metal arc welding (GMAW), the plasma obtained has

2011-01-01

277

Plasma ionization frequency, edge-to-axis density ratio, and density on axis of a cylindrical gas discharge  

SciTech Connect

A rigorous derivation of expressions, starting from the governing equations, for the ionization frequency, edge-to-axis ratio of plasma density, plasma density at the axis, and radially averaged plasma density in a cylindrical gas discharge has been obtained. The derived expressions are simple and involve the relevant parameters of the discharge: Cylinder radius, axial current, and neutral gas pressure. The found expressions account for ion inertia, ion temperature, and changes in plasma ion collisionality.

Palacio Mizrahi, J. H. [Physics Department, Technion, Haifa 32000 (Israel)

2014-06-15

278

Experimental study on the dynamics of a cylindrical plasma sheath in a gas-puff z-pinch device  

Microsoft Academic Search

The dynamics of a hollow cylindrical plasma sheath produced in a gas-puff Z-pinch device were studied with a differential interferometer. The velocity of the imploding plasma during three stages of compression the minimum radius of the pinched plasma column, the hot spots and the X-ray emissions were measured. The effect of the parameters of the gas cylinder on the plasma

Cheng Rong Li; Tsin Chi Yang

1991-01-01

279

Gas Kinetic Study of Magnetic Field Effects on Plasma Plumes  

E-print Network

in the Hall regime are performed, confirming the theoretically predicted azimuthal rotation of the plasma jet due to Hall physics. The primary conclusion from this work is that the addition of the Hall effect generates helical structures in magnetic nozzle...

Ebersohn, Frans 1987-

2012-12-07

280

Polarity effect on the behavior of gas-puff z-pinch plasma produced by IPP system  

Microsoft Academic Search

Hot spots produced by gas-puff z-pinch plasma which are high energy density plasma regions radiate intensive soft X-rays. The gas-puff z-pinch is expected to have industrial applications such as soft X-ray lithography, microscopy and in lasers. In these cases, the scattering of hot spots is important when the gas-puff z-pinch plasma is used as a point source of soft X-rays.

K. Imasaka; K. Takahashi; J. Suehiro; M. Hara

2001-01-01

281

Optical diagnostics of a low power---low gas flow rates atmospheric-pressure argon plasma created by a microwave plasma torch  

Microsoft Academic Search

We employ a suite of optical techniques, namely, visual imaging, optical emission spectroscopy and cavity ringdown spectroscopy (CRDS), to characterize a low power, low gas flow rates, atmospheric-pressure argon microwave induced plasma. The plasma is created by a microwave plasma torch, which is excited by a 2.45 GHz microwave with powers ranging from 60 to 120 W. A series of

Chuji Wang; Nimisha Srivastava; Susan Scherrer; Ping-Rey Jang; Theodore S. Dibble; Yixiang Duan

2009-01-01

282

The sterile inflammatory response  

PubMed Central

The acute inflammatory response is a double-edged sword. On the one hand it plays a key role in initial host defense particularly against many infections. On the other hand its aim is imprecise and as a consequence, when it is drawn into battle, it can cause collateral damage in tissues. In situations where the inciting stimulus is sterile, the cost-benefit ratio may be high; because of this, sterile inflammation underlies the pathogenesis of a number of diseases. While there have been major advances in our understanding of how microbes trigger inflammation, much less has been learned about this process in sterile situations. This review focuses on a subset of the many sterile stimuli that can induce inflammation – specifically dead cells and a variety of irritant particles, including crystals, minerals, and protein aggregates. Although this subset of stimuli is structurally very diverse and might appear to be unrelated, there is accumulating evidence that the innate immune system may recognize them in similar ways and stimulate the sterile inflammatory response via common pathways. Here we review established and emerging data about these responses. PMID:20307211

Rock, Kenneth L.; Latz, Eicke; Ontiveros, Fernando; Kono, Hajime

2015-01-01

283

Noble-gas resonant radiation effects on electron emission in plasma devices.  

PubMed

Experimental investigation results for photoemission affected by vacuum ultraviolet radiation of xenon and krypton atoms from a solid in vacuum and the target surface in contact with plasma (gas) are presented. It is demonstrated that, for adsorption (or implantation) of gas atoms into the target, the photoemission response considerably (to an order of magnitude) increases. This is caused by a change in the mechanism of photoemission from a solid surface in contact with plasma (gas), as compared to vacuum. This phenomenon can be characterized by the term adsorption- (implantation-) induced resonant photoemission. The inclusion of this phenomenon has largely transformed our view of gas discharge ignition and glowing, in addition to operating a variety of plasmic and photoelectron devices. A different class of gas discharge instruments can be realized on this basis as well. PMID:23944566

Bokhan, P A; Zakrevsky, Dm E

2013-07-01

284

N2 Gas Plasma Inactivates Influenza Virus by Inducing Changes in Viral Surface Morphology, Protein, and Genomic RNA  

PubMed Central

We have recently treated with N2 gas plasma and achieved inactivation of bacteria. However, the effect of N2 gas plasma on viruses remains unclear. With the aim of developing this technique, we analyzed the virucidal effect of N2 gas plasma on influenza virus and its influence on the viral components. We treated influenza virus particles with inert N2 gas plasma (1.5?kpps; kilo pulses per second) produced by a short high-voltage pulse generated from a static induction thyristor power supply. A bioassay using chicken embryonated eggs demonstrated that N2 gas plasma inactivated influenza virus in allantoic fluid within 5?min. Immunochromatography, enzyme-linked immunosorbent assay, and Coomassie brilliant blue staining showed that N2 gas plasma treatment of influenza A and B viruses in nasal aspirates and allantoic fluids as well as purified influenza A and B viruses induced degradation of viral proteins including nucleoprotein. Analysis using the polymerase chain reaction suggested that N2 gas plasma treatment induced changes in the viral RNA genome. Scanning electron microscopy analysis showed that aggregation and fusion of influenza viruses were induced by N2 gas plasma treatment. We believe these biochemical changes may contribute to the inactivation of influenza viruses by N2 gas plasma. PMID:24195077

Shimizu, Naohiro; Imanishi, Yuichiro

2013-01-01

285

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

286

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review  

NASA Astrophysics Data System (ADS)

The gas temperature in non-equilibrium plasmas is often obtained from the plasma-induced emission by measuring the rotational temperature of a diatomic molecule in its excited state. This is motivated by both tradition and the availability of low budget spectrometers. However, non-thermal plasmas do not automatically guarantee that the rotational distribution in the monitored vibrational level of the diatomic molecule is in equilibrium with the translational (gas) temperature. Often non-Boltzmann rotational molecular spectra are found in non-equilibrium plasmas. The deduction of a gas temperature from these non-thermal distributions must be done with care as clearly the equilibrium between translational and rotational degrees of freedom cannot be achieved. In this contribution different methods and approaches to determine the gas temperature are evaluated and discussed. A detailed analysis of the gas temperature determination from rotational spectra is performed. The physical and chemical background of non-equilibrium rotational population distributions in molecular spectra is discussed and a large range of conditions for which non-equilibrium occurs are identified. Fitting procedures which are used to fit (non-equilibrium) rotational distributions are analyzed in detail. Lastly, recommendations concerning the conditions for which the gas temperatures can be obtained from diatomic spectra are formulated.

Bruggeman, P. J.; Sadeghi, N.; Schram, D. C.; Linss, V.

2014-04-01

287

A gas-puff-driven theta pinch for plasma-surface interaction studies  

NASA Astrophysics Data System (ADS)

DEVeX is a theta pinch device used to investigate fusion-related material interaction such as vapor shielding and ICRF antenna interactions with plasma-pulses in a laboratory setting. The simulator is required to produce high heat-flux plasma enough to induce temperature gradient high enough to study extreme conditions happened in a plasma fusion reactor. In order to achieve it, DEVeX is reconfigured to be combined with gas puff system as gas puffing may reduce heat flux loss resulting from collisions with neutral. A gas puff system as well as a conical gas nozzle is manufactured and several diagnostics including hot wire anemometer and fast ionization gauge are carried out to quantitatively estimate the supersonic flow of gas. Energy deposited on the target for gas puffing and static-filled conditions is measured with thermocouples and its application to TELS, an innovative concept utilizing a thermoelectric-driven liquid metal flow for plasma facing component, is discussed.

Jung, Soonwook; Kesler, Leigh; Yun, Hyun-Ho; Curreli, Davide; Andruczyk, Daniel; Ruzic, David

2012-10-01

288

Nonthermal plasma processor utilizing additive-gas injection and/or gas extraction  

DOEpatents

A device for processing gases includes a cylindrical housing in which an electrically grounded, metal injection/extraction gas supply tube is disposed. A dielectric tube surrounds the injection/extraction gas supply tube to establish a gas modification passage therearound. Additionally, a metal high voltage electrode circumscribes the dielectric tube. The high voltage electrode is energizable to create nonthermal electrical microdischarges between the high voltage electrode and the injection/extraction gas supply tube across the dielectric tube within the gas modification passage. An injection/extraction gas and a process gas flow through the nonthermal electrical microdischarges within the gas modification passage and a modified process gas results. Using the device contaminants that are entrained in the process gas can be destroyed to yield a cleaner, modified process gas.

Rosocha, Louis A.

2006-06-20

289

Measurement of the plasma and neutral gas flow velocities in a low-pressure hollow-cathode plasma jet sputtering system  

NASA Astrophysics Data System (ADS)

We present results from two mutually independent measurements of plasma and neutral gas flow velocities in a plasma jet deposition system. Operation of a hollow-cathode discharge within the plasma jet nozzle in the pulse regime enables the simple use of a classical Langmuir probe for the plasma flow velocity measurement. In this method, we assume that the plasma is generated solely inside the nozzle during the power impulse and we measure the time of flight of the ions along a known distance between the nozzle end and the probe. The plasma velocity at the plasma jet axis is then determined by differentiation of the dependence of the distance covered by ions on time. As the second method the well-known Pitot tube is used for measurement of the neutral gas velocity. By comparison of both methods we have experimentally proved that the neutral gas flow velocity is almost unaffected by the presence of the plasma, i.e. it does not substantially depend on whether the discharge is switched on or off. The results of both methods correspond well; detected differences are qualitatively explained. It is documented that the plasma jet can be operated both in a subsonic and in a supersonic regime. We present the dependences of the plasma and neutral gas flow velocity on the distance from the cathode, on the pressure in the reactor chamber, and on the flow rate of the working gas.

Kluso?, J.; Kudrna, P.; Tichý, M.

2013-02-01

290

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

291

Sterile neutrinos in the early universe  

SciTech Connect

We discuss the role played by right-handed sterile neutrinos in the early universe. We show how well known {sup 4}He constraint on the number of relativistic degrees of freedom at early times limits the equilibration of the right handed neutrino sea with the background plasma. We discuss how this allows interesting constraints to be placed on neutrino properties. In particular, a new limit on the Dirac mass of the neutrino is presented. 12 refs.

Malaney, R.A. (Lawrence Livermore National Lab., CA (USA)); Fuller, G.M. (California Univ., San Diego, La Jolla, CA (USA). Dept. of Physics)

1990-11-14

292

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

293

Mechanisms of gas precipitation in plasma-exposed tungsten  

SciTech Connect

Precipitation in subsurface bubbles is a key process that governs how hydrogen isotopes migrate through and become trapped within plasma-exposed tungsten. We describe a continuum-scale model of hydrogen diffusion in plasma-exposed materials that includes the effects of precipitation. The model can account for bubble expansion via dislocation loop punching, using an accurate equation of state to determine the internal pressure. This information is used to predict amount of hydrogen trapped by bubbles, as well as the conditions where the bubbles become saturated. In an effort to validate the underlying assumptions, we compare our results with published positron annihilation and thermal desorption spectroscopy data, as well as our own measurements using the tritium plasma experiment (TPE).

R. D. Kolasinski; D. F. Cowgill; D. C. Donovan; M. Shimada

2012-05-01

294

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

295

Synthesis gas production from CO 2 and H 2O with nonthermal plasma  

Microsoft Academic Search

Synthesis gas was produced from CO2 and H2O with nonthermal plasma. A ferroelectric packed-bed reactor worked much better than a silent discharge plasma reactor. CO2 and H2O competitively reacted to give CO and H2, respectively. Arbitrary molar ratios of H2 to CO were obtained by controlling that of H2O to CO2. Energy conversion efficiency decreased with water content, and its

Shigeru Futamura; Hajime Kabashima

2004-01-01

296

A platform for highly charged ions: surface-foil-gas-plasma interaction at the IMP  

NASA Astrophysics Data System (ADS)

A platform for the study of highly charged ions (HCIs), the surface-foil-gas-plasma interaction at IMP Lanzhou, is introduced. Some potentially useful results obtain over the last few years on x-ray emission, ion sputtering, secondary electron emission and the nano-etching effects during HCIs' impact on surfaces, as well as the guiding effect of nano-capillaries, are reviewed. Our ongoing work on the HCI interaction with plasma is also reported.

Cheng, R.; Zhou, X. M.; Sun, Y. B.; Lei, Y.; Wang, X.; Xu, G.

2011-06-01

297

Experimental study of a small gas-puff Z-pinch plasma device  

Microsoft Academic Search

An experiment was carried out on a small gas-puff Z-pinch plasma device with capacitor bank of 16 ?F and charging voltage 22 kV. Discharge current was measured by Rogowski coil. A compact Thomson ion energy analyzer was installed in the discharge chamber for determining the energy spectra of ion beam emitted from the Z-pinch plasma. The energy spectra of argon

Chengmu Luo; Chengrong Li; Xinxin Wang; Zhifeng Xie; X. M. Guo; Min Han

1999-01-01

298

Diagnostics for a small gas-puff Z-pinch plasma device  

Microsoft Academic Search

Experiments were carried out on a small gas-puff Z-pinch plasma device with a capacitor bank of 16 ?F and a charging voltage of 22 kV. A compact Thomson ion energy analyzer was installed on the device for determining the energy spectra of ion beam emitted from the Z-pinch plasma. The energy spectra of Argon ion beams with single, double, and

Chengmu Luo; Xinxin Wang; Min Han; Chengrong Li

2000-01-01

299

Gas-puff z-pinch plasmas driven by inductive energy storage pulsed power generator  

Microsoft Academic Search

ASO-II, an inductive energy storage pulsed power generator developed at Kumamoto University, is used as a power source for gas-puff z-pinch plasmas. The plasma characteristics are compared with those generated by a fast capacitive bank that supplies the same energy. Also, solid and mesh cathode electrodes are compared with respect to the pinch behavior. Using ASO-II in the case of

K. Murayama; T. Shinkai; S. Katsuki; H. Akiyama

1997-01-01

300

EUV radiation characteristics of Ar gas-puff Z-pinch plasma with axial magnetic field  

Microsoft Academic Search

The axial magnetic field was applied to the Ar gas-puff Z-pinch plasma for the control of soft X-ray and EUV emission. The reduction of soft X-ray and increase of EUV emission were again confirmed. EUV spectroscopic measurement was made on the Z-pinch plasma, and Ar IX and Ar X lines were observed. By applying axial magnetic field of 950 G,

Keiichi Takasugi; Fuminari Kobayashi

2004-01-01

301

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

SciTech Connect

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

302

Diffusion-controlled regime of surface-wave-produced plasmas in helium gas  

Microsoft Academic Search

The study presents a numerical fluid-plasma model of diffusion-controlled surface-wave-sustained discharges in helium gas. The self-consistent behaviour of the discharge based on the interrelation between plasma density and Theta, the power absorbed on average by one electron, is described. The nonlinear process of step ionization in the charged particle balance equation is the main factor, which ensures the self-consistency. However,

J. Berndt; K. Makasheva; H. Schlüter; A. Shivarova

2002-01-01

303

Vacuum arc plasma jet interaction with neutral ambient gas  

Microsoft Academic Search

Vacuum arc plasma jet (VAPJ) propagation in a neutral nitrogen atmosphere has been calculated numerically on the basis of a hydrodynamic description. It was assumed that the VAPJ was emitted isotropically from a point source located z0 = 20 mm in front of the entrance of a straight duct 100 mm in diameter in which an axial magnetic field of

E. Gidalevich; S. Goldsmith; R. L. Boxman

2000-01-01

304

Gas Tungsten Arc Welding and Plasma Arc Cutting. Teacher Edition.  

ERIC Educational Resources Information Center

This welding curriculum guide treats two topics in detail: the care of tungsten electrodes and the entire concept of contamination control and the hafnium electrode and its importance in dual-air cutting systems that use compressed shop air for plasma arc cutting activities. The guide contains three units of instruction that cover the following…

Fortney, Clarence; And Others

305

The effects of sterilization, processing and aging on the structure and morphology of medical-grade ultrahigh molecular weight polyethylene for use in total joint replacements  

NASA Astrophysics Data System (ADS)

A pilot study was performed which examined the effects of gamma radiation sterilization after five years aging in air on the structure of ultrahigh molecular weight polyethylene (UHMWPE) for total joint replacements. A sterilized tibial component and a nonsterile block of polymer which had come from the same compression molded batch of material were characterized by differential scanning calorimetry (DSC), density gradient column (DGC), small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FTIR). Increases in crystallinity and density were observed for the sterilized component after five years aging in air. A thickening of the lamellae as well as an increase in their tortuosity was seen in the sterilized material. Oxygen uptake occurred in the irradiated specimens. Results indicated that chain scission was the dominant response to gamma irradiation sterilization and aging in air for five years. Material from four different processing conditions was sterilized by: gamma irradiation, electron beam irradiation, ethylene oxide gas, plasma, or not sterilized as a control. Groups were divided into aging environments: air, hyaluronic acid and hydrogen peroxide. Characterization by DSC, DGC, TEM, SAXS and FTIR was performed periodically over a period of one and a half years. Processing conditions had the least effect on the structure and morphology of UHMWPE. Initial increases in oxygen uptake were higher for those materials with higher nascent crystallinities. Trends observed for all materials as a function of sterilization, aging environment and time were similar. Sterilization method and subsequent aging time were the most important factor in examining the structure of UHMWPE. Ethylene oxide gas and plasma did not appear to alter the polymer. Both forms of irradiation resulted in the most changes with time augmenting some effects. Results indicated chain scission dominated in response to radiation and caused a degradation of the polymer. Aging environment had a significant effect on the polymer with hydrogen peroxide leading to the most dramatic changes including embrittlement of the material. A mechanism for the oxidation of the polymer is proposed in which oxygen attacks the amorphous regions leading to strains and the eventual creation of microcracks.

Goldman, Marni

306

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

307

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

308

Formation and Dynamics of Vortex Structures in Pure and Gas-Discharge Nonneutral Collisionless Electron Plasmas  

E-print Network

The comparative analysis of the results of experimental investigations of the processes of formation, interaction and dynamics of vortex structures in pure electron and gas-discharge electron nonneutral plasmas taking place for the period of time much less than the electron-neutral collision time has been given. The general processes of formation and behavior of vortex structures in these two plasmas were considered. The phenomena, taking place only in one of these plasmas were also considered. It is shown that the existing difference in behavior of vortex structures is caused by different initial states of nonneutral electron plasmas. The role of vortex structures in the processes taking place in nonneutral electron plasma is discussed.

Kervalishvili, N A

2013-01-01

309

MINOS Sterile Neutrino Search  

SciTech Connect

The Main Injector Neutrino Oscillation Search (MINOS) is a long-baseline accelerator neutrino experiment designed to measure properties of neutrino oscillation. Using a high intensity muon neutrino beam, produced by the Neutrinos at Main Injector (NuMI) complex at Fermilab, MINOS makes two measurements of neutrino interactions. The first measurement is made using the Near Detector situated at Fermilab and the second is made using the Far Detector located in the Soudan Underground laboratory in northern Minnesota. The primary goal of MINOS is to verify, and measure the properties of, neutrino oscillation between the two detectors using the {nu}{sub {mu}} {yields} V{sub {tau}} transition. A complementary measurement can be made to search for the existence of sterile neutrinos; an oft theorized, but experimentally unvalidated particle. The following thesis will show the results of a sterile neutrino search using MINOS RunI and RunII data totaling {approx}2.5 x 10{sup 20} protons on target. Due to the theoretical nature of sterile neutrinos, complete formalism that covers transition probabilities for the three known active states with the addition of a sterile state is also presented.

Koskinen, David Jason; /University Coll. London

2009-09-01

310

Sterility of packaged implant components.  

PubMed

Several implant components in their original glass vial and peel-back packages were subjected to sterility testing to determine whether the contents remained sterile after the expiration date marked on the package had passed. The results from a university microbiology laboratory showed that the contents remained sterile for 6 to 11 years after the expiration dates. PMID:15973959

Worthington, Philip

2005-01-01

311

Observations of thermal creep gas flow and dust-density waves in dusty plasma experiments  

NASA Astrophysics Data System (ADS)

In laboratory experiments, I study strongly-coupled dusty plasma levitated in a glow-discharge plasma. Dusty plasma is an arrangement of small dust particles in a plasma background of electrons, ions, and neutral gas. The dust particles are negatively charged because they collect electrons and ions from the background plasma. Depending on the experimental setup, the plasma's electric field can help to balance the dust particles against gravity. The high dust charge causes dust particles to repel each other, while confinement forces prevent their escape. The dust particles cannot easily move past one another, and instead organize themselves into highly-ordered structures. The neutral gas also plays a key role in these experiments. Depending on the relative motion between gas and dust particles, the neutral gas can either impede dust motion or it can drive the dust into motion. In this thesis, I report the findings of three separate experiments. In the first experiment, I use a spherically-shaped dusty plasma (Yukawa ball) as an indicator of a flow of neutral gas, called thermal creep flow. In the second and third experiments, I study naturally occurring dust-density waves, which propagate within the volume of a dusty plasma that has many horizontal layers. In Ch. 2 of this thesis, I study thermal creep flow (TCF), which is a flow of gas driven by a temperature gradient along a solid boundary. Stripes on a glass box are heated by laser beam absorption, leading to both TCF and a thermophoretic force. A stirring motion of the dust particle suspension is observed. By eliminating all other explanations for this motion, I conclude that TCF at the boundary couples by drag to the bulk gas, causing the bulk gas to flow, thereby stirring the suspension of dust particles. This result provides an experimental verification that TCF in the slip-flow regime causes steady-state gas flow in a confined volume. In Ch. 3, I observe the growth of a naturally occurring dust-density wave (DDW) using high-speed imaging. This low-frequency wave (˜ 25 Hz) grows in amplitude as it propagates downward through a dusty plasma. I measure the wave's linear growth rate using a phase-sensitive analysis method. For the conditions studied here, the growth rate increases as gas pressure decreases. At a critical gas pressure that I observe, a balance between an ion-flow instability and dissipation by neutral gas drag determines a threshold for wave propagation. A linear dispersion relation is derived, taking into account effects of strong coupling, to compare to the experiment. In Ch. 4, I observe the development of nonlinearity in the naturally occurring dust-density wave by measuring harmonics of the fundamental. Using high-speed imaging, I measure amplitudes, wave numbers and growth rates for the fundamental and its harmonics. The amplitudes of the harmonics exhibit a strong exponential increase with diminishing gas pressure, and they saturate at lower gas pressures. My measurements show that the wave numbers and growth rates of harmonics are near integer multiples of the fundamental.

Flanagan, Timothy Mcguire

312

Experimental study of a gas-puff Z-pinch plasma  

Microsoft Academic Search

A small gas-puff Z-pinch plasma device driven by a capacitor bank (12 ?f, 3.75 kJ) is reported. The current reaches the maximum of 200 kA in about 2.2 ?s. A supersonic (March 4) flow nozzle is used to feed argon into the discharge chamber. The gas density profile, the discharge current, the rate of current rise, the compression process of

C. R. Li; T. C. Yang; M. Han; C. M. Luo

1989-01-01

313

Comparison of Monte Carlo and fluid dynamics simulations of gas flow for plasma radiation source nozzles  

Microsoft Academic Search

The Decade radiation simulator will use a Plasma Radiation Source (PRS) to provide the soft x-ray environment for DoD Nuclear Weapons Effects Testing requirements. We have made comparisons of two very different approaches to the modeling of gas flow for nozzles used in PRS z-pinches. Time-dependent, 2-D numerical simulations were performed of the gas flow through various double shell PRS

R. Chapman; M. Scott; K. Tatum; H. Ebrahimi; R. Spinetti; M. Krishnan; N. Qi; R. Prasad; E. Waisman; A. Bixier; K. Campbell; P. Coleman

2002-01-01

314

Emerging applications of low temperature gas plasmas in the food industry.  

PubMed

The global burden of foodborne disease due to the presence of contaminating micro-organisms remains high, despite some notable examples of their successful reduction in some instances. Globally, the number of species of micro-organisms responsible for foodborne diseases has increased over the past decades and as a result of the continued centralization of the food processing industry, outbreaks now have far reaching consequences. Gas plasmas offer a broad range of microbicidal capabilities that could be exploited in the food industry and against which microbial resistance would be unlikely to occur. In addition to reducing the incidence of disease by acting on the micro-organisms responsible for food spoilage, gas plasmas could also play a role in increasing the shelf-life of perishable foods and thereby reduce food wastage with positive financial and environmental implications. Treatment need not be confined to the food itself but could include food processing equipment and also the environment in which commercial food processing occurs. Moreover, gas plasmas could also be used to bring about the degradation of undesirable chemical compounds, such as allergens, toxins, and pesticide residues, often encountered on foods and food-processing equipment. The literature on the application of gas plasmas to food treatment is beginning to reveal an appreciation that attention needs also to be paid to ensuring that the key quality attributes of foods are not significantly impaired as a result of treatment. A greater understanding of both the mechanisms by which micro-organisms and chemical compounds are inactivated, and of the plasma species responsible for this is forming. This is significant, as this knowledge can then be used to design plasma systems with tailored compositions that will achieve maximum efficacy. Better understanding of the underlying interactions will also enable the design and implementation of control strategies capable of minimizing variations in plasma treatment efficacy despite perturbations in environmental and operational conditions. PMID:25779089

Shaw, Alex; Shama, Gilbert; Iza, Felipe

2015-01-01

315

Laser plasma radiation from small solid particle in gas atmosphere  

NASA Astrophysics Data System (ADS)

The problem of small particle size detection is important for industrial and environmental applications. Previous investigations have shown the possibility of using the laser breakdown method to achieve this goal; the sensitivity of this method is a thousand times higher than that of conventional methods. However, for small particle sizes, the damage threshold of the solid target in this case is very close to the breakdown point of pure air. After breakdown, there is a small volume of dense hot plasma that emits radiation. We analyzed this radiation using an analytical model and simulation code as well as by experiment, and found that the emission intensity varied depending on the laser type and plasma parameters including initial particle size.

Andreev, Alexander A.; Ueda, Toshitsugu; Hayashi, Hisanori

2000-03-01

316

Features of plasma glow in low pressure terahertz gas discharge  

SciTech Connect

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.; Razin, S. V. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation)] [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); Litvak, A. G.; Sidorov, A. V.; Skalyga, V. A.; Zorin, V. G. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation) [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); Lobachevsky State University of Nizhny Novgorod (UNN), 23 Gagarina st., 603950 Nizhny Novgorod (Russian Federation)

2013-12-15

317

Gas temperature measurements in a microwave plasma by optical emission spectroscopy under single-wall carbon nanotube growth conditions  

Microsoft Academic Search

Plasma gas temperatures were measured via in situ optical emission spectroscopy in a microwave CH4-H2 plasma under carbon nanotube (CNT) growth conditions. Gas temperature is an important parameter in controlling and optimizing CNT growth. The temperature has a significant impact on chemical kinetic rates, species concentrations and CNT growth rates on the substrate. H2 rotational temperatures were determined from the

R. K. Garg; T. N. Anderson; R. P. Lucht; T. S. Fisher; J. P. Gore

2008-01-01

318

Gas temperature measurements in a microwave plasma by optical emission spectroscopy under single-wall carbon nanotube growth conditions  

Microsoft Academic Search

Plasma gas temperatures were measured via in situ optical emission spectroscopy in a microwave CH4–H2 plasma under carbon nanotube (CNT) growth conditions. Gas temperature is an important parameter in controlling and optimizing CNT growth. The temperature has a significant impact on chemical kinetic rates, species concentrations and CNT growth rates on the substrate. H2 rotational temperatures were determined from the

R K Garg; T N Anderson; R P Lucht; T S Fisher; J P Gore

2008-01-01

319

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

320

Modeling of gas reactions in denitrification from flue gas by discharge plasma  

Microsoft Academic Search

Modeling of plasma discharge is a necessary complement for experimental investigation not only because it helps in understanding the fundamental chemistry and physics governing the discharge but also because it is necessary for the design and analysis of the performance of plasma devices. In this paper, a kinetics model was developed to characterize the chemical reactions taking place in a

Dong Li-Min; Zhou Zhi-Qiang; Chi Xiao-Chun; Yang Jia-Yang

2004-01-01

321

Plasma gas-switching method for gas chromatography/inductively coupled plasma mass spectrometry and determination of polybrominated diphenylethers with high precision and sensitivity.  

PubMed

The drift in sensitivity due to carbon deposition on the sampling cone, skimmer cone and ion lenses has been a serious problem in gas chromatography/inductively coupled plasma mass spectrometry (GC/ICP-MS). To overcome this problem, a high-speed switching method between a mixed-gas plasma and a pure-argon plasma (named plasma gas-switching method) using an oxygen permeation tube and a switching valve was developed. This enabled both the cleaning of deposited carbon and an enhancement of the sensitivity; as a consequence, both the repeatability and the sensitivity of polybrominated diphenylether (PBDE) were improved by more than 3 and 4 times, respectively. The drifts of sensitivity over a period of 8 h were less than 5% in most cases. Concerning the analytical performance of thermally labile congeners from octa- to deca-BDE, the detection limits, dynamic ranges of the calibration graphs and unequivalent sensitivities were remarkably improved by using a metal capillary separation column coated with a very thin (0.05 micromm) film of immobilized-polydimethylsiloxane. The detection limits ranged from 0.014 pg (BDE-154) to 0.093 pg (BDE-209), which were equal or superior to the lowest values reported hitherto by GC/MS (high resolution). A remarkable loss of sensitivity for highly-brominated congeners, such as nona- and deca-BDE, was observed in an analysis of PBDE technical mixtures when the solvent was methanol. The loss of sensitivity turned out to be due to an activation of the retention gap used for on-column injection; this problem was solved by changing methanol to isooctane in the sample-preparation step before analysis. PMID:19075460

Tao, Hiroaki; Nakazato, Tetsuya; Akasaka, Mikio; Rajendran, Ramaswamy Babu; Elouali, Sofia

2008-12-01

322

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

323

Plasma generation in an organic molecular gas by an ultraviolet laser Y. S. Zhang and J. E. Scharer  

E-print Network

and the one photon ionization process. An application of a TMAE plasma as a mirror for microwave potential application is to use a rotating plasma sheet to steer a high frequency radar beamPlasma generation in an organic molecular gas by an ultraviolet laser pulse Y. S. Zhang and J. E

Scharer, John E.

324

Three-dimensional modeling of arc plasma and metal transfer in gas metal arc welding  

Microsoft Academic Search

An integrated comprehensive 3D model has been developed to study the transport phenomena in gas metal arc welding (GMAW). This includes the arc plasma, droplet generation, transfer and impingement onto the weld pool, and weld pool dynamics. The continuum formulation is used for the conservation equations of mass, momentum, and energy in the metal zone. The free surface is tracked

G. Xu; J. Hu; H. L. Tsai

2009-01-01

325

Diesel emission control system using combined process of nonthermal plasma and exhaust gas components' recirculation  

Microsoft Academic Search

A NOx aftertreatment system, using nonthermal plasma (NTP) reduction and exhaust gas components' recirculation, is investigated. A pilot-scale system is applied to a stationary diesel engine. In this system, NOx is first removed by adsorption, and subsequently, the adsorbent is regenerated by thermal desorption. NOx desorbed is reduced by using nitrogen NTP. Moreover, NOx, CO2, and water vapor recirculated into

Keiichiro Yoshida; Tomoyuki Kuroki; Masaaki Okubo

2009-01-01

326

Formation of tungsten coatings by gas tunnel type plasma spraying Akira Kobayashia,*, Shahram Sharafatb  

E-print Network

Formation of tungsten coatings by gas tunnel type plasma spraying Akira Kobayashia,*, Shahram Tungsten is a material that has the highest melting point of 3422 -C among metals. Therefore, when deposited as a coating, it can protect the substrate surface from high heat flux. In this study, tungsten (W

Ghoniem, Nasr M.

327

Gas-surface dynamics and charging effects during plasma processing of semiconductors  

Microsoft Academic Search

This thesis work attempts to elucidate the fundamentals of gas-surface interactions that occur during plasma etching. Controlled experiments using hyperthermal fluorine beams have enabled us to uncover the scattering dynamics at complex surfaces similar to those encountered in etching. By analyzing energy and angular distributions of inelastically scattered F atoms, we were able to distinguish single- and multiple-bounce scattering and

Gyeong Soon Hwang

1999-01-01

328

Removal of SO2 from gas streams using a dielectric barrier discharge and combined plasma photolysis  

E-print Network

Removal of SO2 from gas streams using a dielectric barrier discharge and combined plasma photolysis H. Balbach University of Illinois. Department of Electrical and Computer Engineering, 1406 W Green Engineering, I406 F! Green Street, Urbana, Illinois 61801 (Received 8 November 1990; accepted for publication

Kushner, Mark

329

Effect of neutral gas heating in argon radio frequency inductively coupled plasma  

NASA Astrophysics Data System (ADS)

Heating of neutral gas in inductively coupled plasma (ICP) is known to result in neutral gas depletion. In this work, this effect is considered in the simulation of the magnetic field distribution of a 13.56 MHz planar coil ICP. Measured electron temperatures and densities at argon pressures of 0.03, 0.07 and 0.2 mbar were used in the simulation whilst neutral gas temperatures were heuristically fitted. The simulated results showed reasonable agreement with the measured magnetic field profile.

Chin, O. H.; Jayapalan, K. K.; Wong, C. S.

2014-08-01

330

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

331

Residual gas entering high density hydrogen plasma: rarefaction due to rapid heating  

NASA Astrophysics Data System (ADS)

The interaction of background molecular hydrogen with magnetized (0.4 T) high density (1–5 × 1020 m?3) low temperature (?3 eV) hydrogen plasma was inferred from the Fulcher band emission in the linear plasma generator Pilot-PSI. In the plasma center, vibrational temperatures reached 1 eV. Rotational temperatures obtained from the Q(v = 1) branch were systematically ?0.1 eV lower than the Q(v = 0) branch temperatures, which were in the range of 0.4–0.8 eV, typically 60% of the translational temperature (determined from the width of the same spectral lines). The latter is attributed to preferential excitation of translational degrees of freedom in collisions with ions on the timescale of their in-plasma residence time. Doppler shifts revealed co-rotation of the molecules with the plasma at an angular velocity an order of magnitude lower, confirming that the Fulcher emission connects to background molecules. A simple model estimated a factor of 90 rarefaction of the molecular density at the center of the plasma column compared to the residual gas density. Temperature and density information was combined to conclude that ion-conversion molecular assisted recombination dominates plasma recombination at a rate of 1 × 10?15 m3 s?1. The observations illustrate the general significance of rapid molecule heating in high density hydrogen plasma for estimating molecular processes and how this affects Fulcher spectroscopy.

Den Harder, N.; Schram, D. C.; Goedheer, W. J.; De Blank, H. J.; Van de Sanden, M. C. M.; Van Rooij, G. J.

2015-04-01

332

Plasma-assisted catalysis for the destruction of CFC12 in atmospheric pressure gas streams using TiO 2  

Microsoft Academic Search

A non-thermal, atmospheric pressure plasma with a titanium dioxide catalyst were combined to destroy difluorochloromethane,\\u000a CCl2F2, (CFC-12) in gas streams of nitrogen and air using two configurations; one where the catalyst was incorporated directly into\\u000a the plasma and the other where the catalyst was downstream of the plasma. The single stage reactor, in both gas streams, gave\\u000a significant enhancement of

Anna E. Wallis; J. Christopher Whitehead; Kui Zhang

2007-01-01

333

Transcutaneous male sterilization.  

PubMed

This report reviews and summarizes the results of current animal and human research studies for each of the 3 approaches to transcutaneous sterilization: intratesticular injection of chemical agents to affect spermatogenesis; intraepididymal injection of chemical agents to affect sperm transport; and obstruction of the vas lumen by the intravasal injection of chemical (sclerosing) agents or by electrocoagulation of the vas lumen. Wiebe and Barr evaluated the effects of the direct injection of aqueous 1, 2, 3-trihydroxypropane (THP; glycerol), a normal component of living cells, into the testes of Sprague-Dawley rats. Spermatogenesis was inhibited by a direct and local action of THP on the seminiferous tubules. The only other intratesticular method that has been investigated is the use of ultrasonic energy. Although the injection of sclerosing agents directly into the epididymis is technically simpler than injection into the vas lumen, the intraepididymal approach to nonsurgical sterilization has been evaluated in only 3 studies. The advantages of intraepididymal over intravasal injections are that the cauda epididymis is easily palpated and intraluminal placement of the needle in the epididymis is not necessary. The appeal of the intraepididymal approach to transcutaneous sterilization is that it is easier to inject a chemical into the epididymis than into the vas lumen. Limitated evaluations of the intraepididymal injection of chemical agents has shown this to be an unsatisfactory approach to male sterilization. Whether improved results can be obtained with other chemical agents remains to be evaluated. Numerous chemical agents have been injected into the vasa of rats, dogs, and rabbits to evaluate their effects in producing vas occulsion. A table lists the agents that have been evaluated. Only 2 chemical agents are known to have been tested in man: 3.6% formaldehyde in 90% ethanol and 4% formaldehyde in 90% ethanol and a carbolic acid, n-butyl alpha cyanoacrylate mixture. The mode of action of all of the sclerosing agents tested is thought to be similar: they produce local necrosis and fibrosis and vasal closure through scarring. A main objective in choosing a chemical agent for use in human sterilization procedures is to select one that has minimal toxic effects and will produce a minimal amount of damage if injected onto structures other than the vas. The transcutaneous intravasal sterilization procedure developed by the Chinese and which has been widely and successfully used since 1972 is described. To further advance the electrocoagulation procedure developed by Schmidt in 1966, bipolar electrodes have been developed. Black, at the Marie Stopes Clinic in the UK, is currently investigating a transcutaneous electrocoagulation procedure. Black believes that improvement of the electrodes and some changes in the technique of performing the electrocoagulation will result in an effective procedure. PMID:12179626

Goldsmith, A; Edelman, D A; Zatuchni, G I

1985-04-01

334

A parallel hybrid numerical algorithm for simulating gas flow and gas discharge of an atmospheric-pressure plasma jet  

NASA Astrophysics Data System (ADS)

Development of a hybrid numerical algorithm which couples weakly with the gas flow model (GFM) and the plasma fluid model (PFM) for simulating an atmospheric-pressure plasma jet (APPJ) and its acceleration by two approaches is presented. The weak coupling between gas flow and discharge is introduced by transferring between the results obtained from the steady-state solution of the GFM and cycle-averaged solution of the PFM respectively. Approaches of reducing the overall runtime include parallel computing of the GFM and the PFM solvers, and employing a temporal multi-scale method (TMSM) for PFM. Parallel computing of both solvers is realized using the domain decomposition method with the message passing interface (MPI) on distributed-memory machines. The TMSM considers only chemical reactions by ignoring the transport terms when integrating temporally the continuity equations of heavy species at each time step, and then the transport terms are restored only at an interval of time marching steps. The total reduction of runtime is 47% by applying the TMSM to the APPJ example presented in this study. Application of the proposed hybrid algorithm is demonstrated by simulating a parallel-plate helium APPJ impinging onto a substrate, which the cycle-averaged properties of the 200th cycle are presented. The distribution patterns of species densities are strongly correlated by the background gas flow pattern, which shows that consideration of gas flow in APPJ simulations is critical.

Lin, K.-M.; Hu, M.-H.; Hung, C.-T.; Wu, J.-S.; Hwang, F.-N.; Chen, Y.-S.; Cheng, G.

2012-12-01

335

Study of atmospheric plasma spray process with the emphasis on gas-shrouded nozzles  

NASA Astrophysics Data System (ADS)

An atmospheric plasma spraying process is investigated in this work by using experimental approach and mathematical modelling. Emphasis was put on the gas shrouded nozzles, their design, and the protection against the mixing with the surrounding air, which they give to the plasma jet. First part of the thesis is dedicated to the analysis of enthalpy probe method, as a major diagnostic tool in this work. Systematic error in measuring the stagnation pressure, due to a big temperature difference between the plasma and the water-cooled probe, is investigated here. Parallel measurements with the enthalpy probe and an uncooled ceramic probe were performed. Also, numerical experiments were conducted, using the k-? model of turbulence. Based on the obtained results, a compensating algorithm for the above error is suggested. Major objective of the thesis was to study the plasma spraying process, and potential benefits from using the gas shrouded nozzles. Mathematical modelling was used to perform the parametric study on the flow pattern inside these nozzles. Two nozzles were used: a commercial conical nozzle, and a custom-made curvilinear nozzle. The later is aimed towards elimination of the cold air entrainment, recorded for the conical nozzle. Also, parametric study on the shrouding gas and its interaction with the plasma jet was carried out. Two modes of the shrouding gas injection were tested: through sixteen injection ports, and through a continuous slot, surrounding the plasma jet. Both nozzles and both injection modes were thoroughly tested, experimentally and numerically. The curvilinear nozzle completely eliminates the cold air entrainment and yields significantly higher plasma temperature. Also, injection through the continuous slot resulted in a much better protection of the plasma jet. Both nozzles were used to perform the spraying tests. Obtained coatings were tested on porosity, adhesion strength, and micro- structure. These tests indicated better micro-structure of the coatings sprayed by the curvilinear nozzle. Also, their porosity was significantly lower, and the adhesion strength was higher for more than 25%. The overall results suggest that the curvilinear nozzles represent a much better solution for the gas shrouded plasma spraying.

Jankovic, Miodrag M.

336

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

337

Determination of acenocoumarol in human plasma by capillary gas chromatography with mass-selective detection.  

PubMed

A method for the determination of acenocoumarol in human plasma by capillary gas chromatography-mass-selective detection is described. After addition of a structurally related analogue as the internal standard, the compounds are extracted from plasma at acidic pH into toluene, back-extracted with a basic solution and re-extracted from hydrochloric acid solution with toluene, which is then evaporated to dryness. The compounds are converted into their methyl derivatives, which are determined by gas chromatography using a mass-selective detector at m/z 324 for acenocoumarol and m/z 338 for the internal standard. The reproducibility and accuracy of the method were found to be suitable over the acenocoumarol concentrations range 2.2-74 nmol/l. The method could be considered as selective for acenocoumarol in the presence of its major metabolites in plasma. PMID:8004241

Pommier, F; Ackermann, R; Sioufi, A; Godbillon, J

1994-03-18

338

Determination of levamisole in plasma and animal tissues by gas chromatography with thermionic specific detection.  

PubMed

A rapid and sensitive method has been developed for the determination of the anthelmintic levamisole in plasma and tissues from man and animals. The procedure involves the extraction of the drug and its internal standard from the biological material at alkaline pH, back-extraction into sulphuric acid and re-extraction into the organic phase (heptane-isoamyl alcohol). Several extraction steps can be omitted, however, whenever the gas chromatographic background permits and some operations can be simplified using Clin ElutTM extraction tubes. The analyses were carried out by gas chromatography using a nitrogen-selective thermionic specific detector. The detection limit was 5 ng, contained in 1 ml of plasma or in 1 g of the various tissues, and recoveries were sufficiently high (79-86%). The method was applied to human plasma samples in a comprehensive bioavailability study of levamisole in healthy volunteers, and to plasma and tissues in a residue trial in cattle. The effect of the blood collection technique on the plasma levels was also studied and pointed to decreased plasma concentrations when Vacutainer tubes were used. PMID:7263817

Woestenborghs, R; Michielsen, L; Heykants, J

1981-06-12

339

Characterization of volatile radiolysis products in radiation-sterilized plastics by thermal desorption-gas chromatography-mass spectrometry: screening of six medical polymers  

NASA Astrophysics Data System (ADS)

Volatile radiolysis products of six medical polymers were identified by TDS-GC-MS after sterilizing doses of ca 25 kGy. All the polymers—PS, MABS, PA-6, PVC, PE, and PP—produce detectable amounts of volatiles which remain trapped in the polymer matrix for considerable times; the products and their concentrations are characteristic for each plastic. The main products of PS are acetophenone, benzaldehyde, phenol, 1-phenylethanol, and phenylacetaldehyde; their concentrations are ca one order of magnitude below the residual styrene/styrene dimer levels. Some trace products are formed with still lower yields—with the exception of benzene these are also oxidized aromatic compounds. The same volatiles are observed in MABS, which additionally gives some aliphatic compounds. PA-6 yields pentanamide as the main product, plus traces of some homologous amides. The main products of PVC and PP are fragments of additives, i.e., of stabilizers and phenol-type antioxidants, respectively. The PE produces only traces of hydrocarbons, aldehydes, ketones, and carboxylic acids, which largely disappear within weeks. The effects of irradiation on polymer pellets and injection-molded parts are comparable. The implications of our results for radiation detection and for the safety of irradiated devices and packaging materials are briefly discussed.

Buchalla, Rainer; Boess, Christian; Bögl, Klaus Werner

1999-09-01

340

Analytical treatment of the force acting on a relativistic electron beam spreading in dense gas plasma by the ohmic plasma channel  

NASA Astrophysics Data System (ADS)

A method is described for the analytical evaluation of the force acting on a relativistic electron beam spreading in dense gas plasma by the ohmic plasma channel. This is useful for the solution of the general definitions for the force of the beam plasma interactions in the case of an arbitrary displacement of the symmetry axis of the plasma channel relative to the corresponding axis of the beam. The accuracy of these procedures is tested and their efficiency illustrated with practical applications, including the computation of the tracking force exerting on a relativistic electron beam by the ohmic plasma channel.

Mamedov, B. A.

2015-04-01

341

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

342

[Permanent tubal hysteroscopic sterilization].  

PubMed

Tubal sterilization, of common practice all over the world, has had a quick spread in France since its legalization in 2001 and the income of a new hysteroscopic method. As a matter of fact, France is the second greater country for women having Essure® and the first country where Essure® method forestall surgical tubal ligation. Thus we focus on good practice and update knowledge about Essure® method. PMID:22658908

Panel, P; Jost, S; Grosdemouge, I; Friederich, L; Niro, J; Le Tohic, A

2012-01-01

343

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

344

[Determination of beta-phenyllactic acid in rat plasma by derivatization capillary gas chromatography (DCGC)].  

PubMed

The determination of beta-phenyllactic acid (PLA) in rat plasma by derivatization capillary gas chromatography is described. Quantitation was affected by 63Ni-electron capture detector after separation with a SE-54 quartz capillary chromatographic column. Calibration curves were linear within the range of 1.6-9.6 micrograms.ml-1. The limit of detection of PLA was considered to be 0.5 microgram.ml-1. PLA was extracted from plasma with ethyl acetate (rat plasma 0.1 ml). The recovery from plasma was high and the mean value was 98.11 +/- 3.81 (s)%, their within day and between day relative standard deviations were 5.13% and 5.99% respectively. PMID:7660790

Mo, G Q; Zhang, X M; Cheng, W B; Li, D; Yang, X Y

1995-01-01

345

Determination of 17 ?-Estradiol in Rabbit Plasma by Gas Chromatography with Flame Ionization Detection  

PubMed Central

This article describes gas chromatography-flame ionization detection method for determination of 17 ?-estradiol in rabbit plasma. 17 ?-estradiol and internal standard progesterone were extracted from plasma using liquid–liquid extraction method. Linearity was found between 0.25 and 20 ?g/ml (r2=0.994) for plasma samples. Intra-day and inter-day precision, expressed as the relative standard deviation were less than 5.5%, and accuracy (relative error) was less than 3.5%. The mean recovery of 17 ?-estradiol samples was 94.4%. The limits of detection and quantification of method for plasma samples were 0.10 ?g/ml and 0.15 ?g/ml, respectively. Also, clinically used other 10 drugs were investigated to check for potential interferences and the method was successfully applied to the determination of 17 ?-estradiol in New Zealand white rabbits. PMID:23439655

Yilmaz, B; Kadioglu, Y.

2012-01-01

346

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.

347

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

348

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

349

Recent nuclear pumped laser results. [gas mixtures and laser plasmas  

NASA Technical Reports Server (NTRS)

Recent direct nuclear pumped laser research has concentrated on experiments with three gas mixtures (Ne-N2, He-Ne-O2, and He-Hg). One mixture has been made to lase and gain has been achieved with the other two. All three of these mixtures are discussed with particular attention paid to He-Hg. Of interest is the 6150-angstroms ion transition in Hg(+). The upper state of this transition is formed directly by charge transfer and by Penning ionization.

Miley, G. H.; Wells, W. E.; Akerman, M. A.; Anderson, J. H.

1976-01-01

350

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

351

[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

352

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

SciTech Connect

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. [School of Energy Science and Engineering, Central South University, Changsha 410083 (China); Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States); Liao, S. M. [School of Energy Science and Engineering, Central South University, Changsha 410083 (China); Tsai, H. L. [Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States)

2010-02-15

353

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

354

Plasma-produced phase-pure cuprous oxide nanowires for methane gas sensing  

SciTech Connect

Phase-selective synthesis of copper oxide nanowires is warranted by several applications, yet it remains challenging because of the narrow windows of the suitable temperature and precursor gas composition in thermal processes. Here, we report on the room-temperature synthesis of small-diameter, large-area, uniform, and phase-pure Cu{sub 2}O nanowires by exposing copper films to a custom-designed low-pressure, thermally non-equilibrium, high-density (typically, the electron number density is in the range of 10{sup 11}–10{sup 13}?cm{sup ?3}) inductively coupled plasmas. The mechanism of the plasma-enabled phase selectivity is proposed. The gas sensors based on the synthesized Cu{sub 2}O nanowires feature fast response and recovery for the low-temperature (?140?°C) detection of methane gas in comparison with polycrystalline Cu{sub 2}O thin film-based gas sensors. Specifically, at a methane concentration of 4%, the response and the recovery times of the Cu{sub 2}O nanowire-based gas sensors are 125 and 147?s, respectively. The Cu{sub 2}O nanowire-based gas sensors have a potential for applications in the environmental monitoring, chemical industry, mining industry, and several other emerging areas.

Cheng, Qijin, E-mail: ijin.cheng@xmu.edu.cn; Zhang, Fengyan [School of Energy Research, Xiamen University, Xiamen City, Fujian Province 361005 (China); Yan, Wei [School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney, New South Wales 2052 (Australia); Plasma Nanoscience Laboratories, CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Randeniya, Lakshman [Plasma Nanoscience Laboratories, CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Ostrikov, Kostya [Plasma Nanoscience Laboratories, CSIRO Materials Science and Engineering, Lindfield, New South Wales 2070 (Australia); Plasma Nanoscience, School of Physics, The University of Sydney, Sydney, New South Wales 2006 (Australia)

2014-03-28

355

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

356

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

357

IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 34, NO. 3, JUNE 2006 895 Simulation of Electron Kinetics in Gas Discharges  

E-print Network

in Gas Discharges Vladimir I. Kolobov, Senior Member, IEEE, and Robert R. Arslanbekov Abstract--We review the state-of-the-art for the simulation of electron kinetics in gas discharges based on the numerical simulation of the electron distribution function in collisional gas discharge plasmas. We illustrate

Kaganovich, Igor

358

Dynamics of plasma expansion and shockwave formation in femtosecond laser-ablated aluminum plumes in argon gas at atmospheric pressures  

E-print Network

in argon gas at atmospheric pressures Alexander Miloshevsky, Sivanandan S. Harilal, Gennady Miloshevsky formation in fs-pulse and ns-pulse laser ablated Al plumes in an ambient gas at atmospheric pressures. VC plasma expansion into a background gas at atmospheric pressure is cru- cial for many engineering

Harilal, S. S.

359

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

360

Intense microwave pulse propagation through gas breakdown plasmas in a waveguide  

SciTech Connect

High-power microwave pulse-compression techniques are used to generate 2.856 GHz pulses which are propagated in a TE/sub 10/ mode through a gas filled section of waveguide, where the pulses interact with self-generated gas-breakdown plasmas. Pulse envelopes transmitted through the plasmas, with duration varying from 2 ns to greater than 1 ..mu..s, and peak powers of a few kW to nearly 100 MW, are measured as a function of incident pulse and gas pressure for air, nitrogen, and helium. In addition, the spatial and temporal development of the optical radiation emitted by the breakdown plasmas are measured. For transmitted pulse durations greater than or equal to 100 ns, good agreement is found with both theory and existing measurements. For transmitted pulse duration as short as 2 ns (less than 10 rf cycles), a two-dimensional model is used in which the electrons in the plasma are treated as a fluid whose interactions with the microwave pulse are governed by a self-consistent set of fluid equations and Maxwell's equations for the electromagnetic field. The predictions of this model for air are compared with the experimental results over a pressure range of 0.8 torr to 300 torr. Good agreement is obtained above about 1 torr pressure, demonstrating that microwave pulse propagation above the breakdown threshold can be accurately modeled on this time scale. 63 refs., 44 figs., 2 tabs.

Byrne, D.P.

1986-10-08

361

Two-stage plasma gun based on a gas discharge with a self-heating hollow emitter  

SciTech Connect

The paper presents the results of tests of a new compact two-stage bulk gas plasma gun. The plasma gun is based on a nonself-sustained gas discharge with an electron emitter based on a discharge with a self-heating hollow cathode. The operating characteristics of the plasma gun are investigated. The discharge system makes it possible to produce uniform and stable gas plasma in the dc mode with a plasma density up to 3x10{sup 9} cm{sup -3} at an operating gas pressure in the vacuum chamber of less than 2x10{sup -2} Pa. The device features high power efficiency, design simplicity, and compactness.

Vizir, A. V.; Tyunkov, A. V.; Shandrikov, M. V.; Oks, E. M. [Institute of High Current Electronics, Russian Academy of Sciences, Tomsk 634055 (Russian Federation)

2010-02-15

362

Transition from gas to plasma kinetic equilibria in gravitating axisymmetric structures  

SciTech Connect

The problem of the transition from gas to plasma in gravitating axisymmetric structures is addressed under the assumption of having initial and final states realized by kinetic Maxwellian-like equilibria. In astrophysics, the theory applies to accretion-disc scenarios around compact objects. A formulation based on non-relativistic kinetic theory for collisionless systems is adopted. Equilibrium solutions for the kinetic distribution functions describing the initial neutral matter and the resulting plasma state are constructed in terms of single-particle invariants and expressed by generalized Maxwellian distributions. The final plasma configuration is related to the initial gas distribution by the introduction of appropriate functional constraints. Qualitative aspects of the solution are investigated and physical properties of the system are pointed out. In particular, the admitted functional dependences of the fluid fields carried by the corresponding equilibrium distributions are determined. Then, the plasma is proved to violate the condition of quasi-neutrality, implying a net charge separation between ions and electrons. This result is shown to be independent of the precise realization of the plasma distribution function, while a physical mechanism able to support a non-neutral equilibrium state is proposed.

Cremaschini, Claudio; Stuchlík, Zden?k [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic)] [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic)

2014-04-15

363

Physical and biological mechanisms of plasma interaction with living tissue  

Microsoft Academic Search

Non-thermal plasmas are already well-known for their sterilization ability; however the mechanisms of this sterilization are under debate. Short and long living active species and radicals produced by plasma, ultraviolet (UV) radiation, local thermal effects, and bombardment by charges particles are all listed as potential candidates for sterilization of various surfaces. In this work, biochemical and physical mechanisms of plasma

G. Fridman; D. Dobrynin; G. Friedman; A. Fridman

2008-01-01

364

Applications of Laser Plasma EUV Source Based on a Gas Puff Target  

SciTech Connect

Laser plasma with temperature of the order of tens eV can be an efficient source of extreme ultraviolet (EUV). The radiation can be focused using different kind of optics giving sufficient fluence for some applications. In this work we present results of investigations concerning different applications of a laser plasma EUV source based on a double stream gas puff target. The experiments were connected with micromachining of organic polymers by direct photo-etching luminescence excited with EUV and using the source for EUV microscopy.

Bartnik, A.; Fiedorowicz, H.; Jarocki, R.; Kostecki, J.; Rakowski, R.; Szczurek, A.; Szczurek, M. [Institute of Optoelectronics, Military University of Technology, Kaliskiego 2, 00-908 Warsaw (Poland)

2008-03-19

365

Gas laser for efficient sustaining a continuous optical discharge plasma in scientific and technological applications  

SciTech Connect

A stable high-power laser is developed for the study and technical applications of a continuous optical discharge (COD). The laser based on the technology of a combined discharge in a scheme with a fast axial gas flow emits 2.2 kW at 10.6 {mu}m per meter of the active medium in continuous and repetitively pulsed regimes with the electrooptical efficiency 20%. The sustaining of the COD plasma in argon and air is demonstrated at the atmospheric pressure. The emission properties of the COD plasma are studied and its possible applications are discussed. (lasers)

Zimakov, V P; Kuznetsov, V A; Kedrov, A Yu; Solov'ev, N G; Shemyakin, A N; Yakimov, M Yu [A.Yu. Ishlinskii Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow (Russian Federation)

2009-09-30

366

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

367

Parametric Study of Localized Plasma Mechanisms in ICP reactors using HBr/Cl2 Gas Mixtures  

NASA Astrophysics Data System (ADS)

HBr/Cl2 gas mixture is often used for etching poly-Si. As the dimensions of the transistors are reduced, profile control, high poly-Si etch rate, high selectivity over the gate oxide, low ion-induced damage become critical. We have investigated detailed plasma mechanism for HBr/Cl2 and applied to two dimensional plasma transport code in order to investigate localized behavior of HBr/Cl2 plasma chemistry. The initial mechanism for HBr/Cl2 is investigated using well mixed model. For a HBr/Cl2 plasma, the nominal conditions are 1000 Watts of input power, 5 mTorr of pressure, and a gas mixture of HBr/Cl2 = 20/80%. The major ions are Cl+, Cl2+ and Br+. The well mixed computational results show that approximately HBr/Cl2 = 55/45% will produce the equal amount of Br+ and Cl+ ions. The generation of Br+ and Cl+ are almost exclusively from the ionization of ground states and excited states of Br and Cl, where Br and Cl is mostly formed from the electron dissociation of HBr and Cl2, respectively. Cl2+ is mostly from the ionization of ground state Cl2. For a two dimensional transport code, we have used latest version of INDUCT, (2) which solves a set of time dependent fluid equations for electron and ions self-consistently with Poisson's equation for the electric potential. The dominant plasma reactions are identified for several locations in the reactor chamber including the areas below the coils, close to the side wall, center of the reactor, and above the wafer. (1) E. Meeks and J. W. Shon, IEEE Trans. on Plasma Sci., 23, 539, 1995. (2) P. Vitello, J. N. Bardsley, G. Dipeso, and G. J. Parker, IEEE Trans. on Plasma Sci., 24, 123, 1996.

Shon, J. W.; Vitello, P.

1996-10-01

368

Sterilization in the United States  

PubMed Central

Unintended pregnancies are expensive for patients and for society in terms of medical costs, the cost of caring for more children, and the cost to personal and professional goals. Sterilization is the most common contraceptive method utilized by couples in the United States. Given technological advances over the past few decades, male and female surgical sterilization has become a safe, convenient, easy, and highly effective birth control method for the long term. This article reviews current male and female sterilization options. PMID:18701927

Bartz, Deborah; Greenberg, James A

2008-01-01

369

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

SciTech Connect

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 H{sub 2} 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 of 1 atm, T needs to be higher than about 450 deg. C in order to successfully produce washers of titanium hydride. Results on compressive strength of the loaded washers suggest that an appropriate ratio of atoms of hydrogen to titanium is less than H:Ti{approx}0.85:1.

Himura, H.; Saito, Y.; Sanpei, A.; Masamune, S.; Takeuchi, N.; Shiono, T. [Department of Electronics, Kyoto Institute of Technology, Matsugasaki, Sakyo Ward, Kyoto 606-8585 (Japan); Department of Chemistry and Materials Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo Ward, Kyoto 606-8585 (Japan)

2006-07-15

370

Gas temperature in transient CO2 plasma measured by Raman scattering  

NASA Astrophysics Data System (ADS)

Rotational Raman scattering on the vibrational ground state of CO2 was performed to determine the gas temperature in narrow-gap dielectric barrier discharges (DBDs). The Raman spectrometer was equipped with a straightforward spectral filtering to mask ca. 30 cm?1 (0.85 nm) centered around the excitation wavelength of 532 nm. Linearisation of the observed transitions (J = 18–42) was applied to retrieve gas temperatures in discharge gaps of 1 mm. The DBD was operated in pure CO2 at atmospheric pressure and non-negligible gas heating of about 160 K was observed at 33 W injected power. Based on a simplified energy balance the gas temperature measurements were extrapolated to a broad range of injected plasma power values (0–60 W).

Brehmer, F.; Welzel, S.; Klarenaar, B. L. M.; van der Meiden, H. J.; van de Sanden, M. C. M.; Engeln, R.

2015-04-01

371

Numerical study on the Z pinch dynamics of gas jet type discharge produced plasma (DPP) source  

NASA Astrophysics Data System (ADS)

Z pinch DPP source is often used as an Extreme Ultra-Violet (EUV) source. It is convenient to produce high temperature and high density plasma. There are several analytical models to describe the dynamics of the plasma. The snowplow model is a simple and widely used model to analyze the motion of the plasma shell and predict the pinch time; however, it is incapable of analyzing the plasma behavior after the maximum pinch and providing detailed information of concerned plasma parameters, such as electron density and electron temperature. In this study, we present the simulation results of the Z pinch DPP dynamics obtained by a 2D MHD code. This code solves the problem based on the assumption of single fluid, two temperature approximations in the cylindrical geometry. The numerical scheme for this MHD code is Total-Variation-Diminishing scheme in Lax Friedrich formulation (TVD-LF). The evolution of electron density, electron temperature, current density, magnetic flux and some other important parameters in Z pinch dynamics are investigated with this code. The simulation results show that the maximum pinch electron density is on the order of 10^19 cm-3, with a pinch plasma radius of about 0.1 mm. In order to optimize the radiation output, the influences of initial gas distribution and the current waveform on the Z pinch dynamics are also investigated. They affect the electron density at pinch stagnation obviously; while in term of electron temperature, the effect is slight.

Huang, Bin; Xie, Bin; Tomizuka, Taku; Watanabe, Masato; Xiao, Feng; Hotta, Eiki

2012-10-01

372

[Determination of endogenous agmatine in rat plasma by isotope dilution-gas chromatography-mass spectrometry].  

PubMed

A method for the determination of endogenous agmatine in rat plasma was developed by isotope dilution-gas chromatography-negative chemical ionization mass spectrometry (GC-NCI/MS). The plasma samples were analyzed after protein precipitation, evaporation, derivatization by hexafluoroacetone (HFAA), and clean-up on a Florisil SPE column. The GC-MS analysis utilized stable isotope d8-agmatine as internal standard. The samples after treatme were tested by negative chemical ionization with selected ion monitoring (SIM) which was set at m/z 492 (molecular ion of agmatine) and m/z 500 (molecular ion of internal standard). The limit of detection (LOD) of agmatine standard solution was 0.005 7 ng/mL. The calibration curve of the agmatine spiked in rat plasma showed a good linear relationship at the range of 1.14-57.0 ng/mL (r = 0.997). The recoveries of agmatine spiked in rat plasma ranged from 92.3% to 109.8%. Inter-day and intra-day precisions were less than 15%. The average concentration level of agmatine in rat plasma was (22 +/- 9) ng/mL, and there was no significant difference between male and female SD rats (p > 0.05). The method is high sensitive and specific, and can be used for the determination of endogenous agmatine in plasma. It provides a strong support for the subsequent research of agmatine. PMID:25255573

Qiu, Zhongli; Lin, Ying; Xiong, Zhili; Xie, Jianwei

2014-07-01

373

plasmas  

NASA Astrophysics Data System (ADS)

As-deposited HfO2 films were modified by CHF3, C4F8, and mixed C4F8/O2 plasmas in a dual-frequency capacitively coupled plasma chamber driven by radio frequency generators of 60 MHz as the high frequency (HF) source and 2 MHz as the low frequency source (60/2 MHz). The influences of various surface plasma treatments under CHF3, C4F8, and C4F8/O2 were investigated in order to understand the chemical and structural changes in thin-film systems, as well as their influence on the electrical properties. Fluorine atoms were incorporated into the HfO2 films by either CHF3 or C4F8 plasma treatment; meanwhile, the C/F films were formed on the surface of the HfO2 films. The formation of C/F layers decreased the k value of the gate stacks because of its low dielectric constant. However, the addition of O2 gas in the discharge gases suppressed the formation of C/F layers. After thermal annealing, tetragonal HfO2 phase was investigated in both samples treated with CHF3 and C4F8 plasmas. However, the samples treated with O-rich plasmas showed monoclinic phase, which indicated that the addition of O plasmas could influence the Hf/O ratio of the HfO2 films. The mechanism of the t-HfO2 formation was attributed to oxygen insufficiency generated by the incorporation of F atoms. The capacitors treated with C4F8/O2 plasmas displayed the highest k value, which ascribed that the C/F layers were suppressed and the tetragonal phase of HfO2 was formed. Good electrical properties, especially on the hysteresis voltage and frequency dispersion, were obtained because the bulk traps were passivated by the incorporation of F atoms. However, the H-related traps were generated during the CHF3 plasma treatments, which caused the performance degradation. All the treated samples showed lower leakage current density than the as-deposited HfO2 films at negative bias due to the reduced trap-assisted tunneling by the incorporation of F to block the electrons transferring from metal electrode to the trap level.

Zhang, H. Y.; Jin, C. G.; Yang, Y.; Ye, C.; Zhuge, L. J.; Wu, X. M.

2014-12-01

374

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

375

Laparoscopic sterilization kit.  

PubMed

A suitcase size laparoscopic sterilization kit produced by Medical Technology Internationale, Inc. was tested on 50 patients at the Johns Hopkins Hospital and field tested in San Jose, Costa Rica. The pneumoperitoneum device has reduced overall size with 2 "pop-off" valves, one to prevent more than one l carbon dioxide from entering the abdomen and one to protect against sudden expansion of any carbon dioxide within the peritoneal cavity. Electrocoagulation capacity has been adequate for fulguration of the uterine tube. The miniaturization of the equipment should provide greater mobility in delivering family planning services. PMID:4269087

Wheeless, C R

1973-08-01

376

Development and characterization of very dense submillimetric gas jets for laser-plasma interaction.  

PubMed

We report on the characterization of recently developed submillimetric He gas jets with peak density higher than 10(21) atoms/cm(3) from cylindrical and slightly conical nozzles of throat diameter of less than 400 ?m. Helium gas at pressure 300-400 bar has been developed for this purpose to compensate the nozzle throat diameter reduction that affects the output mass flow rate. The fast-switching electro-valve enables to operate the jet safely for multi-stage vacuum pump assembly. Such gaseous thin targets are particularly suitable for laser-plasma interaction studies in the unexplored near-critical regime. PMID:22462922

Sylla, F; Veltcheva, M; Kahaly, S; Flacco, A; Malka, V

2012-03-01

377

Development and characterization of very dense submillimetric gas jets for laser-plasma interaction  

NASA Astrophysics Data System (ADS)

We report on the characterization of recently developed submillimetric He gas jets with peak density higher than 1021 atoms/cm3 from cylindrical and slightly conical nozzles of throat diameter of less than 400 ?m. Helium gas at pressure 300-400 bar has been developed for this purpose to compensate the nozzle throat diameter reduction that affects the output mass flow rate. The fast-switching electro-valve enables to operate the jet safely for multi-stage vacuum pump assembly. Such gaseous thin targets are particularly suitable for laser-plasma interaction studies in the unexplored near-critical regime.

Sylla, F.; Veltcheva, M.; Kahaly, S.; Flacco, A.; Malka, V.

2012-03-01

378

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

NASA Astrophysics Data System (ADS)

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 understanding the dynamics of non-thermal plasmas in flame environments. In this concept, cold (in a generalized sense) barriers of gas play the role of the dielectrics, with some major differences in behaviour with respect to solid barriers. We present an analytical evaluation of the discharge appearance modes, new experimental results using helium-nitrogen layers that confirm the possibility of avoiding breakdown in the cold layers and a numerical evaluation that helps interpret the development of streamers once they reach a non-ionizing region.

Guerra-Garcia, C.; Martinez-Sanchez, M.

2013-08-01

379

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

SciTech Connect

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 {mu}F, 50 to 200 nH, and 1 to 3 kV, respectively.

Poehlmann, Flavio R.; Cappelli, Mark A. [Department of Mechanical Engineering, Stanford University, Stanford, California 94305 (United States); Rieker, Gregory B. [Fluence, LLC, 37444 Sycamore Street, Unit 16, Newark, California 94560 (United States)

2010-12-15

380

Comparison of plasma and gas driven permeation of deuterium through titanium diboride  

NASA Astrophysics Data System (ADS)

Plasma driven and gas driven permeation of deuterium through Kovar and TiB 2 coated Kovar membranes have been measured. The transport of deuterium through the coated surface was found to be fundamentally different for the two drivers. For gas driven permeation, essentially no deuterium diffuses through the coating, but a significant quantity reaches the Kovar substrate through microcracks in the coating. The permeation rate is thus determined by the extent to which the coating masks the substrate. For plasma driven permeation, on the other hand, the ions are implanted into the coating and diffuse through to the substrate. The data were used to determine the diffusivity of deuterium in TiB 2 at 500°C. The implications for tritium permeation through coated components in fusion reactors are discussed.

Kerst, R. A.; Swansiger, W. A.

1985-09-01

381

Group separation and gas chromatography--mass spectrometry of conjugated steroids in plasma.  

PubMed

A method is described for analysis of metabolic profiles of conjugated steroids in plasma. Steroids are extracted by Amberlite XAD-2 or Sep-Pak C18 cartridges at 60 64 C in the presence of triethylamine sulphate and separated into unconjugated neutral and phenolic compounds, glucuronide, monosulphate and disulphate conjugate groups by chromatography on the lipophilic strong anion exchanger triethylaminohydroxypropyl Sephadex LH-20 (TEAP-LH-20). The conjugate moiety is hydrolyzed by brief enzymatic or solvolytic procedures and released steroids are separated into a neutral and a phenolic fraction on TEAP-LH-20. The O-methyloxime and trimethylsilyl ether derivatives of the steroids are analyzed by glass capillary column gas liquid chromatography and gas chromatography mass spectrometry. Examples of the application of the method to analysis of conjugated steroids in plasma from pregnant women are given. PMID:6827836

Axelson, M; Sahlberg, B L

1983-03-01

382

Effect of Zr on microstructure of metallic glass coatings prepared by gas tunnel type plasma spraying.  

PubMed

Metallic glass is one of the most attractive advanced materials, and many researchers have conducted various developmental research works. Metallic glass is expected to be used as a functional material because of its excellent physical and chemical functions such as high strength and high corrosion resistance. However, the application for small size parts has been carried out only in some industrial fields. In order to widen the industrial application fields, a composite material is preferred for the cost performance. In the coating processes of metallic glass with the conventional deposition techniques, there is a difficulty to form thick coatings due to their low deposition rate. Thermal spraying method is one of the potential candidates to produce metallic glass composites. Metallic glass coatings can be applied to the longer parts and therefore the application field can be widened. The gas tunnel plasma spraying is one of the most important technologies for high quality ceramic coating and synthesizing functional materials. As the gas tunnel type plasma jet is superior to the properties of other conventional type plasma jets, this plasma has great possibilities for various applications in thermal processing. In this study, the gas tunnel type plasma spraying was used to form the metallic glass coatings on the stainless-steel substrate. The microstructure and surface morphology of the metallic glass coatings were examined using Fe-based metallic glass powder and Zr-based metallic glass powder as coating material. For the mechanical properties the Vickers hardness was measured on the cross section of both the coatings and the difference between the powders was compared. PMID:22905546

Kobayashi, A; Kuroda, T; Kimura, H; Inoue, A

2012-06-01

383

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

384

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

385

Spatial characterization of extreme ultraviolet plasmas generated by laser excitation of xenon gas targets  

Microsoft Academic Search

At Laser-Laboratorium Göttingen laser-plasma sources were tested, which are going to be used for characterization of optical components and sensoric devices in the wavelength region from 11 to 13 nm. In all cases extreme ultraviolet (EUV) radiation is generated by focusing a Q-switched Nd:YAG laser into a pulsed gas puff target. By the use of xenon or oxygen as target

Sebastian Kranzusch; Christian Peth; Klaus Mann

2003-01-01

386

Investigations on plasma-polymer-coated SAW and STW resonators for chemical gas-sensing applications  

Microsoft Academic Search

Results from gas probing with various analyte vapors on high-Q low-loss surface transverse wave (STW) and surface acoustic wave (SAW) resonators coated with thin plasma-polymer films of hexamethyldisiloxane (HMDSO), styrene, and allyl alcohol at different polymerization conditions are presented in this paper. At the same acoustic wavelength of 7.22 ?m and identical film thicknesses, HMDSO-coated STW devices feature substantially higher

Ivan D. Avramov; Shigeru Kurosawa; Michael Rapp; Piotr Krawczak; Ekaterina I. Radeva

2001-01-01

387

Epitaxial silicon films deposited at high rates by gas-jet electron beam plasma CVD  

Microsoft Academic Search

We discuss a new method for low temperature epitaxial growth of silicon films by gas-jet electron beam plasma chemical vapor deposition in SiH4–Ar mixture. The growth rate up to 0.8 ?m\\/min becomes possible at the substrate temperature below 650 °C, without using ultra-high vacuum chamber. Epitaxial Si films were deposited with the thickness up to 2–10 ?m. The structure of

R. G. Sharafutdinov; V. M. Karsten; S. Ya. Khmel; A. G. Cherkov; A. K. Gutakovskii; L. D. Pokrovsky; O. I. Semenova

2003-01-01

388

VUV ablation of polymers by emission from gas-puff Z-pinch plasmas  

Microsoft Academic Search

We have made experiments of the polymer ablation utilizing the gas-puff Z-pinch plasmas which provide a highly bright emission extending over a broad wavelength range from visible lights to X-rays. When the emission was irradiated through a mask onto a polytetrafluoroethylene (PTFE) film, the irradiated area was ablated and a pattern of the mask was copied on the surface of

H. Deno; S. Sugiyama; Y. Kakudate; M. Yoshida; S. Fujiwara

1996-01-01

389

Gas-Puff Z-Pinch Plasmas Driven by Inductive Energy Storage Pulsed Power Generator  

Microsoft Academic Search

An inductive energy storage pulsed power generator is used as a power source of gas-puff z-pinch plasmas to investigate the effect of the steepened current rise on the intensity of soft X-rays and the spatial reproducibility of the hot spots. Furthermore, two kinds of electrodes, which are solid and mesh type, are used to investigate the influence of the incident

Koichi Murayama; Toshinori Shinkai; Sunao Katsuki; Hidenori Akiyama

1998-01-01

390

Soft X-ray spectroscopic study of a gas-puff Z-pinch argon plasma  

Microsoft Academic Search

X-ray radiation characteristics of argon plasma produced by a gas-puff Z-pinch device were investigated using an X-ray crystal spectrometer, an X-ray diode, and an extreme ultraviolet (XUV) spectrometer. Using a germanium crystal we have observed spectral emission from Ar XVII produced by hot spots at the pinched stage. With the help of a 2-m grazing incidence XUV spectrometer, the spectrum

Seong Ho Kim; Dong-Eon Kim; Tong Nyong Lee

1998-01-01

391

Evaluation of plasma enzyme activities using gas chromatography–mass spectrometry based steroid signatures  

Microsoft Academic Search

The simultaneous quantification of 65 plasma steroids, including 22 androgens, 15 estrogens, 15 corticoids and 13 progestins, was developed using gas chromatography-mass spectrometry (GC–MS). The extraction efficiency of the catechol estrogens was improved by the addition of l-ascorbic acid in several steps. All steroids, as their trimethylsilyl derivatives, were well separated with good peak shapes within a 50min run. The

Young Wan Ha; Ju-Yeon Moon; Hyun-Jin Jung; Bong Chul Chung; Man Ho Choi

2009-01-01

392

On the charge of dust particles in a low-pressure gas discharge plasma  

Microsoft Academic Search

Self-consistent molecular-dynamics calculations of the charge of micron-size particles in a low-pressure gas-discharge plasma\\u000a are performed. It is shown that charge exchange of ions on neutrals starts to affect the charge of dust particles at pressures\\u000a corresponding to ion mean free paths much greater than the Debye radius. The computational results show that the potential\\u000a of a particle depends nonmonotonically

A. V. Zobnin; A. P. Nefedov; V. A. Sinel’shchikov; V. E. Fortov

2000-01-01

393

Ion-plasma protective coatings for gas-turbine engine blades  

Microsoft Academic Search

Evaporated, diffusion, and evaporation—diffusion protective and hardening multicomponent ionplasma coatings for turbine and\\u000a compressor blades and other gas-turbine engine parts are considered. The processes of ion surface treatment (ion etching and\\u000a ion saturation of a surface in the metallic plasma of a vacuum arc) and commercial equipment for the deposition of coatings\\u000a and ion surface treatment are analyzed. The specific

E. N. Kablov; S. A. Muboyadzhyan; S. A. Budinovskii; A. N. Lutsenko

2007-01-01

394

Quantitation by gas chromatography of the 1- and 4-hydroxy metabolites of midazolam in human plasma.  

PubMed

The imidazobenzodiazepine midazolam (MDZ), along with its 1-hydroxy and 4-hydroxy metabolites (1-OH-MDZ, 4-OH-MDZ) can be simultaneously quantitated by electron capture gas-liquid chromatography. After addition of diazepam as internal standard, alkalinized plasma samples are extracted into benzene-isoamyl alcohol. The organic extract is separated, evaporated to dryness, reconstituted, and chromatographed using 3% SP-2250 as the liquid phase. The identity of 4-OH-MDZ, not previously detected in human plasma in unconjugated form, was verified by negative-ion chemical ionization mass spectroscopy. After single oral doses of MDZ administered to humans, concentrations of MDZ and 1-OH-MDZ (alternatively named 1-hydroxymethyl midazolam) were similar, and both compounds were eliminated from plasma in parallel. Concentrations of 4-OH-MDZ were considerably lower, but this metabolite was also eliminated in parallel with the parent compound. PMID:6483962

Arendt, R M; Greenblatt, D J; Garland, W A

1984-01-01

395

Enantioselective gas chromatographic assay with electron-capture detection for dl-ritalinic acid in plasma.  

PubMed

Enantioselective gas chromatographic assays for the quantitation of methylphenidate and its major metabolite ritalinic acid in plasma are described. The procedures involved the extraction of methylphenidate enantiomers from alkanised plasma. The plasma was then washed to ensure complete removal of methylphenidate before saturation with sodium carbonate to promote the extraction of ritalinic acid enantiomers with ethyl acetate-isopropanol (60:40) solvent mixture. Subsequently, ritalinic acid enantiomers were converted back into methylphenidate enantiomers by Fisher-Speier esterification. N-Heptafluorobutyryl-L-prolyl chloride, a chiral acylating reagent, was used to convert the enantiomers of methylphenidate into their corresponding diastereomeric amide derivatives, which were separated cleanly on an achiral capillary column (OV-225) and quantitated with electron-capture detection. The assays were sensitive, reliable and reproducible. PMID:2079507

Srinivas, N R; Hubbard, J W; Midha, K K

1990-09-14

396

Measurements of large scale-length plasmas produced from gas-filled targets  

SciTech Connect

Apart from their intrinsic interest, plasma physics processes are important because they affect the coupling of the laser energy into laser-irradiated targets. Recently, new gas-filled targets have been developed to create large mm-size plasmas for the study of stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS). We present x-ray images and x-ray spectra to characterize these targets, which show that the plasmas are homogeneous, have electron densities of {approximately}10{sup 21} cm{sup {minus}3}, and attain electron temperatures of {approximately}3 keV. We also present SBS measurements to demonstrate how systematic studies of physical phenomena can be performed using these targets.

Back, C.A.; Berger, R.L.; Estabrook, K. [and others

1995-06-30

397

Surface alloying of thin-walled metallic tube fragments using pulsed gas plasma flows  

NASA Astrophysics Data System (ADS)

A technique is developed and conditions are determined for the surface liquid-phase alloying with aluminum and chromium of thin-walled tubes made of 12% Cr type steels with the use of high-temperature pulsed gas plasma flows. The surface morphology of the samples subjected to alloying is shown to depend on the type and thickness of a deposited film and the plasma treatment conditions. The optimum plasma treatment conditions are determined; as a result, alloying elements are rather uniformly distributed in a 10-?mthick near-surface layer at a preliminarily deposited film thickness of ˜0.5 ?m. In this case, the average aluminum content in the surface layer changes in the range 6-18 wt % and the chromium content increases from ˜12 to ˜25-40 wt %.

Yakushin, V. L.; Hein, A. T.; Dzhumaev, P. S.; Kalin, B. A.; Leont'eva-Smirnova, M. V.; Pol'skii, V. I.

2014-07-01

398

Determination of clemastine in human plasma by gas chromatography with nitrogen-phosphorus detection.  

PubMed

A method for the quantitative determination of clemastine in human plasma has been developed and validated. The assay uses gas chromatography with nitrogen-phosphorus detection and a HP-1 capillary column (25 mx0.22 mm, film thickness 0.33 mm) coated with dimethylpolysiloxane. Clemastine (with orphenadrine as internal standard) was isolated from human plasma using liquid-liquid extraction. A linear relationship was observed between 0.1 and 12.8 ng/ml using the peak area ratio of clemastine to orphenadrine with a correlation coefficient greater than 0.99 (the detection limit for clemastine was 0.06 ng/ml). The intra- and inter-day coefficients of variation were less than 11%. The developed method was used for the analysis of plasma samples from healthy volunteers (n = 19) to examine the pharmacokinetics of the antihistamine clemastine after single and multiple oral doses of clemastine fumarate. PMID:10985579

Davydova, N N; Yasuda, S U; Woosley, R L; Wainer, I W

2000-07-01

399

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

400

[Rapid assay of plasma acetate by gas chromatography: evaluation and comparison with two other methods].  

PubMed

Human plasma acetate is derived from colonic fermentation of fiber and endogenous metabolism of dextrose and fatty acids. Acetate may have regulatory functions in hepatic carbohydrate metabolism. Intake of dietary fiber is associated with several beneficial effects on carbohydrates and lipids metabolisms. To study theses effects a valid and automated method for routine analysis of acetate in plasma is necessary. After oral administration of lactulose to healthy human volunteers, the concentration of plasma acetate was measured by head space gas chromatography (HS-GC), vacuum distillation gas chromatography (VD-GC) and enzymatic spectrometric method (ES). The method HS-GC was linear to 0.5 mmol.l-1 (n = 5, r = 0.998), the detection limit is 0.005 mmol.l-1. Within-day variation (CV) was 3.60% and day-to-day variation was 4.5% (0.1 mmol.l-1). The coefficients of correlation between CG-ET/CG-DsV and CG-ET/E-M are 0.903 (p = 0.0001) and 0.54 (p = 0.006) respectively, the mean square errors are respectively 0.118 and 0.138 mmol.l-1. The variation curves of plasma acetate measured by GC versus time show peak concentration of 0.323 to 0.380 mmol.l-1 at 120 min. PMID:8572379

Boussairi, A; Alamowitch, C; Hoebler, C; Champ, M; Bornet, F; Guyon, F

1995-01-01

401

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

2003-05-19

402

Influence of Gas Heating and Vibrational Kinetics on the Ionization Dynamics of Preformed Air Plasma Channels  

NASA Astrophysics Data System (ADS)

An extensive self-consistent air-plasma model based upon the Boltzmann equation for the electron energy distribution function, coupled with a heavy particle kinetics was developed to study electric discharges in a preexisting air plasma column [1]. Incorporated in the model are the steady-state balance equations for various nitrogen and oxygen species in ground and excited states, as well as atomic and molecular ions. The influence of the gas temperature is accounted for by reduction of the neutral density, collisional processes such as recombination, dissociation, V-V and V-T reactions [2], and by reactions involving electronically excited states of O2. The model was applied to study the influence of the gas temperature and vibrational kinetics on the breakdown processes in a preformed air plasma channel. Numerical calculations predict that electrical breakdown occurs at relatively low electric field. The calculated self-consistent breakdown electric field is ˜10 kV/cm for gas temperature of 300 K, while at temperature of 600 K it drops to ˜5.7 kV/cm, in excellent agreement with the experimentally determined breakdown electric field [1]. * NRC-NRL Postdoc [1] Tz.B. Petrova, H.D. Ladouceur, and A.P. Baronavski, 58th Gaseous Electronics Conference, 2005; San Jose, California, FM.00062 [2] J. Loureiro and C.M. Ferreira, J. Phys. D: Appl. Phys 19 (1986) 17-35

Ladouceur, Harold; Baronavski, Andrew; Petrova, Tzvetelina

2006-03-01

403

Electrolytic silver ion cell sterilizes water supply  

NASA Technical Reports Server (NTRS)

Electrolytic water sterilizer controls microbial contamination in manned spacecraft. Individual sterilizer cells are self-contained and require no external power or control. The sterilizer generates silver ions which do not impart an unpleasant taste to water.

Albright, C. F.; Gillerman, J. B.

1968-01-01

404

Optimizing sterilization logistics in hospitals.  

PubMed

This paper deals with the optimization of the flow of sterile instruments in hospitals which takes place between the sterilization department and the operating theatre. This topic is especially of interest in view of the current attempts of hospitals to cut cost by outsourcing sterilization tasks. Oftentimes, outsourcing implies placing the sterilization unit at a larger distance, hence introducing a longer logistic loop, which may result in lower instrument availability, and higher cost. This paper discusses the optimization problems that have to be solved when redesigning processes so as to improve material availability and reduce cost. We consider changing the logistic management principles, use of visibility information, and optimizing the composition of the nets of sterile materials. PMID:18390165

van de Klundert, Joris; Muls, Philippe; Schadd, Maarten

2008-03-01

405

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

NASA Astrophysics Data System (ADS)

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.; Ostrikov, K.

2013-02-01

406

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

407

Numerical and experimental study of behavior of gas-puff z-pinch plasma produced by inductive pulsed power generator  

Microsoft Academic Search

Magnetohydrodynamic (MHD) instabilities, such as kink and sausage instabilities, appeared on the gas-puff z-pinch plasma during the pinching process prevent spatial stability of hot spots, which are high energy density plasma regions produced by those instabilities on the z-pinch plasma column locally. Spatial stabilization of hot spots in the axial direction is very important to have practical applications. In this

K. Imasaka; Y. Kawauchi; K. Kawazoe; J. Suehiro; M. Hara

1998-01-01

408

Freezing and Melting of 3D Complex Plasma Structures under Microgravity Conditions Driven by Neutral Gas Pressure Manipulation  

SciTech Connect

Freezing and melting of large three-dimensional complex plasmas under microgravity conditions is investigated. The neutral gas pressure is used as a control parameter to trigger the phase changes: Complex plasma freezes (melts) by decreasing (increasing) the pressure. The evolution of complex plasma structural properties upon pressure variation is studied. Theoretical estimates allow us to identify the main factors responsible for the observed behavior.

Khrapak, S. A.; Klumov, B. A. [Max-Planck-Institut fuer extraterrestrische Physik, D-85741 Garching (Germany); Joint Institute for High Temperatures, 125412 Moscow (Russian Federation); Huber, P.; Thomas, H. M.; Ivlev, A. V.; Morfill, G. E. [Max-Planck-Institut fuer extraterrestrische Physik, D-85741 Garching (Germany); Molotkov, V. I.; Lipaev, A. M.; Naumkin, V. N.; Petrov, O. F.; Fortov, V. E. [Joint Institute for High Temperatures, 125412 Moscow (Russian Federation); Malentschenko, Yu.; Volkov, S. [Yuri Gagarin Cosmonaut Training Centre, 141160 Star City (Russian Federation)

2011-05-20

409

Production of vanadium nitride nanopowders from gas-phase VOCl 3 by making use of microwave plasma torch  

Microsoft Academic Search

Vanadium nitride (VN) nanopowders were directly prepared via decomposition of gas-phase vanadium oxytrichloride (VOCl3) in N2\\/Ar\\/H2 microwave plasma generated at the atmospheric pressure. The dark greenish black powders were deposited on the inner wall of the quartz tube in the microwave plasma torch. The synthesized samples were taken from two regions of the plasma reactor and analyzed by scanning electron

Yong Cheol Hong; Dong Hun Shin; Han Sup Uhm

2007-01-01

410

Comparison of European and US biological indicators for ethylene oxide sterilization  

Microsoft Academic Search

Summary Biological indicators (BIs) are used to monitor ethylene oxide (EO) gas sterilization processes for medical devices. Several European and United States BIs for EO sterilization were evaluated for resistance according to both United States Pharmacopeia (USP) XXI and United Kingdom's (UK) tests for D-values. US BIs areB. subtilis var. niger spores on paper strips or disc carriers while European

Christopher A. Demitrius; Anthony P. Duran; Virginia C. Chamberlain; Victoria M. Hitchins

1993-01-01

411

Conditional sterility in plants  

SciTech Connect

The present disclosure provides methods, recombinant DNA molecules, recombinant host cells containing the DNA molecules, and transgenic plant cells, plant tissue and plants which contain and express at least one antisense or interference RNA specific for a thiamine biosynthetic coding sequence or a thiamine binding protein or a thiamine-degrading protein, wherein the RNA or thiamine binding protein is expressed under the regulatory control of a transcription regulatory sequence which directs expression in male and/or female reproductive tissue. These transgenic plants are conditionally sterile; i.e., they are fertile only in the presence of exogenous thiamine. Such plants are especially appropriate for use in the seed industry or in the environment, for example, for use in revegetation of contaminated soils or phytoremediation, especially when those transgenic plants also contain and express one or more chimeric genes which confer resistance to contaminants.

Meagher, Richard B. (Athens, GA); McKinney, Elizabeth (Athens, GA); Kim, Tehryung (Taejeon, KR)

2010-02-23

412

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

413

Pain Associated With Hysteroscopic Sterilization  

PubMed Central

Background and Objectives: The safety and efficacy of female hysteroscopic sterilization using the Essure system has been well documented. Given the marked differences in the execution of hysteroscopic and laparoscopic sterilization, the objective of this study was to assess the experience of pain postprocedure between the 2. Secondary end-points included postoperative pain medication, time to return to normal activities, postprocedure bleeding, and patient satisfaction. Methods: Twenty cases each of laparoscopic sterilization (LS) and hysteroscopic sterilization (HS) were performed. Patients were surveyed regarding their experience of pain immediately postoperatively, 1 week, and 4 weeks post-procedure. Results: The average pain score immediately postprocedure was significantly lower among HS patients than among LS patients (t=?8.17, P<.0001). One-week post-procedure, none of the patients in the HS group reported any pain, while the average pain score among the LS patients was 2.65 (t =?9.67, P<.0001). Four weeks post-procedure, women in the HS group continued to report no pain, 35% of the LS group continued to report some pain (t=?3.04, P=.004). Conclusions: Hysteroscopic sterilization offers a minimally invasive, less painful, equally efficacious modality for sterilization than laparoscopic sterilization and should be available to all women seeking permanent birth control. PMID:17651558

Levy, Jenna; Childers, Meredith E.

2007-01-01

414

Investigation into the determination of trimethylarsine in natural gas and its partitioning into gas and condensate phases using (cryotrapping)\\/gas chromatography coupled to inductively coupled plasma mass spectrometry and liquid\\/solid sorption techniques  

Microsoft Academic Search

Speciation of trialkylated arsenic compunds in natural gas, pressurized and stable condensate samples from the same gas well was performed using (Cryotrapping) Gas Chromatography-Inductively Coupled Plasma Mass Spectrometry. The major species in all phases investigated was found to be trimethylarsine with a highest concentration of 17.8 ng\\/L (As) in the gas phase and 33.2 ?g\\/L (As) in the stable condensate phase. The

E. M. Krupp; C. Johnson; C. Rechsteiner; M. Moir; D. Leong; J. Feldmann

2007-01-01

415

Electron Impact Excitation of Metastable Rare-Gas Atoms with Applications to Plasma Diagnostics  

NASA Astrophysics Data System (ADS)

Electron-impact excitation of metastable rare-gas atoms is important for both understanding fundamental collision processes as well as for applications to gaseous discharges and plasmas. The electronic structure of the rare-gases provides a vast array of excited levels and excitation processes to study. In this work, over 38 individual cross sections for excitation out of the metastable levels in three rare-gases (Ar, Kr, and Xe) are measured via the optical method. For these experiments, a hollow cathode discharge provides a robust source of metastable atoms, which are excited by a well characterized mono-energetic electron beam (2-10 eV). The resulting electron impact excitation cross sections demonstrate a wide range of magnitudes and a variety of excitation function shapes, which are interpreted in relation to the angular momentum coupling of the initial and final energy levels. From this systematic study of the rare-gases, a few general patterns have emerged, which are valuable for estimating cross sections for which no experimental data is available. Electron excitation of metastable atoms plays an important role in low-temperature plasmas. In particular, our cross section results indicate that certain excited levels are populated more readily by excitation from metastable levels than by excitation from the ground state. Thus the optical emissions from such excited levels provide a sensitive test of the low energy region of the electron energy distribution function (eedf) within a plasma. To explore this aspect, optical emission spectra generated by Ne plasmas were experimentally measured in an inductively coupled plasma source (ICP) under a variety of experimental conditions and also calculated using a simple optical emission model. This emission model combines our experimentally measured excitation cross sections with experimentally measured number densities of excited species within the ICP, and yields an estimate of the eedf in the plasma, which is then compared to the eedf measured by an electrical probe.

Jung, Ryan O.

416

MINOS Search for Sterile Neutrinos  

E-print Network

Using a NuMI beam exposure of 7.1 /times 10^20 protons-on-target, the MINOS long-baseline experiment has performed a search for active to sterile neutrino mixing over a distance of 735 km. Details of the analysis are provided, along with results from comparisons with standard three neutrino oscillations and fits to a 3+1 model including oscillations into one sterile neutrino. An outlook on the future sterile neutrino related contributions from MINOS and the proposed MINOS+ project is also presented.

Alexandre Sousa; on behalf of the MINOS Collaboration

2011-10-16

417

Fast valve and nozzle for gas-puff operation of dense plasma focus  

SciTech Connect

A simple and reliable valve and nozzle system for a very fast injection of gas has been designed and constructed for its use in gas-puff mode of dense plasma focus experiments. It delivers a very quick rise time: 55 {mu}s. The pressure measured in our setup at a distance of 15 mm from the nozzle output is about 0.285 mbar, with a plenum pressure of 3 bars (absolute). The time between the valve aperture and pressure front arrival is 360 {mu}s. This result comes up as an average of about a hundred measurements. The energy input is 95 J (270 V on a 3000 {mu}F capacitor bank). The typical dimensions of the valve are 52 mm in diameter and 80 mm in length. The entire volume of the valve is, then, very small. The relative low pressure and voltage operation are significant advantages of this development. The performance of the valve satisfactorily fulfills the objectives of gas-puff plasma focus operation.

Milanese, Maria M.; Pouzo, Jorge O.; Cortazar, Osvaldo D.; Moroso, Roberto L. [Dense Plasma Group (GPDM), Instituto de Fisica Arroyo Seco, Universidad Nacional del Centro de la Provincia de Buenos Aires, Pinto 399, Tandil, Buenos Aires 7000 (Argentina) and CONICET, Avenida Rivadavia 1917, 1033 Buenos Aires (Argentina)

2006-03-15

418

IOP PUBLISHING PLASMA SOURCES SCIENCE AND TECHNOLOGY Plasma Sources Sci. Technol. 20 (2011) 035018 (8pp) doi:10.1088/0963-0252/20/3/035018  

E-print Network

applications of APPs is sterilization and disinfection [13]. The causes of bacteria killing by plasmas, in the case of bacteria, the plasma's sterilization capability. In this paper, we discuss results from is the plasma sterilization of air by killing floating bacteria. Topologically, bacteria floating in air being

Kushner, Mark

419

Plasma structures observed in gas breakdown using a 1.5 MW, 110 GHz pulsed gyrotron  

SciTech Connect

Regular two-dimensional plasma filamentary arrays have been observed in gas breakdown experiments using a pulsed 1.5 MW, 110 GHz gyrotron. The gyrotron Gaussian output beam is focused to an intensity of up to 4 MW/cm{sup 2}. The plasma filaments develop in an array with a spacing of about one quarter wavelength, elongated in the electric field direction. The array was imaged using photodiodes, a slow camera, which captures the entire breakdown event, and a fast camera with a 6 ns window. These diagnostics demonstrate the sequential development of the array propagating back toward the source. Gases studied included air, nitrogen, SF{sub 6}, and helium at various pressures. A discrete plasma array structure is observed at high pressure, while a diffuse plasma is observed at lower pressure. The propagation speed of the ionization front for air and nitrogen at atmospheric pressure for 3 MW/cm{sup 2} was found to be of the order of 10 km/s.

Hidaka, Yoshiteru; Choi, E. M.; Mastovsky, I.; Shapiro, M. A.; Sirigiri, J. R.; Temkin, R. J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, 167 Albany St., Cambridge, Massachusetts 02139 (United States); Edmiston, G. F.; Neuber, A. A. [Center for Pulsed Power and Power Electronics, Department of Electrical and Computer Engineering and Physics, Texas Tech University, MS 43102, Lubbock, Texas 79409 (United States); Oda, Y. [Naka Fusion Research Institute, Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki 311-0196 (Japan)

2009-05-15

420

Ion-plasma protective coatings for gas-turbine engine blades  

NASA Astrophysics Data System (ADS)

Evaporated, diffusion, and evaporation—diffusion protective and hardening multicomponent ionplasma coatings for turbine and compressor blades and other gas-turbine engine parts are considered. The processes of ion surface treatment (ion etching and ion saturation of a surface in the metallic plasma of a vacuum arc) and commercial equipment for the deposition of coatings and ion surface treatment are analyzed. The specific features of the ion-plasma coatings deposited from the metallic plasma of a vacuum arc are described, and the effect of the ion energy on the phase composition of the coatings and the processes occurring in the surface layer of an article to be treated are discussed. Some properties of ion-plasma coatings designed for various purposes are presented. The ion surface saturation of articles made from structural materials is shown to change the structural and phase states of their surfaces and, correspondingly, the related properties of these materials (i.e., their heat resistance, corrosion resistance, fatigue strength, and so on).

Kablov, E. N.; Muboyadzhyan, S. A.; Budinovskii, S. A.; Lutsenko, A. N.

2007-10-01

421

Simulation of gas dynamics and electromagnetic processes in high-current arc plasmas  

NASA Astrophysics Data System (ADS)

A strategy is developed to numerically study thermal plasma arc columns under high-current conditions. Necessary assumptions are made to focus the investigation on the interactions between gas flow, energy transport and the electromagnetic field. In order to study the macroscopic behavior of a thermal plasma under the conditions of local thermodynamic equilibrium, coupled Navier-Stokes and Maxwell's equations are derived. While the air plasma studied is assumed to be a multi-species ideal gas, the thermodynamic properties (specific heat and enthalpy) and transport properties (electrical conductivity, thermal conductivity, viscosity, and total volumetric radiation emission coefficient) are obtained using molecular theory. A commercially available, finite-volume based computational fluid dynamics code FLUENT is adapted through the use of user-defined subroutines to include the electromagnetic field and its coupling with plasma flow and heat transfer. One of Maxwell's equations-the current continuity equation-is solved in conjunction with the Navier-Stokes equations, while the magnetic field is obtained using the Biot-Savart equation. The non-linearity of the physical properties as functions of temperature and pressure are treated in the programs to ensure solution convergence. The coupling between the fluid field and electromagnetic field is modeled through source terms-an ohmic heating term in the energy equation and a Lorentz force in the momentum equation. In order to validate the code, a two-dimensional, axi- symmetric, steady-state, vertical arc column at low current (<100 A) is modeled without considering the influence of the magnetic force (Lorentz force). The effects of current level, cathode diameter and natural convection are studied. At high current levels (>100 A), the self-induced magnetic field can no longer be ignored. Therefore, a three-dimensional arc column at high current is modeled and again compared with the literature. The comparison between the results from the current study and those from the literature were satisfactory, providing validation of the code. To study the effects of both internal and external effects on a high current arc, a parametric analysis is carried out on a wall-stabilized three-dimensional arc column to investigate the influences of geometric configuration, ambient pressure, gravitational field and various boundary conditions. When the arc column is exposed to a transverse external magnetic field, the arc is bent toward the direction of the magnetic force. The corresponding plasma flow pattern is also altered. Transient analysis is performed in an open-ended arc chamber where a three-dimensional air arc column is under the influence of a transverse external magnetic field. It is found that the arc starts to bend under the magnetic force while the arc voltage increases as a result. Eventually, arc interruption is predicted when the arc voltage undergoes a rapid increase. The effects of gas ablation from sublimation materials on a high current arc column are studied by modeling the mixing of the sublimated gas (hydrogen) and air plasma. The gassing velocity is a function of heat transfer to the material, and therefore is a function of time and position. It is found that gassing in the arc chamber increases the arc voltage rapidly. The current numerical tool developed is shown to be a useful tool in applications involving thermal plasma, such as current interruption technology in switchgear applications and thermal plasma technology. Further development of the model would enable additional real arcing phenomena to be studied.

Schlitz, Lei Zhang

1998-10-01

422

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

2005-12-13

423

Pregnancy after failed tubal sterilization.  

PubMed

Various research studies have documented post-sterilization ectopic pregnancy rates ranging from 5% to 90%. To investigate this complication further, the pregnancy outcomes of the 12 women with failed tubal sterilizations who received care during 1989-91 at the Beaumont Army Medical Center in El Paso, Texas, and of 137 such patients at other Texas military hospitals during 1984-88 were reviewed. Ectopic pregnancies occurred in 8 (67%) women in the former group and 49 (36%) in the latter. The incidence of ectopic pregnancy was similar for minilaparotomy, cesarean section-associated sterilization, and laparoscopy, indicating that there is no significant advantage associated with any one procedure. A post-sterilization pregnancy may be due to tubal recanalization or to a proximal fistula. Recommended is the practice of electrocoagulating both cornual regions to cause scarring of the myometrium and closing of any fistula. PMID:8866391

Napolitano, P G; Vu, K; Rosa, C

1996-08-01

424

Plasma-sprayed zirconia gas path seal technology: A state-of-the-art review  

NASA Technical Reports Server (NTRS)

The benefits derived from application of ceramic materials to high pressure turbine gas path seal components are described and the developmental backgrounds of various approaches are reviewed. The most fully developed approaches are those employing plasma sprayed zirconium oxide as the ceramic material. Prevention of cracking and spalling of the zirconium oxide under cyclic thermal shock conditions imposed by the engine operating cycle is the most immediate problem to be solved before implementation is undertaken. Three promising approaches to improving cyclic thermal shock resistance are described and comparative rig performance of each are reviewed. Advanced concepts showing potential for performance improvements are described.

Bill, R. C.

1979-01-01

425

Determination of fluoxetine and norfluoxetine in plasma by gas chromatography with electron-capture detection  

SciTech Connect

This gas-chromatographic method for assay of fluoxetine and norfluoxetine in human plasma involves extraction of the drugs and use of a /sup 63/Ni electron-capture detector. The linear range of detection is 25 to 800 micrograms/L for each drug. Overall precision (CV) in the concentration range of 10 to 100 micrograms/L for both drugs was approximately 10%. Accuracy (relative error) in the same concentration range was approximately +10%. None of the commonly prescribed antidepressants or tranquilizers that we tested interfere with the assay.

Nash, J.F.; Bopp, R.J.; Carmichael, R.H.; Farid, K.Z.; Lemberger, L.

1982-10-01

426

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

427

Voluntary sterilization in North Tyneside.  

PubMed

Since 1975, sterilization operations, on both men and women have been performed with increasing frequency within the National Health Service in the North Tyneside Area in northeast England. A prospective study was undertaken to discover some of the reasons why healthy young men and women chose surgical sterilization rather than use the established reversible methods of family planning available to them. The study examined some of the characteristics of those requesting sterilization, attempted to understand why they did so at that particular time, and assessed the patient-perceived morbidity resulting from this elective procedure. The study population included all individuals referred for consultation following the patient's request for voluntary sterilization by vasectomy or occlusive tubal surgery, during the period of 1 year (August 1, 1980-July 31, 1981). Women sterilized in association with a pregnancy outcome were not included in the study. Data on pregnancies and sterilizations in North Tyneside demonstrate a rapid increase in requests for vasectomy after 1975. Patients requesting sterilization were admitted to the study during the initial out-patient appointment with their surgeon. Couples seeking sterilization show similar age range for men (mean 34.2) and women (33.1). The proportion of patients who were not married at the time of the operation is perhaps a reflection of doctors' increasing willingness to perform sterilizations on the unmarried, and of individuals to seek such surgery in a committed manner. The increasing tendency for requests to be received from people still in their early 20s is seen as a problem. Data indicates that married people who request the operation at an early age are also those who were married under age 21, started a family immediately and with a 25% divorce rate. At the other end of the age range, couples who ahve been sucessfully using oral contraceptives have become concerned about its safety, especially after age 35. Data indicates husbands are prepared to admit to their worries about longterm pill use and to request an alternative method of fertility control that involved them instead of their wives. Comparisons between the results of this survey and those of the Teeside survey on female sterilization between 1966-70, indicate a change in usage. The greatest difference in practice over the 12 year period was in the use of coitus interruptus, which declined sharply. It is suggested that the continued rise in the demand for sterilization may be a function of the economic recession, a relationship which needs further investigation. PMID:6725306

Carnegie-Smith, K

1984-04-01

428

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

429

The energy transfer in dust particles structure in gas discharge plasma  

NASA Astrophysics Data System (ADS)

Dust particles in gas-discharge plasma oscillate along the vertical and horizontal axes differently and have different kinetic temperature under certain conditions. The mechanism of energy transfer from discharge to dust particles motion is divided into several parts. Warming up of dust particles vertical oscillations is considered separately from the heating of horizontal oscillation, as these processes are determined by several different phenomena due to near-electrode layer anisotropy. The outflow of energy from the dust particles oscillations due to friction on the neutral gas is also taken into account. The system of dust particles is considered with involving the theory of parametric resonance and forced oscillation and phenomena of charge fluctuations. Consideration of dust particles horizontal and vertical oscillations separately reveals the possibility of two different average kinetic temperature oscillations of dust particles.

Timofeev, A.

2011-11-01

430

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.

431

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

432

Radiation sterilization of skin allograft  

NASA Astrophysics Data System (ADS)

In the treatment of burns or accidental loss of skin, cadaveric skin allografts provide an alternative to temporarily cover a wounded area. The skin bank facility is indispensable for burn care. The first human skin bank was established in Argentina in 1989; later, 3 more banks were established. A careful donor selection is carried out according to the national regulation in order to prevent transmissible diseases. As cadaveric human skin is naturally highly contaminated, a final sterilization is necessary to reach a sterility assurance level (SAL) of 10 -6. The sterilization dose for 106 batches of processed human skin was determined on the basis of the Code of Practice for the Radiation Sterilization of Tissue Allografts: Requirements for Validation and Routine Control (2004) and ISO 11137-2 (2006). They ranged from 17.6 to 33.4 kGy for bioburdens of >10-162.700 CFU/100 cm 2. The presence of Gram negative bacteria was checked for each produced batch. From the analysis of the experimental results, it was observed that the bioburden range was very wide and consequently the estimated sterilization doses too. If this is the case, the determination of a tissue-specific dose per production batch is necessary to achieve a specified requirement of SAL. Otherwise if the dose of 25 kGy is preselected, a standardized method for substantiation of this dose should be done to confirm the radiation sterilization process.

Kairiyama, E.; Horak, C.; Spinosa, M.; Pachado, J.; Schwint, O.

2009-07-01

433

Restrictions on the lifetime of sterile neutrinos from primordial nucleosynthesis  

SciTech Connect

We analyze the influence of sterile neutrinos with the masses in the MeV range on the primordial abundances of Helium-4 and Deuterium. We solve explicitly the Boltzmann equations for all particle species, taking into account neutrino flavour oscillations and demonstrate that the abundances are sensitive mostly to the sterile neutrino lifetime and only weakly to the way the active-sterile mixing is distributed between flavours. The decay of these particles also perturbs the spectra of (decoupled) neutrinos and heats photons, changing the ratio of neutrino to photon energy density, that can be interpreted as extra neutrino species at the recombination epoch. We derive upper bounds on the lifetime of sterile neutrinos based on both astrophysical and cosmological measurements of Helium-4 and Deuterium. We also demonstrate that the recent results of Izotov and Thuan [1], who find 2? higher than predicted by the standard primordial nucleosynthesis value of Helium-4 abundance, are consistent with the presence in the plasma of